阅读说明：本技术 一种用于提高三次谐波产生效率的激光设备 (Laser equipment for improving generation efficiency of third harmonic ) 是由 尹雨松 于 2019-10-16 设计创作，主要内容包括：本发明公开了一种用于提高三次谐波产生效率的激光设备,包括光学腔、基波束产生一级加强装置、可调节反射镜、多重波反射加强输出装置和三次谐波加强反射装置,所述基波束产生一级加强装置、可调节反射镜、多重波反射加强输出装置和三次谐波加强反射装置设于光学腔内,所述基波束产生一级加强装置和可调节反射镜水平中轴线设于同一水平公共轴一上,所述可调节反射镜可调节自身角度,所述多重波反射加强输出装置设于可调节反射镜整下方,所述三次谐波加强反射装置和多重波反射加强输出装置水平中轴线设于同一水平公共轴二上。本发明属于激光技术领域,具体是指一种光转换效率高、三次谐波输出稳定性高的激光设备。(The invention discloses laser equipment for improving the generation efficiency of third harmonic, which comprises an optical cavity, a first-stage reinforcing device for generating a fundamental wave beam, an adjustable reflector, a multiple-wave reflection reinforcing output device and a third-harmonic reflection reinforcing device, wherein the first-stage reinforcing device for generating the fundamental wave beam, the adjustable reflector, the multiple-wave reflection reinforcing output device and the third-harmonic reflection reinforcing reflection device are arranged in the optical cavity, the first-stage reinforcing device for generating the fundamental wave beam and the horizontal central axis of the adjustable reflector are arranged on a same horizontal common axis I, the adjustable reflector can adjust the angle per se, the multiple-wave reflection reinforcing output device is arranged below the adjustable reflector, and the horizontal central axes of the third-harmonic reflection reinforcing reflection device and the multiple-wave reflection reinforcing output device are arranged on a same horizontal common axis II. The invention belongs to the technical field of laser, and particularly relates to laser equipment with high light conversion efficiency and high third harmonic output stability.)

1. A laser apparatus for improving third harmonic generation efficiency, characterized in that: comprises an optical cavity, a first-stage reinforcing device for generating fundamental wave beams, an adjustable reflector, a multi-wave reflection reinforcing output device and a third-harmonic reinforcing reflection device, the fundamental wave beam generation primary reinforcing device, the adjustable reflector, the multiple wave reflection reinforcing output device and the third harmonic wave reinforcing reflection device are arranged in the optical cavity, the fundamental wave beam generation primary strengthening device and the adjustable reflector are sequentially arranged along the horizontal direction, the fundamental wave beam generation primary strengthening device and the adjustable reflector horizontal central axis are arranged on the same horizontal common axis, the adjustable reflector can adjust the self angle, the multiple wave reflection enhancing output device is arranged right below the adjustable reflector, the third harmonic wave reinforced reflection device and the multiple wave reflection reinforced output device are sequentially arranged in the horizontal direction, the third harmonic wave reinforced reflection device and the multiple wave reflection reinforced output device are arranged on the same horizontal common shaft II along the horizontal central axis; the fundamental wave beam generation primary reinforcing device comprises a laser medium, a laser pump, a first fundamental frequency high reflector, a Q switch, a spherical lens and a cylindrical lens, wherein the laser medium, the laser pump, the first fundamental frequency high reflector, the Q switch, the spherical lens, the cylindrical lens and an adjustable reflector are sequentially arranged along the horizontal direction; the third harmonic enhanced reflection device comprises a light beam high reflection lens, an I-type nonlinear second harmonic crystal and an II-type nonlinear third harmonic crystal, wherein the multiple wave high reflection lens, the light beam high reflection lens, the I-type nonlinear second harmonic crystal and the II-type nonlinear third harmonic crystal are sequentially arranged along the horizontal direction, the horizontal central axes of the light beam high reflection lens, the I-type nonlinear second harmonic crystal, the II-type nonlinear third harmonic crystal and the multiple wave high reflection lens are arranged on the same horizontal common axis II, the I-type nonlinear second harmonic crystal is used for generating second harmonics, the II-type nonlinear third harmonic crystal is used for generating third harmonics, and the light beam high reflection lens is a high reflection lens of fundamental frequency and second harmonic frequency spectrum.

2. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: output device is strengthened in multiple wave reflection includes prism one, prism two, direction lens and second harmonic transmitter, one side that adjustable speculum is close to the laser pump is located to the slope that connects with two apex angles of prism one, the oblique top of prism two is located to prism one, directly over the prism is located to the direction lens, one side of adjustable reflector principle laser pump is located to the second harmonic generator, the second harmonic transmitter is located between adjustable speculum and the direction lens, prism two is located on same water flat line with the nonlinear third harmonic crystal of II type.

3. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the third harmonic enhanced reflection device comprises a light beam high reflection lens, an I-type nonlinear second harmonic crystal, an II-type nonlinear third harmonic crystal and a wave plate, wherein the light beam high reflection lens, the I-type nonlinear second harmonic crystal, the II-type nonlinear third harmonic crystal and the wave plate are sequentially arranged along the horizontal direction, the horizontal central axis of the light beam high reflection lens, the I-type nonlinear second harmonic crystal, the II-type nonlinear third harmonic crystal and the wave plate is arranged on the same horizontal common axis II, and the wave plate is arranged between the II-type nonlinear third harmonic crystal and the multi-wave high reflection lens.

4. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the triple harmonic enhanced reflection device comprises a light beam high reflection lens, an I-type doubling crystal, an I-type triple frequency crystal and a wave plate, wherein the light beam high reflection lens, the I-type doubling crystal, the wave plate and the I-type triple frequency crystal are sequentially arranged along the horizontal direction, the horizontal central axes of the light beam high reflection lens, the I-type doubling crystal, the wave plate and the I-type triple frequency crystal are arranged on the same horizontal common axis II, and the wave plate is arranged between the I-type triple frequency crystal and the I-type doubling crystal.

5. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the cylindrical lens has the thermal lens characteristic of a compensation crystal, the spherical lens is used for adjusting the spot size of a light beam, and the first fundamental frequency high reflector is a high reflector of the fundamental frequency of the laser medium.

6. A laser device for improving third harmonic generation efficiency according to claim 2, characterized in that: the first prism and the second prism are a first fused siliconized prism and a second fused siliconized prism which are gradually changed in the UV.

7. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the adjustable reflector is a folding lens.

8. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the multi-wave high-reflection lens is a dichroic mirror.

9. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the I-type nonlinear second harmonic crystal is an I-type LBO crystal.

10. A laser device for improving third harmonic generation efficiency according to claim 1, characterized in that: the II type nonlinear third harmonic crystal is II type lithium triborate crystal.

Technical Field

The invention belongs to the technical field of laser, and particularly relates to laser equipment for improving the generation efficiency of third harmonic.

Background

The common third harmonic solid laser is produced outside the laser resonant cavity, one infrared laser is used as light source, the output infrared laser is used as fundamental wave and is injected into the frequency doubling non-linear crystal to produce second harmonic light, and the frequency doubling light and unconverted third harmonic light are obtainedThe fundamental wave light is acted on the third harmonic nonlinear crystal together to mix frequency to generate the output of frequency tripling laser, although the third harmonic light generated by the device is easy to debug, because the incident fundamental wave power is low, the output coupling ratio of the infrared laser generation technology is about 20 percent, and the harmonic efficiency is in direct proportion to the square of the incident fundamental wave power, the conversion efficiency is limited by the harmonic outside the cavity, in order to improve the conversion efficiency of the harmonic outside the cavity, the lens focusing is usually adopted to enhance the power density of the fundamental wave, but the gathered light beam can cause the damage of the optical anti-reflection film layer on the surface of the nonlinear crystal and the crystal, thereby the total output power of the harmonic is limited, the frequency mixing outside the cavity is a single-pass behavior, namely the fundamental wave and the second harmonic pass through the frequency tripling crystal once, the fundamental wave and the second harmonic light which are not converted into the third harmonic are all wasted, so that the third harmonic solid laser, for high power lasers, the typical efficiency is limited to less than 25% of the total conversion efficiency, since the unconverted fundamental and second harmonic beams are wasted in the structure, even though very high power pulses Nd: YAG laser, the total conversion efficiency is lower than 25%; the theory behind intracavity second harmonic generation has been elucidated, with the crystal medium producing the second harmonic of the incident radiation frequency, the tensor d in the lowest order nonlinear polarization term, only if the crystal lacks inversion symmetry to polarize the second order^ijDoes not disappear, if the crystal has inverted symmetry, the lowest order nonlinear polarization contribution is cubic in the electric field strength, and the crystal will produce only third or higher harmonics of the initial frequency.

Disclosure of Invention

In order to solve the existing problems, the invention provides a laser device with high light conversion efficiency and high third harmonic output stability.

The technical scheme adopted by the invention is as follows: a laser device for improving the generation efficiency of third harmonic wave comprises an optical cavity, a primary reinforcing device for generating a base beam, an adjustable reflector, a multi-wave reflection reinforcing output device and a third harmonic wave reinforcing reflection device, wherein the primary reinforcing device for generating the base beam, the adjustable reflector, the multi-wave reflection reinforcing output device and the third harmonic wave reinforcing reflection device are arranged in the optical cavity; the primary reinforcing device for generating the base beam and the adjustable reflector are sequentially arranged in the horizontal direction, the primary reinforcing device for generating the base beam and the horizontal central axis of the adjustable reflector are arranged on the same horizontal common axis, the primary reinforcing device for generating the base beam is used for simultaneously reflecting and reinforcing the base beam, the reinforced base beam reaches the adjustable reflector, the angle of the adjustable reflector can be adjusted, the adjustable reflector reflects the reinforced base beam and is optionally a high-reflection device for second harmonic frequency, the high-reflection device and the base beam from the primary reinforcing device generate optical output oscillation of the base beam, the downward reflection in the vertical direction can be realized according to the different angles of the adjustable reflector, the downward reflection in the vertical direction can also be realized, and the multi-wave reflection reinforcing output device is arranged under the adjustable reflector, the third harmonic enhanced reflection device and the multiple wave reflection enhanced output device are sequentially arranged in the horizontal direction, the horizontal central axes of the third harmonic enhanced reflection device and the multiple wave reflection enhanced output device are arranged on the same horizontal common axis II, the multiple wave reflection enhanced output device is provided with a high reflection device for pre-selecting high transmission light beams of fundamental frequency and third harmonic frequency light beams and is also a high reflection device for second harmonic wavelength light beams, and the third harmonic enhanced reflection device is used for high reflection of fundamental frequency and second harmonic frequency spectrums and simultaneously generating third harmonic; the primary reinforcing device for generating the base beam comprises a laser medium, a laser pump, a first fundamental frequency high reflector, a Q switch, a spherical lens and a cylindrical lens, wherein the laser medium, the laser pump, the first fundamental frequency high reflector, the Q switch, the spherical lens, the cylindrical lens and an adjustable reflector are sequentially arranged along the horizontal direction, the laser medium, the laser pump, the first fundamental frequency high reflector, the Q switch, the spherical lens, the cylindrical lens and the horizontal central axis of the adjustable reflector are arranged on the same horizontal common shaft I, the laser medium is used for providing laser materials, the laser medium is YLF, YAG, YVO4 and the like, the laser pump is used for exciting the laser medium, the laser pump can be a lamp pump, a laser diode and the like, the first fundamental frequency high reflector selects the laser medium to generate laser beams along the common shaft I with a preselected fundamental frequency, and the spherical lens and the cylindrical lens are particularly provided with Nd: a YLF crystal that, in the Q-switch option, suppresses the laser by introducing losses in the resonator while pumping and storing energy in atomic population inversion that will reduce the cavity losses once the required inversion is achieved to allow laser emission, in which mode a large pulse train output can be generated from the laser, the multiple reflection enhanced output device being a multiple wave highly reflective mirror that is placed under an adjustable mirror, the multiple wave highly reflective mirror providing adjustable mirror optical round-trip, and high reflection of the high transmitted beam for the preselected fundamental and third harmonic beams simultaneously for high reflection of the second harmonic wavelength beam; the third harmonic enhanced reflection device comprises a light beam high reflection lens, an I-type nonlinear second harmonic crystal and an II-type nonlinear third harmonic crystal, wherein the multiple wave high reflection lens, the light beam high reflection lens, the I-type nonlinear second harmonic crystal and the II-type nonlinear third harmonic crystal are sequentially arranged along the horizontal direction, the horizontal central axes of the light beam high reflection lens, the I-type nonlinear second harmonic crystal, the II-type nonlinear third harmonic crystal and the multiple wave high reflection lens are arranged on the same horizontal common axis II, the I-type nonlinear second harmonic crystal is used for generating second harmonics, the II-type nonlinear third harmonic crystal is used for generating third harmonics, the light beam high reflection lens is a high reflection lens with fundamental frequency and second harmonic frequency spectrums, and the first high reflection lens and the light beam high reflection lens are used for limiting an optical cavity.

Further, output device is strengthened in multiple wave reflection includes prism one, prism two, direction lens and second harmonic transmitter, one and two apex angles of prism meet the slope and locate one side that adjustable speculum is close to the laser pump, the oblique top of prism two is located to prism one, the direction lens is located directly over the prism one, one side of adjustable reflector principle laser pump is located to the second harmonic generator, the second harmonic transmitter is located between adjustable speculum and the direction lens, prism two and II type nonlinear third harmonic crystal locate on same water flat line.

Furthermore, the third harmonic enhanced reflection device comprises a light beam high reflection lens, an I-type nonlinear second harmonic crystal, an II-type nonlinear third harmonic crystal and a wave plate, wherein the light beam high reflection lens, the I-type nonlinear second harmonic crystal, the II-type nonlinear third harmonic crystal and the wave plate are sequentially arranged along the horizontal direction, the horizontal central axes of the light beam high reflection lens, the I-type nonlinear second harmonic crystal, the II-type nonlinear third harmonic crystal and the wave plate are arranged on the same horizontal common axis II, and the wave plate is arranged between the II-type nonlinear third harmonic crystal and the multi-wave high reflection lens.

Furthermore, the third harmonic enhanced reflection device comprises a light beam high reflection lens, an I-type doubling crystal, an I-type frequency tripling crystal and a wave plate, wherein the light beam high reflection lens, the I-type doubling crystal, the wave plate and the I-type frequency tripling crystal are sequentially arranged along the horizontal direction, the I-type frequency tripling crystal is an I-type BBO or LBO crystal or the like, horizontal central axes of the light beam high reflection lens, the I-type doubling crystal, the wave plate and the I-type frequency tripling crystal are arranged on the same horizontal common axis II, and the wave plate is arranged between the I-type frequency tripling crystal and the I-type doubling crystal.

Further, the cylindrical lens has the thermal lens characteristic of a compensation crystal, the spherical lens is used for adjusting the spot size of the light beam, and the first fundamental frequency high reflector is a high reflector of the fundamental frequency of the laser medium.

Further, the first prism and the second prism are a UV-gradually-changed fused siliconized first prism and a UV-gradually-changed fused siliconized second prism.

Further, the adjustable mirror is a folding mirror, and the laser medium can be preselected.

Further, the multi-wave high-reflection lens is a dichroic mirror.

Further, the type I nonlinear second harmonic crystal is a type I LBO crystal.

Further, the II type nonlinear third harmonic crystal is II type lithium triborate crystal.

The beneficial effects obtained by adopting the invention are as follows: compared with the method of the third harmonic outside the cavity, the laser equipment provided by the invention fully utilizes the strong fundamental wave light in the cavity, the strong fundamental wave light is reflected by the first fundamental frequency high reflector and the second fundamental frequency high reflector, the basic light beam is polarized perpendicular to the crystal axis, and the generated second harmonic beam is polarized parallel to the optical axis, the high transmission beam is reflected by the high reflection lens and the fundamental frequency and second harmonic high reflection lens, the fundamental beam and the second harmonic beam are orthogonally polarized and generate a third harmonic beam, the polarization of the polarization base beam and the polarization of the third harmonic beam, the polarization of which is parallel to one of the two input beams, are parallel, so that the conversion efficiency is improved, the second harmonic power is fully utilized for carrying out multiple frequency mixing, the efficiency and the power of the third harmonic are increased, the polarization optical coupling loss is reduced, and the beam quality and the stability of the third harmonic are improved.

Drawings

FIG. 1 is a schematic diagram of a laser apparatus for improving the efficiency of third harmonic generation according to the present invention;

FIG. 2 is a schematic diagram of an alternative embodiment of a laser apparatus for improving third harmonic generation efficiency in accordance with the present invention;

FIG. 3 is a graph of conversion efficiency of a laser apparatus for improving the efficiency of third harmonic generation in accordance with the present invention;

FIG. 4 is a schematic diagram of an alternative embodiment of a laser apparatus for improving third harmonic generation efficiency in accordance with the present invention;

fig. 5 is a schematic diagram of an alternative embodiment of a laser apparatus for improving the efficiency of third harmonic generation according to the present invention.

The device comprises an optical cavity 1, an optical cavity 2, a primary beam generation strengthening device, a tunable reflector 3, a multi-wave reflection strengthening output device 4, a third harmonic strengthening reflection device 5, a third harmonic strengthening reflection device 6, a laser medium 7, a laser pump 8, a first fundamental frequency high reflector, a 9, a Q switch 10, a spherical lens 11, a cylindrical lens 12, a multi-wave high reflector, a 13 beam high reflector, a 14, a I type nonlinear second harmonic crystal, a 15, a II type nonlinear third harmonic crystal, a 16, a first prism, a 17, a second prism, a 18, a guide lens 19, a second harmonic emitter 20, a wave plate 21, an I type triple frequency crystal, and a 22, I type double frequency crystal.

Detailed Description

The technical solutions of the present invention will be further described in detail with reference to specific implementations, and all the portions of the present invention not described in detail are the prior art.

The present invention will be described in further detail with reference to the accompanying drawings.

As shown in fig. 1-5, the laser device for improving the third harmonic generation efficiency of the present invention includes an optical cavity 1, a first-order enhancing device 2 for generating a base beam, an adjustable mirror 3, a multiple-wave reflection enhancing output device 4 and a third-order harmonic enhancement reflection device 5, wherein the first-order enhancing device 2 for generating a base beam, the adjustable mirror 3, the multiple-wave reflection enhancing output device 4 and the third-order harmonic enhancement reflection device 5 are disposed in the optical cavity 1, the first-order enhancing device 2 for generating a base beam and the adjustable mirror 3 are sequentially arranged along a horizontal direction, horizontal central axes of the first-order enhancing device 2 for generating a base beam and the adjustable mirror 3 are disposed on a same horizontal common axis, an angle of the adjustable mirror 3 can be adjusted, the multiple-wave reflection enhancing output device 4 is disposed under the adjustable mirror 3, and the third-order enhancing reflection device 5 and the multiple-wave reflection enhancing output device 4 are sequentially arranged along a horizontal direction The third harmonic enhanced reflection device 5 and the multiple wave reflection enhanced output device 4 are arranged on the same horizontal common shaft II along the horizontal central axis; the primary reinforcing device 2 for generating the fundamental light beam comprises a laser medium 6, a laser pump 7, a first fundamental frequency high reflector 8, a Q switch 9, a spherical lens 10 and a cylindrical lens 11, wherein the laser medium 6, the laser pump 7, the first fundamental frequency high reflector 8, the Q switch 9, the spherical lens 10, the cylindrical lens 11 and the adjustable reflector 3 are sequentially arranged along the horizontal direction, the laser medium 6, the laser pump 7, the first fundamental frequency high reflector 8, the Q switch 9, the spherical lens 10, the cylindrical lens 11 and the adjustable reflector 3 are arranged on the same horizontal common axis, the multiple wave reflection reinforcing output device 4 is a multiple wave high reflector 12, and the multiple wave high reflector 12 is arranged below the adjustable reflector 3; the third harmonic enhanced reflection device 5 comprises a light beam high reflection lens 13, a type I nonlinear second harmonic crystal 14 and a type II nonlinear third harmonic crystal 15, the multiple wave high reflection lens 12, the light beam high reflection lens 13, the type I nonlinear second harmonic crystal 14 and the type II nonlinear third harmonic crystal 15 are sequentially arranged along the horizontal direction, the light beam high reflection lens 13, the type I nonlinear second harmonic crystal 14, the type II nonlinear third harmonic crystal 15 and the multiple wave high reflection lens 12 are arranged on the same horizontal common axis II, the type I nonlinear second harmonic crystal 14 is used for generating second harmonics, the type II nonlinear third harmonic crystal 15 is used for generating third harmonics, and the light beam high reflection lens 13 is a high reflection lens of fundamental frequency and second harmonic frequency spectrum.

Output device 4 is strengthened in multiple wave reflection includes prism 16, two 17 of prism, direction lens 18 and second harmonic transmitter 19, one 16 of prism and two 17 apex angles of prism meet the slope and locate adjustable speculum 3 and be close to one side of laser pump 7, the oblique top of two 17 of prism is located to one 16 of prism, direction lens 18 is located directly over one 16 of prism, one side of adjustable reflector principle laser pump 7 is located to the second harmonic generator, second harmonic transmitter 19 is located between adjustable speculum 3 and the direction lens 18, two 17 of prisms and II type nonlinear third harmonic crystal 15 locate on same water flat line.

The third harmonic enhanced reflection device 5 comprises a light beam high reflection lens 13, an I-type nonlinear second harmonic crystal 14, an II-type nonlinear third harmonic crystal 15 and a wave plate 20, wherein the light beam high reflection lens 13, the I-type nonlinear second harmonic crystal 14, the II-type nonlinear third harmonic crystal 15 and the wave plate 20 are sequentially arranged along the horizontal direction, the horizontal central axes of the light beam high reflection lens 13, the I-type nonlinear second harmonic crystal 14, the II-type nonlinear third harmonic crystal 15 and the wave plate 20 are arranged on the same horizontal common axis II, and the wave plate 20 is arranged between the II-type nonlinear third harmonic crystal 15 and the multi-wave high reflection lens 12.

The third harmonic enhanced reflection device 5 comprises a light beam high reflection lens 13, an I-type doubling crystal 22, an I-type frequency tripling crystal 21 and a wave plate 20, wherein the light beam high reflection lens 13, the I-type doubling crystal 22, the wave plate 20 and the I-type frequency tripling crystal 21 are sequentially arranged along the horizontal direction, horizontal central axes of the light beam high reflection lens 13, the I-type doubling crystal 22, the wave plate 20 and the I-type frequency tripling crystal 21 are arranged on the same horizontal common axis II, and the wave plate 20 is arranged between the I-type frequency tripling crystal 21 and the I-type frequency tripling crystal 22.

The cylindrical lens 11 has the thermal lens characteristic of a compensation crystal, the spherical lens 10 is used for adjusting the spot size of the light beam, and the first fundamental frequency high reflector 8 is a high reflector of the fundamental frequency of the laser medium 6.

The first prism 16 and the second prism 17 are fused siliconized prisms 16 and 17 with UV gradual change.

The adjustable mirror 3 is a folding mirror.

The multi-wave high reflection mirror 12 is a dichroic mirror.

The type I nonlinear second harmonic crystal 14 is a type I LBO crystal.

The II-type nonlinear third harmonic crystal 15 is a II-type lithium triborate crystal.

In particular use, as shown in fig. 1, a laser medium 6 provides laser material, a laser pump 7 is used to excite the laser medium 6, the laser medium 6 is preselected to produce a fundamental laser beam frequency at a preselected fundamental frequency along a common axis, a Q-switch 9 may be provided where pulsed laser output is desired rather than continuous wave output, the laser is suppressed by introducing losses in the resonator in the Q-switch 9 option while energy pumps are pumped and stored in population inversion, the losses are reduced to allow laser emission once the desired population inversion is obtained, in this mode a large pulse train output may be produced from the laser, the beam is emitted from the front of the laser medium 6 and from the back of the laser medium 6 to a fundamental frequency high mirror one 8, the fundamental frequency high mirror one 8 highly reflects the fundamental frequency of the laser medium 6, the adjustable mirror 3 highly reflects the fundamental frequency of the laser medium 6, and optionally a high reflection for the second harmonic frequency, which forms an optical output oscillation with the reflection from the front end high frequency mirror-8 of the laser medium 6, a multi-wave high reflection mirror 12 forming an optical loop with the adjustable mirror 3, the multi-wave high reflection mirror 12 highly reflecting the high transmitted beam of the preselected fundamental frequency and third harmonic frequency beams while also highly reflecting the second harmonic wavelength beams, a type II nonlinear third harmonic crystal 15 for the second harmonic wavelength beamsA type II nonlinear third harmonic is generated which oscillates with the light beam reflected by the multi-wave highly reflective mirror 12, the output of the type II nonlinear third harmonic crystal 15 is directed to a type I nonlinear second harmonic crystal 14 for second harmonic generation, the output of the type I nonlinear second harmonic crystal 14 is directed to a light beam highly reflective mirror 13, the light beam highly reflective mirror 13 highly reflects the fundamental frequency and the second harmonic spectrum, the formed optical axis is generally U-shaped, and for example, Nd: YLF laser medium 6, emitting a light beam with a wavelength of 1053nm, which, according to the invention, will generate a second harmonic light beam with a wavelength of 527nm and a UV third harmonic light beam with a wavelength of 351 nm; the fundamental wave beam from the laser medium 6 is reflected by the fundamental frequency high reflection mirror 8 and amplified by the laser medium 6 along the horizontal common axis, then the fundamental wave beam is vertically polarized on the adjustable mirror 3, the vertically polarized fundamental wave beam is reflected on the multiple wave high reflection mirror 12 and forms a transmission horizontally polarized fundamental wave beam, the laser medium 6 emits light with vertical polarization because the vertically polarized beam is favorable and does not support the horizontally polarized beam, optionally, the adjustable mirror 3 can reflect the horizontally polarized fundamental wave beam and emit the vertically polarized fundamental wave beam, then the laser material will be horizontally polarized laser light, the multiple wave high reflection mirror 12 guides the reflected beam from the adjustable mirror 3 to the type II nonlinear third harmonic crystal 15, the fundamental wave beam is incident on the type I nonlinear second harmonic crystal 14 to the type II nonlinear third harmonic crystal 15, since the type II nonlinear third harmonic crystal 15 converts the fundamental light beam into the third harmonic light beam only in the presence of the second harmonic light beam, the fundamental light beam is not affected when passing through the type II nonlinear third harmonic crystal 15, a small part of the fundamental light beam is converted into a horizontally polarized second harmonic light beam by satisfying its phase matching condition (K (2w) ═ K (w) + K (w))) by the type I nonlinear second harmonic crystal 14, phase-matched (crystal orientation) or noncritical phase-matched (temperature tuning), the fundamental light beam and the second harmonic light beam are transmitted toward the beam highly reflecting mirror 13 and reflected from the same mirror, and when the fundamental light beam passes through the type I nonlinear second harmonic crystal 14 upon reflection from the beam highly reflecting mirror 13, another small part of the fundamental light beam is converted into its second harmonic light beam, which is converted into its second harmonic light beam together with the anti-reflection mirrorThe emitted second harmonic beams are superposed to form a combined second harmonic beam, and the type II nonlinear third harmonic crystal 15 satisfies a phase matching condition k (3W)^1/2(k (w) + k (2w)) a portion of the fundamental beam and most of the second harmonic beam transmitted from the type I nonlinear second harmonic crystal 14 are converted into a third harmonic beam, the fundamental beam, the second harmonic beam and the third harmonic beam are directed to the plate multi-wave high reflection mirror 12, the multi-wave high reflection mirror 12 removes the third harmonic beam from the cavity and reflects the fundamental beam and the second harmonic beam to the adjustable mirror 3, while the second harmonic beam and the third harmonic beam can be output together from the cavity. The second harmonic beam reflects off the adjustable mirror 3 and pumps the laser medium 6 to increase pumping efficiency, the spot size on the type I nonlinear second harmonic crystal 14 and the type II nonlinear third harmonic crystal 15 is ideally one-half the crystal diameter or less, the resulting laser has higher efficiency, achieving a total fundamental to third harmonic conversion in excess of 25%, preferably from about 25% to about 50% efficiency, and most preferably in excess of about 50% conversion efficiency; the total conversion efficiency is calculated by dividing the triple frequency output power by the total fundamental frequency output power without the generation of second and third harmonic frequencies, e.g., typical prior art Nd: the YLF laser produces a total of 12 watts of power at the fundamental frequency at a Q-switched 91000Hz repetition rate of 150 nanosecond pulse width. Using the same laser, the laser produces a total power of 2 watts or less of tripled power. The overall conversion efficiency is below 17%. Laser Nd according to the invention: YLF as shown in FIG. 1, produced a tripled frequency output of 6.8W of UV wavelength, from a fundamental power of 12W, with a repetition rate of 1000Hz, and a conversion efficiency of about 57%.

Referring to fig. 2, there is shown an alternative example of the laser apparatus of the present invention in which a pair of prisms, prism one 16 and prism two 17, are shown, the third harmonic beam is separated from the fundamental beam using UV graded fused siliconized prism one 16 and prism two 17, the fundamental beam from the laser medium 6 is highly reflected by the directing mirror 18, the fundamental beam is reflected to the prism one 16 and prism two 17, deflecting and directing the fundamental beam to the type II nonlinear third harmonic crystal 15, the beam passes through the type II nonlinear third harmonic crystal 15, the type I nonlinear second harmonic crystal 14 and is reflected by the beam highly reflective mirror 13, the fundamental beam, the second harmonic beam and the third harmonic beam enter the prism two 17, where the beams are displaced from one to another, the displaced beams enter the prism one 16 increasing the displacement between the beams, the fundamental beam exiting the prism one 16 is directed to the adjustable mirror 3 and reflected back to the laser medium 6, the second and third harmonic beams are reflected by directing optics 18. directing optics 18 reflect the third and second harmonic beams and reflect the beams out of the laser cavity, and a second harmonic emitter 19 provides a second harmonic beam to block the second harmonic beam from the output.

In another aspect of the invention, it has been found that improved recovery of the third harmonic beam from the laser cavity can be achieved if the polarization of the third harmonic beam with the multi-wave highly reflective optic 12 is "P" polarized, achieving removal of more than about 90%, preferably about 95% to 99%, more preferably about 99% of the third harmonic, as in fig. 4, except that a wave plate 20 is provided between the type II nonlinear third harmonic crystal 15 and the multi-wave highly reflective optic 12, the multi-wave highly reflective optic 12 is preferably coated with a dichroic mirror for high transmission of the third harmonic frequency beam of the fundamental frequency beam to the multi-wave highly reflective optic 12 with P polarization on the mirror surface, which reflects better than 99.5% at the fundamental wavelength, and better than 95% at the third harmonic beam when the third harmonic beam is P polarized to the optic, the fundamental beam is reflected by the adjustable mirror 3 with vertical polarization, then the fundamental wave light beam is reflected by the multi-wave high reflection mirror 12 and passes through the wave plate 20, the wave plate 20 rotates the fundamental wave light beam into an integer of full wave or full wave, the polarization of the fundamental wave beam is not changed, the fundamental wave light beam passes through the type II nonlinear third harmonic crystal 15 without being affected by the absence of the second harmonic light beam, the fundamental wave light beam is generated on the type I nonlinear second harmonic crystal 14, a part of the fundamental wave light beam is converted into the second harmonic, the polarization of the fundamental wave light beam is kept vertically polarized, and the resultant second harmonic light beam is horizontally polarized, the beam high reflection mirror 13 reflects the fundamental wave and the second harmonic light beam through the type I nonlinear second harmonic crystal 14, and a further part of the fundamental wave light beam is converted into the horizontally polarized second harmonic light beam, the fundamental wave and the second harmonic light beam are guided through the type II nonlinear third harmonic crystal 15, which requires the base and second harmonic light beams to be generated on, a portion of the fundamental wave and a major portion of the second harmonic are converted to a third harmonic beam having the same polarization as the fundamental wave, in this case vertical polarization, the beam exiting the type II nonlinear third harmonic crystal 15 is directed through a wave plate 20, the wave plate 20 performs an 1/2 wave rotation on the third harmonic beam to convert its polarization to horizontal polarization before an incident occurs on its multi-wave highly reflective optic 12, which multi-wave highly reflective optic 12 will remove substantially all of the third harmonic beam from the laser cavity; or fig. 4 may be further modified, a wave plate 20 may be placed between the type II nonlinear third harmonic crystal 15 and the multi-wave highly reflective mirror 12, which rotates a half wave for the fundamental wavelength and a full wave for the third harmonic beam, and other combinations may be provided to achieve "P" polarization when the third harmonic beam occurs on the multi-wave highly reflective mirror 12.

As still another alternative example, as shown in fig. 5, in operation, a fundamental-wave-length light beam having vertical polarization is reflected by the adjustable mirror 3 to the multiple-wave high-reflection mirror 12, reflected by the I-type frequency tripling crystal 21 and the wave plate 20, the fundamental light beam passing through the I-type frequency tripling crystal 21 without being affected by the crystal unless the second-harmonic light beam is polarized in parallel with the fundamental light beam, which has no effect on the fundamental light beam, passing through the wave plate 20 with its polarization unchanged, the light beam occurring on the I-type frequency doubling crystal 22, the I-type frequency doubling crystal 22 converts a part of the fundamental light beam into a horizontally polarized second-harmonic light beam, the fundamental and second harmonics being reflected from the beam high-reflection mirror 13 back to the I-type frequency doubling crystal 22, in which a part of the fundamental wave is converted again into a horizontally polarized second-harmonic light beam, the polarization of the second-, the fundamental wave and the second harmonic light beam have polarization relatively parallel to each other, which is necessary for the type I triple crystal for the third harmonic conversion, a part of the fundamental wave and most of the second harmonic are converted into the third harmonic light beam and exit the type I triple crystal 21, the generated third harmonic light beam is horizontally polarized, and then the horizontally polarized third harmonic light beam is incident on the multiple-wave high reflection mirror 12, the orientation of the multiple-wave high reflection mirror 12 is such that the horizontally polarized light beam will be P-polarized to the multiple-wave high reflection mirror 12, the P-polarized third harmonic light beam will be substantially completely transmitted through the multiple-wave high reflection mirror 12, and the unconverted fundamental light beam will be reflected since the multiple-wave high reflection mirror 12 is reflective to the fundamental light beam.

The present invention and its embodiments have been described above, and the description is not intended to be limiting, and the drawings are only one embodiment of the present invention, and the actual structure is not limited thereto. In summary, those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiments as a basis for designing or modifying other structures for carrying out the same purposes of the present invention without departing from the spirit and scope of the invention as defined by the appended claims.