Automatic frequency stabilization circuit of semiconductor laser

Abstract

The utility model discloses an automatic frequency stabilization circuit of a semiconductor laser. The automatic frequency stabilization circuit comprises a bandwidth control circuit, a proportional feedback control circuit and an integral feedback control circuit, the bandwidth control circuit comprises a switch SW1 and a switch SW2, the switch SW1 is used for controlling whether the capacitor C1 enters a signal transmission link or not, and the switch SW2 is used for controlling whether the capacitor C2 enters the signal transmission link or not; the proportional feedback control circuit comprises a switch SW3, and the switch SW3 is used for controlling whether the resistor R3 enters a signal transmission link or not; the integral feedback control circuit comprises a switch SW4, and the switch SW4 is used for controlling whether the capacitor C4 enters the signal transmission link or not. According to the utility model, two bandwidth adjusting switches and corresponding capacitors are added to the bandwidth control circuit part; a proportional feedback intensity adjusting switch and a corresponding resistor are added to the proportional feedback control circuit part; an integral feedback intensity adjusting switch and a corresponding capacitor are added to the integral feedback control circuit part. And high-efficiency and high-performance automatic frequency stabilization of the laser is realized through a program control switch.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor laser frequency stabilization, in particular to a semiconductor laser automatic frequency stabilization circuit. Background Art

[0002] Semiconductor precision lasers are widely used in quantum computing, quantum communication, and quantum precision measurement, and are essential components for quantum technology applications. When semiconductor precision lasers are used in quantum precision measurement, the laser's output frequency often needs to be stabilized and locked to the transition spectrum of atoms, molecules, and other particles. Therefore, the laser frequency stabilization circuit plays a key role in laser performance. This was discovered during the development and application of existing semiconductor laser automatic frequency stabilization circuit products.

[0003] 1) The inherent linewidth of existing lasers can reach several MHz to hundreds of kHz, which exceeds the linewidth level of most atomic spectra. Therefore, the laser frequency stabilization circuit should reduce the impact on the inherent high performance of the laser during the locking process of the laser frequency;

[0004] 2) The frequency of the laser output changes with the changes in the external environment. The rate of change is usually about a few Hz to tens of Hz, which is a slow drift, but it needs to be compensated by a strong feedback intensity;

[0005] 3) When the laser is performing laser frequency stabilization, in order to enable the laser frequency to be locked quickly and smoothly, a higher laser feedback bandwidth and error signal are required. A higher feedback bandwidth will limit the feedback strength, and excessive feedback strength will cause oscillation. Utility Model Content

[0006] The purpose of the present utility model is to provide a semiconductor laser automatic frequency stabilization circuit to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions: a semiconductor laser automatic frequency stabilization circuit, comprising a bandwidth control circuit, a proportional feedback control circuit, and an integral feedback control circuit;

[0008] The bandwidth control circuit includes switches SW1 and SW2. Switch SW1 is used to control whether capacitor C1 enters the signal transmission link, and SW2 is used to control whether capacitor C2 enters the signal transmission link.

[0009] The proportional feedback control circuit includes a switch SW3, which is used to control whether the resistor R3 enters the signal transmission link;

[0010] The integral feedback control circuit includes a switch SW4 , and the switch SW4 is used to control whether the capacitor C4 enters the signal transmission link.

[0011] Preferably, one end of the capacitor C1 is grounded, and the other end of the capacitor C1 is connected to the main circuit via the switch SW1.

[0012] Preferably, both ends of the capacitor C2 are connected in parallel to the main circuit, and one end of the capacitor C2 is connected to the switch SW2.

[0013] Preferably, both ends of the resistor R3 are connected in parallel to the main circuit, and one end of the resistor R3 is connected to the switch SW3.

[0014] Preferably, both ends of the capacitor C4 are connected in parallel to the main circuit, and one end of the capacitor C4 is connected to the switch SW4.

[0015] Preferably, the switch SW1 , the switch SW2 , the switch SW3 , and the switch SW4 are all chip-type electronically controlled switches.

[0016] Preferably, the values ​​of capacitors C1 and C2 are both the capacitors C B The value of resistor R3 is 10 times the value of the resistor R in the main circuit. P The resistance value is 1 / 10, and the value of capacitor C4 is the capacitor C in the main circuit. I 1 / 10 of the capacitance value.

[0017] Compared with existing technologies, the present invention offers the following advantages: It adds two bandwidth adjustment switches and corresponding capacitors to the bandwidth control circuit; adds a proportional feedback intensity adjustment switch and corresponding resistor to the proportional feedback control circuit; and adds an integral feedback intensity adjustment switch and corresponding capacitor to the integral feedback control circuit. By program-controlled switches, efficient and high-performance automatic frequency stabilization of the laser is achieved. This invention can be used to improve the frequency performance of laser output after automatic frequency stabilization of a semiconductor laser and reduce laser frequency noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a circuit schematic diagram of the utility model. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] like Figure 1As shown in the figure, the present invention provides a technical solution: a semiconductor laser automatic frequency stabilization circuit. The left half is a schematic diagram of the bandwidth control circuit for laser frequency stabilization, and the right half is a schematic diagram of the proportional feedback control circuit and integral feedback control circuit for laser frequency stabilization. The demodulated signal in the laser frequency stabilization circuit is input from the left side into the bandwidth control circuit, generating an error signal for implementing PI (proportional-integral) feedback; the error signal is divided into two paths, the upper path entering the proportional feedback control circuit to generate a proportional feedback signal, and the lower path entering the integral feedback control circuit to generate an integral feedback signal; the feedback signal is input into the laser drive circuit to achieve laser frequency stabilization.

[0021] Compared with the general semiconductor laser automatic frequency stabilization related circuit, this embodiment has made the following improvements: (1) Figure 1 Switches SW1 and SW2 are added to the bandwidth control circuit on the left. The two switches control whether capacitors C1 and C2 enter the signal transmission link; (2) Figure 1 A switch SW3 is added to the proportional feedback control circuit on the upper right side, which controls whether the resistor R3 enters the signal transmission link; (3) Figure 1 A switch SW4 is added to the integral feedback control circuit on the lower right side, which controls whether the capacitor C4 enters the signal transmission link.

[0022] At the beginning of laser frequency stabilization, SW1 and SW2 are open, SW3 is closed, and SW4 is closed. At this time, the error signal bandwidth is approximately 100Hz to 1kHz, the proportional feedback signal amplification factor is approximately 1, and the integral feedback signal does not cause oscillation.

[0023] After the laser frequency is locked and stabilized: SW1 and SW2 are closed at the same time, and SW3 is immediately disconnected. Capacitor C2 is connected in parallel to the bandwidth control circuit, and the values ​​of C1 and C2 are the original capacitor C B When the value is 10 times that of the original value, the bandwidth of the bandwidth control circuit is reduced to 10Hz~100Hz; the parallel connection of resistor R3 and the proportional feedback control circuit is disconnected, and the value of R3 is the original resistance R P When the resistance value is 1 / 10, the amplification factor of the proportional feedback control circuit is increased to 10 times the original value;

[0024] After the laser frequency is locked: SW4 is disconnected, the parallel connection between capacitor C4 and the integral feedback control circuit is disconnected, and the value of C4 is the original capacitor C I When the capacitance is 1 / 10 of that, the integration time of the integral feedback control circuit is 1 / 10 of the original one.

[0025] At this time, the laser frequency stabilization is in a locked state with good performance.

[0026] These four switches are all chip-based electronically controlled switches and can be controlled by a single-chip microcomputer (MCU) or a field-programmable gate array (FPGA) program. The basic working process is as follows:

[0027] In the default state, the two switches in the bandwidth control circuit of the laser frequency stabilization are in the open state, and the switches of the proportional feedback control circuit and the integral feedback control circuit are in the closed state. At this time, the bandwidth of the circuit is large, the proportional feedback strength is small, and the laser begins to lock;

[0028] After the laser enters the lock state, the laser frequency stabilization program continuously detects the error signal. If the fluctuation of the error signal is lower than the set strong lock threshold, it means that the laser has entered a relatively stable frequency stabilization working state.

[0029] When the error signal fluctuates below the strong lock threshold, the program sets the two switches in the bandwidth control circuit to close, significantly reducing the bandwidth of the error signal; then the program immediately sets the switch in the proportional feedback control circuit to open, significantly increasing the proportional feedback strength; the program also detects the stability of the laser output frequency;

[0030] If the laser output frequency is still the target frequency to be locked, it means that the laser frequency stabilization has successfully entered the low-bandwidth strong lock state. The program sets the switch in the integral feedback control circuit to be disconnected to increase the integral feedback strength. If the laser output frequency is unlocked, the strong lock fails and returns to the default state to enter step 1).

[0031] This embodiment achieves high-performance automatic frequency stabilization of the laser output frequency. The frequency stabilization circuit only compensates for the impact of environmental fluctuations on the laser without introducing additional noise interference to the laser. When the laser is locked, high bandwidth is first used to enable the laser to lock smoothly, and then a low-bandwidth strong lock state is entered.

[0032] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A semiconductor laser automatic frequency stabilization circuit, characterized in that: It includes a bandwidth control circuit, a proportional feedback control circuit and an integral feedback control circuit; The bandwidth control circuit includes switches SW1 and SW2. Switch SW1 is used to control whether capacitor C1 enters the signal transmission link, and SW2 is used to control whether capacitor C2 enters the signal transmission link. The proportional feedback control circuit includes a switch SW3, which is used to control whether the resistor R3 enters the signal transmission link; The integral feedback control circuit includes a switch SW4 , and the switch SW4 is used to control whether the capacitor C4 enters the signal transmission link.

2. The semiconductor laser automatic frequency stabilization circuit according to claim 1, characterized in that: One end of the capacitor C1 is grounded, and the other end of the capacitor C1 is connected to the main circuit via the switch SW1 .

3. The semiconductor laser automatic frequency stabilization circuit according to claim 2, characterized in that: Both ends of the capacitor C2 are connected in parallel to the main circuit, and one end of the capacitor C2 is connected to the switch SW2.

4. The semiconductor laser automatic frequency stabilization circuit according to claim 1, characterized in that: Both ends of the resistor R3 are connected in parallel to the main circuit, and one end of the resistor R3 is connected to the switch SW3.

5. The semiconductor laser automatic frequency stabilization circuit according to claim 1, characterized in that: Both ends of the capacitor C4 are connected in parallel to the main circuit, and one end of the capacitor C4 is connected to the switch SW4.

6. The semiconductor laser automatic frequency stabilization circuit according to claim 1, characterized in that: The switch SW1 , the switch SW2 , the switch SW3 , and the switch SW4 are all chip-type electronically controlled switches.

7. The semiconductor laser automatic frequency stabilization circuit according to claim 1, characterized in that: The values ​​of capacitors C1 and C2 are both the capacitors C in the main circuit. B The value of resistor R3 is 10 times the value of the resistor R in the main circuit. P The resistance value is 1 / 10, and the value of capacitor C4 is the capacitor C in the main circuit. I 1 / 10 of the capacitance value.

Images