CN109270825B - Dual-wavelength good-bad cavity active optical clock based on secondary cavity locking technology and implementation method thereof - Google Patents
Dual-wavelength good-bad cavity active optical clock based on secondary cavity locking technology and implementation method thereof Download PDFInfo
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- CN109270825B CN109270825B CN201811188592.9A CN201811188592A CN109270825B CN 109270825 B CN109270825 B CN 109270825B CN 201811188592 A CN201811188592 A CN 201811188592A CN 109270825 B CN109270825 B CN 109270825B
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- G—PHYSICS
- G04—HOROLOGY
- G04F—TIME-INTERVAL MEASURING
- G04F5/00—Apparatus for producing preselected time intervals for use as timing standards
- G04F5/14—Apparatus for producing preselected time intervals for use as timing standards using atomic clocks
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
- H01S3/13—Stabilisation of laser output parameters, e.g. frequency or amplitude
- H01S3/136—Stabilisation of laser output parameters, e.g. frequency or amplitude by controlling devices placed within the cavity
Abstract
The invention discloses a dual-wavelength good-bad cavity active optical clock based on a secondary cavity locking technology and an implementation method thereof. The invention provides a scheme for eliminating the influence of residual cavity traction effect on the long-term stability of an active optical frequency standard by utilizing the cavity traction inhibition effect of bad cavity laser in a dual-wavelength good-bad cavity laser system twice based on a secondary cavity locking technology, which amplifies the cavity traction inhibition effect to be square times of the main resonant cavity bad cavity coefficient, locks the cavity length of the main resonant cavity twice through a servo feedback system and achieves the effect of jitter immunity of the active optical frequency standard on a cavity mode in the dual-wavelength good-bad cavity system.
Description
Technical Field
The invention belongs to the technical field of atomic clocks and frequency standards, and particularly relates to a dual-wavelength active optical clock based on a secondary cavity locking technology and an implementation method thereof.
Background
The precise time frequency standard, namely the atomic clock, has important application in the fields of precise measurement, information network time synchronization, international standard time coordination, global navigation positioning system and the like, so that the atomic clock is always one of the key research directions in the field of measurement. Particularly, in the last decade, the optical frequency metering field has been developed rapidly, the performance of the optical frequency atomic clock exceeds that of the microwave atomic clock, and the stability and the accuracy of the optical frequency atomic clock (optical clock) realized by adopting the optical lattice and single ion trapping technology reach 10
-18In order of magnitude, there is a lower uncertainty than the cesium atomic fountain clocks currently used to define seconds, with the potential to redefine seconds instead of microwave atomic clocks. Especially, the development of optical combs and optical fibers has greatly promoted the application of optical frequency standards (optical frequency standards) that can precisely transfer the precision of optical frequencies to the microwave band, thereby realizing recording and display.
Although the existing optical frequency atomic clock has made great progress, all are based on passive working principle, the frequency of the local oscillator laser is locked on the atomic reference frequency through the electronic servo loop. The Pound-Drever-hall (pdh) frequency stabilization system used in a passive optical clock has a complex structure, wherein frequency drift (frequency drift) caused by the cavity length jitter of a high-fineness fabry-perot resonant cavity is difficult to further suppress, the frequency stability of a frequency-locked laser system is finally limited by cavity length thermal noise caused by brownian motion, and in order to suppress the frequency drift, some super cavities need to work in an extremely low-temperature environment, and the narrowing of the optical frequency scale to the millihertz order still faces huge challenges.
In order to break through the limitation of the traditional passive optical frequency standard, the new concept and principle of the active optical frequency standard are firstly proposed in 2005 by Beijing university: a novel optical frequency standard of multi-atom coherent stimulated radiation is formed between atom transition energy levels through weak feedback of an optical resonant cavity, the optical frequency standard with ultra-narrow line width can be realized, and the limitation of a traditional optical frequency atomic clock in the aspect of an ultra-stable resonant cavity is broken through. Because the clock transition signal is directly output by using the stimulated radiation of the quantum reference system, the laser frequency does not need to be passively locked to the quantum reference, the output laser has the immunity characteristic to the cavity length noise, the frequency stability is determined by atoms, the linewidth can be far smaller than the linewidth of the output laser of the traditional laser to reach the millihertz magnitude, simultaneously, the influence of the cavity traction effect can be greatly reduced, the influence of the external environment on the stability of the output laser is reduced, and the technical bottleneck of the traditional optical clock is broken through. The high-performance active optical frequency standard can be used as an independent laser frequency standard, can also be transmitted by an optical comb or a Fabry-Perot cavity, and provides narrow linewidth laser light sources with different frequency bands for other precision measurements, so that the development of the field of optical frequency precision measurement is promoted.
The four-level active optical clock realized by adopting thermal atoms at present has proved that the cavity traction effect can be effectively inhibited, and further the influence of the cavity length thermal noise on the output laser frequency is reduced, but because the cavity length of the active optical clock resonant cavity (main resonant cavity) is not locked, the cavity length is greatly influenced by external noise, the output bad cavity laser is still limited by the influence of the residual cavity traction effect, the output laser linewidth can not be further narrowed, the output laser cannot be used as an optical frequency standard, and the advantages of the active optical clock are not fully exerted.
Disclosure of Invention
In order to overcome the influence of the residual cavity pulling effect of the four-level active optical clock on the output optical frequency standard, the active optical frequency standard with quantum limit line width and jitter immunity of output frequency to cavity length is realized at normal temperature, and the stability of the cavity length of the main resonant cavity needs to be ensured. Firstly, good-cavity laser in a main resonant cavity is simultaneously output (refer to a paper that 'ten years and future prospects are sent by an active optical frequency standard'), wherein the good-cavity laser is divided into two paths, one path is combined with a PDH frequency stabilization technology of the existing passive optical clock local oscillator laser, so that the cavity length of the main resonant cavity is preliminarily stabilized on an ultra-stable optical resonant cavity (ultra-cavity), namely, the good-cavity laser frequency drift is consistent with the ultra-cavity, and on the basis, the bad-cavity laser frequency drift is reduced by two orders of magnitude compared with the good-cavity laser with PDH frequency stabilization by utilizing the cavity traction inhibition effect of the bad-cavity laser; then, the bad cavity laser is used as an ultra-narrow line width laser source, the repetition frequency of an optical frequency comb (optical comb) is locked on the bad cavity laser, and the frequency drift of the optical comb repetition frequency is consistent with the bad cavity laser; next, locking the other path of the good cavity laser on the comb teeth of the optical comb corresponding to the laser wavelength of the good cavity through beat frequency, so that the frequency drift of the good cavity laser is consistent with the frequency drift of the repetition frequency of the optical comb, namely consistent with the bad cavity laser; finally, the cavity length of the main resonant cavity is secondarily stabilized by the good-cavity laser in the previous step, namely the cavity length of the main resonant cavity is locked on the narrow-line narrow-width bad-cavity laser source, the cavity traction inhibiting effect of the bad-cavity laser is utilized again, so that the frequency drift of the output bad-cavity laser is reduced by two orders of magnitude, the influence of the residual cavity traction effect of the main resonant cavity on the active optical frequency standard is reduced or even eliminated, and the active optical frequency standard with the millihertz order quantum limit line width and excellent long-term stability is realized at normal temperature; the invention provides a scheme for eliminating the influence of residual cavity traction effect on the long-term stability of an active optical frequency standard by utilizing the cavity traction inhibition effect of bad cavity laser in a dual-wavelength good-bad cavity laser system twice based on a secondary cavity locking technology, which amplifies the cavity traction inhibition effect to be square times of the main resonant cavity bad cavity coefficient, locks the cavity length of the main resonant cavity twice through a servo feedback system and achieves the effect of jitter immunity of the active optical frequency standard on a cavity mode in the dual-wavelength good-bad cavity system.
The technical scheme of the invention is as follows:
a double-wavelength good-bad cavity active optical clock based on a secondary lock cavity technology is characterized by comprising a double-wavelength good-bad cavity system, a first dichroic mirror 17 and a second dichroic mirror 18, wherein double-wavelength good-bad cavity laser output by the double-wavelength good-bad cavity system is separated into good-cavity laser and bad-cavity laser through the second dichroic mirror 18 after being guided out by the first dichroic mirror 17; the good cavity laser passes through the second half-wave plate 19, the second polarization beam splitter prism 20, the phase modulator 21, the third polarization beam splitter prism 22 and the quarter-wave plate 23 in sequence and then is coupled into the reference cavity 24, the reflected signal of the reference cavity 24 passes through the quarter-wave plate 23 and the third polarization beam splitter prism 22 in sequence and then is input to the first photodetector 25, the output end of the first photodetector 25 is connected to an input end of the first mixer 27, the first signal generator 26 is respectively connected to the phase modulator 21 and the first mixer 27 to provide a driving signal for the phase modulator 21 and a reference signal for the first mixer 27, the first mixer 27 performs mixing phase-sensitive demodulation on the signal input by the first photodetector 25 and the reference signal to obtain a frequency discrimination signal, and feeds the frequency discrimination signal back to the piezoelectric ceramic plate 6 of the main resonant cavity of the dual-wavelength good-and-bad cavity system through the second servo feedback circuit 28.
Further, the dual-wavelength good-bad cavity system comprises a main resonant cavity, a first laser 1 and a second laser 10, wherein the first laser 1 and the second laser 10 are used for pumping a good-bad cavity gain medium in the main resonant cavity, laser output by the second laser 10 is divided into a strong beam and a weak beam sequentially through an isolator 12, a first half-wave plate 13 and a first polarization beam splitter prism 14, one beam with the weaker beam is input into a modulation transfer spectrum frequency stabilization module 15 to perform modulation transfer spectrum frequency stabilization to obtain a modulation transfer spectrum signal, the modulation transfer spectrum signal is fed back to the second laser 10 through a first servo feedback circuit 16 to stabilize the frequency of the second laser 10, and one beam with the stronger beam as bad cavity laser is input into the main resonant cavity through a first dichroic mirror 17 and is used for pumping the bad cavity gain medium to output the bad cavity laser; the main resonant cavity comprises main resonant cavity mirrors, a good cavity laser gain medium 7 and a bad cavity laser gain medium which are arranged between the main resonant cavity mirrors, and a piezoelectric ceramic piece 6 is arranged on the main resonant cavity mirror.
Furthermore, the dual-wavelength good-bad cavity system also comprises a magnetic shielding box 9, and the main resonant cavity is positioned in the magnetic shielding box 9; the bad cavity laser gain medium is positioned in the alkali metal atom gas chamber 8; the main resonant cavity mirror comprises a plane mirror 4 and a plane concave mirror 5, and a piezoelectric ceramic piece 6 is arranged on the plane mirror 4.
Further, the cavity laser light separated by the second dichroic mirror 18 passes through the fourth polarization splitting prism 29 and is divided into two beams, one beam is output as cavity laser light, and the other beam passes through the second photodetector 30 to convert an optical signal into an electrical signal and input into the fast fourier transform spectrum analyzer 31.
Further, the device also comprises an ultrastable femtosecond optical frequency comb 32, and the zero frequency f of the ultrastable femtosecond optical frequency comb 32
ceoThe signal is locked on a frequency reference provided by a microwave atomic clock; the ultrastable femtosecond optical frequency comb 32 outputs a repetition frequency f
kLight of (a) and a repetition frequency of f
gOf repetition frequency f
kThe same or similar to the laser frequency of the bad cavity, the repetition frequency f
gThe frequency of the laser is the same as or similar to that of the good cavity laser; repetition frequency f
kThe light and the bad cavity laser are respectively input into a fifth polarization beam splitter prism 34 to obtain a beat frequency signal f
b(ii) a Will signal f
bThe converted signal is input into a first phase-locked loop 37 through a third photoelectric detector 35, the first phase-locked loop 37 is connected with a second signal generator 36 and is used for receiving a radio frequency standard signal input by the second signal generator 36, and an error signal output by the first phase-locked loop 37 stabilizes the repetition frequency of the ultrastable femtosecond optical frequency comb 32 through a third servo feedback circuit 38; repetition frequency f
gThe light and the good cavity laser output by the second polarization splitting prism 20 are respectively input into a sixth polarization splitting prism 39 to obtain a beat frequency signal f
b’Will signal f
b’The converted signal is input to a second phase-locked loop 42 through a fourth photodetector 40, the second phase-locked loop 42 is connected to a third signal generator 41, and is configured to receive the radio frequency standard signal input by the third signal generator 41, and an error signal output by the second phase-locked loop 42 adjusts the cavity length of the main resonant cavity through a fourth servo feedback circuit 43.
A method for realizing a dual-wavelength good-bad cavity active optical clock based on a secondary cavity locking technology comprises the following steps:
1) separating the dual-wavelength good-and-bad cavity laser output by the dual-wavelength good-and-bad cavity system at the same time, and respectively outputting good-cavity laser and bad-cavity laser;
2) dividing good cavity laser into two paths, wherein one path is combined with a PDH frequency stabilization technology of a passive optical clock local oscillator laser, so that the cavity length of a main resonant cavity of the dual-wavelength good-bad cavity system is preliminarily stabilized on an ultrastable optical resonant cavity, namely, a good cavity laser frequency drift is consistent with the ultrastable optical resonant cavity, and on the basis, the frequency stabilization of bad cavity laser is preliminarily realized by utilizing the cavity traction suppression effect of the bad cavity laser;
3) the bad cavity laser is used as an ultra-narrow line width laser source, the repetition frequency of the optical frequency comb is locked on the bad cavity laser, and the frequency drift of the optical frequency comb repetition frequency is consistent with the bad cavity laser; and then, locking the other path of the good cavity laser on the comb teeth of the optical comb corresponding to the laser wavelength of the good cavity through beat frequency, so that the frequency drift of the good cavity laser is consistent with the frequency drift of the repetition frequency of the optical comb, namely consistent with the bad cavity laser.
Further, the implementation method of the step 3) is as follows: the zero frequency f of an ultrastable femtosecond optical frequency comb 32
ceoThe signal is locked on a frequency reference provided by a microwave atomic clock; the ultrastable femtosecond optical frequency comb 32 outputs a repetition frequency f
kLight of (a) and a repetition frequency of f
gOf repetition frequency f
kThe same or similar to the laser frequency of the bad cavity, the repetition frequency f
gThe frequency of the laser is the same as or similar to that of the good cavity laser; repetition frequency f
kThe light and the bad cavity laser are respectively input into a fifth polarization beam splitter prism 34 to obtain a beat frequency signal f
b(ii) a Will signal f
bConverted by the third photodetector 35 and input to the first phase-locked loop 37, the first phase-locked loop 37 being dependent on the signal f
bGenerating an error signal with the rf standard signal input from the second signal generator 36, and stabilizing the repetition frequency of the optical comb by the error signal through the third servo feedback circuit 38; repetition frequency f
gThe light and the good cavity laser output by the second polarization splitting prism 20 are respectively input into a sixth polarization splitting prism 39 to obtain a beat frequency signal f
b’Will signal f
b’Converted by the fourth photo detector 40 and input to a second phase locked loop 42, the second phase locked loop 42 being dependent on the signal f
b’And the radio frequency standard signal input by the third signal generator 41, generates an error signal and adjusts the length of the main resonant cavity through a fourth servo feedback circuit 43.
Further, in the step 1), the dual-wavelength good-bad cavity laser is firstly led out through the first dichroic mirror, and then the separation of the good-bad cavity laser is realized through the second dichroic mirror.
Further, in the step 2), the good cavity laser is divided into two laser beams with different intensities through a second half-wave plate and a second polarization beam splitter prism, wherein one laser beam is used for PDH frequency stabilization to primarily lock the cavity length of the main resonant cavity, the laser beam is firstly subjected to phase modulation through an electro-optical modulator, a pair of side bands with opposite phases appears on the modulated optical field at two sides of a carrier wave, a first signal generator provides a driving signal for the first phase modulator, the laser beam is divided into two laser beams through a third polarization beam splitter prism, a transmission light enters a reference cavity through a quarter coupling, a reflection signal of the reference wave plate cavity passes through the quarter wave plate again and is received by a first photoelectric detector through the third polarization beam splitter prism, the first signal generator provides a reference signal for the first mixer, and the frequency discrimination signal is obtained after mixing and phase-sensitive demodulation with a signal received by the first photoelectric detector in the first mixer, i.e., the PDH signal; the PDH signal is fed back to the piezoelectric ceramic chip of the main resonant cavity through a second servo feedback circuit, so that the good cavity laser frequency is locked on the resonant frequency of the reference cavity, and the primary stability of the cavity length of the main resonant cavity and the line width narrowing of the good cavity laser are realized; after the bad cavity laser sequentially passes through the second dichroic mirror and the fourth polarization beam splitting prism, reflected light enters the second photoelectric detector, optical signals are converted into electric signals, and the detector is connected with the fast Fourier transform analyzer and used for measuring the line width of the bad cavity laser.
One of the purposes of the invention is to combine a PDH frequency stabilization method to lock good cavity laser in a dual-wavelength good-and-bad cavity system on an ultrastable optical resonant cavity 24, stabilize the cavity length of a main resonant cavity, and then utilize the cavity traction inhibition effect of bad cavity laser to reduce the line width and frequency drift of the output bad cavity laser by two orders of magnitude compared with that of the good cavity laser stabilized by PDH frequency, thereby reducing the influence of the residual cavity traction effect on an active optical frequency scale.
The invention discloses a method for realizing short-term stability and line width narrowing of bad cavity laser based on a dual-wavelength good-bad cavity active optical clock principle, which comprises the following steps: the system comprises a first laser, a first laser power supply, an integrated invar steel resonant cavity, a four-point coated main resonant cavity mirror-plane mirror and a plano-concave mirror, a piezoelectric ceramic piece, a good cavity laser gain medium, an alkali metal atom air chamber, a magnetic shielding box, a second laser power supply, an isolator, a first half-wave plate, a first polarization splitting prism, a modulation transfer spectrum frequency stabilization module, a first servo feedback circuit, a first dichroic mirror, a second half-wave plate, a second polarization splitting prism, a phase modulator, a third polarization splitting prism, a quarter-wave plate, a high-fineness Fabry-Perot reference cavity, a first photoelectric detector, a first signal generator, a first frequency mixer, a second servo feedback circuit, a fourth polarization splitting prism, a second photoelectric detector and a fast Fourier transform spectrum analyzer.
Wherein, the alkali metal atom gas chambers are filled with soda metal atoms, and the glass bubbles are externally connected with a temperature control system for heating and are arranged in a magnetic shielding box; the main resonant cavity mirror is embedded in integrated invar steel to increase the stability of the cavity, wherein the two resonant cavity mirrors can control the dual-wavelength laser signals to respectively work in a good cavity range and a bad cavity range through four-point coating;
1) the first laser power supply is used for driving the first laser to output laser, and is used for pumping a good cavity laser gain medium in the main resonant cavity and outputting good cavity laser.
2) The second laser power supply is used for driving the second laser to output laser, and frequency stabilization is carried out by a modulation transfer spectrum method, wherein the laser emitted by the second laser passes through a first half-wave plate and a first polarization beam splitter prism, the intensity of two beams of laser can be adjusted by rotating the angle between the first half-wave plate and the first polarization beam splitter prism, strong light is used as pump light of a bad cavity gain medium in an alkali metal atom gas chamber 8, and weak light is input into a modulation transfer spectrum frequency stabilization module 15 and is used for modulating transfer spectrum frequency stabilization and stabilizing the frequency of the pump laser 10 of a bad cavity of an active optical clock to obtain a high-performance modulation transfer spectrum signal; the modulation transfer spectrum signal is fed back to the second laser power supply through the first servo feedback circuit, so that the laser frequency of the second laser is locked on the atomic transfer spectrum line. The steps realize the frequency stabilization of the pump light of the bad cavity laser.
3) The laser emitted by the second laser is modulated, transferred and frequency stabilized to pump atoms in the alkali metal atom gas chamber, and forms multi-atom coherent stimulated radiation between transition energy levels of the alkali metal atoms through weak feedback of the main resonant cavity to output the laser of the bad cavity.
4) Step 1) to step 3) realize the simultaneous output of dual-wavelength good-bad cavity laser in the main resonant cavity, then realize the separation of good-bad cavity laser through first dichroic mirror and second dichroic mirror, good cavity laser is divided into two routes, wherein a route of good cavity laser is locked on the high-fineness Fabry-Perot reference cavity with the linewidth of 0.6Hz and the frequency drift of 0.01Hz/s through PDH frequency stabilization technology, realize that the line width of good cavity laser is narrowed and the cavity length of the main resonant cavity is stabilized preliminarily, make the cavity length jitter of the main resonant cavity consistent with the reference cavity, the concrete method is as follows: the dual-wavelength good-bad cavity laser is led out through a first dichroic mirror (the bad cavity laser and the good cavity laser are both high-reflection), then the good-bad cavity laser is separated through a second dichroic mirror (the bad cavity laser is high-reflection, the good cavity laser is high-transmission), the good cavity laser is separated into two laser beams with unequal intensities through a second half-wave plate and a second polarization splitting prism, the intensities of the two laser beams are adjusted through rotating an angle between the second half-wave plate and the second polarization splitting prism, reflected light is used for PDH frequency stabilization to primarily lock the cavity length of a main resonant cavity, the laser is firstly subjected to phase modulation through an electro-optical modulator, a pair of opposite-phase sidebands appear on two sides of a carrier wave of a modulated light field, a first signal generator provides a driving signal for the first phase modulator, the two laser beams are separated through a third polarization splitting prism, the transmitted light enters a high-fineness Fabry-Perot reference cavity through a quarter-wave plate coupling, the reflected signal of the reference cavity passes through the quarter-wave plate again, passes through the third polarization beam splitter prism and is received by the first photoelectric detector, the first signal generator provides a reference signal for the first frequency mixer, and the reference signal and the signal received by the first photoelectric detector are subjected to frequency mixing and phase-sensitive demodulation in the first frequency mixer to obtain a frequency discrimination signal, namely a PDH signal. The third polarization beam splitter prism and the quarter wave plate have the function of leading the reflected light of the reference cavity into the first photoelectric detector. And a PDH signal is fed back to the piezoelectric ceramic chip of the main resonant cavity through a second servo feedback circuit, and the good cavity laser frequency is locked on the resonant frequency of the reference cavity through high-precision feedback control, so that the primary stability of the cavity length of the main resonant cavity and the line width narrowing of the good cavity laser are realized.
5) Bad chamber laser passes through second dichroscope and fourth polarization beam splitting prism after, the reverberation gets into the second photoelectric detector, convert the light signal into the signal of telecommunication, the detector is connected fast Fourier transform analysis appearance and is used for measuring the linewidth of bad chamber laser, because bad chamber laser among the good or bad chamber laser of dual wavelength has the chamber and draws the inhibitory effect, have certain immunity to the chamber length shake promptly, consequently output bad chamber laser frequency drift is two orders of magnitude lower than the good chamber laser through PDH frequency stabilization to output linewidth also is two orders of magnitude narrower than the good chamber laser of PDH frequency stabilization.
The second purpose of the invention is that the double-wavelength good-bad cavity active optical clock based on the secondary cavity locking technology is combined with the ultrastable femtosecond optical comb, the main resonant cavity which is locked on the high-fineness Fabry-Perot reference cavity is locked on the bad cavity laser which is output in the first purpose, and the cavity traction inhibition effect of the bad cavity laser is reused, so that the line width and the frequency drift of the finally output bad cavity laser are reduced by two orders of magnitude compared with the bad cavity laser in the first purpose, the influence of the residual cavity traction effect on the long-term stability of the active optical frequency standard is greatly reduced or even eliminated, and the effect of the shaking immunity of the bad cavity laser on a cavity mode in the double-wavelength good-bad cavity system is achieved.
The invention relates to a method for realizing a dual-wavelength good-bad cavity active optical clock based on a secondary cavity locking technology, which comprises the following steps: all optical elements and instruments, ultrastable femtosecond optical comb, microwave clock, fifth polarization beam splitter prism, third photoelectric detector, second signal generator, first phase-locked loop, third servo feedback circuit, sixth polarization beam splitter prism, fourth photoelectric detector, third signal generator, second phase-locked loop and fourth servo feedback circuit used in the first purpose.
1) The wavelength range of the femtosecond optical comb should cover the wavelength range of the good or bad cavity laser, wherein the zero frequency f of the ultrastable femtosecond optical frequency comb 32
ceoThe signal is locked on a frequency reference provided by a microwave atomic clock: extracting zero frequency f of femtosecond optical comb by using 1f-2f interference (self-reference technology)
ceoSignal when zero frequency f
ceoWhen the signal is phase-discriminated from the microwave frequency standard, a phase error signal is output, and the phase error is usedBy changing the intensity of the laser pump light by signal, f can be adjusted
ceoSignal, bringing it in phase with the microwave frequency standard, and then precisely controlling it.
2) Further, when the frequency f is zero
ceoAfter signal locking, the bad cavity laser output in the first purpose is used as an optical frequency reference f
refoLocking the repetition frequency f of the optical comb
r: the k-th comb tooth in the optical comb is f
k，f
kAnd an active optical frequency scale f
refoThe frequencies are close and the beat frequency is f
bThen f
k＝f
refo±f
b(sign is given by f)
kAnd f
refoThe beat frequency signal f is obtained by the formula
b)。f
refoIs a known optical frequency standard if f is precisely controlled
bThen f
kAnd is accurately controlled. Let f
bThe signal is transmitted to the phase-locked control loop I together with the radio frequency standard generated by the second signal generator 36 by taking the radio frequency standard as reference, the phase-locked control loop identifies the phase between the signals to generate an error signal, and the cavity length is adjusted by controlling a cavity mirror arranged on a piezoelectric ceramic piece of the comb laser through a third servo feedback circuit, so that the repetition frequency f is accurately controlled
r。
3) Further, the good-cavity laser transmission light passing through the second polarization beam splitter prism is locked at the repetition frequency f of the optical comb
rUpper (method similar to the above-described locking of the optical comb repetition frequency): the k' th comb tooth in the optical comb is f
k’，f
k’With good cavity laser frequency f
gApproaching and beating to obtain a beat signal f
b’Then f
g＝f
k’±f
b’(sign is given by f)
k’And f
gSize relationship determination). f. of
k’The frequency jitter of one comb tooth as an optical comb is consistent with the preliminarily stable bad cavity laser, if f is accurately controlled
b’So that the cavity laser f is good
gAnd is accurately controlled. Let f
b’The signal is fed into the second phase-locked control loop together with the radio frequency standard by taking the radio frequency standard as reference, the phase-locked control loop identifies the phase between the signals to generate an error signal, and the error signal is fed back quickly by a fourth servo feedback circuit to control a first cavity mirror arranged on the piezoelectric ceramic of the main resonant cavity to adjust the main resonant cavityThe resonant cavity is long, so that the frequency of good-cavity laser is accurately controlled, namely the good-cavity laser is locked on the bad-cavity laser which is initially stable in the first step.
Due to the cavity traction inhibition effect of the bad cavity laser, the frequency scale frequency drift of the finally output active optical frequency scale can be reduced by two orders of magnitude on the basis of the first-order good cavity laser, the frequency drift of the active optical frequency scale is reduced by four orders of magnitude compared with the fine-degree Fabry-Perot reference cavity through the secondary cavity locking technology, the influence of the residual cavity traction effect on the long-term stability of the active optical frequency scale is greatly reduced or even eliminated, and the active optical frequency scale with the quantum limit line width is realized at room temperature.
The invention has the advantages that:
the invention integrates and applies the four-aspect technology: the dual-wavelength good-bad cavity active optical clock, a PDH frequency stabilization technology, an optical comb repetition frequency locking technology and a fast phase modulation feedback technology. The active optical frequency standard with the millihertz quantum limit line width and the immunity to the cavity length noise is innovatively realized, and the frequency drift of the active optical frequency standard is finally reduced to 10
-6Hz/s, eliminating the influence of the residual cavity traction effect on the bad cavity laser in the dual-wavelength good-bad cavity active optical clock system; through four-point coating and selection of proper good-bad cavity gain media (the good cavity gain media can be Nd: YAG crystal, and the bad cavity gain media are atoms contained in an alkali metal atom air chamber 8, such as cesium atoms), the output dual-wavelength laser can work in the range of the good cavity and the bad cavity respectively; locking the cavity length of a main resonant cavity on a high-fineness Fabry-Perot reference cavity by adopting a PDH frequency stabilization technology, and preliminarily realizing the frequency stabilization of the bad cavity laser by utilizing the cavity traction inhibition effect of the bad cavity laser; the optical frequency comb is used as a transmission medium, the repetition frequency of the optical comb is locked on the preliminarily stable bad cavity laser, the preliminarily stable good cavity laser is locked on one comb tooth of the optical comb, which is close to the good cavity laser wavelength, the cavity length of the main resonant cavity is locked again by using the rapid phase feedback technology, the cavity traction inhibition effect of the bad cavity laser in the dual-wavelength signal is reused, the frequency drift of the finally output active optical frequency scale is reduced to be square times of the cavity traction inhibition coefficient of the bad cavity laser, and the second-level stability of 10 at room temperature is realized
-16Long term stabilityIs better than 10
-18Frequency drift of 10
-6The active optical frequency standard of Hz/s can be used as an independent laser frequency standard, and can also be transferred by an optical comb or a Fabry-Perot cavity to provide narrow linewidth laser light sources with different frequency bands for other precision measurement.
Drawings
Fig. 1 is a schematic diagram of a first embodiment of a dual-wavelength good-bad cavity active optical clock based on a secondary cavity locking technology and an implementation method thereof according to the present invention;
fig. 2 is a schematic diagram of a second embodiment of the dual-wavelength good-bad cavity active optical clock based on the secondary cavity locking technology and the implementation method thereof.
Wherein, 1-a first laser, 2-a first laser power supply, 3-an integrated invar resonant cavity, 4-a four-point coated main resonant cavity mirror-plane mirror, 5-a plano-concave mirror, 6-a piezoelectric ceramic plate, 7-a good cavity laser gain medium, 8-an alkali metal atom air chamber, 9-a magnetic shielding box, 10-a second laser, 11-a second laser power supply, 12-an isolator, 13-a first half-wave plate, 14-a first polarization beam splitter prism, 15-a modulation transfer spectrum frequency stabilization module, 16-a first servo feedback circuit, 17-a first dichroic mirror, 18-a second dichroic mirror, 19-a second half-wave plate, 20-a second polarization beam splitter prism, 21-a phase modulator, 22-a third polarization beam splitter mirror, 23-quarter wave plate, 24-high-fineness Fabry-Perot reference cavity, 25-first photoelectric detector, 26-first signal generator, 27-first mixer, 28-second servo feedback circuit, 29-fourth polarization beam splitter prism, 30-second photoelectric detector, 31-fast Fourier transform spectrum analyzer, 32-ultrastable femtosecond optical frequency comb, 33-microwave atomic clock, 34-a fifth polarization beam splitter prism, 35-a third photoelectric detector, 36-a second signal generator, 37-a first phase-locked loop, 38-a third servo feedback circuit, 39-a sixth polarization beam splitter prism, 40-a fourth photoelectric detector, 41-a third signal generator, 42-a second phase-locked loop and 43-a fourth servo feedback circuit.
Detailed Description
The invention will be further elucidated by means of specific embodiments in the following with reference to the drawing.
Example one
As shown in fig. 1, the dual-wavelength good-bad cavity active optical clock based on the secondary cavity-locking technology and the implementation method thereof in this embodiment include: the system comprises a first laser 1, a first laser power supply 2, an integrated invar resonant cavity 3, a four-point coated main resonant cavity mirror-plane mirror 4, a plano-concave mirror 5, a piezoelectric ceramic plate 6, a good cavity laser gain medium 7, an alkali metal atom air chamber 8, a magnetic shielding box 9, a second laser 10, a second laser power supply 11, an isolator 12, a first half-wave plate 13, a first polarization beam splitter prism 14, a modulation transfer spectrum frequency stabilization module 15, a first servo feedback circuit 16, a first dichroic mirror 17, a second dichroic mirror 18, a second half-wave plate 19, a second polarization beam splitter prism 20, a phase modulator 21, a third polarization beam splitter prism 22, a quarter-wave plate 23, a high-fineness Fabry-Perot reference cavity 24, a first photoelectric detector 25, a first signal generator 26, a first mixer 27, a second servo feedback circuit 28, a fourth polarization beam splitter prism 29, A second photodetector 30, and a fast fourier transform spectrum analyzer 31. The plane mirror 4 has high transmittance for the laser wavelength output by the first laser 1 and the second laser 10, and has high reflection for the laser wavelength of the output good cavity and the laser wavelength of the output bad cavity; the plano-concave mirror 5 is highly transparent to the laser wavelength output by the second laser 10, does not require the laser wavelength output by the first laser, is highly reflective to the laser wavelength of a good cavity, and has low reflectivity to the laser of a bad cavity, and the reflectivity affects the coefficient of the bad cavity.
Wherein, the first laser 1 and the second laser 10 are respectively a 808nm semiconductor laser and a 459nm narrow linewidth interference filter external cavity semiconductor laser; the four-point coated flat mirror 4 is plated with 808nm high-transmittance, 1064nm and 1470nm high-reflectance, the planoconcave mirror 5 is plated with 459nm high-transmittance, 1064nm high-reflectance and 1470nm reflectance of 50%, and the good or bad cavity laser with 1064/1470nm dual-wavelength can be controlled to work in the good cavity range and the bad cavity range respectively; YAG crystal as well as alkali metal atom gas chamber 8 filled with pure cesium atom, and the atom gas chamber is heated by external temperature control system and placed in magnetic shielding box 9; the main resonant cavity mirror is embedded in the integrated invar steel resonant cavity 3, so that the stability of the cavity is improved.
1) The first laser power supply 2 is used for driving the first laser 1 to output 808nm laser, pumping a good cavity laser gain medium 7 in the main resonant cavity and outputting 1064nm good cavity laser;
2) the 459nm laser output by the second laser 10 passes through the first half wave plate 13 and the first polarization beam splitter prism 14, the intensity of the two beams of laser is adjusted by rotating the angle between the first half wave plate 13 and the first polarization beam splitter prism 14, the strong light is used as the pumping light of the bad cavity laser, the weak light is used for the modulation transfer spectrum frequency stabilization of the pumping light of the 459nm bad cavity laser, and the frequency of the second laser 10 is stabilized; the modulated transfer spectrum signal is fed back to the second laser power supply 11 through the first servo feedback circuit 16, so as to lock the laser frequency of the second laser 10 on the cesium atoms 6
2S
1/2(F＝4)-7
2P
1/2(F-3) on the transition line. The frequency stabilization of the 459nm bad cavity laser pumping light is realized through the steps;
3) 459nm laser emitted by a second laser 10 is modulated, transferred and frequency stabilized to pump cesium atoms in an alkali metal atom gas chamber 8, polyatomic coherent stimulated radiation is formed between cesium atom transition energy levels through weak feedback of a main resonant cavity, and 1470nm bad cavity laser is output;
4) the method comprises the following steps 1) to 3), simultaneous output of 1064/1470nm dual-wavelength good-and-bad cavity laser in a main resonant cavity is achieved, then separation of good-and-bad cavity laser is achieved through a first dichroic mirror 17 and a second dichroic mirror 18, 1064nm good-cavity laser is divided into two paths, one path is locked on a high-fineness Fabry-Perot reference cavity 24 with the line width of 0.6Hz and the frequency drift of 0.01Hz/s through a PDH frequency stabilization technology, line width narrowing of the 1064nm good-cavity laser is achieved, the length of the main resonant cavity is stabilized preliminarily, and the length of the main resonant cavity is shaken to be consistent with that of the reference cavity 24, and the specific method is as follows: 1064/1470nm dual-wavelength good-bad cavity laser is led out through a first dichroic mirror 17, separation of good-bad cavity laser is achieved through a second dichroic mirror 18, the good-cavity laser is divided into two laser beams with unequal intensities through a second half-wave plate 19 and a second polarization beam splitter 20, the intensities of the two laser beams are adjusted through rotating an angle between the second half-wave plate 19 and the second polarization beam splitter 20, reflected light passing through the second polarization beam splitter 20 is used for PDH frequency stabilization to primarily lock the cavity length of a main resonant cavity, the laser is firstly subjected to phase modulation through a phase modulator 21, a pair of side bands with opposite phases appear on two sides of a carrier wave after modulated light field, a first signal generator 26 provides a driving signal for the phase modulator 21, the laser beams are divided into two laser beams through a third polarization beam splitter 22, transmitted light is coupled into a high-fineness Fabry-Perot reference cavity 24 through a quarter wave plate 23, the reflected signal of the reference cavity passes through the quarter-wave plate 23 again, passes through the third polarization beam splitter prism 22, and is provided with a reference signal by the first photodetector 25 and the first signal generator 26 for the first mixer 27, and is mixed and phase-sensitively demodulated with the signal received by the first photodetector 25 in the first mixer 27 to obtain a frequency discrimination signal, i.e., a PDH signal. The third polarization splitting prism 22 and the quarter-wave plate 23 function to direct the reference cavity reflected light into the first photodetector 25. A PDH signal is fed back to the piezoelectric ceramic plate 6 of the main resonant cavity through the second servo feedback circuit 28, and the 1064nm good cavity laser frequency is locked on the resonant frequency of the reference cavity through high-precision feedback control, so that the primary stability of the cavity length of the main resonant cavity and the line width narrowing of the 1064nm good cavity laser are realized;
5) after 1470nm bad cavity laser passes through the second dichroic mirror 18 and the fourth polarization beam splitter prism 29, reflected light enters the second photoelectric detector 30, optical signals are converted into electric signals, the detector is connected with the fast Fourier transform spectrum analyzer 31 and used for measuring the line width of the 1470nm bad cavity laser, and the 1470nm bad cavity laser has a cavity traction inhibition effect, namely, has a certain immunity effect on cavity length jitter, so that the frequency drift and the line width of the 1470nm bad cavity laser are output two orders of magnitude lower than that of 1064nm good cavity laser subjected to PDH frequency stabilization.
Example two
As shown in fig. 2, the dual wavelength good-bad cavity active optical clock based on the secondary cavity locking technology and the implementation method thereof of the present invention include: all optical elements and instruments used in the first embodiment, the ultrastable femtosecond optical frequency comb 32, the microwave atomic clock 33, the fifth polarization beam splitter prism 34, the third photodetector 35, the second signal generator 36, the first phase-locked loop 37, the third servo feedback circuit 38, the sixth polarization beam splitter prism 39, the fourth photodetector 40, the third signal generator 41, the second phase-locked loop 42, and the fourth servo feedback circuit 43.
1) Wherein the wavelength range of the optical comb should cover 1000-1500nm, wherein the zero frequency f
ceoThe signal is locked on a frequency reference provided by a microwave atomic clock: extraction of zero frequency f of optical comb using 1f-2f interference (self-referencing technique)
ceoSignal when zero frequency f
ceoWhen the signal is compared with microwave frequency standard, a phase error signal is output, and the signal is used to change the light intensity of laser pump to regulate f
ceoSignal, bringing it in phase with the microwave frequency standard, and then precisely controlling it.
2) Further, when the frequency f is zero
ceoAfter signal locking, 1470nm active optical frequency standard output in the first embodiment is used as the optical frequency reference f
refoControlling the repetition frequency f of the optical comb
r: the k-th comb tooth in the optical comb is f
k，f
kAnd 1470nm active optical frequency standard f
refoThe frequencies are close and the beat frequency is f
bThen f
k＝f
refo±f
b(sign is given by f)
kAnd f
refoSize relationship determination). f. of
refoIs a known optical standard if f is precisely controlled
bThen f
kAnd is accurately controlled. Let f
bThe signal is transmitted to the first phase-locked loop 37 together with the radio frequency standard by taking the radio frequency standard as reference, the phase-locked control loop identifies the phase between the signals to generate an error signal, and the cavity length is adjusted by controlling a cavity mirror arranged on the PZT of the optical comb laser through a third servo feedback circuit 38, so that the repetition frequency f of the optical comb is accurately controlled
r。
3) Further, the 1064nm good cavity laser transmission light passing through the third polarization splitting prism 20 is locked at the repetition frequency f of the optical comb
rUpper (method similar to the above-described locking of the optical comb repetition frequency): the k' th comb tooth in the optical comb is f
k’，f
k’And 1064nm good cavity laser f
gThe frequencies are close and the beat frequency is f
b’Then f
g＝f
k’±f
b’(sign is given by f)
k’And f
gSize relationship determination). f. of
k’As one comb of the optical comb, the frequency of the comb is jittered and the 1470nm bad cavity laser is initially stableIn agreement, if f is precisely controlled
b’Then 1064nm good cavity laser f
gAnd is accurately controlled. Let f
b’The signal is referred to the radio frequency standard and sent to the second phase-locked loop 42 together with the radio frequency standard, the second phase-locked loop 42 identifies the phase between the signals to generate an error signal, and the error signal is fed back quickly through the fourth servo feedback circuit 43 to control the cavity mirror I arranged on the piezoelectric ceramic 6 of the main resonant cavity to adjust the cavity length of the main resonant cavity, so that the frequency of the 1064nm good cavity laser is accurately controlled, that is, the 1064nm good cavity laser is locked on the 1470nm bad cavity laser which is initially stable in the first embodiment. Due to the cavity pulling suppression effect of the bad cavity laser, the finally output frequency scale frequency drift of the 1470nm active optical frequency scale can be reduced by two orders of magnitude on the basis of the 1064nm good cavity laser in the embodiment, the frequency drift of the 1470nm active optical frequency scale is four orders of magnitude smaller than that of a fine Fabry-Perot reference cavity through secondary locking, the influence of the residual cavity pulling effect on the long-term stability of the active optical frequency scale is greatly reduced or even eliminated, the active optical frequency scale with quantum limit line width is realized at room temperature, and the realized 1470nm transition wavelength is in a communication waveband, so that the active optical frequency scale can be used as a communication waveband optical frequency standard with narrow line width, and the communication speed and the accuracy are greatly improved.
In this embodiment, 459nm laser is used as the pump light of the bad cavity laser. Other wavelengths, such as 420nm and 421nm, can be selected for the bad cavity laser pumping light. The bad cavity laser gain medium is cesium atoms, or rubidium atoms can be selected to realize the good and bad cavity active optical frequency standard with double wavelengths of 1064/1367nm and 1064/1529nm, and the rubidium bubbles can be used for replacing the cesium bubbles in the same basic structure according to a similar principle, so that the active optical frequency standard which has quantum limit line width and is not influenced by the residual cavity traction effect is realized at room temperature.
Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (7)
1. A double-wavelength good-bad cavity active optical clock based on a secondary lock cavity technology is characterized by comprising a double-wavelength good-bad cavity system, a first dichroic mirror (17), a second dichroic mirror (18) and an ultrastable femtosecond optical frequency comb (32), wherein double-wavelength good-bad cavity laser output by the double-wavelength good-bad cavity system is guided out by the first dichroic mirror (17) and then is separated into good-cavity laser and bad-cavity laser by the second dichroic mirror (18); the good cavity laser sequentially passes through a second half-wave plate (19), a second polarization beam splitter prism (20), a phase modulator (21), a third polarization beam splitter prism (22) and a quarter-wave plate (23) and then is coupled into a reference cavity (24), a reflected signal of the reference cavity (24) sequentially passes through the quarter-wave plate (23) and the third polarization beam splitter prism (22) and then is input into a first photoelectric detector (25), an output end of the first photoelectric detector (25) is connected with an input end of a first mixer (27), a first signal generator (26) is respectively connected with the phase modulator (21) and the first mixer (27) and is used for providing a driving signal for the phase modulator (21) and a reference signal for the first mixer (27), and the first mixer (27) is used for carrying out frequency mixing and phase demodulation on the signal input by the first photoelectric detector (25) and the reference signal to obtain a frequency discrimination signal and then passes through a second servo feedback circuit (28) Feeding back to the piezoelectric ceramic piece (6) of the main resonant cavity of the dual-wavelength good-and-bad cavity system; the cavity laser separated by the second dichroic mirror (18) is divided into two beams after passing through a fourth polarization beam splitter prism (29), one beam is output as the cavity laser, and the other beam converts an optical signal into an electric signal through a second photoelectric detector (30) and inputs the electric signal into a fast Fourier transform spectrum analyzer (31);
the zero frequency f of the ultrastable femtosecond optical frequency comb (32)
ceoThe signal is locked on a frequency reference provided by a microwave atomic clock; the ultrastable femtosecond optical frequency comb (32) outputs a repetition frequency f
kLight of (a) and a repetition frequency of f
gOf repetition frequency f
kThe same or similar to the laser frequency of the bad cavity, the repetition frequency f
gThe frequency of the laser is the same as or similar to that of the good cavity laser; repetition frequency f
kThe light and the bad cavity laser are respectively input into a fifth polarization beam splitterThe prism (34) obtains a beat frequency signal f
b(ii) a Will signal f
bThe signal is converted by a third photoelectric detector (35) and then input into a first phase-locked loop (37), the first phase-locked loop (37) is connected with a second signal generator (36) and is used for receiving a radio frequency standard signal input by the second signal generator (36), and an error signal output by the first phase-locked loop (37) stabilizes the repetition frequency of the ultrastable femtosecond optical frequency comb (32) through a third servo feedback circuit (38); repetition frequency f
gThe light and the good cavity laser output by the second polarization beam splitter prism (20) are respectively input into a sixth polarization beam splitter prism (39) to obtain a beat frequency signal f
b’Will signal f
b’And the converted signal is input into a second phase-locked loop (42) through a fourth photoelectric detector (40), the second phase-locked loop (42) is connected with a third signal generator (41) and is used for receiving the radio frequency standard signal input by the third signal generator (41), and an error signal output by the second phase-locked loop (42) adjusts the cavity length of the main resonant cavity through a fourth servo feedback circuit (43).
2. The dual-wavelength good-bad cavity active optical clock of claim 1, wherein the dual-wavelength good-bad cavity system comprises a main resonant cavity, a first laser (1) and a second laser (10) for pumping good-bad cavity gain medium in the main resonant cavity, the laser output by the second laser (10) is divided into two strong and weak beams by an isolator (12), a first half-wave plate (13) and a first polarization splitting prism (14) in sequence, wherein a weaker beam is input into a modulation transfer spectrum frequency stabilization module (15) to carry out modulation transfer spectrum frequency stabilization to obtain a modulation transfer spectrum signal, and feeds back the modulation transfer spectrum signal to the second laser (10) through a first servo feedback circuit (16), the frequency of the second laser (10) is stabilized, a stronger beam of pumping light as bad cavity laser is input into the main resonant cavity through the first dichroic mirror (17) and is used for pumping a bad cavity gain medium to output the bad cavity laser; the main resonant cavity comprises main resonant cavity mirrors, a good cavity laser gain medium (7) and a bad cavity laser gain medium which are positioned between the main resonant cavity mirrors, and a piezoelectric ceramic piece (6) is arranged on the main resonant cavity mirror.
3. The dual wavelength good-bad cavity active optical clock of claim 2, wherein said dual wavelength good-bad cavity system further comprises a magnetic shielding box (9), said main resonant cavity being located in said magnetic shielding box (9); the bad cavity laser gain medium is positioned in the alkali metal atom air chamber (8); the main resonant cavity mirror comprises a plane mirror (4) and a plane concave mirror (5), and a piezoelectric ceramic piece (6) is arranged on the plane mirror (4).
4. A method for realizing a dual-wavelength good-bad cavity active optical clock based on a secondary cavity locking technology comprises the following steps:
1) separating the dual-wavelength good-and-bad cavity laser output by the dual-wavelength good-and-bad cavity system at the same time, and respectively outputting good-cavity laser and bad-cavity laser;
2) dividing good cavity laser into two paths, wherein one path is combined with a PDH frequency stabilization technology of a passive optical clock local oscillator laser, so that the cavity length of a main resonant cavity of the dual-wavelength good-bad cavity system is preliminarily stabilized on an ultrastable optical resonant cavity, namely, a good cavity laser frequency drift is consistent with the ultrastable optical resonant cavity, and on the basis, the frequency stabilization of bad cavity laser is preliminarily realized by utilizing the cavity traction suppression effect of the bad cavity laser;
3) the bad cavity laser is used as an ultra-narrow line width laser source, the repetition frequency of the optical frequency comb is locked on the bad cavity laser, and the frequency drift of the optical frequency comb repetition frequency is consistent with the bad cavity laser; and then, locking the other path of the good cavity laser on the comb teeth of the optical comb corresponding to the laser wavelength of the good cavity through beat frequency, so that the frequency drift of the good cavity laser is consistent with the frequency drift of the repetition frequency of the optical comb, namely consistent with the bad cavity laser.
5. The method as claimed in claim 4, wherein the step 3) is realized by: the zero frequency f of an ultrastable femtosecond optical frequency comb (32)
ceoThe signal is locked on a frequency reference provided by a microwave atomic clock; the ultrastable femtosecond optical frequency comb (32) outputs a repetition frequency f
kLight of (a) and a repetition frequency of f
gOf repetition frequency f
kThe same or similar to the laser frequency of the bad cavity, the repetition frequency f
gThe frequency of the laser is the same as or similar to that of the good cavity laser; repetition frequency f
kThe light and the bad cavity laser are respectively input to a fifth polarization beam splitting prismThe mirror (34) obtains a beat frequency signal f
b(ii) a Will signal f
bConverted by a third photodetector (35) and input to a first phase-locked loop (37), the first phase-locked loop (37) being dependent on the signal f
bGenerating an error signal with the RF standard signal input by the second signal generator (36), and stabilizing the repetition frequency of the optical comb by the error signal through a third servo feedback circuit (38); repetition frequency f
gThe light and the good cavity laser output by the second polarization beam splitter prism (20) are respectively input into a sixth polarization beam splitter prism (39) to obtain a beat frequency signal f
b’Will signal f
b’Converted by a fourth photodetector (40) and input to a second phase locked loop (42), the second phase locked loop (42) being responsive to the signal f
b’And the radio frequency standard signal input by the third signal generator (41) generates an error signal and adjusts the cavity length of the main resonant cavity through a fourth servo feedback circuit (43).
6. The method as claimed in claim 4, wherein in step 1), the dual-wavelength good-and-bad cavity laser is first led out through the first dichroic mirror, and then the separation of the good-and-bad cavity laser is realized through the second dichroic mirror.
7. The method as claimed in claim 4, wherein in step 2), the good cavity laser is divided into two laser beams with different intensities by a second half-wave plate and a second polarization beam splitter prism, wherein one laser beam is used for PDH frequency stabilization primary locking of the main cavity length, the laser beam is firstly phase-modulated by an electro-optical modulator, a pair of opposite-phase sidebands appears on the modulated optical field at two sides of a carrier wave, a first signal generator provides a driving signal for the first phase modulator, the laser beam is divided into two laser beams by a third polarization beam splitter prism, the transmitted light is coupled into a reference cavity by a quarter-wave plate, a reflected signal of the reference cavity passes through the quarter-wave plate again and is received by the first photo-electric detector by the third polarization beam splitter prism, the first signal generator provides a reference signal for the first mixer, and the phase-sensitive demodulation is carried out on the reflected signal of the reference cavity by the quarter-wave plate and is mixed with a signal received by the first photo-electric detector to obtain a frequency discrimination signal, i.e., the PDH signal; the PDH signal is fed back to the piezoelectric ceramic chip of the main resonant cavity through a second servo feedback circuit, so that the good cavity laser frequency is locked on the resonant frequency of the reference cavity, and the primary stability of the cavity length of the main resonant cavity and the line width narrowing of the good cavity laser are realized; after the bad cavity laser sequentially passes through the second dichroic mirror and the fourth polarization beam splitting prism, reflected light enters the second photoelectric detector, optical signals are converted into electric signals, and the detector is connected with the fast Fourier transform analyzer and used for measuring the line width of the bad cavity laser.
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| CN110333651B (en) * | 2019-07-15 | 2021-04-02 | 温州激光与光电子协同创新中心 | Laser atomic clock locked based on coherent population trapping mode |
| CN110286577B (en) * | 2019-07-16 | 2020-10-20 | 温州激光与光电子协同创新中心 | Hyperfine energy level interval measuring device and method based on four-energy-level active optical clock |
| CN110336182B (en) | 2019-07-25 | 2020-06-23 | 温州激光与光电子协同创新中心 | Dark cavity laser |
| CN110488594A (en) * | 2019-08-12 | 2019-11-22 | 浙江法拉第激光科技有限公司 | The small caesium clock of optical pumping and preparation method thereof based on Modulation Transfer spectrum Frequency Stabilized Lasers |
| CN110784217A (en) * | 2019-10-11 | 2020-02-11 | 浙江法拉第激光科技有限公司 | Cesium microwave atomic clock based on microwave-optical frequency modulation transfer technology and implementation method |
| CN111900618B (en) * | 2020-07-31 | 2022-03-11 | 浙江法拉第激光科技有限公司 | High-stability double-frequency Faraday laser based on beat frequency locking and implementation method thereof |
| CN112003121B (en) * | 2020-08-24 | 2021-11-30 | 中国科学院上海光学精密机械研究所 | Ultra-stable microwave generation device based on dual-frequency Fabry-Perot cavity frequency stabilized laser |
| CN113097854B (en) * | 2021-04-02 | 2022-09-30 | 温州激光与光电子协同创新中心 | Faraday active optical clock-based dark cavity laser and implementation method thereof |
| CN113178773A (en) * | 2021-04-16 | 2021-07-27 | 山西大学 | Method for dynamically controlling feedback phase in optical feedback lock cavity technology |
| CN113138550B (en) * | 2021-04-20 | 2022-02-08 | 温州激光与光电子协同创新中心 | Device for generating good-cavity dual-wavelength optical frequency standard based on active optical clock |
| CN114914782A (en) * | 2022-04-15 | 2022-08-16 | 合肥工业大学 | High-efficiency frequency stabilizer of single-frequency continuous laser |
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