CN218070536U

CN218070536U - High-power nanosecond intracavity quintupling frequency laser

Info

Publication number: CN218070536U
Application number: CN202222309912.XU
Authority: CN
Inventors: 朱光
Original assignee: Tianjin Light Particle Technology Development Co ltd
Current assignee: Tianjin Light Particle Technology Development Co ltd
Priority date: 2022-09-01
Filing date: 2022-09-01
Publication date: 2022-12-16
Anticipated expiration: 2032-09-01

Abstract

The utility model discloses a five times frequency laser in high power nanosecond intracavity. The utility model has the advantages that the four high-power laser diode modules pump two laser crystals respectively to form a high-power high-repetition-frequency laser cavity, so that the fundamental frequency laser in the cavity has the characteristics of high repetition frequency, large pulse energy, excellent beam quality and the like; and then the beam size at the position of the frequency summation crystal in the cavity is controlled by using the combination of a lens and the cavity mirror, and the frequency summation of the fundamental frequency light and the quadruple frequency light in the cavity is realized by using the characteristic of high peak power in the cavity, so that the output of the quintuple frequency laser in the solid nanosecond cavity is finally realized. Utilize the utility model discloses can be very light acquire intracavity quintupling frequency laser of 1um wave band laser, overcome quintupling frequency laser and produced and need the picosecond, complicated devices such as femto second or high energy laser can high-efficient reliable production high power nanosecond intracavity quintupling frequency laser, have high application prospect.

Description

High-power nanosecond intracavity quintupling frequency laser

Technical Field

The utility model relates to the laser field especially involves the design of the higher frequency doubling laser instrument of solid nanosecond, the utility model discloses a high power nanosecond intracavity frequency doubling laser instrument.

Background

In recent years, the development of all-solid-state ultraviolet and deep ultraviolet lasers has been promoted, which mainly benefits from the wide application prospect and the potential huge market value. From microlithography to marking identification, from semiconductor wafer detection, to biomolecule sequencing, from information storage to security medicine, the use of ultraviolet and deep ultraviolet lasers plays irreplaceable roles in these fields.

The solid deep ultraviolet at the present stage is mainly generated by concentrating the frequency summation outside the cavity for many times, so that a high-power fundamental frequency laser is needed, and the frequency doubling efficiency is not high. In order to better solve the efficiency problem of the deep ultraviolet solid nanosecond quintupling frequency laser, a high-power nanosecond intracavity quintupling frequency laser is specially designed.

Disclosure of Invention

For picosecond ultraviolet and femto second ultraviolet laser, the utility model relates to a simple structure, solid nanosecond quintupling frequency laser that the reliability is high. The intracavity sum frequency technology fully utilizes the characteristic of high peak power in the cavity and utilizes the multiple frequency multiplication sum frequency of the fundamental frequency light to generate the quintuple-frequency laser. Compared with a nanosecond cavity sum frequency scheme, under the condition of the same pumping power, the cavity sum frequency technology does not need to converge light spots, and the space coincidence degree is high, so that the complex structure of the cavity sum frequency is simplified, and the purpose of efficiently outputting quintupled frequency laser is achieved.

In order to achieve the purpose, the design of the high-power nanosecond intracavity quintupling frequency laser is characterized in that the laser is mainly constructed into three parts, namely a high-power pumping system, a high-power nanosecond laser cavity and a sum frequency component.

The high-power pumping system is formed by converging four high-power optical fiber coupling modules in a first laser crystal (14) and a second laser crystal (24) through a first coupling system (151), a second coupling system (152), a third coupling system (251) and a fourth coupling system (252). The pumping system adopts 878nm or 888nm pumping light for reducing the quantum loss of the laser crystal and generating extremely high pumping power. The pumping power of each module is required to be more than 100W, and high-power pumping light is utilized to realize high-power fundamental frequency laser.

The high-power nanosecond laser cavity can generate high-power nanosecond fundamental frequency laser, and the high-power nanosecond laser cavity is characterized by sequentially comprising a total reflection mirror (11), a Q-switch (12), a first low-pass lens (131), a first laser crystal (14), a second low-pass lens (132), a third low-pass lens (231), a second laser crystal (24), a fourth low-pass lens (232), a lens (25), a dichroic mirror (22) and a multipoint reflecting mirror (21). From the total reflection mirror (11) to the multipoint reflection mirror (21), the laser in the cavity passes through the devices in sequence and oscillates in the cavity to form laser.

Further, in the laser cavity, the first laser crystal (14) and the second laser crystal (24) are neodymium-doped particle crystals, the length of the laser crystals is about 50mm, the neodymium-doped particle crystals are used for completely absorbing pump light, and the corresponding crystal concentration is adjusted according to design.

Further, in the laser cavity, the first low-pass lens (131), the second low-pass lens (132), the third low-pass lens (231) and the fourth low-pass lens (232) can be plano-convex or lenses with corresponding curvatures, the curvature of the lens and the coating requirements are adjusted according to the design requirements, and the main purpose is to compensate the thermal focal length of the crystal. The dichroic mirror (22) reflects the fundamental frequency light at the edge position, emits the higher order frequency doubling light at the side position, and transmits the frequency doubling light at the middle position inside the lens.

The further lens (25) is a fundamental frequency optical lens, the fundamental frequency optical lens and the multipoint reflector (21) form a light beam control system, and the focal length of the lens (25), the curvature of the multipoint reflector (21) and the distance between the focal length and the curvature of the multipoint reflector (21) are designed, so that the spot size between the lens (25) and the multipoint reflector (21) can be accurately controlled, and subsequent frequency doubling and sum frequency are facilitated.

The sum frequency component comprises a frequency doubling crystal (31), a frequency quadrupling crystal (32) and a frequency quintupling crystal (33), and light returning from the multipoint reflector (21) sequentially passes through the frequency doubling crystal (31), the frequency quadrupling crystal (32) and the frequency quintupling crystal (33) to generate frequency quintupling laser output.

Further in the sum frequency component, controlling the spot size and crystal length in the crystal can reduce the effect of the walk-off effect on power.

In the sum frequency component, the emergent end face of the quintupling frequency crystal (33) is cut and distributed with angles for separating emergent light from other light beams.

Further, in the sum frequency assembly, all sum frequency crystals are placed in a heat sink with TEC temperature control, and the corresponding frequency doubling and sum frequency process is realized through TEC accurate temperature control.

Further, in the final light emitting light path, quintuple frequency light (40) in the emitting light is emitted according to the corresponding light path, the rest of the quintuple frequency light (42) and the quadruplicate frequency light (41) enter the corresponding second stray light collecting device (342) and the first stray light collecting device (341), and the fundamental frequency light (43) returns in the original path.

Drawings

Fig. 1 is a schematic structural diagram of the present invention.

Fig. 2 is a schematic beam splitting diagram of the outgoing laser beam.

Detailed Description

The utility model discloses an overall structure is as shown in figure 1, and the laser main part is a four pump high power end pumping solid laser of bicrystal, utilizes the high peak power characteristics of intracavity to come the frequency sum many times and produce five times frequency deep ultraviolet nanosecond laser.

The high-power nanosecond intracavity quintupling frequency laser is characterized in that the laser is mainly constructed into three parts, namely a high-power pumping system, a high-power nanosecond laser cavity and a sum frequency component.

The high-power pumping system is formed by converging four high-power optical fiber coupling modules in a laser crystal through a first coupling system (151), a second coupling system (152), a third coupling system (251) and a fourth coupling system (252), wherein a pumping source pumps the crystal by 888nm light, and the high-power pumping system is mainly used for reducing quantum loss, thermal lens effect and the like. The pumping power of each fiber coupling module needs to be larger than 100W, the fiber core diameter is 400um, the coupling ratio of the corresponding coupling system is 1. The optical fiber coupling module can select a wavelength locking module for reducing the influence of temperature change on the overall light output power.

The high-power nanosecond laser cavity is characterized by comprising a total reflection mirror (11), a Q-switch (12), a first low-pass lens (131), a first laser crystal (14), a second low-pass lens (132), a third low-pass lens (231), a second laser crystal (24), a fourth low-pass lens (232), a lens (25), a dichroic mirror (22), a multipoint reflecting mirror (21) and the like, and is a cavity of fundamental laser. From the total reflection mirror (11) to the multipoint reflection mirror (21), the intracavity fundamental frequency laser passes through the devices in sequence and oscillates in the cavity in a reciprocating mode.

Total reflection mirror (11) the utility model discloses use the monochromatic dielectric film of 1064nm to realize the reflection function of fundamental frequency light, reflection angle is 0.

The Q-switch (12) is used to store and release energy for generating pulsed energy, preferably driven with a 1.5mm active area, 41M RF frequency, 20W RF power.

Wherein, first low pass lens (131), second low pass lens (132), third low pass lens (231), fourth low pass lens (232) are in the utility model discloses in can use plano-convex low pass lens, mainly used sees through the pump light, reflects fundamental frequency light, the thermal effect of compensation crystal simultaneously. The overall dimensions and coating parameters of the four lenses can be consistent, wherein the coating parameters are preferably 888nm high-transmittance and 1064nm high-reflectance lenses, the reflection angle is 13 degrees, and the corresponding curvature is determined according to parameters such as the overall cavity length, the spacing, the crystal thermal focus and the like.

The first laser crystal (14) and the second laser crystal (24) are laser working crystals, the utility model uses Nd: YVO4 crystal to realize functions, and has the advantages of high repetition frequency, polarization output and the like. The recommended corresponding parameters are 4 x 50 crystal size, 0.5% crystal concentration, and the high transmittance of 888nm and 1064nm is adopted for the coating, wherein the crystals are not limited to Nd: YVO4 crystals, and the crystals with the same property have the same protection range.

The dichroic mirror (22) is used for changing the propagation direction of the fundamental frequency light and emitting frequency doubling light, the coating parameters of the dichroic mirror are 532nm high-transmittance and 1064nm high-reflectance lenses, and the lateral position of the dichroic mirror is used for reflecting the fundamental frequency light and enabling the fundamental frequency light to continue to oscillate in the cavity.

The lens (25) and the multipoint reflector (21) are matched for use, so that a light beam size control function can be realized, the light spot size between the lens (25) and the multipoint reflector (21) can be accurately controlled by designing the focal length of the lens (25), the curvature of the multipoint reflector (21) and the distance between the focal length of the lens (25) and the curvature of the multipoint reflector (21), the frequency doubling efficiency can be optimized, and the light output power can be improved. The utility model discloses well lens (25) use plano-convex lens, plate the high transparent film system of 1064nm, and plano concave or plano lens are used in multiple spot speculum (21), and the coating adopts 1064nm and 532nm high reflection scheme for reflect fundamental frequency light and frequency doubling light, distance between the two is adjusted according to the designing requirement.

The sum frequency component consists of three crystals, namely a frequency doubling crystal (31), a frequency quadrupling crystal (32) and a frequency quintupling crystal (33), wherein the light-emitting position of the frequency quintupling crystal (33) is cut and subjected to angle distribution.

The corresponding frequency doubling process in the crystal is that the fundamental frequency light reflected from the multipoint reflector (21) firstly passes through the frequency doubling crystal (31) and is subjected to phase matching to generate frequency doubled laser, the frequency doubled laser continuously passes through the frequency quadrupling crystal (32), the phase matching is performed in the frequency quadrupling crystal (32) to generate frequency quadrupled laser, the frequency quadrupled light after passing through the frequency quadrupling crystal (32) and the residual fundamental frequency light are subjected to sum frequency in the frequency quintupling crystal (33) and are subjected to sum frequency quintupling laser, and finally the laser is emitted at the angle distribution position.

The final emergent light is double-frequency light, quadruple-frequency light and quintuple-frequency light. Wherein fundamental frequency light returns the cavitation according to former way, and two, quadruple frequency light are stray light, enter into first stray light collector (341) respectively, in second stray light collector (342), and quintupling frequency light is then the utility model discloses the laser of needs is exported according to confirming the position.

The crystal cutting and deflection directions are explained below. In the present invention, the first laser crystal (14) and the second laser crystal (24) are Nd: YVO4 birefringent crystals, and the direction of the C axis is perpendicular to the paper surface, so that the polarization direction of the fundamental frequency light is perpendicular to the paper surface.

When the fundamental frequency light passes through the frequency doubling crystal (31), the frequency doubling crystal uses LBO crystal, I-type phase matching is used for frequency doubling, the polarization direction of frequency doubled light is parallel to the paper surface, and the parameter of the frequency doubling crystal is Theta =90; phi =10.8, crystal size 3 x 16, the crystals were ambient temperature crystals.

When the frequency-doubled light continuously transmits through the quadruple frequency crystal (32), the quadruple frequency crystal (32) is a BBO crystal, and the BBO crystal has the advantages of large nonlinear coefficient, short ultraviolet cutoff wavelength and the like. However, because the BBO crystal has a strong absorption to deep ultraviolet and a large walk-off effect, the crystal length is usually not too long in order to take sum frequency efficiency and beam quality into account. When the frequency-doubled light passes through the quadruple frequency crystal (32), I-type phase matching is used, the polarization direction of the quadruple frequency light is the direction vertical to the paper surface, and the parameter of the quadruple frequency crystal (32) is Theta =47; phi =0, crystal size 3 x 4, normal temperature crystals.

And finally, performing class I phase matching on the quadruple frequency light and the fundamental frequency light polarized perpendicular to the paper surface after passing through a quintupling frequency crystal (33), and generating quintupling frequency laser after frequency summation, wherein the quintupling frequency crystal (33) is also a BBO crystal, the crystal cutting parameter is Theta =51.2, phi =0, the crystal size is 3 x 10, and the crystal is a normal-temperature crystal. The polarization direction of the quintupled frequency light which is finally output is in the paper surface, and when the polarized light in the paper surface is emitted through the angle distribution, the power loss is minimum. All crystals are placed in a heat sink with accurate temperature control of the TEC, and five-fold frequency light power of the emergent light can be finally maximized by optimizing the temperature.

In a quintupling crystal (33), temporal and spatial walk-off can have an effect on the sum frequency efficiency. The time walk away because fundamental frequency light and quadruple frequency light are getting into quintupling frequency crystal (33) around the dispersion in time, but the utility model discloses well laser pulse width is 20ns of orders, need the optical path difference of two bundles of light to produce essential influence to sum frequency efficiency at m level according to the time conversion, and in shorter quadruple frequency crystal (32), the optical path difference of crystal to the difference of fundamental frequency light and quadruple light can be ignored.

The spatial walk-off is mainly due to the dispersion of fundamental frequency light and quadruple frequency light on the spatial position when the fundamental frequency light and the quadruple frequency light enter the quintupled crystal (33), the beam diameter is properly controlled through a beam control system, the frequency doubling efficiency can be improved, and the walk-off distance accounts for the proportion of the whole light spot after the light passes through each crystal. Secondly, the frequency doubling crystal (31) is LBO, the corresponding walk-off angle is small, even if the size is long, the corresponding walk-off distance is small, so the long LBO is used for increasing the frequency doubling conversion efficiency as far as possible under the condition that the walk-off ratio is controllable, the frequency quadrupling crystal (32) uses BBO with short distance, relatively speaking, the walk-off angle of the BBO crystal is large, the walk-off between the frequency quadrupling light and the base frequency light can affect the sum frequency of the frequency quintupling crystal, the front-end frequency doubling crystal can perform efficient frequency conversion as far as possible, the short frequency quadrupling crystal is adopted, the effect of the frequency quadrupling walk-off on the final sum frequency efficiency is reduced, and although the frequency quadrupling efficiency is reduced, the whole light-emitting efficiency is improved. Meanwhile, high-power frequency doubling light and quadruple frequency light are obtained through extremely high-power pumping, and even if quadruple frequency light and fundamental frequency light are separated, high-power nanosecond quintuple frequency doubling laser can be output in a quintuple frequency crystal in a frequency doubling mode.

YVO4, frequency-doubling crystal LBO, frequency-quadrupling crystal BBO, and frequency-quintupling crystal BBO are taken as examples to illustrate the corresponding light-emitting situation, wherein the frequency-doubling light is e light in the frequency-quintupling crystal (33), the corresponding refractive index is 1.598, the base frequency light is o light in the frequency-quintupling crystal (33), the corresponding refractive index is 1.654, the frequency-quadrupling light is o light in the frequency-quintupling crystal (33), the corresponding refractive index is 1.758, the frequency-quintupling light is e light in the frequency-quintupling crystal (33), and the corresponding refractive index is 1.736.

After the angle distribution, the refractive index of the double-frequency light (42) is minimum, the double-frequency light passes through the dichroic mirror (22) and enters the second stray light collecting device (342), the fundamental-frequency light (43) is reflected back to the cavity on the dichroic mirror (22) to continue oscillation, the refractive index of the quadruple-frequency light (41) is maximum, the refractive index of the quadruple-frequency light is output to the first stray light collecting device (341) from the side face of the dichroic mirror (22), and the quintupling-frequency light (40) exits the laser according to design requirements.

If special requirements are needed for subsequent light beam application, a shaping device can be added to adjust the shape of the light beam.

The utility model discloses utilize the high characteristics of intracavity peak power, carry out frequency doubling and sum frequency many times in the intracavity, the five frequency doubling deep ultraviolet laser of final output high power nanosecond have extensive market prospect and value, develop new direction for deep ultraviolet laser's research and development.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, a plurality of improvements and decorations can be made without departing from the principle of the present invention, and these improvements and decorations should also be regarded as the protection scope of the present invention.

Claims

1. The utility model provides a five-fold frequency laser in high power nanosecond intracavity which characterized in that includes the high power pumping source, high power nanosecond laser cavity, sum frequency subassembly, wherein high power nanosecond laser cavity includes total reflection mirror (11) in proper order, Q opens light (12), first low pass lens (131), first laser crystal (14), second low pass lens (132), third low pass lens (231), second laser crystal (24), fourth low pass lens (232), lens (25), dichroic mirror (22), multiple spot speculum (21), wherein sum frequency subassembly includes frequency doubling crystal (31), frequency doubling crystal (32), frequency doubling crystal (33) quintupling, the final emergent light enters into stray light collection device and collects.

2. The high-power nanosecond intracavity five-time frequency laser as claimed in claim 1, comprising a high-power pumping source, wherein the high-power pumping source works for four high-power pumping light pumping double crystals, and the high-power fundamental laser is realized by using light with pumping power larger than 100 watts 888nm as pumping light.

3. The high power nanosecond intracavity quintupling laser according to claim 1, characterized by comprising a dichroic mirror (22), said dichroic mirror (22) being a low pass filter, with edge positions reflecting fundamental light, lateral positions for the emission of quadruple and quintuplex light, and a middle position transmitting the doubled light.

4. The high power nanosecond intracavity fivefold frequency laser according to claim 1, characterized by comprising a lens (25), a multipoint mirror (21), said lens (25), multipoint mirror (21) constituting the beam control means, by controlling the focal length and curvature of the lens (25) and multipoint mirror (21), and the distance between them, the spot size between them can be precisely controlled.

5. The high power nanosecond intracavity quintupling frequency laser device as claimed in claim 1, comprising a sum frequency module in which crystals are all placed in a heat sink with TEC temperature control, and the respective frequency doubling and sum frequency processes are realized by TEC precise temperature control.

6. The high power nanosecond intracavity quintupling frequency laser as claimed in claim 1, comprising a sum frequency module in which the effect of walk-off on the output power is reduced by controlling the length of each crystal in the sum frequency module.

7. The high-power nanosecond intracavity quintupling laser according to claim 1, characterized by comprising a quintupling crystal (33), the exit facet of said quintupling crystal (33) being cut with a spread angle for beam splitting.