CN215119530U

CN215119530U - High-power laser

Info

Publication number: CN215119530U
Application number: CN202022295072.7U
Authority: CN
Inventors: 尹雨松; 刘学松; 王世波; 陶锐; 周晓海; 黄巧; 杨焕鹏; 刘明明
Original assignee: Photonics Laser Technology Dongguan Co ltd
Current assignee: Photonics Laser Technology Dongguan Co ltd
Priority date: 2020-10-15
Filing date: 2020-10-15
Publication date: 2021-12-10
Anticipated expiration: 2030-10-15

Abstract

The invention provides a high-power laser. Including optical resonator, harmonic generating device, optical axis, speculum one, folding speculum, speculum two and cooling jacket, optical resonator locates between speculum reflection surface and the speculum two reflection surfaces, the optical axis is located in the optical resonator, harmonic generating device locates on the optical axis, folding speculum is located between speculum one and the speculum two and is close to harmonic generating device, harmonic generating device locates in the cooling jacket. The invention belongs to the technical field of laser, and particularly relates to a high-power laser which improves output power, long-term stability and pumping conversion efficiency.

Description

High-power laser

Technical Field

The utility model relates to a laser technical field especially relates to a high power laser.

Background

In end-pumped lasers, crystals doped with active ions such as Nd: YVO₄And Nd: YLF and Nd: end-pumped lasers of YAG crystal, which can be end-pumped from both ends, however, the output power of the laser is limited by problems such as thermal lenses, thermal birefringence and thermal distortion effects, and crystal breakage, for example, in order to separate the laser from Nd: higher output power is obtained with YAG lasers, especially for linearly polarized TEM₀₀Mode, usually requiring an external amplifier, methods have been proposed to address the heat and stress problems caused by pumping, but the output power is still limited, the conventional wisdom holds that high brightness pumping can achieve optimal conversion efficiency and better mode quality, and for high efficiency, compactness and good mode quality, the optical cavity length is usually limited to 30cm or less and the spot diameter is 0.6mm or less; in addition, the predominant atomic percentage doping level of Nd is about 1%, Nd: YLF and Nd: YVO₄The same is true, and typical diode end-pumped Nd: YAG laser in polarization TEM₀₀The output power in the mode is 10W or less.

Existing diodesPumped solid state lasers have higher efficiency and compactness than lamp pumped lasers, particularly in those requiring TEM₀₀In applications of a mode laser beam, such as Nd: YAG, Nd: YLF and Nd: YVO₄Such diode end pumped laser crystals have produced the best mode quality and highest TEM₀₀Mode output power, but in conventional end-pumped designs, the method of removing heat from the diode-pumped laser crystal is "conduction" cooling (the laser crystal is mounted directly on a heat sink), which results in non-uniform heating of the laser medium since only a portion of the pump power is converted to laser radiation, while the remaining power is converted to radiationless transitions and absorbed and transferred to the crystal lattice; in order to counteract the thermal effects of the pump radiation, the lasing medium must be cooled during operation, and as such, mounting the crystal on a heat sink causes additional mechanical stresses on the crystal which are sensitive to environmental and temperature variations, which in turn leads to long term instability of the laser in an industrial environment, with consequent temperature non-uniformity and thermal stress induced birefringence, thermally induced distortion severely limiting TEM₀₀Maximum output power in mode, e.g. diode end-pumped Nd: linear polarization TEM of YAG laser₀₀The mode output power is usually limited to around 10W, so the higher output power, high reliability and stability of the laser are crucial for its industrial application.

SUMMERY OF THE UTILITY MODEL

In order to solve the problem, the utility model provides an improve output, improved long-term stability and pumping conversion efficiency's high power laser.

In order to realize the above functions, the utility model discloses the technical scheme who takes as follows: a high-power laser comprises an optical resonant cavity, a harmonic generation device, an optical axis, a first reflector, a folding reflector, a second reflector and a cooling jacket, wherein the optical resonant cavity is arranged between the reflection surface of the first reflector and the reflection surface of the second reflector, the first reflector is used for partial reflection and partial transmission of fundamental frequency beams and can be used as an output coupler of the laser, preferably, the first reflector has 85% reflectivity and 15% transmissivity of the fundamental frequency beams, the two pairs of fundamental frequency beams have high reflectivity, the optical axis is arranged in the optical resonant cavity, the harmonic generation device is arranged on the optical axis, the folding reflector is arranged between the first reflector and the second reflector and is close to the harmonic generation device, the folding reflector is highly reflective to the fundamental frequency beams, the folding reflector is highly transparent to pumping beams, and forms a certain acute angle with the longitudinal axis of the harmonic generation device, the fundamental frequency light beam emitted from the surface of the harmonic wave generating device is reflected at an acute angle and is transmitted to the reflecting mirror to leave, and the harmonic wave generating device is arranged in the cooling jacket.

Further, the optical resonant cavity is configured as a TEM₀₀And (4) operating in a mode.

Further, the harmonic generation device comprises a laser medium and a pump laser device.

Further, the harmonic generation device comprises a laser medium, a pump laser device, a first folding mirror and a polarization discriminator.

Further, the harmonic generation device comprises a laser medium, a pumping laser device, a first folding reflector and a multiple harmonic generation device.

Further, the harmonic generation device comprises a laser medium, a pump laser device and an OPO generator.

Furthermore, the laser medium is arranged in an optical resonant cavity between the first reflecting mirror and the second reflecting mirror and close to the folding reflecting mirror, the laser medium is provided with a front end face and a rear end face, the laser medium generates fundamental frequency beams transmitted from the front end face and the rear end face, the diameter of the fundamental frequency beams is 0.8-2.0 mm, and the diameter of the laser medium is 1.6-5 times of the diameter of the fundamental frequency beams.

Furthermore, the first folding reflector is arranged in an optical resonant cavity between the first folding reflector and the second folding reflector and close to the laser medium, the first folding reflector reflects a fundamental frequency light beam emitted from the rear end face of the laser medium at an acute angle and transmits the reflected fundamental frequency light beam to the second folding reflector, the folding reflector is high-reflective relative to the fundamental frequency light beam and high-transparent relative to a pump light beam, the pump laser device is arranged on the opposite outer sides of the laser medium and the folding reflector, the pump laser device comprises a diode pump source and a lens assembly, the lens assembly is respectively arranged on the outer sides of the first folding reflector and the first folding reflector, the diode pump source is arranged on the outer side of the lens assembly, the wavelength of the pump light beam emitted by the diode pump source is specified or adjusted by cooling temperature so as to match an absorption band of the laser medium, and after passing through the lens assembly, the pump light beam is transmitted by the first folding reflector and excites the laser medium, when properly aligned, the laser will lase at a preselected fundamental beam frequency.

Further, the OPO generator is a nonlinear crystal, such as an LBO, BBO, KTP, KTA crystal or any other suitable crystal.

Furthermore, the polarization discriminator is arranged between the first folding reflector and the second folding reflector, the polarization discriminator is a Brewster plate, and the light beam transmitted from the rear end face of the laser medium is firstly reflected by the first folding reflector, then passes through the polarization discriminator and finally is reflected back to the laser medium by the second reflector.

Further, the multiple harmonic generation device includes a Q switch, a dichroic mirror, a multiple harmonic generator, and a third reflecting mirror, the Q switch is disposed between the first reflecting mirror and the second reflecting mirror, the Q switch can be located at any position in the cavity if space permits, the dichroic mirror is disposed between the first reflecting mirror and the second reflecting mirror, the dichroic mirror is disposed at or near the brewster angle of the fundamental frequency beam, the surface of the dichroic mirror near the first reflecting mirror is not coated with a film, while the surface near the second reflecting mirror is coated with a multiple harmonic beam highly reflective film and a P-polarized fundamental frequency beam highly transmissive film, if the angle of the dichroic mirror is not the brewster angle, the surface of the dichroic mirror near the first reflecting mirror is also coated with a P-polarized fundamental frequency beam highly transmissive film, which is advantageous for oscillation of the P-polarized fundamental frequency beam, thereby suppressing S polarization, and the multi-harmonic generator is arranged between the dichroic mirror and the first reflecting mirror, and the third reflecting mirror is arranged close to the dichroic mirror.

Further, the multiple harmonic generator includes a second harmonic generator.

Further, the multiple harmonic generator includes a second harmonic generator and a third harmonic generator.

Further, the multiple harmonic generator includes a second harmonic generator, a third harmonic generator, and a fourth harmonic generator.

Further, the second harmonic generator is a second harmonic nonlinear crystal, and the second harmonic nonlinear crystal is an I or II type phase matching nonlinear crystal.

Further, the third harmonic generator is a third harmonic nonlinear crystal, and the third harmonic nonlinear crystal is an I or II type phase matching nonlinear crystal.

Further, the fourth harmonic generator is a fourth harmonic nonlinear crystal, and the fourth harmonic nonlinear crystal is a class I phase-matched fourth harmonic LBO nonlinear crystal.

Further, the laser medium is a laser crystal with Nd.

Further, the laser crystal is Nd: YAG crystal with doping concentration of 0.2-0.8% and length not less than 20 mm.

Further, the laser crystal is Nd: YAG crystal with doping concentration of 0.4-0.6%.

Further, the laser crystal is Nd: the doping concentration of the YLF crystal is about 0.3% -0.8%, and the length of the laser crystal is not less than 20 mm.

Further, the laser crystal is Nd: YLF crystal, the doping concentration is about 0.4% -0.7%.

Further, the laser crystal is Nd: YVO₄The crystal has the doping concentration of about 0.1-0.5%, and the length of the laser crystal is not less than 12 mm.

Further, the laser crystal is Nd: YVO₄Crystal with doping concentration of about 0.2-0.4%.

Further, the length of the optical resonant cavity is 22 cm-100 cm.

Further, the length of the optical resonant cavity is 35 cm-100 cm.

The utility model adopts the above structure to gain beneficial effect as follows: the utility model provides a pair of high power laser has solved prior art's Nd: YAG lasers have disadvantages such as thermal lenses, thermally induced birefringence and distortion, depolarization losses and poor mode quality, it is difficult to obtain output powers in excess of 10W, and such lasers operate unreliably at 10W, and in part because of Nd: the defect that the output power may vary from day to day due to the mechanical stress of mounting on the YAG laser crystal is to use an end-pumped Nd that can produce an output power of more than 10W, preferably 15W, 20W or more, and has long-term stability: YAG laser, can realize second harmonic, third harmonic, fourth harmonic or higher order harmonic laser, with fundamental frequency beam optical communication, such harmonic laser has improved efficiency and power, OPO generator can be in optical communication with fundamental frequency beam in the optical resonator, realize from fundamental frequency beam to OPO high conversion efficiency of generator output.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of a high power laser according to the present invention;

fig. 2 is a schematic structural diagram of another embodiment of a high power laser according to the present invention;

fig. 3 is a schematic structural diagram of a second harmonic generator of a high power laser according to the present invention;

fig. 4 is a schematic structural diagram of a third harmonic generator of the high power laser of the present invention;

fig. 5 is a schematic structural diagram of a fourth harmonic generator of the high power laser of the present invention;

fig. 6 is a schematic diagram of a cooling jacket structure of a high power laser of the present invention;

fig. 7 is a perspective view of a laser medium with a low Nd doped or undoped YAG crystal at both ends or a low Nd doped or undoped YLF crystal at both ends, a high doped YLF crystal in the center of a high power laser of the present invention;

fig. 8 is a perspective view of the lasing medium of another cooling jacket of a high power laser of the present invention;

FIG. 9 is a schematic view ofThe utility model relates to a high power laser's Nd that has low Nd and adulterates: YVO₄A perspective view of a laser medium of the crystal;

fig. 10 is a schematic structural diagram of an OPO laser of the high power laser of the present invention.

The optical resonance cavity light source device comprises an optical resonance cavity 1, an optical axis 2, a harmonic wave generating device 3, an optical axis 4, a first reflecting mirror 5, a folding reflecting mirror 6, a second reflecting mirror 7, a cooling jacket 8, a laser medium 9, a pump laser device 10, a polarization discriminator 11, a multiple harmonic wave generating device 12, an OPO generator 13, a diode pump source 14, a fourth harmonic wave generator 15, a lens component 16, a third harmonic wave generator 17, a first folding reflecting mirror 18, a Q switch 19, a dichroic mirror 20, a multiple harmonic wave generator 21, a third reflecting mirror 22 and a second harmonic wave generator.

Detailed Description

The technical solution of the present invention will be described clearly and completely with reference to the accompanying drawings, and obviously, the described embodiments are some, but not all embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

As shown in fig. 1-10, the utility model relates to a high power laser, including optical resonator 1, harmonic generation device 2, optical axis 3, a speculum 4, folding mirror 5, speculum two 6 and cooling jacket 7, optical resonator 1 is located between a speculum 4 reflecting surface and the speculum two 6 reflecting surfaces, optical axis 3 is located in optical resonator 1, harmonic generation device 2 is located on optical axis 3, folding mirror 5 is located between speculum 4 and the speculum two 6 and is close to harmonic generation device 2, harmonic generation device 2 is located in cooling jacket 7.

The optical resonant cavity 1 is arranged in TEM₀₀And (4) operating in a mode.

The harmonic generation device 2 comprises a laser medium 8 and a pump laser device 9.

The harmonic generation device 2 comprises a laser medium 8, a pump laser device 9, a first folding mirror 17 and a polarization discriminator 10.

The harmonic generation device 2 comprises a laser medium 8, a pumping laser device 9, a first folding reflector 17 and a multiple harmonic generation device 11.

The harmonic generation device 2 comprises a laser medium 8, a pump laser device 9, a first folding mirror 17 and an OPO generator 12.

The laser medium 8 is arranged in the optical resonant cavity 1 between the first reflector 4 and the second reflector 6 and close to the folding reflector 5, the laser medium 8 is provided with a front end face and a rear end face, the laser medium 8 generates fundamental frequency beams transmitted from the front end face and the rear end face, the diameter of the fundamental frequency beams is 0.8-2.0 mm, and the diameter of the laser medium 8 is 1.6-5 times of the diameter of the fundamental frequency beams.

The first folding reflector 17 is arranged in the optical resonant cavity 1 between the first reflector 4 and the second reflector 6 and is close to the laser medium 8, the pump laser device 9 is arranged on the outer side of the laser medium 8 relative to the folding reflector 5, the pump laser device 9 comprises a diode pump source 13 and a lens component 15, the lens component 15 is arranged on the outer side of the folding reflector 5 and the outer side of the first folding reflector 17 respectively, and the diode pump source 13 is arranged on the outer side of the lens component 15.

The OPO generator 12 is a nonlinear crystal.

The polarization discriminator 10 is arranged between the first folding reflector 17 and the second reflector 6, and the polarization discriminator 10 is a Brewster plate.

Multiple harmonic generation device 11 includes Q switch 18, dichroic mirror 19, multiple harmonic generator 20 and reflector third 21, Q switch 18 is located between reflector first 4 and folding mirror 5, dichroic mirror 19 is located between folding mirror first 17 and reflector second 6, multiple harmonic generator 20 is located between dichroic mirror 19 and reflector first 4, reflector third 21 is placed near dichroic mirror 19.

The multiple harmonic generator 20 includes a second harmonic generator 22.

The multiple harmonic generator 20 includes a second harmonic generator 22 and a third harmonic generator 16.

The multiple harmonic generator 20 includes a second harmonic generator 22, a third harmonic generator 16, and a fourth harmonic generator 14.

The second harmonic generator 22 is a second harmonic nonlinear crystal, which is an I or II type phase-matching nonlinear crystal.

The third harmonic generator 16 is a third harmonic nonlinear crystal, which is an I or II type phase-matching nonlinear crystal.

The fourth harmonic generator 14 is a fourth harmonic nonlinear crystal that is a class I phase matched fourth harmonic LBO nonlinear crystal.

The laser medium 8 is a laser crystal with Nd.

The laser crystal is Nd: YAG crystal with doping concentration of 0.2-0.8% and length not less than 20 mm.

The laser crystal is Nd: YAG crystal with doping concentration of 0.4-0.6%.

The laser crystal is Nd: the doping concentration of the YLF crystal is about 0.3% -0.8%, and the length of the laser crystal is not less than 20 mm.

The laser crystal is Nd: YLF crystal, the doping concentration is about 0.4% -0.7%.

The laser crystal is Nd: YVO₄The crystal has the doping concentration of about 0.1-0.5%, and the length of the laser crystal is not less than 12 mm.

The laser crystal is Nd: YVO₄Crystal with doping concentration of about 0.2-0.4%.

The length of the optical resonant cavity 1 is 22 cm-100 cm.

The length of the optical resonant cavity 1 is 35 cm-100 cm.

The laser comprises a first mirror 4 and a second mirror 6 forming an optical resonator 1, in which optical resonator 1 a laser medium 8, in particular a Nd-doped laser medium 8, such as Nd: YAG, Nd: YLF or Nd: YVO₄A crystal, the pumped laser medium 8 generates fundamental frequency propagating from the front end face and the back end face of the laser medium 8The surface of a first reflecting mirror 4 of the laser beam is highly reflective to the fundamental frequency beam; the surface of the second reflector 6 reflects part of the fundamental frequency beam, the laser medium 8 is pumped by a diode pump source, such as a laser diode, a diode array or a fiber coupled laser diode, adjacent to the front end face and the rear end face of the laser medium 8, the wavelength of the laser medium is matched with the phase of the absorption band of the laser medium 8, the optical resonant cavity 1 is designed to have a diameter of the fundamental frequency beam in the laser medium 8 of about 0.8 mm-2 mm, ideally, the diameter of the laser medium 8 is about 1.6-4 times of the diameter of the fundamental frequency beam in the laser medium 8, and ideally, a cooling jacket 7 is arranged around the laser medium 8 to directly cool the laser medium 8, and the optical resonant cavity 1 is also designed to have the fundamental frequency beam reflected by a TEM₀₀Mode operation, preferably a polarization discriminator 10 such as a brewster plate is included within the optical cavity 1 to facilitate operation of a particular polarization state.

It is expected that the present invention will be used for Nd: YAG laser, prior art Nd: YAG lasers have disadvantages such as thermal lenses, thermally induced birefringence and distortion, depolarization losses and poor mode quality, it is difficult to obtain output powers in excess of 10W, and such lasers operate unreliably at 10W, and in part because of Nd: the output power may vary from day to day due to the mechanical stress of the mounting on the YAG laser crystal. The utility model discloses a can produce the output that exceeds 10W, preferably have 15W, 20W or higher output and have long-term stability's end-face pumping Nd: YAG laser.

In another aspect of the invention, a neodymium-doped crystal is used, in particular, a low Nd-doped Nd: YAG, Nd: YLF and Nd: YVO₄The crystal may be a multi-level doped crystal or an end-face undoped crystal, or a single low-Nd doped crystal.

In the prior art, Nd: YAG, Nd: YLF and Nd: YVO₄The crystal is doped by about 1%, the present invention preferably uses a low doped crystal, i.e. for Nd: YAG is doped with 0.2 to 0.8 percent of Nd; preferably about 0.4% to 0.6% Nd. For a single piece of Nd: YLF crystals doped with about 0.3% to about 0.8% Nd, preferably about 0.4% to about 0.7% Nd. To pairIn a single piece of Nd: YVO₄About 0.1% to about 0.5% Nd, preferably about 0.2% to about 0.4% Nd. These monolithic low-doped Nd crystals can also be used without any doping or low doping at both ends.

In another aspect of the invention, a low doped Nd: YAG, Nd: YLF and Nd: YVO₄And (4) crystals. Nd: YAG or Nd: the crystal total length of YLF is at least 20 mm. Nd: YVO₄Has a total crystal length of at least 12 mm.

In another aspect of the present invention, the optical resonator 1 is designed such that the laser medium 8 is a TEM₀₀The size of the light spot of the mode is 0.8 mm-2.0 mm; the length of the optical resonant cavity 1 is 22 cm-100 cm or more, preferably 35 cm-100 cm, and for the design of the optical resonant cavity 1, commercial optical software such as GLAD can be used, and the design can also be designed according to the ABCD transmission matrix law. Typical TEMs of diode end-pumped solid-state lasers are currently available₀₀The mode spot size is 0.6mm or less and the optical cavity 1 is typically 20cm or less in length.

In another aspect of the present invention, particularly for Nd: YAG crystals using direct liquid cooled enclosures, currently polarized TEM₀₀Mode Nd: YAG laser generally adopts a conduction cooling mode, namely, a laser crystal is wrapped in a thin indium foil and then directly mounted in a heat conduction heat sink; the heat sink is cooled by liquid or air, and the size of the laser crystal is far larger than that of a laser spot in the crystal, namely, the laser spot is generally 6-10 times larger.

In another aspect of the present invention, a Nd-doped laser medium 8, such as Nd: YAG, Nd: YLF and Nd: YVO₄The cross-sectional diameter of the laser crystal is 1.6 to 5 times the diameter of the laser beam in the laser medium 8.

In another aspect of the present invention, a laser of second harmonic, third harmonic, fourth harmonic, or higher order harmonic can be implemented. When the second harmonic generator 22 is employed, the second harmonic generator 22, e.g., a type I or type II phase-matched nonlinear crystal, e.g., a LBO, BBO, KTP crystal, is located in the resonator in optical communication with the fundamental light beam, achieving high second harmonic optical conversion efficiency, when the third harmonic generator 16 is desired, both the second harmonic generator 22 and the third harmonic generator 16 are located in the resonator in optical communication with the fundamental light beam, and when the fourth harmonic generator 14 is desired, both the second harmonic generator 22, the third harmonic light beam, and the fourth harmonic generator 14 are located in the resonator in optical communication with the fundamental light beam, such harmonic lasers having increased efficiency and power.

In the aspect of harmonic generation of the utility model, I or II type phase matching nonlinear crystal is adopted for the second harmonic generation; the third harmonic generation adopts I or II type phase matching crystal; the fourth harmonic generation uses a type I phase matched crystal. In the type I phase-matching crystal that generates the second harmonic, the polarization state of the fundamental frequency beam is orthogonal to that of the generated second harmonic beam, and in the type I phase-matching crystal that generates the third harmonic, the polarization states of the fundamental frequency beam and the second harmonic beam incident on the type I phase-matching crystal are parallel to each other, and the third harmonic beam that is vertically polarized to the fundamental frequency beam and the second harmonic beam is generated. In a type II phase-matched crystal that generates a third harmonic, the polarization states of the fundamental beam and the second harmonic beam are orthogonal, and the polarization state of the generated third harmonic beam is parallel to the polarization state of one of the input beams. For example, the polarization states of the fundamental beam (1064nm) and the third harmonic beam (355mn) in type II LBO crystals will be parallel, and fourth harmonic conversion may also be achieved, suitable crystals include LiNBO3, BaNa (NbO)₃)、LiO₃、KDP、KTiOPO₄LBO, BBO or CLBO, etc., or other periodically poled nonlinear devices.

The utility model discloses an on the other hand can realize intracavity optical parametric oscillator, and I type or II type phase matching nonlinear crystal (for example LBO, BBO, KTP or KTA crystal) or other OPO generator 12 can communicate with fundamental frequency light beam optics in optical resonator 1, realize the high conversion efficiency from fundamental frequency light beam to OPO generator 12 output.

Fig. 1 shows an embodiment of the high power laser of the present invention. Between two reflecting surfaces, preferably between mirror one 4 and mirror two 6, an optical resonator 1 is formed, the mirror one 4 being partially reflective/partially transmissive for the fundamental beam, and it being possible for the fundamental beam to be reflected/partially transmittedServing as an output coupler for the laser. Ideally, mirror one 4 has about 85% reflectivity and 15% transmission for the fundamental beam. The intracavity fold mirror 5 is highly reflective for the fundamental frequency beam, an optical axis 3 is defined between the first mirror 4 and the second mirror 6, a laser medium 8 is located in the cavity between the first mirror 4 and the second mirror 6, preferably adjacent to the fold mirror 5, the laser medium 8 is preferably a laser crystal, and further preferably a Nd-doped laser crystal, such as Nd: YLF, Nd: YAG or Nd: YVO₄A laser crystal, and preferably a low doped Nd laser crystal. The diode pump pumps the laser medium 8LM end-pumped through the fold mirror 5. The folding mirror 5 is highly transparent to the pump beam. The folding mirror 5 reflects the light beam transmitted from the laser medium 8 to the first mirror 4 at an angle; and then the first reflector 4 reflects part of the light beam back to the folding reflector 5 and passes through the laser medium 8 again, the optical resonant cavity 1 is designed to enable the diameter of the light beam in the laser medium 8 to be 0.8-2 mm, and the diameter of the laser crystal is 1.6-4 times of that of the laser beam in the laser medium 8.

In operation, the front facet of the laser medium 8 is pumped by a diode pump source. The laser medium 8 is lased and fundamental frequency beams are propagated from the front end face and the rear end face of the laser medium 8. After being reflected by the second reflecting mirror 6, the fundamental frequency light beam generated by the laser medium 8 is guided back to the folding reflecting mirror 5 and passes through the laser medium 8; then reaches a first reflector 4, and a part of the first reflector is taken out of the cavity as the output of the laser; and another portion is reflected back to the fold mirror 5 and back to the lasing medium 8. The resulting laser thus has high power and high stability.

Fig. 2 discloses another embodiment of the high power laser of the present invention. Referring to fig. 2, an optical resonator 1 is formed between two reflecting surfaces, preferably between a mirror one 4 and a mirror two 6. Ideally, mirror one 4 is partially reflective and partially transmissive to the fundamental beam, although other percentages may be used, typically 85% reflectivity and 15% transmissivity is used. The second mirror 6 has high reflectivity for the fundamental frequency beam, and the laser medium 8 is located in the optical resonator 1 between the first mirror 4 and the second mirror 6, and preferably, the laser medium 8 is Nd: YLF, Nd: YAG or Nd: YVO₄And (4) crystals. For Nd: the YAG crystal is further preferably a low doped crystal doped at about 0.2% to about 0.8%, preferably at about 0.4% to about 0.6%. Preferably, the diameter of the laser crystal is 1.6-4 times of the diameter of the fundamental frequency beam in the crystal. A folding mirror 5 and a folding mirror 17 are arranged between the first mirror 4 and the second mirror 6 along the light path and are adjacent to the laser medium 8. The folding mirror 5 is at an angle to the longitudinal axis of the laser crystal and reflects the laser beam exiting the front face surface of the laser crystal at an acute angle, passing towards the first mirror 4 and exiting therefrom. Similarly, the first folding mirror 17 reflects the laser beam emitted from the rear end face of the laser medium 8 at an acute angle toward the second mirror 6. The diode pump source 13 is preferably adjacent to the fold mirror 5; preferably adjacent to fold mirror one 17. At least one brewster plate is inserted as polarization discriminator 10 between mirror one 4 and fold mirror one 17 or elsewhere in the optical path within optical cavity 1. The folding mirror 5 and the first folding mirror 17 are highly reflective for the fundamental beam and highly transmissive for the pump beam. The pump wavelength is specified or adjusted by the cooling temperature to match the absorption band of the lasing medium 8. For example, for Nd: YAG laser crystal, one of the absorption bands is about 808 nm; for Nd: YLF laser crystal, the absorption band is about 797nm, another is about 804 nm; for Nd: YVO₄The laser crystal has an absorption band of about 808 nm. The diameter of a fundamental frequency beam in the laser medium 8 is about 0.8 mm-2.0 mm through the design of the optical resonant cavity 1, and the polarization TEM₀₀And operating in the mode.

In operation, the diode pump source 13 generates a pump laser beam whose wavelength is phase-matched to the absorption band of the laser medium 8. After passing through the lens assembly, the pump beam is transmitted by fold mirror one 17 and fold mirror 5 and excites the laser medium 8. When properly aligned, the laser will lase at a preselected fundamental beam frequency: for example, for Nd: YAG crystal with frequency of 1064 nm. The fundamental frequency light beam exits from the front end face and the rear end face of the laser medium 8 and propagates along the optical axis 3. Is first reflected by fold mirror 5 to mirror one 4. On mirror one 4, a portion of the light beam is transmitted and another portion of the light beam is reflected. And then reflected back to the laser crystal by the folding mirror 5. Light propagating from the rear end face of the laser medium 8The beam is reflected by a first folding mirror 17; then passes through the polarization discriminator 10; and finally reflected by the first high-reflection mirror 4 back to the laser medium 8. The laser medium 8, such as Nd: the diameter of the fundamental frequency light beam in the YAG crystal is about 0.8 mm-2.0 mm. The diameter of the laser medium 8 is preferably about 1.6 to 4 times the diameter of the fundamental beam. In fig. 6, a schematic diagram of a laser crystal cooling jacket 7 is shown, which can directly cool a laser medium 8, such as Nd: YAG crystal. Ideally, Nd: the doping concentration of the YAG crystal LM is low, about 0.2% to 8%, preferably about 0.4% to about 0.6%. The laser is preferably in the TEM₀₀And operating in the mode.

Example 1

The specific configuration of the laser shown in fig. 2: two 30W fiber coupled diode lasers. The fiber coupled diode is output through an energy transmission fiber with the diameter of 0.8mm and the numerical aperture NA of 0.2. The pumping beam with the wavelength of 808nm is incident to the Nd: YAG laser crystal. The pump beam waist in the laser crystal is about 1mm in diameter. The laser medium 8 includes: central portion-0.5% Nd doped with phi 3mm × 30 mm: YAG crystal; undoped YAG crystals with two ends of 3mm x 5mm are respectively bonded to the doped crystals by diffusion. The total length of the crystal was 40 mm. As shown in fig. 6, a YAG crystal is mounted in the cooling jacket 7. Two O-rings and a stainless steel plate fix two ends of the YAG crystal. Nd throughout a 30mm length: YAG crystals are directly water-cooled. Water flows in from one end and out from the other. The total length of the optical cavity 1 is about 50 cm. Making TEM in YAG crystal by designing optical resonant cavity 1₀₀The mode spot diameter is about 0.9mm and the polarization discriminator 10 is a fused silica sheet polarization discriminator 10 set at about the brewster angle. Mirror one 4 is a partial reflector with 85% reflectivity at 1064nm, mirror two 6 is a high reflector with 99.9% reflectivity at 1064 nm. M3 and fold mirror one 17 were coated for high reflectivity at 1064nm (99.9%) and high transmission at 808nm (97%). The total pump power of the laser crystal is about 57W, the output power of the laser at 1064nm is 22W, and the polarization TEM is adopted₀₀Mode operation, from pump power to polarized TEM₀₀Conversion efficiency of mode output power was 38.5% and laser outputIs stable and reliable.

Example 2

The crystal size of the laser used in example 1 was changed to 4mm x 30mm, the doping concentration of 0.5% Nd was unchanged, and the undoped regions at both ends were 4mm x 5mm in size. All other descriptions are the same as example 1. We realized a 19.0W polarized TEM₀₀And (6) outputting the mode. Although the conversion efficiency was 31.6%, which is lower than that of example 1, the laser output was stable and reliable, and the mode quality was excellent.

On the other hand, the utility model discloses harmonic beam output can be realized to the laser instrument, as shown in fig. 3 ~ 5, the utility model discloses be particularly suitable for producing high power harmonic beam laser instrument, fig. 3 has given second harmonic generator 22 example, and under the ideal condition, laser medium 8 is the Nd: YAG, Nd: YLF or Nd: YVO₄An optical resonant cavity 1 is formed between a crystal, a first reflector 4 and a second reflector 6, and the first reflector 4 and the second reflector 6 both have high reflection on fundamental frequency beams-for Nd: YAG laser, its reflection wavelength is 1064nm, and mirror two 6 is also highly reflective for the second harmonic beam — for Nd: YAG laser with wavelength of 532 nm. A Q-switch 18 may be incorporated into the cavity, the Q-switch 18 being adjacent to the preferred first mirror 4, the Q-switch 18 being located anywhere in the cavity if space permits, lens assemblies being disposed between the diode pump source and the folding mirror 5 and between the diode pump source and the folding mirror 17, the laser medium 8 being pumped in the same manner as described with reference to fig. 1, the fundamental beam reflected from the first mirror folding mirror 17 propagating through a dichroic mirror 19, the dichroic mirror 19 being placed at or near the brewster angle of the fundamental beam; surface 10 of dichroic mirror 19 need not be coated with a film, and surface 12 of dichroic mirror 19 is coated with a high-reflection film for the second harmonic light beam and a high-transmission film for the P-polarized fundamental frequency light beam. If the angle of dichroic mirror 19 is not brewster' S angle, surface 10 of dichroic mirror 19 is also coated with a highly transmissive film of P-polarized fundamental frequency beam, which will facilitate oscillation of P-polarized fundamental frequency beam, thereby suppressing S-polarization and achieving polarization. The fundamental beam is directed through a second harmonic generator 22SHG, which is preferably a second harmonic nonlinear crystal, such as an LBO or BBO or KTP crystal or other nonlinear SHG generator, in which a portion of the fundamental light is passedThe beam is converted to a second harmonic beam. The second mirror 6 is highly reflective to both the fundamental beam and the second harmonic beam, and reflects the second harmonic beam and the fundamental beam through the crystal SHG, where a portion of the fundamental beam is converted to the second harmonic, and then the second harmonic beam generated by the second harmonic crystal SHG is reflected by the second mirror 6 to the second folding mirror 5, which second folding mirror 5 is also highly reflective to the second harmonic, and exits the cavity as the output of the laser. The fundamental frequency beam is transmitted by the second mirror 6, reflected by the first mirror 17, and amplified again through the laser medium 8.

Example 3

In the laser shown in fig. 3, dichroic mirror 19 is oriented at an angle of about 56 degrees with respect to the fundamental and second harmonic light beams, and face 12 of dichroic mirror 19 is coated with a highly reflective film having a wavelength of about 99.5% at 532nm for S polarization and a highly transmissive film having a wavelength of about 99.8% at 1064nm for P polarization, and face 10 of dichroic mirror 19 is uncoated. The base material of dichroic mirror 19 is fused silica having a thickness of about 1 mm. An acousto-optic Q-switch 18 is inserted into the cavity and placed at a Bragg angle so that the laser remains off when the continuous rf power supply is on. Dichroic mirror 19 functions similar to polarization discriminator 10, forcing the laser to operate as a fundamental beam of P-polarization, with mirror two 6 having a reflectivity of about 99.9% at both 1064nm and 532nm, SHG being a second harmonic producing LBO crystal of 3mm x 10mm size cut to critical phase matching to produce a second harmonic of 1064 nm; wherein, theta is 90 degrees, phi is 11.4 degrees; laser crystal Nd: YAG has a total pump power of about 57W, the laser is a polarized TEM at a Q-switch 18 repetition rate of 10kHz and a wavelength of 532nm₀₀The mode output power is 15W and the pulse width is 40ns (fwhm). The second harmonic generator 22 of this example is highly stable and reliable, and the laser can reliably operate at a repetition rate of single pulses 50kHz, in example 1, if the same Q-switch 18 is inserted in the optical cavity 1, a polarized TEM with a wavelength of 1064nm at a repetition rate of 10kHz₀₀The mode output power is 15W and the pulse width is about 50ns (fwhm). The conversion efficiency from fundamental beam power to second harmonic power is close to 100%. Thus it is aHigh efficiency, high power polarized TEM₀₀A direct second harmonic generator 22 of modes. Compared with the conventional second harmonic generator 22, the present invention has about twice the efficiency of the latter and better reliability and stability.

Fig. 4 adds to fig. 3 a third harmonic beam generating device THG, which is located between the SHG and the second mirror 6, in this example the second harmonic is generated using a type I phase-matched crystal and the third harmonic is generated using a type II phase-matched crystal. In a type I phase-matched second harmonic crystal, the polarization direction of the fundamental beam is perpendicular to the crystal axis ("o" light or ordinary light), and the polarization direction of the generated second harmonic beam is parallel to the optical axis 3 ("e" light or extraordinary light). In a type II phase matched third harmonic crystal, the fundamental and second harmonic beams are orthogonally polarized, producing a third harmonic beam with a polarization state parallel to the polarization state of one of the two input beams. For example, in a type II LBO crystal, the polarization states of the fundamental beam and the third harmonic beam are parallel.

The fundamental light beam is reflected by folding mirror one 17 to dichroic mirror 19, and dichroic mirror 19 is in optical communication with mirror two 6. Between dichroic mirror 19 and second mirror 6 are third harmonic generator 16THG and second harmonic generator 22SHG, and in optical communication with dichroic mirror 19 is folding mirror 5 two, which is highly reflective of the third harmonic light beam. In operation, the fundamental light beam is reflected by fold mirror one 17 and directed toward dichroic mirror 19, dichroic mirror 19 being highly transmissive to the P-polarized fundamental light beam, dichroic mirror 19 preferably being disposed at or near brewster's angle relative to the fundamental light beam propagating along optical axis 3. The surface 10 of the dichroic mirror 19 is not coated with a film, and the surface 12 of the dichroic mirror 19 is coated with a high-reflection film for the third harmonic light beam and a high-transmission film for the P polarization fundamental frequency light beam; if dichroic mirror 19 is set at an angle other than Brewster' S angle, then facet 10 is coated with a highly transparent film for the P-polarized fundamental beam, which will facilitate oscillation of the P-polarized fundamental beam, thereby suppressing S-polarization, achieving polarization operation, then the fundamental beam passes through third harmonic generator 16THG, which is preferably a third harmonic nonlinear crystal, most preferably a type II LBO crystal, since type II THG nonlinear crystal can convert only the fundamental beam and the second harmonic together into the third harmonic under phase matching conditions, and thus the third harmonic is not formed in the first pass of the fundamental beam through third harmonic generator 16, then the fundamental beam passes through second harmonic generator 22 where the fundamental beam is converted into the second harmonic, and then the second harmonic beam and the fundamental beam are reflected back to second harmonic generator 22SHG by mirror two 6, where another portion of the fundamental light beam is again converted to a second harmonic and then the fundamental light beam and the second harmonic are directed through third harmonic generator 16 where portions of the fundamental light beam and the second harmonic light beam are converted to a third harmonic and then the third harmonic light beam is reflected by surface 12 of dichroic mirror 19 to dichroic mirror 19, preferably with the second harmonic light beam being highly transmitted by dichroic mirror 19 and the third harmonic light beam being reflected by dichroic mirror 19 and directed as output out of the cavity, the fundamental light beam being transmitted through dichroic mirror 19 to fold mirror one 17 and then again amplified through laser medium 8.

Example 4

In the laser shown in fig. 4, surface 12 of dichroic mirror 19 is coated with a reflectivity of about 99% for 355nm wavelength P-polarized light and a transmissivity of about 99.8% for 1064nm wavelength P-polarized light, and for the incident fundamental frequency beam, the second and third harmonic beams are arranged at about 56 degrees, and surface 10 of dichroic mirror 19 is uncoated. The base material of dichroic mirror 19 is fused silica having a thickness of about 1 mm. Dichroic mirror 19 acts like polarization discriminator 10, forcing the laser to operate at a fundamental beam of P polarization. Laser crystal Nd: YG with a total pump power of about 57W, THG being a type II phase matched LBO crystal with dimensions 3mm x 15nm, laser polarized TEM at 355nm at Q-switch 18 repetition frequency of 10kHz₀₀The mode output power can reach 11W, the pulse width is 38ns (FWHM), the third harmonic generator 16 is highly stable and reliable, the laser can reliably work under the repetition frequency of single pulse-50 kHz, the efficiency from the fundamental frequency beam to the third harmonic output is about 70 percent, and the laser is a high-efficiency and high-power polarized TEM₀₀Mode direct third harmonic generator 16, with conventional external third harmonic generationThe efficiency of the device 16 is more than two times higher than that of the device, and the device has higher reliability and stability.

The utility model comprises a fourth harmonic generator 14, which adopts a second harmonic LBO crystal (critical phase matching or non-critical phase matching cutting) in the optical resonant cavity 1 for converting partial fundamental light beam into a second harmonic light beam, a II type phase matching third harmonic LBO nonlinear crystal (critical phase matching cutting) is also in the optical resonant cavity 1, the fundamental light beam from the laser gain medium is guided to pass through the I type phase matching second harmonic crystal in the resonant cavity, as a result, a part of the fundamental light beam is converted into a second harmonic light beam, the fundamental light beam and the second harmonic light beam are reflected back after passing through the I type phase matching second harmonic crystal, before the second harmonic light beam is converted into a higher harmonic light beam, the fundamental light beam is partially converted into a second harmonic light beam again, and then the obtained second harmonic light beam and the residual fundamental light beam are guided to the II type third harmonic LBO nonlinear crystal, when the fundamental light beam and the second harmonic light beam pass through, the crystal converts a part of the fundamental light beam and a large part of the second harmonic light beam into a third harmonic light beam, then, when the third harmonic light beam and the unconverted fundamental light beam are guided through an I-type fourth harmonic LBO crystal (critical phase matching cut), the fourth harmonic crystal converts a part of the fundamental light beam and a part of the third harmonic light beam into a fourth harmonic light beam, then, the obtained fundamental light beam, second harmonic light beam, third harmonic light beam and fourth harmonic light beam are guided to a dichroic mirror 19, and the fourth harmonic light beam and the fundamental light beam are separated by the dichroic mirror 19 and then guided out of the time resonant cavity as the output of the laser. Alternatively, a second ultraviolet separator may be placed between first dichroic mirror 19 and lasing medium 8 to block any ultraviolet light beams that may pass through lasing medium 8 and then direct the fundamental light beam back through lasing medium 8 for amplification, optionally with both unconverted fundamental light beam and second harmonic light beam back through lasing medium 8 to improve its efficiency.

Fig. 5 is similar to fig. 4 except that fourth harmonic generator 14FHG is provided between third harmonic generator 16THG and dichroic mirror 19, and dichroic mirror 19 is provided between first folding mirror 17 and second mirror 6, FHG being in optical communication with dichroic mirror 19 and second mirror 6, THG being in optical communication with FHG, and SHG being in optical communication with THG. In operation, the fundamental light beam is directed toward dichroic mirror 19, which dichroic mirror 19 is highly transmissive to the P-polarized fundamental light beam, dichroic mirror 19 is preferably disposed at or near brewster 'S angle relative to the fundamental light beam propagating along optical axis 3, surface 10 of dichroic mirror 19 is uncoated, surface 12 of dichroic mirror 19 is coated with a highly reflective film for the fourth harmonic light beam and a highly transmissive film for the P-polarized fundamental light beam, if dichroic mirror 19 is not disposed at brewster' S angle, then surface 10 can be coated with a highly transmissive film for the P-polarized fundamental light beam, which will favor the P-polarized fundamental light beam and will distinguish the S polarization. Thus, the laser will operate in optical cavity 1 substantially with P-polarization, optionally, fold mirror 5 two will separate the fourth harmonic beam from the second and third harmonic beams, the P-polarized fundamental beam passing through dichroic mirror 19 and entering fourth harmonic generator 14FHG, which is preferably a class I phase matched fourth harmonic nonlinear crystal LBO that converts the third harmonic beam to the fourth harmonic beam in the presence of the fundamental beam, unaffected when the fundamental beam first passes through the FHG, unaffected when the fundamental beam then propagates through the THG, passes through the SHG, wherein a portion of the fundamental beam is converted to the second harmonic beam, the second and fundamental beams are then reflected by mirror two 6, passes through the SHG for a second time, wherein another portion of the fundamental beam is converted to the second harmonic beam, and thereafter, as the second and fundamental beams pass through the THG, part of the fundamental light beam and the second harmonic are converted into the third harmonic, the light beam propagated by the THG is then guided through the FHG, where the fourth harmonic light beam and part of the fundamental light beam are converted into the fourth harmonic light beam, which is then propagated to dichroic mirror 19, where the fundamental light beam is transmitted back to laser medium 8 for amplification; and the fourth harmonic light beam is reflected by dichroic mirror 19 and folding mirror 5 and guided out of the cavity.

Referring to fig. 6, a direct water-cooled laser medium 8 module is used, and other cooling fluids, Nd: YAG crystal with total length of 30mm, diameter of 3mm and middle partA portion of Nd was doped with 0.5% and had 5mm long undoped regions at both ends, alternatively, the undoped regions may be formed of a low-doped Nd: YAG crystal, for example, about 0.1% doped, both optical crystal surfaces are coated with antireflection films for the laser wavelength and the pump wavelength, the crystal is prepared using diffusion bonding technique, the laser crystal is water-cooled directly on all surfaces except for both end surfaces perpendicular to the optical axis 3, water enters from one end and exits from the other end, undoped or about 0.1% doped YAG crystal end surfaces are fixed and sealed using O-rings and stainless steel plates, water inlet and outlet ports are not shown (below), the cooling jacket 7 eliminates mechanical mounting stresses associated with conduction cooling, which for Nd: YAG lasers are particularly important because mechanical stress, in addition to thermally induced stress, can lead to high efficiency/high power linearly polarized TEM₀₀Mode lasers are unreliable in operation and additionally, the undoped and lowly doped regions produce surprisingly superior results-this is in contradiction to the conventional view of seeking high coupling efficiency, high absorbed pump power, and smaller crystal diameters also produce higher output power and better stability. Nd: YVO₄And Nd: YLF laser crystals can also improve output power, efficiency and reliability with similar cooling, low doping and smaller diameter designs.

Referring to the conduction cooling module design of fig. 7 and 8, three segments of bonded Nd: YLF crystal, laser crystal 30 doped with 0.4% Nd and having dimensions of 4mm x 7mm, laser crystal 31 doped with Nd at a concentration of 1% and having dimensions of 4mm x 20mm, three crystals were aligned along the "c" axis and wrapped with 125 μm thick indium foil, then Nd: YLF crystals are mounted directly in the copper heat sink module, cooled by water flow, now referring to Nd in fig. 3: YLF laser with spot size of about 1.0mm for fundamental beam, total pump power of 57W from two 30W fiber coupled diodes with center wavelength of 804nm, and linear polarization TEM₀₀The continuous wave output fundamental frequency power can reach 23W, the conversion efficiency is about 40 percent, and under the repetition frequency of 3kHz, the second harmonic TEM₀₀The mode output power is about 14W, and the laser is efficient, stable and reliable.

Referring again to fig. 8 and 1, Nd was pumped using a 30W single fiber coupled diode pumped laser: YVO₄The laser has a pumping center wavelength of about 808nm, a laser beam spot size designed to be about 0.9mm in diameter, and a laser beam spot size of 3mm × 3mm × 15mm doped with Nd with a doping concentration of 0.3%: YVO₄Crystals were wrapped in indium foil 100 μm thick, and as shown in fig. 7, the Nd: YVO₄The crystal is directly arranged in the copper heat sink module, and the heat sink module is cooled by leading water to flow in from one end and flow out from the other end, so that the 14.5W linear polarization TEM can be realized under the pumping power of 29W₀₀Mode output power, 50% conversion efficiency, and producing a polarized TEM at a repetition rate of 20kHz when the laser is operated in the Q-switched state₀₀A polarized TEM of 532nm at a repetition frequency of 20kHz has been achieved with an 11W average output power with a mode pulse width (FWHM) of 30ns using the second harmonic cavity in FIG. 3₀₀Mode second harmonic output power 11W, pulse width 25ns, conversion efficiency from fundamental beam to second harmonic beam is again 1: 1, this is a highly efficient, stable laser.

The utility model discloses a direct water-cooling is preferred to laser crystal, especially to polarization TEM₀₀High efficiency Nd of mode: YAG high power laser, as mentioned before, preferably a low doped laser medium 8, in direct contact with water through a cooling jacket 7, the laser medium 8 preferably being a laser crystal, most preferably a rod or bar Nd: YAG crystal, ideally Nd: the YAG rod has a low Nd doping concentration, or Nd doping, of from 0.2% to 0.8%, or a plurality of regions of Nd doping, in which case the doping level increases with increasing distance from the pump laser, preferably the laser medium 8 has at least two regions with different doping levels in the two regions, in particular a first region with a doping concentration of a preselected level, a second region between the first region and the first pump laser with a lower doping concentration than the first region, the doping level in the second region being 5% to 70% of the doping level in the first region. When pumping the laser medium 8 from both ends, the laser medium 8 preferably comprises a third region having a lower doping concentration than the first region, and a second pump laser, desirably, the doping level in the third region is 5% ~ to ℃ of the doping level in the first region70% of the liquid cooling module, the lower doped end can also be undoped with any active ions.

In fig. 7, a three-segment Nd is used: YAG crystal. The central region is doped at about 0.4% to about 0.6%, while the crystal segment near the pump laser is doped at about 0.1% to about 0.2%, preferably about 0.1%, and may be undoped. The end part of the crystal is provided with the crystal which is not doped or is doped with Nd and has lower concentration, so that the thermal stress in the crystal can be reduced, and the thermal distribution is more uniform; and also serves to shrink the cooling jacket 7 and secure the laser rod in place.

On the other hand, the present invention includes an intracavity optical parametric oscillator, particularly suitable for generating high power mirror one 4 and mirror two 6 outputs, as shown in fig. 10, where the laser medium 8 is Nd: YAG, Nd: YLF or Nd: YVO4, an optical resonator 1 is formed between the reflecting surfaces of the first mirror 4 and the second mirror 6, the first mirror 4 and the second mirror 6 both highly reflect the fundamental frequency beam, and for Nd: YAG laser, with mirror wavelength of 1064nm, mirror one 4 highly reflective for the preselected signal wave of OPO generator 12, transmissive for the idler wave, in the example given idler wave 2602nm, signal 1800nm, or mirror two 6 partially reflective for the signal wave, thereby serving as an output coupler for OPO generator 12, an optional Q-switch 18 may be employed within the cavity, the Q-switch 18 preferably being adjacent to mirror one 4, and also located anywhere in the cavity as desired, the fundamental light beam reflected from fold mirror one 17 being directed through a dichroic mirror 19, the dichroic mirror 19 being set at or near the brewster angle of the fundamental light beam, the surface 10 of dichroic mirror 19 being uncoated, the surface 12 of dichroic mirror 19 being highly reflective for the signal wave and highly transmissive for the fundamental light in P polarization, if the setting of dichroic mirror 19 is not at brewster angle, its surface 10 may also be coated with a highly transparent film of P-polarized fundamental light, which will favor the P-polarized fundamental beam and will distinguish the S-polarization. Thus, the laser will operate in optical cavity 1 with substantially P-polarization, mirror one 4 being partially reflective and partially transmissive for the signal wave and transmissive for the idler wave, the OPO optical cavity 1 being formed between mirror one 4 and mirror two 6, the fundamental beam being directed through a non-linear OPO generator 12, the non-linear OPO generator 12 preferably being a non-linear crystal, such as a LBO, BBO, KTP, KTA crystal or any other suitable crystal, a portion of the fundamental beam being converted into a signal wave and an idler wave under phase matching conditions according to a "laser fundamental frequency light frequency-signal wave frequency + idler frequency" relationship, the output signal frequency being controllable by controlling the non-linear crystal angle or temperature, another portion of the fundamental beam being converted into a signal wave and an idler wave after the laser fundamental beam and the OPO signal beam have been reflected back into the non-linear OPO crystal, the laser fundamental frequency beam reaches laser medium 8 through dichroic mirror 19 for further amplification, and the signal wave will oscillate between folding mirror 5 two and mirror 6 two and generate an output through dichroic mirror 19. The laser fundamental beam acts as a pump beam for the OPO. In this configuration, the laser fundamental frequency beam is not wasted.

The present invention and the embodiments thereof have been described above, but the description is not limited thereto, and the embodiment shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. In summary, those skilled in the art should understand that they should not be limited to the embodiments described above, and that they can design the similar structure and embodiments without departing from the spirit of the invention.

Claims

1. A high power laser characterized by: including optical resonator, harmonic generating device, optical axis, speculum one, folding speculum, speculum two and cooling jacket, optical resonator locates between speculum reflection surface and the speculum two reflection surfaces, the optical axis is located in the optical resonator, harmonic generating device locates on the optical axis, folding speculum is located between speculum one and the speculum two and is close to harmonic generating device, harmonic generating device locates in the cooling jacket.

2. A high power laser according to claim 1, wherein: the optical resonant cavity is arranged in TEM₀₀Mode operation。

3. A high power laser according to claim 1, wherein: the harmonic generation device comprises a laser medium and a pump laser device.

4. A high power laser according to claim 1, wherein: the harmonic generation device comprises a laser medium, a pumping laser device, a first folding reflector and a polarization discriminator.

5. A high power laser according to claim 1, wherein: the harmonic generation device comprises a laser medium, a pumping laser device and a multi-harmonic generation device.

6. A high power laser according to claim 1, wherein: the harmonic generation device comprises a laser medium, a pumping laser device, a first folding reflector and an OPO generator.

7. A high power laser according to any of claims 3-6, characterized in that: the laser medium is arranged in an optical resonant cavity between the first reflecting mirror and the second reflecting mirror and is close to the folding reflecting mirror, the laser medium is provided with a front end face and a rear end face, the laser medium generates fundamental frequency beams transmitted from the front end face and the rear end face, the diameter of the fundamental frequency beams is 0.8-2.0 mm, and the diameter of the laser medium is 1.6-5 times of the diameter of the fundamental frequency beams.

8. A high power laser according to claim 4 or 6, wherein: the first folding reflector is arranged in an optical resonant cavity between the first reflector and the second reflector and is close to the laser medium.

9. A high power laser according to any of claims 3-6, characterized in that: the pumping laser device is arranged on the outer side, opposite to the folding reflector, of the laser medium and comprises a diode pumping source and a lens assembly, the lens assembly is arranged on the outer side of the folding reflector and the outer side of the folding reflector respectively, and the diode pumping source is arranged on the outer side of the lens assembly.

10. A high power laser according to claim 6, characterized in that: the OPO generator is a nonlinear crystal.

11. A high power laser according to claim 4, characterized in that: the polarization discriminator is arranged between the first folding reflector and the second reflector, and the polarization discriminator is a Brewster plate.

12. A high power laser according to claim 5, characterized in that: the multi-time harmonic generation device comprises a Q switch, a dichroic mirror, a multi-time harmonic generator and a reflecting mirror III, wherein the Q switch is arranged between the reflecting mirror I and the folding reflecting mirror, the dichroic mirror is arranged between the folding reflecting mirror I and the reflecting mirror II, the multi-time harmonic generator is arranged between the dichroic mirror and the reflecting mirror I, and the reflecting mirror III is arranged close to the dichroic mirror.

13. A high power laser according to claim 12, wherein: the multiple harmonic generator comprises a second harmonic generator.

14. A high power laser according to claim 12, wherein: the multiple harmonic generator comprises a second harmonic generator and a third harmonic generator.

15. A high power laser according to claim 12, wherein: the multiple harmonic generator comprises a second harmonic generator, a third harmonic generator and a fourth harmonic generator.

16. A high power laser according to any one of claims 13, 14 and 15, wherein: the second harmonic generator is a second harmonic nonlinear crystal, and the second harmonic nonlinear crystal is an I or II type phase matching nonlinear crystal.

17. A high power laser according to claim 14 or 15, wherein: the third harmonic generator is a third harmonic nonlinear crystal, and the third harmonic nonlinear crystal is an I or II type phase matching nonlinear crystal.

18. A high power laser according to claim 15, wherein: the fourth harmonic generator is a fourth harmonic nonlinear crystal, and the fourth harmonic nonlinear crystal is a class I phase-matched fourth harmonic LBO nonlinear crystal.

19. A high power laser according to claim 2, wherein: the length of the optical resonant cavity is 22 cm-100 cm.

20. A high power laser according to claim 2, wherein: the length of the optical resonant cavity is 35 cm-100 cm.