Single longitudinal mode pulse laser feedback control circuit and control method

Abstract

The present application discloses a single longitudinal mode pulse laser feedback control circuit and control method, the circuit includes: an optical signal acquisition module, used to collect optical signals in the laser; a signal processing module, used to determine whether the i-th optical signal reaches the single longitudinal mode pulse laser output condition, if it reaches it, outputs the single longitudinal mode pulse laser, if not, adjusts the linear pulse voltage of the input laser, and obtains the i+1th optical signal in the laser; a linear pulse voltage control module, used to adjust the linear pulse voltage in the input laser; the optical signal acquisition module is connected to the signal processing module; the signal processing module is connected to the linear pulse voltage control module; the signal processing module and the linear pulse voltage control module are respectively connected to the laser. The circuit can make the output probability of the single longitudinal mode pulse laser reach 100%, and the control efficiency is relatively high. Another aspect of the present application also provides a single longitudinal mode pulse laser feedback control method.

Description

Technical Field

[0001] The present application relates to a single longitudinal mode pulse laser feedback control circuit and a control method, belonging to the field of laser control. Background Art

[0002] Single-frequency lasers, that is, single longitudinal mode lasers, are characterized by the output laser mode that satisfies both single transverse mode and single longitudinal mode. Only a single longitudinal mode oscillates inside its resonant cavity, and the output light intensity presents a Gaussian distribution. In addition to the good monochromaticity and directionality of the laser itself, single longitudinal mode lasers have the characteristics of long coherence length and narrow spectral line width that are difficult to achieve with ordinary lasers. Moreover, single longitudinal mode pulse lasers also have the characteristics of good monochromaticity and no modulation in the time domain, and are often used as seed sources for pulsed lasers.

[0003] However, existing single longitudinal mode lasers have complex structures, poor output stability, high costs, and it is difficult to achieve high-frequency single longitudinal mode laser pulse output.

[0004] The principle of controlling the mode selection of a single longitudinal mode laser by Q-switching is to scan the cavity length of the resonant cavity in each pump pulse cycle, and analyze the interference signal formed after the seed light passes through the driven cavity. When the interference peak is detected, it means that the seed light and the driven cavity frequency are consistent, and the Q-switching switch is turned on instantly. This method can basically achieve a 100% single longitudinal mode output probability and has strong anti-interference performance. Summary of the invention

[0005] According to one aspect of the present application, a single longitudinal mode pulse laser feedback control circuit is provided, which can make the output probability of the single longitudinal mode pulse laser reach 100% and has high control efficiency.

[0006] The single longitudinal mode pulse laser feedback control circuit is characterized by comprising:

[0007] An optical signal acquisition module, used for acquiring optical signals in the laser;

[0008] A signal processing module, used for judging whether the i-th optical signal meets the single longitudinal mode pulse laser output condition, and outputting the single longitudinal mode pulse laser if it meets the condition; if it does not meet the condition, adjusting the linear pulse voltage input to the laser, and obtaining the i+1-th optical signal in the laser;

[0009] The linear pulse voltage control module is used to adjust the linear pulse voltage input into the laser;

[0010] The optical signal acquisition module is connected to the signal processing module; the signal processing module is connected to the linear pulse voltage control module; the signal processing module and the linear pulse voltage control module are connected to the laser respectively.

[0011] Optionally, the single longitudinal mode pulse laser output condition is that the interference signal formed after the seed laser in the laser passes through the driven cavity is the highest point of the interference peak.

[0012] Optionally, the optical signal acquisition module includes: a Pin tube and an A / D sampling circuit, wherein the Pin tube is arranged in the optical path of the laser and connected to the input end of the A / D sampling circuit, and is used to receive the feedback optical analog signal VI;

[0013] The output end of the A / D sampling circuit is connected to the input end of the signal processing module, and is used to convert the feedback optical analog signal VI into a digital signal.

[0014] Optionally, the laser comprises an RTP crystal, and the RTP crystal is arranged in the optical path of the laser;

[0015] The linear pulse voltage control module is connected to the voltage input end of the RTP crystal, and the other end of the crystal RTP is grounded.

[0016] Optionally, the laser includes an acousto-optic modulator, which is electrically connected to the signal processing module and is used to control the output of the single longitudinal mode pulse laser.

[0017] Optionally, the linear pulse voltage control module includes: an optical coupler, a third resistor, a second transistor, a fourth resistor, a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is connected to the anode terminal of the optical coupler;

[0018] The second input terminal is connected in series with a parallel circuit consisting of the third resistor and the second transistor;

[0019] The output terminal is connected in series with the fourth resistor.

[0020] Optionally, the linear pulse voltage control module includes: a first resistor, a second resistor, a first transistor, a diode, a fifth resistor, and a capacitor.

[0021] The collector end of the optical coupler is connected to the input end of the first resistor, the input end of the second resistor and the first end of the first transistor;

[0022] The output end of the first resistor is connected to a +12V DC voltage;

[0023] The output end of the second resistor is connected to the cathode end of the optocoupler, the S pole of the first transistor, and the diode;

[0024] One end of the fifth resistor is connected to the D electrode of the first transistor, and the other end is connected to the HV DC high voltage;

[0025] The generating end of the optical coupler is grounded;

[0026] The S terminal of the first transistor is connected to one end of the diode;

[0027] The other end of the diode is connected to one end of the capacitor;

[0028] The other end of the capacitor is grounded and connected to one end of the third resistor and the S electrode of the second transistor;

[0029] The D electrode of the second transistor is connected to one end of the fourth resistor.

[0030] Optionally, the first transistor and the second transistor are metal-oxide semiconductor field effect transistors.

[0031] Optionally, the optical signal acquired by the optical signal acquisition module is an optical signal of laser transmitted in the resonant cavity of the laser.

[0032] According to another aspect of the present application, a single longitudinal mode pulse laser feedback control method is provided, comprising the following steps:

[0033] a) Real-time collection of optical signals in the laser;

[0034] b) determining whether the optical signal meets the output condition of the single longitudinal mode pulse laser;

[0035] c) If the condition is met, outputting single longitudinal mode pulse laser; if not, adjusting the voltage input to the laser and then returning to step a) until the output condition is met.

[0036] The beneficial effects of this application include:

[0037] 1) The single longitudinal mode pulse laser feedback control circuit provided in the present application can output single longitudinal mode laser by turning on the acousto-optic modulation switch when the best matching point is obtained when scanning the resonant cavity of the pulse laser. The control process is simple and accurate, which improves the accuracy of laser mode selection and output stability.

[0038] 2) The single longitudinal mode pulse laser feedback control circuit provided in this application has a simple circuit structure, requires fewer components and has low cost; it is particularly suitable for single longitudinal mode pulse laser output control with a frequency of up to 20KHz, and can achieve a single longitudinal mode pulse laser with a stable output probability of 100%.

[0039] 3) The single longitudinal mode pulse laser feedback control circuit provided in this application has the advantages of high output frequency and 100% output of single longitudinal mode pulse laser. The circuit outputs high laser frequency and is a repetitive frequency laser, and the output voltage can reach 4000-5000V. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The drawings described herein are used to provide further understanding of the present invention and constitute a part of this application. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0041] Figure 1 This is a schematic diagram of the structure of a single longitudinal mode pulse laser feedback control circuit in one embodiment of the present application;

[0042] Figure 2 This is a schematic diagram of the structure of a single longitudinal mode pulse laser feedback control circuit in another embodiment of the present application;

[0043] Figure 3 This is a schematic diagram of the structure of a single longitudinal mode pulse laser feedback control circuit in another embodiment of the present application;

[0044] Figure 4 This is a schematic flow chart of a single longitudinal mode pulse laser feedback control method in yet another embodiment of the present application.

[0045] List of parts and reference numerals:

[0046] Part Name Reference numerals Part Name Reference numerals Optocoupler U3 The first transistor Q1 First resistor R1 diode D1 Second resistor R1 capacitance C1 The third resistor R3 The second transistor Q2 The fourth resistor R4 Fifth resistor R5 DETAILED DESCRIPTION

[0047] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0048] See also Figure 1 , the single longitudinal mode pulse laser feedback control circuit provided in the present application comprises:

[0049] An optical signal acquisition module, used for acquiring optical signals in the laser;

[0050] A signal processing module, used for judging whether the i-th optical signal meets the single longitudinal mode pulse laser output condition, and outputting the single longitudinal mode pulse laser if it meets the condition; if it does not meet the condition, adjusting the linear pulse voltage input to the laser, and obtaining the i+1-th optical signal in the laser;

[0051] The linear pulse voltage control module is used to adjust the linear pulse voltage input into the laser;

[0052] The optical signal acquisition module is connected to the signal processing module; the signal processing module is connected to the linear pulse voltage control module; the signal processing module and the linear pulse voltage control module are connected to the laser respectively.

[0053] The connection in this article includes optical connection and electrical connection. Electrical connection includes but is not limited to wired or wireless connection. The data transmitted after connection includes but is not limited to control instructions, voltage, and optical signals. Optical connection includes the connection of the optical path of each device.

[0054] The present application provides a circuit that measures the optical signal in the laser resonant cavity and adjusts the input voltage in the laser according to the measurement result. When an optical signal that meets the requirements is detected, the laser is controlled to output the laser that meets the conditions, thereby achieving a 100% output probability of a single longitudinal mode pulse laser.

[0055] Preferably, the single longitudinal mode pulse laser output condition is that the interference signal formed after the seed laser in the laser passes through the driven cavity is the highest point of the interference peak.

[0056] Optionally, the optical signal acquired by the optical signal acquisition module is an optical signal of laser transmitted in the resonant cavity of the laser.

[0057] See also Figure 2 Optionally, the optical signal acquisition module includes a Pin tube and an A / D sampling circuit, the Pin tube is arranged in the optical path of the laser and connected to the input end of the A / D sampling circuit, for receiving the feedback optical analog signal VI; the output end of the A / D sampling circuit is connected to the input end of the signal processing module, for converting the feedback optical analog signal VI into a digital signal.

[0058] Optionally, the laser includes an RTP crystal, the RTP crystal is arranged in the optical path of the laser, the linear pulse voltage control module is connected to the voltage input end of the RTP crystal, and the other end of the crystal RTP is grounded.

[0059] The linear pulse voltage control module controls the laser to generate a laser interference signal by adjusting the pressure on the RTP crystal, thereby controllably achieving single longitudinal mode pulse laser output.

[0060] RTP crystal, Chinese name: Rubidium Titanyl Phosphate. Mainly used in nonlinear and electro-optical fields.

[0061] See also Figure 2 Optionally, the linear pulse voltage control module includes: a first input end and a second input end, the first input end is connected to the anode end of the optocoupler U3, the collector end of the optocoupler U3 is connected to the input end of the first resistor R1, the input end of the second resistor R2 and the first end of the first transistor Q1;

[0062] The input end of the first resistor R1 is connected to a +12V DC voltage;

[0063] The output end of the second resistor R2 is connected to the cathode end of the optical coupler U3, the S pole of the first transistor Q1, and the diode D1;

[0064] One end of the fifth resistor R5 is connected to the D electrode of the first transistor Q1, and the other end is connected to the HV DC high voltage;

[0065] The generating end of the optocoupler U3 is grounded.

[0066] The S pole of the first transistor Q1 is connected to one end of the diode D1;

[0067] The other end of the diode D1 is connected to one end of the capacitor C1;

[0068] The other end of the capacitor C1 is grounded, and connected to one end of the third resistor R3 and the S electrode of the second transistor Q2;

[0069] The second input terminal is respectively connected to the first terminal of the second transistor Q2 and the other terminal of the third resistor R3;

[0070] The D terminal of the second transistor Q2 is connected to one end of the fourth resistor R4, and the other end of the fourth resistor R4 is used as an output end and connected to the voltage input end of the laser.

[0071] The linear pulse voltage control module can generate a pulsed linear high-voltage signal, thereby pressurizing the crystal RTP in the laser optical path as needed, and adjusting the cavity length continuously, rapidly and at a high repetition rate, thereby ensuring the output of single longitudinal mode pulsed laser.

[0072] By adopting this circuit, the high voltage input at one end can be adjusted and output as needed. The HV DC high voltage used here can be connected as needed.

[0073] Optionally, the transistor is a MOSFET transistor. MOSFET is a metal-oxide semiconductor field effect transistor, or MOSFET for short.

[0074] See also Figure 3 , optionally, in Figure 2 On the basis of the circuit structure shown, the laser includes an acousto-optic modulator, which is electrically connected to the signal processing module and is used to control the output of the single longitudinal mode pulse laser.

[0075] See also Figure 4 Another aspect of the present application further provides a single longitudinal mode pulse laser feedback control method, comprising the following steps:

[0076] a) Real-time collection of optical signals in the laser;

[0077] b) determining whether the optical signal meets the output condition of the single longitudinal mode pulse laser;

[0078] c) If the condition is met, outputting single longitudinal mode pulse laser; if not, adjusting the voltage input to the laser and then returning to step a) until the output condition is met.

[0079] The control method can improve the control efficiency and achieve a 100% probability of single longitudinal mode pulse laser output.

[0080] Example

[0081] In this embodiment, the single longitudinal mode pulse laser feedback control circuit is as follows: Figures 2-3 As shown, including:

[0082] S1: consists of optical input VI and A / D sampling U1 to collect optical pulse signals and perform digital processing;

[0083] S2: FPGA digital signal processor U2, which outputs out1 and out2 of the received optical signal to control the linear high-voltage pulse generating circuit in S3, and outputs out3 to control the acousto-optic modulator to achieve the purpose of controlling the laser output mode;

[0084] S3: The linear high-voltage pulse generating circuit includes an optocoupler U3, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a MOSFET transistor metal-oxide semiconductor field effect transistor, referred to as metal-oxide semiconductor field effect transistor Q1, a MOSFET transistor Q2, a capacitor C1, a diode D1, a +12V DC voltage and a HV DC high voltage.

[0085] The specific implementation process is as follows:

[0086] S1 converts the feedback optical analog signal VI received by the Pin tube in the optical path into a digital signal through the A / D sampling circuit and inputs it into S2;

[0087] The FPGA digital signal processor in S2 controls the linear high-voltage pulse generation circuit in S3 through the output signals out1 and out2 to generate a pulsed linear high-voltage signal to pressurize the crystal RTP in the optical path, and adjust the cavity length continuously and rapidly with high repetition rate. Then the FPGA digital signal processor in S2 monitors the optical input VI in S1 in real time. When VI reaches the highest point of the interference peak, the FPGA output signal out3 in S2 turns on the acousto-optic modulator and outputs a high-repetition-rate single longitudinal mode pulse laser.

[0088] The invention is characterized by a linear high-voltage feedback control circuit, low cost, a repetition frequency up to 20KHz, and can realize stable output of a single longitudinal mode of the laser.

[0089] The Pin tube is used to receive the optical input VI signal, and the FPGA digital signal processor analyzes the optical input VI signal to obtain the interference signal formed by the light. When an interference peak appears in the interference signal detected, it indicates that the laser in the laser cavity has reached the best matching point. At this time, the FPGA digital signal processor outputs an "open" instruction to the acousto-optic modulation switch. By controlling the acousto-optic modulation switch to turn on, a high-repetition-rate stable single longitudinal mode laser can be output.

[0090] The working medium of the laser resonant cavity is RTP crystal, through which the voltage can be controlled quickly and at a high repetition rate, so as to achieve continuous, fast and high repetition rate adjustment of the cavity length.

[0091] Through the circuit in this embodiment, single longitudinal mode pulse laser output with a repetition rate of up to 20KHZ can be achieved, and the output probability can reach 100%.

[0092] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A single longitudinal mode pulse laser feedback control circuit, characterized in that: include: An optical signal acquisition module, used for acquiring optical signals in the laser; A signal processing module, used for judging whether the i-th optical signal meets the single longitudinal mode pulse laser output condition, and outputting the single longitudinal mode pulse laser if it meets the condition; if it does not meet the condition, adjusting the linear pulse voltage input to the laser, and obtaining the i+1-th optical signal in the laser; The linear pulse voltage control module is used to adjust the linear pulse voltage input into the laser; The linear pulse voltage control module comprises: an optical coupler, a third resistor, a second transistor, a fourth resistor, a first input terminal, a second input terminal and an output terminal, wherein the first input terminal is connected to the anode terminal of the optical coupler; The second input terminal is connected in series with a parallel circuit consisting of the third resistor and the second transistor; The output end is connected in series with the fourth resistor; The optical signal acquisition module is connected to the signal processing module; the signal processing module is connected to the linear pulse voltage control module; the signal processing module and the linear pulse voltage control module are connected to the laser respectively; The single longitudinal mode pulse laser output condition is that the interference signal formed after the seed laser in the laser passes through the driven cavity is the highest point of the interference peak.

2. The single longitudinal mode pulse laser feedback control circuit according to claim 1, characterized in that: The optical signal acquisition module includes: a Pin tube and an A / D sampling circuit, wherein the Pin tube is arranged in the optical path of the laser and connected to the input end of the A / D sampling circuit, and is used to receive the feedback optical analog signal VI; The output end of the A / D sampling circuit is connected to the input end of the signal processing module, and is used to convert the feedback optical analog signal VI into a digital signal.

3. The single longitudinal mode pulse laser feedback control circuit according to claim 1, characterized in that: The laser comprises an RTP crystal, and the RTP crystal is arranged in the optical path of the laser; The linear pulse voltage control module is connected to the voltage input end of the RTP crystal, and the other end of the crystal RTP is grounded.

4. The single longitudinal mode pulse laser feedback control circuit according to claim 1, characterized in that: The laser comprises an acousto-optic modulator, which is electrically connected to the signal processing module and is used to control the output of the single longitudinal mode pulse laser.

5. The single longitudinal mode pulse laser feedback control circuit according to claim 1, characterized in that: The linear pulse voltage control module includes: a first resistor, a second resistor, a first transistor, a diode, a fifth resistor, and a capacitor, and the collector end of the optical coupler is connected to the input end of the first resistor, the input end of the second resistor, and the first end of the first transistor; The output end of the first resistor is connected to a +12V DC voltage; The output end of the second resistor is connected to the cathode end of the optocoupler, the S pole of the first transistor, and the diode; One end of the fifth resistor is connected to the D electrode of the first transistor, and the other end is connected to the HV DC high voltage; The generating end of the optical coupler is grounded; The S terminal of the first transistor is connected to one end of the diode; The other end of the diode is connected to one end of the capacitor; The other end of the capacitor is grounded and connected to one end of the third resistor and the S electrode of the second transistor; The D electrode of the second transistor is connected to one end of the fourth resistor.

6. The single longitudinal mode pulse laser feedback control circuit according to claim 1, characterized in that: The transistor is a metal-oxide semiconductor field effect transistor.

7. The single longitudinal mode pulse laser feedback control circuit according to claim 1, characterized in that: The optical signal acquired by the optical signal acquisition module is an optical signal of the laser transmitted in the resonant cavity of the laser.

8. A single longitudinal mode pulse laser feedback control method, applied to the single longitudinal mode pulse laser feedback control circuit as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: a) Real-time collection of optical signals in the laser; b) determining whether the optical signal meets the output condition of the single longitudinal mode pulse laser; c) If the laser reaches the target, the single longitudinal mode pulse laser is output; if the laser reaches the target, the voltage input to the laser is adjusted. Return to step a) until the output condition is met.

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