CN118017329A - Dual-wavelength intracavity sum-frequency pulsed blue laser - Google Patents

Abstract

A dual-wavelength running intracavity sum frequency pulse blue laser belongs to the technical field of lasers, and utilizes a laser diode to pump two fundamental frequency pulse lasers of 908nm and 1047nm generated by an Nd: YLF crystal electro-optic Q-switched laser, and the two wavelengths are simultaneously started to vibrate in the cavity and then sum frequency to obtain 486nm solar dark line blue laser output. The invention has the characteristics of miniaturization, high peak power, good beam quality and the like, and is suitable for the fields of marine radar detection, underwater communication and the like.

Description

Dual-wavelength intracavity sum-frequency pulsed blue laser

Technical Field

The invention belongs to the technical field of lasers, and in particular relates to a dual-wavelength operating intracavity sum-frequency pulsed blue laser.

Background technique

In the field of solid lasers, green lasers represented by 532nm Nd:YAG lasers are relatively mature. In comparison, blue lasers are a relatively new visible laser light source. However, with its wide application in biomedicine, laser display, high-density optical storage, ocean detection and underwater communications, blue lasers have become a research hotspot in the field of laser technology research. The blue-green light band is the optical transmission window of ocean water bodies. Its attenuation coefficient in ocean water bodies is significantly lower than that of other bands. In deep sea water bodies, the short-wave blue light with a wavelength in the 450-490nm band has the highest transmittance, so it is selected as the working band for ocean lidar detection. There is a Fraunhofer dark line at 486.13nm in the solar absorption spectrum. Selecting this wavelength pulse laser as the detection light source can effectively reduce the background noise of sunlight, thereby improving the signal-to-noise ratio of the echo signal.

Patent CN 109586153 A introduces a method of building two separate fundamental frequency lights of 903nm and 1053nm and then performing frequency summing to obtain 486.1nm blue laser. The structure of this solution is relatively complex, and the stimulated emission cross section of the fundamental frequency wavelength is small, which is not easy to meet the requirements of compactness and high power applications.

Summary of the invention

In order to overcome the shortcomings of the current complex structure of laser technology in this band, the present invention provides a dual-wavelength intracavity sum-frequency pulsed blue light laser, which can achieve simultaneous oscillation of dual wavelengths in a single resonant cavity, and directly obtain 486.1nm pulsed blue light output after intracavity sum-frequency, and has a compact structure, which can meet the application requirements of miniaturization and high power.

The core innovation of the present invention is:

The two fundamental frequency pulse lasers of 908nm and 1047nm generated by laser diode pumping Nd:YLF crystal electro-optical Q-switched laser are simultaneously oscillated in the same resonant cavity and then frequency-summed to obtain 486nm solar dark line blue laser output.

The technical solution of the present invention is:

The present invention provides a dual-wavelength intracavity sum-frequency pulsed blue laser, comprising a pump module, a laser resonant cavity and a driving module, wherein the pump module comprises an LD pump source and a pump coupling lens group placed along the optical axis;

The laser resonant cavity at least comprises:

An input mirror is used to input the pump light emitted by the pump module and collimated and focused into the laser crystal, and to reflect the fundamental frequency light to form laser oscillation between the output mirrors;

An electro-optical Q-switched switch, comprising a Brewster polarizer, a quarter wave plate and a Q-switched crystal placed along an optical axis, wherein the angle between the Brewster polarizer and the optical axis is slightly larger or smaller than the Brewster angle, and both the incident surface and the exit surface are coated with 908nm and 1047nm anti-reflection films, so that both 908nm p-polarized light and 1047nm s-polarized light are transmitted through the Brewster polarizer, thereby generating 908nm and 1047nm laser pulses;

A sum frequency crystal, used to convert the 908nm and 1047nm laser pulses as fundamental frequency light into sum frequency light; and,

An output mirror, used to output the sum frequency light and reflect the fundamental frequency light to form 908nm laser pulse and 1047nm pulse laser oscillation between the input mirrors;

The driving module is used to drive the LD pump source and the Q-switched crystal.

Specifically, the present invention provides a dual-wavelength intracavity sum frequency pulsed blue laser, including an LD pump source, a pump coupling lens group, an input mirror, a laser crystal, a Brewster polarizer, a quarter wave plate, a Q-switched crystal, a sum frequency crystal and an output mirror. The 806nm pump light emitted by the LD pump source is collimated and focused by the pump coupling lens group, which is coated with an 806nm anti-reflection film; the focused pump light enters the laser crystal through the input mirror, the pump light incident surface of the input mirror is coated with an 806nm anti-reflection film, and the output surface is coated with an 806nm anti-reflection film and 908nm and 1047nm high-reflection films; the pump light focus is located inside the laser crystal, the laser crystal is an a-axis cut Nd:YLF crystal, the c-axis of which is perpendicular to the resonant cavity plane, and the two light-transmitting surfaces of the crystal are coated with 806nm, 908nm and 1047nm anti-reflection films, the ⁴ F _3/2 - ⁴ I _9/2 transition of the Nd:YLF crystal includes a 903nm laser with π polarization and a 908nm laser with σ polarization, ⁴ F _3/2 - ⁴ I The _11/2 transition includes a π-polarized 1047nm laser and a σ-polarized 1053nm laser. Due to the polarization selection of the Brewster polarizer and the coating selection of the input mirror and the output mirror, the σ-polarized 908nm laser perpendicular to the c-axis and the 1047nm laser with the largest stimulated emission cross section can be oscillated at the same time; the polarizer, 1/4 wave plate and Q-switched crystal form an electro-optical Q-switched switch to form 908nm and 1047nm infrared laser pulses, wherein the Brewster polarizer The angle between the Brewster polarizer and the optical axis is slightly larger or smaller than the Brewster angle by 3°-5°, so that both the p-polarized light of 908nm and the s-polarized light of 1047nm are transmitted through the Brewster polarizer, the 1/4 wave plate is coated with 908nm and 1047nm anti-reflection films, and the Q-switched crystal is an electro-optical Q-switched crystal, such as rubidium titanyl phosphate RTP crystal, potassium deuterium phosphate KD*P crystal, etc., and the two light-transmitting surfaces of the electro-optical Q-switched crystal are coated with 908nm and 1047nm anti-reflection films. The 908nm and 1047nm laser pulses enter the sum frequency crystal as fundamental frequency light, and a 486nm pulse sum frequency light is generated due to the nonlinear effect of the sum frequency crystal. The sum frequency crystal is a second-class phase-matched crystal, such as a lithium triborate LBO crystal, a barium metaborate BBO crystal, a potassium titanyl phosphate KTP crystal, etc. The two light-transmitting surfaces of the sum frequency crystal are coated with 908nm, 1047nm and 486nm anti-reflection films; the front and rear surfaces of the output mirror are coated with a 486nm anti-reflection film and a 908nm, 1047nm high-reflection film, the 486nm sum frequency light is output after passing through the output mirror, and the fundamental frequency light is reflected by the output mirror and returns along the original optical path, forming 908nm and 1047nm pulse laser oscillations between the input mirror and the output mirror. The driver includes an LD driver and a Q-switched driver, wherein the LD driver is used to drive the LD pump source and operates in a pulse mode, the Q-switched driver is used to drive the Q-switched crystal, and the external trigger end of the LD driver is connected to the trigger input end of the Q-switched driver.

Compared with the prior art, the present invention has the following advantages:

1. Use LD to pump the wavelength laser and frequency of two polarization states of Nd:YLF crystal. The wavelength of the sum frequency light just matches the Fraunhofer dark line. The structure is simple and compact.

2. The two fundamental frequency lights share the same resonant cavity, the optical paths overlap, the modes match, and the light spots at the sum frequency crystal completely overlap, effectively improving the sum frequency efficiency.

3. The electro-optical Q-switching method is adopted to obtain high peak power pulse laser, which can be used for underwater communication and marine radar detection and has strong practicality.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the optical path of the dual-wavelength intracavity sum-frequency pulsed blue laser of the present invention.

In the figure: A-pump module, B-laser resonant cavity, C-drive module; 1-LD pump source, 2-pump coupling lens group, 3-input mirror, 4-laser crystal, 5-Brewster polarizer, 6-1/4 wave plate, 7-Q-switched crystal, 8-sum frequency crystal, 9-output mirror, 10-LD driver, 11-Q-switched driver.

Detailed ways

The specific implementation modes of the present invention are further described below in conjunction with the accompanying drawings, but the protection scope of the present invention shall not be limited thereto.

As shown in FIG1 , the dual-wavelength intracavity sum-frequency pulsed blue laser involved in the present invention comprises three parts: a pump module A, a laser resonant cavity B, and a drive module C. The positional relationship of the above components is as follows:

Pump A includes LD pump source 1, pump coupling lens group 2; the laser resonant cavity B includes input mirror 3, laser crystal 4, Brewster polarizer 5, 1/4 wave plate 6, Q-switched crystal 7, sum frequency crystal 8, output mirror 9, and the parameters and position relationship of each component are as follows:

The LD pump source 1 is a 806nm fiber-coupled output laser diode;

The pump coupling lens group 2 is coated with an anti-reflection film for the pump light wavelength of 806nm;

The input mirror is coated with an 806nm anti-reflection film and a 908nm and 1047nm high-reflection film;

The laser crystal 4 is an a-axis cut Nd:YLF crystal with a cutting size of 3mm×3mm×7mm, a Nd ³⁺ doping concentration of 0.8at.%, a c-axis of which is perpendicular to the resonant cavity screen, and two 3mm×3mm light-transmitting surfaces of the crystal are coated with 806nm, 908nm and 1047nm anti-reflection films;

The Brewster angle polarizer 5 is coated with 908nm and 1047nm anti-reflection films, and the angle between the polarizer and the optical axis is slightly larger or smaller than the Brewster angle by 3°-5°;

The 1/4 wave plate 6 is coated with 908nm and 1047nm anti-reflection films;

The Q-switching crystal 7 is an electro-optical Q-switching crystal, such as rubidium titanyl phosphate RTP crystal, potassium dideuterium phosphate KD ^* P crystal, etc., and the light-transmitting surfaces of the Q-switching crystal are coated with 908nm and 1047nm anti-reflection films;

The sum frequency crystal 8 is a second type of phase-matched crystal, such as lithium triborate LBO crystal, barium metaborate BBO crystal, potassium titanyl phosphate KTP crystal, etc.

The output mirror 9 is coated with 908nm, 1047nm high reflection film and 486nm anti-reflection film;

The pump light emitted from the LD pump source 1 is collimated and focused by the pump coupling lens group 2, and then enters the laser crystal 4 through the input mirror 3. The focus of the pump light is located inside the first laser crystal 4. The laser crystal 4 generates 908nm laser and 1047nm infrared laser excitation under the excitation of the pump light. The 908nm laser is p-polarized light, and the 1047nm laser is s-polarized light. The 908nm and 1047nm lasers pass through the electro-optical Q-switched switch composed of the Brewster polarizer 5, the 1/4 wave plate 6 and the Q-switched crystal 7 in sequence to generate 908nm and 1047nm laser pulses; the 908nm laser pulse and the 1047nm laser pulse are combined as fundamental frequency light, and the fundamental frequency light enters the sum frequency crystal 8 to generate sum frequency light, which is transmitted and output through the output mirror 9. The 908nm pulse laser and the 1047nm pulse laser are reflected by the output mirror 9 and return along the original optical path to form laser oscillation between the input mirror 3 and the output mirror 9;

The driving module C includes an LD driver 10 and a Q-switched driver 11. The driving output end of the LD driver 10 is connected to the LD pump source 1 for driving the LD pump source 1 and operates in a pulse mode with a repetition frequency of 1kHz and a pulse width of 480μs. The driving output end of the Q-switched driver 11 is connected to the Q-switched crystal 7 for driving the Q-switched crystal 7. The external trigger end of the LD driver 10 is connected to the trigger input end of the Q-switched driver 11. The high-voltage signal output by the Q-switched driver is synchronized with the LD driver, and the Q-switched high-voltage signal is located at the falling edge of the LD pump pulse.

In summary, the present invention has the characteristics of compact structure, miniaturization, high peak power, good beam quality and an output wavelength located at the Fraunhofer dark line. It can obtain high peak power 486.1nm pulsed blue light laser output, which is suitable for applications in underwater communications and marine radar detection.

The above embodiments are only for illustrating the technical features of the present invention and should not be used to limit the protection scope of the present invention. Any modification or replacement that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (11)

1. The dual-wavelength operation intracavity sum frequency pulse blue laser comprises a pumping module, a laser resonant cavity and a driving module, and is characterized in that,

The pumping module is used for outputting collimated and focused pumping light;

the laser resonant cavity at least comprises:

The input mirror is used for inputting the pump light emitted by the pump module and collimated and focused into the laser crystal and reflecting fundamental frequency light so as to form laser oscillation between the output mirrors;

The laser crystal is an a-axis cut Nd: YLF crystal, the c-axis is perpendicular to the optical axis plane, and both light-passing surfaces are plated with 806nm, 908nm and 1047nm antireflection films for generating 908nm and 1047nm laser under the excitation of pump light generated by the pump module;

An electro-optic Q-switched switch, which consists of a Brewster polarizer, a 1/4 wave plate and a Q-switched crystal, wherein the Brewster polarizer is arranged along an optical axis, the included angle between the Brewster polarizer and the optical axis is slightly larger or smaller than the Brewster angle, and an incidence surface and an emergent surface are plated with 908nm and 1047nm antireflection films, so that 908nm p polarized light and 1047nm s polarized light are transmitted through the Brewster polarizer, and 908nm and 1047nm laser pulses are generated;

the sum frequency crystal is used for converting the 908nm and 1047nm laser pulses as fundamental frequency light into sum frequency light; and

An output mirror for outputting the sum frequency light and reflecting the fundamental frequency light to form 908nm laser pulses and 1047nm pulse laser oscillations between the input mirrors;

the driving module is used for driving the pumping module and the Q-switching crystal.

2. The dual wavelength operation intracavity sum frequency pulse blue laser according to claim 1, wherein the pumping module comprises an LD pumping source and a pumping coupling lens group, and 806nm pumping light emitted by the LD pumping source (1) enters the laser crystal (4) through the input mirror (3) after being collimated and focused by the pumping coupling lens group (2); the pump light focus is positioned inside the laser crystal (4), and the laser crystal (4) generates 908nm and 1047nm laser under the excitation of 806nm pump light.

3. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein said drive module comprises an LD driver (10) and a Q-switched driver (11); the driving output end of the LD driver (10) is connected with the LD pumping source (1) and is used for driving the LD pumping source (1) to work in a pulse mode; the driving output end of the Q-switching driver (11) is connected with the Q-switching crystal (7) and is used for driving the Q-switching crystal (7); the external trigger end of the LD driver (10) is connected with the trigger input end of the Q-switching driver (11).

4. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the LD pumping source (1) is an optical fiber coupling output laser diode with the output center wavelength of 806 nm.

5. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the pump coupling lens group (2) is plated with a 806nm antireflection film.

6. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the front surface of the input mirror (3) is plated with a 806nm antireflection film, and the rear surface is plated with a 806nm antireflection film, a 908nm high reflection film and a 1047nm high reflection film.

7. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the included angle between the Brewster polarizer and the optical axis is slightly larger or slightly smaller than the Brewster angle by 3 degrees to 5 degrees.

8. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the 1/4 wave plate (6) is plated with 908nm and 1047nm antireflection films.

9. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the Q-switching crystal (7) is an electro-optic Q-switching crystal, such as a titanium oxyrubidium RTP crystal, a potassium dideuterium phosphate KD, a P crystal and the like.

10. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the sum frequency crystal (8) is a second-class phase-matched crystal, such as a lithium triborate LBO crystal, a barium metaborate BBO crystal, a potassium titanyl phosphate KTP crystal and the like, and two light-passing surfaces of the sum frequency crystal are plated with 908nm, 1047nm and 486nm antireflection films.

11. The dual wavelength operation intracavity sum frequency pulse blue laser of claim 1 wherein: the front and back surfaces of the output mirror (9) are plated with 486nm antireflection films and 908nm and 1047nm high-reflection films.