Abstract:
A surgical system that ablates soft tissue. The system may include a fiber laser oscillator as the gain medium that emits electromagnetic radiation. The system may process the electromagnetic radiation, and direct the electromagnetic radiation on to the soft tissue to be ablated. Due at least in part to the nature of the electromagnetic radiation emitted by the fiber laser oscillator, the system may provide various enhancements, such as a higher power conversion efficiency, a longer lifetime, less heat dissipation, a more compact design, and/or other enhancements, for example. The system may also generate electromagnetic radiation with a relatively high beam quality. This may reduce beam divergence and beam spot size on targeted soft tissue, thereby enhancing power density in the electromagnetic radiation guided to the soft tissue. This enhanced power density may facilitate effective ablation.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application entitled “Apparatus and Method for Soft Tissue Ablation Employing High Power Harmonic Fiber Laser” No. 60/691,528 filed Jun. 17, 2005, the entire content of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to laser soft tissue ablation and in particular to laser prostatectomy. 
     BACKGROUND OF THE INVENTION 
     Benign Prostatic Hyperplasia (BPH) can cause urinary frequency, dysuria and incomplete bladder emptying. The surgical “gold standard” for treating BPH has been the transurethral electrosurgical resection of obstructing prostatic tissue. Since its introduction some 50 years ago, transurethral resection of the prostate (TURP) has become the most widely used surgical therapy for BPH. Unfortunately, TURP associates with numerous side effects. 
     In the past decade, laser prostate surgery has become an alternative option to treat BPH, which troubles effected men with symptoms such as urinary frequency, dysuria and incomplete bladder emptying. In laser prostate surgery, a high power laser beam may be delivered to target prostate tissue through an optical fiber that is introduced through an endoscope or cystoscope. The effectiveness of this treatment for BPH (or for the removal of other soft tissue) may depend on a number of factors, including wavelength, power density, pulse duration, pulse fluence and/or other factors. 
     Conventional laser ablation systems implemented in laser prostate surgery may include high average power (60-80 W) Nd:YAG laser with a wavelength of 1064 nm. The electromagnetic radiation emitted by these systems may heat up the laser-irradiated tissue to boiling temperature. This may evaporate a top layer of the tissue and coagulate an under layer of the tissue. The conventional systems tend to employ Nd:YAG lasers because they may be capable of emitting electromagnetic radiation with an enhanced hemostatic effect. For example, the radiation may penetrate the tissue to a 7 mm penetration depth. But, with the Nd:YAG systems, this penetration may create a thick layer of tissue coagulation. For this and other reasons, conventional systems employing an Nd:YAG laser may not be as effective as TURP in the treatment of obstructive BPH. 
     Other conventional systems for ablating soft tissue, such as prostate tissue have implemented high power (60-100 W) Ho:YAG lasers with a wavelength of 2140 nm. Electromagnetic radiation produced by these systems may by absorbed by water, and can thus evaporate soft tissue effectively. Under limited circumstances, Ho:YAG laser surgery may produce a clinical outcome comparable with TURP. However, Ho:YAG laser surgery may provide various technical problems, and may not currently be practical for widespread usage. 
     In still other conventional systems, a 60 W average power, Q-switched and frequency-doubled Nd:YAG laser may be used for the ablation of soft tissue in BPH treatment. In these systems, the laser may be lamp pumped to produce quasi-CW Q-switched pulses at 532 nm. Electromagnetic radiation at this wavelength is transparent in water but may be selectively absorbed by oxyhemoglobin in soft tissue. These systems may effectively vaporize and ablate soft tissue and concurrently achieve some level of hemostasis. The surgical outcome is comparable with TURP while the complication is significantly reduced. However, as with the Ho:YAG systems, technical problems with the implementation of an Nd:YAG laser in a clinical system for ablating soft tissue exist. 
     For example, the power conversion efficiency of these systems may be relatively low. In some instances, this efficiency may be below 3%. This may require these systems to include a special power source, as they may not be efficient enough to run off of a power supply provided by a standard wall outlet (e.g. a 110V outlet, a 220V outlet, etc.). 
     As another example, Nd:YAG lasers, as well as the Ho:YAG lasers, typically implement a solid state gain medium, which may dissipate an elevated amount of energy as heat. Thus, in order to avoid damaging components of the laser ablation systems that employ these types of lasers, the systems usually must incorporate an extensive cooling system. For example, these cooling systems may include liquid cooling systems and/or secondary cooling loops. These extensive cooling systems may require additional power, be bulky and/or unwieldy, an/or provide other drawbacks. 
     Other drawbacks associated with these and other conventional systems that use lasers to ablate soft tissue exist. 
     SUMMARY 
     One aspect of the invention relates to a surgical system that ablates soft tissue. The system may include a fiber laser oscillator as the gain medium that emits electromagnetic radiation. The system may process the electromagnetic radiation, and direct the electromagnetic radiation on to the soft tissue to be ablated. Due at least in part to the nature of the electromagnetic radiation emitted by the fiber laser oscillator, the system may provide various enhancements, such as a higher power conversion efficiency, a longer lifetime, less heat dissipation, a more compact design, and/or other enhancements, for example. The system may also generate electromagnetic radiation with a relatively high beam quality. This may reduce beam divergence and beam spot size on targeted soft tissue, thereby enhancing power density in the electromagnetic radiation guided to the soft tissue. This enhanced power density may facilitate effective ablation. 
     In some embodiments of the invention, the surgical system may include a source, an output assembly, a power assembly, a cooling assembly, a processor, and/or other components. In some implementations, the source may output electromagnetic radiation at a predetermined output wavelength and a predetermined output power. The output assembly may be configured to deliver the output electromagnetic radiation to soft tissue of a patient to ablate the soft tissue. For example, output assembly may include an optical fiber. In some instances, the optical fiber may include a side-firing tip. The power assembly may receive an input power from an external power source and may, at least in part, drive source and/or other components of the surgical system with the input power. The cooling assembly may cool the source during operation. The processor may control operation of the various components of the system. 
     According to various embodiments of the invention, the source may include a generation assembly, an amplification assembly, a wavelength adjustment assembly, and/or other components or assemblies. The generation assembly may generate electromagnetic radiation at a predetermined fundamental wavelength and a predetermined fundamental power. The amplification assembly may be optically coupled with the generation assembly to receive electromagnetic radiation from the generation assembly, and may amplify the power of the received electromagnetic radiation to ensure that the electromagnetic radiation that is output from the source at the predetermined output power. The wavelength adjustment assembly may be optically coupled to the amplification assembly, and may adjust the wavelength of electromagnetic radiation received from the amplification assembly to the predetermined output wavelength. In some instances, the output wavelength may be shorter than the fundamental wavelength. 
     In some implementations, the generation assembly may include one or more pump sources, a fiber laser oscillator, an amplitude modulator, and/or other components. The pump source may provide pump energy to fiber laser oscillator. The pump energy may cause the fiber laser oscillator to lase, thereby emitting electromagnetic radiation with the fundamental wavelength. The amplitude modulator may be optically coupled to the fiber laser oscillator to receive electromagnetic radiation emitted by the fiber laser oscillator. The amplitude modulator may modulate the amplitude of the received electromagnetic radiation to provide electromagnetic radiation in pulses. The pulses of electromagnetic radiation may be provided at a predetermined frequency and/or with a predetermined pulse width. Since the amplitude modulator modulates only the amplitude of the electromagnetic radiation, electromagnetic radiation included in the pulses provided by the amplitude modulator may generally have the fundamental wavelength. The electromagnetic radiation included in the pulses created by the amplitude modulator may have the fundamental power. 
     According to various implementations, the wavelength adjustment assembly may act as a second harmonics generator by receiving electromagnetic radiation from the amplification assembly and adjusting the wavelength of the received electromagnetic radiation from the fundamental wavelength to the output wavelength. In some instances, the wavelength adjustment assembly may effectively half the wavelength (e.g., double the frequency) of the received electromagnetic radiation. 
     In some embodiments of the invention, the surgical system may process the electromagnetic radiation emitted by the fiber laser oscillator to output green electromagnetic radiation (e.g., electromagnetic radiation with a wavelength of about 540 nm). The pulses of electromagnetic radiation, as provided by the amplitude modulator may cause the output electromagnetic radiation to be output in a quasi-continuous mode. Both blood contained soft tissue and coagulated soft tissue may experience good optical absorption for green electromagnetic radiation. 
     As the fiber laser oscillator lases during the operation of the surgical system, it may produce electromagnetic radiation at a wavelength of about 1080 nm that has a relatively high beam quality (e.g., substantially single transverse mode (TEM00) radiation) with an enhanced input power to optical output power efficiency, particularly when compared with other, more conventional oscillator media (e.g., solid state gain media, etc.). This may prove useful in the context of soft tissue ablation for several reasons. 
     For instance, electromagnetic radiation with a high beam quality may enhance soft tissue ablation, so the generation of electromagnetic radiation by the fiber laser oscillator with substantially a single transverse mode and at a relatively high power conversion efficiency may enable the source to generate electromagnetic radiation that is effective in ablating soft tissue while being powered only from a standard wall outlet. This may facilitate the implementation of the surgical system for soft tissue ablation in a variety of treatment settings where more substantial power supplies may not be readily available (e.g., in a hospital, a doctors office, a patients home, etc.). 
     As another example of an enhancement provided by the use of the fiber laser oscillator, the source may not dissipate as much energy in the form of heat as with other conventional laser ablation systems. In other systems used for soft tissue ablation and employing a more standard oscillating medium, the amount of heat produced as a bi-product may require an extensive cooling system to ensure that theses systems are not damaged by the heat (e.g., they may require liquid cooling and/or a secondary cooling loop). The implementation of the fiber laser oscillator in the surgical system may enable the cooling assembly to keep the various components of the system at safe operating temperatures without employing a liquid cooling system and/or a secondary cooling loop. This may reduce the overall size and weight of the system, and therefore make the use of the system more convenient. 
     The use of the amplification assembly in conjunction with the fiber laser oscillator may further enhance the power conversion efficiency of the system in providing electromagnetic radiation for ablating soft tissue. In some implementations, the fiber laser oscillator in conjunction with the amplification assembly may convert the input power used by the power assembly to power the surgical system to optical power output to the patient in the form of electromagnetic radiation with an efficiency of greater than about 6%. In some of these implementations, the input power may be converted with an efficiency of between about 8% and about 14%. 
     These and other objects, features, benefits, and advantages of the invention will be apparent through the detailed description of the preferred embodiments and the drawings attached hereto. It is also to be understood that both the foregoing general description and the following detailed description are exemplary and not restrictive of the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a surgical system, according to one or more embodiments of the invention. 
         FIG. 2  illustrates a generation assembly, according to one or more embodiments of the invention. 
         FIG. 3  illustrates an amplification assembly, in accordance with one or more embodiments of the invention. 
         FIG. 4  illustrates a wavelength adjustment assembly, according to one or more embodiments of the invention. 
         FIG. 5  illustrates a wavelength adjustment assembly, according to one or more embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a surgical system  10  configured to ablate soft tissue of a patient, according to one or more implementations. Surgical system  10  may be particularly configured to ablate prostate tissue, or other soft tissue. In some implementations, system  10  may include a source  12 , an output assembly  14 , a power assembly  16 , a cooling assembly  18 , a processor  20 , and/or other components. In some implementations, source  12  may output electromagnetic radiation at a predetermined output wavelength and a predetermined output power. Output assembly  14  may be configured to deliver the output electromagnetic radiation to soft tissue of the patient to ablate the soft tissue. For example, output assembly  14  may include an optical fiber. In some instances, the optical fiber may include a side-firing tip. Output assembly  14  may be configured to deliver the output electromagnetic radiation to prostate tissue of the patient to ablate the prostate tissue. Power assembly  16  may receive an input power from an external power source and may, at least in part, drive source  12  and/or other components of system  10  with the input power. Cooling assembly  18  may cool source  12  during operation. Processor  20  may control operation of system  10 . 
     As is illustrated in  FIG. 1 , source  12  may include a generation assembly  22 , an amplification assembly  24 , a wavelength adjustment assembly  26 , and/or other components or assemblies. Generation assembly  22  may generate electromagnetic radiation at a predetermined fundamental wavelength and a predetermined fundamental power. Amplification assembly  24  may be optically coupled with generation assembly  22  to receive electromagnetic radiation from generation assembly  22  and may amplify the power of the received electromagnetic radiation to that the electromagnetic radiation that is output to ablate the soft tissue will be output at the predetermined output power. Wavelength adjustment assembly  26  may be optically coupled to amplification assembly  24 , and may adjust the wavelength of the received electromagnetic radiation to the predetermined output wavelength. In some instance, the output wavelength may be shorter than the fundamental wavelength. 
     In some implementations, processor  20  may execute a generation module  28 , an amplification module  30 , a cooling/temperature module  32 , a temperature tuning module  34 , and/or other modules. Although processor  20  is shown in  FIG. 1  as a single unit, it may be appreciated that processor  20  may include a plurality of processors operatively linked to each other, and that various ones of the linked processors may be physically located locally to each other, or may be remote from each other. For example, in one implementation, processor  20  may include a processor integral with the other components system  10  and a central processing unit of a host computer system being employed to control and/or read out data from system  10 . In another implementation, processor  20  may include only the processor formed integrally with the other components of system  10 . Other configurations exist. Further, each of modules  28 ,  30 ,  32 , and/or  34  may be implemented in hardware, software, firmware, or in some combination thereof. Modules  28 ,  30 ,  32 , and/or  34  may be executed locally to each other, or one or more of modules  28 ,  30 ,  32 , and/or  34  may be executed remotely from other ones of modules  28 ,  30 ,  32 , and/or  34 . 
     Generation module  28  may operate to control and receive feedback from generation assembly  22 . For instance, as will be discussed further below, generation module  28  may include one or more drivers configured to communicate with various components of generation assembly  22 . 
     Amplification module  30  may operate to control and receive feedback from amplification assembly  24 . For instance, as will be discussed further below, amplification module  30  may include one or more drivers configured to communicate with various components of amplification assembly  30 . 
     Cooling/temperature module  32  may operate to determine one or more temperature related to the operation of system  10 . For example, cooling/temperature module  32  may receive information from one or more sensors (not shown) located at source  12 , and based on this information may determine an overall temperature of source  12 , individual temperatures of one or more of assemblies  22 ,  24 , or  26 , and/or individual temperatures of one or more components of assemblies  22 ,  24 , or  26 . Further, cooling/temperature module  32  may be operate to control and/or receive feedback from cooling assembly  18 . 
     As will be discussed further below, temperature tuning module  34  may operate to tune one or more components of wavelength adjustment module  26  to an operating temperature. The tuning performed by temperature tuning module  34  may enhance the performance of wavelength adjustment assembly  26 , protect one or more of the components of wavelength adjustment assembly  26 , and/or provide other advantages. 
     Referring to  FIG. 2 , generation assembly  22  is illustrated in accordance with one or more implementations. As shown, generation assembly  22  may include one or more pump sources  36 , a fiber laser oscillator  38 , an optical isolator  40 , an amplitude modulator  42 , and/or other components. Pump source  36  may provide pump energy to fiber laser oscillator  38 . The pump energy may cause fiber laser oscillator  38  to lase, thereby emitting electromagnetic radiation with the fundamental wavelength. Amplitude modulator  42  may be optically coupled to fiber laser oscillator  38 , via optical isolator  40 , to receive electromagnetic radiation emitted by fiber laser oscillator  38 . Amplitude modulator  42  may modulate the amplitude of the received electromagnetic radiation to provide electromagnetic radiation in pulses. The pulses of electromagnetic radiation may be provided at a predetermined frequency and/or with a predetermined pulse width. Since amplitude modulator  42  modulates only the amplitude of the electromagnetic radiation, electromagnetic radiation included in the pulses provided by amplitude modulator  42  may generally have the fundamental wavelength. The electromagnetic radiation included in the pulses of amplitude modulator  42  may have the fundamental power. 
     Pump source  26  may be controlled by a pump driver executed by generation module  28  (as shown in  FIG. 1 ). Pump source  36  may include one or more diode lasers that emit electromagnetic radiation. The electromagnetic radiation emitted by the one or more diode lasers may be guided to fiber laser oscillator  38 , and may provide the pump energy requisite to lase fiber laser oscillator  38 . In some instances, the one or more diode lasers may include a plurality of broad-area laser diodes. The broad-area laser diodes may emit electromagnetic radiation with a wavelength between about 915 nm and 976 nm. In some implementations, fiber laser oscillator  38  may include a double or triple clad fiber to enable the energy from pump source  36  to be applied to fiber laser oscillator  38  as a cladding pump. It should be appreciated that alternative configurations of pump source  36  are also contemplated. 
     As fiber laser oscillator  38  lases, it may produce electromagnetic radiation at a wavelength of about 1080 nm that has a relatively high beam quality (e.g., substantially single transverse mode (TEM00) radiation) with an enhanced input power to optical output power efficiency, particularly when compared with other, more conventional oscillator media (e.g., solid state gain media, etc.). This may prove useful in the context of soft tissue ablation for several reasons. 
     For instance, electromagnetic radiation with a high beam quality may enhance soft tissue ablation, so the generation of electromagnetic radiation by fiber laser oscillator  38  with substantially a single transverse mode and at a relatively high power conversion efficiency may enable source  12  to generate electromagnetic radiation that is effective in ablating soft tissue while being powered only from a standard wall outlet via power assembly  16 . This may facilitate the implementation of system  10  for soft tissue ablation in a variety of treatment settings where more substantial power supplies may not be readily available (e.g., in a hospital, a doctors office, a patients home, etc.). 
     As another example of an enhancement provided by the use of fiber laser oscillator  38 , source  12  may not dissipate as much energy in the form of heat. In other systems used for soft tissue ablation that employ a more standard oscillating medium, the amount of heat produced as a bi-product may require an extensive cooling system to ensure that theses systems are not damaged by the dissipated heat (e.g., they may require liquid cooling and/or a secondary cooling loop). The implementation of fiber laser oscillator  38  in system  10  may enable cooling assembly  18  to keep the various components of system  10  at safe operating temperatures without employing a liquid cooling system and/or a secondary cooling loop. This may reduce the overall size and weight of system  10 , and therefore make the use of system  10  more convenient. 
     Fiber laser oscillator  38  may include a Yb-doped fiber, or other types of fiber laser oscillators, as the oscillator. The electromagnetic radiation emitted by fiber laser oscillator  38  may be near infrared. For example, the electromagnetic radiation may have a wavelength of between about 1000 nm to about 1100 nm. In some instance, fiber laser oscillator  38  may include one or more diffractive elements that narrow the linewidth of the emitted electromagnetic radiation. The linewidth of the electromagnetic radiation may be narrowed by the one or more diffractive elements to about 1080 nm. In one implementation, the one or more diffractive elements may include one or more Bragg gratings. 
     Isolator  40  may be located between fiber laser oscillator  38  and amplitude modulator  42 . Isolator  40  may protect fiber laser oscillator  38  from undesired feedback. 
     Amplitude modulator  42  may include a high frequency acousto-optical modulator and may be controlled by an amplitude modulator driver executed by generation module  28  (shown in  FIG. 1 ). As was mentioned above, amplitude modulator  42  may chop a beam of electromagnetic radiation received from fiber laser oscillator  38  into a train of pulses of electromagnetic radiation. The train of pulses may form a quasi-continuous wave beam of electromagnetic radiation that may eventually be delivered to the patient by output assembly  14 . The pulses formed by amplitude modulator  42  may have a predetermined frequency and/or a predetermined pulse width. The predetermined frequency may be between about 0.1 kHz and about 1000 kHz. In one implementation, the predetermined frequency may be between about 5 kHz and about 100 kHz. The predetermined pulse width may be between about 0.1 ns and about 100 ns. In one implementation, the predetermined pulse width may be between less than about 30 ns. Due in part to the predetermined frequency and/or predetermine pulse width, in combination with subsequent processing of the electromagnetic radiation in the pulses (e.g., by amplification assembly  24  and wavelength adjustment assembly  26 ), the electromagnetic radiation in the pulses may eventually be delivered to the patient with a predetermined pulse fluence and/or a predetermined peak power. In some instances, the predetermined pulse fluence may be between about 250 mJ/cm 2  and 1000 mJ/cm 2 . In some implementations, the predetermined peak power may be between about 50 kW and about 100 kW. 
     Turning to  FIG. 3 , amplification module  24  is illustrated, according to one or more implementations. As can be seen, amplification module  24  may form a multi-stage amplifier system. The multi-stage amplifier system may include a first amplifier  44 , an isolator  46 , a second amplifier  48 , and/or other components. First amplifier  44  may receive electromagnetic radiation at the fundamental wavelength and the fundamental power from source generation assembly  22 , and may amplify the power of the received electromagnetic radiation. Second amplifier  48  may be optically coupled to first amplifier  44 , via isolator  46 , to receive the electromagnetic radiation amplified by first amplifier  44 . Second amplifier  48  may amplify the power of the received electromagnetic radiation. In some instances (not shown), the multi-stage amplifier system may include more (e.g., three or more) amplifiers than the amount shown in  FIG. 3 . In other instances, amplification module  24  may include only a single amplification stage. 
     Isolator  46  may be located between first amplifier  44  and second amplifier  46 . Isolator  46  may protect first amplifier  44  from undesired feedback. 
     In some implementations of the invention, first and second amplifiers  44  and  48  may be formed as high-power, high-gain fiber amplifiers. In these implementations, amplifiers  44  and  48  may include large core Yb-doped fiber amplifiers. First and second amplifiers  44  and  48  may be controlled by a corresponding driver or drivers executed by amplification module  30  (as shown in  FIG. 1 ) to provide the electromagnetic radiation received from generation assembly  24  with a predetermined gain. 
     The use of amplification assembly  24  in conjunction with generation assembly  22  may further enhance the power conversion efficiency of system  10  in providing electromagnetic radiation to output assembly  14 . In some implementations, system  10  may convert the input power used by power assembly  16  to power system  10  to optical power output to the patient via output assembly  14  with an efficiency of greater than about 6%. In some of these implementations, the input power may be converted with an efficiency of between about 8% and about 14%. 
       FIG. 4  illustrates wavelength adjustment assembly  26 , in accordance with one or more implementations. In the implementation(s) of  FIG. 4 , wavelength adjustment assembly  26  may include a refractive optical element  50  and a pair of crystals  52 . Refractive optical element  50  may include a focusing lens that may concentrate electromagnetic radiation received by wavelength adjustment assembly  26  onto crystals  52 . Crystals  52  may adjust the wavelength of the received electromagnetic radiation. Wavelength adjustment assembly  26  may act as a second harmonics generator by receiving electromagnetic radiation from amplification assembly  24  and adjusting the wavelength of the received electromagnetic radiation from the fundamental wavelength to the output wavelength. In some instances, wavelength adjustment assembly  26  may effectively half the wavelength (e.g., double the frequency) of the received electromagnetic radiation. 
     Crystals  52  may include nonlinear crystals arranged in a cascading configuration. Crystals  52  may be replaced by a single crystal, provided the single crystal is made long enough. Crystals  52  may be composed of a nonlinear material such as KTP or LBO. LBO may be more resistant to heat, and thus may be more compatible with use in wavelength adjustment assembly  26 . 
     Turning to  FIG. 5 , an illustration of one or more alternate implementations of wavelength adjustment module  26  is shown. In the implementation(s) of  FIG. 5 , wavelength adjustment module  26  may perform substantially the same function as the implementation(s) described above with respect to  FIG. 4 . However, in the implementation(s) of  FIG. 5 , wavelength module  26  may include collimating optics  54 , a crystal array  56 , and/or other components. 
     Collimating optics  54  may include a positive lens  58  and a negative lens  60 . Collimating optics  54  may down collimate electromagnetic radiation received from amplification assembly  24 . Down collimating the electromagnetic radiation may enable the beam size of the electromagnetic radiation to be reduced. This reduction in beam size may enhance the efficiency of adjustment of the wavelength. 
     Crystal array  56  may include a block array of a plurality of individual crystals  58 . In some implementations, crystal array  56  may include three or more crystals. The crystals may be phase matched. For instance, the crystals may be type I or type II phase matched. The optical surfaces of the crystals may be coated with an anti-reflection coating for one or both of infrared and visible electromagnetic radiation. 
     In some implementations, the phase matched crystals in crystal array  56  may be mechanically and/or temperature tuned to meet the phase matching condition for the linewidth of the electromagnetic radiation emitted by fiber laser oscillator  38  to enhance the adjustment of the wavelength of the electromagnetic radiation (e.g., frequency doubling from near infrared to green). In some instances, this tuning may be monitored and controlled by temperature tuning module  34  (as shown in  FIG. 1 ). The conversion efficiency of wavelength adjustment module  26 , due at least in part to the temperature and/or mechanical tuning of the crystals in crystal array  56 , may be greater than about 50%. 
     Other embodiments, uses and advantages of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. The specification should be considered exemplary only, and the scope of the invention is accordingly intended to be limited only by the following claims.