An all-fiber laser frequency stability transfer system

Abstract

The application discloses a kind of all-fiber laser frequency stability transfer system, including main laser, slave laser, acoustooptic modulator, coupler, fiber delay line, temperature controller, PZT, Faraday mirror, optical add-drop multiplexer, optical filter, photoelectric detector, radio frequency frequency synthesizer, frequency discrimination signal generator, servo feedback circuit;Frequency stability of main laser is transferred to fiber interferometer by feedback control to fiber delay line, which is composed of coupler, fiber delay line and Faraday mirror, then the frequency of slave laser is locked on fiber interferometer, and then laser frequency stability transfer is realized.The application only needs a stable main laser, can use the method, obtain multiple slave lasers with the same stability, and the system has the advantages of low cost, simple structure, high stability and the like, and has wide application prospect in the field of quantum precision measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser frequency stabilization, in particular to a kind of all-fiber laser frequency stability transfer system. BACKGROUND

[0002] Laser frequency stabilization technology is an important part of atomic optical frequency standard.The commonly used methods of laser frequency stabilization include: atomic frequency stabilization, which locks the laser frequency on the atomic or molecular spectral line, and the frequency range of the laser is limited by the atomic or molecular transition spectrum;Cavity frequency stabilization: using PDH method to stabilize the laser frequency on the cavity length of Fabry-Perot cavity, which can stabilize the laser frequency away from the atomic or molecular resonance frequency;Interferometer frequency stabilization: using unequal arm interferometer to extract frequency fluctuation signal, and compensating the frequency of the laser to improve the frequency stability of the laser.

[0003] In the method of fiber interferometer frequency stabilization, the fiber interferometer converts the laser frequency fluctuation into a laser interference signal output, and the frequency stability of the laser is locked on the fiber interferometer.Due to the limitation of the stability of the fiber interferometer caused by environmental temperature and other factors, the patent [application publication number: 202110334941.9] proposes an ultra-stable laser system based on polarization maintaining fiber.Due to the different responses of the fast and slow axes of the polarization maintaining fiber to temperature, and the linear relationship between the optical path difference output by the fast and slow axes of the polarization maintaining fiber interferometer and temperature, the output signal can be used for feedback control of the laser to compensate the influence of temperature on the stability of the fiber interferometer and improve the performance of laser frequency stabilization.The method has the advantages of low cost, simple structure and high signal stability, but it can only be used for the stabilization of one laser, and cannot realize the frequency transfer function of multiple lasers.The other laser frequency stabilization and transfer methods such as optical frequency comb transfer and optical transfer cavity transfer have complex structure and poor stability, which is not conducive to miniaturization and integration. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and proposes an all-fiber laser frequency stability transfer system, which can simultaneously compensate for the changes in optical path caused by the different lengths of the interferometer arms and the thermal-optic effect through the combination of temperature controller and PZT control, and realize the locking of the interferometer on the frequency of the main laser.The frequency of other slave lasers is re-locked on the stabilized fiber interferometer, thereby realizing the transfer of the frequency stability of the main laser to the slave lasers.The system uses all-fiber structure and has the advantages of low cost, simple structure and high stability.

[0005] The technical scheme of the present application is as follows:

[0006] An all-fiber laser frequency stability transfer system, characterized in that, comprising a slave laser group, a first acousto-optic modulator group, a first coupler group, a master laser, a second coupler group, a third coupler, a first Faraday mirror, a temperature controller, a TEC, a fiber delay line, a second acousto-optic modulator, a second Faraday mirror, an optical add-drop multiplexer group, a first optical filter, a second optical filter group, a first photodetector, a second photodetector group, a frequency discrimination signal generator, a first servo feedback controller, a frequency synthesizer, a second servo feedback controller;

[0007] The output light of the slave laser group passes through the first acousto-optic modulator group and is divided into two beams by the first coupler group, one of which is directly output, and the other of which is combined with the output laser of the master laser after passing through the second coupler group, and then is divided into two paths by the third coupler, one of which returns to the third coupler after being reflected by the first Faraday mirror, and the other of which returns to the third coupler after passing through the temperature controller, TEC, fiber delay line and second acousto-optic modulator and being reflected by the second Faraday mirror, the two paths of light form interference through the third coupler, and the interference laser signal is separated by the optical add-drop multiplexer group according to wavelength, and the interference signals of the master laser and the slave laser group are output respectively;

[0008] The interference signal of the master laser passes through the first optical filter and is converted into a master laser detection signal by the first photodetector, mixes with the radio frequency signal output by the frequency synthesizer in the frequency discrimination signal generator to obtain a master laser frequency discrimination signal, and enters the first servo feedback controller to generate a temperature control signal and a PZT control signal, wherein the temperature control signal controls the temperature controller to raise or lower the temperature of the fiber delay line covered by the temperature controller, thereby changing the refractive index and length of the long arm of the fiber interferometer in which the fiber delay line is located, the optical path difference of the fiber interferometer is thus changed, which in turn causes the interference signal of the 132th output to change, forming a closed-loop feedback control to lock the fiber interferometer to the frequency of the master laser, and the PZT control signal controls the piezoelectric ceramic PZT, which also forms a closed-loop feedback control to lock the fiber interferometer to the master laser;

[0009] The interference signal of the slave laser group is converted into a slave laser detection signal by the second photodetector group after passing through the second filter group, and mixed with the radio frequency signal emitted by the frequency synthesizer in the frequency discriminator signal generator to obtain a slave laser frequency discriminator signal, which enters the second servo feedback controller group to generate a slow frequency feedback signal and a fast frequency feedback signal, wherein the slow frequency feedback signal controls the frequency slow modulation of the feedback mechanism of the slave laser group, and the fast frequency feedback signal controls the fast modulation of the first acousto-optic modulator group, thereby changing the laser frequency of the slave laser group and locking the slave laser group to the fiber interferometer, and the stability of the fiber interferometer follows the frequency stability of the master laser, that is, the frequency stability of the master laser to the slave laser group is transferred.

[0010] The feedback control of the fiber interferometer locks the fiber interferometer to the frequency of the master laser, and then uses the fiber interferometer as a reference to realize the frequency stability of multiple slave lasers and the transfer of the frequency stability of the master laser to the slave lasers.

[0011] The fiber interferometer is an unequal-arm interferometer, and the detection of the frequency discriminator signal is heterodyne detection.

[0012] The fiber interferometer is an unequal-arm Michelson fiber interferometer.

[0013] The master laser beam and the slave laser beam are distinguished by an optical add-drop multiplexer group, a filter and / or a polarization beam splitter: if the fiber delay line uses a non-polarization-maintaining fiber, an optical add-drop multiplexer group is used for frequency discrimination; if the fiber delay line uses a polarization-maintaining fiber, a polarization beam splitter is used for frequency discrimination.

[0014] Optionally, the fiber interferometer is an unequal-arm interferometer, and the detection of the frequency discriminator signal is heterodyne detection.

[0015] Optionally, the master laser beam and the slave laser beam are distinguished by an optical add-drop multiplexer group, a filter and a polarization beam splitter: if the fiber delay line uses a non-polarization-maintaining fiber, an optical add-drop multiplexer group is used for frequency discrimination; if the fiber delay line uses a polarization-maintaining fiber, a polarization beam splitter is used for frequency discrimination.

[0016] Optionally, the fiber interferometer is an unequal-arm Michelson fiber interferometer.

[0017] Optionally, the detection of the frequency discriminator signal of the fiber interferometer uses homodyne detection.

[0018] Compared with the prior art, the present application has the following advantages:

[0019] 1) The present method uses all-fiber links, which can more conveniently increase the length of the fiber delay line to improve the precision of the frequency discrimination signal, thereby improving the transfer precision of the laser frequency stability;

[0020] 2) The present application changes the state of the long arm of the fiber interferometer in real time through the temperature controller and the PZT, dynamically following the frequency stability of the master laser; and uses a temperature feedback and PZT combined control method to compensate for the arm length change and the thermal light effect of the long arm of the interferometer, which reduces the sensitivity to environmental temperature fluctuations compared with the method using only the PZT, and improves the performance of the laser frequency stability transfer system;

[0021] 3) The broadband fiber devices are used to combine different frequency lasers, and the optical wavelength division multiplexer is used to separate the lasers according to the wavelength, so that the frequency transfer function can be realized on one set of system, and the frequency locking of multiple slave lasers can be realized;

[0022] 4) The fiber interferometer composed of the fiber delay line and the other components described above is used to replace the transfer cavity or the optical comb to perform frequency stability transfer. The frequency stabilization performance of this method is comparable to that of the cavity transfer and the optical comb frequency locking, and it does not require a high-precision optical cavity and a complex optical comb frequency acquisition system. The fiber interferometer has a simple structure and is easy to miniaturize. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram of a specific embodiment of the all-fiber laser frequency stability transfer system of the present application DETAILED DESCRIPTION

[0024] The specific embodiments of the present application will be further described in detail below with reference to the accompanying drawings. The following examples are used to illustrate the present application, but are not intended to limit the scope of the present application. The specific structures and functional details disclosed herein are only used to describe the example embodiments of the present application. However, the present application can be embodied in many alternative forms, and should not be understood as being limited in the embodiments set forth herein.

[0025] It should be understood that although the terms first, second, etc. can be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another unit. For example, a first unit can be called a second unit, and similarly a second unit can be called a first unit, without departing from the scope of the example embodiments of the present application.

[0026] EMBODIMENT

[0027] Figure 1The application discloses an all-fiber laser frequency stability transmission system, which comprises a slave laser group 1, a first acousto-optic modulator group 2, a first coupler group 3, a main laser 4, a second coupler group 5, a third coupler 6, a first Faraday mirror 7, a temperature controller 8, a TEC 9, a fiber delay line 10, a second acousto-optic modulator 11, a second Faraday mirror 12, an optical add-drop multiplexer group 13, a first optical filter 14, a second optical filter group 15, a first photoelectric detector 16, a second photoelectric detector group 17, a frequency discrimination signal generator 18, a first servo feedback controller 19, a frequency synthesizer 20 and a second servo feedback controller group 21.

[0028] The slave laser of the slave laser group 1 outputs a wavelength of 1112 nm, sequentially passes through the first acousto-optic modulator group 2, enters the 31 port of the first coupler group 3, the 32 port of the first coupler group 3 outputs a slave laser as the output of the slave laser 1, and the 33 port outputs a slave laser to enter the 52 port of the beam combiner 5. The main laser of the 1064 nm main laser 4 exits and enters the 51 port of the second coupler group 5, the second coupler group 5 combines the main laser and the slave laser, and then outputs the combined laser from the 55 port to enter the 61 port of the third coupler 6; the combined laser is divided into two paths by the third coupler, one path is output from the 63 port, passes through the first Faraday mirror, and returns to the 63 port of the third coupler in the original path; one path is output from the 64 port, passes through the temperature controller, the TEC, the fiber delay line and the second acousto-optic modulator, is reflected by the second Faraday mirror, and returns to the 64 port of the third coupler in the original path. The 1112 nm slave laser returned to the 63 port interferes with the 1112 nm slave laser returned to the 64 port to obtain a 1112 nm slave interference signal; the 1064 nm main laser returned to the 63 port interferes with the 1064 nm main laser returned to the 64 port to obtain a 1064 nm main interference signal; the interference lasers of different wavelengths are separated according to wavelengths by the optical add-drop multiplexer group: the 1064 nm main laser is output from the 132 port; and the 1112 nm slave laser is output from the 133 port.

[0029] The 1064 nm main interference signal is output from the 132 port, passes through the 1064 nm optical filter 14, enters the first photoelectric converter 16, is converted into a main laser detection signal with a frequency of The main laser detection signal enters the frequency discrimination signal generator 18, and is compared with the f AOMThe signal beat frequency obtains a main laser frequency discrimination signal, the main laser frequency discrimination signal is connected to the 191 end of the first servo feedback controller 19, the 192 end generates a temperature control signal to control the temperature controller 8, and the 193 end generates a PZT control signal to control the PZT 9; the temperature controller 8 locks the stability of the fiber interferometer on the 1064nm main laser 4 by changing the length and refractive index of the long arm of the fiber interferometer.

[0030] 1112nm slave interference signal is output from the 133 end, passes through the 1112nm filter 15, enters the second photoelectric converter 17 to be converted into a 1112nm slave laser detection signal with a frequency of The 1112nm slave laser detection signal is beat with the f AOM Signal to obtain a slave laser frequency discrimination signal, and enters the second servo feedback controller group 21 to generate a slow feedback signal and a fast feedback signal for laser frequency stabilization; the slow feedback signal controls the 1112nm slave laser 1, and the fast feedback signal enters the first acousto-optic modulator group 2 to be frequency modulated, and finally outputs the 1112nm ultra-stable laser.

[0031] In a specific application, for example, the main laser frequency discrimination signal controls the temperature controller through the first servo feedback controller 19, so as to change the stability of the optical path difference of the fiber interferometer, and lock the fiber interferometer with the 1064nm main laser 4. Therefore, the interferometer stability follows the 1064nm main laser 4. The slave laser frequency discrimination signal enters the second servo feedback controller group 21, and controls the first acousto-optic modulator group 2 and the 1112nm slave laser 1 through the generated feedback signal to stabilize the slave laser.

[0032] In summary, the all-fiber laser frequency stability transfer system provided by the embodiment has the following technical effects:

[0033] 1) The method uses an all-fiber link, and the length of the fiber delay line can be more conveniently increased to improve the precision of the frequency discrimination signal, so that the laser frequency stability transfer precision is improved;

[0034] 2) The temperature controller and the PZT are used to change the state of the long arm of the fiber interferometer in real time, and the frequency stability of the main laser is dynamically followed; and the temperature feedback and PZT combined control method is used to compensate the arm length change and thermal light effect of the long arm of the interferometer, compared with the method of using only the PZT, the sensitivity to environmental temperature fluctuations is reduced, and the performance of the laser frequency stability transfer system is improved;

[0035] 3) Using the fiber device with wide bandwidth to combine different frequency lasers, and using the optical wavelength division multiplexer to separate the lasers according to the wavelength, the frequency transfer function can be realized on a set of system, and the frequency locking of multiple slave lasers can be realized;

[0036] 4) Using the fiber interferometer composed of the fiber delay line and other components to replace the transfer cavity or the optical comb to perform the frequency stability transfer. The frequency stabilization performance of this method is equivalent to the cavity transfer and the optical comb frequency locking, and it does not need high-precision optical cavity and complex optical comb frequency acquisition system. The fiber interferometer has simple structure and is easy to miniaturize.

Claims

1. An all-fiber laser frequency stability transfer system, characterized by, The slave laser group (1) includes a first acousto-optic modulator group (2), a first coupler group (3), a main laser (4), a second coupler group (5), a third coupler (6), a first Faraday mirror (7), a temperature controller (8), a piezoelectric ceramic PZT (9), a fiber delay line (10), a second acousto-optic modulator (11), a second Faraday mirror (12), an optical add-drop multiplexer group (13), a first optical filter (14), a second optical filter group (15), a first photodetector (16), a second photodetector group (17), a frequency discriminator signal generator (18), a first servo feedback controller (19), a frequency synthesizer (20), and a second servo feedback controller (21). The output light of the slave laser group (1) is divided into two beams by the first acousto-optic modulator group (2) and the first coupler group (3), one of which is directly output, and the other of which is combined with the output light of the main laser (4) through the second coupler group (5), and then divided into two paths by the third coupler (6), one of which is reflected by the first Faraday mirror (7) and returned to the third coupler (6), and the other of which is reflected by the second Faraday mirror (12) after passing through the temperature controller (8), the piezoelectric ceramic PZT (9), the fiber delay line (10), and the second acousto-optic modulator (11), and returned to the third coupler (6), the two paths of light form interference through the third coupler (6), and the interference light signal is separated by the optical add-drop multiplexer group (13) according to wavelength, and the interference signals of the main laser (4) and the slave laser group (1) are output respectively. The interference signal of the main laser (4) is converted into a main laser detection signal by the first photodetector (16) after passing through the first optical filter (14), and is mixed with the radio frequency signal output by the frequency synthesizer (20) in the frequency discriminator signal generator (18) to obtain a main laser frequency discrimination signal, which enters the first servo feedback controller (19) to generate a temperature control signal and a PZT control signal, wherein the temperature control signal controls the temperature controller (8) to raise or lower the temperature of the fiber delay line (10) covered by the temperature controller (8), thereby changing the refractive index and length of the long arm of the fiber interferometer, the optical path difference of the fiber interferometer is changed, and the output of the interference signal of the main laser interferometer output port of the optical add-drop multiplexer group is changed, forming a closed-loop feedback control, and the fiber interferometer is locked to the frequency of the main laser, and the PZT control signal controls the piezoelectric ceramic PZT (9), which is also controlled by a closed-loop feedback control to lock the fiber interferometer to the main laser. The interference signal of the slave laser group (1) is converted into a slave laser detection signal by the second photodetector group (17) after passing through the second filter group (15), and the slave laser detection signal is mixed with the radio frequency signal emitted by the frequency synthesizer (20) in the frequency discriminator (18) to obtain a slave laser frequency discriminator signal, which enters the second servo feedback controller group (21) to generate a slow frequency feedback signal and a fast frequency feedback signal. The slow frequency feedback signal controls the frequency slow modulation of the feedback mechanism of the slave laser group (1), and the fast frequency feedback signal controls the fast modulation of the first acousto-optic modulator group (2), thereby changing the laser frequency of the slave laser group (1) and locking the slave laser group (1) to the fiber interferometer. The stability of the fiber interferometer follows the frequency stability of the master laser (4), that is, the frequency stability of the master laser (4) to the slave laser group (1) is transferred. The fiber interferometer is controlled by feedback to lock the fiber interferometer to the frequency of the master laser, and the fiber interferometer is used as a reference to achieve the frequency stability of multiple slave lasers and the transfer of the frequency stability of the master laser to the slave lasers.

2. An all-fiber laser frequency stability transfer system according to claim 1, wherein, The fiber interferometer is a non-equal-arm interferometer, and the detection of the frequency discriminator signal is heterodyne detection.

3. An all-fiber laser frequency stability transfer system as claimed in claim 2, characterized in that, The fiber interferometer is a non-equal-arm Michelson fiber interferometer.

4. An all-fiber laser frequency stability transfer system as claimed in claim 1, characterized in that, The master laser beam and the slave laser beam are distinguished by an optical add-drop multiplexer group, a filter and / or a polarization beam splitter: if the fiber delay line uses a non-polarization-maintaining fiber, an optical add-drop multiplexer group is used for frequency discrimination; if the fiber delay line uses a polarization-maintaining fiber, a polarization beam splitter is used for frequency discrimination.

Images