Method, system and device for improving locking bandwidth and control range of optical frequency comb

Abstract

The present application discloses a method, system and device for improving the locking bandwidth and control range of an optical frequency comb. ceo Error signal and repetition frequency f r The error signal controls the voltage of the double electro-optical crystal electrodes to achieve f ceo and f r The locking bandwidth is improved, and the temperature of the control wave plate is increased. ceo The control range is to control the voltage of the piezoelectric ceramic PZT to increase f r The control range of the optical frequency comb is reduced. This avoids the problem of optical frequency comb spectrum changes and difficulty in maintaining mode locking caused by large-range control, and improves the long-term stability of the system. ceo and f r , repeat the above steps until the error signal is lower than the threshold. Using dual electro-optical crystals, a four-way control method with two locking loops is reasonably arranged, and can be performed simultaneously, which improves the locking bandwidth and increases the control range.

Description

Technical Field

[0001] The present application relates to the technical field of frequency control of optical frequency combs, and in particular to a method, system and device for improving the locking bandwidth and control range of optical frequency combs. Background Art

[0002] An optical frequency comb is an optical frequency measurement conversion tool that uses a mode-locked laser to generate ultrashort optical pulses. It can measure unknown frequencies or stabilize the laser to a specific frequency. Its characteristic is that the time intervals between adjacent pulse waves are exactly the same. It can be said that an optical frequency comb is like a ruler or timer with a precise scale. The optical frequency comb can be obtained from the carrier envelope phase shift frequency (f ceo ) and repetition frequency (f r ) Two degrees of freedom are used to accurately lock the bandwidth and control range.

[0003] In existing optical frequency comb systems, there is often f ceo 、f r The problem of insufficient locking loop bandwidth or insufficient control range affects the core indicators and long-term reliability of the optical frequency comb system, such as phase noise and stability, making it difficult for the system to operate continuously and normally, thus affecting the application of optical frequency combs. ceo 、f r Locking with high bandwidth and large control range has become an urgent problem to be solved. Summary of the invention

[0004] Based on the above problems, the present application provides a method, system and device for improving the locking bandwidth and control range of an optical frequency comb to achieve f ceo 、f r Locking with high bandwidth and large control range.

[0005] The present application discloses a method for improving the locking bandwidth and control range of an optical frequency comb, the method comprising:

[0006] Get the carrier-envelope phase shift frequency f in the optical frequency comb ceo Error signal and repetition frequency f r Error signal; the f ceo The error signal is given by f ceo The electrical signal is compared with the radio frequency reference signal; the f r The error signal is given by f r The electrical signal is compared with the radio frequency reference signal;

[0007] Using the f ceo The error signal controls the voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis to increase f ceo The locking bandwidth is controlled by controlling the temperature of the wave plate to increase f ceoScope of control;

[0008] Based on the changed f ceo , repeatedly obtain and based on f ceo Error signal to f ceo Change until f ceo The error signal is below the threshold;

[0009] At the same time, using the f r The error signal controls the voltage of the two electrodes of the EOM cut along the Y axis to increase the f r The locking bandwidth is increased by controlling the voltage of the piezoelectric ceramic PZT to increase f r Scope of control;

[0010] Based on the changed f r , repeatedly obtain and based on f r Error signal to f r Change until f r The error signal is below the threshold.

[0011] Optionally, the carrier envelope phase shift frequency f in the optical frequency comb is obtained. ceo Error signals, including:

[0012] Get f in the optical frequency comb ceo Generate an optical signal output by the module;

[0013] The optical signal is converted into the f ceo The electrical signal is input into a bandpass amplifier;

[0014] The bandpass amplifier is used to ceo The electrical signal is filtered and amplified to obtain f ceo Amplify the signal;

[0015] The f ceo The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison;

[0016] The phase detector outputs the comparison result to the low-pass filter to obtain f ceo Error signal.

[0017] Optional, get f r Error signals, including:

[0018] The photodetector will r The relevant optical signal is converted into the f r electric signal;

[0019] The f r The electrical signal is input into the bandpass amplifier for filtering and amplification to obtain f rAmplify the signal;

[0020] The f r The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison;

[0021] The phase detector outputs the comparison result to the low-pass filter to obtain f r Error signal.

[0022] Optional,

[0023] When the optical frequency comb is locked to a radio frequency reference, the r The relevant optical signal is f r Optical pulse signal;

[0024] When the optical frequency comb is locked to an optical frequency reference, the r The relevant optical signal is a beat frequency signal of the optical frequency comb and the radio frequency reference signal.

[0025] Optionally, the f ceo The error signal is divided into a first signal and a second signal. r The error signal is divided into a third signal and a fourth signal.

[0026] Optionally, the voltage of two electrodes of the electro-optic modulator EOM cut along the Z axis is controlled to increase f ceo The locked bandwidth includes:

[0027] The first signal controls the voltage of two electrodes on the Y axis of the EOM cut along the Z axis through the PI controller, changes the polarization state of the light transmitted by the EOM, changes the intracavity power of the optical frequency comb, and thus changes f ceo The locked bandwidth.

[0028] Optionally, the temperature of the wave plate is controlled to increase f ceo The scope of control includes:

[0029] The second signal controls the set temperature value of the temperature control module through the PI controller; the temperature control module corresponds to the temperature of the wave plate;

[0030] The temperature control module controls the temperature of the wave plate, changes the phase delay of the wave plate, and thus changes f ceo range of control.

[0031] Optionally, the voltage of the two electrodes of the EOM cut along the Y axis is controlled to increase f r The locked bandwidth includes:

[0032] The third signal controls the voltage of two electrodes on the Z axis of the EOM cut along the Y axis through the PI controller, changes the refractive index of the EOM cut along the Y axis, changes the intracavity optical path of the optical frequency comb, and thus changes f r The locked bandwidth.

[0033] Optionally, the voltage of the piezoelectric ceramic PZT is controlled to increase f r The scope of control includes:

[0034] The fourth signal controls the voltage applied to the PZT through the PI controller, changes the expansion and contraction of the PZT, changes the cavity length of the optical frequency comb, and thus changes f r range of control.

[0035] Optionally, the EOM is a lithium niobate crystal.

[0036] Based on the above method for improving the locking bandwidth and control range of an optical frequency comb, the present application also discloses a system for improving the locking bandwidth and control range of an optical frequency comb, which is used to implement the above method for improving the locking bandwidth and control range of an optical frequency comb, and the system comprises:

[0037] EOM cut along the Z axis, EOM cut along the Y axis, wave plate and PZT;

[0038] The EOM cut along the Z axis is used according to f ceo The error signal increases f ceo The locked bandwidth;

[0039] The EOM cut along the Y axis is used according to f r The error signal increases f r The locked bandwidth;

[0040] The wave plate is used according to f ceo The error signal increases f ceo Scope of control;

[0041] The PZT is used according to f r The error signal increases f r range of control.

[0042] Optionally, also include:

[0043] A polarization beam splitter is used to isolate the EOM cut along the Z axis and the EOM cut along the Y axis.

[0044] Optionally, also include:

[0045] PI controller is used to realize f ceo and f r Automatic control.

[0046] Based on the above method for improving the locking bandwidth and control range of an optical frequency comb, the present application also discloses a device for improving the locking bandwidth and control range of an optical frequency comb, characterized in that, for the above method, the device comprises: an error signal acquisition unit, a first control unit, a first locking unit, a second control unit and a second locking unit;

[0047] The error signal acquisition unit is used to acquire the carrier envelope phase shift frequency f in the optical frequency comb. ceo Error signal and repetition frequency f r Error signal; the f ceo The error signal is given by f ceo The electrical signal is compared with the radio frequency reference signal; the f r The error signal is given by f r The electrical signal is compared with the radio frequency reference signal;

[0048] The first control unit is used to utilize the f ceo The error signal controls the voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis to increase f ceo The locking bandwidth is controlled by controlling the temperature of the wave plate to increase f ceo Scope of control;

[0049] The first locking unit is used to lock the ceo , repeatedly obtain and based on f ceo Error signal to f ceo Change until f ceo The error signal is below the threshold;

[0050] The second control unit is used to simultaneously use the f r The error signal controls the voltage of the two electrodes of the EOM cut along the Y axis to increase the f r The locking bandwidth is increased by controlling the voltage of the piezoelectric ceramic PZT to increase f r Scope of control;

[0051] The second locking unit is used to lock the r , repeatedly obtain and based on f r Error signal to f r Change until f r The error signal is below the threshold.

[0052] Optionally, the error signal acquisition unit includes:

[0053] The first acquisition subunit is used to obtain f in the optical frequency comb. ceo Generate an optical signal output by the module;

[0054] The first conversion subunit is used to convert the optical signal into the f ceo The electrical signal is input into a bandpass amplifier;

[0055] The first amplifying subunit is used for the bandpass amplifier to ceo The electrical signal is filtered and amplified to obtain f ceo Amplify the signal;

[0056] The first comparison subunit is used to compare the f ceo The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison;

[0057] The first output subunit is used for the phase detector to output the comparison result to the low-pass filter to obtain f ceo Error signal.

[0058] Optionally, the error signal acquisition unit includes:

[0059] The second acquisition subunit is used to detect the r The relevant optical signal is converted into the f r electric signal;

[0060] The second amplifying subunit is used to convert the f r The electrical signal is input into the bandpass amplifier for filtering and amplification to obtain f r Amplify the signal;

[0061] The second comparison subunit is used to compare the f r The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison;

[0062] The second output subunit is used for the phase detector to output the comparison result to the low-pass filter to obtain f r Error signal.

[0063] Optionally, when the optical frequency comb is locked to a radio frequency reference, the r The relevant optical signal is f r Optical pulse signal;

[0064] When the optical frequency comb is locked to an optical frequency reference, the r The relevant optical signal is a beat frequency signal of the optical frequency comb and the radio frequency reference signal.

[0065] Optionally, the f ceo The error signal is divided into a first signal and a second signal. r The error signal is divided into a third signal and a fourth signal.

[0066] Optionally, the first control unit includes:

[0067] The first processing subunit is used for controlling the voltage of two electrodes on the Y axis of the EOM cut along the Z axis through the PI controller, changing the polarization state of the light transmitted by the EOM, changing the intracavity power of the optical frequency comb, and thus changing f ceo The locked bandwidth.

[0068] Optionally, the first control unit includes:

[0069] A second processing subunit, configured to control the set temperature value of a temperature control module through a PI controller with the second signal; the temperature control module corresponds to the temperature of the wave plate;

[0070] The temperature control module is also used to control the temperature of the wave plate, change the phase delay of the wave plate, and thus change f ceo range of control.

[0071] Optionally, the second control unit includes:

[0072] The third processing subunit is used for the third signal to control the voltage of two electrodes on the Z axis of the EOM cut along the Y axis through the PI controller, so as to change the refractive index of the EOM cut along the Y axis, so as to change the intracavity optical path of the optical frequency comb, thereby changing f r The locked bandwidth.

[0073] Optionally, the second control unit includes:

[0074] The fourth processing subunit is used for the fourth signal to control the voltage applied to the PZT through the PI controller, change the expansion and contraction amount of the PZT, change the cavity length of the optical frequency comb, and thus change f r range of control.

[0075] Optionally, the EOM is a lithium niobate crystal.

[0076] The present application discloses a method, system and device for improving the locking bandwidth and control range of an optical frequency comb. Obtaining the carrier envelope phase shift frequency f in an optical frequency comb ceo Error signal and repetition frequency f r Error signal. Using f ceo The error signal controls the voltage increase of the two electrodes of the electro-optic modulator EOM cut along the Z axis. ceo The locking bandwidth is increased by controlling the temperature of the wave plate. ceo The control range of r Error signal, controlling the voltage increase of the two electrodes of the EOM cut along the Y axis rThe locking bandwidth is improved by controlling the voltage of the piezoelectric ceramic PZT. r Based on the changed f ceo and f r , repeatedly obtain the error signal for processing until the error signal is lower than the threshold. The present application adopts a dual electro-optical crystal and a four-way control method with two locking loops arranged reasonably, which can be performed simultaneously, thereby increasing the locking bandwidth and the control range. Among them, the control range is increased by controlling the operating temperature of the wave plate, which avoids the problem of optical frequency comb spectrum changes and difficulty in maintaining locked mode caused by large-range control, and improves the long-term stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0078] Figure 1 A flow chart of a method for improving the locking bandwidth and control range of an optical frequency comb disclosed in an embodiment of the present application;

[0079] Figure 2 A flow chart of another method for improving the locking bandwidth and control range of an optical frequency comb disclosed in an embodiment of the present application;

[0080] Figure 3 A schematic diagram of the structure of a system for improving the locking bandwidth and control range of an optical frequency comb disclosed in an embodiment of the present application. DETAILED DESCRIPTION

[0081] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0082] Embodiment 1: This application discloses a method for improving the locking bandwidth and control range of an optical frequency comb.

[0083] For details, please refer to Figure 1 , a method for improving the locking bandwidth and control range of an optical frequency comb disclosed in this embodiment includes the following steps:

[0084] Step 101: Obtain the carrier-envelope phase shift frequency f in the optical frequency comb ceoError signal and repetition frequency f r Error signal.

[0085] In the method described in this embodiment, it is first necessary to obtain ultrashort pulse light. Specifically, a "9" cavity mode-locked laser based on a nonlinear amplifying ring mirror can be used to form an ultrashort pulse light output with a central wavelength of 1550nm and a 3dB spectrum width of 50nm. The ultrashort pulse light is then divided into three paths, one of which is used to communicate with f r The other input is to f ceo Signal generation module to generate f ceo The final optical signal is used as the output of the optical comb system.

[0086] In the method described in this embodiment, f ceo The error signal is given by f ceo The electrical signal is compared with the RF reference signal, f r The error signal is given by f r The electrical signal is compared with the RF reference signal.

[0087] Among them, f ceo The error signal can be obtained by obtaining f in the optical frequency comb. ceo The optical signal generated by the module is converted into f ceo The electrical signal is input into the bandpass amplifier. Through the filtering effect of the bandpass amplifier, f ceo The required RF signal is extracted from the electrical signal and then amplified to obtain f ceo Amplify the signal. ceo The amplified signal and the RF reference signal are input into the phase detector for comparison. The RF reference signal can be preset according to actual needs, and the specific value of the RF reference signal is not limited here. After that, the phase detector outputs the comparison result to the low-pass filter for filtering, and only the low-frequency signal, i.e., f ceo Error signal.

[0088] Accordingly, f r The error signal can be obtained by using a photodetector to r The relevant optical signal is converted into f r When the optical frequency comb is locked to the RF reference, it is related to f r The relevant optical signal is f r When the optical frequency comb is locked to the optical frequency reference, it is r The relevant optical signal is the beat frequency signal of the optical frequency comb and the RF reference signal. r The electrical signal is input into the bandpass amplifier for filtering and amplification to obtain f r Amplify the signal. Then fr The amplified signal and the RF reference signal are input into the phase detector for comparison. Finally, the phase detector outputs the comparison result to the low-pass filter to obtain f r Error signal.

[0089] Step 102: Using the f ceo The error signal controls the voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis to increase f ceo The locking bandwidth is controlled by controlling the temperature of the wave plate to increase f ceo range of control.

[0090] In the method described in this embodiment, as an optional method, f ceo The error signal is divided into the first signal and the second signal. r The error signal is divided into a third signal and a fourth signal.

[0091] Among them, the first signal controls the voltage of the two electrodes on the Y axis of the EOM cut along the Z axis (abbreviated as Z-cut-EOM) through the PI controller, changes the polarization state of the EOM transmitted light, and makes part of the transmitted light be reflected out of the cavity of the optical frequency comb, thereby changing the intracavity power of the optical frequency comb, thereby changing f ceo The locking bandwidth of . Among them, the PI controller can realize automatic and fast control of this step. In order to distinguish, the PI controller that processes the first signal is called a fast PI controller.

[0092] The experimental verification results show that the Z-cut-EOM can achieve f ceo The locked bandwidth can reach more than 500kHz, and the locked dynamic range (control range) can reach more than 5MHz, meeting the requirements of f ceo High bandwidth locking requirement.

[0093] The second signal passes through the PI controller to control the set temperature value of the temperature control module. The temperature control module corresponds to the temperature of the wave plate. The temperature control module controls the temperature of the wave plate, changes the phase delay of the wave plate, and thus changes f ceo The control range of this step can be achieved through the PI controller. Since its control time is shorter than that of the fast PI controller, the PI controller that processes the second signal can be called a slow PI controller for distinction.

[0094] In the method described in this embodiment, the heat conduction method between the temperature control module and the wave plate can be contact heat conduction, or air heat conduction or other methods. The heat conduction method between the temperature control module and the wave plate is not specifically limited here, and the temperature control module can control the temperature of the wave plate. The temperature control range can be ±2°C, and the dynamic range is 200MHz.

[0095] The experimental verification results show that this method can achieve a locking bandwidth of the order of Hz and a dynamic range of several hundred MHz, which meets the requirements of f ceo Requests for widespread lockdown.

[0096] In the method described in this embodiment, the EOM may be a lithium niobate crystal or a crystal of other materials. The specific material of the EOM is not limited here, and it only needs to be able to implement the method described in this embodiment.

[0097] Step 103: Based on the changed f ceo , repeatedly obtain and based on f ceo Error signal to f ceo Change until f ceo The error signal is below the threshold.

[0098] In the method described in this embodiment, the changed f ceo The output is sent to the photodetector in step 101, and steps 101 and 102 are repeated until f ceo The error signal is lower than the threshold, i.e., f is locked. ceo bandwidth and range.

[0099] Step 104: Simultaneously utilize the f r The error signal controls the voltage of the two electrodes of the EOM cut along the Y axis to increase the f r The locking bandwidth is increased by controlling the voltage of the piezoelectric ceramic PZT to increase f r range of control.

[0100] In the method described in this embodiment, the third signal controls the voltage of the two electrodes on the Z axis of the EOM cut along the Y axis (referred to as Y-cut-EOM) through the PI controller. At this time, changing the voltage in the Z axis direction will not change the polarization state of the light, but due to the electro-optical effect, it will change the refractive index of the EOM cut along the Y axis, so that the optical path in the cavity of the optical frequency comb changes, thereby changing f r The locking bandwidth is 1.5. At this time, the light transmission direction of the Y-cut-EOM is its Y axis, and the Z surface is gold-plated for applying voltage. Among them, the PI controller can realize automatic and fast control of this step. In order to distinguish, the PI controller that processes the third signal is called a fast PI controller.

[0101] The experimental verification results show that the Y-cut-EOM can achieve f r The locked bandwidth can reach more than 600kHz, and the locked dynamic range can reach more than 10Hz, which meets the requirements of f r High bandwidth locking requirement.

[0102] The fourth signal passes through the PI controller to control the voltage applied to the PZT, changing the expansion and contraction of the PZT, changing the cavity length of the optical frequency comb, and thus changing f r The control range of this step can be achieved through the PI controller. For the sake of distinction, the PI controller that processes the fourth signal can be called a slow PI controller because its control time is shorter than that of a fast PI controller.

[0103] The experimental verification results show that the control range of this method depends on the extension stroke of PZT and f r The PZT applied voltage range can be 0-100V, the maximum elongation is 20μm, and the repetition frequency change is 4kHz. For example, for an optical frequency comb with a repetition frequency of 200MHz, a PZT with a stroke of 20μm can achieve a control frequency range of ±2kHz. Its control is affected by the response time of the PZT, which is generally around 5kHz.

[0104] Step 105: Based on the changed f r , repeatedly obtain and based on f r Error signal to f r Change until f r The error signal is below the threshold.

[0105] In the method described in this embodiment, the changed f r The output is sent to the photodetector in step 101, and steps 101 and 104 are repeated until f r The error signal is lower than the threshold, i.e., f is locked. r bandwidth and range.

[0106] In the method described in this embodiment, steps 102, 103 and steps 104, 105 can be performed simultaneously, that is, ceo and f r The processing of f can be performed simultaneously. ceo The processing and f r The order of processing is specifically limited.

[0107] The method described in this embodiment adopts dual EOM, two locking loops and four control methods to achieve simultaneous control of f ceo and f r The locking bandwidth and control range are improved. The coupling between the two locking loops is reduced, and the control range is increased while the locking bandwidth is increased, which ultimately improves the core indicators such as phase noise and stability, and ensures the long-term stability of the system. The method of increasing the control range of the wave plate operating temperature is also adopted to avoid the problem of optical frequency comb spectrum changes and difficulty in maintaining mode locking caused by large-range control, thereby improving the long-term stability of the system.

[0108] Embodiment 2: This application discloses another method for improving the locking bandwidth and control range of an optical frequency comb. Figure 2 The method described in this embodiment introduces the whole process of improving the locking bandwidth and control range of the optical frequency comb.

[0109] Step 201: Based on the radio frequency reference signal and the current moment f ceo and the current moment f r , get the current time f ceo The error signal and the current f r Error signal.

[0110] Step 202: Set the current f ceo The error signal controls the Z-cut-EOM and temperature control module through the PI controller, and obtains the f at the next moment. ceo .

[0111] Step 203: Based on the RF reference signal and the next moment f ceo Get the next moment f ceo error signal, and determine the next moment f ceo Is the error signal less than the threshold? If yes, proceed to step 204. If no, proceed to step 205.

[0112] Step 204: Output f ceo .

[0113] Step 205: Set the next moment f ceo As the current moment f ceo . Repeat step 202.

[0114] Step 206: Set the current f r The error signal controls the Y-cut-EOM and PZT via the PI controller, and obtains the f at the next moment. r .

[0115] Step 207: Based on the RF reference signal and the next moment f r Get the next moment f r error signal, and determine the next moment f r Is the error signal less than the threshold? If yes, proceed to step 208. If no, proceed to step 209.

[0116] Step 208: Output f r .

[0117] Step 209: Set the next moment f r As the current moment f r . Repeat step 206.

[0118] Based on the method for improving the locking bandwidth and control range of an optical frequency comb disclosed in the above embodiment, this embodiment correspondingly discloses a system for improving the locking bandwidth and control range of an optical frequency comb, which is used to implement the above method for improving the locking bandwidth and control range of an optical frequency comb. The system for improving the locking bandwidth and control range of an optical frequency comb includes: an EOM cut along the Z axis, an EOM cut along the Y axis, a wave plate, and a PZT;

[0119] The EOM cut along the Z axis is used according to f ceo The error signal increases f ceo The locked bandwidth;

[0120] The EOM cut along the Y axis is used according to f r The error signal increases f r The locked bandwidth;

[0121] The wave plate is used according to f ceo The error signal increases f ceo Scope of control;

[0122] The PZT is used according to f r The error signal increases f r range of control.

[0123] Optionally, also include:

[0124] A polarization beam splitter is used to isolate the EOM cut along the Z axis and the EOM cut along the Y axis.

[0125] Optionally, also include:

[0126] PI controller is used to realize f ceo and f r Automatic control.

[0127] In the system described in this embodiment, Figure 3 Schematic diagram of the structure of a system for improving the locking bandwidth and control range of an optical frequency comb disclosed in an embodiment of the present application, such as Figure 3 As shown on the left, the rectangular box is a black box, which contains the optical frequency comb optical system. The optical frequency comb optical system includes two mirrors and a cavity formed between the two mirrors. The cavity also includes a Y-cut-EOM, a Z-cut-EOM, a wave plate, a PZT, a temperature control module, a polarization beam splitter PBS and an f ceo Generate module.

[0128] like Figure 3 As shown on the right, f ceo By ceoThe RF reference signal is also input to the phase detector 2 through the photodetector 2 and the bandpass amplifier 2. The phase detector 2 compares the result to obtain the f through the low-pass filter 2. ceo One of the error signals is input to the fast PI controller 2. The fast PI controller 2 is based on f ceo The error signal controls the Z-cut-EOM in the optical frequency comb optical system. ceo The other input of the error signal is to the slow PI controller 2, which is based on f ceo The error signal controls the temperature control module, that is, controls the wave plate, and finally obtains the changed f ceo After the change, f ceo By ceo The generation module is re-output to the photodetector 2, thereby f ceo The bandwidth and range of the RF signal are locked to approximately the same level as the RF reference signal.

[0129] Accordingly, f r The optical frequency comb optical system, i.e. the black box, sends the signal to the photodetector 1, and then passes through the bandpass amplifier 1 to the phase detector 1. At the same time, the RF reference signal is also input to the phase detector 1, and the phase detector 1 compares the result to obtain f through the low-pass filter 1. r One of the error signals is input to the fast PI controller 1. The fast PI controller 1 is based on f r The error signal controls the Y-cut-EOM in the optical frequency comb optical system. r The other input of the error signal is to the slow PI controller 1, which is based on f r The error signal controls the PZT, and finally the changed f is obtained. r After the change, f r The black box outputs the photodetector 1 again, thus converting f r The bandwidth and range of the RF signal are locked to approximately the same level as the RF reference signal.

[0130] Based on the above method for improving the locking bandwidth and control range of an optical frequency comb, the present application also discloses a device for improving the locking bandwidth and control range of an optical frequency comb, characterized in that, for the above method, the device comprises: an error signal acquisition unit, a first control unit, a first locking unit, a second control unit and a second locking unit;

[0131] The error signal acquisition unit is used to acquire the carrier envelope phase shift frequency f in the optical frequency comb. ceo Error signal and repetition frequency f r Error signal; the f ceo The error signal is given by f ceoThe electrical signal is compared with the radio frequency reference signal; the f r The error signal is given by f r The electrical signal is compared with the radio frequency reference signal;

[0132] The first control unit is used to utilize the f ceo The error signal controls the voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis to increase f ceo The locking bandwidth is controlled by controlling the temperature of the wave plate to increase f ceo Scope of control;

[0133] The first locking unit is used to lock the ceo , repeatedly obtain and based on f ceo Error signal to f ceo Change until f ceo The error signal is below the threshold;

[0134] The second control unit is used to simultaneously use the f r The error signal controls the voltage of the two electrodes of the EOM cut along the Y axis to increase the f r The locking bandwidth is increased by controlling the voltage of the piezoelectric ceramic PZT to increase f r Scope of control;

[0135] The second locking unit is used to lock the r , repeatedly obtain and based on f r Error signal to f r Change until f r The error signal is below the threshold.

[0136] Optionally, the error signal acquisition unit includes:

[0137] The first acquisition subunit is used to obtain f in the optical frequency comb. ceo Generate an optical signal output by the module;

[0138] The first conversion subunit is used to convert the optical signal into the f ceo The electrical signal is input into a bandpass amplifier;

[0139] The first amplifying subunit is used for the bandpass amplifier to ceo The electrical signal is filtered and amplified to obtain f ceo Amplify the signal;

[0140] The first comparison subunit is used to compare the f ceo The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison;

[0141] The first output subunit is used for the phase detector to output the comparison result to the low-pass filter to obtain f ceo Error signal.

[0142] Optionally, the error signal acquisition unit includes:

[0143] The second acquisition subunit is used to detect the r The relevant optical signal is converted into the f r electric signal;

[0144] The second amplifying subunit is used to convert the f r The electrical signal is input into the bandpass amplifier for filtering and amplification to obtain f r Amplify the signal;

[0145] The second comparison subunit is used to compare the f r The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison;

[0146] The second output subunit is used for the phase detector to output the comparison result to the low-pass filter to obtain f r Error signal.

[0147] Optionally, when the optical frequency comb is locked to a radio frequency reference, the r The relevant optical signal is f r Optical pulse signal;

[0148] When the optical frequency comb is locked to an optical frequency reference, the r The relevant optical signal is a beat frequency signal of the optical frequency comb and the radio frequency reference signal.

[0149] Optionally, the f ceo The error signal is divided into a first signal and a second signal. r The error signal is divided into a third signal and a fourth signal.

[0150] Optionally, the first control unit includes:

[0151] The first processing subunit is used for controlling the voltage of two electrodes on the Y axis of the EOM cut along the Z axis through the PI controller, changing the polarization state of the light transmitted by the EOM, changing the intracavity power of the optical frequency comb, and thus changing f ceo The locked bandwidth.

[0152] Optionally, the first control unit includes:

[0153] A second processing subunit, configured to control the set temperature value of a temperature control module through a PI controller with the second signal; the temperature control module corresponds to the temperature of the wave plate;

[0154] The temperature control module is also used to control the temperature of the wave plate, change the phase delay of the wave plate, and thus change f ceo range of control.

[0155] Optionally, the second control unit includes:

[0156] The third processing subunit is used for the third signal to control the voltage of two electrodes on the Z axis of the EOM cut along the Y axis through the PI controller, so as to change the refractive index of the EOM cut along the Y axis, so as to change the intracavity optical path of the optical frequency comb, thereby changing f r The locked bandwidth.

[0157] Optionally, the second control unit includes:

[0158] The fourth processing subunit is used for the fourth signal to control the voltage applied to the PZT through the PI controller, change the expansion and contraction amount of the PZT, change the cavity length of the optical frequency comb, and thus change f r range of control.

[0159] Optionally, the EOM is a lithium niobate crystal.

[0160] The embodiments in this specification are described in a progressive manner. As for the devices disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the methods.

[0161] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0162] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0163] The features described in the embodiments of this specification can be replaced or combined with each other, so that professional and technical personnel in this field can implement or use the present application.

[0164] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving the locking bandwidth and control range of an optical frequency comb, characterized in that: include: Get the carrier-envelope phase shift frequency f in the optical frequency comb ceo Error signal and repetition frequency f r Error signal; the f ceo The error signal is given by f ceo The electrical signal is compared with the radio frequency reference signal; the f r The error signal is given by f r The electrical signal is compared with the radio frequency reference signal; Using the f ceo The error signal controls the voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis to increase f ceo The locking bandwidth is controlled by controlling the temperature of the wave plate to increase f ceo Scope of control; Based on the changed f ceo , repeatedly obtain and based on f ceo Error signal to f ceo Change until f ceo The error signal is below the threshold; At the same time, using the f r The error signal controls the voltage of the two electrodes of the EOM cut along the Y axis to increase the f r The locking bandwidth is increased by controlling the voltage of the piezoelectric ceramic PZT to increase f r Scope of control; Based on the changed f r , repeatedly obtain and based on f r Error signal to f r Change until f r The error signal is below the threshold.

2. The method according to claim 1, characterized in that The carrier-envelope phase shift frequency f in the optical frequency comb is obtained. ceo Error signals, including: Get f in the optical frequency comb ceo Generate an optical signal output by the module; The optical signal is converted into the f ceo The electrical signal is input into a bandpass amplifier; The bandpass amplifier is used to ceo The electrical signal is filtered and amplified to obtain f ceo Amplify the signal; The f ceo The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison; The phase detector outputs the comparison result to the low-pass filter to obtain f ceo Error signal.

3. The method according to claim 1, characterized in that Get f r Error signals, including: The photodetector will r The relevant optical signal is converted into the f r electric signal; The f r The electrical signal is input into the bandpass amplifier for filtering and amplification to obtain f r Amplify the signal; The f r The amplified signal and the preset radio frequency reference signal are input into the phase detector for comparison; The phase detector outputs the comparison result to the low-pass filter to obtain f r Error signal.

4. The method according to claim 3, characterized in that When the optical frequency comb is locked to a radio frequency reference, the r The relevant optical signal is f r Optical pulse signal; When the optical frequency comb is locked to an optical frequency reference, the r The relevant optical signal is a beat frequency signal of the optical frequency comb and the radio frequency reference signal.

5. The method according to claim 1, characterized in that The f ceo The error signal is divided into a first signal and a second signal. r The error signal is divided into a third signal and a fourth signal.

6. The method according to claim 5, characterized in that The voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis is controlled to increase the f ceo The locked bandwidth includes: The first signal controls the voltage of two electrodes on the Y axis of the EOM cut along the Z axis through the PI controller, changes the polarization state of the light transmitted by the EOM, changes the intracavity power of the optical frequency comb, and thus changes f ceo The locked bandwidth.

7. The method according to claim 5, characterized in that The temperature of the wave plate is controlled to increase the f ceo The scope of control includes: The second signal controls the set temperature value of the temperature control module through the PI controller; the temperature control module corresponds to the temperature of the wave plate; The temperature control module controls the temperature of the wave plate, changes the phase delay of the wave plate, and thus changes f ceo range of control.

8. The method according to claim 5, characterized in that The voltage of the two electrodes of the EOM cut along the Y axis is controlled to increase the f r The locked bandwidth includes: The third signal controls the voltage of two electrodes on the Z axis of the EOM cut along the Y axis through the PI controller, changes the refractive index of the EOM cut along the Y axis, changes the intracavity optical path of the optical frequency comb, and thus changes f r The locked bandwidth.

9. The method according to claim 5, characterized in that The voltage of the piezoelectric ceramic PZT is controlled to increase the f r The scope of control includes: The fourth signal controls the voltage applied to the PZT through the PI controller, changes the expansion and contraction of the PZT, changes the cavity length of the optical frequency comb, and thus changes f r range of control.

10. The method according to any one of claims 1 to 9, characterized in that: The EOM is a lithium niobate crystal.

11. A system for improving the locking bandwidth and control range of an optical frequency comb, characterized in that: For implementing the method according to any one of claims 1 to 10, the system comprises: an EOM cut along the Z axis, an EOM cut along the Y axis, a wave plate and a PZT; The EOM cut along the Z axis is used according to f ceo The error signal increases f ceo The locked bandwidth; The EOM cut along the Y axis is used according to f r The error signal increases f r The locked bandwidth; The wave plate is used according to f ceo The error signal increases f ceo Scope of control; The PZT is used according to f r The error signal increases f r range of control.

12. The system according to claim 11, characterized in that Also includes: A polarization beam splitter is used to isolate the EOM cut along the Z axis and the EOM cut along the Y axis.

13. The system according to claim 11, characterized in that Also includes: PI controller is used to realize f ceo and f r Automatic control.

14. A device for improving the locking bandwidth and control range of an optical frequency comb, characterized in that: Used to implement the method according to any one of claims 1 to 10, the device comprises: an error signal acquisition unit, a first control unit, a first locking unit, a second control unit and a second locking unit; The error signal acquisition unit is used to acquire the carrier envelope phase shift frequency f in the optical frequency comb. ceo Error signal and repetition frequency f r Error signal; the f ceo The error signal is given by f ceo The electrical signal is compared with the radio frequency reference signal; the f r The error signal is given by f r The electrical signal is compared with the radio frequency reference signal; The first control unit is used to utilize the f ceo The error signal controls the voltage of the two electrodes of the electro-optic modulator EOM cut along the Z axis to increase f ceo The locking bandwidth is controlled by controlling the temperature of the wave plate to increase f ceo Scope of control; The first locking unit is used to lock the ceo , repeatedly obtain and based on f ceo Error signal to f ceo Change until f ceo The error signal is below the threshold; The second control unit is used to simultaneously use the f r The error signal controls the voltage of the two electrodes of the EOM cut along the Y axis to increase the f r The locking bandwidth is increased by controlling the voltage of the piezoelectric ceramic PZT to increase f r Scope of control; The second locking unit is used to lock the r , repeatedly obtain and based on f r Error signal to f r Change until f r The error signal is below the threshold.

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