Miniature narrow linewidth laser system and method based on echo wall microcavity locking

Abstract

The invention discloses a miniature narrow linewidth laser system and method based on echo wall microcavity locking, the miniature narrow linewidth laser system comprises an external cavity laser, an electro-optical modulator, an echo wall microcavity, a photoelectric detector, a phase-locked amplification module and a servo controller, the external cavity laser outputs light to the electro-optical modulator, and frequency sidebands are increased based on the electro-optical modulator; an optical signal is emitted by the echo wall microcavity and is converted into an electric signal based on the photoelectric detector, and the electric signal generates an error signal based on the phase-locked amplification module and is used for adjusting parameters of the servo controller and locking the frequency of light output by the external cavity laser to the resonant frequency of the microcavity. Through the structure, the problems that an existing laser is large in size and inconvenient to carry, and due to the fact that the FP cavity has high requirements for a high-reflectivity lens, a high-precision cavity regulator and a high-stability controller, the manufacturing and maintenance cost of the FP cavity is high, and a laser capable of carrying narrow linewidth is difficult to produce are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of optical devices, and in particular to a miniature narrow-linewidth laser system and method based on whispering gallery microcavity locking. Background Art

[0002] Narrow linewidth technology mainly refers to reducing the spectrum width of the laser through various means to make it close to a single frequency output. It is usually used in high-precision measurement, quantum computing, optical atomic clocks, laser cooling and other fields.

[0003] Linewidth lasers achieve very high coherence and precision by reducing noise and stabilizing frequency. PDH (Pound-Drever-Hall) locking is a frequency stabilization technique used to accurately lock the frequency of the laser to the resonant frequency of the Fabry-Perot cavity (FP cavity).

[0004] PDH locking technology uses phase modulation technology to modulate the laser frequency into a main frequency and two sidebands (two frequency components formed by the modulation frequency above and below the main frequency). When the laser is incident on the FP cavity, if the main frequency of the laser is not completely consistent with the resonant frequency of the FP cavity, a frequency-shifted reflected light will be generated in the cavity. By analyzing the phase information of the reflected light, an error signal can be generated to indicate the direction and amplitude of the deviation of the laser frequency from the resonant frequency of the FP cavity. The free spectral range (FSR) of the FP cavity determines the discrete frequency intervals allowed to pass, while the quality factor (Q factor) of the cavity determines the selectivity and linewidth compression capabilities of these frequencies.

[0005] Existing means compress the line width of the laser to an extremely narrow range by optimizing the design of the FP cavity. However, the FP cavity with a high quality factor is extremely sensitive to the environment. Changes in temperature and vibration will greatly cause frequency drift, resulting in unstable output. Therefore, the FP cavity is usually subject to strict temperature control and vibration isolation, resulting in a large size and inconvenient transportation. In addition, since the FP cavity has high requirements for high-reflectivity lenses, high-precision cavity regulators and high-stability controllers, its manufacturing and maintenance costs are relatively high.

[0006] Therefore, there is an urgent need for a miniature narrow-linewidth laser system and method based on whispering gallery microcavity locking to overcome the above problems. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a miniature narrow-linewidth laser system and method based on whispering gallery microcavity locking, so as to solve the problems of bulky size, inconvenient transportation, high manufacturing and maintenance costs due to the high requirements of the FP cavity on high-reflectivity lenses, high-precision cavity regulators and high-stability controllers, and difficulty in producing portable narrow-linewidth lasers.

[0008] In order to solve the above technical problems, the present invention provides a miniature narrow linewidth laser system based on whispering gallery microcavity locking, comprising:

[0009] External cavity lasers, electro-optic modulators, whispering gallery microcavities, photodetectors, phase-locked amplifier modules, and servo controllers;

[0010] The external cavity laser outputs light to the electro-optic modulator, and frequency sidebands are added based on the electro-optic modulator, and input into the whispering gallery microcavity, the whispering gallery microcavity emits a light signal, and the light signal is converted into an electrical signal based on the photodetector, and the electrical signal generates an error signal based on the phase-locked amplifier module, which is used to adjust the parameters of the servo controller and lock the frequency of the output light of the external cavity laser to the resonance frequency of the microcavity.

[0011] As an improvement of the present invention, the external cavity laser comprises:

[0012] Interference filter, laser diode, collimating lens, cat's eye structure, the light output by the laser diode passes through the collimating lens, interference filter, cat's eye structure in sequence to form light feedback, and the wavelength of the output laser is changed by adjusting the central wavelength of the laser diode.

[0013] As an improvement of the present invention, the diameter of the whispering gallery microcavity is set to 9.5 mm, the surface root mean square roughness of the whispering gallery microcavity is set to 0.26n, and the whispering gallery microcavity adopts a MgF2 crystal whispering gallery microcavity.

[0014] As an improvement of the present invention, the optical volume of the laser generated by the external cavity laser and the whispering gallery microcavity is less than 20 cm×10 cm×4 cm.

[0015] As an improvement of the present invention, the line width of the laser is narrowed to 3 Hz based on the external cavity laser and the whispering gallery microcavity.

[0016] As an improvement of the present invention, the output stability of the laser is set to 6.0×10 -12 @0.1s.

[0017] As another improvement of the present invention, a method for generating a portable laser based on a miniature narrow linewidth laser is provided, the method comprising the following steps:

[0018] S1, turning on the laser power supply of the external cavity laser, and setting the operating temperature and operating current of the external cavity laser based on the power supply control software;

[0019] S2, increasing current scanning on the external cavity laser, observing the output signal of the photodetector, and adjusting the signal-to-noise ratio of the transmission signal after passing through the whispering gallery microcavity;

[0020] S3, changing the operating current and the operating temperature of the external cavity laser during operation, finding the transmission peak of the transmission extinction ratio, and gradually narrowing the scanning range;

[0021] S4, turn on the signal generator to output the modulation signal, and adjust the phase of the modulation signal to the error signal to obtain the maximum slope;

[0022] S5. Turn on the servo controller, change parameters, turn off scanning, reduce the amplitude of the error signal to the minimum value, and complete locking.

[0023] As an improvement of the present invention, the micro external cavity laser adopts micro optical path technology to reduce the volume to 40mm×35mm×5mm.

[0024] As an improvement of the present invention, the micro external cavity laser can be modulated at high speed.

[0025] After adopting such a design, the present invention has at least the following advantages:

[0026] The miniature narrow-linewidth laser system based on whispering gallery microcavity locking reduces the volume of the entire device through miniaturized external cavity laser and whispering gallery microcavity, and narrows the linewidth of the generated laser to the order of ten hertz, with a laser output stability of 6.0×10 -12 @0.1s, the overall optical volume is less than 20cm (length) × 10cm (width) × 4cm (height), which reduces the volume, facilitates transportation, and reduces its manufacturing and maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0028] Figure 1 The module flow diagram of a miniature narrow linewidth laser system based on whispering gallery microcavity locking in one embodiment of the present invention.

[0029] Figure 2 It is a module workflow diagram of the miniature narrow linewidth laser system based on whispering gallery microcavity locking in the present invention.

[0030] Figure 3 It is a schematic diagram of the structure of the internal components of the micro external cavity laser in the present invention.

[0031] Figure 4 The structure of the whispering gallery microcavity in the present invention is shown in FIG. Figure 1 .

[0032] Figure 5 The structure of the whispering gallery microcavity in the present invention is shown in FIG. Figure 2 .

[0033] Description of reference numerals:

[0034] 1. External cavity laser; 11. Diode; 12. Collimating lens; 13. Interference filter; 14. Cat's eye structure; 2. Electro-optic modulator; 3. Polarization controller; 4. Whispering gallery microcavity; 5. Photodetector; 6. Signal generator; 7. Servo controller; 8. Laser power supply. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings.

[0036] See also Figures 1 to 5 A specific implementation of a miniature narrow-linewidth laser system and method based on whispering gallery microcavity locking is shown.

[0037] like Figure 1 and Figure 2 As shown, in this embodiment, the miniature narrow linewidth laser system based on the locking of the whispering gallery microcavity 4 includes an external cavity laser 1, an electro-optic modulator 2, a whispering gallery microcavity 4, a photodetector 5, a phase-locked amplifier module and a servo controller 7. The external cavity laser 1 outputs light to the electro-optic modulator 2, and adds a frequency sideband based on the electro-optic modulator 2, which is input to the whispering gallery microcavity 4. The whispering gallery microcavity 4 emits a light signal, which is converted into an electrical signal based on the photodetector 5. The electrical signal generates an error signal based on the phase-locked amplifier module, which is used to adjust the parameters of the servo controller 7 and lock the frequency of the output light of the external cavity laser 1 to the resonance frequency of the microcavity. The FP cavity with a high quality factor is extremely sensitive to the environment. Changes in temperature and vibration will greatly cause frequency drift, resulting in unstable output. Therefore, a small-volume external cavity laser 1 is used to generate a narrow-linewidth laser through the above-mentioned means.

[0038] Specifically, Figures 1 to 5As shown, the external cavity laser 1 includes an interference filter 13, a laser diode 11, a collimating lens 12, and a cat's eye structure 14. The light output by the laser diode 11 passes through the collimating lens 12, the interference filter 13, and the cat's eye structure 14 in sequence to form optical feedback. The wavelength of the output laser is changed by adjusting the angle of the interference filter 13. The diameter of the whispering gallery microcavity 4 is set to 9.5 mm, and the surface root mean square roughness of the whispering gallery microcavity 4 is set to 0.26n. The whispering gallery microcavity 4 adopts a MgF2 crystal whispering gallery microcavity 4. The micro narrow linewidth laser system locked by the whispering gallery microcavity 4 adopts a PD The PDH locking technology is composed of the following: the output light of the external cavity laser 1 is increased with frequency sidebands by the electro-optic modulator 2, and is input into the whispering gallery microcavity 4 through the polarization controller 3. The light signal emitted from the whispering gallery microcavity 4 is detected by the photodetector 5 and converted into an electrical signal. The output frequency of the external cavity laser 1 is scanned to make the output of the external cavity laser 1 close to the resonance frequency of the whispering gallery microcavity 4. After the resonance frequency corresponds, an error signal is generated by the electrical signal of the phase-locked amplifier module. The error signal is used to adjust the parameters of the servo controller 7 to lock the output frequency of the external cavity laser 1 to the resonance frequency of the whispering gallery microcavity 4.

[0039] It is understandable that if Figure 4 and Figure 5 As shown, the optical volume of the laser generated by the external cavity laser 1 and the whispering gallery microcavity 4 is less than 20 cm × 10 cm × 4 cm, the line width of the laser is narrowed to 3 Hz, and the output stability of the laser is set to 6.0 × 10 -12 @0.1s.

[0040] On the other hand, the present invention also discloses a method for generating a portable laser based on a miniature narrow linewidth laser system, the method comprising the following steps:

[0041] S1, turning on the laser power supply 8 of the external cavity laser 1, and setting the operating temperature and operating current of the external cavity laser 1 based on the power supply control software;

[0042] S2, increasing the current scanning of the external cavity laser 1, observing the output signal of the photodetector 5, and adjusting the signal-to-noise ratio of the transmission signal after passing through the whispering gallery microcavity 4;

[0043] S3, changing the operating current and the operating temperature of the external cavity laser 1 during operation, finding the transmission peak of the transmission extinction ratio, and gradually narrowing the scanning range;

[0044] S4, turn on the signal generator 6 to output the modulation signal, and adjust the phase of the modulation signal to the error signal to obtain the maximum slope;

[0045] S5, turn on the servo controller 7, change the parameters, turn off the scan, reduce the amplitude of the error signal to the minimum value, and complete the locking.

[0046] In the present embodiment S1, the current value of the operating current of the external cavity laser 1 is greater than 40 mA, and the operating temperature is set to 28 degrees Celsius.

[0047] In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "front", "rear", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0048] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Those skilled in the art may make some simple modifications, equivalent changes or modifications using the technical contents disclosed above, which all fall within the protection scope of the present invention.

Claims

1. A miniature narrow linewidth laser system based on whispering gallery microcavity locking, characterized in that: include: External cavity lasers, electro-optic modulators, whispering gallery microcavities, photodetectors, phase-locked amplifier modules, and servo controllers; The external cavity laser outputs light to the electro-optic modulator, and frequency sidebands are added based on the electro-optic modulator, and input into the whispering gallery microcavity, the whispering gallery microcavity emits a light signal, and the light signal is converted into an electrical signal based on the photodetector, and the electrical signal generates an error signal based on the phase-locked amplifier module, which is used to adjust the parameters of the servo controller and lock the frequency of the output light of the external cavity laser to the resonance frequency of the microcavity.

2. The miniature narrow linewidth laser system based on whispering gallery microcavity locking according to claim 1, characterized in that: The external cavity laser comprises: Interference filter, laser diode, collimating lens, cat's eye structure, the light output by the laser diode passes through the collimating lens, interference filter, cat's eye structure in sequence to form light feedback, and the wavelength of the output laser is changed by adjusting the central wavelength of the laser diode.

3. The miniature narrow linewidth laser system based on whispering gallery microcavity locking according to claim 2 is characterized in that: The diameter of the whispering gallery microcavity is set to 9.5 mm, the surface root mean square roughness of the whispering gallery microcavity is set to 0.26n, and the whispering gallery microcavity adopts a MgF2 crystal whispering gallery microcavity.

4. The small frequency-stabilized laser system based on whispering gallery microcavity locking according to claim 3 is characterized in that: The optical volume of the laser generated based on the external cavity laser and the whispering gallery microcavity is less than 20cm×10cm×4cm.

5. The miniature narrow linewidth laser system based on whispering gallery microcavity locking according to claim 3 is characterized in that: Based on the external cavity laser and the whispering gallery microcavity, the line width of the laser is narrowed to 3 Hz.

6. The miniature narrow linewidth laser system based on whispering gallery microcavity locking according to claim 3 is characterized in that: Based on the external cavity laser and the whispering gallery microcavity, the output stability of the laser is set to 6.0×10 -12 @0.1s.

7. A method for generating portable laser based on a miniature narrow linewidth laser system, characterized in that: The method comprises the following steps: S1, turning on the laser power supply of the external cavity laser, and setting the operating temperature and operating current of the external cavity laser based on the power supply control software; S2, increasing current scanning on the external cavity laser, observing the output signal of the photodetector, and adjusting the signal-to-noise ratio of the transmission signal after passing through the whispering gallery microcavity; S3, changing the operating current and the operating temperature of the external cavity laser during operation, finding the transmission peak of the transmission extinction ratio, and gradually narrowing the scanning range; S4, turn on the signal generator to output the modulation signal, and adjust the phase of the modulation signal to the error signal to obtain the maximum slope; S5. Turn on the servo controller, change parameters, turn off scanning, reduce the amplitude of the error signal to the minimum value, and complete locking.

8. The method for generating portable laser based on a miniature narrow linewidth laser system according to claim 7, characterized in that: The current value of the working current is greater than 40mA.

9. The method for generating portable laser based on a miniature narrow linewidth laser system according to claim 7, characterized in that: The operating temperature is set at 28 degrees Celsius.

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