阅读说明：本技术 用于微片激光器泵浦源输出波长控制的装置 (Device for controlling output wavelength of microchip laser pumping source ) 是由 李振华 王俊 来建成 王春勇 严伟 纪运景 赵艳 于 2019-09-03 设计创作，主要内容包括：本发明公开了一种用于微片激光器泵浦源输出波长控制的装置,装置包括散热系统、半导体制冷片、第一连接热沉、激光二极管、温度传感器、窄带滤光片、光电传感器、固定支架、激光腔、第二连接热沉、金属基板、信号调理电路、信号处理系统和闭环控制电路；利用温度传感器进行升温和降温的判定,利用设置窄带滤光片结合光电探测器和信号调理电路感知激光二极管波长的偏移量,反馈给闭环控制电路利用模糊PID方法对半导体制冷片进行制冷或加热的变频控制。本发明采用波长信号与温度信号双重反馈,能根据微片激光器的工作环境设定相应的半导体制冷片温度,以保证激光器工作状态达到最佳,改善了微片激光器温度适应性差的问题。(The invention discloses a device for controlling the output wavelength of a pumping source of a microchip laser, which comprises a heat dissipation system, a semiconductor refrigerating sheet, a first connecting heat sink, a laser diode, a temperature sensor, a narrow band filter, a photoelectric sensor, a fixed support, a laser cavity, a second connecting heat sink, a metal substrate, a signal conditioning circuit, a signal processing system and a closed-loop control circuit, wherein the first connecting heat sink is connected with the laser diode; the temperature sensor is used for judging temperature rise and temperature drop, the narrow-band filter is arranged, the photoelectric detector and the signal conditioning circuit are combined to sense the wavelength offset of the laser diode, the wavelength offset is fed back to the closed-loop control circuit, and the fuzzy PID method is used for performing variable frequency control on the refrigeration or heating of the semiconductor refrigeration chip. The invention adopts double feedback of wavelength signals and temperature signals, and can set the corresponding temperature of the semiconductor refrigerating plate according to the working environment of the microchip laser, thereby ensuring the working state of the laser to be optimal and improving the problem of poor temperature adaptability of the microchip laser.)

1. A device for controlling the output wavelength of a pumping source of a microchip laser is characterized by comprising a heat dissipation system (1), a semiconductor refrigerating plate (2), a first connecting heat sink (3), a laser diode (4), a temperature sensor (5), a narrow-band filter (6), a photoelectric sensor (7), a fixed support (8), a laser cavity (9), a second connecting heat sink (10), a metal substrate (11), a signal conditioning circuit (12), a signal processing system (13) and a closed-loop control circuit (14);

wherein the heat dissipation system (1) is positioned at the tail part of the laser, the hot end of the semiconductor refrigeration piece (2) is connected with the heat dissipation system (1), the cold end of the semiconductor refrigeration piece (2) is tightly attached to the rear surface of the first connection heat sink (3), the laser diode (4) is fixed on the front surface of the first connection heat sink (3), the temperature sensor (5) is fixed on the shell of the laser diode (4), the narrow-band optical filter (6) covers the receiving window of the photoelectric sensor (7), the photoelectric sensor (7) is installed on the fixed support (8), the laser cavity (9) is arranged in the second connection heat sink (10), the metal substrate (11) is connected with the first connection heat sink (3), the second connection heat sink (10), the fixed support (8) is connected, the signal conditioning circuit (12) is connected with the photoelectric sensor (7), the signal processing system (13) is connected with the temperature sensor (5), The signal conditioning circuit (12) is connected with the closed-loop control circuit (14), and the closed-loop control circuit (14) is connected with the semiconductor refrigerating chip (2);

wherein, a wavelength feedback device composed of a narrow-band filter (6) and a photoelectric sensor (7) is arranged close to and below the laser diode (4); the central axis of the laser cavity (9) is coincident with the emission optical axis of the laser diode (4); the signal conditioning circuit (12) filters and denoises the wavelength signal fed back by the photoelectric sensor (7) and then transmits the wavelength signal to the signal processing system (13), the signal processing system (13) judges the peak value of the wavelength signal, and the magnitude and the direction of the current in the closed-loop control circuit (14) are changed by combining the temperature signal fed back by the temperature sensor (5), so that the temperature rise or the temperature drop of the semiconductor refrigerating sheet (2) is controlled.

2. The device for controlling the output wavelength of the laser diode pump source in the microchip laser as claimed in claim 1, characterized in that the laser cavity (9) is composed of a laser crystal, a Q-switching crystal, an input mirror and a coupling output mirror; wherein, the input mirror is positioned at the foremost end of the laser cavity (9) and is a receiving window of the pump light; the laser crystal is fixed behind the input mirror, and the Q-switched crystal is tightly attached to the rear surface of the laser crystal; the coupling-out mirror is located at the rearmost end of the laser cavity (9) and is the emission window of the laser light.

3. The laser diode pump source output wavelength control in a microchip laser as defined in claim 2The laser crystal is Nd: YVO₄The output wavelength is 1064 nm; q-switched crystal is Cr⁴⁺:YAG。

4. The device for controlling the output wavelength of a laser diode pump source in a microchip laser as claimed in claim 2, characterized in that the bandwidth of the narrow-band filter (6) is less than or equal to the absorption bandwidth of the laser crystal.

5. The device for controlling the output wavelength of a laser diode pump source in a microchip laser as claimed in claim 1, characterized in that the output wavelength of the laser diode (4) is 808 nm.

6. The device for controlling the output wavelength of the laser diode pump source in the microchip laser as claimed in claim 1, characterized in that the absorption bandwidth of the narrow band filter (6) is 806 nm to 810 nm.

Technical Field

The invention relates to a temperature control technology, in particular to a device for controlling the output wavelength of a pumping source of a microchip laser.

Background

In 1989, Zayhowski first proposed the concept of a microchip laser, reporting and studying a Yb: YAG microchip laser that achieved laser wavelength outputs of 1.064 μm and 1.3 μm. The microchip laser has the advantages of small volume, stable performance, long service life and the like, and has important application value in the fields of laser radar, laser sensing, laser medical treatment, optical storage, nonlinear optics and the like.

Microchip lasers typically use a laser diode as the pump source. A laser diode is a small semiconductor laser, and temperature has a large influence on the performance of the semiconductor laser, particularly the output wavelength of the semiconductor laser. When the output wavelength of the laser diode drifts, the laser crystal has a narrow absorption bandwidth to the pump light, so that a good wavelength matching effect is difficult to achieve, and the output light quality of the microchip laser is reduced.

Therefore, laser diode temperature control appears to be critical. Patent CN204087018U discloses a temperature control system of semiconductor laser, which is a negative feedback control system composed of semiconductor refrigerating chip, feedback measuring element and PID controller. The system firstly sets the temperature value of the TEC according to experience, and then controls the temperature of the laser through a feedback circuit. When the environmental temperature is not changed greatly, the method provided by the patent can accurately control the temperature of the laser; when the change amplitude of the environmental temperature is large, the output wavelength of the semiconductor laser drifts due to the sensitivity of the semiconductor laser to the temperature change, and at the moment, the value of the TEC needs to be reset. This patent gives a detailed description of the hardware circuitry of the control system, and involves little in terms of software control. In the aspect of software control, the document 'design and algorithm simulation of a semiconductor laser temperature control system, instrument technology and sensors, 2013(5): 95-98' proposes a fuzzy PID-Smith method, namely Smith estimation control is introduced on the basis of a fuzzy PID controller. The Smith estimation control is used for overcoming the problem of time lag of a laser temperature control system, but the Smith estimation control needs an accurate system model, and if the system model is changed in the working process of a laser, the control effect is obviously weakened.

Disclosure of Invention

The invention aims to provide a device for controlling the output wavelength of a pumping source of a microchip laser, which solves the problem of poor temperature adaptability of the microchip laser.

The technical solution for realizing the purpose of the invention is as follows: a device for controlling the output wavelength of a pumping source of a microchip laser comprises a heat dissipation system, a semiconductor refrigerating chip, a first connecting heat sink, a laser diode, a temperature sensor, a narrow band filter, a photoelectric sensor, a fixed support, a laser cavity, a second connecting heat sink, a metal substrate, a signal conditioning circuit, a signal processing system and a closed-loop control circuit;

the heat dissipation system is positioned at the tail part of the laser, the hot end of the semiconductor refrigeration piece is connected with the heat dissipation system, the cold end of the semiconductor refrigeration piece is tightly attached to the rear surface of the first connecting heat sink, the laser diode is fixed on the front surface of the first connecting heat sink, the temperature sensor is fixed on the laser diode shell, the narrow-band optical filter covers the receiving window of the photoelectric sensor, the photoelectric sensor is installed on the fixed support, the laser cavity is placed in the second connecting heat sink, the metal substrate is connected with the first connecting heat sink, the second connecting heat sink and the fixed support, the signal conditioning circuit is connected with the photoelectric sensor, the signal processing system is connected with the temperature sensor, the signal conditioning circuit and the closed-loop control circuit, and the closed-loop control circuit is;

the wavelength feedback device composed of the narrow-band filter and the photoelectric sensor is arranged close to and below the laser diode; the central axis of the laser cavity is superposed with the emission optical axis of the laser diode; the signal conditioning circuit filters and denoises the wavelength signal fed back by the photoelectric sensor and then transmits the wavelength signal to the signal processing system, the signal processing system judges the peak value of the wavelength signal, and the magnitude and the direction of the current in the closed-loop control circuit are changed by combining the temperature signal fed back by the temperature sensor, so that the temperature rise or the temperature reduction of the semiconductor refrigerating sheet is controlled.

Compared with the prior art, the invention has the following remarkable advantages: (1) the dual feedback of the wavelength signal and the temperature signal is adopted, and the corresponding temperature of the semiconductor refrigerating sheet can be set according to the working environment of the microchip laser, so that the working state of the laser is ensured to be optimal, and the problem of poor temperature adaptability of the microchip laser is solved; (2) the output light quality of the microchip laser is indirectly judged through the signal intensity of the photoelectric sensor, and compared with a method of direct detection by using a spectrometer, the microchip laser has higher integration degree, simpler use and lower manufacturing cost of the whole system; (3) and carrying out frequency conversion control on the semiconductor refrigerating sheet by using an improved fuzzy PID method. On one hand, the temperature is accurately, quickly and stably controlled by adjusting three parameters of the PID controller in real time; on the other hand, a frequency conversion control technology is introduced, and the energy consumption of the system is reduced.

Drawings

FIG. 1 is a schematic structural diagram of a microchip laser temperature control device according to the present invention.

Fig. 2 is a flow chart of temperature control of the microchip laser of the present invention.

Fig. 3 is a schematic diagram of an improved fuzzy PID control.

Fig. 4 is a simulation diagram of the temperature control effect of the present invention.

Detailed Description

As shown in fig. 1, a device for controlling output wavelength of a pumping source of a microchip laser comprises a heat dissipation system 1, a semiconductor chilling plate 2, a first connecting heat sink 3, a laser diode 4, a temperature sensor 5, a narrowband filter 6, a photoelectric sensor 7, a fixed bracket 8, a laser cavity 9, a second connecting heat sink 10, a metal substrate 11, a signal conditioning circuit 12, a signal processing system 13 and a closed-loop control circuit 14;

the heat dissipation system 1 is positioned at the tail part of the laser, the hot end of the semiconductor refrigeration piece 2 is connected with the heat dissipation system 1, the cold end of the semiconductor refrigeration piece 2 is tightly attached to the rear surface of the first connecting heat sink 3, the laser diode 4 is fixed on the front surface of the first connecting heat sink 3, the temperature sensor 5 is fixed on the shell of the laser diode 4, the narrow-band optical filter 6 covers the receiving window of the photoelectric sensor 7, the photoelectric sensor 7 is installed on the fixed support 8, the laser cavity 9 is placed in the second connecting heat sink 10, the metal substrate 11 is connected with the first connecting heat sink 3, the second connecting heat sink 10 and the fixed support 8, the signal conditioning circuit 12 is connected with the photoelectric sensor 7, the signal processing system 13 is connected with the temperature sensor 5, the signal conditioning circuit 12 and the closed-loop control circuit 14, and the closed-loop control circuit 14 is connected;

wherein, a wavelength feedback device composed of a narrow-band filter 6 and a photoelectric sensor 7 is arranged close to the laser diode 4 and below the laser diode; the central axis of the laser cavity 9 coincides with the emission optical axis of the laser diode 4; the signal conditioning circuit 12 filters and denoises the wavelength signal fed back by the photoelectric sensor 7 and then transmits the wavelength signal to the signal processing system 13, the signal processing system 13 judges the peak value of the wavelength signal, and the magnitude and the direction of the current in the closed-loop control circuit 14 are changed by combining the temperature signal fed back by the temperature sensor 5, so that the temperature rise or the temperature fall of the semiconductor refrigerating sheet 2 is controlled.

The laser cavity 9 consists of a laser crystal, a Q-switching crystal, an input mirror and a coupling output mirror; wherein, the input mirror is located at the foremost end of the laser cavity 9 and is a receiving window of the pump light; the laser crystal is fixed behind the input mirror, and the Q-switched crystal is tightly attached to the rear surface of the laser crystal; the coupling-out mirror is located at the rearmost end of the laser cavity 9 and is the emission window of the laser light.

Wherein the laser crystal is Nd: YVO₄The output wavelength is 1064 nm; q-switched crystal is Cr⁴⁺:YAG。

The bandwidth of the narrow-band filter 6 is less than or equal to the absorption bandwidth of the laser crystal.

The output wavelength of the laser diode 4 is 808 nm; the absorption bandwidth of the narrow-band filter 6 is 806-810 nm.

The device for controlling the output wavelength of the microchip laser pumping source adopts dual feedback control of wavelength deviation and temperature; the photoelectric sensor is used for detecting the output wavelength of the laser diode, and when the peak intensity of the wavelength signal is lower than a threshold value, the temperature sensor is used for detecting the temperature of the laser diode and then judging the temperature reduction or the temperature rise so as to change the temperature of the cold end of the semiconductor refrigeration chip (TEC), so that the laser diode works in a normal temperature range; the TEC is usually driven by a Pulse Width Modulation (PWM) method, and the variable frequency control is realized by changing the voltage and frequency of the PWM modulation using a modified fuzzy PID method, which includes the following steps:

step 1, carrying out optimization function method on three initial parameters K of PID controller_p0、K_i0And K_d0Setting;

step 2, determining the universe of discourse and universe of fuzzy controller input quantity and output quantity, and calculating the expansion factor of input quantity and output quantity;

step 3, grading the variation range of the input error, adopting different adjustment coefficients in different error intervals, and adjusting the scaling factor in real time;

step 4, determining a membership function and a fuzzy rule table of the fuzzy controller;

step 5, carrying out fuzzy reasoning and defuzzification on the input quantity to obtain the output quantity delta K of the fuzzy controller_p、ΔK_iAnd Δ K_dAnd the finally obtained output of the fuzzy PID controller is as follows:

in the formula, K_p、K_iAnd K_dRespectively a proportional control parameter, an integral control parameter and a differential control parameter.

Aiming at the problem that the tube core temperature of the laser diode cannot be directly measured, the invention realizes the accurate, rapid and stable control of the laser diode temperature by indirectly monitoring the feedback wavelength signal, taking the temperature feedback signal as an auxiliary means, combining an improved fuzzy PID control method and carrying out variable frequency control on the semiconductor refrigerating sheet, ensures the best output performance of the microchip laser and simultaneously reduces the energy consumption of the whole temperature control system.

The present invention will be described in detail with reference to examples.