An optical waveform shaping circuit for a MOPA laser seed source

Abstract

A waveform shaping circuit for a seed source of a MOPA laser includes a laser, a MOSFET, a driving circuit, and resistors R3, R5, R6, and R8, an inductor L1, and diodes D1 to D3. Resistor R3 is a current-limiting resistor; one end is connected to the positive power supply, and the other end is connected in series with resistor R8 and then to the first input terminal of the laser. Resistor R5 is connected in series with inductor L1 and then in parallel across resistor R8. Resistor R6 is connected in series with diode D1 and then in parallel across resistor R8. The output terminal of the driving circuit is connected to the gate (G) of the MOSFET to control its on / off state. One of the source (S) and drain (D) terminals of the MOSFET is grounded, and the other is connected to the second input terminal of the laser. The anodes of diodes D2 and D3 are connected to the second input terminal of the laser, and their cathodes are connected to the first input terminal. After amplification by the downstream optical amplification system, this invention effectively suppresses the nonlinear amplification of the downstream optical waveform, ensuring that the output optical waveforms do not exhibit significant overshoot.

Description

Technical Field

[0001] This invention relates to the field of lasers, and more particularly to a waveform shaping circuit for a seed source of a MOPA laser. Background Technology

[0002] MOPA lasers refer to nanosecond pulsed fiber lasers based on an electrically modulated seed source and a multi-stage power amplifier. They are mainly used in laser marking, precision cutting, welding, drilling, and other applications. Physically, MOPA is a laser configuration relative to a single-oscillator configuration; its full English name is Main Oscillator and Power Amplifier. Internally, after outputting the seed source, a MOPA laser typically has a two-stage optical amplification system to amplify the seed source before output. However, existing MOPA laser back-end two-stage optical amplification systems exhibit significant gain overshoot, such as... Figure 1 As shown, this results in a very high peak optical power for the first 50 ns of each output optical waveform, which risks damaging the subsequent optical path. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the technical defect in the prior art where the peak optical power of each optical waveform output by MOPA is very high in the first 50 ns, which poses a risk of damaging the subsequent optical path. The present invention provides an optical waveform shaping circuit for the seed source of MOPA laser.

[0004] The optical waveform shaping circuit for MOPA laser seed source provided by the present invention includes a laser, a MOS transistor, a driving circuit, and also includes resistors R3, R5, R6, R8, inductor L1, and diodes D1 to D3.

[0005] Resistor R3 is a current-limiting resistor used to limit the current flowing through the laser. One end of resistor R3 is connected to the positive power supply, and the other end is connected in series with resistor R8 and then connected to the first input terminal of the laser. Resistor R5 is connected in series with inductor L1 and then in parallel across resistor R8. Together with resistor R8, it is used to prevent sudden changes in the current flow when the MOSFET is turned on, thus slowing down the current rise time. Resistor R6 is connected in series with diode D1 and then in parallel across resistor R8. It is used to release the energy stored in inductor L1 when the MOSFET is turned off. The conduction direction of diode D1 is from the first input terminal of the laser to resistor R3.

[0006] The output of the drive circuit is connected to the gate (G) of the MOSFET to control its on / off state. One of the source (S) and drain (D) of the MOSFET is grounded, and the other is connected to the second input terminal of the laser. The anodes of diodes D2 and D3 are connected to the second input terminal of the laser, and the cathodes are connected to the first input terminal of the laser. Diodes D2 and D3 are clamping diodes to prevent excessive reverse voltage from damaging the laser.

[0007] Furthermore, in the optical waveform shaping circuit for the seed source of the MOPA laser of the present invention, the resistor R8 is 10Ω±20%, the resistor R5 is 1Ω±20%, and the inductor L1 is 470nH±20%.

[0008] Furthermore, in the optical waveform shaping circuit for the MOPA laser seed source of the present invention, the resistor R6 is 10 ohms.

[0009] Furthermore, in the optical waveform shaping circuit for the seed source of the MOPA laser of the present invention, diodes D1 to D3 are of type ES1D-E3 / 5AT.

[0010] Furthermore, in the optical waveform shaping circuit for the seed source of the MOPA laser of the present invention, the MOS transistor is implemented using EPC2037, the second and fourth pins of EPC2037 are grounded, and the third pin is connected to the second input terminal of the laser.

[0011] Furthermore, in the optical waveform shaping circuit for the seed source of the MOPA laser of the present invention, the working positive power supply is connected in series with a power supply filter capacitor and then grounded. The power supply filter capacitor consists of four capacitors connected in parallel with a size ratio of 22μF, 22μF, 0.1μF, and 0.1μF.

[0012] Furthermore, in the optical waveform shaping circuit for the seed source of the MOPA laser of the present invention, the driving circuit includes a chip LMG1020. The VDD pin of LMG1020 is connected in series with a feedthrough filter and then grounded. The IN+ pin is connected to an electrical pulse signal to control the output of LMG1020, thereby controlling the on / off state of the MOS transistor. The GND pin and the IN- pin are grounded, and the OUTL and OTH pins are connected together to the gate of the MOS transistor.

[0013] The optical waveform shaping circuit for MOPA laser seed source of the present invention has the following technical effects: After the seed source is shaped by the optical waveform shaping circuit of the present invention, it can effectively suppress the nonlinear amplification of the back-end optical waveform after being amplified by the back-end optical amplification system, so that the output optical waveforms do not have obvious overshoot. Attached Figure Description

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0015] Figure 1 These are waveform diagrams of a single waveform from the seed source of an existing MOPA laser and a single waveform amplified by a back-end two-stage optical amplification system.

[0016] Figure 2 This is a circuit diagram of an embodiment of the optical waveform shaping circuit for a seed source of a MOPA laser according to the present invention;

[0017] Figure 3 This is a simulation result diagram of the optical waveform shaping circuit for the seed source of the MOPA laser according to the present invention. Detailed Implementation

[0018] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] refer to Figure 2 The waveform shaping circuit for the seed source of the MOPA laser in this embodiment includes a laser, a MOSFET Q1, a driving circuit, and also includes resistors R3, R5, R6, R8, inductor L1, and diodes D1 to D3.

[0020] Resistor R3 is a current-limiting resistor, with a value of 3mΩ in this embodiment, used to limit the current flowing through the laser. Its size can be designed according to actual needs. One end of resistor R3 is connected to the positive power supply VCC_LD, and the other end is connected in series with resistor R8 and then connected to the first input terminal of the laser. The positive power supply VCC_LD is selected according to the operating power requirements of different lasers. The positive power supply VCC_LD is connected in series with a power filter capacitor and then grounded. The power filter capacitor consists of four capacitors C4 to C7 connected in parallel with a size ratio of 22μF, 22μF, 0.1μF, and 0.1μF.

[0021] Resistor R5 is connected in series with inductor L1 and then in parallel across resistor R8. Together with resistor R8, they are used to prevent sudden changes in the current flow when MOSFET Q1 is turned on, thus slowing down the current rise time. Resistor R6 is connected in series with diode D1 and then in parallel across resistor R8. This is used to release the energy stored in inductor L1 when MOSFET Q1 is turned off. The conduction direction of diode D1 is from the first input terminal of the laser to resistor R3.

[0022] The output of the drive circuit is connected to the gate (G) of MOSFET Q1 to control the on / off state of the MOSFET. One of the source (S) and drain (D) of MOSFET Q1 is grounded, and the other is connected to the second input terminal of the laser. The anodes of diodes D2 and D3 are connected to the second input terminal of the laser, and the cathodes are connected to the first input terminal of the laser. Diodes D2 and D3 are clamping diodes and fast recovery diodes to prevent excessive reverse voltage from damaging the laser.

[0023] In this embodiment, resistor R8 is 10Ω, resistor R5 is 1Ω, inductor L1 is 470nH, resistor R6 is 10 ohms, and diodes D1 to D3 are of type ES1D-E3 / 5AT.

[0024] In practical applications of two-stage optical amplification systems, because the light is pulsed, there will be a step response and obvious overshoot during the amplification process. The overshoot response time is only related to the rise time of the pulse and is not related to the pulse width. Therefore, the peak overshoot time is about 50ns and remains basically constant. Thus, the values ​​of the parameters mentioned above in this invention can be applied to different subsequent amplification circuits.

[0025] The MOSFET Q1 is implemented using an EPC2037. Pins 2 and 4 of the EPC2037 are grounded, and pin 3 is connected to the second input terminal of the laser.

[0026] The driving circuit includes the LMG1020 chip. The VDD pin of the LMG1020 is connected in series with a feedthrough filter and then grounded. The IN+ pin is connected to the Pulse Signal to control the output of the LMG1020, thereby controlling the on / off state of the MOSFET. The GND pin and the IN- pin are grounded. The OUTL and OTH pins are connected together to the gate of the MOSFET.

[0027] Under the control of the electrical pulse signal, the driving circuit generates a driving pulse input to the gate (G) of MOSFET Q1, thereby controlling the on / off state of MOSFET Q1. When MOSFET Q1 is off, the working circuit of the laser is disconnected, and the laser stops working. When MOSFET Q1 is on, the second input terminal of the laser is essentially grounded, and the working circuit of the laser operates normally, emitting a shaped seed source.

[0028] The circuit based on this invention was simulated, and the simulation results are as follows: Figure 3As shown, curve a represents the seed source waveform of the laser output when the positive power supply VCC_LD is 5V and 10V respectively, and waveform curve b is shown. Each waveform in waveform curve b, after being processed by the subsequent two-stage optical amplification system, effectively resolves the overshoot phenomenon and reduces the risk of damaging the subsequent optical path. It should be understood that the application scenarios of this invention are not limited to a two-stage optical amplification system; multiple stages of optical amplification systems are also possible. However, since a two-stage optical amplification system is sufficient to effectively resolve the overshoot phenomenon, it is generally sufficient to use a two-stage optical amplification system unless a higher amplification factor is required in the subsequent stage.

[0029] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. An optical waveform shaping circuit for a MOPA laser seed source, comprising a laser, a MOS tube, a driving circuit, characterized in that, It also includes resistors R3, R5, R6, and R8, inductor L1, and diodes D1 to D3; Resistor R3 is a current-limiting resistor used to limit the current flowing through the laser. One end of resistor R3 is connected to the positive power supply, and the other end is connected in series with resistor R8 and then connected to the first input terminal of the laser. Resistor R5 is connected in series with inductor L1 and then in parallel across resistor R8. Together with resistor R8, it is used to prevent sudden changes in the current flow when the MOSFET is turned on, thus slowing down the current rise time. Resistor R6 is connected in series with diode D1 and then in parallel across resistor R8. It is used to release the energy stored in inductor L1 when the MOSFET is turned off. The conduction direction of diode D1 is from the first input terminal of the laser to resistor R3. The output terminal of the drive circuit is connected to the gate of the MOSFET to control the on / off state of the MOSFET. One of the source and drain terminals of the MOSFET is grounded, and the other is connected to the second input terminal of the laser. The anodes of diodes D2 and D3 are connected to the second input terminal of the laser, and the cathodes are connected to the first input terminal of the laser. Diodes D2 and D3 are clamping diodes to prevent excessive reverse voltage from damaging the laser. Resistor R8 is 10Ω±20%, resistor R5 is 1Ω±20%, inductor L1 is 470nH±20%, and resistor R6 is 10 ohms.

2. The optical waveform shaping circuit for a MOPA laser seed source of claim 1, wherein, The diodes D1 to D3 are model numbers ES1D-E3 / 5AT.

3. The optical waveform shaping circuit for a MOPA laser seed source of claim 1, wherein, The MOSFET is implemented using an EPC2037. Pins 2 and 4 of the EPC2037 are grounded, and pin 3 is connected to the second input terminal of the laser.

4. The optical waveform shaping circuit for a MOPA laser seed source of claim 1, wherein, The working positive power supply is connected in series with a power filter capacitor and then grounded. The power filter capacitor consists of four capacitors connected in parallel with a size ratio of 22μF, 22μF, 0.1μF, and 0.1μF.

5. The optical waveform shaping circuit for a MOPA laser seed source of claim 1, wherein, The driving circuit includes the LMG1020 chip. The VDD pin of the LMG1020 is connected in series with a feedthrough filter and then grounded. The IN+ pin is connected to an electrical pulse signal to control the output of the LMG1020, thereby controlling the on / off state of the MOSFET. The GND pin and the IN- pin are grounded. The OUTL and OTH pins are connected together to the gate of the MOSFET.

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