Source: http://www.google.com/patents/US7142568?dq=actionscript
Timestamp: 2016-12-04 18:54:47
Document Index: 448677225

Matched Legal Cases: ['§ 120', 'Application No. 60', 'Application No. 60', 'Application No. 60', 'Application No. 60', '§ 119']

Patent US7142568 - High-power blue and green light laser generation from high-powered diode lasers - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA device for generating blue or green laser light, comprising an infrared high power semiconductor laser or an infrared high power semiconductor laser bar or array, a diffractive optical device, and an optical device utilizing a non-linear crystal to generate the blue or green laser light....http://www.google.com/patents/US7142568?utm_source=gb-gplus-sharePatent US7142568 - High-power blue and green light laser generation from high-powered diode lasersAdvanced Patent SearchTry the new Google Patents, with machine-classified Google Scholar results, and Japanese and South Korean patents.Publication numberUS7142568 B2Publication typeGrantApplication numberUS 10/768,426Publication dateNov 28, 2006Filing dateJan 29, 2004Priority dateAug 31, 1999Fee statusLapsedAlso published asUS20030026314, US20040184490Publication number10768426, 768426, US 7142568 B2, US 7142568B2, US-B2-7142568, US7142568 B2, US7142568B2InventorsRuey-Jen HwuOriginal AssigneeRuey-Jen HwuExport CitationBiBTeX, EndNote, RefManPatent Citations (23), Non-Patent Citations (2), Classifications (13), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetHigh-power blue and green light laser generation from high-powered diode lasers
US 7142568 B2Abstract
A device for generating blue or green laser light, comprising an infrared high power semiconductor laser or an infrared high power semiconductor laser bar or array, a diffractive optical device, and an optical device utilizing a non-linear crystal to generate the blue or green laser light.
This application is a continuation of application Ser. No. 10/197,151, filed Jul. 15, 2002 now abandoned; which in turn is a continuation of application Ser. No. 09/652,527, filed Aug. 31, 2000 now abandoned, priority from the filing date of which is hereby claimed under 35 U.S.C. § 120, which claims the benefit U.S. Provisional Application No. 60/156,982, filed Oct. 1, 1999; U.S. Provisional Application No. 60/157,381, filed Oct. 1, 1999; U.S. Provisional Application No. 60/151,664, filed Aug. 31, 1999; and U.S. Provisional Application No. 60/151,779, filed Aug. 31, 1999, the benefit of which is hereby claimed under 35 U.S.C. § 119.
The present invention relates to high-powered laser sources; more specifically, the present invention relates to an apparatus for generating high-powered green and blue light lasers.
The present invention provides a system and method for generating a high-power blue or green light laser beam. The present invention utilizes a compact, low-cost design to produce a high-power, stable, single-mode output beam from an unstable, multimode diode laser source. More specifically, the high-power laser source is an infrared broad-area semiconductor laser having at least one watt of output power or a broad-area semiconductor laser bar or array having at least twenty watts of output power. The high-power multimode laser source is focused into a small area and directed into a nonlinear crystal through the use of diffractive optics. In one case, the light beam passing through the nonlinear crystal generates a blue laser light through frequency doubling and, in another case, generates a single mode longer wavelength laser light, which is converted to a green laser light through an alternative nonlinear crystal. The blue or green light is produced through frequency doubling in the nonlinear crystal. The use of diffractive optics effectively corrects longitudinal spherical aberrations created by the conventional lenses and, in addition, the diffractive optics effectively focuses the output beams from broad-area semiconductor lasers, broad-area semiconductor laser bars, or laser arrays. For the case of the high-power, multimode laser source directly generating a blue or green laser light, diffractive optics are used to provide the necessary feedback to obtain a single mode laser light prior to entering the nonlinear crystal for frequency doubling.
FIGS. 1A–1B illustrate perspective and side views of a semiconductor laser device that can be used in several embodiments of the present invention;
FIGS. 2A–2B are schematic illustrations of an embodiment of the laser source utilizing an external reflection feedback mechanism;
FIGS. 16A–16C illustrate end, perspective, and side views, respectively, of an amplified corrected laser beam as it enters a gain medium.
The semiconductor laser 101 emits light from aperture 51 in a widely divergent beam, also referred to a broad area laser beam, with an angle of divergence in the x-z plane greater than about 80° and an angle of divergence in the y-z plane up to about 16°. The semiconductor laser 101 can be formed of a gallium aluminum arsenic compound or other suitable material known to those skilled in the art.
FIGS. 2A–2B are schematic illustrations of one embodiment of the present invention where the laser source 700 utilizes an external feedback mechanism 300 and 301 to improve the quality of the laser beam directed into a coupling lens 120 and a ring resonator 121. In this embodiment, the feedback mechanism alternatively utilizes reflective optical members 105 and 107 to produce optical feedback that improves the quality of the laser beam. More specifically, the external optical reflector members 105 and 107 create a laser light beam that has a normal curve, for example, a Gaussian or quasi-Gaussian profile. These profiles provide a high degree of redistribution of the original signal in its feedback, i.e., the feedback is not at all proportional to the original signal, to discourage the filamentary behavior of the output of the broad-area laser diode. Other curved surfaces such as a spherical profile can also provide a certain level of mode control. A Gaussian beam has many desirable qualities with one being that a Gaussian beam can be manipulated to be an eigenmode of an optical cavity with finite-size spherical mirrors. Other benefits utilizing an external optical reflector are further described in U.S. Pat. No. 6,002,703 to Hwu et al., entitled “Gaussian Profile Promoting Cavity For Semiconductor Laser,” the disclosure of which is specifically incorporated herein by reference.
The laser source 700 depicted in FIG. 2A comprises a semiconductor laser 101, an external optical reflector 107, a beam splitter 102 a nonlinear crystal 128 and a plurality of mirrors 122–126 that are operatively arranged to create a ring resonator 121. The optical reflector 107 preferably has a substantially parabolic cavity 108. The optical reflector 107 is oriented such that parabolic cavity 108 faces the aperture 51 of semiconductor laser 101. The semiconductor laser 101 is positioned so that aperture 51 is located at the focal point “f” of parabolic cavity 108. The external optical reflector 101, beam splitter 102 and semiconductor laser 101 are collectively referred to herein as a Gaussian optical device 300.
The beam splitter 102 is positioned between semiconductor laser 101 and optical reflector 107 at a location such that a beam 150 is incident on the beam splitter 102. The beam splitter 102 is oriented at a suitable angle in order to deflect a portion of the reflected light from optical reflector 107 away from the Gaussian optical device 300. For example, the beam splitter 102 can be at an angle of about 45° with respect to the direction of light propagation, i.e., the z direction shown in FIG. 1A. The beam splitter 102 can be formed of light transmissive materials such as various plastics or glass. In addition, a variety of conventional optical coatings or layers are optionally applied to the surfaces of beam splitter 102 to produce the desired reflectivity, transmissivity, or deflection properties for a particular application.
During operation of the laser source 100, the semiconductor laser 101 emits a diverging beam 150 that is incident upon the beam splitter 102 and the optical reflector 107. The beam 150 is reflected back towards the beam splitter 102 and the facet (51 of FIG. 1A) of semiconductor laser 101. A portion of the beam 150 is transmitted back through the beam splitter 102 toward the facet 51 to produce an optical feedback effect. The remaining portion of beam the 150 is deflected by the beam splitter 102 at an angle of about 90° with respect to the direction of light propagation, i.e., the z direction shown in FIG. 1A. The portion of the beam 151 that is deflected by the beam splitter 102 has substantially reduced or no filamentation.
FIG. 3 is a schematic view of a blue and green laser source 100 formed in accordance with yet another embodiment of the present invention. Depending on the configuration, the laser source 100 can produce a stable, high-power, single-mode blue (for example 490 nm) laser beam from a single source semiconductor laser having a wavelength of 980 nm. The laser source 100 comprises a semiconductor laser 101, a volume holographic transmission grating (VHTG) 110, a high-reflectivity mirror 111, a coupling lens 120, a nonlinear crystal 128, and a plurality of mirrors 122–126 that are operatively arranged to create a ring resonator 121. Optionally, a focusing (coupling) lens (not shown) can be placed between the semiconductor laser 101 and the volume holographic transmission grating 110. In this exemplary embodiment, the coupling lens 120 is placed at a distance from the semiconductor laser 101 equal to the focal length of coupling lens. The semiconductor laser 101, VHTG 110, and high-reflectivity mirror 111 are collectively referred to herein as a VHTG system 200.
The VHTG output beam 45 is received by a coupling lens 120, which focuses the output beam 46 into the ring resonator 121 (components 122–126 ). The ring resonator 121 is configured in a manner consistent with the constriction of FIGS. 2A and 2B and concentrates the corrected laser beams 46, having better spatial mode, into a nonlinear crystal 128, which in turn, produces a green or blue output beam 49. As noted above, the wavelength of the source laser determines the color of the laser. For green light generation, the laser source may have a wavelength of approximately 1000 nm and a nonlinear crystal may be Potassium Titanium Oxide Phosphate (KTP), Lithium Triborate (LBO), or other like materials. For blue light generation, the laser source may have a wavelength of approximately 900 nm and the nonlinear crystal may be Lithium Triborate (LBO), Ammonium Dihydrogen Phosphate (ADP), ADTP, or other like materials. In the embodiment of FIG. 3, tuning is achieved by rotating the high-reflectivity mirror 111 and the diffractive optical reflector 105, respectively. When the high-reflectivity mirror 111 and the diffractive optical reflector 105 are tilted, the feedback beam will enter the semiconductor laser 101 (100-μm width) at different incident angles, thereby changing the spatial output.
FIG. 6 is a side view of a blazed diffraction grating 114, a device that can be used for mode controlling of a high-power laser source by providing feedback that is not directly proportional to its original signal. As shown in FIG. 6, angled ridges cut into the glass are configured to spread the light as it exits the surface of the diffraction grating 114. For instance, when the beam near the top of the device 304 exits the diffraction grating 114, it is redirected at an angle approximate to 30° from the beam's original path 304. Also shown in FIG. 6, other etchings are created to redirect the light at other angles, such as beam 307, having a redirection of approximately 19.5°, and beam 310 having a redirection of approximately 14.5°.
where Ef is the forward traveling wave, Eb is the backward traveling wave, Γ is the transverse confinement factor, α is the linewidth-enhancement factor, αint is the internal loss, n2 is the Kerr coefficient, and g(N)=α(N−N0) is the local carrier-dependent gain, which is linearly related to the carrier density N(x,z).
The above equations can give the whole picture of the beam propagation inside the laser gain region, located in the active layer 50 (see FIG. 1A). With the use of an external cavity, the boundary conditions are defined by the following equations (3a) and (3b):
E f(x,0)=√{square root over (R 0)}E b(x,0)+∫E b(x,0)exp(iφ b(x,x′))dx′ (3a)
E b(x,0)=√{square root over (R 0)}E f(x,0)+∫E f(x,0)exp(iφ f(x,x′))dx′ (3b)
The wave equations (1a) and (1b) are solved iteratively by the split-step Fourier method. For every iteration, the forward and backward traveling beams are calculated using the fast Fourier transform (FFT) algorithm described in Agrawal, J. Appl. Phys., Vol. 56, pp. 3100–3109 (1984), the disclosure of which is herein incorporated by reference. At the facets, the two beams are related by the boundary conditions. The integration across the boundary area is carried out each time. The carrier density distributions are solved through a tri-diagonal matrix method using the finite-difference approximation of the second order derivative term.
FIG. 13 is schematic illustration of another embodiment of the laser source 100 shown in FIGS. 2A, 2B, 3, and 4 utilizing diffractive optics to correct the longitudinal spherical aberrations of the laser beam emitted from the semiconductor laser 101. The embodiment of FIG. 13 comprises a hybrid coupler 115, a ring resonator 121 (components 122–126), and a nonlinear crystal 128. In this embodiment, the ring resonator 121 and a nonlinear crystal 128 are configured in a manner similar to the embodiments of FIGS. 2A, 2B, 3, and 4. The purpose of the hybrid coupler 115 is to effectively focus the output beam from the semiconductor laser 101.
FIGS. 16A–16C, respectively, illustrate end, perspective, and side views of the laser beam 2150 as it enters the gain medium 2124 (see FIG. 15). These diagrams are provided for illustrative purposes to show how the diverging beams of the diode bar or diode array are focused by diffractive beam focusing device 2001 into a converging pattern as shown by laser beam 1957. FIG. 16A illustrates a plurality of intensity distribution end views 1601–1605 of the laser beam 1957 at the point where it strikes the gain medium 2124. As shown in FIG. 16A, the top four patterns 1601–1604 do not have uniform distributions, a laser beam that is not desirable in the above described embodiments. However, the bottom beam pattern 1605 does show a preferred laser beam having a uniform distribution, such as the beam having a Gaussian profile described above with reference to FIGS. 2A and 2B. FIGS. 16B and 16C show how the reflective surface with a high order polynomial function such as a parabolic function helps to direct the output of multiple single broad-area semiconductor lasers (in the form of a bar or array) into the small cross section of the gain medium 2124 end surface.
Returning to FIG. 15, once the corrected laser beam 2155 is passed through the reflective optic devices 2102–2103 and coupled to a gain medium 2124, the light passes through a nonlinear crystal 2120 in a manner similar to the above described embodiments with reference to FIGS. 2A, 2B, 3, and 4. By the use of the nonlinear crystal 2120, the second harmonic generated will provide the green or blue laser light. More specifically, gain medium 2124, which can be Nd:YAG, outputs a light beam 2155 with a 920 or 1064 nm wavelength, and is positioned in a 920 or 1064 nm laser cavity extending between a mirror 2121 and a beam splitter 2111, also referred to as an output mirror or coupler mirror.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3637929 *Sep 30, 1968Jan 25, 1972Bell Telephone Labor IncOptical scanning apparatus utilizing a re-entrant laser beamUS5046803 *Dec 8, 1989Sep 10, 1991North American Philips Corp.Actively phased matched frequency doubling optical waveguideUS5067134Mar 8, 1991Nov 19, 1991U.S. Philips Corp.Device for generating blue laser lightUS5185752Feb 18, 1992Feb 9, 1993Spectra Diode Laboratories, Inc.Coupling arrangements for frequency-doubled diode lasersUS5222088Nov 1, 1991Jun 22, 1993Hoya CorporationSolid-state blue laser device capable of producing a blue laser beam having high powerUS5295144Jun 1, 1992Mar 15, 1994Adlas Gmbh & Co. KgLaserUS5305345Sep 25, 1992Apr 19, 1994The United States Of America As Represented By The United States Department Of EnergyZigzag laser with reduced optical distortionUS5610934Oct 13, 1995Mar 11, 1997Polaroid CorporationMiniaturized intracavity frequency-doubled blue laserUS5623510May 8, 1995Apr 22, 1997The United States Of America As Represented By The United States Department Of EnergyTunable, diode side-pumped Er: YAG laserUS5651019Apr 28, 1995Jul 22, 1997The United States Of America As Represented By The Secretary Of The NavySolid-state blue laser sourceUS5651021Apr 21, 1994Jul 22, 1997The Commonwealth Of AustraliaDiode pumped slab laserUS5691989Sep 14, 1993Nov 25, 1997Accuwave CorporationWavelength stabilized laser sources using feedback from volume hologramsUS5809048Jul 9, 1997Sep 15, 1998Mitsui Petrochemical Industries, Ltd.Wavelength stabilized light sourceUS5912910May 17, 1996Jun 15, 1999Sdl, Inc.High power pumped mid-IR wavelength systems using nonlinear frequency mixing (NFM) devicesUS5982788Nov 5, 1997Nov 9, 1999California Institute Of TechnologySemi-monolithic cavity for external resonant frequency doubling and method of performing the sameUS5982805Jan 15, 1997Nov 9, 1999Sony CorporationLaser generating apparatusUS6002703Jan 28, 1998Dec 14, 1999University Of Utah Research FoundationGaussian profile promoting cavity for semiconductor laserUS6021141Feb 28, 1997Feb 1, 2000Sdl, Inc.Tunable blue laser diodeUS6094297Jul 7, 1998Jul 25, 2000Trw Inc.End pumped zig-zag slab laser gain mediumUS6097742Mar 5, 1999Aug 1, 2000Coherent, Inc.High-power external-cavity optically-pumped semiconductor lasersUS6100975Apr 3, 1998Aug 8, 2000Process Instruments, Inc.Raman spectroscopy apparatus and method using external cavity laser for continuous chemical analysis of sample streamsUS6108356Mar 5, 1999Aug 22, 2000Photonics Industries International, Inc.Intracavity optical parametric oscillatorsUS6414973 *Aug 31, 2000Jul 2, 2002Ruey-Jen HwuHigh-power blue and green light laser generation from high powered diode lasers* Cited by examinerNon-Patent CitationsReference1Pan, M.-W., et al., "Spatial and Temporal Coherence of Broad-Area Lasers with Grating Feedback," Journal of the Optical Society of America B 15(10):2531-2536, Oct. 1998.2Pan, M.-W., et al., SIAM Activity Group on Dynamical Systems, abstract entitled "Spatio-Temporal Dynamics of Broad-Area Semiconductor Lasers with Optical Feedback," Program for Society for Industrial and Applied Mathematics Program and Abstracts, Snowbird, Utah, May 18-22, 1997, p. 39.Classifications U.S. Classification372/19, 372/25International ClassificationH01S5/20, H01S5/14, H01S3/098, G02F1/37Cooperative ClassificationG02F2001/372, G02F1/37, H01S5/141, H01S2301/18, H01S5/2036, H01S5/14European ClassificationH01S5/14Legal EventsDateCodeEventDescriptionJul 5, 2010REMIMaintenance fee reminder mailedNov 29, 2010SULPSurcharge for late paymentNov 29, 2010FPAYFee paymentYear of fee payment: 4Jul 11, 2014REMIMaintenance fee reminder mailedNov 28, 2014LAPSLapse for failure to pay maintenance feesJan 20, 2015FPExpired due to failure to pay maintenance feeEffective date: 20141128RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services