CN114865445A - Frequency-adjustable ultrastable laser generation method based on modulation sideband frequency locking and laser system - Google Patents
Frequency-adjustable ultrastable laser generation method based on modulation sideband frequency locking and laser system Download PDFInfo
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- H—ELECTRICITY
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- 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
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Abstract
The invention provides a frequency-adjustable ultrastable laser generating method and a laser system based on modulation sideband frequency locking, which lock primary sideband light of electro-optic modulated laser to the resonant frequency of an ultrastable optical resonant cavity, and then ensure that the modulation-demodulation phase relation in the frequency modulation process of an electro-optic crystal is constant by utilizing a frequency synthesis technology, thereby realizing the ultrastable laser with the offset frequency locking function. By means of the invention, short-term ultrastable laser with hundred MHz magnitude frequency regulation range and high spectral purity can be obtained through a simple optical structure and a control process, so that the requirement of application scenes such as precision spectral measurement, quantum communication and the like on large-range adjustable ultrastable laser signals is well met.
Description
Technical Field
The invention relates to the technical field of laser frequency stabilization, in particular to a frequency-adjustable ultrastable laser generation method and a laser system based on modulation sideband frequency locking.
Background
Ultrastable cavity stabilization is a common method for generating laser signals with ultra-high short-term stability, usually at E -15 -E -16 Order of magnitude, up to E -17 And the magnitude is superior to that of all other existing technical means.
Currently, a cavity-stabilizing frequency locking technology generally adopts international universal PDH (sound-driver Hall, resonant and non-resonant optical interference frequency locking) technology, wherein after laser is modulated by an electro-optical modulator, the original laser frequency is matched with the resonant frequency of an ultrastable optical cavity, and a cavity reflection laser signal detected by demodulation photoelectricity or a laser and resonant cavity frequency deviation signal is fed back to a laser to realize laser frequency stabilization. However, since the length of the ultrastable optical cavity is very stable, the resonant frequency thereof cannot be adjusted, and thus, the frequency stabilization can be achieved only at a specific frequency (i.e., the resonant frequency of the ultrastable optical cavity) in the prior art. However, many applications including precise spectrum measurement and quantum communication require fine scanning or controlling laser frequency within a certain range (for example, hundred megahertz), and the conventional frequency stabilization scheme for an ultra-stable cavity based on PDH technology cannot simultaneously achieve flexible laser frequency modulation and frequency-stabilized laser output.
In order to obtain the frequency modulation function, the prior art proposes a solution implemented by adding a laser frequency modulation technology on the basis of frequency-unmodulatable ultrastable laser. For example, a separate laser is used to lock to a fixed frequency of the ultrastable laser and to achieve offset frequency phase lock by adjusting the heterodyne beat frequency lock reference frequency, or an optical modulator is used to shift the frequency. However, these solutions have certain disadvantages in terms of frequency modulation range, spectral purity, etc., and cannot fully meet the requirements of application scenarios such as precision spectral measurement and quantum communication.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a frequency-adjustable ultrastable laser generation method and a laser system based on modulation sideband frequency locking, which lock primary sideband light on a laser signal subjected to electro-optic phase modulation to the resonant frequency (reference frequency) of an ultrastable optical resonant cavity, and then ensure that the modulation-demodulation phase relation in the electro-optic crystal frequency modulation process is constant by using a frequency synthesis technology, so that the ultrastable laser with the offset frequency locking function is realized.
The first aspect of the invention relates to a frequency-adjustable ultrastable laser generation method based on modulation sideband frequency locking, which comprises a frequency signal generation step, a laser signal modulation step, a reference cavity coupling step, a photoelectric detection step, a down-conversion step, an error signal generation step and a feedback locking step; wherein the content of the first and second substances,
in the frequency signal generating step, a signal having a first frequency f is generated 1 Has a second frequency f 2 And having a third frequency f 3 Of said first frequency f, said first frequency f 1 And a second frequency f 2 Adjustable and having a frequency difference Δ f therebetween, said third frequency f 3 ＝△f；
In the laser signal modulation step, phase-modulating a laser signal based on the first frequency signal, the laser signal being generated by a single-frequency laser source and having a frequency v;
in the reference cavity coupling step, coupling the phase-modulated laser signal into an ultra-stable optical resonant cavity;
in the photoelectric detection step, performing photoelectric detection on an optical signal reflected from the ultrastable optical resonant cavity relative to the laser signal, and generating a photoelectric detection signal;
in the down-conversion step, mixing the second frequency signal with the photodetection signal to obtain a down-conversion signal;
in the error signal generating step, demodulating the down-converted signal with the third frequency signal to generate a frequency error signal;
in the feedback locking step, the frequency v of the single-frequency laser source is adjusted based on the frequency error signal to lock a primary sideband frequency on the phase-modulated laser signal at a resonant frequency of the ultrastable optical resonator.
Further, the first and second frequency signals are respectively and independently generated by a frequency signal source, and the third frequency signal is generated by mixing the first and second frequency signals; and/or the frequency difference Δ v is a fixed value.
Further, based on the second order, with respect to the width of the line of resonance spectrum of the ultrastable optical resonatorA frequency f 1 The phase modulation performed is high frequency modulation.
Further, the photo-detection step further comprises the step of pre-amplifying the photo-detection signal and/or filtering the photo-detection signal to filter out the first frequency f 1 And (3) other frequency components.
Further, the second frequency signal for mixing and the photodetection signal have the same time delay; and/or the down-conversion step further comprises the step of filtering the down-converted signal to filter out other frequency components except the third frequency; and/or the down-converting step further comprises the step of amplifying the down-converted signal.
Further, the error signal generating step further includes the step of adjusting a time delay or a phase of the third frequency signal to maximize the frequency error signal.
Further, the feedback locking step further comprises the step of performing a proportional-integral operation on the frequency error signal to generate a feedback control signal.
Further, in the feedback locking step, the frequency v of the single-frequency laser source is adjusted by one or more of laser cavity temperature control, laser pump drive current control, piezoelectric ceramic, or a frequency-tunable drive electro-optic modulator based on the frequency error signal.
The second aspect of the invention relates to a frequency-tunable ultrastable laser system based on modulation sideband frequency locking, which comprises a single-frequency laser source, a frequency signal generating unit, an electro-optical modulating unit, an optical coupling unit, an ultrastable optical resonant cavity, a photoelectric detection and error signal generating unit and a laser frequency control unit, wherein:
the single-frequency laser source is arranged for generating a laser signal and is adjustable in frequency;
the frequency signal generating unit is arranged for generating a signal having a first frequency f 1 Has a second frequency f 2 The second frequency signal of,And having a third frequency f 3 Wherein the first frequency f 1 And a second frequency f 2 Adjustable and having a frequency difference Δ f therebetween, said third frequency f 3 ＝△f；
The electro-optical modulation unit is arranged for phase modulating the laser signal based on the first frequency signal;
the optical coupling unit is used for coupling the modulated laser signal into the ultrastable optical resonant cavity and transmitting a reflected light signal from the ultrastable optical resonant cavity to the photoelectric detection and error signal generation unit;
the photodetection and error signal generating unit is configured to photodetection the reflected light signal to generate a photodetection signal, mix the photodetection signal with the second frequency signal to generate a down-converted signal, and demodulate the down-converted signal with the third frequency signal to generate a frequency error signal;
the laser frequency control unit is configured to adjust the frequency of the single-frequency laser source based on the frequency error signal to frequency lock a primary sideband on the modulated laser signal at a resonant frequency of the ultrastable optical resonator.
Further, the frequency signal generating unit comprises a first and a second frequency signal source for generating the first and the second frequency signals, respectively, and a down-conversion part for mixing the first and the second frequency signals to generate the third frequency signal; and/or the frequency difference Δ f is a fixed value.
Further, the frequency signal source comprises an adjustable frequency synthesizer; and/or an amplifier and an impedance adapting element are arranged between the frequency signal generating unit and the electro-optical modulating unit.
Preferably, the electro-optical modulation unit comprises a broadband electro-optical modulator without a resonant circuit.
Preferably, the ultrastable resonant optical cavity comprises a v-P cavity.
Further, the photodetection and error signal generation unit includes a photodetection portion and an error signal generation portion; the photoelectric detection part comprises a photoelectric detector; the error signal generating section includes down-conversion means for generating the down-converted signal, and mixer demodulation means for generating the frequency error signal.
Still further, the photodetection portion further comprises a first signal amplifier and/or a first band-pass filter, the first signal amplifier being configured to amplify the photodetection signal, the first band-pass filter being configured to filter the photodetection signal to filter out components other than the first frequency; and/or the like, and/or,
the down-conversion component further comprises a second band-pass filter and/or a second signal amplifier, the second band-pass filter is configured to filter the down-converted signal to filter out components other than the third frequency, and the second signal amplifier is configured to amplify the down-converted signal; and/or the like, and/or,
the photo detection and error signal generation unit further comprises means for adjusting the time delay or phase of the third frequency signal and/or means for adjusting the time delay of the second frequency signal.
Further, the laser frequency control unit is further configured to perform a proportional-integral operation on the frequency error signal to generate a feedback control signal.
Drawings
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 shows a frame schematic diagram of a frequency tunable ultrastable laser system based on modulation sideband frequency locking according to the present invention.
Fig. 2 shows a frame schematic diagram of a frequency signal generating unit in a frequency tunable ultrastable laser system based on modulation sideband frequency locking according to the present invention.
Fig. 3 shows a block schematic diagram of a photodetection and error signal generation unit in a frequency tunable ultrastable laser system based on modulation sideband frequency locking according to the present invention.
Detailed Description
Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following examples are provided by way of illustration in order to fully convey the spirit of the invention to those skilled in the art to which the invention pertains. Accordingly, the present invention is not limited to the embodiments disclosed herein.
In order to obtain the frequency-adjustable ultrastable laser, the invention provides that primary sideband light on a laser signal subjected to phase modulation is locked to the resonant frequency (reference frequency) of an ultrastable optical resonant cavity, and the short-term ultrastable laser with adjustable frequency is obtained by adjusting the electro-optic phase modulation frequency by means of the relationship between the primary sideband frequency and the frequency of the laser signal and the phase modulation frequency.
Specifically, the frequency-tunable ultrastable laser generation method based on modulation sideband frequency locking according to the invention can comprise a frequency signal generation step, a laser signal modulation step, a reference cavity coupling step, a photoelectric detection step, a down-conversion step, an error signal generation step and a feedback locking step.
In the frequency signal generating step, a first frequency f is generated 1 Has a second frequency f 2 And having a third frequency f 3 Of the third frequency signal. Wherein the first frequency f 1 And a second frequency f 2 Adjustable and fixed frequency difference delta f, third frequency f between them 3 Is f 1 -f 2 ＝△f。
As an example, the first and second frequency signals may each be generated by means of a separate frequency signal source (e.g. a tunable frequency synthesizer), and the third frequency signal may be generated by mixing the first frequency signal and the second frequency signal.
In the laser signal modulation step, a laser signal having a fourth frequency v is phase-modulated based on the first frequency signal, forming a modulated laser signal. As an example, the laser signal may be generated by a single frequency laser source.
Those skilled in the art know that the phase-modulated laser signal mainly comprises a laser signal (carrier) having a fourth frequency v, and a pair of frequencies (i.e. primary sideband frequencies) located on both sides of the laser signal are v ± f 1 And the first order sideband light in phase opposition.
In a reference cavity coupling step, a phase modulated laser signal is coupled into an ultrastable optical resonator.
In the invention, the ultrastable optical resonant cavity can be a v-P reference cavity arranged in a vacuum environment and used for providing reference frequency so as to lock frequency; first frequency f 1 Is selected to be based on the first frequency f relative to the width of the resonance line of the reference cavity 1 Is a high frequency modulation to allow a large (e.g., hundreds of MHz) frequency tuning range to be provided.
In the photodetection step, a reflected light signal from the ultrastable optical resonator is photodetection to generate a photodetection signal.
In a preferred example, the photodetection step may further comprise a step of pre-amplifying the photodetection signal, and/or a step of filtering the photodetection signal to filter out the first frequency f 1 And other frequency components.
In the down-conversion step, the second frequency signal is mixed with the photodetection signal generated in the photodetection step to obtain a down-converted signal. Thereby, the frequency is set to the first frequency f 1 Down-converting the photo-detection signal to a frequency f 1 -f 2 A down-converted signal of Δ f.
According to the invention, the second frequency signal used for mixing and the photo detection signal have the same time delay. As an example, the time delay may be controlled by means of a time delay element.
In a preferred example, the down-converting step may further include the step of filtering the down-converted signal to filter out frequency components other than the third frequency af, and/or the step of amplifying the down-converted signal.
In the error signal generating step, the down-converted signal is demodulated with a third frequency signal (i.e., a demodulated signal) to generate a frequency error signal indicative of a deviation of the selected primary sideband frequency from a reference frequency of the hyperstable optical resonator.
According to the present invention, the error signal generating step may further include the step of adjusting a time delay or a phase of the third frequency signal to maximize the frequency error signal. Therefore, the fixed phase relation between the demodulation signal and the down-conversion signal to be demodulated can be kept in the frequency variation process, and reliable frequency locking is realized, so that a reliable frequency-adjustable ultrastable laser signal is allowed to be obtained. Meanwhile, by setting a fixed demodulation frequency, the method is beneficial to noise filtering and amplification design, ensures the efficiency and reliability of the system and improves the performance of the system.
As an example, the adjustment of the phase or time delay of the third frequency signal may be realized by means of a phase shifter or a delay line.
In the feedback locking step, the frequency of the single-frequency laser source is adjusted based on the frequency error signal to achieve frequency locking.
As an example, the frequency of the single-frequency laser source may be adjusted by one or more of laser cavity temperature control, laser pump drive current control, piezoelectric ceramic, or a combination of frequency-tunable drive electro-optic modulators based on the frequency error signal.
As an example, the feedback locking step may further include the step of performing a proportional integral operation on the frequency error signal to generate the feedback control signal, wherein the single-frequency laser source performs the frequency adjustment based on the feedback control signal.
It can be seen that the frequency-tunable ultrastable laser generation method based on modulation sideband frequency locking of the inventionBy applying a primary sideband frequency (e.g. v-f) 1 ) Locked to the reference frequency of the hyperstable optical resonator, so that it can be simply tuned by varying the first frequency f 1 The frequency v of the short-term ultrastable laser is adjusted, and the frequency adjusting range can be up to hundreds of MHz. In addition, the method only needs to additionally arrange a frequency signal source on the basis of the traditional hyperstable laser system realized based on the PDH technology, the realization structure is simple, the process is easy to control, and the spectral purity of the finally output hyperstable laser is high.
For a better understanding of the working principle of the present invention, the frequency tunable ultrastable laser system based on modulation sideband frequency locking of the present invention will be described below with reference to the examples of fig. 1 to 3.
Fig. 1 schematically shows a frequency tunable ultrastable laser system based on modulation sideband frequency locking according to the present invention.
As shown in fig. 1, the frequency tunable ultrastable laser system of the present invention may include a single-frequency laser source 1, a frequency signal generating unit 2, an electro-optical modulating unit 3, an optical coupling unit 4, an ultrastable optical resonator 5, a photo-detection and error signal generating unit 6, and a laser frequency control unit 7.
The single-frequency laser source 1 may be any single-frequency laser having a frequency control function, which is used to generate a laser signal having a fourth frequency v.
By way of example, the frequency control function of a single frequency laser may be achieved by means of one or more of laser cavity temperature control, laser pump drive current control, piezoelectric ceramics, or a frequency-tunable driven electro-optic modulator in combination.
The frequency signal generating unit 2 is used for generating a signal having a first frequency f 1 Has a second frequency f 2 And having a third frequency f 3 Wherein the first frequency f 1 And a first frequency f 2 Adjustable and fixed frequency difference delta f-f between them 1 -f 2 And a third frequency f 3 ＝△f。
Fig. 2 shows an example of a frequency signal generating unit 2 according to the invention.
As shown in fig. 2, the frequency signal generating unit 2 may include a first frequency signal source, a second frequency signal source, and a down-conversion section.
The first and second frequency signal sources are used for independently generating first and second frequency signals, respectively, and the down-conversion component is used for mixing the first frequency signal and the second frequency signal to generate a third frequency signal.
As an example, the first and second frequency signal sources may comprise tunable frequency synthesizers.
Further, an amplifier for amplifying the first frequency signal, and/or an impedance adaptation element may also be disposed between the frequency signal generation unit 2 and the electro-optical modulation unit 3.
The electro-optical modulation unit 3 is configured to perform phase modulation on the laser signal based on the first frequency signal, thereby generating a laser signal having modulation sidebands.
As an example, the electro-optical modulation unit 3 may comprise a broadband electro-optical modulator without a resonant circuit, which may for example be driven by a broadband radio frequency signal.
The optical coupling unit 4 is used for coupling the modulated laser signal to the ultrastable optical resonant cavity 5, so that the spatial modes of the laser signal are well matched; and transmitting the reflected light signal from the ultrastable optical resonator to the photodetection and error signal generation unit 6.
As an example, the optical coupling unit 4 may comprise an optical element for adjusting the beam envelope of the laser signal to the resonance mode of the metastable optical resonator 5 and directing it into the metastable optical resonator 5.
The metastable optical cavity 5 may comprise, for example, a v-P cavity placed in a vacuum environment, the resonant frequency of which is used as the reference frequency of the metastable laser system.
The photodetection and error signal generating unit 6 may include a photodetection section and an error signal generating section, wherein: the photoelectric detection part is used for performing photoelectric detection on a reflected light signal from the ultrastable optical resonant cavity to generate a photoelectric detection signal; the error signal generating section is configured to demodulate the photodetection signal with the second and third frequency signals to generate a frequency error signal representing a deviation between the selected primary sideband frequency and a reference frequency of the hyperstable optical resonator.
Fig. 3 shows an example of a photo detection and error signal generation unit 6 according to the invention.
As shown in fig. 3, the photo-detecting portion may include a photo-detector configured to perform photo-detection on the reflected light signal from the meta-stable optical resonator and output a photo-detection signal.
As a preferred example, the photodetection section may further include a first signal amplifier and/or a first band-pass filter. The first signal amplifier is used for pre-amplifying the photoelectric detection signal, and the first band-pass filter is used for filtering the photoelectric detection signal to filter out the first frequency f 1 Other than the first frequency f, thereby obtaining a frequency band containing only the first frequency f 1 Photoelectric detection signals of the components.
The error signal generating section may include a down-conversion section and a mixing demodulation section.
The down-conversion component is used for receiving the photoelectric detection signal and the second frequency signal and mixing the second frequency signal with the photoelectric detection signal to obtain a down-conversion signal with a third frequency.
As a preferred example, the down conversion means may further comprise a second band pass filter and/or a second signal amplifier. The second band-pass filter is used for filtering the down-converted signal to filter components except for a third frequency, so that a down-converted signal only containing the third frequency components is obtained, and the second signal amplifier is used for amplifying the down-converted signal. The second signal amplifier may be, for example, a radio frequency amplifier.
The mixing demodulation component is used for receiving the down-conversion signal and the third frequency signal and demodulating the down-conversion signal by using the third frequency signal to obtain a frequency error signal.
According to the present invention, the photodetection and error signal generating unit 6 may further comprise a phase adjusting element and/or a time delay element for adjusting the time delay or phase of the third frequency signal to maximize the frequency error signal; and/or adjusting the time delay of the second frequency signal so that the second frequency signal and the photodetection signal have the same time delay.
The laser frequency control unit 7 is configured to output a feedback control signal to the single-frequency laser source based on the frequency error signal, so as to lock the primary sideband frequency to the reference frequency of the ultrastable optical resonator.
Further, the laser frequency control unit may be further arranged to perform a proportional integral operation on the frequency error signal to generate the feedback control signal.
Based on the above, on the basis of the conventional hyperstable laser system realized based on the PDH locking technology, the phase relation between the demodulation signal and the photoelectric detection signal is changed by simply changing the structure of the frequency signal generating unit, so that the first-level sideband light generated by the electro-optic modulated laser is locked to the resonant frequency of the hyperstable optical resonant cavity, and the modulation and demodulation phase relation in the frequency modulation process of the electro-optic crystal is ensured to be constant by using the frequency synthesis technology, so that the short-term hyperstable laser with high spectral purity can be obtained on the premise that the resonant frequency of the hyperstable optical resonant cavity is taken as the reference frequency (the short-term frequency stability of the ultrastable laser can reach E) -16 Magnitude or better), and the hundred MHz magnitude frequency regulation capability is obtained, so that the requirements of application scenes such as precision spectrum measurement and quantum communication on large-range adjustable ultrastable laser signals are well met. Besides, the whole laser system is simple in structure, compared with a traditional PDH system, except that the phase of a demodulation signal process is opposite to that of the traditional PDH technology, and a frequency signal generation part is changed due to the addition of a frequency modulation function, other links are kept unchanged, the spectrum of the locked laser has no additional modulation signal, the application requirements of frequency precision scanning and locking can be met, and compared with a combined implementation scheme of a non-frequency-modulation ultrastable laser and frequency modulation design, the control process of the laser system is simpler and is based on regulation.
Although the present invention has been described in connection with the embodiments illustrated in the accompanying drawings, it will be understood by those skilled in the art that the embodiments described above are merely exemplary for illustrating the principles of the present invention and are not intended to limit the scope of the present invention, and that various combinations, modifications and equivalents of the above-described embodiments may be made by those skilled in the art without departing from the spirit and scope of the present invention.
Claims (16)
1. A frequency-adjustable ultrastable laser generating method based on modulation sideband frequency locking comprises a frequency signal generating step, a laser signal modulating step, a reference cavity coupling step, a photoelectric detection step, a down-conversion step, an error signal generating step and a feedback locking step; wherein the content of the first and second substances,
in the frequency signal generating step, a signal having a first frequency f is generated 1 Has a second frequency f 2 And having a third frequency f 3 Of said first frequency f, said first frequency f 1 And a second frequency f 2 Adjustable and having a frequency difference Δ f therebetween, said third frequency f 3 ＝△f；
In the laser signal modulation step, phase-modulating a laser signal based on the first frequency signal, the laser signal being generated by a single-frequency laser source and having a frequency v;
in the reference cavity coupling step, coupling the phase-modulated laser signal into an ultra-stable optical resonant cavity;
in the photoelectric detection step, performing photoelectric detection on an optical signal reflected from the ultrastable optical resonant cavity relative to the laser signal, and generating a photoelectric detection signal;
in the down-conversion step, mixing the second frequency signal with the photodetection signal to obtain a down-conversion signal;
in the error signal generating step, demodulating the down-converted signal with the third frequency signal to generate a frequency error signal;
in the feedback locking step, the frequency v of the single-frequency laser source is adjusted based on the frequency error signal to lock a primary sideband frequency on the phase-modulated laser signal at a resonant frequency of the ultrastable optical resonator.
2. The method of claim 1, wherein the first and second frequency signals are independently generated by a frequency signal source, and the third frequency signal is generated by mixing the first and second frequency signals; and/or the frequency difference Δ f is a fixed value.
3. The method of claim 1, wherein the first frequency f is based on a width of a resonant line of the metastable optical resonator 1 The phase modulation performed is high frequency modulation.
4. The method of claim 1, wherein the step of photo-detecting further comprises pre-amplifying the photo-detection signal and/or filtering the photo-detection signal to filter the first frequency f 1 And (3) other frequency components.
5. The frequency tunable ultrastable laser generating method of claim 1, wherein:
the second frequency signal used for mixing and the photoelectric detection signal have the same time delay; and/or the like, and/or,
the step of down-converting further comprises the step of filtering the down-converted signal to filter out frequency components other than the third frequency; and/or the like, and/or,
the step of down converting further comprises the step of amplifying the down converted signal.
6. The method of frequency tunable ultrastable laser generation of claim 1, wherein the error signal generation step further comprises the step of adjusting a time delay or phase of the third frequency signal to maximize the frequency error signal.
7. The method of frequency tunable ultrastable laser generation of claim 1, wherein said feedback locking step further comprises the step of performing a proportional-integral operation on said frequency error signal to generate a feedback control signal.
8. The method of frequency tunable ultrastable laser generation of claim 1, wherein in the feedback locking step, the frequency v of the single-frequency laser source is adjusted by one or a combination of laser cavity temperature control, laser pump drive current control, piezo ceramic, or a frequency tunable driven electro-optic modulator based on the frequency error signal.
9. A frequency-adjustable ultrastable laser system based on modulation sideband frequency locking comprises a single-frequency laser source, a frequency signal generating unit, an electro-optical modulating unit, an optical coupling unit, an ultrastable optical resonant cavity, a photoelectric detection and error signal generating unit and a laser frequency control unit, wherein:
the single-frequency laser source is arranged for generating a laser signal and is adjustable in frequency;
the frequency signal generating unit is arranged for generating a signal having a first frequency f 1 Has a second frequency f 2 And having a third frequency f 3 Wherein the first frequency f 1 And a second frequency f 2 Adjustable and having a frequency difference Δ f therebetween, said third frequency f 3 ＝△f；
The electro-optical modulation unit is arranged for phase modulating the laser signal based on the first frequency signal;
the optical coupling unit is used for coupling the modulated laser signal into the ultrastable optical resonant cavity and transmitting a reflected light signal from the ultrastable optical resonant cavity to the photoelectric detection and error signal generation unit;
the photodetection and error signal generating unit is configured to photodetection the reflected light signal to generate a photodetection signal, mix the photodetection signal with the second frequency signal to generate a down-converted signal, and demodulate the down-converted signal with the third frequency signal to generate a frequency error signal;
the laser frequency control unit is configured to adjust the frequency of the single-frequency laser source based on the frequency error signal to frequency lock a primary sideband on the modulated laser signal at a resonant frequency of the ultrastable optical resonator.
10. The frequency tunable ultrastable laser system of claim 9,
the frequency signal generating unit comprises a first and a second frequency signal source for generating the first and the second frequency signals, respectively, and a down-conversion part for mixing the first and the second frequency signals to generate the third frequency signal; and/or the like, and/or,
the frequency difference Δ f is a fixed value.
11. The frequency tunable ultrastable laser system of claim 10, wherein the frequency signal source comprises a tunable frequency synthesizer; and/or an amplifier and an impedance adapting element are arranged between the frequency signal generating unit and the electro-optical modulating unit.
12. The frequency tunable ultrastable laser system of claim 9, wherein the electro-optic modulation unit comprises a broadband electro-optic modulator without a resonant circuit.
13. The frequency tunable ultrastable laser system of claim 9, wherein the ultrastable optical resonant cavity comprises a v-P cavity.
14. The frequency tunable ultrastable laser system of claim 9, wherein the photodetection and error signal generating unit comprises a photodetection portion and an error signal generating portion;
the photoelectric detection part comprises a photoelectric detector;
the error signal generating section includes down-conversion means for generating the down-converted signal, and mixer demodulation means for generating the frequency error signal.
15. The frequency tunable ultrastable laser system of claim 14, wherein:
the photodetection part further comprises a first signal amplifier and/or a first band-pass filter, the first signal amplifier being arranged to amplify the photodetection signal, the first band-pass filter being arranged to filter the photodetection signal to filter out components other than the first frequency; and/or the like, and/or,
the down-conversion component further comprises a second band-pass filter and/or a second signal amplifier, the second band-pass filter is configured to filter the down-converted signal to filter out components other than the third frequency, and the second signal amplifier is configured to amplify the down-converted signal; and/or the like, and/or,
the photo detection and error signal generation unit further comprises means for adjusting the time delay or phase of the third frequency signal and/or means for adjusting the time delay of the second frequency signal.
16. The frequency tunable ultrastable laser system of claim 9, wherein the laser frequency control unit is further configured to perform a proportional-integral operation on the frequency error signal to generate a feedback control signal.
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| CN116718123A (en) * | 2023-08-09 | 2023-09-08 | 中国科学院精密测量科学与技术创新研究院 | Absolute length measurement device and method based on PDH frequency stabilization |
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| CN116718123A (en) * | 2023-08-09 | 2023-09-08 | 中国科学院精密测量科学与技术创新研究院 | Absolute length measurement device and method based on PDH frequency stabilization |
| CN116718123B (en) * | 2023-08-09 | 2023-10-20 | 中国科学院精密测量科学与技术创新研究院 | Absolute length measurement device and method based on PDH frequency stabilization |
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