CN117559207B - A high-precision narrow-linewidth wavelength-tunable pulse laser output method - Google Patents

Abstract

The invention relates to a high-precision narrow linewidth wavelength adjustable pulse laser output method, wherein a laser comprises a semiconductor laser pumping source, a laser gain crystal and a Q-switching device; a first F-P etalon is arranged between the semiconductor laser pumping source and the laser gain crystal; a second F-P etalon is arranged between the laser gain crystal and the Q-switching device; the laser gain crystal can generate a multi-longitudinal-mode light beam; the thickness of the first F-P etalon and the thickness of the second F-P etalon are adjustable, and the thickness d of the first F-P etalon is adjusted by the method, so that the first F-P etalon has high reflection on laser to be output; the thickness d of the second F-P etalon is adjusted such that the second F-P etalon is partially transmissive to the laser light to be output. The invention is beneficial to the high-power output of laser, and the thickness of the F-P etalon is regulated by the active feedback control of the industrial personal computer through the real-time monitoring of the broadband laser and the grating spectrometer, so that the high-precision narrow-linewidth adjustable wavelength pulse laser output can be realized.

Description

A high-precision narrow-linewidth wavelength-tunable pulse laser output method

Technical Field

The invention relates to a high-precision narrow-linewidth wavelength-adjustable pulse laser output method, belonging to the technical field of lasers.

Background technique

Common solid-state lasers can only emit a single or a few fixed wavelengths, which makes it difficult to meet the diverse needs of different applications. With the continuous development of lasers and laser technology and the increasing requirements of laser application fields, narrow-linewidth wavelength-tunable lasers have a wide range of application prospects in the fields of industry, laser detection, laser communication, etc.

In the prior art, by inserting an F-P etalon into the resonant cavity and utilizing the principle of multi-beam interference, a narrow linewidth single longitudinal mode laser output can be achieved with high transmittance for a laser mode of a specific frequency and high reflection loss for other modes. The output longitudinal mode can be tuned by changing the insertion angle of the etalon, changing the frequency of the transmission center wavelength, or adjusting the operating temperature of the gain medium, changing the optical length of the resonant cavity, and using a scanning interferometer at the output end to detect the wavelength.

Inserting an F-P etalon into the cavity will complicate the laser structure and introduce insertion loss. As the tuning fineness of the F-P etalon increases, the insertion loss in the resonant cavity will also increase, and the output power will decrease, which is not conducive to high-power laser output. At the same time, the method of using a scanning interferometer at the output end to detect the wavelength and tune the output longitudinal mode has low accuracy.

Summary of the invention

In order to overcome the above problems, the present invention provides a high-precision narrow linewidth wavelength adjustable pulse laser output method, the laser resonant cavity structure used is simple, the input and output cavity mirrors are replaced by F-P standard tools with adjustable spacing, no redundant components are inserted into the resonant cavity, the insertion loss is reduced, and it is conducive to high-power laser output. In addition, the method can achieve high-precision narrow linewidth adjustable wavelength pulse laser output through real-time monitoring of broadband lasers and grating spectrometers, and active feedback control of industrial computers to adjust the thickness of F-P standard tools.

The technical solution of the present invention is as follows:

A high-precision narrow linewidth wavelength-adjustable pulse laser output method, the laser comprises a semiconductor laser pump source, a laser gain crystal and a Q-switching device; a first F-P etalon is arranged between the semiconductor laser pump source and the laser gain crystal; a second F-P etalon is arranged between the laser gain crystal and the Q-switching device; the laser gain crystal can generate a multi-longitudinal mode beam; the thickness of the first F-P etalon and the second F-P etalon are adjustable;

The first F-P etalon and the second F-P etalon include a movable reflector and a fixed reflector; the movable reflector and the fixed reflector are perpendicular to the optical axis of the laser and are placed parallel to each other and spaced apart;

The movable reflector is made of PZT, and further comprises a first PZT actuator connected to the movable reflector of the first F-P etalon, and a second PZT actuator connected to the movable reflector of the second F-P etalon;

It also includes a control unit, a first broadband laser, a second broadband laser, a first grating spectrometer, and a second grating spectrometer; the first broadband laser and the first grating spectrometer detect the central wavelength of the first F-P etalon in real time and transmit it to the control unit; the second broadband laser and the second grating spectrometer detect the central wavelength of the second F-P etalon in real time and transmit it to the control unit;

The control unit is an industrial computer; the first PZT actuator and the second PZT actuator are connected to the control unit;

Laser output includes the following steps:

The transmittance T of the first F-P etalon or the second F-P etalon is:

;

;

Wherein, R is the basic transmittance of the first FP etalon or the second FP etalon, n is the refractive index of the first FP etalon or the second FP etalon, θ is the refraction angle of the light beam after entering the first FP etalon or the second FP etalon, λ is the wavelength of the incident wave, and d is the thickness of the first FP etalon or the second FP etalon;

The frequency v corresponding to the transmission peak of the first FP etalon or the second FP etalon is obtained:

;

Where, j is an integer coefficient, c is the speed of light;

Confirm the wavelength λ ₁ of the laser to be output;

The thickness d of the first FP etalon is adjusted so that the first FP etalon has high reflection to the output laser, that is:

;

Wherein, k is a coefficient, and k is a natural number;

The thickness d of the second FP etalon is adjusted so that the second FP etalon partially transmits the laser light to be output.

Furthermore, the thickness d of the second FP etalon is adjusted to satisfy the optimal transmittance.

Furthermore, the method further comprises the following steps:

Obtaining the wavelength λ ₁ of the laser to be output;

The central wavelength of the first F-P etalon is detected in real time by the first broadband laser and the first grating spectrometer; the central wavelength of the second F-P etalon is detected in real time by the second broadband laser and the second grating spectrometer;

The thicknesses of the first F-P etalon and the second F-P etalon are adjusted by controlling the first PZT actuator and the second PZT actuator, thereby changing the transmittance of the first F-P etalon and the second F-P etalon to the laser light to be output, so that the first F-P etalon has high reflectivity to the laser light to be output and the second F-P etalon partially transmits the laser light to be output.

The present invention has the following beneficial effects: the laser resonant cavity has a simple structure, low intracavity loss, and is conducive to high-power laser output. In the prior art, the method of inserting an F-P standard tool into the cavity for wavelength tuning has a relatively complex structure and will introduce insertion loss into the cavity. As the tuning fineness of the standard tool increases, the insertion loss in the cavity will also increase, and the output power will decrease. The present invention does not insert redundant devices into the resonant cavity, but adopts the method of replacing the cavity mirror with an F-P standard tool, which has a lower intracavity loss and is more conducive to the output of high-power lasers.

The laser has high wavelength tuning accuracy and fast response speed. In the prior art, the method of tuning the wavelength by changing the angle of the F-P standard and detecting the mode change through a scanning interferometer cannot perform fine tuning, and can only perform coarse tuning within a certain range. In the present invention, a broadband laser and a spectrometer are used to detect the central wavelength of the F-P standard in real time, and the PZT actuator is actively feedback-controlled by an industrial computer to drive the movable reflector to move, thereby achieving high response speed and high-precision wavelength tuning.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the overall structure of the present invention.

The reference numerals in the figure are as follows:

1. Semiconductor laser pump source; 2. First F-P etalon; 3. Laser gain crystal; 4. Q-switching device; 5. Second F-P etalon; 6. First PZT actuator; 7. First broadband laser; 8. First grating spectrometer; 9. Control unit; 10. Second grating spectrometer; 11. Second broadband laser; 12. Second PZT actuator.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Referring to FIG1 , a method for outputting a high-precision narrow linewidth wavelength-adjustable pulsed laser is provided, wherein the laser comprises a semiconductor laser pump source 1, a laser gain crystal 3 and a Q-switching device 4; a first F-P etalon 2 is provided between the semiconductor laser pump source 1 and the laser gain crystal 3; a second F-P etalon 5 is provided between the laser gain crystal 3 and the Q-switching device 4; the laser gain crystal 3 is capable of generating a multi-longitudinal mode beam; the thickness of the first F-P etalon 2 and the second F-P etalon 5 are adjustable;

The first F-P etalon 2 and the second F-P etalon 5 include a movable reflector and a fixed reflector; the movable reflector and the fixed reflector are perpendicular to the optical axis of the laser and are placed parallel to each other and spaced apart;

The movable reflector is made of PZT, and further comprises a first PZT actuator 6 connected to the movable reflector of the first F-P etalon 2, and a second PZT actuator 12 connected to the movable reflector of the second F-P etalon 5;

It also includes a control unit 9, a first broadband laser 7, a second broadband laser 11, a first grating spectrometer 8 and a second grating spectrometer 10; the first broadband laser 7 and the first grating spectrometer 8 detect the central wavelength of the first F-P etalon 2 in real time, and transmit it to the control unit 9; the second broadband laser 11 and the second grating spectrometer 10 detect the central wavelength of the second F-P etalon 5 in real time, and transmit it to the control unit 9;

The control unit 9 is an industrial computer; the first PZT actuator 6 and the second PZT actuator 12 are connected to the control unit 9;

As shown in FIG1 , the light emitted by the semiconductor laser pump source 1 enters the laser resonant cavity (composed of the first F-P etalon 2 and the second F-P etalon 5) through the first F-P etalon 2, and excites the laser gain crystal 3; the light generated by the laser gain crystal 3 oscillates in the resonant cavity, is amplified, and is output through the second F-P etalon 5.

The light emitted by the first broadband laser 7 and the second broadband laser 11 enters the first grating spectrometer 8 and the second grating spectrometer 10 through the first F-P etalon 2 and the second F-P etalon 5 respectively.

Laser output includes the following steps:

The transmittance T of the first F-P etalon 2 or the second F-P etalon 5 is:

;

;

Wherein, R is the basic transmittance of the first FP etalon 2 or the second FP etalon 5, n is the refractive index of the first FP etalon 2 or the second FP etalon 5, θ is the refraction angle of the light beam after entering the first FP etalon 2 or the second FP etalon 5, λ is the wavelength of the incident wave, and d is the thickness of the first FP etalon 2 or the second FP etalon 5;

The frequency v corresponding to the transmission peak of the first FP etalon 2 or the second FP etalon 5 is obtained:

;

Where, j is an integer coefficient, c is the speed of light;

Confirm the wavelength λ ₁ of the laser to be output;

The thickness d of the first FP etalon 2 is adjusted so that the first FP etalon 2 has high reflection to the output laser, that is:

;

Wherein, k is a coefficient, and k is a natural number;

The thickness d of the second FP etalon 5 is adjusted to make the second FP etalon 5 partially transmit the laser light to be output; the partially transmittance of the laser light to be output means that the transmittance of the second FP etalon 5 to the output laser light is between a minimum value and a maximum value, and the specific value is set according to actual needs.

The gain of the laser to be output is greater than the loss in the resonant cavity, and oscillation is obtained. The loss of other wavelengths is greater than the gain, and they cannot oscillate. When the laser to be output reaches the threshold condition for the generation of the laser beam, the target laser beam output is obtained. The Q value of the resonant cavity is suddenly changed by the Q-switching device 4, so as to obtain a pulsed laser output of the target wavelength.

By changing the thickness of the first F-P etalon 2 and the second F-P etalon 5, the frequency of the oscillation mode in the cavity can be changed to achieve the purpose of adjustable output wavelength.

In one embodiment of the present invention, the thickness d of the second FP etalon 5 is adjusted to meet the optimum transmittance. The optimum transmittance is determined according to the gain and loss.

In one embodiment of the present invention, the following steps are also included:

Obtaining the wavelength λ ₁ of the laser to be output;

The central wavelength of the first F-P etalon 2 is detected in real time by the first broadband laser 7 and the first grating spectrometer 8; the central wavelength of the second F-P etalon 5 is detected in real time by the second broadband laser 11 and the second grating spectrometer 10;

The thickness of the first F-P etalon 2 and the second F-P etalon 5 are adjusted by controlling the first PZT actuator 6 and the second PZT actuator 12, thereby changing the transmittance of the first F-P etalon 2 and the second F-P etalon 5 to the laser to be output, so that the first F-P etalon 2 has high reflectivity to the laser to be output and the second F-P etalon 5 partially transmits the laser to be output.

This embodiment adjusts the laser output wavelength by real-time detection of the center wavelengths of the first F-P etalon 2 and the second F-P etalon 5, and adjusting them to the target requirements. As shown in FIG1 , when the movable reflectors of the first F-P etalon 2 and the second F-P etalon 5 are both arranged on the side away from the laser gain crystal 3, adjusting the thickness of the first F-P etalon 2 and the second F-P etalon 5 does not affect the structure in the resonant cavity. A portion of the first F-P etalon 2 and the second F-P etalon 5 is arranged outside the resonant cavity, so that the center wavelengths of the first F-P etalon 2 and the second F-P etalon 5 are detected without affecting the optical path inside the resonant cavity and without increasing more losses.

The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure made using the contents of the present invention's specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims (3)

1. A high-precision narrow linewidth wavelength adjustable pulse laser output method is characterized in that a laser comprises a semiconductor laser pumping source (1), a laser gain crystal (3) and a Q-switching device (4); a first F-P etalon (2) is arranged between the semiconductor laser pumping source (1) and the laser gain crystal (3); a second F-P etalon (5) is arranged between the laser gain crystal (3) and the Q-switching device (4); the laser gain crystal (3) is capable of generating a multi-longitudinal mode beam; the thickness of the first F-P etalon (2) and the second F-P etalon (5) is adjustable;

The first F-P etalon (2) and the second F-P etalon (5) comprise a movable mirror and a fixed mirror; the movable reflecting mirror and the fixed reflecting mirror are perpendicular to the optical axis of the laser and are arranged in parallel at intervals;

The movable reflector is made of PZT, and further comprises a first PZT actuator (6) connected with the movable reflector of the first F-P etalon (2), and a second PZT actuator (12) connected with the movable reflector of the second F-P etalon (5);

The system also comprises a control unit (9), a first broadband laser (7), a second broadband laser (11), a first grating spectrometer (8) and a second grating spectrometer (10); the first broadband laser (7) and the first grating spectrometer (8) detect the central wavelength of the first F-P etalon (2) in real time and transmit the central wavelength to the control unit (9); the second broadband laser (11) and the second grating spectrometer (10) detect the center wavelength of the second F-P etalon (5) in real time and transmit the center wavelength to the control unit (9);

The control unit (9) is an industrial personal computer; the first PZT actuator (6) and the second PZT actuator (12) are connected to the control unit (9);

the laser output comprises the following steps:

the transmissivity T of the first F-P etalon (2) or the second F-P etalon (5) is:

；

；

Wherein R is the fundamental transmittance of the first F-P etalon (2) or the second F-P etalon (5), n is the refractive index of the first F-P etalon (2) or the second F-P etalon (5), θ is the refraction angle of the light beam after entering the first F-P etalon (2) or the second F-P etalon (5), λ is the wavelength of the incident wave, and d is the thickness of the first F-P etalon (2) or the second F-P etalon (5);

Obtaining a frequency v corresponding to the transmission peak of the first F-P etalon (2) or the second F-P etalon (5):

；

Wherein j is an integer coefficient, and c is the speed of light;

confirming the wavelength lambda ₁ of the laser to be output;

Adjusting the thickness d of the first F-P etalon (2) such that the first F-P etalon (2) has a high reflection of the laser light to be output, i.e.:

；

wherein k is a coefficient, and k is a natural number;

The thickness d of the second F-P etalon (5) is adjusted such that the second F-P etalon (5) is partially transmissive to the laser light to be output.

2. A high precision narrow linewidth wavelength tunable pulsed laser output method according to claim 1, characterized by adjusting the thickness d of the second F-P etalon (5) to meet the optimal transmittance.

3. The method for outputting the high-precision narrow-linewidth wavelength tunable pulse laser according to claim 1, further comprising the steps of:

Obtaining wavelength lambda ₁ of laser to be output;

-detecting in real time the center wavelength of the first F-P etalon (2) by means of the first broadband laser (7) and the first grating spectrometer (8); -detecting in real time the center wavelength of the second F-P etalon (5) by means of the second broadband laser (11) and the second grating spectrometer (10);

The thicknesses of the first F-P etalon (2) and the second F-P etalon (5) are adjusted by controlling the first PZT actuator (6) and the second PZT actuator (12), so that the transmissivity of the first F-P etalon (2) and the second F-P etalon (5) to output laser light is changed, and the first F-P etalon (2) has high reflection to the output laser light and the second F-P etalon (5) transmits the output laser light partially.