A high-response bandwidth grating external cavity control device and frequency stabilized laser system

Abstract

This invention belongs to the field of laser technology and discloses a high-response-bandwidth grating external cavity control device and a frequency-stabilized laser system. The grating external cavity control device includes a grating holder, a magnetostrictive actuator, and a driving current source. The grating holder is used to set the grating, and the magnetostrictive actuator is used to drive the grating holder to rotate, thereby changing the grating angle and external cavity length of the laser grating. The magnetostrictive actuator includes a magnetostrictive rod, a fixed base, a permanent magnet, and a solenoid. One end of the magnetostrictive rod is fixed to the fixed base, and the other end serves as the free end of the magnetostrictive actuator. The solenoid is sleeved around the outer circumference of the magnetostrictive rod and is used to provide an axial magnetic field to the magnetostrictive rod under the drive of the current source. The permanent magnet is used to provide a bias magnetic field to the magnetostrictive rod. The frequency-stabilized laser system involves the specific structures of three feedback loops of two types: grating and current, and frequency-stabilized closed-loop loops for single-actuator and dual-actuator grating external cavity control devices, respectively. This invention improves the response bandwidth of the laser, which can greatly improve the linewidth and noise characteristics of the laser, and enhance its environmental adaptability and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of laser technology, specifically relating to a high-response-bandwidth grating external cavity control device for narrow-linewidth lasers and a corresponding frequency-stabilized laser system. Background Technology

[0002] Semiconductor lasers are crucial devices widely used in scientific research, industry, and medicine. Their performance is critical to the effectiveness of these applications. Among them, the External Cavity Diode Laser (ECDL) is a classic solution for high-end semiconductor laser applications, enabling narrowing of the linewidth and continuous frequency tuning of the laser output from the laser diode. Controlling either the injection current of the laser diode or the grating position of the ECDL's external cavity (changing the position can alter the cavity length and grating feedback angle) can change the laser frequency, allowing for open-loop tuning or closed-loop correction. However, because current adjustment causes synchronous changes in the laser's output frequency and power, and because the electrical and physical characteristics of the semiconductor laser diode, as well as the laser's threshold current, slope efficiency, thermal effects, and nonlinear effects, limit the adjustment range of the injection current, large-scale current adjustments can lead to a sharp decline in laser performance or even damage. Furthermore, grating control typically involves adjustments to the optical path and mechanical structure, the physical characteristics and precision of which limit the adjustment range of the grating control. Due to the requirements of mode competition, the feedback intensity cannot change too much during continuous non-mode-hopping tuning of the ECDL grating external cavity, resulting in a limited stroke for the final grating mechanical structure. More importantly, the response speed of the grating optomechanical system and the drive mechanism directly affects the response bandwidth of laser frequency modulation via the grating. The limitations on the range or adjustment of frequency continuous tuning, current, and grating are all based on the requirement for continuous non-mode-hopping tuning characteristics. Technical solutions typically employ a feedforward approach, synchronously adjusting the grating and current to increase the non-mode-hopping continuous tuning range.

[0003] Currently, commonly used ECDL laser grating external cavity control schemes are based on piezoelectric PZT (piezoelectric ceramic actuator) control mechanisms. By adjusting the driving voltage on the PZT, the length of the actuator is changed, thereby altering the angle or position of the grating and achieving low-speed control of the laser frequency. This is due, in part, to the insufficient response bandwidth of piezoelectric ceramic materials, typically in the kHz range, and the driving force in the hundreds of Newtons range; furthermore, traditional PZT grating drive mechanisms are limited by the elastic recovery speed of the mechanical structure under elastic deformation. The limited response bandwidth and sweep speed of PZT-based grating drive mechanisms result in a limited stable frequency closed-loop bandwidth. High-speed frequency control or tuning, however, requires changing the injection current. However, due to the different response bandwidths, response speeds, and adjustment ranges of current and grating control, the dynamic range of the collaborative tuning system is limited in open-loop operation, and the feedback loop correction capability and closed-loop bandwidth are limited in frequency stabilization closed-loop feedback. Ultimately, the frequency noise suppression capability of the laser's frequency stabilization closed loop is limited within the bandwidth range. The frequency-stabilized laser will lose lock due to mode hopping caused by long-term drift caused by various factors, which restricts the stability of the laser and its frequency stabilization system during long-term operation.

[0004] In summary, due to the limited bandwidth of the PZT driving grating feedback loop when acting alone, even with a feedforward approach to improve the continuously tunable range, the limited operating bandwidth still makes the laser output frequency and noise characteristics sensitive to the environment. This results in limited environmental adaptability and long-term continuous operation stability of semiconductor lasers and their frequency stabilization systems. Therefore, it is necessary to invent a novel laser grating external cavity control device and frequency stabilization method to address the shortcomings of existing methods in terms of response bandwidth. Summary of the Invention

[0005] To address the technical problem of slow mechanical movement speed and large time delay in the external cavity of semiconductor laser gratings, which limits the bandwidth of its frequency stabilization response, this invention proposes a high-bandwidth grating external cavity control device and laser system. By using a magnetostrictive actuator to drive the grating, the position and angle of the grating in the laser are rapidly controlled, enabling rapid tuning of the laser output frequency by the external cavity of the grating and a high-bandwidth frequency stabilization closed loop.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a high response bandwidth grating external cavity control device, comprising: a magnetostrictive actuator and a current source; the magnetostrictive actuator is used to drive the grating of the laser to rotate, so as to change the grating angle and external cavity length of the laser grating external cavity;

[0007] The magnetostrictive actuator includes a magnetostrictive rod, a fixed base, a permanent magnet, and a solenoid. One end of the magnetostrictive rod is fixed to the fixed base, and the other end serves as the free end of the magnetostrictive actuator. The solenoid is sleeved on the outer periphery of the magnetostrictive rod and is used to provide an axial magnetic field to the magnetostrictive rod under the drive of a current source. The permanent magnet is used to provide a bias magnetic field to the magnetostrictive rod.

[0008] The high-response-bandwidth grating external cavity single actuator control device further includes a grating mounting bracket for setting the grating. The grating mounting bracket is a U-shaped structure integrally formed of elastic material. One side of the U-shaped structure is a support block fixedly mounted on the laser base, and the other side is an elastic block for setting the grating. The fixed end of the magnetostrictive actuator is fixedly connected to the support block, and the free end is connected to the elastic block. The magnetostrictive actuator is used to drive the elastic block to rotate around the connection between the support block and the elastic block.

[0009] A rebound spring is also provided between the support block and the elastic block.

[0010] The magnetostrictive actuator also includes a fixed base at one end of the fixed end of the magnetostrictive rod and a magnetic shield for shielding magnetic field interference. The magnetic shield has an opening for the movable end of the magnetostrictive rod to extend out.

[0011] The high-response-bandwidth grating external cavity single actuator control device further includes a grating mounting bracket for setting the grating. One end of the grating mounting bracket is connected to the laser base via a rotating shaft, and a magnetostrictive actuator is respectively provided on both sides of the other end. The fixed end of the magnetostrictive actuator is connected to the laser base, and the free end is used to drive the grating mounting bracket to rotate clockwise and counterclockwise, respectively.

[0012] The high-response-bandwidth grating external cavity dual actuator control device further includes two bosses located on both sides of the grating fixing frame, the bosses being fixedly mounted on the laser base, and the fixed end of the magnetostrictive actuator being fixedly mounted on the bosses.

[0013] The high-response-bandwidth grating external cavity dual-actuator control device includes one magnetostrictive actuator directly driven by the grating feedback loop signal, and the other magnetostrictive actuator driven by the signal after the grating feedback loop signal is inverted.

[0014] Furthermore, the present invention also provides a high-response-bandwidth frequency-stabilized laser system, including a laser body, the laser body including a laser diode, a collimating lens, a grating and a laser base, and the laser body also including the laser grating external cavity control device.

[0015] The high-response-bandwidth frequency-stabilized laser system further includes a frequency reference device, a driving constant current source, a modulation signal generator, and a multiplier and a low-pass filter.

[0016] The constant current source is used to input current into the laser diode to drive it to emit light. The modulator generator has two output terminals. The first output terminal is connected to the input terminal of the constant current source and is used to output the modulation signal. The second output terminal shifts the modulation signal and sends it to the first input terminal of the multiplier. The output laser of the laser diode is output after passing through a collimating lens and a grating. The output laser is then output to the second input terminal of the multiplier after passing through a frequency reference device. The frequency discrimination signal required for frequency stabilization is obtained by passing through the multiplier and a low-pass filter.

[0017] The frequency discrimination signal is divided into two paths. The first path passes through the first PID controller to form a feedback electrical signal, which is then divided into two branches after passing through the feedforward controller. The first branch is output to the current source to form a grating feedback loop; the second branch is output to the driving constant current source to form a current feedback loop.

[0018] The second path, after passing through the second PID controller, outputs a feedback electrical signal to the laser diode, forming a high-speed current feedback loop.

[0019] The high-response-bandwidth frequency-stabilized laser system further includes a first filter, a second filter, a phase shifter, an adder, and a sweep signal generator;

[0020] The first filter is set at the input terminal of the first PID controller, the second filter is set at the input terminal of the second PID controller, and the phase shifter is set at the output terminal of the second PID controller.

[0021] The first input terminal of the adder is connected to the output terminal of the sweep frequency signal generator, and the second input terminal is connected to the output terminal of the feedforward controller; the output terminal of the adder is connected to the input terminal of the constant current source.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. This invention proposes a high-response-bandwidth grating external cavity control device and laser system. The grating external cavity is driven by a magnetostrictive actuator. Due to the advantages of the magnetostrictive material's high response bandwidth (up to megahertz) and greater driving force, the efficiency and response performance of grating adjustment are improved, and the grating feedback response characteristics of the laser are enhanced. The response bandwidth can reach the MHz level.

[0024] 2. This invention also stabilizes the laser frequency by constructing a high-bandwidth, fast-response closed-loop feedback control system, which enhances the ability to suppress frequency noise and frequency drift within the laser bandwidth, suppresses laser frequency fluctuations over a wider range and at higher frequencies, reduces the impact of environmental interference on laser performance, enhances the anti-interference capability of the overall laser system, and improves long-term stability and environmental adaptability.

[0025] In summary, this invention uses magnetostrictive materials and magnetostrictive actuator devices as grating external cavity driving mechanisms, which is of great significance for high-response speed control devices and low-noise, high-bandwidth frequency stabilization systems. It can greatly improve the linewidth and noise characteristics of lasers, and enhance environmental adaptability and long-term stability. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating an application example of a high-response-bandwidth grating external cavity control device provided in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of a high-response-bandwidth single-actuator grating external cavity control device provided in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of the structure of the magnetostrictive actuator provided in an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram illustrating the application of a high-response-bandwidth single-actuator grating external cavity control device provided in Embodiment 1 of the present invention in a laser.

[0030] Figure 5 This is a schematic diagram of a high-response-bandwidth dual-actuator grating external cavity control device provided in Embodiment 2 of the present invention;

[0031] Figure 6 This is a schematic diagram illustrating the application of a high-response-bandwidth dual-actuator grating external cavity control device provided in Embodiment 2 of the present invention in a laser.

[0032] Figure 7 This is a schematic diagram of a high-response-bandwidth frequency-stabilized laser system provided in Embodiment 4 of the present invention;

[0033] In the diagram: 1-Laser diode, 2-Collimating lens, 3-Grate, 4-Grate holder, 5-Magnetostrictive actuator, 6-Rebound spring, 7-Rotating shaft, 8-Magnetostrictive rod, 9-Solenoid, 10-Current source, 11-Permanent magnet, 12-Fixed base, 13-Magnetic shield, 14-Laser body, 15-Frequency reference device, 16-Sweep signal generator, 17-Driver constant current source, 18-Adder, 19-Modulation signal generator, 20-Multiplier, 21-Low-pass filter, 22-First filter, 23-First PID controller, 24-Feedforward controller, 25-Second filter, 26-Second PID controller, 27-Phase shifter, 28-Laser base, 29-Boss. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] Embodiment 1 of the present invention provides an implementation example of high-response bandwidth single-actuator grating external cavity control, which relates to... Figure 1 , 2 As shown in 3 and 4. Figure 1 As shown, the grating needs to move back and forth around its axis near a suitable position; as Figure 2 As shown, the laser grating external cavity single actuator control device includes: a grating 3, a grating holder 4, a magnetostrictive actuator 5, and a return spring 6. The grating holder 4 is used to fix the grating 3 in place, and the magnetostrictive actuator 5 is used to drive the grating holder 4 to move, thereby changing the grating angle and external cavity length of the laser grating external cavity.

[0037] Specifically, the grating holder 4, as a moving component, is used to achieve a stable connection between the grating 3 and the magnetostrictive actuator 5. The thrust generated by the magnetostrictive actuator 5 during operation is effectively transmitted to the grating 3 through the grating holder 4, ensuring precise coordination and functional linkage between the two. The magnetostrictive actuator 5, on the one hand, achieves precise control of the grating movement based on its high stress and strong thrust characteristics, and on the other hand, achieves high-speed control of the grating movement based on its high response bandwidth characteristics. The rebound spring 6, on the one hand, provides prestress to the magnetostrictive actuator to optimize its working state, and on the other hand, assists the grating holder 4 in elastic rebound, improving the system's motion response speed.

[0038] like Figure 3 As shown, in this embodiment, the magnetostrictive actuator 5 includes a magnetostrictive rod 8, a fixed base 12, a permanent magnet 11, and a solenoid 9. One end of the magnetostrictive rod 8 is fixed on the fixed base 12, and the other end serves as the free end of the magnetostrictive actuator 5. The solenoid 9 is sleeved on the outer periphery of the magnetostrictive rod 8 and is used to provide an axial magnetic field for the magnetostrictive rod 8 under the drive of the current source 10. The permanent magnet 11 is used to provide the bias magnetic field required for the optimal telescopic characteristic operating point of the magnetostrictive rod 8.

[0039] Specifically, in this embodiment, permanent magnets 11 are uniformly arranged around the outer periphery of solenoid 9 to provide a uniform magnetic field to the location of magnetostrictive rod 8 as a bias magnetic field for its operation, ensuring that magnetostrictive rod 8 can maintain optimal magnetostrictive performance, thereby achieving performance optimization. Fixing base 12 is used to install and constrain magnetostrictive rod 8 to ensure that it can extend linearly in a controllable direction, i.e., to provide magnetostrictive rod 8 with a driving force or thrust pointing in a specific direction. Under the action of the magnetic field, magnetostrictive rod 8 produces deformation corresponding to the direction of the magnetic field, so that the length of magnetostrictive rod 8 changes with the control voltage signal of current source 10 based on the magnetostrictive strain caused by the preset magnetic field bias of permanent magnet 11. This allows for rapid control of the angle of grating 3 and the length of the grating outer cavity. After optical feedback from the outer cavity, the control voltage signal can be used to rapidly tune or modulate the output laser frequency. The current source 10 is a voltage-controlled current source.

[0040] In this embodiment, the permanent magnet 11 can provide stable and optimized bias magnetic field parameters for the magnetostrictive actuator 5, ensuring that the magnetostrictive rod 8 can work under the best magnetostrictive performance. This optimization measure significantly improves the actuation linearity and accuracy of the magnetostrictive rod 8, laying the foundation for achieving more precise grating position or angle control.

[0041] Furthermore, such as Figure 3 As shown, the magnetostrictive actuator 5 also includes a magnetic shielding cover 13 for shielding against magnetic field interference. The magnetic shielding cover 13 has an opening for the magnetostrictive rod 8 to extend. The magnetic shielding cover 13, made of magnetic shielding material, serves two purposes: firstly, it prevents external magnetic field changes from interfering with the deformation of the magnetostrictive rod 8; secondly, it isolates the internal magnetic field, ensuring compatibility with the electromagnetic environment. Since the strength of the magnetic field required for the mechanical deformation of the magnetostrictive rod 8 is determined by the magnitude of the current in the solenoid 9, a voltage-controlled current source 10 is needed to output a stable current to ensure the extension and retraction stability of the magnetostrictive rod 8.

[0042] In this embodiment, the magnetostrictive rod 8 is made of magnetostrictive material. The response time of the magnetostrictive material is the time required from the application of a magnetic field to the generation of the corresponding strain, which is on the order of microseconds. It has good frequency characteristics, and the response bandwidth of the magnetostrictive material can reach the order of megahertz. Based on the magnetostrictive characteristics of high response bandwidth, high-speed grating motion control can be realized, forming a fast closed loop. This fast closed-loop control mechanism can significantly reduce the impact of interference on laser performance. The magnetostrictive rod 8 generates a large thrust when subjected to magnetostrictive strain. A rod of magnetostrictive material with a diameter of about 10 mm generates a thrust of about 200 kg during magnetostriction, which helps to provide better driving capability and achieve faster and more precise control of the grating.

[0043] Specifically, such as Figure 2 As shown, in this embodiment, the grating holder 4 is a U-shaped structure integrally formed of elastic material. One side of the U-shaped structure is a support block fixedly mounted on the laser base, and the other side is an elastic block for mounting the grating 3. The fixed end of the magnetostrictive actuator 5 is fixedly connected to the support block, and the free end is connected to the elastic block. The magnetostrictive actuator 5 is used to drive the elastic block to rotate around the connection between the support block and the elastic block. The elastic block of the grating holder 4 rotates under the extension and retraction of a single magnetostrictive actuator 5 and recovers elastically due to the mechanical structure and material elasticity of the flexible support.

[0044] Furthermore, in this embodiment, as Figure 2 As shown, a return spring 6 is also provided between the support block and the elastic block. Since the magnetostrictive actuator 5 has a large driving capability, when used in conjunction with the return spring 6, the upper limit of the reciprocating motion of the grating outer cavity mechanism and the continuous tuning of the laser frequency is no longer limited by the elastic deformation recovery speed of the grating fixing frame 4, thereby improving the speed of the grating recovery motion and improving the response characteristics of the device.

[0045] like Figure 4 The diagram illustrates the application of a high-response bandwidth single-actuator grating external cavity control device provided in Embodiment 1 of the present invention in a laser. The laser body includes a laser diode 1, a collimating lens 2, and a grating 3. The laser emitted from the laser diode 1 is collimated by the collimating lens 2 and then incident on the grating 3. The diffracted light from the grating forms external cavity optical feedback, achieving narrow-linewidth continuously tunable laser output. The elastic block of the grating holder 4, driven by a magnetostrictive actuator 5, can rotate around the connection between the support block and the elastic block, thereby driving the grating to rotate and tuning the wavelength and frequency of the laser output. The magnetostrictive actuator 5 can rapidly change the position or angle of the grating 3, forming a fast-response laser linewidth narrowing system. This enables rapid frequency sweeping during open-loop laser operation and high-bandwidth closed-loop feedback during laser frequency stabilization.

[0046] Example 2

[0047] Embodiment 2 of the present invention provides an implementation example of high-response bandwidth dual-actuator grating external cavity control, which relates to... Figure 1 , 3 As shown in Figures 5 and 6. Figure 1 As shown, the grating needs to move back and forth around its axis near a suitable position; as Figure 3 As shown, the same magnetostrictive actuator 5 is used, similar to that in Embodiment 1; as Figure 5 As shown, the grating holder 4 is used to fix the grating 3. Unlike Embodiment 1, this embodiment utilizes two magnetostrictive actuators 5, which drive the grating holder 4 to rotate, thereby changing the length of the laser's grating outer cavity. Figure 5 As shown, unlike Embodiment 1, in this embodiment, the grating holder 4 is a linear structure. One end of it is connected to the laser base 28 via a rotating shaft 7, and a magnetostrictive actuator 5 is provided on each side of the other end. The fixed end of the magnetostrictive actuator 5 is fixedly connected to the laser base 28, and the free end is used to drive the grating holder 4 to rotate clockwise and counterclockwise, respectively.

[0048] Furthermore, the high-response-bandwidth grating external cavity dual actuator control device provided in this embodiment also includes two protrusions 29 located on both sides of the grating fixing frame 4 and on the laser base 28. The protrusions 29 are fixed on the laser base 28, and the fixed end of the magnetostrictive actuator 5 is disposed on the protrusions 29.

[0049] In this embodiment, the grating holder 4 reciprocates around the rotating shaft 7 under the coordinated operation of two magnetostrictive actuators 5. Through the cooperative work of the two magnetostrictive actuators 5 that generate driving forces in opposite directions, precise control of the position of the grating 3 can be achieved. At this time, the grating only has the mechanical degree of freedom of rotation. The control of the angle of the grating 3 and the cavity length of the corresponding grating outer cavity does not depend on the elastic deformation at the rotating shaft, but entirely on the cooperation of the thrust of the two magnetostrictive actuators 5. Thus, the upper limit of the continuous tuning speed of the laser frequency is no longer limited by the elastic deformation recovery frequency, and a faster grating driving speed can be obtained, achieving precise control of the grating rotation.

[0050] Furthermore, since the elongation and reset characteristics of magnetostrictive materials differ, similar to the phenomenon of hysteresis loops, this embodiment uses two magnetostrictive actuators 5 to complement each other, improving the linear relationship between the driving current of the magnetostrictive actuator 5 and the grating motion. When the first magnetostrictive actuator 5 elongates, it causes the grating to rotate clockwise, at which time the second magnetostrictive actuator is in a retracted state; when the second magnetostrictive actuator elongates, it causes the grating to rotate counterclockwise to reset, at which time the first magnetostrictive actuator is in a retracted state. By working in coordination through the relative relationship of the driving currents of the two magnetostrictive actuators 5, the stability of the grating oscillation process can be guaranteed, and the stability of the external cavity length control can be improved. Specifically, after obtaining the grating loop signal, one of the magnetostrictive actuators (5) is directly driven by the grating feedback loop signal, and the other magnetostrictive actuator (5) is driven by the signal after the grating feedback loop signal is inverted.

[0051] like Figure 6 The diagram shown illustrates the application of a high-response-bandwidth dual-actuator grating external cavity control device provided in Embodiment 2 of the present invention in a laser; similar to Embodiment 1 and... Figure 4 Similarly, the laser body includes a laser diode 1, a collimating lens 2, and a grating 3. The laser emitted by the laser diode 1 is collimated by the collimating lens 2 and then incident on the grating 3. The diffracted light from the grating forms external cavity optical feedback, achieving narrow-linewidth continuously tunable laser output. Unlike Embodiment 1, this embodiment uses two magnetostrictive actuators 5 to drive the linear grating holder 4 in reciprocating motion. Specifically, the performance parameters of each actuator can be finely adjusted to achieve their coordinated operation. This optimization ensures that the two magnetostrictive actuators can jointly generate a more precise, stable, and reciprocating thrust output. Simultaneously, the grating external cavity is no longer limited by the upper limit of the elastic deformation response of the grating holder 4 in the traditional scheme. Now, only rotational control is available, thus the upper limit of the continuous tuning speed of the laser frequency is no longer limited by the elastic deformation recovery speed. This improves the response bandwidth of the entire mechanism, thereby achieving precise control of the grating position or angle, and ultimately realizing high-bandwidth closed-loop locking of the laser output frequency relative to the reference frequency.

[0052] Example 3

[0053] Embodiment 3 of the present invention provides a high-response-bandwidth grating external cavity laser, comprising a laser body 14, which includes a laser diode 1, a collimating lens 2, a grating 3, and a laser base 28. The laser body 14 also includes the laser grating external cavity control device described in Embodiment 1 or Embodiment 2.

[0054] Furthermore, in this embodiment, the position and rotation axis of the grating 3 are determined based on the requirement of continuous tunability without mode skipping, taking into account the requirements of the output laser mode on the grating diffraction angle and external cavity length during frequency sweep.

[0055] Example 4

[0056] like Figure 7 As shown, Embodiment 4 of the present invention provides a frequency-stabilized laser system structure based on a grating external cavity control device with high response bandwidth. In addition to the laser body 14 described in Embodiment 3, it also includes a frequency reference device 15, a driving constant current source 17, a modulation signal generator 19, and a frequency discrimination signal processing device composed of a multiplier 20 and a low-pass filter 21. The obtained frequency discrimination signal is divided into two paths to form three main feedback loops.

[0057] Specifically, such as Figure 7 As shown, the driving constant current source 17 is used to input current to the laser diode 1 to drive it to emit light. The modulator generator 19 has two output terminals. The first output terminal is connected to the input terminal of the driving constant current source 17 and is used to output a modulation signal to modulate the output current of the driving constant current source 17. The second output terminal sends the modulation signal to the first input terminal of the multiplier 20 after appropriate phase shifting. The output laser of the laser diode is output after passing through the collimating lens 2 and the grating 3. The output laser is then output to the second input terminal of the multiplier 20 after passing through the frequency reference device 15. The frequency discrimination signal required for frequency stabilization is obtained by using the multiplier 20 and the low-pass filter 21. The frequency discrimination signal is divided into two paths.

[0058] Specifically, such as Figure 7 As shown, the frequency discrimination signal, after passing through the first filter 22, is sent to the first PID controller 23 to form a feedback electrical signal. This feedback signal is then split into two paths by the feedforward controller 24. The first path outputs to the current source 10 of the magnetostrictive actuator 5 to control the movement of the grating's outer cavity, forming the first closed-loop feedback loop, which is the grating feedback. The other path outputs to the adder 18 and controls the driving constant current source 17, thereby controlling the constant current source current of the laser and forming the injection current correction for the laser diode 1, forming the second closed-loop feedback loop, which is the current feedback. This achieves the function of jointly correcting frequency drift within the bandwidth of the frequency stabilization system through the grating and current, and improving the long-term stability of continuous operation without mode skipping. In this embodiment, since the magnetostrictive actuator 5 is used to control the grating angle, the feedforward controller 24 can directly process both the grating and current feedback signals, which is more effective than traditional PZT driving.

[0059] Furthermore, such as Figure 7As shown, the frequency discrimination signal, after passing through the second filter 25, is sent to the second PID controller 26 and the phase shifter 27. After passing through the phase shifter 27, a feedback electrical signal is output to the current input terminal of the laser diode 1, forming a third closed-loop feedback loop, which is a high-speed current feedback loop. In this embodiment, a laser frequency fast correction loop can be constructed through the phase shifter 27. This loop achieves high-speed adjustment of the laser frequency by directly controlling the injection current of the semiconductor laser diode. It can effectively compensate and correct the residual noise caused by the driving source noise of the constant current source 17 and the magnetostrictive actuator 5 in the first loop, thereby improving the final laser frequency or phase noise characteristics.

[0060] In summary, this embodiment utilizes frequency discrimination signals for two types of feedback: grating feedback and current feedback. These control the grating position in the external cavity feedback and the driving current of the laser diode, respectively. The current feedback involves intermediate frequency current feedback directly controlling the driving constant current source and high-speed current feedback directly controlling pin 1 of the laser diode. High-speed current feedback enables high-speed frequency drift correction, used to optimize frequency and phase noise. If the requirements for laser linewidth, frequency noise, and phase noise are not high, a high-speed current feedback loop can be omitted.

[0061] Furthermore, the high-response-bandwidth laser frequency stabilization system of this embodiment also includes an adder 18 and a sweep frequency signal generator 16. The first input terminal of the adder 18 is connected to the output terminal of the sweep frequency signal generator 16, and the second input terminal is connected to the output terminal of the feedforward controller 24. The output terminal of the adder 18 is connected to the input terminal of the driving constant current source 17.

[0062] Specifically, in this embodiment, the frequency reference device 15 can be a saturated absorption spectroscopy device or a highly stable FP cavity, which can provide a laser frequency reference based on atomic transition lines or resonant cavity frequencies for laser frequency stabilization.

[0063] Specifically, in this embodiment, when the laser grating external cavity control device in the laser body 14 adopts the structure of Embodiment 2, the grating feedback loop signal output by the feedforward controller 24 needs to be divided into two paths. One path directly controls one magnetostrictive actuator 5, and the other path, after passing through an inverter, forms a complementary control signal to control another magnetostrictive actuator 5. This accommodates the differences in the telescopic motion control of the two magnetostrictive actuators 5, enabling complementary and coordinated control of the counterclockwise and clockwise rotation of the grating, further improving the frequency response bandwidth of the laser.

[0064] Example 5

[0065] Embodiment 5 of the present invention provides a frequency stabilization method for a high-response-bandwidth laser as described in Embodiment 4, comprising the following steps:

[0066] Step 1: A low-frequency sweep signal is generated by the sweep signal generator 16, and the driving constant current source 17 of the laser body 14 is controlled to change the injection current of the laser diode 1, or the position and angle of the grating external cavity are changed by controlling the driving current source 10 in the magnetostrictive actuator 5, so as to realize continuous scanning and tuning of the laser frequency.

[0067] Step 2: Obtain the laser spectrum required for laser frequency stabilization using the frequency reference device 15. The frequency reference device 15 can be, for example, a saturated absorption spectroscopy device or a highly stable FP cavity. After the laser passes through the frequency reference device 15 to obtain the saturated absorption spectrum or the FP optical reference cavity, the transmission or reflection spectrum can be obtained, providing a laser frequency reference based on atomic transition lines or resonant cavity frequencies for laser frequency stabilization. The linewidth of the spectral resonance peak and the signal-to-noise ratio of the signal need to be optimized by adjusting the geometry of the optical path and optoelectronic parameters including detector response characteristics, light power, and polarization.

[0068] Step 3: Optimization of the frequency discrimination signal. Based on the obtained laser frequency reference spectrum, the modulation signal generator 19 outputs two signals. One signal is used to perform high-frequency modulation of the laser frequency by modulating the injection current, grating driver, or modulator on the external optical path of other lasers. The second signal is used as a reference signal input to the multiplier 20. The other input signal of the multiplier 20 comes from the frequency reference device 15 and is the laser frequency reference spectrum (saturated absorption spectrum or FP cavity spectrum) modulated by the high-frequency signal. The output of the multiplier 20 is filtered by the low-pass filter 21 to obtain the frequency discrimination signal. The signal-to-noise ratio of the frequency discrimination signal needs special attention. The response characteristics of the low-pass filter 21, which limits the bandwidth of the frequency discrimination signal, need to be balanced with the signal-to-noise ratio according to the bandwidth requirements.

[0069] Step 4: Preliminary Closed-Loop Optimization. Through parameter tuning of the first filter 22, the second filter 25, the first PID controller 23, the second PID controller 26, and the feedforward controller 24, including selecting filter frequency characteristics and optimizing the proportional, integral, and derivative parameters (PID) of the loop dynamic response characteristics, coordination between the grating and the intermediate frequency current closed-loop feedback loop is achieved. This is used to correct the laser's frequency drift relative to the target frequency and optimize long-term stability, realizing high-bandwidth closed-loop feedback laser frequency stabilization. The focus is on using closed-loop bandwidth and long-term stability as preliminary optimization criteria for closed-loop related parameters. The preliminary optimization process involves two closed loops: the first closed-loop feedback loop is a grating feedback loop, and the second closed-loop feedback loop is a current feedback loop, primarily responsible for laser frequency drift correction and long-term stability optimization.

[0070] Step 5: Closed-Loop Noise Optimization. Given that the grating feedback mechanism constructed by the magnetostrictive actuator 5 has a high response bandwidth, resulting in response bandwidths for both the current and grating feedback loops reaching the MHz level, both types of loops ultimately exhibit residual noise due to the influence of the driver source noise level. Since directly controlling the laser diode current has an even higher bandwidth, noise optimization of the frequency stabilization system can be achieved through a third feedback loop, using high-speed current feedback. Specifically, the frequency and phase noise performance of the frequency stabilization system can be improved by optimizing the parameters of the second filter 25 and the phase shifter 27.

[0071] One of the key features of this invention is the ability to easily implement parameter optimization based on noise characteristic characterization, which is a characteristic effect of the high-bandwidth magnetostrictive grating driving scheme.

[0072] In summary, this invention provides a high-response-bandwidth grating external cavity control device and laser system. Due to the high response bandwidth (megahertz) and large driving force of magnetostrictive materials, driving the grating with a magnetostrictive actuator improves the efficiency and response performance of grating control and laser frequency adjustment, enhances the grating feedback response characteristics of the laser, and achieves a response bandwidth in the MHz range. Furthermore, this invention stabilizes the laser frequency by constructing a high-bandwidth, fast-response closed-loop feedback control system, reducing the impact of interference on laser performance, enhancing the frequency drift suppression capability within the laser bandwidth, improving the suppression of higher-frequency laser fluctuations, enhancing the overall anti-interference capability of the laser system, and improving long-term stability and environmental adaptability. In conclusion, this invention, using magnetostrictive materials as the grating external cavity driving mechanism, is of great significance for high-response-speed control devices and low-noise, high-bandwidth frequency stabilization systems, improving the laser's linewidth and noise characteristics, and enhancing environmental adaptability and long-term stability.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-response-bandwidth frequency-stabilized laser system, comprising a laser body (14), the laser body (14) including a laser diode (1), a collimating lens (2), a grating (3), and a laser base (28), characterized in that, It also includes a frequency reference device (15), a driving constant current source (17), a modulation signal generator (19), a multiplier (20), and a low-pass filter (21). The laser body (14) also includes a grating external cavity control device, which includes a magnetostrictive actuator (5) and a current source (10). The magnetostrictive actuator (5) is used to drive the grating (3) of the laser to rotate, so as to change the grating angle and the length of the outer cavity of the laser grating; The magnetostrictive actuator (5) includes a magnetostrictive rod (8), a fixed base (12), a permanent magnet (11), and a solenoid (9). One end of the magnetostrictive rod (8) is fixed on the fixed base (12), and the other end serves as the free end of the magnetostrictive actuator (5). The solenoid (9) is sleeved on the outer periphery of the magnetostrictive rod (8) and is used to provide an axial magnetic field for the magnetostrictive rod (8) under the drive of the current source (10). The permanent magnet (11) is used to provide a bias magnetic field for the magnetostrictive rod (8). The constant current source (17) is used to input current into the laser diode (1) to drive it to emit light. The modulation signal generator (19) has two output terminals. The first output terminal is connected to the input terminal of the constant current source (17) and is used to output the modulation signal. The second output terminal shifts the modulation signal and sends it to the first input terminal of the multiplier (20). The output laser of the laser diode is output after passing through the collimating lens (2) and the grating (3). The output laser is output to the second input terminal of the multiplier (20) after passing through the frequency reference device (15). The frequency discrimination signal required for frequency stabilization is obtained by the multiplier (20) and the low-pass filter (21). The frequency discrimination signal is divided into two paths. The first path passes through the first PID controller (23) to form a feedback electrical signal. After passing through the feedforward controller (24), it is divided into two branches. The first branch is output to the current source (10) to form a grating feedback loop. The second branch is output to the driving constant current source (17) to form a current feedback loop. The second path outputs a feedback electrical signal to the laser diode (1) after passing through the second PID controller (26), forming a high-speed current feedback loop.

2. The high-response-bandwidth frequency-stabilized laser system according to claim 1, characterized in that, The grating external cavity control device also includes a grating fixing frame (4) for setting the grating (3). The grating fixing frame (4) is a U-shaped structure integrally formed of elastic material. One side of the U-shaped structure is a support block fixedly set on the laser base, and the other side is an elastic block for setting the grating (3). The fixed end of the magnetostrictive actuator (5) is fixedly connected to the support block, and the free end is connected to the elastic block. The magnetostrictive actuator (5) is used to drive the elastic block to rotate around the connection between the support block and the elastic block.

3. The high-response-bandwidth frequency-stabilized laser system according to claim 2, characterized in that, A rebound spring (6) is also provided between the support block and the elastic block.

4. The high-response-bandwidth frequency-stabilized laser system according to claim 1, characterized in that, The magnetostrictive actuator (5) further includes a fixed base (12) at one end of the fixed end of the magnetostrictive rod and a magnetic shield (13) for shielding magnetic field interference. The magnetic shield (13) is provided with an opening for the free end of the magnetostrictive rod (8) to extend out.

5. A high-response-bandwidth frequency-stabilized laser system according to claim 1, characterized in that, The grating external cavity control device also includes a grating fixture (4) for setting the grating (3). One end of the grating fixture (4) is connected to the laser base (28) via a rotating shaft (7), and a magnetostrictive actuator (5) is provided on both sides of the other end. The fixed end of the magnetostrictive actuator (5) is connected to the laser base (28), and the free end is used to drive the grating fixture (4) to rotate clockwise and counterclockwise, respectively.

6. A high-response-bandwidth frequency-stabilized laser system according to claim 5, characterized in that, The grating external cavity control device also includes two bosses (29) located on both sides of the grating fixture (4). The bosses (29) are fixedly mounted on the laser base (28), and the fixed end of the magnetostrictive actuator (5) is fixedly mounted on the bosses (29).

7. A high-response-bandwidth frequency-stabilized laser system according to claim 5, characterized in that, One of the magnetostrictive actuators (5) is directly driven by the grating feedback loop signal, and the other magnetostrictive actuator (5) is driven by the signal after the grating feedback loop signal is inverted.

8. A high-response-bandwidth frequency-stabilized laser system according to claim 1, characterized in that, It also includes a first filter (22), a second filter (25), a phase shifter (27), an adder (18), and a sweep frequency signal generator (16); The first filter (22) is set at the input of the first PID controller (23), the second filter (25) is set at the input of the second PID controller (26), and the phase shifter (27) is set at the output of the second PID controller (26). The first input terminal of the adder (18) is connected to the output terminal of the sweep frequency signal generator (16), and the second input terminal is connected to the output terminal of the feedforward controller (24); the output terminal of the adder (18) is connected to the input terminal of the driving constant current source (17).

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