Grating external cavity control device with high response bandwidth and frequency stabilized laser system

Abstract

The invention belongs to the technical field of laser, and discloses a grating external cavity control device with high response bandwidth and a frequency stabilized laser system. The grating external cavity control device comprises a grating fixing frame, a magnetostrictive actuator and a driving current source of the magnetostrictive actuator; the grating fixing frame is used for arranging a grating, and the magnetostrictive actuator is used for driving the grating fixing frame to rotate so as to change the grating angle and the outer cavity length of a laser grating outer cavity; the magnetostrictive actuator comprises a magnetostrictive rod, a fixing seat, a permanent magnet and a solenoid, one end of the magnetostrictive rod is fixed to the fixing seat, the other end of the magnetostrictive rod serves as the free end of the magnetostrictive actuator, and the solenoid is arranged on the periphery of the magnetostrictive rod in a sleeving mode and used for providing an axial magnetic field for the magnetostrictive rod under driving of a current source. The permanent magnet is used for providing a bias magnetic field for the magnetostrictive rod. The frequency stabilized laser system relates to a specific structure of three feedback loops of a grating and a current, and frequency stabilized closed loops respectively aiming at a single-actuator grating external cavity control device and a double-actuator grating external cavity control device. The response bandwidth of the laser is improved, the line width and noise characteristics of the laser can be greatly improved, and the environmental adaptability and long-term stability are improved.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a high-response bandwidth grating external cavity control device for narrow linewidth lasers and a corresponding frequency-stabilized laser system. Background Art

[0002] Semiconductor lasers are important devices widely used in scientific research, industry and medical fields. Their performance is crucial to the application effects in various fields. Among them, grating external cavity feedback lasers (ECDL, External Cavity DiodeLaser) can achieve line width narrowing and continuous frequency tunability of laser diode output lasers, and are classic solutions for high-end applications of semiconductor lasers. The frequency of the laser can be changed by controlling the injection current of the laser diode or the grating position of the grating feedback external cavity of the ECDL (the change of position can bring about the change of cavity length and grating feedback angle), and can be used for open-loop tuning or closed-loop correction of the laser frequency. The output frequency and output power of the laser change synchronously due to the current adjustment. At the same time, the electrical and physical properties of the semiconductor laser diode, the threshold current, slope efficiency, thermal effect and nonlinear effect of the laser determine that the adjustment range of the semiconductor laser injection current is limited. In the end, a large range of current adjustment may also cause a sharp drop in the performance of the laser, or even damage the laser. On the other hand, grating control usually involves the adjustment of the optical path and mechanical structure. The physical characteristics and precision of these mechanical structures limit the adjustment range of grating control. Due to the need for mode competition, the feedback intensity of the ECDL grating external cavity cannot change too much during continuous mode-hopping tuning, resulting in a limited travel of the final grating mechanical structure. More importantly, the response speed of the grating optomechanical system and the drive mechanism is directly related to the response bandwidth of the laser frequency modulation through the grating. The adjustment range or limitation of the frequency continuous tuning or current and grating here is based on the requirement for the frequency non-mode-hopping continuous tunable characteristics. The technical solution usually chooses the feedforward method to synchronously adjust the grating and current to increase the non-mode-hopping continuous tunable range.

[0003] The currently commonly used ECDL laser grating external cavity control scheme is based on the PZT (piezoelectric ceramic actuator) control mechanism of the piezoelectric effect. By adjusting the driving voltage on the PZT to change the length of the actuator, the angle or position of the grating is changed to achieve low-speed control of the laser frequency. On the one hand, this is because the response bandwidth of the piezoelectric ceramic material is not enough, usually in the kHz range, and the driving force is in the hundreds of Newtons; on the other hand, the traditional PZT grating drive mechanism is also limited by the elastic recovery speed of the mechanical structure under elastic deformation when driving the grating. The PZT-based grating drive mechanism has a limited response bandwidth, a limited frequency sweep speed, and a limited bandwidth of the formed frequency stabilization closed loop. High-speed frequency control or tuning needs to be achieved by changing the injected current. However, due to the different response bandwidths, response speeds and adjustment ranges of current and grating control, the dynamic range of the cooperative tuning system is limited in the open loop, and the feedback loop correction capability is limited and the closed-loop bandwidth is small during 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 of various factors, which restricts the stability of the laser and its frequency stabilization system during long-term operation.

[0004] In summary, since the PZT driven grating feedback loop has a limited bandwidth when acting alone, even if the feedforward method is used, the continuous tunable range can be improved, but the working bandwidth is limited, causing the laser output frequency and output noise characteristics to be sensitive to the environment, making the environmental adaptability and long-term continuous operation stability of the semiconductor laser and its frequency stabilization system still limited. Therefore, it is necessary to invent a new laser grating external cavity control device and frequency stabilization method to solve the defects of the existing methods in response bandwidth. Summary of the invention

[0005] In order to solve the technical problem in the prior art that the mechanical movement speed and time delay of the grating external cavity of the semiconductor laser are slow, resulting in a large frequency stabilization response bandwidth being limited, the present invention proposes a grating external cavity control device and a laser system with a high response bandwidth, which utilizes a magnetostrictive actuator to drive the grating, thereby realizing rapid control of the grating position and angle in the laser, and realizing rapid tuning of the laser output frequency by the grating external cavity and a high-bandwidth frequency stabilization closed loop.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a grating external cavity control device with high response bandwidth, 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 the external cavity length of the grating external cavity of the laser; The magnetostrictive actuator comprises a magnetostrictive rod, a fixing seat, a permanent magnet and a solenoid. One end of the magnetostrictive rod is fixed on the fixing seat, and the other end serves as the free end of the magnetostrictive actuator. The solenoid is sleeved on the outer circumference of the magnetostrictive rod and is used to provide an axial magnetic field for the magnetostrictive rod under the drive of a current source. The permanent magnet is used to provide a bias magnetic field for the magnetostrictive rod.

[0007] The high response bandwidth grating external cavity single actuator control device further comprises a grating fixing frame for setting the grating, the grating fixing frame 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; the fixed end of the magnetostrictive actuator is fixedly connected to the support block, and the free end is connected to the elastic block, and the magnetostrictive actuator is used to drive the elastic block to rotate around the connection between the support block and the elastic block; A rebound spring is also arranged between the support block and the elastic block.

[0008] The magnetostrictive actuator also includes a fixing seat at one end of the magnetostrictive rod fixed end and a magnetic shielding cover for shielding magnetic field interference. The magnetic shielding cover is provided with an opening for extending the movable end of the magnetostrictive rod.

[0009] The high response bandwidth grating external cavity single actuator control device also includes a grating fixing frame for setting the grating, one end of the grating fixing frame is connected to the laser base through a rotating shaft, and a magnetostrictive actuator is respectively arranged 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 fixing frame to rotate clockwise and counterclockwise respectively.

[0010] The high response bandwidth grating external cavity dual actuator control device also includes two bosses respectively located on both sides of the grating fixing frame, the bosses are fixedly arranged on the laser base, and the fixed end of the magnetostrictive actuator is fixedly arranged on the bosses.

[0011] In the high response bandwidth grating external cavity dual actuator control device, one magnetostrictive actuator is directly driven by the grating feedback loop signal, and the other magnetostrictive actuator is driven by the grating feedback loop signal after passing through an inverter.

[0012] In addition, the present invention also provides a high response bandwidth stabilized frequency laser system, including a laser body, wherein the laser body includes a laser diode, a collimating lens, a grating and a laser base, and is characterized in that the laser body also includes the laser grating external cavity control device described in any one of claims 1 to 3.

[0013] The high response bandwidth frequency-stabilized laser system also includes a frequency reference device, a driving constant current source, a modulation signal generator, a multiplier, and a low-pass filter; The driving constant current source is used to input current to 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 driving constant current source and is used to output a modulation signal. The second output terminal sends the modulation signal to the first input terminal of the multiplier after phase shifting. The output laser of the laser diode is output after passing through a collimating lens and a grating. The output laser is output to the second input terminal of the multiplier after passing through a frequency reference device, and the discrimination signal required for frequency stabilization is obtained through the multiplier and a low-pass filter. The frequency discrimination signal is divided into two paths. The first path passes through the first PID controller to form a feedback electrical signal, and then passes through the feedforward controller to form two branches. 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 reverse feedback loop. The second path outputs a feedback electrical signal to the laser diode after passing through the second PID controller, forming a high-speed current feedback loop.

[0014] The high response bandwidth frequency-stabilized laser system further includes a first filter, a second filter, a phase shifter, an adder, and a frequency sweep signal generator; The first filter is arranged at the input end of the first PID controller, the second filter is arranged at the input end of the second PID controller, and the phase shifter is arranged at the output end of the second PID; The first input end of the adder is connected to the output end of the sweep signal generator, and the second input end is connected to the output end of the feedforward controller; the output end of the adder is connected to the input end of the driving constant current source.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention proposes a grating external cavity control device and a laser system with a high response bandwidth. The grating external cavity is driven by a magnetostrictive actuator. Due to the advantages of the magnetostrictive material's high response bandwidth of up to MHz and greater driving force, the efficiency and response performance of the grating adjustment are improved, the grating feedback response characteristics of the laser are improved, and the response bandwidth can reach the MHz level.

[0016] 2. The present invention also stabilizes the frequency of the laser by constructing a high-bandwidth, fast-response closed-loop feedback control system, thereby enhancing the ability to suppress frequency noise and frequency drift within the laser bandwidth, suppressing laser frequency fluctuations in a larger range and at a higher frequency, reducing the impact of environmental interference on laser performance, enhancing the anti-interference ability of the overall laser system, and improving long-term stability and environmental adaptability.

[0017] In summary, the present invention uses magnetostrictive materials and magnetostrictive actuator devices as grating external cavity driving mechanisms, which is of great significance to high-response speed control devices and low-noise, high-bandwidth frequency stabilization systems, and can greatly improve the line width and noise characteristics of the laser, and enhance environmental adaptability and long-term stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of an application example of a high response bandwidth grating external cavity control device provided in the first embodiment of the present invention; Figure 2 A schematic structural diagram of a single-actuator grating external cavity control device with high response bandwidth provided in Embodiment 1 of the present invention; Figure 3 It is a schematic structural diagram of a magnetostrictive actuator provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the application of a single-actuator grating external cavity control device with high response bandwidth provided in the first embodiment of the present invention in a laser; Figure 5 This is a schematic structural diagram of a dual-actuator grating external cavity control device with high response bandwidth provided in the second embodiment of the present invention; Figure 6 A schematic diagram of the application of a high response bandwidth dual-actuator grating external cavity control device provided in the second embodiment of the present invention in a laser; Figure 7 This is a schematic structural diagram of a frequency-stabilized laser system with a high response bandwidth provided in the fourth embodiment of the present invention; In the figure: 1-laser diode, 2-collimating lens, 3-grating, 4-grating fixing frame, 5-magnetostrictive actuator, 6-rebound spring, 7-rotating shaft, 8-magnetostrictive rod, 9-solenoid, 10-current source, 11-permanent magnet, 12-fixed seat, 13-magnetic shielding cover, 14-laser body, 15-frequency reference device, 16-sweep frequency signal generator, 17-driving 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 DESCRIPTION

[0019] In order to make the purpose, 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 part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] Embodiment 1 Embodiment 1 of the present invention provides a high response bandwidth single actuator grating external cavity control implementation example, involving Figure 1 , 2 , 3 and 4. Figure 1 As shown, the grating needs to move back and forth around the axis near the appropriate position; Figure 2 As shown, the laser grating external cavity single actuator control device comprises: a grating 3, a grating fixing frame 4, a magnetostrictive actuator 5 and a rebound spring 6. The grating fixing frame 4 is used to fix the grating 3, and the magnetostrictive actuator 5 is used to drive the grating fixing frame 4 to move, so as to change the grating angle and the external cavity length of the laser grating external cavity.

[0021] Specifically, the grating fixing frame 4 is used as a moving component 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 fixing frame 4 to ensure precise matching and functional linkage between the two. The magnetostrictive actuator 5, on the one hand, achieves precise control of the grating movement based on the magnetostrictive characteristics of high stress and strong thrust, and on the other hand, achieves high-speed control of the grating movement based on the magnetostrictive characteristics of high response bandwidth. The rebound spring 6, on the one hand, is used to provide prestress for the magnetostrictive actuator to optimize its working state, and on the other hand, assists the elastic rebound of the grating fixing frame 4 to improve the system movement response speed.

[0022] like Figure 3 As shown, in this embodiment, the magnetostrictive actuator 5 includes a magnetostrictive rod 8, a fixing seat 12, a permanent magnet 11 and a solenoid 9. One end of the magnetostrictive rod 8 is fixed on the fixing seat 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 magnetostrictive rod 8 with a bias magnetic field required for the optimal telescopic characteristic working point.

[0023] Specifically, in this embodiment, the permanent magnet 11 is evenly arranged on the periphery of the solenoid 9, and is used to provide a uniform magnetic field to the position of the magnetostrictive rod 8 as a bias magnetic field for its operation, ensuring that the magnetostrictive rod 8 can maintain the best magnetostrictive efficiency state, thereby optimizing its performance. The fixing seat 12 is used to install and constrain the magnetostrictive rod 8 to ensure that it can be controllably extended linearly along a preset direction, that is, to give the magnetostrictive rod 8 a driving force or thrust pointing to a specific direction; under the action of the magnetic field, the magnetostrictive rod 8 produces a deformation corresponding to the direction of the magnetic field, so that the length of the magnetostrictive rod 8 changes with the control voltage signal of the current source 10 on the basis of the magnetostrictive strain caused by the preset magnetic field bias of the permanent magnet 11, thereby quickly controlling the angle of the grating 3 and the length of the grating external cavity, and after optical feedback from the external cavity, the control voltage signal can be used to quickly tune or modulate the output laser frequency. Among them, the current source 10 is a voltage-controlled current source.

[0024] 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 operate under the optimal magnetostrictive performance state. 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.

[0025] Furthermore, if Figure 3 As shown, the magnetostrictive actuator 5 also includes a magnetic shielding cover 13 for shielding magnetic field interference, and the magnetic shielding cover 13 is provided with an opening for extending the magnetostrictive rod 8. The magnetic shielding cover 13 made of magnetic shielding material, on the one hand, avoids the interference of external magnetic field changes on the deformation of the magnetostrictive rod 8, and on the other hand, isolates the internal magnetic field to ensure the compatibility of 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, the voltage-controlled current source 10 is required to output a stable current to ensure the telescopic stability of the magnetostrictive rod 8.

[0026] In this embodiment, the magnetostrictive rod 8 is a magnetostrictive material. The response time of the magnetostrictive material is the time required from applying a magnetic field to generating a corresponding strain, which is in the microsecond level. The frequency characteristic is good, and the response bandwidth of the magnetostrictive material can reach the megahertz level. Based on the magnetostrictive characteristics of the high response bandwidth, high-speed grating motion control can be achieved to form a fast closed loop. This fast closed-loop control mechanism can significantly reduce the impact of interference on the performance of the laser. The magnetostrictive rod 8 generates a large thrust when magnetostrictive strain occurs. A rod of magnetostrictive material with a diameter of about 10 mm generates a thrust of about 200 kg when magnetostricted, which helps to provide better driving capability and achieve faster and more precise control of the grating.

[0027] Specifically, Figure 2As shown, in this embodiment, 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, and the magnetostrictive actuator 5 is used to drive the elastic block to rotate around the connection between the support block and the elastic block; wherein, the elastic block of the grating fixing frame 4 rotates under the telescopic driving action of the single magnetostrictive actuator 5, and relies on the mechanical structure of the flexible bracket and the elastic recovery of the material.

[0028] Furthermore, in this embodiment, if Figure 2 As shown, a rebound spring 6 is also provided between the support block and the elastic block. Since the magnetostrictive actuator 5 has a large driving capacity, when used in conjunction with the rebound spring 6, the upper limit of the speed of the reciprocating motion of the grating external 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 increasing the speed of the grating recovery motion and improving the response characteristics of the device.

[0029] like Figure 4 As shown, it is a schematic diagram of the application of a single actuator grating external cavity control device with high response bandwidth in a laser provided by the first embodiment of the present invention. 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 grating diffraction light forms an external cavity optical feedback to achieve a narrow line width continuously tunable laser output. The elastic block of the grating fixing frame 4 can rotate around the connection between the support block and the elastic block under the drive of the magnetostrictive actuator 5, thereby driving the grating to rotate, and then tuning the wavelength and frequency of the laser output laser. The magnetostrictive actuator 5 can quickly change the position or angle of the grating 3, forming a fast response laser line width narrowing system, realizing fast frequency sweeping when the laser is in open loop operation, and realizing high bandwidth closed loop feedback when the laser frequency stabilization system is in operation.

[0030] Embodiment 2 Embodiment 2 of the present invention provides a high response bandwidth dual actuator grating external cavity control implementation example, involving Figure 1 , 3 , 5 and 6. Figure 1 As shown, the grating needs to move back and forth around the axis near the appropriate position; Figure 3 As shown, the same magnetostrictive actuator 5 as in the first embodiment is used; Figure 5 As shown, the grating fixing frame 4 is used to fix the grating 3. Different from the first embodiment, in this embodiment, two magnetostrictive actuators 5 are used to drive the grating fixing frame 4 to rotate so as to change the length of the grating outer cavity of the laser. Figure 5 As shown, different from the first embodiment, in this embodiment, the grating fixing frame 4 is a linear structure, one end of which is connected to the laser base 28 through the rotating shaft 7, and a magnetostrictive actuator 5 is respectively arranged on both sides of the other end, and 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 fixing frame 4 to rotate clockwise and counterclockwise respectively.

[0031] Furthermore, the present embodiment provides a high response bandwidth grating external cavity dual actuator control device, which also includes two bosses 29 located on both sides of the grating fixing frame 4 and on the laser base 28, wherein the bosses 29 are fixed on the laser base 28, and the fixed end of the magnetostrictive actuator 5 is arranged on the bosses 29.

[0032] In this embodiment, the grating fixing frame 4 realizes reciprocating drive around the rotating shaft 7 under the coordination of two magnetostrictive actuators 5. Through the coordinated work of two magnetostrictive actuators 5 that generate driving forces in opposite directions, the position of the grating 3 can be precisely controlled. At this time, the grating has only the mechanical freedom of rotation. The control of the angle of the grating 3 and the cavity length of the corresponding grating outer cavity does not need to rely on the elastic deformation at the rotating shaft, but completely relies on the thrust coordination of the two magnetostrictive actuators 5, so that the upper limit of the speed of continuous tuning of the laser frequency is no longer limited by the elastic deformation recovery frequency, and a faster grating driving speed can be obtained, and the precise control of the grating rotation is fully realized.

[0033] Furthermore, since the elongation and reset characteristics of magnetostrictive materials are different, similar to the phenomenon of hysteresis loop, the present embodiment can complement each other through two magnetostrictive actuators 5 to improve the linear relationship between the driving current of the magnetostrictive actuator 5 and the grating movement. When the first of the two magnetostrictive actuators 5 is extended, the grating rotates clockwise, and the second magnetostrictive actuator is in a retracted state; when the second magnetostrictive actuator is extended, the grating rotates counterclockwise and resets, and the first magnetostrictive actuator is in a retracted state. The relative relationship of the driving currents of the two magnetostrictive actuators 5 can work together to ensure the stability of the grating during the swing process and improve the stability of the external cavity length control. Specifically, after the grating loop signal is obtained, 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 of the grating feedback loop signal after the inverter.

[0034] like Figure 6 FIG. 1 is a schematic diagram of an application of a high response bandwidth dual-actuator grating external cavity control device provided in Embodiment 2 of the present invention in a laser; Figure 4Similar to the example shown in the figure, 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 grating diffraction light forms an external cavity optical feedback to achieve a narrow line width continuously tunable laser output. Different from the first embodiment, the present embodiment drives the linear structure grating fixing frame 4 to reciprocate by two magnetostrictive actuators 5. Specifically, the performance parameters of each actuator can be finely adjusted to achieve the coordinated work between them. This optimization ensures that the two magnetostrictive actuators can jointly produce a more accurate, stable and reciprocating thrust output, and at the same time, the grating external cavity is no longer limited by the upper limit of the elastic deformation response of the grating fixing frame 4 in the traditional solution. At this time, there is only rotation control, so that the upper limit of the speed of continuous tuning of the laser frequency is no longer limited by the elastic deformation recovery speed, which can improve the response bandwidth of the entire mechanism, thereby achieving precise control of the grating position or angle, and finally achieving high-bandwidth closed-loop locking of the laser output frequency relative to the reference frequency.

[0035] Embodiment 3 Embodiment 3 of the present invention provides a grating external cavity laser with high response bandwidth, including a laser body 14, wherein the laser body includes a laser diode 1, a collimating lens 2 and 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.

[0036] In addition, in this embodiment, the position and rotation axis of the grating 3 are determined based on the requirement of continuous tunability without mode hopping, taking into account the requirements of the output laser mode on the grating diffraction angle and the external cavity length during frequency scanning.

[0037] Embodiment 4 like Figure 7 As shown, the fourth embodiment of the present invention provides a frequency-stabilized laser system structure based on a grating external cavity control device with a high response bandwidth, which includes, in addition to the laser body 14 described in the third embodiment, 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.

[0038] Specifically, Figure 7As shown, the driving constant current source 17 is used to input current to the laser diode 1 to drive it to emit light, and the modulator generator 19 has two output ends. The first output end is connected to the input end 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 end sends the modulation signal to the first input end of the multiplier 20 after a reasonable phase shift. The output laser of the laser diode is output after passing through the collimating lens 2 and the grating 3, and the output laser is output to the second input end of the multiplier 20 after passing through the frequency reference device 15. The multiplier 20 and the low-pass filter 21 are used to obtain the discrimination signal required for frequency stabilization. The discrimination signal is divided into two paths.

[0039] Specifically, Figure 7 As shown, the first path of the frequency discrimination signal is sent to the first PID controller 23 after passing through the first filter 22 to form a feedback electrical signal, and the feedback electrical signal is divided into two paths after passing through 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 external cavity, forming the first closed-loop feedback loop as grating feedback; the other path is output to the adder 18 and controls the driving constant current source 17 to realize the control of the laser constant current source current, forming the injection current correction of the laser diode 1, and forming the second closed-loop feedback loop as current feedback. Thus, the frequency drift within the bandwidth of the frequency stabilization system is corrected by the grating and the current, and the long-term stability of continuous operation without mode hopping is improved. In the embodiment, since the magnetostrictive actuator 5 is used to control the grating angle, the feedforward controller 24 can be used to directly process the two feedback signals of the grating and the current, which is more effective than the traditional PZT drive.

[0040] Furthermore, if Figure 7 As shown, the second path of the frequency discrimination signal passes through the second filter 25 and 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 end of the laser diode 1, forming a third closed-loop feedback loop as a high-speed current feedback loop. In this embodiment, a laser frequency fast correction loop can be constructed by the phase shifter 27, which realizes high-speed adjustment of the laser frequency by directly controlling the injection current of the semiconductor laser diode, and can effectively compensate and correct the residual noise caused by the constant current source 17 and the magnetostrictive actuator 5 driving source noise of the first loop, thereby improving the final laser frequency or phase noise characteristics.

[0041] In summary, in this embodiment, the frequency discrimination signal is used to perform two types of feedback, grating and current, to control the grating position of the grating external cavity feedback and the driving current of the laser diode respectively. The current feedback involves directly controlling the intermediate frequency current feedback of the driving constant current source and directly controlling the high-speed current feedback of the laser diode 1 pin. The high-speed current feedback can realize high-speed frequency drift correction, which is used to optimize the frequency noise and phase noise. If the line width, frequency noise and phase noise of the laser are not required to be high, the high-speed current feedback loop can be omitted.

[0042] Furthermore, a high response bandwidth laser frequency stabilization system of this embodiment also includes an adder 18 and a swept frequency signal generator 16, wherein the first input end of the adder 18 is connected to the output end of the swept frequency signal generator 16, and the second input end is connected to the output end of the feedforward controller 24; the output end of the adder 18 is connected to the input end of the driving constant current source 17.

[0043] Specifically, in this embodiment, the frequency reference device 15 may be a saturated absorption spectrum device or a high-stability FP cavity, which can provide a laser frequency reference based on an atomic transition line or a resonant cavity resonance frequency for laser frequency stabilization.

[0044] Specifically, in this embodiment, when the laser grating external cavity control device in the laser body 14 adopts the structure of the second embodiment, 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 forms a complementary control signal after passing through an inverter to control another magnetostrictive actuator 5. In this way, the difference between the two magnetostrictive actuators 5 in telescopic motion control is compatible, and the counterclockwise and clockwise rotations of the grating are complementarily and cooperatively controlled, further improving the frequency response bandwidth of the laser.

[0045] Embodiment 5 Embodiment 5 of the present invention provides a frequency stabilization method for a laser with a high response bandwidth as described in Embodiment 4, comprising the following steps: Step 1: Generate a low-frequency sweep signal through the sweep signal generator 16, control the driving constant current source 17 of the laser body 14 to change the injection current of the laser diode 1, or change the position and angle of the grating external cavity by controlling the driving current source 10 in the magnetostrictive actuator 5, so as to realize continuous scanning and tuning of the laser frequency; Step 2: Obtain the laser spectrum required for laser frequency stabilization through the frequency reference device 15. The frequency reference device 15 may be, for example, a saturated absorption spectrum device or a high-stability FP cavity. After the laser passes through the frequency reference device 15 to obtain a saturated absorption spectrum or an FP optical reference cavity, a transmission or reflection spectrum may be obtained to provide a laser frequency reference based on the atomic transition line or the resonance frequency of the resonant cavity for laser frequency stabilization. The line width of the spectral resonance peak and the signal-to-noise ratio of the signal need to be optimized by adjusting the geometric structure of the optical path and optoelectronic parameters including the detector response characteristics, the power of the light, and polarization.

[0046] Step 3: Optimization of the demodulation signal. On the basis of obtaining the laser frequency reference spectrum, the modulation signal generator 19 outputs two signals, one of which is used to modulate the laser frequency at high frequency by modulating the injection current, the grating driver or driving the modulator on the external optical path of other lasers, and the second is input into the multiplier 20 as a reference signal; the other input signal of the multiplier 20 comes from the frequency reference device 15, which is the laser frequency reference spectrum modulated by the high-frequency signal (saturated absorption spectrum or FP cavity spectrum); the output of the multiplier 20 passes through the low-pass filter 21 to obtain the demodulation signal. The signal-to-noise ratio of the demodulation signal needs special attention, and the response characteristics of the low-pass filter 21 that restricts the bandwidth of the demodulation signal need to be weighed against the signal-to-noise ratio according to the bandwidth requirements.

[0047] Step 4: Preliminary closed-loop optimization. By debugging the parameters 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 the filter frequency characteristics and the proportional, integral, and differential parameters (PID) to optimize the loop dynamic response characteristics, the coordination of the grating and intermediate frequency current closed-loop feedback loop is achieved, which is used to correct the frequency drift and long-term stability optimization of the laser relative to the frequency stabilization target reference frequency, and realize the laser frequency stabilization of high-bandwidth closed-loop feedback, focusing on the closed-loop bandwidth and long-term stability as the preliminary optimization criteria for the closed-loop related parameters. Two closed loops are involved in the preliminary optimization process, specifically, the first closed-loop feedback loop is the grating feedback and the second closed-loop feedback loop is the current feedback, which mainly undertakes the laser frequency drift correction and long-term stability optimization functions.

[0048] Step 5: Closed-loop noise optimization. In view of the high response bandwidth of the grating feedback mechanism constructed by the magnetostrictive actuator 5, the response bandwidth of the current and grating feedback loops can reach the MHz level. Since both types of loops are ultimately limited by the influence of the driving source noise level, there is residual noise. Since the current of the laser diode directly controlled has a higher bandwidth, the noise of the frequency stabilization system can be optimized through the third feedback loop, high-speed current feedback. In the specific implementation, the frequency noise and phase noise indicators of the frequency stabilization system can be improved by optimizing the parameters of the second filter 25 and the phase shifter 27.

[0049] Among them, the ability to conveniently implement parameter optimization based on noise characteristic characterization is a characteristic effect of the high-bandwidth magnetostrictive grating driving scheme introduced in the present invention.

[0050] In summary, the present invention provides a grating external cavity control device and a laser system with a high response bandwidth. Due to the high response bandwidth of the magnetostrictive material and the large driving force, the grating is driven by a magnetostrictive actuator, which improves the efficiency and response performance of the grating control and adjustment of the laser frequency, improves the grating feedback response characteristics of the laser, and the response bandwidth can reach the MHz level. In addition, the present invention also stabilizes the laser frequency by constructing a high-bandwidth fast-response closed-loop feedback control system, reduces the impact of interference on the laser performance, enhances the frequency drift suppression capability within the laser bandwidth, improves the suppression of higher-frequency laser frequency fluctuations, enhances the anti-interference capability of the laser overall system, and improves long-term stability and environmental adaptability. In short, the present invention uses magnetostrictive materials as a grating external cavity driving mechanism, which is of great significance to high-response speed control devices and low-noise, high-bandwidth frequency stabilization systems, can improve the line width and noise characteristics of the laser, and improve environmental adaptability and long-term stability.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 grating external cavity control device with high response bandwidth, characterized in that: include: 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 external cavity of the grating external cavity of the laser; The magnetostrictive actuator (5) comprises a magnetostrictive rod (8), a fixing seat (12), a permanent magnet (11) and a solenoid (9); one end of the magnetostrictive rod (8) is fixed to the fixing seat (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 a current source (10); and the permanent magnet (11) is used to provide a bias magnetic field for the magnetostrictive rod (8).

2. The high response bandwidth grating external cavity control device according to claim 1, characterized in that: It 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, and 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 grating external cavity control device 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 grating external cavity control device according to claim 1, characterized in that: The magnetostrictive actuator (5) further comprises a fixing seat (12) at a single end of the magnetostrictive rod fixed end and a magnetic shielding cover (13) for shielding magnetic field interference, wherein the magnetic shielding cover (13) is provided with an opening for allowing the movable end of the magnetostrictive rod (8) to extend out.

5. The high response bandwidth grating external cavity control device according to claim 1, characterized in that: It also includes a grating fixing frame (4) for setting the grating (3), one end of the grating fixing frame (4) is connected to the laser base (28) via a rotating shaft (7), and a magnetostrictive actuator (5) is respectively arranged 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 respectively used to drive the grating fixing frame (4) to rotate clockwise and counterclockwise.

6. The high response bandwidth grating external cavity control device according to claim 5, characterized in that: It also includes two bosses (29) respectively located on both sides of the grating fixing frame (4), the bosses (29) being fixedly arranged on the laser base (28), and the fixed end of the magnetostrictive actuator (5) being fixedly arranged on the bosses (29).

7. The high response bandwidth grating external cavity control device according to claim 5, characterized in that: One of the magnetostrictive actuators (5) is directly driven by a grating feedback loop signal, and the other magnetostrictive actuator (5) is driven by a signal of the grating feedback loop signal after passing through an inverter.

8. A frequency-stabilized laser system with a high response bandwidth, comprising a laser body (14), wherein the laser body (14) comprises a laser diode (1), a collimating lens (2), a grating (3) and a laser base (28), characterized in that: The laser body (14) further comprises the grating external cavity control device according to any one of claims 1 to 7.

9. A frequency-stabilized laser system with high response bandwidth according to claim 8, 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 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 ends, the first output end is connected to the input end of the driving constant current source (17) and is used to output a modulation signal, and the second output end sends the modulation signal to the first input end of the multiplier (20) after 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 output to the second input end of the multiplier (20) after passing through the frequency reference device (15), and the discrimination signal required for frequency stabilization is obtained through the multiplier (20) and the low-pass filter (21). The frequency discrimination signal is divided into two paths, the first path passes through a first PID controller (23) to form a feedback electrical signal, and then passes through a feedforward controller (24) to form two branches, wherein the first branch is output to a current source (10) to form a grating feedback loop; and the second branch is output to a 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), thereby forming a high-speed current feedback loop.

10. A frequency-stabilized laser system with high response bandwidth according to claim 9, characterized in that: It also includes a first filter (22), a second filter (25), a phase shifter (27), an adder (18), and a swept frequency signal generator (16); The first filter (22) is arranged at the input end of the first PID controller (23), the second filter (25) is arranged at the input end of the second PID controller (26), and the phase shifter (27) is arranged at the output end of the second PID (26); The first input end of the adder (18) is connected to the output end of the sweep signal generator (16), and the second input end is connected to the output end of the feedforward controller (24); the output end of the adder (18) is connected to the input end of the driving constant current source (17).

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