CN108879317A - A kind of frequency regulator and frequency-stabilizing method of multi-wavelength continuous laser - Google Patents

Abstract

The invention discloses the frequency regulators and frequency-stabilizing method of a kind of multi-wavelength continuous laser, using under the conditions of not separating the reflected light signal of optical reference chamber, utilize different modulating frequency phase-modulation laser, pass through double balanced mixer demodulated signal, by low-pass filter, non-interfering error system is obtained, the frequency of continuous laser is controlled by servo feedback, realizes a variety of continuous laser frequency stabilization effects of different wave length.It is an advantage of the invention that：A variety of laser of different wave length can be locked on single optical reference chamber simultaneously simultaneously, it is simple for structure, it is easy to accomplish；The complexity for reducing optical path, is easily obtained the error signal of the close laser of wavelength, conducive to the miniaturization of optical system and integrated.

Description

A frequency stabilization device and method for multi-wavelength continuous laser

technical field

The invention belongs to the technical field of continuous lasers, and in particular relates to a frequency stabilization device and a frequency stabilization method for multi-wavelength continuous lasers.

Background technique

Since Maiman invented the laser in 1960, the laser has been used in many fields of scientific research and production. As one of the important branches of laser technology, continuous laser has important applications in many fields such as atomic interferometer, gravitational wave detection, laser spectroscopy and frequency measurement standards, and most experiments require multiple frequency-stabilized lasers with different wavelengths. In the prior art, the frequency-stabilized laser is obtained by locking in the atomic spectrum, and the locking methods include techniques such as saturated absorption spectroscopy and modulation transfer spectroscopy. The CW laser can also be locked on the optical reference cavity by using the Pound-Drever-Hall technique to obtain a frequency-stabilized laser with a sub-Hz linewidth.

The frequency stabilization of multiple lasers with different wavelengths generally uses cavity transfer or optical combs to lock other types of continuous lasers on frequency-stabilized lasers. However, the existing methods rely on frequency-stabilized lasers and transfer cavities or optical combs. The system is complex and the cost is high. .

Contents of the invention

The object of the present invention is to provide a multi-wavelength continuous laser frequency stabilization device and a frequency stabilization method according to the shortcomings of the above-mentioned prior art. The frequency stabilization method uses different modulation frequency phases without separating the reflected optical signal Modulate the laser, demodulate the signal through a double-balanced mixer, and pass through a low-pass filter to obtain an error system that does not interfere with each other. Through servo feedback control, multiple continuous lasers with different wavelengths can be locked on a single optical reference cavity. Based on The Pound-Drever-Hall technology further realizes a variety of continuous laser frequency stabilization effects with different wavelengths.

The object of the present invention is realized by the following technical solutions:

A frequency stabilization device for multi-wavelength continuous lasers, applied to synchronous frequency stabilization modulation of continuous lasers with at least three wavelengths, each of the continuous lasers corresponds to a laser light source, a phase modulation module, and an error analysis module, characterized in that, The frequency stabilization device includes:

At least three of the laser light sources are used to generate continuous laser light with different wavelengths, and adjust the continuous laser light according to the received error signal;

At least three of the phase modulation modules are respectively arranged at the output ends of the corresponding laser light sources, and are used to receive the corresponding continuous laser light, and phase-modulate the continuous laser light into an optical reference cavity;

The optical reference cavity is used to receive each of the continuous lasers collinearly, and reflect a reflected light to a reflected light detection module;

The reflected light detection module is configured to detect the reflected light to generate a reflected signal;

At least three of the error analysis modules are connected to the reflected light detection module and the laser light source corresponding to the continuous laser light and the phase modulation module, and are used to receive the reflected signal and mix the reflected signal The error signal is obtained after frequency, demodulation, and filtering, and the error signal is fed back to the corresponding laser light source of the continuous laser.

Each of the laser light sources includes a servo controller and a laser generator, the servo controller controls the frequency of the continuous laser light emitted by the laser generator; an adjustment module is arranged in the servo controller, and the The adjustment module adjusts the frequency of the currently output continuous laser light according to the error signal.

The wavelength difference between each of the continuous lasers is 10-1000 nanometers.

Each of the continuous lasers is preset with a phase modulation frequency according to its wavelength, and each phase modulation module includes:

An acousto-optic modulator, which shifts the frequency of the continuous laser to meet the condition of resonance with the optical reference cavity, and injects the frequency-shifted continuous laser into a receiving end of a polarization-maintaining optical fiber;

The polarization-maintaining optical fiber transmits the continuous laser light to the output end through the optical fiber;

The electro-optic modulator receives the continuous laser light output from the output end of the polarization-maintaining fiber, and performs phase modulation on the continuous laser light according to the preset phase modulation frequency.

A group of beam mirrors is arranged at the input end of the optical reference cavity for receiving and collinearly processing each of the continuous laser beams to form a combined beam of laser light to enter the optical reference cavity.

The reflected light detection module includes:

a photodetector, configured to detect the reflected light, and generate a reflected signal according to the detection result;

A radio frequency amplifier, connected to the photodetector, is used to amplify the reflected signal.

The error analysis module includes:

A double-balanced mixer, connected to the corresponding phase modulation module, is used to generate a local reference frequency according to the obtained phase modulation frequency, and perform frequency mixing and demodulation according to the reflected signal and the local reference frequency to generate an initial error signal;

A low-pass filter, connected to the double-balanced mixer, for performing signal filtering on the initial error signal to obtain the error signal

The optical reference cavity is an F-P cavity sensor.

A frequency stabilization method involving any one of the frequency stabilization devices for multi-wavelength continuous lasers, characterized in that it is applied to synchronous frequency stabilization modulation of continuous lasers with at least three wavelengths, and each of the continuous lasers corresponds to a laser A light source, a phase modulation module, and an error analysis module, the frequency stabilization method includes the following steps:

Step S1: At least three of the laser light sources simultaneously generate continuous laser light of different wavelengths;

Step S2: At least three of the phase modulation modules respectively receive the corresponding continuous laser light, and perform phase modulation on the continuous laser light;

Step S3: The optical reference cavity collinearly receives each of the continuous lasers, and reflects a reflected light;

Step S4: the reflected light detection module detects the reflected light to generate a reflected signal;

Step S5: At least three of the error analysis modules respectively receive the reflected signals, and perform frequency mixing, demodulation, and filtering on the reflected light signals to obtain error signals, and feed back the error signals to the corresponding laser light source;

Step S6: The laser light source adjusts the continuous laser light according to the error signal.

The advantages of the present invention are: (1) multiple lasers with different wavelengths can be locked on a single optical reference cavity at the same time, and its structure is simple and easy to implement; (2) the reflected light signals are not separated in space, and different modulation frequencies are used, It can reduce the complexity of the optical path, and it is easy to obtain error signals of lasers with similar wavelengths, which is beneficial to the miniaturization and integration of optical systems, and promotes the development of complex experimental systems such as optical clocks.

Description of drawings

Fig. 1 is a structural schematic diagram of a multi-wavelength continuous laser frequency stabilization device in an embodiment of the present invention;

2 is a schematic diagram of transmission paths of optical signals and electrical signals in the frequency stabilization device in an embodiment of the present invention;

Fig. 3 is a schematic diagram of 649 nm laser, 759 nm laser and 770 nm laser locked on the optical reference cavity at the same time in the embodiment of the present invention.

Detailed ways

The features of the present invention and other relevant features are described in further detail below in conjunction with the accompanying drawings through the embodiments, so as to facilitate the understanding of those skilled in the art:

As shown in Figure 1-3, the marks in the figure are: laser light source 1, servo controller 11, laser generator 12, phase modulation module 2, acousto-optic modulator 21, polarization-maintaining fiber 22, electro-optic modulator 23, optical reference cavity 3. Reflected light detection module 4 , photodetector 41 , radio frequency amplifier 42 , error analysis module 5 , modulation frequency 50 , double-balanced mixer 51 , and low-pass filter 52 .

Embodiment: As shown in Figures 1-3, this embodiment specifically relates to a frequency stabilization device and method for multi-wavelength continuous lasers, which are applied to synchronous frequency stabilization modulation of continuous lasers with at least three wavelengths. Under the condition of separating reflected light signals, use different modulation frequencies 50 to phase-modulate the laser, demodulate the signals through a double-balanced mixer 51, pass through a low-pass filter 52, and obtain an error system that does not interfere with each other, and control through servo feedback to realize A variety of continuous lasers with different wavelengths are locked on a single optical reference cavity 3, based on the Pound-Drever-Hall technology to achieve frequency stabilization effects of various continuous lasers with different wavelengths.

As shown in Figure 1-3, a multi-wavelength continuous laser frequency stabilization device includes multiple laser light sources 1, multiple phase modulation modules 2, and multiple error analysis modules 5. Continuous lasers include at least three types, each continuous The laser corresponds to a group of laser light source 1 , phase modulation module 2 and error analysis module 5 , and the frequency stabilization device also includes a shared optical reference cavity 3 and reflected light detection module 4 . Among them, the laser light source 1 is used to generate continuous laser light with different wavelengths, and adjust the continuous laser light according to the received error signal; the phase modulation module 2 is respectively arranged at the output end of the corresponding laser light source 1, and is used to receive the corresponding continuous laser light. laser, and phase-modulate the continuous laser light into an optical reference cavity 3; the optical reference cavity 3 collinearly receives each continuous laser light, and reflects a reflected light to a reflected light detection module 4; the reflected light detection module 4 detects Reflect the light to generate a reflected signal; the error analysis module 5 connects the reflected light detection module 4 and the laser light source 1 and phase modulation module 2 corresponding to the continuous laser, receives the reflected signal, and performs frequency mixing, demodulation, and filtering on the reflected light signal to obtain error signal, and feed back the error signal to the corresponding laser light source 1 of the continuous laser. The solid line in Figure 2 and Figure 3 is the transmission path of the continuous laser, and the dotted line is the transmission path of the electrical signal. The laser light source 1, the modulation module, the optical reference cavity 3, and the reflected light detection module 4 are sequentially connected by an optical path, while the error analysis module 5 is connected to the laser light source 1, the phase modulation module 2, and the reflected light detection module 4. , realize signal transmission and real-time servo feedback. The above solution uses different modulation frequencies to phase-modulate lasers to obtain error signals that do not interfere with each other, so that multiple continuous lasers with different wavelengths are simultaneously locked on a single optical reference cavity 3 .

As shown in Fig. 2 and Fig. 3, laser light source 1 comprises a servo controller 11 and a laser generator 12, and servo controller 11 controls the frequency of the continuous laser light that laser generator 12 emits by electric signal; There is an adjustment module, after the error signal is sent from the error analysis module 5 to the servo controller 11, the adjustment module adjusts the frequency of the continuous laser output currently output by each according to the error signal, and then realizes the synchronous frequency stabilization of various lasers, and the frequency of the continuous laser Locked on optical reference chamber 3. The aforementioned servo feedback is based on error signals that do not interfere with each other, so as to achieve frequency locking on the optical reference cavity 3 . There is a large wavelength difference between the wavelengths of the continuous lasers output by each laser generator 12, which are essentially different types of continuous lasers with a wavelength difference of tens to hundreds of nanometers, and the continuous laser is an unlocked frequency that changes with time , with a wide linewidth, it is an unsteady frequency continuous laser. In this embodiment, a 649 nm semiconductor laser, a 759 nm titanium sapphire laser and a 770 nm semiconductor laser are used for frequency stabilization processing. Therefore, the laser generator 12 uses a semiconductor laser or a titanium sapphire laser.

As shown in Figure 2 and Figure 3, each continuous laser has a preset phase modulation frequency according to its wavelength, and the phase modulation frequencies corresponding to the 649 nm semiconductor laser, 759 nm Ti:sapphire laser and 770 nm semiconductor laser are respectively 14MHz, 19.5MHz, and 24MHz. Each phase modulation module 2 includes: an acousto-optic modulator 21 , a polarization-maintaining fiber 22 , and an electro-optic modulator 23 . The continuous laser light passes through the corresponding acousto-optic modulator 21 twice through the lens group, so as to realize the frequency shift of the continuous laser light to meet the condition of resonating with the optical reference cavity 3 and inject the good frequency shifted continuous laser light into a polarization-maintaining The receiving end of the optical fiber 22; the polarization-maintaining optical fiber 22 transmits the continuous laser to the output end through the optical fiber, and the output end of the optical fiber is an optical fiber collimator with adjustable focal length to adjust the beam waist size and position of the laser beam to meet the mode matching. The continuous laser light exits the polarization maintaining fiber 22 and enters the electro-optic modulator 23 through the purified laser polarization and the Glan prism in sequence. The electro-optic modulator 23 performs phase modulation on the continuous laser light according to a preset phase modulation frequency. The laser phase modulation element can be an electro-optic modulator, which uses different modulation frequencies for different lasers when phase modulating the laser. It is necessary to set an appropriate modulation frequency to ensure that the demodulation errors do not affect each other. The phase modulation of the laser can also adopt other methods such as modulating the current of the semiconductor laser.

As shown in Fig. 2 and Fig. 3, a group of beam mirrors is arranged at the input end of the optical reference cavity 3, and the beam splitter receives and processes each continuous laser light in line to form a combined laser beam and enter the optical reference cavity 3, through The optical path connection realizes the simultaneous incident coupling of the laser and the optical reference cavity 3 and multiple lasers to the optical reference cavity 3 . The optical reference cavity 3 is an FP cavity sensor (Fabry–Perot reference cavity). The optical reference cavity 3 is a medium-fine reference cavity whose fineness is on the order of thousands to tens of thousands. The coating of the optical reference cavity 3 has high reflection characteristics for various wavelengths. The frequency stability of the frequency-stabilized laser follows the stability of the optical reference cavity 3 . The optical reference cavity 3 is a flat concave cavity, placed horizontally in a vacuum chamber with a vacuum degree of 5×10 ^-5 Pa, and its temperature fluctuation is less than 0.01°C. The fineness of the optical reference cavity 3 affects the linewidth of the frequency-stabilized laser, and the control of the environment (temperature, vibration, etc.) where the optical reference cavity 3 is located can also affect the stability of the frequency-stabilized laser.

As shown in FIG. 2 and FIG. 3 , the reflected light detection module 4 includes: a photodetector 41 and a radio frequency amplifier 42 . The reflected light is separated by the polarization beam splitter prism and the quarter-wave plate, and then enters the detection area of the photodetector 41 . The photodetector 41 detects the reflected light and generates a reflected signal according to the detection result; the radio frequency amplifier 42 is connected to the photodetector 41 to amplify the reflected signal to obtain a sufficiently large signal. The photodetector 41 simultaneously detects the reflected signals of multiple continuous lasers of different wavelengths reflected by the optical reference cavity 3 .

As shown in FIG. 2 and FIG. 3 , the amplified reflected signal is divided into three parts, which are respectively sent to respective double-balanced mixers 51 , mixed with the local reference signal, and demodulated the reflected optical signal. The error analysis module 5 includes: a double-balanced mixer 51 and a low-pass filter 52 . The double-balanced mixer 51 obtains the phase modulation frequency through the connection with the phase modulation module 2 to obtain the local reference frequency, and then further mixes and demodulates the reflected signal and the local reference frequency, thereby generating a sum frequency signal, a difference Frequency signal, initial error signal of spurious signal.

The modulation frequency 50 in FIG. 2 and FIG. 3 is a standard radio frequency signal used to drive the electro-optic modulator, and its frequency is the frequency for phase modulation of the laser. The modulation frequency 50 is essentially a frequency signal during transmission, which is sent, received and processed by the electro-optic modulator 23 and the double-balanced mixer 51 at the same time. In this embodiment, the modulation frequencies corresponding to the 649 nm semiconductor laser, the 759 nm titanium sapphire laser and the 770 nm semiconductor laser are 14 MHz, 19.5 MHz and 24 MHz respectively, therefore, the local reference frequency is also based on 14 MHz, 19.5 MHz and 24 MHz generation. The difference frequency signal demodulated by the double-balanced mixer 51 includes all modulation signals and the difference frequency signal of the local reference frequency, thereby causing the error signals to interfere with each other. Therefore, an appropriate modulation frequency 50 and a low-pass filter 52 are used to filter additional demodulated signal. The low-pass filter 52 performs signal filtering on the initial error signal to obtain an error signal. The low-pass filter 52 filters out the sum frequency and spurious signals to obtain error signals that do not interfere with each other. The filtering frequency of the low-pass filter 52 is 1.9 MHz. In the above solution, by using different modulation frequencies 50, the double-balanced mixer 51 can demodulate reflected light signals including multiple modulation information without spatially separating reflected light, thereby avoiding the complexity of the optical path caused by spatially separating reflected light.

As shown in Figures 1-3, the frequency stabilization method of the frequency stabilization device for multi-wavelength continuous lasers in this embodiment is applied to synchronous frequency stabilization modulation of continuous lasers with at least three wavelengths, and each continuous laser corresponds to a laser light source 1 , phase modulation module 2, error analysis module 5, the frequency stabilization method comprises the following steps:

Step S1: At least three laser light sources 1 simultaneously generate continuous laser light of different wavelengths;

Step S2: At least three phase modulation modules 2 respectively receive the corresponding continuous laser light, and perform phase modulation on the continuous laser light;

Step S3: The optical reference cavity 3 collinearly receives each continuous laser light and reflects a reflected light;

Step S4: the reflected light detection module 4 detects the reflected light to generate a reflected signal;

Step S5: at least three error analysis modules 5 respectively receive the reflected signals, and perform frequency mixing, demodulation, and filtering on the reflected optical signals to obtain error signals, and feed back the error signals to the corresponding laser light source 1;

Step S6: The laser light source 1 adjusts the continuous laser light according to the error signal.

In other words, the above process is equivalent to: multiple continuous lasers with different wavelengths are firstly phase-modulated, and then combined and coupled into the optical reference cavity 3, and the reflected optical signal is detected through the optical path and a single photodetector 41; The reflected light signals are respectively sent to respective double-balanced mixers 51, mixed with respective local reference frequencies, and passed through respective low-pass filters 52 to obtain error signals which do not interfere with each other; the respective error signals are sent to respective servo The adjustment module of the controller 11, the adjustment module controls the actuators of the respective lasers based on the feedback signal, so that multiple lasers can be locked on a single optical reference cavity 3 at the same time to obtain frequency-stabilized lasers.

The beneficial effects of this embodiment are: (1) multiple lasers with different wavelengths can be locked on a single optical reference cavity 3 at the same time, and its structure is simple and easy to implement; (2) the reflected optical signals are not separated in space, and different Frequency modulation can reduce the complexity of the optical path, and it is easy to obtain error signals of lasers with similar wavelengths, which is conducive to the miniaturization and integration of optical systems, and promotes the development of complex experimental systems such as optical clocks.

Claims (9)

1. A frequency stabilization device for multi-wavelength continuous lasers, applied to at least three wavelengths of continuous lasers for synchronous frequency stabilization modulation, each of the continuous lasers corresponds to a laser light source, a phase modulation module, and an error analysis module, its characteristics In that, the frequency stabilizing device includes: At least three of the laser light sources are used to generate continuous laser light with different wavelengths, and adjust the continuous laser light according to the received error signal; At least three of the phase modulation modules are respectively arranged at the output ends of the corresponding laser light sources, and are used to receive the corresponding continuous laser light, and phase-modulate the continuous laser light into an optical reference cavity; The optical reference cavity is used to receive each of the continuous lasers collinearly, and reflect a reflected light to a reflected light detection module; The reflected light detection module is configured to detect the reflected light to generate a reflected signal; At least three of the error analysis modules are connected to the reflected light detection module and the laser light source corresponding to the continuous laser light and the phase modulation module, and are used to receive the reflected signal and mix the reflected signal The error signal is obtained after frequency, demodulation, and filtering, and the error signal is fed back to the corresponding laser light source of the continuous laser. 2. The frequency stabilizing device of a kind of multi-wavelength continuous laser according to claim 1, is characterized in that, each described laser light source comprises a servo controller and a laser generator, and described servo controller controls described laser The frequency of the continuous laser light emitted by the generator; an adjustment module is arranged in the servo controller, and the adjustment module adjusts the frequency of the current output continuous laser light according to the error signal. 3 . The frequency stabilization device for multi-wavelength continuous lasers according to claim 1 , wherein the wavelength difference between each of the continuous lasers is 10-1000 nanometers. 4. the frequency stabilization device of a kind of multi-wavelength continuous laser according to claim 1, is characterized in that, each described continuous laser has a phase modulation frequency preset according to its wavelength, and each described phase modulation module comprises: An acousto-optic modulator, which shifts the frequency of the continuous laser to meet the condition of resonance with the optical reference cavity, and injects the frequency-shifted continuous laser into a receiving end of a polarization-maintaining optical fiber; The polarization-maintaining optical fiber transmits the continuous laser light to the output end through the optical fiber; The electro-optic modulator receives the continuous laser light output from the output end of the polarization-maintaining fiber, and performs phase modulation on the continuous laser light according to the preset phase modulation frequency. 5. the frequency stabilization device of a kind of multi-wavelength continuous laser according to claim 1, is characterized in that, the input end of described optical reference cavity is provided with a group of beam mirrors, is used to receive and collinearly process each The continuous laser light is injected into the optical reference cavity to form a combined laser beam. 6. The frequency stabilization device of a multi-wavelength continuous laser according to claim 1, wherein the reflected light detection module comprises: a photodetector, configured to detect the reflected light, and generate a reflected signal according to the detection result; A radio frequency amplifier, connected to the photodetector, is used to amplify the reflected signal. 7. The frequency stabilization device of a kind of multi-wavelength continuous laser according to claim 1, is characterized in that, error analysis module comprises: A double-balanced mixer, connected to the corresponding phase modulation module, is used to generate a local reference frequency according to the obtained phase modulation frequency, and perform frequency mixing and demodulation according to the reflected signal and the local reference frequency to generate an initial error signal; A low-pass filter, connected to the double-balanced mixer, for performing signal filtering on the initial error signal to obtain the error signal. 8. A multi-wavelength continuous laser frequency stabilization device according to claim 1, wherein the optical reference cavity is an F-P cavity sensor. 9. A frequency stabilization method related to the frequency stabilization device of the multi-wavelength continuous laser described in any one of claims 1-8, characterized in that, it is applied to synchronous frequency stabilization modulation of continuous laser light of at least three wavelengths, each A described continuous laser corresponds to a laser light source, a phase modulation module, and an error analysis module, and the frequency stabilization method includes the following steps: Step S1: At least three of the laser light sources simultaneously generate continuous laser light of different wavelengths; Step S2: At least three of the phase modulation modules respectively receive the corresponding continuous laser light, and perform phase modulation on the continuous laser light; Step S3: The optical reference cavity collinearly receives each of the continuous lasers, and reflects a reflected light; Step S4: the reflected light detection module detects the reflected light to generate a reflected signal; Step S5: At least three of the error analysis modules respectively receive the reflected signals, and perform frequency mixing, demodulation, and filtering on the reflected light signals to obtain error signals, and feed back the error signals to the corresponding laser light source; Step S6: The laser light source adjusts the continuous laser light according to the error signal.