Improved systems and methods for UV laser energy delivery for phototherapy.

Abstract

A system and method for UV laser energy delivery for phototherapy. A main laser generates laser light at wavelengths λ2 and λ3, where 1 / λ2 + 1 / λ3 is substantially equal to 1 / λ4, with λ4 in the UVB band. This laser light is transmitted via a fiber optic cable to a separate housing containing a UVB frequency conversion assembly. The UVB frequency conversion assembly operates to generate UVB light at wavelength λ4 from input light at wavelengths λ2 and λ3. The generated UVB light is output from a handpiece and applied to a patient.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 63 / 488,272, filed March 3, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to improved methods and systems for generating and delivering UVB laser energy for use in applications such as phototherapy. [Background technology]

[0003] Skin diseases such as atopic dermatitis, dyshidrotic eczema, eczema, lichen planus, psoriasis, and vitiligo are diseases that commonly affect large populations at some point in a person's life. Psoriasis ranges in severity from relatively mild symptoms accompanied by dryness and peeling of the affected skin to severe cases in which a very serious rash occurs over a wide area of ​​the patient's body. Even very mild psoriasis is uncomfortable and cosmetically undesirable. Severe cases are physically and psychologically debilitating and pose a very serious threat to the patient's overall health.

[0004] Although the underlying mechanisms of psoriasis are not yet fully understood, the disease involves abnormally rapid cell proliferation in the basal layer of the skin. This hyperproliferation can be reduced and the disease ameliorated by a treatment conventionally known as "phototherapy," i.e., by exposing the affected skin surface to a light source, specifically ultraviolet light. One conventional treatment is targeted phototherapy, in which a controlled dose of narrow-band ultraviolet energy at a wavelength of 308 nm is applied to specific areas of a patient's skin.

[0005] A currently used system for 308 nm narrowband ultraviolet phototherapy uses a XeCl excimer laser. This laser system is an FDA-approved medical device for the optical treatment of psoriasis, atopic dermatitis (eczema), vitiligo, and other indications. The excimer laser and associated power and cooling systems are held in an enclosure, such as a mobile cart. The laser generates 308 nm laser radiation directly by discharge in a gas chamber. The laser radiation is then guided through a flexible light guide delivery system. The light guide delivers the 308 nm laser radiation to a treatment handpiece. The handpiece is holdable by the system user and is used to apply the laser radiation to the patient. The handpiece contains internal optics to guide the 308 nm laser light received through the light guide to an output aperture. This aperture is placed directly on the patient's skin and has an aperture area (e.g., 4 cm). 2 ) to uniformly transmit laser radiation.

[0006] The portability of the delivery system is necessary to ensure consistent delivery of laser light to all affected areas of the patient using the handpiece. A typical treatment involves multiple non-adjacent areas, each with a 500cm radius. 2 Laser light may need to be applied to skin that is thicker than the laser source. The most common delivery system for transmitting 308 nm laser light from the laser source to the handpiece is optical fiber. Conventional optical fiber assemblies have solid or liquid cores and are used to transmit 308 nm beams from the laser source over lengths up to 2 m. In practice, liquid-core optical fibers achieve 65% transmission efficiency at 1.5 m and have good durability over time. Solid-core optical fibers offer an initial transmission efficiency of 80% but degrade more rapidly over time. Summary of the Invention [Problem to be solved by the invention]

[0007] To compensate for losses in the optical fiber, the power of the source laser must be significantly higher than the desired dose output. For example, a 6-W laser may be required to apply 4 W of laser energy to the patient. Requiring higher power increases the cost of the laser. Additionally, excessive wear on the optical fiber connecting the handpiece and the laser source can necessitate replacement, resulting in operational costs.

[0008] There is a need for more efficient transmission of laser radiation from the light source to the handpiece, which would allow for the use of lower power laser sources and reduce costs. It is also desirable to reduce degradation of the optical fiber, which would provide a longer-lasting transmission means by eliminating the need for frequent replacement of the optical fiber, thereby reducing system costs. [Means for solving the problem]

[0009] The methods and systems disclosed herein provide these and other advantages by more efficiently delivering, for example, 308 nm UVB laser radiation to a treatment handpiece. Conventional UVB solid-state laser systems include a low-frequency primary laser and one or more frequency conversion stages to shift the initial low-frequency laser light to the desired UVB wavelength. The methods and systems of the present invention physically separate the intermediate frequency conversion stage from the final conversion stage. This advantageously allows for the construction of a system in which the high-frequency UVB light used for treatment does not need to be transmitted to the handpiece through a light guide. The laser generates intermediate laser light, such as visible or near-infrared (NIR) light. This intermediate light is transmitted to the handpiece via one or more fiber optic cables. The final conversion of the low-frequency laser radiation to high-frequency UV light occurs within the handpiece, for example, via a frequency conversion crystal.

[0010] Fiber optic cables provide an efficient and flexible transmission system that facilitates the delivery of low-frequency laser radiation to the handpiece, offering lower transmission losses and a higher threshold for laser-induced damage compared to conventional systems that use optical fiber to deliver 308 nm radiation to the handpiece. Low-frequency radiation is transmitted very efficiently through optical fiber. This allows the use of lower-power lasers, reducing costs. Existing highly efficient optical fibers optimized for transmitting visible and NIR light over long distances can be used. Efficient transmission significantly reduces, and in some cases virtually eliminates, the need to replace optical fiber due to degradation from absorbed laser radiation. Longer lifespans of fiber optic components can reduce operational costs.

[0011] In one embodiment, the phototherapy treatment system includes a main laser that outputs laser light at wavelengths λ2 and λ3, where 1 / λ2 + 1 / λ3 is substantially equal to 1 / λ4, and λ4 is in the UVB band between 304 nm and 312 nm, particularly about 308 nm. A housing separate from the main laser includes a UVB frequency conversion assembly that generates UVB light at wavelength λ4 from input light at wavelengths λ2 and λ3. A first fiber optic cable optically connects the main laser to the housing.

[0012] In one embodiment, the main laser comprises a primary laser that generates light having wavelength λ1, and an intermediate frequency conversion assembly that generates light of wavelengths λ2 and λ3 from the light of wavelength λ1.

[0013] The laser light of wavelengths λ2 and λ3 from the main laser may be transmitted to the housing by a single optical fiber, or each wavelength may be transmitted by a separate optical fiber.

[0014] The housing containing the UVB frequency conversion assembly may be a handpiece usable for applying the generated UVB light to a patient's skin. Alternatively, the housing may be separate from the handpiece and connected to the handpiece via a second fiber optic cable that transmits the UVB light from the housing to the handpiece. The second fiber optic cable may have a length that is substantially shorter than the length of the first fiber optic cable.

[0015] A method for generating UVB light for phototherapy treatment, such as 308 nm light, includes connecting a main laser to a remote housing using a fiber optic cable. The main laser generates laser light having wavelengths λ2 and λ3. 1 / λ2 + 1 / λ3 is substantially equal to 1 / λ4, where λ4 is in the UVB band of 304 nm to 312 nm. A UVB frequency conversion assembly in the housing is used to convert the laser light having wavelengths λ2 and λ3 from the main laser to UVB light having wavelength λ4. The light having wavelengths λ2 and λ3 is obtained by using a primary laser to generate light having wavelength λ1 and using an intermediate frequency conversion assembly to generate light having wavelengths λ2 and λ3 from the light having wavelength λ1.

[0016] The housing may contain a treatment handpiece, or the treatment handpiece may be optically coupled to the housing using a second fiber optic cable. The UVB light generated by the UVB frequency conversion is emitted from an opening in the handpiece. The UVB light emitted from the opening is applied to the patient.

[0017] Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic diagram of a system for delivering UV laser radiation to a patient. [Figure 2] FIG. 2 illustrates an embodiment of the handpiece of FIG. 1 with a single fiber delivery configuration. [Figure 3] FIG. 3 illustrates an embodiment of the handpiece of FIG. 1 with a dual fiber delivery configuration. [Figure 4] FIG. 4 shows an alternative embodiment in which the UVB frequency converter is housed separately from the handpiece. DETAILED DESCRIPTION OF THE INVENTION

[0019] 1 is a schematic diagram of a system 100 for delivering UVB laser radiation to a patient in a phototherapy treatment. In one embodiment, the UVB laser radiation is substantially in the UVB band at 308 nm. The UVB radiation is delivered to the patient via a suitable handpiece to treat various skin conditions.

[0020] Referring to FIG. 1 , system 100 includes a main laser system 105 and a handpiece 110. Main laser system 105 includes a primary laser 115. Primary laser 115 generally provides the highest laser power level. For example, laser 115 is a high-power, electrically efficient diode laser that outputs light at wavelength λ1. In one embodiment, laser 115 is a solid-state laser. However, other laser sources, such as gas lasers, may also be used. Radiation from primary laser 115 at an initial wavelength λ1 is directed to an intermediate frequency conversion assembly 120. Intermediate frequency conversion assembly 120 operates to convert the input laser radiation from the initial wavelength λ1 to one or more intermediate wavelengths (e.g., λ2 and λ3).

[0021] Frequency conversion in the intermediate frequency conversion assembly 120 can be performed using various techniques, and the conversion may include one or more intermediate frequency conversion stages. In one embodiment, the primary laser 115 is used to pump the secondary laser in the intermediate frequency conversion assembly 120. The secondary laser may include a laser crystal (e.g., Nd:YAG), one or more tunable lasers (e.g., titanium sapphire), a high-power fiber amplifier (e.g., Yb- or Er-doped silicate) with a low-power seed laser input, or other configurations known to those skilled in the art. The output of the secondary laser is directed to one or more additional conversion stages, as needed, to generate the intermediate wavelengths λ2 and λ3. In one embodiment, a nonlinear optical crystal (e.g., LBO) is used to generate the intermediate wavelengths by harmonic generation or sum-frequency generation of the intermediate wavelength radiation.

[0022] The intermediate wavelength laser radiation generated by the intermediate frequency conversion assembly 120 is guided to the UVB frequency conversion assembly 125 via a light guide. In one embodiment, the light guide includes a flexible fiber optic cable 130. The fiber optic cable 130 is coupled to the intermediate frequency conversion assembly 120 and the UVB frequency conversion assembly 125 using fiber optic couplers 135a and 135b, respectively. The UVB frequency conversion assembly 125 operates to generate high-frequency light at wavelength λ4 from the laser radiation at intermediate wavelengths λ2 and λ3. In one embodiment, λ4 is in the UVB band between 304 nm and 312 nm. In a further embodiment, λ4 is substantially 308 nm. In one embodiment, the UVB frequency conversion assembly is integrated into the handpiece 110. The fiber optic couplers 135a and 135b to the laser system may be permanent or may include a quick-disconnect mechanism that allows for easy disassembly / reassembly and replacement (e.g., replacement of the fiber optic cable 130 or the handpiece 110).

[0023] The UVB frequency conversion assembly may include a nonlinear crystal to generate the desired therapeutic wavelength λ4 by harmonic or sum frequency generation. The remaining intermediate wavelength light in the final beam is substantially removed using a dichroic mirror (DM) 140, which is then directed, for example, to an absorptive heat sink (HS) 145 or elsewhere. The dichroic mirror 140 may be integrated into the handpiece 110. For example, therapeutic radiation at λ4, 308 nm, may be directed to the output aperture by optical structures as needed. The intermediate wavelength light generated by the main laser 105 and transmitted by the optical fiber 130 is in the visible to near-infrared (NIR) wavelength range. This allows the use of conventional optical fibers, such as data transmission optical fibers, designed to transmit light in this wavelength range over very long distances without loss. Visible and NIR wavelengths exhibit excellent transmission characteristics, at 99.5% over 1.5 m through solid-core fibers such as quartz. Compared to optical fibers that transmit UV light, intermediate wavelength energy is less absorbed in the fiber, thereby reducing the possibility of laser-induced damage in the optical fiber.

[0024] The intermediate frequency conversion assembly 120 may be configured to generate two wavelengths, λ2 and λ3, where 1 / λ2 + 1 / λ3 is substantially equal to 1 / λ4, where λ4 is the target wavelength, e.g., 308 nm (±0.5 nm). A configuration where λ2 = λ3, i.e., frequency doubling, may also be used.

[0025] A specific example embodiment of an intermediate frequency conversion assembly 120 that can be used in the main laser system 105 and details of the functionality implemented in the UVB frequency conversion assembly 125 are set forth below. (A) Intracavity upconverting optical parametric oscillator (OPO): A 1064 nm Nd:YAG laser is frequency doubled to produce 532 nm (λ2) light, which serves as the pump light for the OPO. The OPO is tuned to oscillate at 731.5 nm (λ3). The remaining 532 nm and 731.5 nm light is transmitted through optical fiber 130 and sum-frequency mixed in the second conversion assembly 125 to produce 308 nm light. (B) A frequency-doubled Nd:YAG laser pumps a Ti:sapphire laser, which is tuned to oscillate at 924 nm (λ2) and frequency-doubled to 462 nm (λ3). The remaining 924 nm and 462 nm light is transmitted by optical fiber 130 and sum-frequency mixed in second conversion assembly 125 to produce 308 nm light. (C) 1232 nm pulsed fiber laser source based on Raman conversion Yb-doped fiber: 1232 nm light is frequency doubled to 616 nm (λ2 = λ3), which is transmitted through optical fiber 130 and further frequency doubled in a second conversion assembly to produce 308 nm light. (D) 1030 nm and 1535 nm MOPA (Master Oscillator Power Amplifier) ​​lasers: These are based on Yb-doped and Er-doped fiber amplifiers and are frequency doubled to 515 nm (λ2) and 768 nm (λ3), respectively. These wavelengths are transmitted by optical fiber 130 and sum-frequency mixed in the second conversion assembly 125 to 308 nm.

[0026] The multiple wavelengths (e.g., λ2 and λ3) generated by the intermediate frequency conversion assembly 120 are transmitted to the second conversion assembly 125 via a single or multiple optical fibers. In embodiments using a single optical fiber, the intermediate wavelengths are combined, such as by a dichroic mirror, and then focused into a single optical fiber. After exiting the fiber, the combined beam is focused onto a nonlinear crystal within the UVB frequency conversion assembly 125. In embodiments using multiple fibers, each intermediate wavelength, such as λ2 and λ3, is focused onto a respective optical fiber. After entering the second conversion assembly 125, the beams are combined, such as by a dichroic mirror, and then focused onto a nonlinear crystal.

[0027] The choice of whether to use a single or dual fiber system in one embodiment is based on a variety of factors. Using a single fiber cable for both wavelengths allows the coupling optics to be located in the main laser 105 and not required as part of the UVB frequency conversion assembly 125. In configurations where the UVB frequency conversion assembly 125 is integrated into the handpiece 110, using a single cable reduces the size of the handpiece and makes it easier for the user to handle. Using separate fiber cables allows each fiber to be optimized for each wavelength being transmitted, allowing for the selection of appropriate fiber core substrates. Using separate cables also reduces heat absorption per cable. However, dual fiber systems may be more costly than single fiber systems. Furthermore, coupling optics are required in the UVB frequency conversion assembly 125 to combine the light from each fiber. In configurations where the UVB frequency conversion assembly 125 is integrated into the handpiece 110, this additional element can increase the size and cost of the handpiece 110.

[0028] Conventional solid-core optical fibers exhibit very high efficiency for visible and NIR light. In embodiments where it is desired to maximize the generation efficiency into the UVB band at the nonlinear crystal of the UVB frequency conversion assembly 125, the intermediate wavelength single-mode beam profile should be maintained as much as possible within the fiber. A single-mode Gaussian profile provides optimal light collection, thus resulting in higher peak power and conversion efficiency at the nonlinear crystal. Due to the short propagation length (e.g., approximately 2 m or less), standard step-index fiber may be used, which reduces profile degradation.

[0029] However, in some embodiments, single-mode or graded-index fibers may be preferred. Single-mode fibers have good profile-retention characteristics but small diameters of approximately ±10 μm. This limits the optical power they can transmit and can generate significant heat, necessitating the use of thermal management systems. Graded-index fibers can also maintain a near-Gaussian profile. They generally have larger diameters than single-mode fibers, allowing for higher power transmission. Their larger input and output facets compared to single-mode fibers also provide a higher tolerance to laser-induced damage and allow the use of anti-reflection coatings. Due to the large power transmitted (which can reach up to 18 W), thermal management is still required to prevent fiber damage. Thermal management involves using flexible solid, liquid, or paste-like materials with high thermal conductivity and / or high heat capacity surrounding and in contact with the optical fiber.

[0030] A specific embodiment of the system 100 is described below.

[0031] The primary laser 115 is a 976 nm (λ1) diode laser. The first conversion assembly 120 contains two low-power seed lasers, outputting 1535 nm and 1030 nm, respectively. The 1535 nm seed laser output is amplified by multiple stages of Er-doped fiber amplifiers, and the 1030 nm seed laser output is amplified by multiple stages of Yb-doped fiber amplifiers. Both fiber amplifiers are pumped by the primary laser 115. The amplified outputs are second-harmonic converted to 768 nm (λ2) and 515 nm (λ3), respectively, and a dichroic mirror filters out the seed laser wavelength. These intermediate wavelengths, 768 nm (λ2) and 515 nm (λ3), can be combined in the main laser system 105 and transmitted via a single optical fiber to the assembly 125 in the handpiece 110, or they can be transmitted separately via two optical fibers and combined in the second conversion assembly 125 in the handpiece.

[0032] FIG. 2 shows one embodiment of a handpiece 200 having a single fiber delivery configuration.

[0033] The intermediate wavelengths λ2 and λ3 are transmitted to the handpiece 200 via a single fiber 205. The fiber 205 may be connected to the handpiece 200 via a fiber coupling 210. The fiber 205 is fixedly coupled to an optical platform 215 within the handpiece 200. The input beam 220 is captured by a lens L1 and refocused onto a nonlinear crystal (NLC) 225. The NLC 225 produces a sum-frequency-generated output beam 230, e.g., at 308 nm, containing the residual intermediate wavelengths λ2 and λ3. The beam 230 is focused and collimated by a lens L2. The intermediate wavelengths λ2 and λ3 are removed from the beam 230 by a dichroic mirror DM1 (235). The residual intermediate wavelengths are reflected by DM1 and directed toward an absorptive heat sink 240, such as a thick aluminum wall coated with black light-absorbing paint. The heat generated is absorbed by the aluminum and dissipated to the surroundings. UVB light beam 245 passes through DM1 (235) and is directed to diverging lens L3. Beam 245 enters conduit 250, which has walls 255 with suitable UVB-reflective surfaces on the interior surfaces and an opening 260 at the opposite end. Conduit 250 may be square in cross section and have UVB-reflective mirrors on all four interior walls. The central beam and the reflected edges form a relatively uniform profile at the aperture.

[0034] FIG. 3 shows one embodiment of a handpiece 300 having a dual fiber delivery configuration.

[0035] The intermediate wavelengths λ2 and λ3 are transmitted to the handpiece by separate fibers 305a and 305b. Both optical fibers 305a and 305b are connected to the handpiece 300 by respective fiber couplers 310a and 310b. Fibers 305a and 305b are fixedly coupled to the optical platform 315 in the handpiece 300. The input beams carrying wavelengths λ2 and λ3 are captured and collimated by lenses L4 and L5, respectively. The λ3 beam is reflected by mirror 320 and directed to dichroic mirror 325, which reflects the λ3 light and transmits the λ2 light, combining the λ3 and λ2 beams. Lens L6 focuses the combined beam onto the NLC 225. The NLC 225 and subsequent optical processing in the handpiece 300 of FIG. 3 are similar to the single fiber approach in the handpiece 200 of FIG.

[0036] In a representative embodiment of a single or multiple fiber configuration, the optical lenses and mirrors are typically about 12.5 mm in diameter. The NLC is typically about 3 mm x 3 mm x 35 mm and may be housed in a small oven (not shown) to maintain a constant temperature. The output conduit, through which the 308 nm UVB output beam diverges, is about 7.5 cm long and has an aperture of about 2 cm x 2 cm. The representative sizes disclosed herein are by way of example, and components in a particular embodiment may be larger or smaller in size.

[0037] This output conduit may be specially configured to closely resemble that produced by existing handpiece designs in which a beam generated by a XeCl excimer laser exits the light guide of the Xtrac phototherapy system (manufactured by Strata Skin Sciences, Inc.) Various aspects of such a handpiece design are disclosed in U.S. Patent No. 11,471,695, the entire contents of which are incorporated herein by reference.

[0038] In the above-described embodiments, the components of the UVB frequency conversion assembly are illustrated as being housed within the housing of the hand piece. In an alternative embodiment 400, referring to FIG. 4 , the UVB frequency conversion assembly 125, which receives light at wavelengths λ2 and λ3 and generates UVB therapeutic radiation, is housed in a housing 405 separate from the hand piece 410. The light at wavelengths λ2 and λ3 generated and output by the main laser system 105 is supplied to the UVB frequency conversion assembly by fiber optic cable 130. A second fiber optic cable 415 transmits the UVB radiation generated by the UVB frequency conversion assembly from the housing 400 to the hand piece 410.

[0039] This alternative embodiment allows for the use of conventional handpieces that require an external UVB therapeutic radiation source while still enjoying most of the benefits provided by the embodiment with the UVB frequency conversion assembly 125 within the handpiece. The second fiber optic cable 410 can be substantially shorter than the main fiber optic cable 130. For example, if the main fiber optic cable 130 is 1.5 m or 2 m long, the second fiber optic cable 410 may have a length of 10 cm to 30 cm or 5 cm to 50 cm. Because energy absorption within the second cable 410 is relatively low due to its short length, overall UVB power loss is insignificant. The second cable 410 may deteriorate over time, but if replacement is necessary, the cost will be lower than replacing the longer main cable 130. The housing 400 housing the UVB frequency conversion assembly may be wearable, such as on the waist or arm of the person operating the handpiece, so as not to interfere with operation of the handpiece.

[0040] Although the present system is described in the context of generating UVB band light, for example, substantially at 308 nm, to provide UV phototherapy treatment, the improved system and method can also be used to improve the efficiency of other systems in which high frequency laser energy is currently transmitted within optical fiber, where the length and configuration of the optical fiber results in significant energy losses.

[0041] Various aspects, embodiments, and examples of the present invention are disclosed and described herein, and modifications, additions, and variations may be made by those skilled in the art without departing from the spirit and scope of the invention, as defined in the appended claims.

Claims

1. 1. A phototherapy treatment system comprising: wavelength λ 2 and λ 3 A main laser that outputs laser light of 1 / λ 2 +1 / λ 3 is substantially 1 / λ 4 is equal to λ 4 a main laser having a wavelength in the UVB band of 304 nm to 312 nm; The wavelength λ 2 and λ 3 from the input light of wavelength λ 4 a housing having a UVB frequency conversion assembly therein operative to generate UVB light of a first optical fiber cable optically connecting the main laser and the housing and configured to transmit the laser light from the main laser to the housing; A phototherapy treatment system comprising:

2. the housing includes a handpiece configured to emit the UVB light generated by the UVB frequency conversion assembly through an opening in the handpiece; The system of claim 1 , wherein the emitted UVB light is applied to the patient's skin.

3. the first fiber optic cable has a first end and a second end; the main laser includes a first optical fiber coupler, the first end of the optical fiber cable is connected to the first coupler; The system of claim 2 , wherein the handpiece includes a second fiber optic coupler, and the second end of the fiber optic cable is connected to the second coupler.

4. a handpiece separate from the housing, the handpiece being coupled to the housing by a second fiber optic cable; the second fiber optic cable operates to transmit UVB light generated by the UVB frequency conversion assembly from the housing to the handpiece; the handpiece is configured to emit the UVB light through an opening in the handpiece; The system of claim 1 , wherein the emitted UVB light is applied to the patient's skin.

5. The system of claim 4 , wherein the length of the second fiber optic cable is substantially less than the length of the first fiber optic cable.

6. The system of claim 4 , wherein the housing is wearable.

7. The main laser is wavelength λ 1 a primary laser generating light having a The wavelength λ 1 from the light of wavelength λ 2 and λ 3 an intermediate frequency conversion assembly operative to generate light of The system of claim 1 , comprising:

8. The main laser has the wavelength λ 2 and the wavelength λ 3 outputting the laser light as separate beams, The first optical fiber cable comprises: a laser beam having a wavelength λ 2 a first fiber for transmitting the laser light; a laser beam having a wavelength λ 3 a second fiber for transmitting the laser light; Including, The UVB frequency conversion assembly converts the wavelength λ received through the first fiber 2 and the laser light of wavelength λ received through the second fiber. 3 10. The system of claim 1, further comprising a coupling optical system for coupling the laser light from the first laser beam to the second laser beam.

9. The wavelength λ 4 The system of claim 1 , wherein is substantially 308 nm.

10. The system of claim 1 , wherein the first fiber optic cable has a length of at least 1 meter.

11. 1. A method for producing UVB light for phototherapy treatment, comprising: connecting the main laser to a separate housing using a fiber optic cable; The main laser is used to generate a wavelength λ 2 and λ 3 generating a laser beam of 1 / λ 2 +1 / λ 3 is substantially 1 / λ 4 is equal to λ 4 is in the UVB band of 304 nm to 312 nm; A UVB frequency conversion assembly within the housing is used to convert the wavelength λ from the main laser. 2 and λ 3 Laser light with wavelength λ 4 into UVB light; 10. A method for generating UVB light for phototherapy treatment, comprising:

12. the housing includes a handpiece having an opening; The method of claim 11 , further comprising emitting the UVB light produced by UVB frequency conversion through the aperture.

13. further comprising optically coupling a handpiece having an aperture to the housing using a second fiber optic cable; 12. The method of claim 11, wherein the UVB light generated within the housing is transmitted by the second fiber optic cable to the handpiece and emitted from an opening in the handpiece.

14. 14. The method of claim 12 or 13, further comprising applying the UVB light emitted from the opening of the handpiece to a patient.

15. The main laser is used to generate a wavelength λ 2 and λ 3 The step of generating the laser light includes: Using a primary laser, wavelength λ 1 generating light having a Using an intermediate frequency conversion assembly, 1 from light of wavelength λ 2 and λ 3 generating light of The method of claim 11 , comprising:

16. The wavelength λ generated by the main laser 2 and the wavelength λ 3 the laser light is transmitted through separate fibers in a first fiber optic cable; The wavelength λ 2 and the wavelength λ 3 12. The method of claim 11, further comprising the step of: coupling light from the first light source to the second light source;

17. The wavelength λ 4 The method of claim 11 , wherein is substantially 308 nm.

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