CN117791289A - PDH frequency stabilization all-fiber laser system based on optical fiber F-P cavity - Google Patents
PDH frequency stabilization all-fiber laser system based on optical fiber F-P cavity Download PDFInfo
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- 230000037431 insertion Effects 0.000 claims description 9
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- 229910052783 alkali metal Inorganic materials 0.000 description 2
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- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 description 1
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Abstract
The invention provides a PDH frequency stabilization all-fiber laser system based on an optical fiber F-P cavity, which comprises: a laser for laser output; the light conduction device is connected with the laser, and is used for splitting laser output by the laser, outputting one path of light and modulating the other path of light; the optical fiber F-P cavity is connected with the optical conduction device, and is used for carrying out multiple reflection on the light subjected to the modulation treatment of the other path and outputting the light; and the control device is respectively connected with the optical conduction device and the laser, receives and processes the optical signals output by the optical fiber F-P cavity, outputs feedback signals, tunes the output laser frequency of the laser and stabilizes the frequency of the laser output laser. The invention has the advantages that the size of the F-P cavity of the optical fiber is the same as that of the optical fiber, the volume is smaller, the constant-temperature vibration isolation packaging is easy to carry out, all optical fiber devices are connected through an optical fiber welding process or an optical fiber connector, the optical path is built and debugged simply, and the connection reliability of an optical path system is ensured, so that the laser system has a compact structure.
Description
Technical Field
The invention belongs to the technical field of laser frequency stabilization, and particularly relates to a PDH frequency stabilization all-fiber laser system based on an optical fiber F-P cavity.
Background
In the existing frequency stabilization technology research of the F-P cavity-based laser, a space F-P cavity interferometer is adopted as a frequency discriminator, the curvature radius of a reflector of the space F-P cavity interferometer is 50mm, the distance between two cavity mirrors is 50mm, a collimator and a convex lens are adopted to make mode matching between a front-stage optical path and a space F-P cavity, an optical fiber optical path is adopted as a front surface light source optical path of the space F-P cavity, a space optical path is adopted as an optical path after an electro-optical modulator, a lens is required to be matched for conversion between the optical fiber optical path and the space optical path, and the optical path part of the whole system has complicated manufacture and debugging due to the existence of the optical fiber optical path and the space optical path; in the all-fiber laser frequency stabilization device, however, the core key device adopts an alkali metal heat atom steam chamber, the size of the alkali metal heat atom steam chamber is not compact enough, and the packaging volume is larger.
Disclosure of Invention
In view of the above, the present invention provides a PDH frequency stabilized all-fiber laser system based on an optical fiber F-P cavity, so as to solve the above or other problems in the prior art.
In order to solve the technical problems, the invention adopts the following technical scheme: a PDH frequency stabilized all-fiber laser system based on an optical fiber F-P cavity, comprising:
a laser for laser output;
the light conduction device is connected with the laser, and is used for splitting laser output by the laser, outputting one path of light and modulating the other path of light;
the optical fiber F-P cavity is connected with the optical conduction device, and is used for carrying out multiple reflection on the light subjected to the modulation treatment of the other path and outputting the light;
and the control device is respectively connected with the optical conduction device and the laser, receives and processes the optical signals output by the optical fiber F-P cavity, outputs feedback signals, tunes the output laser frequency of the laser and stabilizes the frequency of the laser output laser.
Further, the optical conduction device comprises a light splitting device, a phase modulation device and a transmission device which are sequentially connected, the light splitting device is connected with the laser and divides laser of the laser into two beams, the phase modulation device carries out phase modulation on one path of light phase after light splitting, and modulated light enters the optical fiber F-P cavity through the signal transmission device.
Further, the optical conduction device further comprises an acousto-optic modulation device which is respectively connected with the laser and the light splitting device and used for adjusting the frequency of the output laser of the laser.
Further, the light splitting device is an optical fiber light splitter, and the polarization extinction ratio of the optical fiber light splitter is more than 18dB;
the phase modulation device is an optical fiber coupling phase modulator, the modulation broadband of the optical fiber coupling phase modulator is not less than 100MHz, and the insertion loss is less than 10dB;
the transmission device is an optical fiber circulator, and the fineness of the optical fiber F-P cavity is more than 10000.
Further, the control device comprises a photoelectric detection device, a modulation module, a demodulation module and a PID control module, wherein,
the photoelectric detection device is respectively connected with the transmission device and the demodulation module, receives the optical signal output by the transmission device and transmits the optical signal to the demodulation module;
the modulation module is respectively connected with the phase modulation device and the demodulation module, and the modulation module outputs a radio frequency signal to the phase modulation device so that the phase modulation device carries out phase modulation on laser;
the demodulation module carries out frequency mixing demodulation processing on the intrinsic signal output by the modulation module and the photoelectric signal output by the photoelectric detection device to obtain a drift error signal of the laser;
the PID control module is respectively connected with the demodulation circuit and the laser, processes the error signal, and controls the laser to act to tune the output laser frequency.
Furthermore, the laser is a single-frequency narrow linewidth laser and is provided with a piezoelectric control device.
Further, the control device comprises a photoelectric detection device, a modulation module, a demodulation module, an acousto-optic adjustment module and a PID control module, wherein,
the photoelectric detection device is respectively connected with the transmission device and the demodulation module, receives the optical signal output by the transmission device and transmits the optical signal to the demodulation module;
the modulation module is respectively connected with the phase modulation device and the demodulation module, and the modulation module outputs a radio frequency signal to the phase modulation device so that the phase modulation device carries out phase modulation on laser;
the demodulation module carries out frequency mixing demodulation processing on the intrinsic signal output by the modulation module and the photoelectric signal output by the photoelectric detection device to obtain a drift error signal of the laser;
the PID control module is respectively connected with the demodulation circuit, the acousto-optic adjustment module and the laser, processes the error signal, controls the action of the laser to tune the output laser frequency, controls the acousto-optic adjustment module to drive the acousto-optic modulation device to act, and adjusts the output laser frequency of the laser.
Further, the photoelectric detection device is a photoelectric detector, and the bandwidth of the photoelectric detector is larger than the bandwidth of the radio frequency signal of the phase modulation device;
the modulation module is a modulation circuit, and the frequency and the radio frequency power of an output radio frequency signal of the modulation circuit are adjustable;
the demodulation module is a demodulation circuit, and the PID control module is a PID control circuit.
Furthermore, the F-P cavity of the optical fiber is packaged with constant temperature vibration isolation.
Further, the acousto-optic modulation module is an acousto-optic modulator driving circuit.
By adopting the technical scheme, the PDH frequency stabilization all-fiber laser system based on the fiber F-P cavity is provided with the fiber circuit and the electric signal circuit which are connected, and the fiber circuit modulates laser according to the feedback signal of the electric signal circuit to inhibit external interference so as to ensure that the laser frequency output by the laser is stable; the optical fiber line is provided with an optical fiber F-P cavity which is used as a reference cavity, has the same size as the optical fiber, has the size advantage compared with a space type optical device, has smaller volume, is easy to perform constant temperature vibration isolation packaging, and has smaller size compared with the space type optical device after packaging;
the optical fiber circuit is connected with the laser, the optical fiber circuit is provided with an acousto-optic modulation device, a light splitting device, a phase modulation device and an optical fiber circulator which are sequentially connected, the acousto-optic modulation device, the light splitting device, the phase modulation device and the optical fiber circulator are all polarization maintaining optical fiber coupling devices, laser output by the laser enters the light splitting device after being modulated by the acousto-optic modulation device, the laser is split into two beams of light by the light splitting device, one beam of light is output, the other beam of light enters the phase modulation device, the beam of laser enters an optical fiber F-P cavity after being modulated by the phase, the laser is output by the optical fiber circulator after being reflected for many times, a photoelectric detection device in the electric signal circuit receives the output optical signal, the optical signal is mixed with an intrinsic signal of a driving signal output by the modulation circuit to the phase modulation device in the demodulation circuit, an error signal containing frequency detuning information is obtained, the error signal is fed back to the laser and the acousto-optic modulation device by the PID control circuit, the frequency of the laser is compensated in low frequency and high frequency, the PID control circuit continuously adjusts the driving signal of the laser according to deviation of the feedback information and a set value, and thus the interference frequency of the laser is stabilized;
each optical fiber device is connected through an optical fiber fusion process or an optical fiber connector, the optical path is built and debugged simply, the connection reliability of an optical path system is improved, and the mode matching between a preceding optical path and an optical fiber F-P cavity is not required to be carried out through a complex mode conversion optical path, so that the laser system is compact in structure.
Drawings
FIG. 1 is a schematic diagram of a PDH frequency stabilized all-fiber laser system based on an optical fiber F-P cavity according to a first embodiment of the present invention;
fig. 2 is a schematic structural diagram of a PDH frequency stabilized all-fiber laser system based on an optical fiber F-P cavity according to a second embodiment of the present invention.
In the figure:
1. laser 2, acousto-optic modulation device 3, and spectroscopic device
4. Phase modulation device 5, transmission device 6 and optical fiber F-P cavity
7. Photoelectric detection device 8, modulation module 9 and demodulation module
10. PID control module 11 and acousto-optic adjustment module
Detailed Description
The invention will be further described with reference to the drawings and the specific examples.
Fig. 1 shows a schematic structural diagram of an embodiment of the present invention, where the present embodiment relates to a PDH frequency stabilization all-fiber laser system based on an optical fiber F-P cavity, where an entire optical path of a light conduction device is an optical fiber optical path, and the optical path connection is simple, and the entire laser system is made to be more compact by using the optical fiber F-P cavity and an optical fiber circulator with 3 ports, and a control device receives a laser signal output by the optical fiber F-P cavity, modulates and demodulates the laser, generates a feedback signal, and controls and adjusts an output frequency of the laser according to the error signal, so that an output laser frequency of the laser is stable.
Example 1
A PDH frequency stabilization all-fiber laser system based on an optical fiber F-P cavity is characterized in that the PDH frequency stabilization is realized by utilizing an ultra-stable optical cavity as a frequency reference and adopting an electro-optic phase modulation and phase demodulation method. Specifically, the PDH frequency stabilization all-fiber laser system based on the fiber F-P cavity, as shown in fig. 1, comprises:
a laser 1 for outputting laser light;
the light conduction device is connected with the laser 1 and is used for conducting laser output by the laser 1 and outputting light at the same time;
the optical fiber F-P cavity 6 is connected with the optical conduction device, and laser transmitted into the optical fiber F-P cavity 6 is reflected for multiple times and output;
the control device is respectively connected with the optical conduction device and the laser 1, processes the optical signal output by the optical fiber F-P cavity 6, outputs an error signal and a feedback signal, and respectively controls the optical conduction device and the laser 1 according to the error signal and the feedback signal so that the laser 1 outputs laser with stable frequency;
when the PDH frequency stabilization all-fiber laser system based on the fiber F-P cavity works, laser output by the laser 1 is conducted through the light conduction device, in the laser conduction process, the light conduction device divides laser output by the laser 1 into two paths, one path of light is output and is used as final output light for a user to conduct the other path of light, the other path of light enters the fiber F-P cavity 6, the other path of light is reflected and output for many times in the fiber F-P cavity 6, an output optical signal is received by the control device, the control device processes the received optical signal to obtain an error signal and a feedback signal, the light conduction device receives the error signal to adjust, and the laser 1 receives the feedback signal to adjust, so that the output laser frequency of the laser 1 is kept stable, and the stability of the laser frequency output by the laser 1 is realized.
Specifically, in this embodiment, the laser 1 is a single-frequency narrow-linewidth laser, which may be an optical fiber laser, an optical fiber coupling output type semiconductor laser, or other types of lasers, where the effective linewidth of the single-frequency narrow-linewidth laser is within 200KHz, the output optical power is greater than 1mW, and a temperature detection device, such as a temperature sensor, is built in the single-frequency narrow-linewidth laser, and meanwhile, the single-frequency narrow-linewidth laser is further provided with a wavelength tuning function unit, such as a laser driving current or a piezoelectric actuator, and the output laser is a linear polarization laser, and the type of the laser 1 is selected according to practical requirements, which is not specifically required herein.
The above-mentioned light conduction device includes the acousto-optic modulation device 2, the beam splitting device 3, the phase modulation device 4 and the transmission device 5 that are connected in turn, the acousto-optic modulation device 2 is connected with the laser 1, the transmission device 5 is connected with the optic fibre F-P chamber 6, and the transmission device 5 is connected with the controlling means, the laser that the laser 1 output is received by the acousto-optic modulation device 2, the output frequency of the laser 1 is adjusted and handled by the acousto-optic modulation device 2, the laser after handling by the acousto-optic modulation device 2 enters the beam splitting device 3, the beam splitting device 3 splits the laser, the laser 1 output is split into two ways, one way of light is output, the other way of light enters the phase modulation device 4, modulate the other way of light phase after splitting, the modulated light enters the optic fibre F-P chamber 6 through the signal transmission device 5, make the output laser of the laser 1 enter the optic fibre F-P chamber 6 after being reflected in the optic fibre F-P chamber 6 a plurality of times, output through the transmission device 5, transmit to the controlling means, the setting of the light conduction device realizes the setting of the laser 1 and the laser frequency of the laser, the phase of the output and the laser 1 is adjusted and the phase of the laser after splitting the output and the laser.
The above-mentioned acousto-optic modulation device 2 is used for fine tuning the laser frequency output by the laser 1, in this embodiment, the acousto-optic modulation device 2 is an optical fiber coupling type acousto-optic modulator, the frequency shift is not greater than 200MHz, the insertion loss is not greater than 5dB, the tail fiber is a polarization maintaining tail fiber, and the polarization extinction ratio is greater than 18dB.
The above-mentioned light-splitting device 3 splits the laser light output by the acousto-optic modulation device 2 into two beams, wherein one beam is used as a frequency stabilization optical signal to enter a post-stage optical path of the optical conduction device for frequency stabilization, and the other beam is used as the output light of the laser 1 for a user, in this embodiment, the light-splitting device 3 is an optical fiber light-splitting device, preferably a polarization maintaining optical fiber light-splitting device, the polarization extinction ratio is greater than 18dB, and the light-splitting ratio of the optical fiber light-splitting device is selected according to practical application requirements, which is not specifically required.
The phase modulation device 4 is used for performing phase modulation on the laser frequency, and generating two sideband frequency signals with a certain value different from the laser center frequency, in this embodiment, the phase modulation device 4 is an optical fiber coupling phase modulator, preferably a phase modulator made of optical fiber coupling type lithium niobate material, the modulation broadband of the optical fiber coupling phase modulator is not less than 100MHz, the insertion loss is less than 10dB, and the input and output tail fibers of the optical fiber coupling phase modulator are polarization maintaining tail fibers.
The above-mentioned transmission device 5 receives the laser light output by the phase modulation device 4, transmits the laser light to the optical fiber F-P cavity 6, and transmits the optical signal output by the optical fiber F-P cavity 6 to the control device, where in this embodiment, the transmission device 5 is an optical fiber circulator, and the optical fiber circulator has three ports, that is, the optical fiber circulator includes a first port, a second port and a third port, the first port is connected with the output end of the phase modulation device 4, the second port is connected with the input end of the optical fiber F-P cavity 6, the third port is connected with the control device, and performs transmission and output of the laser light, and the optical fiber circulator is a polarization-maintaining circulator, and the pigtail fiber is a polarization-maintaining pigtail fiber.
The optical fiber F-P cavity 6 is an F-P cavity formed by modifying or modifying an optical fiber waveguide structure based on an optical fiber, the F-P cavity can be obtained by modifying an optical fiber end face size structure or a substance structure, meanwhile, the optical fiber F-P cavity 6 can be not an open cavity, vacuum or other refractive index mediums of air can be filled in the cavity to improve the performance of the F-P cavity, the optical fiber F-P cavity 6 is small in size and full-optical fiber, so that the fineness and wavelength selection characteristics of the optical fiber F-P cavity are not influenced by external temperature and vibration sound through a certain package, a very stable reference cavity is formed, the optical fiber F-P cavity can be subjected to constant temperature and vibration isolation package, and the constant temperature vibration isolation package adopts vacuum cavity package and adopts a thermoelectric refrigerator to perform constant temperature control on the optical fiber F-P cavity 6. The fineness of the F-P cavity of the optical fiber is greater than 10000, the fineness is selected according to actual requirements, and different finesses can be selected according to different application occasions in actual application.
The laser 1, the acousto-optic modulation device 2, the light splitting device 3, the phase modulation device 4, the transmission device 5 and the optical fiber F-P cavity 6 are sequentially connected, and the laser 1, the acousto-optic modulation device 2, the light splitting device 3, the phase modulation device 4, the transmission device 5 and the optical fiber F-P cavity 6 are all optical fiber devices, so that the connection mode among the optical fiber devices is an optical fiber welding process, and the connection reliability and the polarization stability among the optical fiber devices are ensured.
The control device comprises a photoelectric detection device 7, a modulation module 8, a demodulation module 9, an acousto-optic adjustment module 11 and a PID control module 10, wherein the photoelectric detection device 7 is respectively connected with the transmission device 5 and the demodulation module 9, the photoelectric detection device 7 receives an optical signal output by the transmission device 5 and transmits the optical signal to the demodulation module 9, the modulation module 8 is respectively connected with the phase modulation device 4 and the demodulation module 9, the modulation module 8 outputs a radio frequency signal to the phase modulation device 4 to perform phase modulation on laser in an optical path, meanwhile, the modulation module 8 outputs an intrinsic reference signal to the demodulation module 9, the PID control module 10 is respectively connected with a demodulation circuit, the acousto-optic adjustment module 11 and the laser 1, the acousto-optic adjustment module 11 is connected with the acousto-optic adjustment device 2, the demodulation module 9 mixes and demodulates the photoelectric signal output by the photoelectric detection device 7 and the intrinsic reference signal output by the modulation module 8 to obtain a frequency drift error signal of the laser 1, the error signal is transmitted to the PID control module 10, the PID control module 10 amplifies and delays the amplitude of the error signal and feeds back the radio frequency signal to the laser 1 and the laser device 2, and the laser frequency of the laser 1 is modulated by the laser frequency modulator 1, and the laser frequency of the laser is modulated by the laser modulator 1.
The aforementioned acousto-optic modulation module 11 is an acousto-optic modulator driving circuit, and is used for driving the acousto-optic modulation device 2, and starting the acousto-optic modulation device 2, so that the laser can pass through the acousto-optic modulation device 2, and the acousto-optic modulation device 2 can modulate the frequency of the laser passing through the acousto-optic modulation device 2. The driving circuit of the acousto-optic modulator is in the prior art and is selected according to actual requirements.
The above-mentioned photo-detecting device 7 is configured to receive the optical signal of the laser beam output by the transmitting device 5, in this embodiment, the photo-detecting device 7 is a photo-detector, the output electrical signal interface of the photo-detector is AC coupling, and the photo-bandwidth of the photo-detector is greater than the radio frequency signal bandwidth of the phase modulating device 4 when working, and the photo-gain of the photo-detector is greater than 30dB.
The modulation module 8 is a modulation circuit, and is configured to output a radio frequency signal to the phase modulation device 4, so that the phase modulation device 4 performs phase modulation on the laser in the optical path, so that the frequency and the radio frequency power of the output radio frequency signal of the phase modulation device 4 can be adjusted, the radio frequency of the modulation circuit depends on the photoelectric bandwidth of the photoelectric detector, and the radio frequency power can be adjusted from 0 to 20 dBm. The modulation circuit is in the prior art and is selected according to actual requirements.
The demodulation module 9 is a demodulation circuit, and an analog frequency mixing demodulation function is built in the demodulation circuit, so that the photoelectric signal output by the photoelectric detection device 7 and the output intrinsic reference signal of the modulation module 8 can be mixed and demodulated to obtain a frequency drift error signal of the laser 1. The demodulation circuit is in the prior art and is selected according to actual requirements.
The PID control module 10 is a PID control circuit, and is configured to amplify and delay the amplitude and phase of the error signal output by the demodulation module 9, feed back the error signal to the laser 1 and the acoustic optical modulation device 2, control the current wavelength tuning unit inside the laser 1 and tune the frequency of the laser by the acoustic optical modulation device 2, and stabilize the frequency of the output laser of the laser 1. The PID control circuit is in the prior art and is selected according to actual requirements.
In the control device, when the photoelectric detection device 7, the modulation module 8, the demodulation module 9, the acousto-optic modulation module 11 and the PID control module 10 are connected, the signal line is connected by adopting a coaxial radio frequency line, and the power supply line is connected by adopting a wire.
Before the PDH frequency stabilization all-fiber laser system based on the fiber F-P cavity is used, all fiber devices and all circuit modules are firstly connected, the fiber devices in the optical conduction device are firstly connected, the laser 1, the acousto-optic modulation device 2, the beam splitting device 3, the phase modulation device 4, the transmission device 5 and the fiber F-P cavity 6 are connected through a fiber fusion process, then all circuit modules in the control device are connected, the photoelectric detection device 7 and the transmission device 5 are connected, the modulation module 8 is respectively connected with the phase modulation device 4 and the demodulation module 9, the demodulation module 9 is connected with the PID control module 10, the PID control module 10 is respectively connected with the acousto-optic adjustment module 11 and the laser 1, and the acousto-optic adjustment module 11 is connected with the acousto-optic modulation device 2;
the phase modulation device 4 receives the radio frequency signal output by the modulation module 8, the phase modulation device 4 carries out phase modulation on a beam of light split by the light splitting device 3, and two sideband frequency signals with a certain value different from the frequency of the beam of light are generated near the center frequency of the laser; the laser after phase modulation enters the optical fiber F-P cavity 6 through the first port and the second port of the optical fiber circulator, the laser entering the optical fiber F-P cavity 6 is reflected back and forth in the optical fiber F-P cavity 6 for many times, when the laser frequency is inconsistent with the laser frequency matched with the optical fiber F-P cavity 6, the laser is reflected by the concave cavity mirror and then reflected by the front cavity mirror, the part of laser with frequency jitter information is output through the second port and the third port of the optical fiber circulator, and the output photoelectric signal is detected by the photoelectric detection device 7;
the laser light output by the laser 1 will generate loss in the process of conduction in the light conduction device and the optical fiber F-P cavity 6, and the following is set: the output optical power of the laser 1 is P Lout (dBm) optical fiber acousto-optic modulator with on insertion loss IL AOM (dB) the insertion loss of the optical fiber beam splitter into the post-stage phase modulator end is IL OC (dB) the operating insertion loss of the fiber-coupled phase modulator is IL EOM (dB) the insertion loss of the first port to the second port of the fiber optic circulator is IL CIR12 (dB) the insertion loss from the second port to the third port is IL CIR23 (dB) the reflectivity of the fiber F-P cavity 6 is R cavity The responsivity of the photoelectric detector is eta λ (V/W), then the optical power ultimately entering the photodetector is: p (P) in_pd ＝P Lout -IL AOM -IL OC -IL EOM -IL CIR12 +10·log(1-R cavity ) (dBm) according to the types of the laser 1, the acousto-optic modulation device 2, the beam splitting device 3, the phase modulation device 4, the optical fiber circulator and the optical fiber F-P cavity 6, and by combining the above formulas, the optical power entering the photodetector can be calculated;
the photoelectric signal detected by the photoelectric detection device 7, the alternating current part of which is input into the demodulation module 9, the signal of the photoelectric detector is mixed with the modulated intrinsic signal given by the modulation module 8 and then is subjected to low-pass filtering, and a PDH error signal serving as a frequency discrimination signal is output; the error signal PDH serving as the frequency discrimination signal enters the PID control module 10 as a feedback signal, and the PID control module 10 continuously adjusts the driving signal of the laser 1 according to the deviation between the feedback information and the set value, thereby suppressing the external interference and stabilizing the laser frequency.
When the PDH frequency stabilization all-fiber laser 1 system based on the fiber F-P cavity 6 works, single-frequency laser output by the single-frequency narrow-linewidth laser 1 passes through an acousto-optic modulation device 2, an acousto-optic modulation module 11 receives signals transmitted by a PID control module 10 to drive the acousto-optic modulation device 2 to act, the acousto-optic modulation device 2 shifts the single-frequency laser in a certain range, the size of the frequency shift is determined by the size and polarity of an error signal provided by the PID control module 10, the output end of the acousto-optic modulation device 2 is connected with a light splitting device 3, one beam of light is split by the light splitting device 3 as final output light of the laser 1 for a user, the other beam of light enters a post-stage phase modulation device 4, and the phase modulation device 4 receives radio frequency signals output by a modulation module 8, so that the phase modulation device 4 modulates the beam of laser and generates two sideband frequency signals which are different from the single-frequency by a certain value near the center frequency of the laser; the modulated laser is injected into an optical fiber F-P cavity 6 through a transmission device 5, the optical fiber F-P cavity 6 has very high fineness and very low loss, and is used as a reference cavity, and standing waves can be formed in the cavity only when the laser frequency is matched with the resonant frequency of the cavity; the laser is reflected in the optical fiber F-P cavity 6 for multiple times, the laser reflected by the cavity enters the photoelectric detection device 7 from the second port to the third port of the transmission device 5, the photoelectric signal output by the photoelectric detection device 7 enters the demodulation module 9, and the photoelectric signal and the intrinsic signal output by the modulation module 8 to the driving signal of the phase modulation device 4 are mixed in the demodulation module 9, so that an error signal containing frequency detuning information is obtained;
the error signals are fed back to the wavelength tuning functional unit and the acoustic optical modulation device 2 inside the single-frequency narrow-linewidth laser 1 respectively through the PID control module 10, and the frequencies of the laser 1 are compensated in a low frequency mode and a high frequency mode respectively, so that the locking of the laser frequency to the reference cavity is achieved, and the stabilization of the output laser frequency of the laser 1 is achieved.
Example two
As shown in fig. 2, the difference between this embodiment and the first embodiment is that there is no acousto-optic modulation device 2 and no acousto-optic modulation module 11 between the laser 1 and the optical splitting device 3, the feedback signal of the pid control module 10 is transmitted to the laser 1, in this embodiment, the optical conduction device includes the optical splitting device 3, the phase modulation device 4 and the transmission device 5 which are sequentially connected, the optical splitting device 3 is connected to the laser 1, the transmission device 5 is connected to the optical fiber F-P cavity 6, the laser output by the laser 1 enters the optical splitting device 3, the optical splitting device 3 splits the laser into two beams, one beam of light is used as output, the other beam of light enters the phase modulation device 4, the phase modulation device 4 performs phase modulation on the beam of laser, the modulated laser enters the transmission device 5, enters the optical fiber F-P cavity 6 through the first port and the second port, the laser is reflected in the optical fiber F-P cavity multiple times, and the laser is output through the second port and the third port.
The control device comprises a photoelectric detection device 7, a modulation module 8, a demodulation module 9 and a PID control module 10, wherein the photoelectric detection device 7 is respectively connected with the transmission device 5 and the demodulation module 9, the modulation module 8 is respectively connected with the phase modulation device 4 and the demodulation module 9, the PID control module 10 is respectively connected with a demodulation circuit and the laser 1, the photoelectric detection device 7 receives an optical signal of laser output from the transmission device 5 and transmits the optical signal to the demodulation module 9, the modulation module 8 transmits a radio frequency signal to the phase modulation device 4, so that the phase modulation device 5 carries out phase modulation on the laser, and in the demodulation module 9, the optical signal output by the transmission device 5 and an intrinsic signal of a driving signal output by the modulation module 8 to the phase modulation device 4 are mixed in the demodulation module 9 to obtain an error signal containing frequency detuning information, and the error signal is fed back to the laser 1 through the PID control module 10 to realize current tuning control and voltage tuning control on the laser 1, so that the output laser frequency of the laser 1 is stabilized.
In this embodiment, the laser 1 may be a tunable narrow linewidth optical fiber external cavity laser 1, where the laser 1 is provided with a piezoelectric control device, and the piezoelectric control device is disposed on an external cavity of the laser 1, preferably, the piezoelectric control device is a piezoelectric actuator, so as to perform a large-scale adjustment on an output laser frequency of the laser 1, and simultaneously may perform a small-scale fine adjustment on the output laser frequency of the laser 1 through a laser driving current. The laser frequency error signal can control the piezoelectric actuator device on the external cavity to perform large-range low-speed coarse calibration on the output frequency of the laser 1, and can control the driving current of the laser 1 to perform high-speed small-range fine calibration on the laser output laser frequency, in the first embodiment, the high-speed small-range fine calibration function is completed by the optical fiber coupling acousto-optic modulator and the acousto-optic modulator driving circuit, in the case of the embodiment, the driving current of the laser 1 is controlled to perform high-speed small-range fine calibration on the laser output laser frequency to replace the functions of the optical fiber coupling acousto-optic modulator and the acousto-optic modulator driving circuit, the light coupling acousto-optic modulator in an optical fiber path can be removed, and the changed system optical path reduces the optical fiber coupling acousto-optic modulator and is simpler.
By adopting the technical scheme, the PDH frequency stabilization all-fiber laser system based on the fiber F-P cavity is provided with the fiber circuit and the electric signal circuit which are connected, and the fiber circuit modulates laser according to the feedback signal of the electric signal circuit to inhibit external interference so as to ensure that the laser frequency output by the laser is stable; the optical fiber line is provided with an optical fiber F-P cavity which is used as a reference cavity, has the same size as the optical fiber, has the size advantage compared with a space type optical device, has smaller volume, is easy to perform constant temperature vibration isolation packaging, and has smaller size compared with the space type optical device after packaging; the optical fiber circuit is connected with the laser, the optical fiber circuit is provided with an acousto-optic modulation device, a light splitting device, a phase modulation device and an optical fiber circulator which are sequentially connected, the acousto-optic modulation device, the light splitting device, the phase modulation device and the optical fiber circulator are all polarization maintaining optical fiber coupling devices, laser output by the laser enters the light splitting device after being modulated by the acousto-optic modulation device, the laser is split into two beams of light by the light splitting device, one beam of light is output, the other beam of light enters the phase modulation device, the beam of laser enters an optical fiber F-P cavity after being modulated by the phase, the laser is output by the optical fiber circulator after being reflected for many times, a photoelectric detection device in the electric signal circuit receives the output optical signal, the optical signal is mixed with an intrinsic signal of a driving signal output by the modulation circuit to the phase modulation device in the demodulation circuit, an error signal containing frequency detuning information is obtained, the error signal is fed back to the laser and the acousto-optic modulation device by the PID control circuit, the frequency of the laser is compensated in low frequency and high frequency, the PID control circuit continuously adjusts the driving signal of the laser according to deviation of the feedback information and a set value, and thus the interference frequency of the laser is stabilized; each optical fiber device is connected through an optical fiber fusion process or an optical fiber connector, the optical path is built and debugged simply, the connection reliability of an optical path system is improved, and the mode matching between a preceding optical path and an optical fiber F-P cavity is not required to be carried out through a complex mode conversion optical path, so that the laser system is compact in structure.
The foregoing describes the embodiments of the present invention in detail, but the description is only a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. All equivalent changes and modifications within the scope of the present invention are intended to be covered by the present invention.
Claims (10)
1. The PDH frequency stabilization all-fiber laser system based on the fiber F-P cavity is characterized in that: comprising the following steps:
a laser for laser output;
the light conduction device is connected with the laser, and is used for carrying out light splitting on laser output by the laser, outputting one path of light and modulating the other path of light;
the optical fiber F-P cavity is connected with the optical conduction device, and is used for carrying out multiple reflection on the light subjected to the modulation treatment of the other path and outputting the light;
and the control device is respectively connected with the optical conduction device and the laser, receives and processes the optical signals output by the optical fiber F-P cavity, outputs feedback signals, tunes the output laser frequency of the laser, and stabilizes the frequency of the laser output laser.
2. The optical fiber F-P cavity based PDH stabilized all-fiber laser system of claim 1, wherein: the optical conduction device comprises an optical splitting device, a phase modulation device and a transmission device which are sequentially connected, wherein the optical splitting device is connected with the laser to split laser of the laser into two beams, the phase modulation device carries out phase modulation on one path of optical phase after optical splitting, and modulated light enters the F-P cavity of the optical fiber through the signal transmission device.
3. The optical fiber F-P cavity based PDH stabilized all-fiber laser system of claim 2, wherein: the optical conduction device further comprises an acousto-optic modulation device, wherein the acousto-optic modulation device is respectively connected with the laser and the light splitting device, and frequency adjustment is carried out on output laser of the laser.
4. A PDH frequency stabilized all-fiber laser system based on an optical fiber F-P cavity as claimed in claim 2 or 3, wherein: the light splitting device is an optical fiber light splitter, and the polarization extinction ratio of the optical fiber light splitter is greater than 18dB;
the phase modulation device is an optical fiber coupling phase modulator, the modulation broadband of the optical fiber coupling phase modulator is not less than 100MHz, and the insertion loss is less than 10dB;
the transmission device is an optical fiber circulator, and the fineness of the F-P cavity of the optical fiber is more than 10000.
5. The optical fiber F-P cavity based PDH stabilized all-fiber laser system of claim 2, wherein: the control device comprises a photoelectric detection device, a modulation module, a demodulation module and a PID control module, wherein,
the photoelectric detection device is respectively connected with the transmission device and the demodulation module, receives the optical signals output by the transmission device and transmits the optical signals to the demodulation module;
the modulation module is respectively connected with the phase modulation device and the demodulation module, and outputs a radio frequency signal to the phase modulation device so that the phase modulation device carries out phase modulation on laser;
the demodulation module carries out frequency mixing demodulation processing on the intrinsic signal output by the modulation module and the photoelectric signal output by the photoelectric detection device to obtain a drift error signal of the laser;
the PID control module is respectively connected with the demodulation circuit and the laser, processes the error signal and controls the laser to act to tune the output laser frequency.
6. The optical fiber F-P cavity based PDH stabilized all-fiber laser system of claim 5, wherein: the laser is a single-frequency narrow linewidth laser and is provided with a piezoelectric control device.
7. A PDH frequency stabilized all-fiber laser system based on fiber F-P cavity as defined in claim 3, wherein: the control device comprises a photoelectric detection device, a modulation module, a demodulation module, an acousto-optic adjustment module and a PID control module, wherein,
the photoelectric detection device is respectively connected with the transmission device and the demodulation module, receives the optical signals output by the transmission device and transmits the optical signals to the demodulation module;
the modulation module is respectively connected with the phase modulation device and the demodulation module, and outputs a radio frequency signal to the phase modulation device so that the phase modulation device carries out phase modulation on laser;
the demodulation module carries out frequency mixing demodulation processing on the intrinsic signal output by the modulation module and the photoelectric signal output by the photoelectric detection device to obtain a drift error signal of the laser;
the PID control module is respectively connected with the demodulation circuit, the acousto-optic adjustment module and the laser, processes the error signal, controls the laser to act to tune the output laser frequency, controls the acousto-optic adjustment module to drive the acousto-optic adjustment device to act, and adjusts the output laser frequency of the laser.
8. The fiber F-P cavity based PDH stabilized all-fiber laser system of any one of claims 5-7, wherein: the photoelectric detection device is a photoelectric detector, and the bandwidth of the photoelectric detector is larger than the bandwidth of the radio frequency signal of the phase modulation device;
the modulation module is a modulation circuit, and the frequency and the radio frequency power of an output radio frequency signal of the modulation circuit are adjustable;
the demodulation module is a demodulation circuit, and the PID control module is a PID control circuit.
9. The optical fiber F-P cavity based PDH stabilized all-fiber laser system of claim 1, wherein: the optical fiber F-P cavity is a constant temperature vibration isolation package.
10. The fiber F-P cavity based PDH stabilized all-fiber laser system of claim 7, wherein: the acousto-optic modulation module is an acousto-optic modulator driving circuit.
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