Solid state lasers

Solid state lasers are disclosed herein. An example laser disclosed herein includes a monolithic body having a first end and a second end. The monolithic body includes a first reflector disposed on the first end, a second reflector disposed on the second end, and a solid state gain medium and a Q-switch disposed between the first reflector and the second reflector. The example laser also includes a pump source to cause a population inversion in the solid state gain medium to cause the monolithic body to output a laser pulse. Various applications of the solid state laser are also disclosed herein.

BACKGROUND OF THE DISCLOSURE

Generally, a laser includes a gain medium (e.g., a gas, liquid, solid, or plasma) and an energy supply. The gain medium often absorbs energy (e.g., optical radiation, electrical current, kinetic energy, thermal energy, etc.) from the energy supply. The energy may excite atoms in the gain medium until a population inversion occurs (i.e., a number of electrons in an excited state exceeds a number of electrons in a relatively lower energy state). If the population inversion occurs, the gain medium generally emits more photons than the gain medium absorbs. If an electromagnetic wave (e.g., visible light) interacts with the gain medium during the population inversion, the gain medium may amplify the electromagnetic wave, and the laser may output a laser pulse.

SUMMARY

Illustrative embodiments of the present disclosure are directed to a laser. The laser includes a monolithic body having a first end and a second end. The monolithic body includes a first reflector disposed on the first end, a second reflector disposed on the second end, and a solid state gain medium and a Q-switch disposed between the first reflector and the second reflector. The example laser also includes a pump source to cause a population inversion in the solid state gain medium that causes the monolithic body to output a laser pulse.

Illustrative embodiments of the present disclosure are also directed to a method for using a laser. The method includes disposing a laser in an environment in which a temperature is greater than one hundred degrees Celsius. The laser includes a monolithic body having a first reflector, a second reflector, and a solid state gain medium disposed between the first reflector and the second reflector. The example method further includes energizing a pump source to cause a population inversion in the solid state gain medium that causes the laser to output a laser pulse.

In a further embodiment, as described herein, an example laser includes a solid state gain medium having a first end and a second end. The example laser also includes a retroreflector adjacent the first end of the solid state gain medium and a reflector adjacent the second end of the solid state gain medium. The example laser further includes a pump source to cause a population inversion in the solid state gain medium. The solid state gain medium outputs a laser pulse through the reflector. The laser pulse has a pulse energy substantially independent of temperature when exposed to temperatures between about room temperature and about two hundred degrees Celsius.

Further illustrative embodiments of the disclosure are directed to a system for optically analyzing a sample. The system includes a pulsable laser that outputs a beam of light. A window is disposed between the laser and the sample. A micro lens array (or arrays) directs and focuses the beam of light through the window onto the sample. A detector detects light that interacts with the sample. The light that interacts with the sample is directed onto the detector by the second optical member and a third optical member.

In yet another embodiment of a system for optically analyzing a sample. The system includes a pulsable laser to output a beam of light. A window is disposed between the laser and the sample. The example system also includes a first optical member and a second optical member to collimate the beam of light outputted by the laser and direct the beam of light through the window onto the sample. The example system further includes a detector to determine a characteristic of the sample based on light interacting with the sample. The light interacting with the sample is directed onto the detector by the first optical member and the second optical member.

Illustrative embodiments of the disclosure are further directed to a downhole production logging tool for analyzing formation fluid. The tool includes a tool housing with a window. The tool also includes an optical module (e.g., a spectrometer) for analyzing the formation fluid. The optical module includes a light source that outputs light and an optical member (or members) that direct the light through the window into the formation fluid outside of the tool housing. The module also includes a detector that detects the light that interacts with the formation fluid and passes back through the window.

DETAILED DESCRIPTION

One or more aspects of the present disclosure relate to solid state lasers. An example laser disclosed herein includes a monolithic body having a first end and a second end. The monolithic body includes a first reflector disposed on the first end and a second reflector disposed on the second end. The monolithic body also includes a solid state gain medium. The solid state gain medium may be disposed between the first reflector and the second reflector. The solid state gain medium may be a material in a solid state such as, for example, a chromium doped beryllium aluminum oxide crystal (Cr3+:BeAl2O4) (“alexandrite”), a neodymium-doped yttrium aluminum garnet crystal (Nd:Y3Al5O12) (“Nd:YAG”) or any other suitable material. In some examples, the monolithic body includes a Q-switch.

The example laser also includes a pump source (e.g., a flash lamp, an arc lamp, a light emitting diode (LED), a diode laser, etc.). In some examples, the laser may include a reflective cavity substantially enclosing the monolithic body and the pump source. During operation, the pump source emits light. The light emitted from the pump source may cause a population inversion (e.g., a number of electrons in an excited state exceed a number of electrons in a relatively lower energy state) in the solid state gain medium, and the example laser may output a laser pulse through the second reflector. The example laser may advantageously output the laser pulse even when the laser is subjected to shocks (e.g., a 500 g shock) and/or vibrations (e.g., a 0.5 g^2/√Hz vibration). In some examples, a pulse energy of the laser pulse may be substantially constant when the laser is exposed to temperatures between about room temperature and about 200° C.

Illustrative embodiments of the present disclosure are directed to oil field and gas field borehole applications.FIG. 1shows an example of a downhole tool100that incorporates an embodiment of a laser as described herein. In this case, the downhole tool100is a production logging tool that is disposed within a borehole102that traverses an earth formation104. The borehole102includes a casing106and the production logging tool100is lowered into the casing106via a wireline cable and centered within the casing using a set of centralizers108. During production logging, formation fluid (e.g., formation liquid and/or formation gas) is extracted from different pay zones of the earth formation104. As the formation fluid flows to the surface, the production logging tool100can be used to monitor the characteristics of the fluid (e.g., composition). As shown inFIG. 1, the production logging tool100includes a housing110that houses a plurality of modules. At one end, the housing110includes an optical module112for performing spectroscopic measurements on a sample of the formation fluid114(e.g., Raman spectroscopy, and laser induced breakdown spectroscopy). The optical module112includes optics, at least one detector, and a light source, such as a laser, that correspond with the embodiments described herein. The laser generates light that is used to analyze the sample of formation fluid114. The light that scatters back from the sample is detected by the detector. The optics are used to communicate the light to and from the sample114. The optical module112is in optical communication with the borehole fluid via a window118. In this manner, the sample of formation fluid114adjacent the window118is analyzed by the optical module112. In this case, the window118is located at the lower end of the tool. In additional or alternative embodiments, the window is located on a sidewall of the housing110. In yet another embodiment, one window is located at the end of the housing110and a second window is located on the side of the housing110.

The production logging tool100also includes several other modules that support the optical module112. For example, the production logging tool100includes a power module120to provide power to the laser and the detector. Also, the production logging tool100may include an amplification module122to amplify an electrical signal that is output from the optical module. This electrical signal is representative of light scattered back from the sample and detected by the detector. Furthermore, the production logging tool may include a telemetry system124to provide communication between the production logging tool and surface electronics and processing systems126. In one example, the telemetry system124communicates the electrical signal from the optical module112to the surface.

In one specific application, the production logging tool100is used in a gas condensate well. The pressures, temperatures, and fluid densities encountered in gas condensate wells produce a multi-phase flow with a phase separation as the gas and liquid flow to the surface. The phase separation produces an annular flow pattern with the gas fraction flowing in the middle of the casing and the fluid fraction flowing against the sides of the casing. Centralizers108, as shown inFIG. 1, allow the gas fraction to be separately sampled, avoiding interference from the fluid fraction. The optical module112described herein can analyze various different types of gases. Exemplary gases include but are not limited to methane, ethane, propane, carbon dioxide, hydrogen sulfide, and nitrogen. In one specific embodiment, a Raman spectroscopy technique is used determine the composition of the gas fraction in the condensate well. In particular, the Raman spectroscopy technique uses a laser light signal and detects a response within the gas fraction this is linear in the density of the gas fraction.

In one embodiment of the tool, a back scattering geometry is employed, in which an axis of the excitation beam is collinear with an axis of the detected light. This back scattering geometry is advantageous for production logging because the composition of the fluid fractions may be determined without passing the fluid or gas fraction through a flow line. Illustrative embodiments of the tool are not limited to a back scattering geometry. In other embodiments, the axis of the excitation beam is offset from the axis of the detected light (e.g., spatially and/or angularly).

FIG. 2shows an example of another downhole tool200that incorporates an embodiment of a laser. In this particular embodiment, the downhole tool200is a wireline tool. The wireline tool200is suspended within a borehole202that traverses an earth formation204. The tool200is suspended within the borehole using a multiconductor cable that is spooled on a winch at the surface. In contrast to the embodiment ofFIG. 1, in which the formation fluid sample is analyzed outside the downhole tool100, in this embodiment, the wireline tool200draws a fluid sample (e.g., formation fluid or borehole fluid) into the tool and analyzes the sample within the tool. In a specific embodiment, the fluid sample is a gas. To this end, the wireline tool200includes a formation tester206having a selectively extendable probe assembly. The extendable probe assembly is configured to fluidly couple to an adjacent formation204and to draw fluid samples from the formation. A pump208is used to pass a fluid sample210through the probe assembly and into a flow line212within the tool200.

The wireline tool200also includes an optical module214for performing spectroscopic measurements on the fluid sample210within the flow line212. (e.g., Raman spectroscopy, absorption spectroscopy and laser induced breakdown spectroscopy). The optical module214includes a laser, optics and at least one detector that correspond with the embodiments described herein. The optical module214is in optical communication with the fluid sample210within the flow line212via a window216. In this manner, the fluid sample210within the flow line212is analyzed by the optical module214. Once the fluid sample210is analyzed, the sample can be expelled through a port (not shown) or the sample may be sent to one or more fluid collecting chambers218.

Various embodiments of the present disclosure are not limited to the production logging tool100and the wireline tool200shown inFIGS. 1 and 2. For example, in another embodiment, a wireline tool may include a window and an optical module for analyzing fluid samples within the borehole and outside the tool, in a similar manner to the production logging tool100ofFIG. 1. Illustrative embodiments of the present disclosure can also be used in drilling applications, such as logging-while-drilling (LWD) systems or measuring-while-drilling (MWD) systems. In one particular embodiment, the LWD system includes a sampling-while-drilling system (e.g., the sampling-while-drilling system is part of an LWD tool suite). In such a sampling-while-drilling system, a fluid sample is drawn into the system from the formation and analyzed within the tool, in a similar manner to the wireline tool200ofFIG. 2. Further details of sampling-while-drilling systems are provided in U.S. Pat. No. 7,114,562, entitled “Apparatus and Method for Acquiring Information while Drilling.”

FIG. 3is a cross-sectional view of a laser300disclosed herein. The example laser300ofFIG. 3may be employed to provide a light source for a variety of spectroscopy techniques (e.g., Raman spectroscopy, absorption spectroscopy, laser induced breakdown spectroscopy, etc.). The laser300includes a monolithic body302having a first end304and a second end306. The first end304and the second end306may be polished. In some examples, the monolithic body302is rod-shaped. The monolithic body302includes a solid state gain medium308having a first end310and a second end312. The solid state gain medium308is a material in a solid state such as, for example, a chromium doped beryllium aluminum oxide crystal (Cr3+:BeAl2O4) (“alexandrite”), a neodymium-doped yttrium aluminum garnet crystal (Nd:Y3Al5O12) (“Nd:YAG”), or any other suitable material. Some example solid state gain media include dopant elements such as Nd, Yb, Er, Ti, Tm, and/or any other suitable dopant element. As described in greater detail below, the solid state gain medium308provides a photon gain when a pump source314creates a population inversion in the solid state gain medium308.

A first reflector316and a second reflector318are disposed on the first end304and the second end306of the monolithic body302, respectively. Thus, the example solid state gain medium308is disposed between the first reflector316and the second reflector318. The first reflector316and the second reflector318provide an optical resonator (i.e., reflect light in a closed path). In the illustrated example, the first reflector316is disposed on the first end310of the solid state gain medium308. In some examples, the first and second reflectors316and318are diffusion bonded to the first and second ends304and306to form the monolithic body302, respectively. In some examples, the first and second reflectors316and318are film coatings. The example first reflector316has a reflectivity of about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) to reflect light emitted from the solid state gain medium308. The example second reflector318has a reflectivity of less than 100 percent (e.g., 80%, 90%, etc.) to enable a laser pulse to pass through the second reflector318. In some examples, the reflective surfaces of the first reflector316and the second reflector318are substantially parallel to each other. In other examples, the first reflector316and the second reflector318are curved. In some such examples, the first reflector316and the second reflector318are curved such that the first reflector316and the second reflector318are substantially confocal (i.e., radii of curvatures of the first reflector316and the second reflector318are equal to a distance between the first reflector316and the second reflector318) or substantially concentric (i.e., the radii of curvatures of the first reflector316and the second reflector318are equal to half of the distance between the first reflector316and the second reflector318).

The monolithic body302of the laser300includes a Q-switch320. In some examples, such as the example illustrated inFIG. 3, the Q-switch320is a passive Q-switch such as, for example, a saturable absorber. A coefficient of thermal expansion of the Q-switch320may be substantially equal to a coefficient of thermal expansion of the solid state gain medium308. In some examples, the Q-switch320is implemented using a Cr:YAG crystal. One end322of the Q-switch320may be non-adhesively bonded (e.g., diffusion bonded, optical contact bonded, etc.) to the second end312of the solid state gain medium308. In some such examples, the second reflector318is disposed on an opposing end324of the Q-switch320. Some embodiments of the laser do not include the Q-switch320. In such examples, the second reflector318is disposed on the second end312of the solid state gain medium308. As described in greater detail below, the Q-switch320prevents the laser from outputting a laser pulse until a population inversion in the solid state gain medium308reaches a predetermined level (e.g., a peak level).

In the illustrated example, the pump source314is a lamp pump source such as, for example, a flash lamp and/or an arc lamp. In other examples, the pump source314is a light emitting diode, a diode laser, and/or any other suitable pump source. The example pump source ofFIG. 3is adjacent the monolithic body302. In some examples, longitudinal axes of the pump source314and the solid state gain medium308are substantially parallel to each other. In the illustrated example, the pump source314includes a substantially transparent tube326(e.g., glass, quartz, etc.) filled with a gas (e.g., Xenon, krypton, etc.). The pump source314is coupled to an electrical power source (e.g., a capacitor) (not shown). During operation, an electric current is delivered to the gas via the electrical power source to cause the gas to ionize and an arc to form through the gas. In some examples, the pump source314has an arc length of about 50 mm. The above-noted dimension is merely one example and, thus, other dimensions may be used without departing from the scope of this disclosure. The arc emits a flash of light such as, for example, a 100 μs flash of light. In other examples, the arc continuously emits light. In some examples, a temperature of the arc is about 10,000° C.

In the illustrated example, a reflective cavity328substantially encloses the monolithic body302and the pump source314. The example reflective cavity328is defined by a substantially transparent (e.g., glass) cylinder330at least partially covered by a diffuse reflector332such as, for example, barium sulfate, Teflon®, and/or any other suitable diffuse reflector. In some examples, the reflective cavity328is an elliptical mirror. A first end334of the example reflective cavity328includes an aperture (not shown) adjacent the first end304of the monolithic body302. A mount336extends through the aperture to hold and/or substantially align the monolithic body302in the reflective cavity328. In some examples, the mount336holds the first end304of the monolithic body302. In some examples, another mount extends through another aperture of the reflective cavity328and holds the monolithic body302along the Q-switch320.

A second end338of the reflective cavity328is at least partially transparent and/or includes an aperture to enable the laser300to output a laser pulse through the second end338of the reflective cavity328. In the illustrated example, the reflective cavity328and the mount336are disposed in a housing340. The example mount336is coupled to the housing340. The housing340may be disposed within a downhole tool such as, for example, the downhole tool ofFIG. 1, the example tool ofFIG. 2, or any other suitable downhole tool. In some examples, the laser300is employed at or near a surface of the Earth (e.g., in a laboratory).

During operation, the pump source314supplies energy to the solid state gain medium308by emitting light. The light emitted by the pump source314is reflected by the diffuse reflector332of the reflective cavity328. The light excites atoms in the solid state gain medium308until a population inversion occurs in the solid state gain medium308(i.e., a number of electrons in an excited state exceed a number of electrons in a lower energy state). When the population inversion occurs, the solid state gain medium308emits more photons than the solid state gain medium308absorbs. As a result, the photons emitted by the solid state gain medium308are amplified by the reflective cavity328and the first and second reflectors316and318to cause a laser pulse to be transmitted through the second reflector318.

During operation, the Q-switch320prevents the laser300from outputting or transmitting the laser pulse until the population inversion in the solid state gain medium308reaches a predetermined level (e.g., a peak level). For example, the Q-switch320, a saturable absorber, is substantially non-transparent until the population inversion reaches the predetermined level. Once the population inversion reaches the predetermined level, the Q-switch320becomes at least partially transparent and the laser pulse passes through the Q-switch320and the second reflector318.

When the laser300is exposed to temperatures between about room temperature and about 200° C., the laser300outputs laser pulses having pulse energies (e.g., 8 mJ, 14 mJ, 22 mJ, etc.) substantially independent of the temperatures. For example, from about room temperature to about 200° C., the laser300outputs laser pulses having pulse energies with a standard deviation within about 10 percent. The deviations are substantially attributable to random fluctuations that occur during operation regardless of the temperatures between about room temperature and about 200° C. such as, for example, creation of the arc in the pump source314, recombination and continuum emission events producing light via the arc, and emitted photon directions from the events. Thus, the laser300outputs laser pulses having substantially constant pulse energies when exposed to temperatures between about room temperature and about 200° C. Also, the laser300advantageously outputs the laser pulses even when subjected to shocks (e.g., a 500 g shock) and/or vibrations (e.g., a 0.5 g^2/√Hz vibration).

FIG. 4is a cross-sectional view of another laser400disclosed herein. During operation, the laser400outputs a laser pulse having a substantially constant pulse energy when the laser400is exposed to temperatures between about room temperature and about 200° C., and, thus, the pulse energy is substantially independent of the temperatures. Also, the laser400advantageously outputs the laser pulses even when subjected to shocks (e.g., a 500 g shock) and/or vibrations (e.g., a 0.5 g^2/√Hz vibration). In some examples, the laser400ofFIG. 4is employed to provide a light source for a variety of spectroscopy techniques (e.g., Raman spectroscopy, absorption spectroscopy, laser induced breakdown spectroscopy, etc.).

The laser400includes a solid state gain medium402having a first end404and a second end406. In some examples, the solid state gain medium402is rod-shaped. In some examples, the solid state gain medium402is alexandrite, Nd:YAG, or any other suitable material. The solid state gain medium402is held by mounts408and410at each of the first and second ends404and406of the solid state gain medium402. In some examples, the mounts408and410include apertures (not shown) and/or the solid state gain medium402is positioned on the mounts408and410such that the mounts408and410are not in the path of the laser pulse during operation.

In the illustrated example, a pump source412such as, for example, a flash lamp or an arc lamp is adjacent the solid state gain medium402. In some examples, the pump source412includes a substantially transparent tube414(e.g., glass, quartz, etc.) filled with a gas (e.g., Xenon, krypton, etc.). In other examples, the pump source is an LED, a diode laser, and/or any other suitable pump source. The pump source412is coupled to an electrical power source (e.g., a capacitor) (not shown). The pump source412is also coupled to the mounts408and410such that longitudinal axes of the pump source412and the solid state gain medium402are substantially parallel.

A reflective cavity416is coupled to the mounts408and410to substantially enclose the solid state gain medium402and the pump source412. The example reflective cavity416illustrated inFIG. 4includes a substantially transparent (e.g., glass) cylinder418at least partially covered by a diffuse reflector420such as, for example, barium sulfate, Teflon, and/or any other suitable diffuse reflector. In other examples, the reflective cavity416is an elliptical mirror. A first end422and a second end424of the reflective cavity416are at least partially transparent and/or include apertures to enable light to travel out of the reflective cavity416and toward a reflective prism426and a reflector428.

In the illustrated example, the reflective prism426is adjacent the first end404of the solid state gain medium402. In some examples, the reflective prism426is retro-reflective. The example reflective prism426ofFIG. 4is coupled to a mount430such as, for example, a flexure mount. The reflector428is adjacent the second end406of the solid state gain medium402. At least a portion of the example reflector428is less than 100 percent reflective to enable the laser pulse to pass through the reflector428during operation. In some examples, a reflectivity of the reflector428is between about 80 percent and about 90 percent. In the illustrated example, the reflector428is coupled to a mount432such as, for example, a flexure mount. In some examples, the reflector428is curved. The reflective prism426and the reflector428are substantially aligned such that, during operation, the reflective prism426and the reflector428provide an optical resonator.

In some examples, the laser400does not include the reflective prism426. In some such examples, a reflector such as, for example, a curved mirror is adjacent the first end404of the solid state gain medium402. In some examples, the reflector428is a reflective prism. In some such examples, the laser400includes another reflector (not shown) disposed along a path of the laser pulse.

The laser400ofFIG. 4includes an optical filter433integrated into the reflector428. In other examples, the optical filter433is disposed along the path of the laser pulse and coupled to another mount (not shown) such as, for example, a flexure mount. In such examples, the optical filter433is disposed between the reflective prism426and the first end404of the solid state gain medium402, between the second end406of the solid state gain medium402and the reflector428, or at any other suitable position along the path of the laser pulse. The optical filter433may be a birefringent tuner, a Lyot filter, an etalon filter, and/or any other suitable filter to control an output wavelength of the laser pulse outputted by the laser400. For example, the optical filter433enables a wavelength of a laser pulse outputted from the laser400having an alexandrite solid state gain medium402to be tuned between about 700 nm and about 820 nm.

The laser400depicted inFIG. 4includes a Q-switch434. In the illustrated example, the Q-switch434is a passive Q-switch such as, for example, a saturable absorber. In some examples, the Q-switch434is an active Q-switch such as, for example, a rotatable reflector or an electro-optic modulator. The example Q-switch434ofFIG. 4is disposed between the second end406of the solid state gain medium402and the reflector428along the path of the laser pulse. In some examples, the Q-switch is coupled (e.g., diffusion bonded, optical contact bonded, etc.) to the solid state gain medium402.

The mounts408,410,428and432are coupled to braces436and438. In some examples, the laser400is disposed in a housing (not shown) in a downhole tool such as, for example, the downhole tool ofFIG. 1, the downhole tool ofFIG. 2, or any other suitable downhole tool. In some examples, the laser400is employed at or near a surface of earth (e.g., in a laboratory).

FIG. 5is a side view of another laser500disclosed herein. The laser500ofFIG. 5includes a monolithic body502. The example monolithic body502includes a solid state gain medium504and a Q-switch506. In some examples, the monolithic body502includes a nonlinear crystal.

In the illustrated example, the solid state gain medium504is side-pumped by a plurality of light emitting diodes (LEDs)508surrounding the monolithic body502to cause a population inversion in the solid state gain medium504. In some examples, the LEDs508emit light corresponding to an absorption peak of the solid state gain medium504. In the illustrated example, a plurality of collimating and/or focusing optics510are disposed between the LEDs508and the monolithic body502to enhance coupling into the solid state gain medium504. In other examples, the LEDs508and the optics510are positioned at an end of the solid state gain medium504to emit light along a length of the solid state gain medium504and, thus, end-pump the solids state gain medium504.

FIG. 6is a rear view of the laser500ofFIG. 5. In the illustrated example, the LEDs508and the optics510are disposed adjacent a top, a bottom, a left side and a right side of the example monolithic body502in the orientation ofFIG. 12. In other examples, the LEDs508and the optics510are disposed at other positions.

FIG. 7illustrates another laser700disclosed herein. In the illustrated example, a downhole tool702(e.g., the example downhole tool ofFIG. 1, the example downhole tool ofFIG. 2, and/or any other suitable downhole tool) is disposed in a borehole704, and a diode laser706is disposed at or near a surface of Earth. The example diode laser706emits light into an optical fiber708via first optics710(e.g., lenses). In the illustrated example, the optical fiber708extends from the surface into the downhole tool702. The example optical fiber708is capable of directing Watts of light into the downhole tool702.

In the illustrated example, the light emitted via the diode laser706travels through the optical fiber708and is emitted into the downhole tool702toward second optics712. The example second optics712direct the light onto an end714of an example monolithic body716. In the illustrated example, the monolithic body716includes a solid state gain medium718(e.g., Nd:YAG) and a Q-switch720. In some examples, the second optics712match a mode of the light to a lasing mode of the solid state gain medium718. In some examples, the monolithic body716includes a nonlinear crystal. In the illustrated example, a reflector722disposed at the end714of the monolithic body716adjacent the second optics712is substantially transparent to the light emitted from the optical fiber708while having a reflectivity of about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) to light at a lasing wavelength of the solid state gain medium718(e.g., 1064 nm for Nd:YAG). As a result, the light emitting from the diode laser706may travel through the reflector722to cause a population inversion in the solid state gain medium718. In the illustrated example, the monolithic body716outputs a laser pulse via the Q-switch720. In some examples, the laser pulse is directed onto a fluid sample (e.g., in a flowline of the downhole tool702, in the borehole, etc.) to perform one or more spectroscopy techniques.

FIGS. 8-13are diagrams of example lasers800,900, and1000disclosed herein, which may be employed to provide light for a variety of spectroscopy techniques utilizing nonlinear wavelength generation such as, for example, optical parametric oscillation, second, third, or fourth harmonic generation, etc. In some examples, the laser800,900, and1000may be used to generate supercontinuum light.

The laser800ofFIG. 8includes a pump source802such as, for example, a flash lamp, an arc lamp, an LED, a laser diode, and/or any other suitable pump source. The example pump source802is adjacent a monolithic body804to transversely pump a solid state gain medium806of the monolithic body804. In the illustrated example, a reflective cavity808substantially encloses the monolithic body804and the pump source802. In some examples, the reflective cavity808is defined by a substantially transparent (e.g., glass) cylinder at least partially covered by a diffuse reflector such as, for example, barium sulfate, Teflon, and/or any other suitable diffuse reflector. In other examples, the reflective cavity808is an elliptical mirror.

The example monolithic body804ofFIG. 8includes a first reflector810, a nonlinear crystal812, a Q-switch814, the solid state gain medium806, and a second reflector816. In the illustrated example, a first end818of the Q-switch814is coupled to the nonlinear crystal812, and a second end820of the Q-switch814is coupled to the solid state gain medium806. In the illustrated example, the first reflector810is disposed on a first end822of the monolithic body804and the second reflector816is disposed on a second end824of the monolithic body804. The example first reflector810is coupled to the nonlinear crystal812, and the example second reflector816is coupled to the solid state gain medium806. In some examples, the first reflector810and/or the second reflector816are film coatings.

In the illustrated example, the first reflector810and the second reflector816provide an optical resonator (i.e., reflect light in a closed path). In some examples, reflective surfaces of the first reflector810and the second reflector816are substantially parallel to each other. In other examples, the first reflector810and the second reflector816are curved. In some such examples, the first reflector810and the second reflector816are curved such that the first reflector810and the second reflector816are substantially confocal or substantially concentric.

The solid state gain medium806is a material in a solid state such as, for example, a chromium doped beryllium aluminum oxide crystal (Cr3+:BeAl2O4) (“alexandrite”), a neodymium-doped yttrium aluminum garnet crystal (Nd:Y3Al5O12) (“Nd:YAG”), or any other suitable material. In some examples, the solid state gain medium806includes a dopant element such as Nd, Yb, Er, Ti, Tm, and/or any other suitable dopant element.

The nonlinear crystal812may be composed of Lithium triborate (LBO), potassium titanyl phosphate (KTP), beta-barium borate (BBO), lithium niobate (LN) and/or any other suitable material. In some examples, the nonlinear crystal812is a periodically poled material such as, for example, periodically poled lithium niobate (PPLN).

During operation of the laser800, the pump source802causes a population inversion in the solid state gain medium806, and the nonlinear crystal812converts light produced via the solid state gain medium806to light having a wavelength different than the light produced via the solid state gain medium806. For example, if the solid state gain medium806is Nd:YAG, the solid state gain medium806produces light having a wavelength of 1064 nm, which the nonlinear crystal812converts to light having a wavelength such as, for example, 532 nm, 354 nm, or 266 nm.

In the illustrated example, one of the first reflector810or the second reflector816is anisotropic. The example first reflector810and the example second reflector816are about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) reflective to the light emitted by the solid state gain medium806(e.g., 1064 nm for Nd:YAG). However, the example second reflector816has a reflectivity of about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) to the light produced via the nonlinear crystal812while the example first reflector810has a reflectivity of less than 100 percent (e.g., 80%, 90%, etc.) to the light produced via the nonlinear crystal812. Thus, the light produced via the solid state gain medium806is substantially reflected between the first reflector810and the second reflector816(i.e., contained in the optical resonator) while the light produced by the nonlinear crystal812(i.e., wavelength shifted light) is outputted via the first reflector810. As a result, the laser800outputs a laser pulse826having a wavelength of the light produced by the nonlinear crystal812.

The laser900ofFIG. 9includes a nonlinear crystal902, a Q-switch904and a solid state gain medium906. In the illustrated example, the nonlinear crystal902, the Q-switch904and the solid state gain medium906are structurally discrete. In the illustrated example, a pump source908(e.g., a flash lamp, an arc lamp, an LED, a laser diode, and/or any other suitable pump source) is disposed adjacent the solid state gain medium906to transversely pump the solid state gain medium906.

In the illustrated example, a reflective cavity910substantially encloses the nonlinear crystal902, the Q-switch904, the solid state gain medium906and the pump source908. In some examples, the reflective cavity910may be defined by a substantially transparent (e.g., glass) cylinder at least partially covered by a diffuse reflector such as, for example, barium sulfate, Teflon, and/or any other suitable diffuse reflector. In other examples, the reflective cavity910is an elliptical mirror.

In the illustrated example, a first reflector912is disposed adjacent a first end914of the reflective cavity910and a second reflector916is disposed adjacent a second end918of the reflective cavity910. The first reflector912and the second reflector916provide an optical resonator (i.e., reflect light in a closed path). In some examples, reflective surfaces of the first reflector912and the second reflector916are substantially parallel to each other. In other examples, the first reflector912and the second reflector916are curved. In some such examples, the first reflector912and the second reflector916are curved such that the first reflector912and the second reflector916are substantially confocal or substantially concentric. In some examples, the first reflector912and/or the second reflector916is a reflective prism (e.g., a retro-reflective prism).

The example solid state gain medium906is a material in a solid state such as, for example, a chromium doped beryllium aluminum oxide crystal (Cr3+:BeAl2O4) (“alexandrite”), a neodymium-doped yttrium aluminum garnet crystal (Nd:Y3Al5O12) (“Nd:YAG”), or any other suitable material. In some examples, the solid state gain medium906includes a dopant element such as Nd, Yb, Er, Ti, Tm, and/or any other suitable dopant element. In the illustrated example, a first end920and a second end922of the solid state gain medium906are oriented at a Brewster angle.

The nonlinear crystal902may be composed of Lithium triborate (LBO), potassium titanyl phosphate (KTP), beta-barium borate (BBO), lithium niobate (LN) and/or any other suitable material. In some examples, the nonlinear crystal902is a periodically poled material such as, for example, periodically poled lithium niobate (PPLN).

During operation of the laser900, the pump source908causes a population inversion in the solid state gain medium906, and the nonlinear crystal902converts light produced via the solid state gain medium906to light having a wavelength different than the light produced via the solid state gain medium906. For example, if the solid state gain medium906is Nd:YAG, the solid state gain medium906can produce light having a wavelength of 1064 nm, which the nonlinear crystal902converts to light having a wavelength such as, for example, 532 nm, 354 nm, or 266 nm.

In the illustrated example, one of the first reflector912or the second reflector916is anisotropic. The example first reflector912and the example second reflector916are about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) reflective to the light emitted by the solid state gain medium906(e.g., 1064 nm for Nd:YAG). However, the example second reflector916has a reflectivity of about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) to the light produced via the nonlinear crystal902while the example first reflector912has a reflectivity of less than 100 percent (e.g., 80%, 90%, etc.) to light produced via the nonlinear crystal902. Thus, the light produced via the solid state gain medium906is substantially reflected between the first reflector912and the second reflector916(i.e., contained in the optical resonator) while the light produced by the nonlinear crystal902(i.e., wavelength shifted light) is outputted via the first reflector912. As a result, the laser900outputs a laser pulse924having a wavelength of the light produced by the nonlinear crystal902.

FIG. 10is a diagram of the laser1000, which may be used to perform a spectroscopy technique utilizing nonlinear wavelength generation. The laser1000ofFIG. 10includes a pump source1002such as, for example, a flash lamp, an arc lamp, an LED, a laser diode, and/or any other suitable pump source. The example pump source1002is adjacent a monolithic body1004to transversely pump a solid state gain medium1006of the monolithic body1004. In the illustrated example, a reflective cavity1008substantially encloses the monolithic body1004and the pump source1002. In some examples, the reflective cavity1008is defined by a substantially transparent (e.g., glass) cylinder at least partially covered by a diffuse reflector such as, for example, barium sulfate, Teflon, and/or any other suitable diffuse reflector. In other examples, the reflective cavity1008is an elliptical mirror. As described in greater detail below, the example monolithic body1004outputs a first laser pulse1010toward a nonlinear crystal1012disposed outside of the reflective cavity1008.

The example monolithic body1004ofFIG. 10includes a first reflector1014, a Q-switch1016, the solid state gain medium1006, and a second reflector1018. In the illustrated example, the Q-switch1016is coupled (e.g., diffusion bonded, optical contact bonded, etc.) to the solid state gain medium1006. In the illustrated example, the first reflector1014is disposed on a first end1020of the monolithic body1004and the second reflector1018is disposed on a second end1022of the monolithic body1004(e.g., the example first reflector1014is coupled to Q-switch1016, and the example second reflector1018is coupled to the solid state gain medium1006). In some examples, the first reflector1014and/or the second reflector1018are film coatings.

The solid state gain medium1006is a material in a solid state such as, for example, a chromium doped beryllium aluminum oxide crystal (Cr3+:BeAl2O4) (“alexandrite”), a neodymium-doped yttrium aluminum garnet crystal (Nd:Y3Al5O12) (“Nd:YAG”), or any other suitable material. In some examples, the solid state gain medium1006includes a dopant element such as Nd, Yb, Er, Ti, Tm, and/or any other suitable dopant element.

The first reflector1014and the second reflector1018provide an optical resonator (i.e., reflect light in a closed path). In some examples, reflective surfaces of the first reflector1014and the second reflector1018are substantially parallel to each other. In other examples, the first reflector1014and the second reflector1018are curved. In such examples, the first reflector1014and the second reflector1018are curved such that the first reflector1014and the second reflector1018are substantially confocal or substantially concentric.

The example second reflector1018is about 100 percent (e.g., 95%, 98%, 99%, 99.9%, etc.) reflective to light emitted by the solid state gain medium1006(e.g., 1064 nm for Nd:YAG). In some such examples, the first reflector1014has a reflectivity of less than 100 percent (e.g., 80%, 90%, etc.) to the light produced via the solid state gain medium1006to enable the monolithic body1004to output the first laser pulse1010(e.g., light) toward the nonlinear crystal1012via the first reflector1014.

In the illustrated example, the nonlinear crystal1012is disposed outside of the reflective cavity1008. The nonlinear crystal1012may be composed of Lithium triborate (LBO), potassium titanyl phosphate (KTP), beta-barium borate (BBO), lithium niobate (LN) and/or any other suitable material. In some examples, the nonlinear crystal1012is a periodically poled material such as, for example, periodically poled lithium niobate (PPLN).

During operation of the laser1000, the pump source1002causes a population inversion in the solid state gain medium1006and the monolithic body1004outputs the first laser pulse1010toward the nonlinear crystal1012. As the first laser pulse1010passes through the nonlinear crystal1012, the nonlinear crystal1012converts the first laser pulse1010to a second laser pulse1024having a wavelength different than the first laser pulse1010. For example, if the solid state gain medium1006is Nd:YAG, the solid state gain medium1006produces the first laser pulse1010having a wavelength of 1064 nm, which the nonlinear crystal1012converts to the second laser pulse1024having a wavelength such as, for example, 532 nm, 354 nm, or 266 nm.

FIG. 11is a diagram of the laser1000in which the nonlinear crystal1012is disposed between a third reflector1100and a fourth reflector1102. In the illustrated example, the third reflector1100, the nonlinear crystal1012, and the fourth reflector1102are disposed outside of the reflective cavity1008along a path of the first laser pulse1010.

In the illustrated example, the third reflector1100and the fourth reflector1102reflect a fundamental wavelength of the first laser pulse1010. As a result, the first laser pulse1010passes through the fourth reflector1102, and the nonlinear crystal1012converts the first laser pulse1010to light having a wavelength different than the first laser pulse1010. In the illustrated example, the third reflector1100and the fourth reflector1102provide an optical resonator for the light produced via the nonlinear crystal1012, and the laser1000outputs the second laser pulse1024via the third reflector1100. Thus, the second laser pulse1024, which has a wavelength of the light produced via the nonlinear crystal1012, is outputted via the third reflector1100.

FIG. 12illustrates the laser1000ofFIG. 11in which the nonlinear crystal1012is coupled to a heat pump1200(e.g., a Peltier thermoelectric device) and a heat sink1202to control a temperature of the nonlinear crystal1012to achieve noncritical phase matching. For example, noncritical phase matching may occur for second harmonic generation of light having a wavelength of 1064 nm by adjusting a temperature of a lithium triborate (LBO) crystal to 148° C.

FIG. 13illustrates the laser1000ofFIG. 11in which a longitudinal axis of the nonlinear crystal1012is nonparallel to an optical axis of the pump source1002. In the illustrated example, the nonlinear crystal1012is oriented such that noncritical phase matching may be achieved.

FIG. 14is a diagram of an example system1400, which may be used to perform laser induced breakdown spectroscopy (LIBS) to, for example, determine an elemental concentration of a fluid and/or identify constituent molecules of the fluid.

The example system1400includes a solid state laser1402. The solid state laser1402may be implemented using, for example, the laser300ofFIG. 3, the laser400ofFIG. 4, the laser500ofFIGS. 5-6, the example lasers700ofFIG. 7, and/or one of the example lasers800,900,1000, or1100ofFIGS. 8-13. In the illustrated example, a laser pulse1404outputted via the solid state laser1402is focused via focusing optics1406onto a fluid sample1408(e.g., liquid(s) and/or gas(es) in a flowline of a downhole tool, fluid in a borehole, etc.). As a result, a portion of the fluid sample1408is ionized such that plasma1410including ion cores and free electrons are formed.

In the illustrated example, light1412emitted from the plasma1410is collected via collection optics1414and directed to a first detector1416and a second detector1418via a fiber optic bundle1420. Other examples include other numbers of detectors (e.g., 1, 3, 4, 5, etc.). In the illustrated example, the first detector1416includes a first pair of collimating and focusing optics1422and1424and a first bandpass optical filter1426. The example second detector1418includes a second pair of collimating and focusing optics1428and1430and a second bandpass optical filter1432. In some examples, the first detector1416and/or the second detector1418is a spectrometer including a plurality of wavelength channels (e.g., an echelle grating based spectrometer) and/or a monochromator. Based on the light1412emitted from the plasma1410, the first detector1416and/or the second detector1418determine a characteristic of the fluid sample1408(e.g., elemental concentrations, concentration of tracer elements, etc.).

FIG. 15is a diagram of an example system1500, which may be used to perform absorption spectroscopy. Absorption spectroscopy may be performed to determine a concentration of constituent molecules (e.g., saturated compounds such as, for example, methane or ethane) of a fluid.

The example system1500includes a solid state laser1502, which may be implemented using, for example, one of the example lasers800,900, and1000ofFIGS. 8-13. In the illustrated example, light1504emitted by the example solid state laser1502is directed onto a fluid sample1506(e.g., fluid flowing through a flowline, fluid disposed in a borehole, etc.). Light1508emitted by the fluid sample (i.e., light that passes through the fluid sample) is collected via collection optics1510and directed to a first detector1512and a second detector1514via a fiber optic bundle1516.

In the illustrated example, the first detector1512includes a first pair of collimating and focusing optics1518and1520and a first bandpass optical filter1522. The example second detector1514includes a second pair of collimating and focusing optics1524and1526and a second bandpass optical filter1528. In some examples, the first detector1512and/or the second detector1514includes a spectrometer including a plurality of wavelength channels (e.g., an echelle grating based spectrometer). Based on the light1508emitted by (i.e., passing through) the fluid sample1506, a characteristic of the fluid sample1506may be determine via the first detector1512and/or the second detector1514.

FIGS. 16, 17, 18 and 19illustrate example spectroscopy systems1600,1700,1800and1900which may be used to perform Raman spectroscopy (e.g., a Raman spectrometer) for sample composition analysis, including, for example, the Raman spectroscopy techniques described in U.S. Publication No. 2008/0111064, titled “Downhole Measurement of Substances in Earth Formations,” filed Nov. 10, 2006.

In illustrative embodiments, the spectroscopy system provides collimated excitation light to the sample and collects scattered light from the sample. Such spectroscopy systems use collimated excitation light to avoid high intensity excitation light within the sample and adjacent optics, which prevents damage to the adjacent optics, ionization of the sample, and/or other non-linear interactions between the excitation light and the sample. The example system1600ofFIG. 16includes a solid state laser1602to emit a first beam1604of light. The example solid state laser1602ofFIG. 16may be implemented using the laser300,400,500,600,700and/or any other suitable solid state laser. In the illustrated example, the solid state laser1602is coupled to a controller1606(e.g., a microprocessor) via a high voltage or pulse forming network1608. In the illustrated example ofFIG. 16, the first beam1604(e.g., excitation light) is directed via a mirror1610and a first filter1612(e.g., a dichroic filter) through a window1614(e.g., a sapphire window) onto a sample1616(e.g., a solid, liquid and/or gas). In the illustrated example, the first beam1604passes through a second filter1618disposed between the mirror1610and the first filter1612. A first lens1620and a second lens1622, disposed between the first filter1612and the window1614, collimate the first beam1604and direct the first beam1604onto the sample1616. As explained above, the first beam1604strikes the sample1616as a collimated beam and, in this manner, prevents high intensity excitation light within the sample. In some embodiments of the present disclosure, the interrogated sample volume1616ofFIG. 16is located at a specific distance from the window1614. The distance of the sample volume from the window is controlled by the choice of lens elements1622ofFIG. 16. It is understood that the present disclosure is not limited to any particular choice of length resulting from different combinations of said lens elements. In the specific illustrated example, the window1614is a distance from the sample1616substantially equal to the inverse of an absorption coefficient of the sample1616at a wavelength of light to be scattered by the sample1616. In other examples, the window1614is other distances from the sample1616(e.g., less than three time the inverse of the absorption coefficient).

In the illustrated example, the first beam1604interacts with the sample1616(e.g., Raman scattering, absorption and/or emissions from a plasma formed by breakdown of a portion of the sample1616, etc.). A second beam1624of light emitted from the sample1616(e.g., diverging Raman scattered light) passes through the window1614and is focused onto a fiber bundle1626via the first lens1620and the second lens1622. In the illustrated example, the second beam1624is also directed through the first filter1612. Via the fiber bundle1626, the second beam1624is directed to a plurality of detectors1628,1630,1632,1634(e.g., spectrometers, photodiodes, etc.). In the illustrated examples, each of the plurality of detectors1628,1630,1632,1634is coupled to the controller1606. Based on the second beam1624(e.g., an intensity of CCvand CHvchannels), a characteristic of the sample1616(e.g., a composition of gas condensates) may be determined. In some examples, a reduction in collected Raman scattered photons (e.g., due to absorption from one or more constituents of the sample1616) is determined and/or corrected for by measuring a concentration of the one or more constituents. In some examples, the concentration of the one or more constituents is measured by determining photons scattered by a Raman band of the one or more constituents.

The example system1700ofFIG. 17includes a solid state laser1702to emit a first beam1704of light. The example solid state laser1702ofFIG. 17may be implemented using the example lasers300,400,500,600,700and/or any other suitable solid state laser. In the illustrated example, the solid state laser1702is coupled to a controller1706(e.g., a microprocessor). In the example system1700ofFIG. 17, the first beam1704is directed via a first filter1708(e.g., a dichroic filter) through a window1710(e.g., a sapphire window) onto a sample1712(e.g., a liquid, solid and/or gas). In the illustrated example, the first beam1704(e.g., excitation light) passes through a second filter1714disposed between the solid state laser1702and the first filter1708. The example system1700also includes a plurality of optical members. In this case, a first lens1716and a second lens1718, disposed between the first filter1708and the window1710, collimate the first beam1704and direct the first beam1704onto the sample1712. As explained above, the first beam1704strikes the sample1716as a collimated beam and, in this manner, prevents high intensity excitation light within the sample. In the illustrated example, the window1710is a distance from the sample1712substantially equal to three times an inverse of an absorption coefficient of the sample1712at a wavelength of light to be scattered by the sample1712. In other examples, the window1710is other distances from the sample1712(e.g., less than three time the inverse of the absorption coefficient).

In the illustrated example, the first beam1704interacts with the sample1712(e.g., Raman scattering, absorption and/or emissions from a plasma formed by breakdown of a portion of the sample1712, etc.). A second beam1720of light emitted from the sample1712(e.g., diverging Raman scattered light) passes through the window1710and is focused onto a fiber bundle1722via the first lens1716and the second lens1718. In the illustrated example, the second beam1720is also directed through the first filter1708. Via the fiber bundle1722, the second beam1720is directed to a plurality of detectors1724,1726,1728and1730(e.g., spectrometers, photodiodes, etc.). Based on the second beam1720(e.g., an intensity of CCvand CHvchannels), a characteristic of the sample1712(e.g., a composition of gas condensates) may be determined. In some examples, a reduction in collected Raman scattered photons (e.g., due to absorption from one or more constituents of the sample1712) is determined and/or corrected for by measuring a concentration of the one or more constituents. In some examples, the concentration of the one or more constituents is measured by determining photons scattered by a Raman band of the one or more constituents.

The first lens1716and the second lens1718may have a variety of different focal lengths, diameters and configurations to provide collimated excitation light to the sample. The present disclosure is not limited to the configurations illustrated inFIG. 16andFIG. 17.

In another example, as shown in the system1800ofFIG. 18, an internal beam waist between the first lens1716and the second lens1718is eliminated by positioning the first lens1816between the fiber1722and the dichroic beam splitter1708and inserting a third lens element1817between the second lens1718and the window1710. In this configuration, the light passing through the dichroic beam splitter1708is collimated.

In yet another example, as shown in the system1900ofFIG. 19, lens optics are provided to modify the excitation beam diameter (e.g., expand or compress) that is emitted by the laser1702. In the particular embodiment ofFIG. 19, a first lens1913and a second lens1915are inserted between the dichroic beam splitter1708and the laser1702. Such lens optics may also be incorporated in the system1600ofFIG. 16, the system1700ofFIG. 17, or the system1800ofFIG. 18.

In yet another example, the system reduces the beam intensity at the window and/or the sample by using a beam homogenizer. In this manner, various embodiments of the system further reduce high intensity excitation light within the sample and adjacent optics, which prevents damage to the adjacent optics, ionization of the sample, and/or other non-linear interactions between the excitation light and the sample. In one embodiment, as shown in the system ofFIG. 20, the system2000includes a non-imaging beam homogenizer. The non-imaging beam homogenizer includes a micro-lens array2015that is inserted between the laser1702and the filter1714. In some embodiments, the micro lens array2015comprises an array of spherical lenslets2400, as shown inFIG. 24, or a pair of crossed arrays of cylindrical lenslets2200, as shown inFIG. 22. The lenslet array divides the input beam profile into a plurality of slices. A spherical lens1718maps the individual beams to the sample focal plane1712producing a more uniform intensity profile.

In yet another example, as shown in the system ofFIG. 21, the beam intensity at the window1710is reduced by providing an imaging beam homogenizer, which includes a pair of micro-lens arrays2113and2115that are inserted between the laser1702and the filter1714. In some embodiments, the micro lens arrays comprise an array of spherical lenslets2400, as shown inFIG. 24, or a pair of crossed arrays of cylindrical lenslets2200, as shown inFIG. 22. The lenslet array divides the input beam profile into a plurality of slices. A spherical lens1718reimages the individual slices to the sample focal plane1712producing a more uniform intensity profile.

The present disclosure is not limited to the configurations illustrated inFIG. 20andFIG. 21. For example, in some embodiments, the micro lens arrays2113and2115in the system2100ofFIG. 21can be combined to form a fly's eye condenser array2300, as shown inFIG. 23. In another embodiment, the micro lens arrays2113and2115may be a crossed fly's eye condenser array.

FIG. 25depicts an example flow diagram representative of processes that may be implemented using, for example, computer readable instructions. The example process ofFIG. 20may be performed using a processor, a controller and/or any other suitable processing device. For example, the example process ofFIG. 25may be implemented using coded instructions (e.g., computer readable instructions) stored on a tangible computer readable medium such as a flash memory, a read-only memory (ROM), and/or a random-access memory (RAM). As used herein, the term tangible computer readable medium is expressly defined to include any type of computer readable storage and to exclude propagating signals. The example process ofFIG. 25may be implemented using coded instructions (e.g., computer readable instructions) stored on a non-transitory computer readable medium such as a flash memory, a read-only memory (ROM), a random-access memory (RAM), a cache, or any other storage media in which information is stored for any duration (e.g., for extended time periods, permanently, brief instances, for temporarily buffering, and/or for caching of the information). As used herein, the term non-transitory computer readable medium is expressly defined to include any type of computer readable medium and to exclude propagating signals.

The example process ofFIG. 25may be implemented using any combination(s) of application specific integrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)), field programmable logic device(s) (FPLD(s)), field programmable gate array(s) (FPGA(s)), discrete logic, hardware, firmware, etc. Also, one or more operations depicted inFIG. 20may be implemented manually or as any combination(s) of any of the foregoing techniques, for example, any combination of firmware, software, discrete logic and/or hardware. In some examples, the example process ofFIG. 20may be implemented using the logging and control unit ofFIG. 1A, the electronics and processing system166, an uphole processor and/or a downhole control system. Further, one or more operations depicted inFIG. 25may be implemented at the surface and/or downhole.

Further, although the example process ofFIG. 25is described with reference to the flow diagram ofFIG. 25, other methods of implementing the process ofFIG. 25may be employed. For example, the order of execution of the blocks may be changed, and/or some of the blocks described may be changed, omitted, sub-divided, or combined. Additionally, one or more of the operations depicted inFIG. 25may be performed sequentially and/or in parallel by, for example, separate processing threads, processors, devices, discrete logic, circuits, etc.

FIG. 25depicts an example process2500disclosed herein. The example process2500begins by disposing a laser (e.g., the example lasers300,400,500,700,800,900,1000, the example monolithic body716, the solid state laser1402, the solid state laser1502, etc.) in an environment in which a temperature is greater than 100 degrees Celsius (block2502). In some examples, the laser includes a monolithic body having a first reflector, a second reflector, and a solid state gain medium disposed between the first reflector and the second reflector. In some examples, the environment is downhole. In some such examples, the laser is disposed in a downhole tool (e.g., the production logging100, the wireline tool200, etc.), and the downhole tool is lowered into a borehole.

At block2504, a pump source (e.g., one or more of the example pump sources314,412,802,908,1002, the LEDs508ofFIG. 5, the diode laser706ofFIG. 7, etc.) is energized to cause a population inversion in the solid state gain medium of the laser to cause the laser to output a laser pulse. In some examples, a flash lamp, a plurality of LEDs, and/or one or more diode lasers are energized to cause a population inversion in the solid state gain medium. In some examples, light from the pump source is directed onto a fiber optic cable, which directs the light onto the solid state gain medium.

At block2506, the laser pulse is directed onto a sample. In some examples, the laser pulse is directed onto a sample via collimating optics (e.g., the optics1620and1622ofFIG. 16, the optics1716and1718ofFIG. 17, the optics1716and1718and1817ofFIG. 18, the optics1913and1915ofFIG. 19). At block2508, light interacting with the sample is directed (e.g., collected and focused by the optics1620and1622ofFIG. 16, the optics1716and1718ofFIG. 17, etc., the optics1816and1818and1817ofFIG. 18, etc., the optics1913and1915ofFIG. 19, etc.) onto a detector. In some such examples, the detector determines one or more characteristics of the sample based on the light interacting with the sample (e.g., light scattered by constituents of the sample).