CN207753292U - Two-frequency laser - Google Patents

Abstract

The utility model provides a dual-frequency laser, which includes a pump source, a focusing coupling system, a resonant cavity, a working medium, a frequency doubling device, a first light splitting device and an optical parametric oscillator. The pump source is used to generate pump light. The pump light generated by the pump source is input into the focusing coupling system for collimation and focusing, and then input into the resonant cavity. The working medium is set in the resonant cavity. The laser pumping working medium input into the resonator is output after being oscillated and amplified by the resonator. The laser input frequency doubling device output by the resonator. The first spectroscopic device is used to reflect a part of the laser light emitted by the frequency doubling device, and the other part passes through the first spectroscopic device to emit. The focusing coupling system, the resonant cavity, the working medium, the frequency doubling device and the first light splitting device are arranged on the same optical axis in sequence. The reflected light of the first light splitting device is input into the optical parametric oscillator, and after optical parametric oscillation, a high-power, high-energy tunable dual-frequency laser is output. The utility model has a simple structure, is convenient for mass production, and has wide application prospects.

Description

dual frequency laser

technical field

The utility model relates to the field of lasers, in particular to a dual-frequency laser.

Background technique

Dual-frequency lasers have a wide range of applications in fields such as optical interferometry and terahertz. Dual-frequency lasers with high power and high energy characteristics can further broaden the application range of dual-frequency lasers to a certain extent. Therefore, dual-frequency lasers with high-power and high-energy characteristics have attracted great attention and interest from researchers at home and abroad. However, it is currently difficult to prepare high-power, high-energy dual-frequency lasers.

Utility model content

Based on this, it is necessary to provide a dual-frequency laser to solve the problem that it is difficult to prepare a high-power, high-energy dual-frequency laser.

A dual-frequency laser comprising:

a pumping source for emitting pumping light;

a focusing coupling system, the pump light generated by the pump source is input into the focusing coupling system;

a resonant cavity, the laser output by the focusing coupling system is input into the resonant cavity;

The working medium is arranged in the resonant cavity, the laser input into the resonant cavity pumps the working medium, and the generated laser is oscillated and amplified by the resonant cavity and then output;

A frequency doubling device, the laser output from the resonator is input to the frequency doubling device;

The first spectroscopic device is used to reflect a part of the laser light emitted by the frequency doubling device, and the other part passes through the first spectroscopic device to emit, the focusing coupling system, the resonant cavity, the working medium, The frequency doubling device and the first spectroscopic device are arranged in sequence along the same optical axis;

An optical parametric oscillator, the reflected light of the first spectroscopic device is input to the optical parametric oscillator, and output tunable dual-frequency laser light after optical parametric oscillation.

In one of the embodiments, the pump source is a semiconductor laser.

In one of the embodiments, the dual-frequency laser also includes:

An optical fiber, connected between the pump source and the focusing coupling system, is used to input pump light from the pump source into the focusing coupling system.

In one of the embodiments, the focus coupling system includes at least one lens, and the at least one lens is perpendicular to the laser light input into the focus coupling system, and is used for focusing the laser light input into the focus coupling system.

In one of the embodiments, the working medium is a composite crystal of a gain medium and a saturable absorber.

In one of the embodiments, the side of the working medium facing the focusing coupling system is coated with an anti-reflection film and a reflective film as the front cavity mirror of the resonator, and the working medium is far away from a side of the focusing coupling system. The side is coated with a high reflection film and a partial reflection film as the rear cavity mirror of the resonant cavity.

In one of the embodiments, the frequency doubling device is an anti-smudge potassium titanyl phosphate crystal.

In one of the embodiments, the first spectroscopic device is used to reflect and output the frequency-doubled laser emitted by the frequency doubling device, and to transmit the unconverted laser light emitted by the frequency doubling device. output through the first light splitting device.

In one of the embodiments, the optical parametric oscillator is a periodically poled anti-gray trace potassium titanyl phosphate crystal.

In any one of the above embodiments, the dual-frequency laser further includes:

The second spectroscopic device is configured to reflect and output a part of the laser light emitted by the optical parametric oscillator, and emit the other part through the second spectroscopic device.

In the dual-frequency laser provided by the utility model, the pumping light generated by the pumping source pumps the working substance after passing through the focusing coupling system, and then enters the multiplied Laser frequency doubling by frequency device can obtain laser with high output power and high light-to-light conversion efficiency. Part of the laser light emitted by the frequency doubling device is emitted through the first spectroscopic device, and the other part is reflected by the first spectroscopic device to the optical parametric oscillator for optical parametric oscillation, thereby generating a tunable output of the dual-frequency laser, A high-power, high-energy dual-frequency tunable laser is formed. The dual-frequency laser device of the utility model is simple in structure and easy to operate, and has wide application prospects in fields such as optical interferometry and terahertz oscillation sources.

Description of drawings

Fig. 1 is a schematic structural diagram of a dual-frequency laser provided by an embodiment of the present invention;

Fig. 2 is the change curve of the average output power of the laser emitted by the frequency doubling device provided by an embodiment of the present invention with the absorbed pump power;

Fig. 3 is the spectral characteristic of the laser emitted by the frequency doubling device provided by an embodiment of the present invention;

FIG. 4 shows the spot characteristics of the laser light emitted by the frequency doubling device provided by an embodiment of the present invention.

Explanation of reference numbers:

10 dual frequency lasers

100 pump source

110 fiber

200 focus coupling system

210 lens

300 cavity resonators

310 front endoscope

320 rear cavity mirror

400 working substances

410 gain medium

420 saturable absorber

500 multiplier

600 The first spectroscopic device

700 Optical Parametric Oscillators

800 second splitting device

Detailed ways

In order to make the above purpose, features and advantages of the present utility model more obvious and understandable, the specific implementation of the present utility model will be described in detail below in conjunction with the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a full understanding of the present invention. However, the utility model can be implemented in many other ways different from those described here, and those skilled in the art can make similar improvements without violating the connotation of the utility model, so the utility model is not limited by the specific implementation disclosed below .

Please refer to Fig. 1, the utility model provides a dual-frequency laser 10, including a pump source 100, a focusing coupling system 200, a resonator 300, a working medium 400, a frequency doubling device 500, a first beam splitting device 600 and an optical parametric oscillator 700 . The pump source 100 is used to emit pump light. The pump light generated by the pump source 100 is input into the focusing coupling system 200 . The laser output from the focusing coupling system 200 is input into the resonant cavity 300 . The working medium 400 is disposed in the resonant cavity 300 . The laser light input into the resonant cavity 300 pumps the working medium 400 and then is oscillated and amplified by the resonant cavity 300 before being output. The laser output from the resonant cavity 300 is input into the frequency doubling device 500 . The first spectroscopic device 600 is used to reflect a part of the laser light emitted by the frequency doubling device 500 , and the other part passes through the first spectroscopic device 600 to emit. The focusing coupling system 200 , the resonant cavity 300 , the working medium 400 , the frequency doubling device 500 and the first spectroscopic device 600 are sequentially arranged along the same optical axis. The reflected light of the first spectroscopic device 600 is input into the optical parametric oscillator 700, and output tunable dual-frequency laser light after optical parametric oscillation.

The pump source 100 can generate pump light. The pumping source 100 can be a traditional solid-state laser, or a high-power diode laser module or laser array. The output wavelength of the pump source 100 can be adjusted according to requirements. The pumping light is input into the focusing coupling system 200 for collimation and focusing, and a pumping spot suitable for the resonant cavity 300 is formed after focusing. The focused laser light is injected into the resonant cavity 300 . The working substance 400 is arranged in the resonant cavity 300 . The laser performs end-pumping on the working substance 400, and the generated laser oscillates through the resonant cavity 300 to output fundamental frequency light λ ₀ . The fundamental frequency light λ ₀ is injected into the frequency doubling device 500 for laser frequency doubling to generate frequency doubled light λ ₀ /2 whose frequency is doubled. Ideal frequency doubling efficiency can be obtained by adjusting the parameters of the frequency doubling device 500 .

The frequency-doubled light λ ₀ /2 and the non-frequency-doubled fundamental frequency light λ ₀ are mixed together and emitted to the first spectroscopic device 600 . The first spectroscopic device 600 reflects the frequency-doubled light λ ₀ /2 to the optical parametric oscillator 700 , and transmits and outputs the base-frequency light λ ₀ that has not been frequency-multiplied. The frequency-doubled light λ ₀ /2 entering the optical parametric oscillator 700 performs optical parametric oscillation to output two outgoing lasers with different frequencies, wherein the outgoing laser with a higher frequency is signal light λ ₂ , and the outgoing laser with a lower frequency is idler light λ ₁ . The tunable outputs of _λ1 and _λ2 can be realized by adjusting the parameters of the optical parametric oscillator 700.

In this embodiment, the pumping light generated by the pumping source 100 pumps the working substance 400 after passing through the focusing coupling system 200, and then oscillating and amplifying through the resonant cavity 300 and then input into the frequency multiplied The device 500 performs laser frequency doubling to obtain laser light with high output power and high light-to-light conversion efficiency. Among the laser beams emitted by the frequency doubling device 500 , the unmultiplied fundamental frequency light λ ₀ passes through the first spectroscopic device 600 and is emitted. The frequency-doubled light λ ₀ /2 generated after frequency doubling is reflected by the first spectroscopic device 600 to the optical parametric oscillator 700 for optical parametric oscillation, thereby generating signal light λ ₂ with a higher frequency and idler light with a lower frequency. The tunable output of frequency light λ ₁ constitutes a high-power, high-energy dual-frequency tunable laser. At the same time, the signal light λ ₂ and the fundamental frequency light λ ₀ can also constitute a tunable dual-frequency laser. The utility model has the advantages of simple structure and easy operation, and has wide application prospects in the fields of light interference measurement, terahertz oscillation source and the like.

In one embodiment, the pump source 100 may be a semiconductor laser. Specifically, the pumping source 100 is an 808nm quasi-continuous semiconductor laser, which can generate pumping light with a wavelength of 808nm. In this embodiment, the pumping source 100 adopts an 808nm quasi-continuous semiconductor laser, which has high output light power, compact structure, stable structure and long service life.

In one embodiment, the dual-frequency laser 10 further includes an optical fiber 110 . The optical fiber 110 is connected between the pumping source 100 and the focusing coupling system 200 , and is used for inputting pump light from the pumping source 100 into the focusing coupling system 200 . In one embodiment, the core diameter of the optical fiber 110 is 400 μm, and the numerical aperture NA is 0.22. The pump light is coupled out to the focusing coupling system 200 through the optical fiber 110 . In another embodiment, the pump light can directly enter the focusing coupling system 200 .

In this embodiment, the optical fiber 110 is used for coupling output, which can compress the divergence angle. The pump light is totally reflected in the optical fiber 110, and the transmission efficiency is high.

In one embodiment, the focusing coupling system 200 includes at least one lens 210 . The at least one lens 210 is perpendicular to the laser light input into the focusing coupling system 200 . The shape of the lens 210 can be selected as required. For example, the lens 210 may be cylindrical or spherical. In one embodiment, the focus coupling system 200 is two convex lenses arranged in parallel and spaced apart, both of which have a focal length of 8 mm. The diameter of the pump spot can be adjusted between 180 μm and 220 μm. In one embodiment, the focused spot diameter is 200 μm. The type and number of the lens 210 used in the focusing coupling system 200 are not limited, as long as the function of collimation and focusing can be realized, and the size of the pump light spot after shaping is close to the size of the fundamental mode oscillation spot of the resonator 300, that is, the mode Just match. For example, the focusing coupling system 200 may also use a self-focusing lens. In order to enhance coupling efficiency, the surface of the lens 210 may also be coated with an anti-reflection coating for pump light.

In this embodiment, the focusing coupling system 200 adopts at least one lens 210 for collimating and focusing, and can form a light spot that is mode-matched with the resonant cavity 300 . The structure is flexible.

In one embodiment, the working medium 400 may be a composite crystal of the gain medium 410 and the saturable absorber 420 . The gain medium 410 and the saturable absorber 420 are composited into the working medium 400 through bonding technology. The working medium 400 has a microchip structure, that is, both the gain medium 410 and the saturable absorber 420 are crystal microchips. The microchip structure is conducive to miniaturization and integration. In one embodiment, the working medium 400 may be a Nd:YAG/Cr ⁴⁺ :YAG composite crystal. The gain medium 410 is Nd:YAG crystal.

In one embodiment, the length of the gain medium 410 can be adjusted between 1mm-2.0mm. In one embodiment, the length of the gain medium 410 can be set to any value among 1.2mm, 1.4mm, 1.6mm, and 1.8mm. In one embodiment, the doping concentration of Nd ³⁺ in the Nd:YAG crystal can be 1 at.%. The saturable absorber 420 is a passive Q-switch, which is used to compress the pulse width and increase the peak power. In one embodiment, the saturable absorber 420 is Cr ⁴⁺ :YAG crystal. In one embodiment, the initial transmittance of the saturable absorber 420 may be set at 50%-95%. In one embodiment, the initial transmittance of the saturable absorber 420 can be set to any value among 60%, 70%, 80%, and 90%. In another embodiment, the saturable absorber 420 may also use a LiF color center crystal.

In one embodiment, the pump light power is continuously increased from the pump threshold to 50W. In one embodiment, the repetition frequency of the pumping light is 10 Hz-5 kHz. In one embodiment, the repetition frequency of the pump light is 20 Hz-1 kHz. In another embodiment, the repetition frequency of the pumping light can be any one of 30 Hz, 40 Hz, 50 Hz, 100 Hz and 500 Hz. In one embodiment, the pump light pulse width is 100 μs-500 μs. In one embodiment, the pump light pulse width is 150 μs-450 μs. In one embodiment, the pump light pulse width can be adjusted to any value among 200 μs, 250 μs, 300 μs, 350 μs, and 400 μs.

In this embodiment, the gain medium 410 is end-pumped by the laser beam focused by the focusing coupling system 200 . Nd:YAG has a high absorption coefficient for 808nm pump light, which matches the 808nm quasi-continuous semiconductor laser, and can obtain high output power and pump efficiency, achieving spectral matching. Cr ⁴⁺ : YAG has a simple structure, is easy to use, has no electromagnetic interference, and can obtain giant pulses with high peak power and small pulse width. The working medium 400 adopting a microchip structure is beneficial to realize the miniaturization and integration of the terahertz wave oscillator 10 .

In one embodiment, the side of the working medium 400 facing the focusing coupling system 200 is coated with an anti-reflection film and a reflective film as the front cavity mirror 310 of the resonator 300 . The side of the working medium 400 away from the focusing coupling system 200 is coated with a high reflection film and a partial reflection film as the rear cavity mirror 320 of the resonator 300 . The front cavity mirror 310 and the rear cavity mirror 320 constitute the resonant cavity 300 . By adjusting the shape of the end surface of the working medium 400, a parallel plane resonant cavity or a flat concave cavity can be formed. In one embodiment, the resonant cavity 300 is a parallel plane resonant cavity. In one embodiment, the anti-reflection film is an 808nm anti-reflection film. The reflective film is a 1064nm reflective film. The high reflection film is an 808nm high reflection film, and the reflectivity R _oc =90%@1064nm. The partial reflection film is a 1064nm partial reflection film. In one embodiment, after the 808nm pumping light is injected into the resonant cavity 300, the pumping light performs end pumping on the working medium 400 to generate 1064nm laser light, which is Q-switched through the saturable absorber 420 A pulsed laser is then generated. The pulsed laser is oscillated and amplified by the resonant cavity 300 and then emitted from the partially reflective film.

In this embodiment, the resonant cavity 300 is constructed by coating the end faces of the compound crystal formed by the gain medium 410 and the saturable absorber 420 . The advantages of such a structure are: 1. Shorten the cavity length of the laser resonator, reduce the volume of the system, and facilitate the miniaturization of the solid-state laser; Intracavity loss; 3. Narrow the laser pulse width and increase the peak power. By adjusting the pump light power, pump spot size, pump light repetition frequency, pump light pulse width and the parameters of the working substance 400, high average output power and large energy single-frequency laser output can be realized.

In one embodiment, the frequency doubling device 500 may be an anti-smudge potassium titanyl phosphate crystal. The length of the anti-gray trace potassium titanyl phosphate (GTR-KTP) crystal can be adjusted as required. In one embodiment, the length of the GTR-KTP crystal is 3mm-7mm. In one embodiment, the length of the GTR-KTP crystal can be any one of 4mm, 5mm and 6mm. In another embodiment, the frequency doubling device 500 may also use other nonlinear optical media. Such as BBO crystal, lithium triborate (LiB ₃ O ₅ ).

In this embodiment, the frequency doubling device 500 doubles the frequency of the laser light emitted from the resonant cavity 300 before emitting it. The wavelength band of the laser is expanded, and the laser with a shorter wavelength can be obtained.

See Figure 2, Figure 3 and Figure 4. FIG. 2 is a curve showing the average output power of green laser output after frequency doubling as a function of absorbed pump power in an embodiment of the present invention. Among them, the slope efficiency η _s is 21%. It can be seen from the curve in Fig. 2 that when the absorbed pump power is 7W, the highest average output power of 1.2W can be obtained, and the light-to-light conversion efficiency is 17%. Preparations are made for the subsequent acquisition of the dual-frequency laser 10 with high conversion efficiency and high average output power. Figure 3 shows the spectral characteristics of the green laser after frequency doubling. It can be seen from Figure 3 that the central wavelength is 532nm. Figure 4 shows the spot characteristics of the green laser light obtained after frequency doubling. It can be seen from Figure 4 that the output laser is a fundamental mode spot close to the diffraction limit.

In one embodiment, the first spectroscopic device 600 is used to reflect the output of the laser light emitted by the frequency doubling device 500 after frequency doubling, and to output the laser light emitted by the frequency doubling device 500 without frequency doubling The converted laser light is output through the first spectroscopic device 600 . In one embodiment, the first beam splitting device 600 is a beam splitter. In one embodiment, the beam splitter is set at an angle of 45° to the laser emitted by the frequency doubling device 500 , so that the frequency doubled light is emitted from a direction perpendicular to the outgoing laser. The type of the beam splitter is not limited, as long as it can split the frequency doubled light and the fundamental frequency light in the laser light emitted by the frequency doubling device 500 into different directions for output. In this embodiment, the frequency doubled light and the fundamental frequency light in the laser light emitted by the frequency doubling device 500 can be separated by using the first spectroscopic device 600 . In one embodiment, the incident fundamental frequency light is a 1064nm laser, by adjusting parameters such as the length of the GTR-KTP crystal and the power of the incident fundamental frequency light, and splitting the beam through a beam splitter, a 532nm green laser can be realized Output, the fundamental frequency light is output from the other side of the beam splitter.

In one embodiment, the optical parametric oscillator 700 is a periodically poled anti-gray trace potassium titanyl phosphate crystal. The periodically polarized anti-grey trace potassium titanyl phosphate (GTR-KTP) crystal is artificially prepared in the nonlinear crystal GTR-KTP by periodically polarizing a grating, and periodically modulating the nonlinear coefficient of the crystal to achieve To compensate the phase mismatch caused by dispersion, a periodically poled GTR-KTP crystal was prepared. The length of the GTR-KTP crystal can be adjusted as needed. In one embodiment, the length of the GTR-KTP crystal is 3mm-7mm. In one embodiment, the length of the GTR-KTP crystal can be any one of 4mm, 5mm and 6mm. The optical parametric oscillator 700 is not limited to using the above-mentioned crystal, as long as it can realize the function of optical parametric oscillation. For example, in another embodiment, the optical parametric oscillator 700 may also use a periodically poled lithium niobate crystal (PPLN) or a periodically poled lithium tantalate crystal (PPLT).

In this embodiment, the optical parametric oscillator 700 uses a periodically poled anti-gray trace potassium titanyl phosphate crystal. The frequency-doubled light emitted by the frequency doubling device 500 is incident on the periodically polarized GTR-KTP crystal, and the optical parametric oscillation characteristic of the nonlinear crystal is used to finally realize dual-frequency laser (idle frequency light and signal light, respectively corresponding to λ ₁ and λ ₂ ) oscillate simultaneously. The tunable output of laser oscillation wavelength (λ ₁ and λ ₂ ) can be realized by adjusting the incident laser power, the length of GTR-KTP crystal, the external temperature, and the period of the polarization grating.

In one embodiment, the dual-frequency laser 10 further includes a second beam splitting device 800 . The second spectroscopic device 800 is used to reflect a part of the laser light emitted by the optical parametric oscillator 700 , and the other part passes through the second spectroscopic device 800 to emit. In one embodiment, the second beam splitting device 800 is a beam splitter. The reflected and output laser is signal light λ ₂ , and the transmitted and output laser is idler light λ ₁ . The beam splitter is arranged obliquely in the extending direction of the emitted laser light of the optical parametric oscillator 700 . In one embodiment, the beam splitter is set at an angle of 45° to the extension direction of the outgoing laser light of the optical parametric oscillator 700, so that the signal light λ in the outgoing laser light of the optical parametric oscillator 700 _is vertical It emits in the extending direction of the emitted laser light, and transmits the idler light _λ1 . In this embodiment, the second spectroscopic device 800 can output the idler light _λ1 and the signal light _λ2 in the emitted laser light of the optical parametric oscillator 700 to different directions respectively.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementations of the utility model, and the description thereof is relatively specific and detailed, but it should not be construed as limiting the patent scope of the utility model. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the scope of protection of the utility model patent should be based on the appended claims.

Claims (10)

1. A dual-frequency laser, characterized in that, comprising: pumping source (100), for emitting pumping light; a focusing coupling system (200), the pump light generated by the pump source (100) is input into the focusing coupling system (200); a resonant cavity (300), the laser output from the focusing coupling system (200) is input into the resonant cavity (300); The working medium (400) is arranged in the resonant cavity (300), the laser input into the resonant cavity (300) pumps the working medium (400), and the generated laser is oscillated and amplified by the resonant cavity (300) post output; A frequency doubling device (500), the laser output from the resonator (300) is input to the frequency doubling device (500); The first spectroscopic device (600) is used to reflect a part of the laser light emitted by the frequency doubling device (500), and the other part is emitted through the first spectroscopic device (600), and the focusing coupling system (200 ), the resonant cavity (300), the working medium (400), the frequency doubling device (500) and the first spectroscopic device (600) are arranged in sequence along the same optical axis; An optical parametric oscillator (700), the reflected light of the first light splitting device (600) is input into the optical parametric oscillator (700), and output tunable dual-frequency laser light after optical parametric oscillation. 2. The dual-frequency laser according to claim 1, characterized in that the pumping source (100) is a semiconductor laser. 3. The dual-frequency laser according to claim 1, further comprising: An optical fiber (110), connected between the pumping source (100) and the focusing coupling system (200), for inputting pump light from the pumping source (100) into the focusing coupling system (200) ). 4. dual-frequency laser according to claim 1, is characterized in that, described focusing coupling system (200) comprises at least one lens (210), and described at least one lens (210) and input described focusing coupling system (200) ) laser vertically, for focusing the laser input into the focusing coupling system (200). 5. The dual-frequency laser according to claim 1, characterized in that, the working medium (400) is a composite crystal of a gain medium (410) and a saturable absorber (420). 6. dual-frequency laser according to claim 1, is characterized in that, described working medium (400) is coated with anti-reflection film and reflection film as described cavity ( The front cavity mirror (310) of 300), the side of the working medium (400) away from the focusing coupling system (200) is coated with a high reflective film and a partial reflective film as the rear cavity mirror of the resonant cavity (300) (320). 7. The dual-frequency laser according to claim 1, characterized in that the frequency doubling device (500) is an anti-smudge potassium titanyl phosphate crystal. 8. The dual-frequency laser according to claim 1, characterized in that, the first spectroscopic device (600) is used to make the laser reflection output generated after frequency doubling emitted by the frequency doubling device (500), and The laser light emitted by the frequency doubling device (500) without frequency doubling conversion is output through the first light splitting device (600). 9. The dual-frequency laser according to claim 1, characterized in that the optical parametric oscillator (700) is a periodically poled anti-gray trace potassium titanyl phosphate crystal. 10. The dual-frequency laser according to any one of claims 1-9, further comprising: The second spectroscopic device (800) is configured to reflect and output a part of the laser light emitted by the optical parametric oscillator (700), and emit the other part through the second spectroscopic device (800).