Narrow linewidth laser frequency control device and method based on optical feedback discretization

Abstract

The invention discloses a narrow linewidth laser frequency control device and method based on optical feedback discretization, and belongs to the technical field of laser control. In order to solve the problems of poor frequency stability and tuning range of an existing laser, a laser beam emitted by the laser is incident to an optical feedback assembly to generate front-cavity mirror transmission light; the optical heterodyne feedback adjusting assembly demodulates an electric signal corresponding to the transmission light of the cavity front mirror to obtain an error signal, and transmits the error signal to the high-voltage amplification control module end to control the PZT, so that the high-voltage amplification control module end controls the PZT according to the error signal to lock the laser frequency on the cavity mode frequency; and meanwhile, the laser controller changes the working current of the laser, so that the laser frequency is locked on each intrinsic cavity mode frequency of the optical resonant cavity, and a series of discrete wide-range stable locking frequencies are obtained under the control of the temperature control module.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser control, and in particular relates to a narrow linewidth laser frequency control device and method based on optical feedback discreteness. Background Art

[0002] Most laser applications have certain requirements for laser frequency stability, which refers to the ability of the laser output frequency to remain consistent over a period of time. Laser frequency stability is crucial.

[0003] However, free-running lasers are sensitive to the environment and are easily affected by factors such as ambient temperature and humidity, atmospheric pressure, and mechanical vibration. The output center frequency will drift at the MHz or even GHz level over time, gradually moving away from the initial frequency, seriously affecting the quality of the laser. Therefore, it is necessary to use frequency locking methods to improve the output frequency stability of the laser. After the laser output frequency changes, the system uses the feedback principle to spontaneously pull the frequency back to the set frequency, which is called the automatic frequency locking method.

[0004] In the application of lasers in the optoelectronics industry and related fields, the single-frequency characteristic is one of the important parameters to pay attention to. However, the free-running laser will inevitably be affected by the external environment temperature, vibration and electromagnetic, resulting in a wide line width and drift of the center frequency. Therefore, in the fields of precision machining and precision measurement, it is usually necessary to lock the laser frequency to obtain the narrowest possible laser line width.

[0005] Due to the influence of spontaneous radiation, the operating line width of integrated semiconductor lasers is usually at the MHz level, which limits further applications. Optical feedback technology is an effective method to suppress the frequency noise of semiconductor lasers, but the line width can only be kept narrow when it is limited to a small range. Therefore, the pure optical feedback method is difficult to apply in applications that require long-term locking. Therefore, the existing technology needs further improvement.

[0006] Since the frequency stability of an ultrastable laser depends mainly on the length of its resonant cavity, and the resonant cavity is usually designed to work at the inflection point temperature to obtain the best temperature characteristics. Although this temperature control strategy helps to improve frequency stability, it also limits the laser frequency range in which the cavity length can be adjusted, which is usually in the MHz range. Therefore, ultrastable lasers need to be frequency tuned over a large range and with high precision. Summary of the invention

[0007] In view of the problems of poor frequency stability and tuning range of current lasers, the present invention provides a narrow linewidth laser frequency control device and method based on optical feedback discreteness.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] A narrow linewidth laser frequency control device based on optical feedback discreteness, comprising: a DFB laser, a laser controller, a feedback adjustment element, an optical feedback component, an optical heterodyne feedback adjustment component and a temperature control module;

[0010] The feedback adjustment element includes: a half wave plate, a polarization beam splitter, and a quarter wave plate; the optical feedback component includes: a reflector, a first focusing lens, a piezoelectric ceramic PZT, and an optical resonant cavity; the optical heterodyne feedback adjustment component includes: a radio frequency generation device mixer, a low-pass filter, a PID locking device, a photodetector, a bias device, a high-voltage amplification control module, and a second focusing lens;

[0011] The DFB laser is used to emit laser light; the emitted laser light passes through a half wave plate, a polarization beam splitter and a quarter wave plate in sequence, is incident on a reflector, is reflected and then enters a first focusing lens, and then passes through a piezoelectric ceramic PZT and is incident on an optical resonant cavity to generate cavity front mirror transmitted light; at the same time, optical feedback cavity enhancement technology is used to form optical feedback in the optical resonant cavity; the cavity front mirror transmitted light is received by a second focusing lens of an optical heterodyne feedback adjustment component, and is transmitted to a photodetector, the photodetector is used to detect the optical signal received from the cavity front mirror transmitted light, and convert the optical signal from the cavity front mirror transmitted light into an electrical signal; the electrical signal is then sent to a bias device, the bias device can allow the electrical signal in the electrical signal to pass through, and prevent the entry of the alternating current signal;

[0012] The laser controller is used to tune the laser current to change the output frequency of the DFB laser; the radio frequency generating device is arranged between the laser controller and the mixer, and is used to generate a sinusoidal radio frequency signal and transmit it to the mixer, so that the direct current signal and a sinusoidal radio frequency signal with the same frequency as the modulation signal are mixed through the mixer; and transmitted to the PID locking device through a low-pass filter; the PID locking device then demodulates the received electrical signal to obtain an error signal, and transmits it to the high-voltage amplification control module; so that the high-voltage amplification control module controls the piezoelectric ceramic according to the error signal to achieve a feedback phase equal to an integer multiple of 2π to satisfy the laser frequency Stably locked on the cavity mode frequency.

[0013] Furthermore, the temperature control module places the entire optical path inside, so as to create a temperature-stable external environment for the optical path, thereby reducing the influence of cavity length on frequency drift due to temperature changes.

[0014] The invention discloses a laser frequency locking method based on a narrow line width laser frequency control device with discrete optical feedback. The laser beam emitted by the laser is incident on an optical feedback component. After receiving the laser beam, the optical feedback component generates a cavity front mirror transmission light. The optical heterodyne feedback adjustment component receives the cavity front mirror transmission light, demodulates the electrical signal corresponding to the cavity front mirror transmission light to obtain an error signal, and transmits the error signal to a high-voltage amplifier control module end to control the piezoelectric ceramic PZT, so that the high-voltage amplifier control module end controls the piezoelectric ceramic PZT according to the error signal so that the laser frequency is locked on the cavity mode frequency. At the same time, the laser controller changes the working current of the laser to realize that the laser frequency is locked on each intrinsic cavity mode frequency of the optical resonant cavity, and a series of discrete wide-range stable locking frequencies are obtained under the control of the temperature control module.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] (1) The method of the present invention combines optical feedback and optical heterodyne feedback technology to achieve long-term stable locking, and achieves continuous locking of the DFB laser frequency on a series of continuous cavity modes by directly tuning the current without the need for repeated locking operations.

[0017] (2) The optical resonant cavity adopts a two-mirror V-shaped cavity structure, which reduces the system volume while avoiding the influence of direct reflected light;

[0018] (3) The system is integrated into the temperature control module to avoid frequency drift caused by temperature changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 It is a schematic diagram of the narrow linewidth laser frequency control method.

[0021] Figure numerals: 1. DFB laser; 2. Half wave plate; 3. Polarization beam splitter; 4. Quarter wave plate; 5. Reflector; 6. Focusing lens; 7. Piezoelectric ceramic PZT; 8. Optical resonant cavity; 9. Laser controller; 10. Radio frequency generating device; 11. Mixer; 12. Low-pass filter; 13. PID; 14. Photodetector; 15. Bias device; 16. High-voltage amplification control module; 17. Second focusing lens. DETAILED DESCRIPTION

[0022] In order to gain a deeper understanding of the present invention, we will provide a comprehensive and detailed description of the present invention. However, the present invention has multiple implementations and is not limited to the specific examples listed herein. The presentation of these examples is intended to deepen the comprehensive understanding of the disclosure of the present invention.

[0023] A narrow linewidth laser frequency control device based on optical feedback discreteness, such as Figure 1 Said method comprises: a DFB laser 1, a laser controller 9, a feedback adjustment element, an optical feedback component, an optical heterodyne feedback adjustment component and a temperature control module;

[0024] The feedback adjustment element includes: a half wave plate 2, a polarization beam splitter 3, and a quarter wave plate 4; the optical feedback component includes: a reflector 5, a first focusing lens 6, a piezoelectric ceramic PZT 7, and an optical resonant cavity 8; the optical heterodyne feedback adjustment component includes: a radio frequency generating device 10, a mixer 11, a low-pass filter 12, a PID locking device 13, a photodetector 14, a bias device 15, a high-voltage amplification control module (16), and a second focusing lens 17;

[0025] The DFB laser 1 is used to emit laser light; the emitted laser light passes through the half wave plate 2, the polarization beam splitter 3 and the quarter wave plate 4 in sequence, is incident on the reflector 5, and then enters the first focusing lens 6 after reflection, and then passes through the piezoelectric ceramic PZT7 to be incident on the optical resonant cavity 8 to generate the cavity front mirror transmitted light; at the same time, the optical feedback cavity enhancement technology is used to form optical feedback in the optical resonant cavity 8; the cavity front mirror transmitted light is received by the second focusing lens 17 of the optical heterodyne feedback adjustment component, and is transmitted to the photodetector 14, and the photodetector 14 is used to detect the optical signal of the cavity front mirror transmitted light received, and convert the optical signal of the cavity front mirror transmitted light into an electrical signal; and then the electrical signal is sent to the bias device 15, and the bias device can allow the electrical signal in the electrical signal to pass through and prevent the entry of the alternating current signal;

[0026] The laser controller 9 is used to tune the laser current so that the output frequency of the DFB laser 1 changes; the radio frequency generating device 10 is arranged between the laser controller 9 and the mixer 11, and is used to generate a sinusoidal radio frequency signal and transmit it to the mixer 11, so that the direct current signal and a sinusoidal radio frequency signal with the same frequency as the modulation signal are mixed through the mixer 11; it is transmitted to the PID locking device 13 through the low-pass filter 12; the PID locking device 13 then demodulates the received electrical signal to obtain an error signal, and transmits it to the high-voltage amplification control module 16; so that the high-voltage amplification control module 16 controls the piezoelectric ceramic 7 according to the error signal to achieve a feedback phase equal to an integer multiple of 2π to satisfy the laser frequency Stably locked on the cavity mode frequency.

[0027] Furthermore, the temperature control module places the entire optical path inside, so as to create a temperature-stable external environment for the optical path, thereby reducing the influence of cavity length on frequency drift due to temperature changes.

[0028] The invention discloses a laser frequency locking method based on a narrow line width laser frequency control device with discrete optical feedback. The laser beam emitted by the laser is incident on an optical feedback component. After receiving the laser beam, the optical feedback component generates a cavity front mirror transmission light. The optical heterodyne feedback adjustment component receives the cavity front mirror transmission light, demodulates the electrical signal corresponding to the cavity front mirror transmission light to obtain an error signal, and transmits the error signal to a high-voltage amplifier control module end to control the piezoelectric ceramic PZT, so that the high-voltage amplifier control module end controls the piezoelectric ceramic PZT according to the error signal so that the laser frequency is locked on the cavity mode frequency. At the same time, the laser controller changes the working current of the laser to realize that the laser frequency is locked on each intrinsic cavity mode frequency of the optical resonant cavity, and a series of discrete wide-range stable locking frequencies are obtained under the control of the temperature control module.

[0029] The contents not described in detail in the specification of the present invention belong to the prior art known to the professional and technical personnel in the field. Although the illustrative specific embodiments of the present invention are described above to facilitate the understanding of the present invention by the technical personnel in the field, it should be clear that the present invention is not limited to the scope of the specific embodiments. For the ordinary technical personnel in the field, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

Claims

1. A narrow linewidth laser frequency control device based on optical feedback discreteness, characterized in that: include: DFB laser (1), laser controller (9), feedback adjustment element, optical feedback component, optical heterodyne feedback adjustment component and temperature control module; The feedback adjustment element comprises: a half wave plate (2), a polarization beam splitter (3), and a quarter wave plate (4); the optical feedback component comprises: a reflector (5), a first focusing lens (6), a piezoelectric ceramic PZT (7), and an optical resonant cavity (8); the optical heterodyne feedback adjustment component comprises: a radio frequency generating device (10), a mixer (11), a low-pass filter (12), a PID locking device (13), a photodetector (14), a bias device (15), a high-voltage amplification control module (16), and a second focusing lens (17); The DFB laser (1) is used to emit laser light; the emitted laser light passes through a half wave plate (2), a polarization beam splitter (3) and a quarter wave plate (4) in sequence, is incident on a reflector (5), enters a first focusing lens (6) after being reflected, and then passes through a piezoelectric ceramic PZT (7) to be incident on an optical resonant cavity (8) to generate cavity front mirror transmitted light; at the same time, optical feedback cavity enhancement technology is used to form optical feedback in the optical resonant cavity (8); the cavity front mirror transmitted light is received by a second focusing lens (17) of an optical heterodyne feedback adjustment component, and is transmitted to a photodetector (14); the photodetector (14) is used to detect the optical signal of the cavity front mirror transmitted light received, and convert the optical signal of the cavity front mirror transmitted light into an electrical signal; the electrical signal is then sent to a bias device (15); the bias device can allow the electrical signal in the electrical signal to pass through and prevent the entry of the alternating current signal; The laser controller (9) is used to tune the laser current so that the output frequency of the DFB laser (1) changes; the radio frequency generating device (10) is arranged between the laser controller (9) and the mixer (11) and is used to generate a sinusoidal radio frequency signal and transmit it to the mixer (11), so that the direct current signal and a sinusoidal radio frequency signal with the same frequency as the modulation signal are mixed by the mixer (11); the direct current signal is transmitted to the PID locking device (13) through a low-pass filter (12); the PID locking device (13) then demodulates the received electrical signal to obtain an error signal and transmits it to the high-voltage amplification control module (16); so that the high-voltage amplification control module (16) controls the piezoelectric ceramic (7) according to the error signal to achieve a feedback phase equal to an integer multiple of 2π to ensure that the laser frequency is stably locked on the cavity mode frequency.

2. The narrow linewidth laser frequency control device based on optical feedback discreteness according to claim 1, characterized in that: The temperature control module places the entire optical path inside, and is used to create a temperature-stable external environment for the optical path, so as to reduce the influence of cavity length on frequency drift due to temperature changes.

3. The laser frequency locking method of the narrow linewidth laser frequency control device based on optical feedback discreteness according to claim 1, characterized in that: The laser beam emitted by the laser is incident on the optical feedback component, and the optical feedback component generates the front mirror transmitted light after receiving the laser beam; the optical heterodyne feedback adjustment component receives the front mirror transmitted light, and demodulates the electrical signal corresponding to the front mirror transmitted light to obtain an error signal, and transmits the error signal to the high-voltage amplifier control module end to control the piezoelectric ceramic PZT, so that the high-voltage amplifier control module end controls the piezoelectric ceramic PZT according to the error signal so that the laser frequency is locked on the cavity mode frequency; at the same time, the laser controller changes the working current of the laser to achieve the locking of the laser frequency on each intrinsic cavity mode frequency of the optical resonant cavity, and under the control of the temperature control module, a series of discrete wide-range stable locking frequencies are obtained.

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