CN114755906B - Atomic beam optical clock with external modulation locking applied to detection light and preparation method thereof - Google Patents
Atomic beam optical clock with external modulation locking applied to detection light and preparation method thereof Download PDFInfo
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- CN114755906B CN114755906B CN202210482546.XA CN202210482546A CN114755906B CN 114755906 B CN114755906 B CN 114755906B CN 202210482546 A CN202210482546 A CN 202210482546A CN 114755906 B CN114755906 B CN 114755906B
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Abstract
The invention provides an atomic beam optical clock with external modulation locking for detecting light and a preparation method thereof. The atomic beam optical clock comprises a 657nm ultrastable laser system, a calcium atomic furnace, an atomic beam tube, a 423nm narrow-linewidth laser, a half-wave plate, a polarization beam splitter prism, an electro-optical modulator, a first photoelectric detector, a signal amplifier, a frequency mixer, a first servo feedback control circuit, an acousto-optic modulator, a second photoelectric detector, a signal source and a second servo feedback control circuit. The atomic beam optical clock can avoid introducing extra frequency noise and has high stability.
Description
Technical Field
The invention relates to the technical field of optical frequency standards, in particular to an atomic beam optical clock with external modulation locking applied to probe light and a preparation method thereof.
Background
Alkaline earth metals are generally chosen as quantum references for optical frequency atomic clocks (also known as optical clocks) because the outermost layer of alkaline earth elements (or alkaline earth-like elements) has two valence electrons that produce long-lived spin triplets that transition in the optical frequency band. The triplet state generated by the alkaline earth element can provide a transition energy level with a narrow line width on one hand, and is favorable for realizing a fine spectrum with the narrow line width for quantum frequency reference of an optical frequency atomic clock.
Taking calcium element in alkaline earth element as an example, the spin singlet state and spin triplet state transition of calcium atom are respectively positioned in blue light wave band and red light wave band which are quite mature in laser technology, and a foundation is laid for realizing a calcium atom beam optical clock. At present, a calcium atomic beam optical clock is generally prepared by using a transfer detection technology, and the principle is that 657nm transition and 423nm transition share a common ground state, so that a clock transition signal can be extracted by using a fluorescence signal of the 423nm transition to obtain the calcium atomic beam optical clock.
In the transition detection technique, the detection light is directly stabilized at the center frequency of the corresponding atomic transition by using an offset frequency locking or inner modulation locking method. Although the offset frequency locking method does not need to modulate the detection light, the locking precision of the detection light is difficult to ensure; the internal modulation locking method needs to perform internal modulation on the laser, and power and frequency noise of detection laser are easily introduced in the process of performing internal modulation on the laser, so that the detection and locking of a clock transition spectral line are affected, and the stability of an optical clock is deteriorated.
Disclosure of Invention
The invention provides an atomic beam optical clock with external modulation locking for detecting light, which has high stability and wide application range.
The invention provides a preparation method of an atomic beam optical clock with external modulation locking applied to probe light, which can prepare a stable atomic beam optical clock.
The invention provides an atomic beam optical clock with external modulation locking for probe light, which comprises: the device comprises a 657nm ultrastable laser system, a calcium atomic furnace, an atomic beam tube, a 423nm narrow linewidth laser, a half-wave plate, a polarization beam splitter prism, an electro-optical modulator, a first photoelectric detector, a signal amplifier, a mixer, a first servo feedback control circuit, an acousto-optical modulator, a second photoelectric detector, a signal source and a second servo feedback control circuit;
the calcium atomic furnace sprays calcium atoms to form a calcium atomic beam, the atomic beam pipe is sleeved outside the calcium atomic beam, and the atomic beam pipe sequentially comprises an atomic beam pipe front window, an atomic action area and an atomic beam pipe rear window along the spraying direction;
the light outlet end of the 423nm narrow linewidth laser faces the half-wave plate, and the light outlet end of the half-wave plate faces the polarization beam splitter prism;
a first signal output end of the signal source is connected with a signal input end of the electro-optical modulator, 423nm transmitted light emitted by the polarization beam splitter prism enters a front window of the atomic beam tube through the electro-optical modulator to generate a first fluorescent signal;
a signal output end of the first photoelectric detector is connected with a signal input end of the signal amplifier, a signal output end of the signal amplifier is connected with a first signal input end of the frequency mixer, and a second signal output end of the signal source is connected with a second signal input end of the frequency mixer;
the first photoelectric detector is configured to detect and convert the first fluorescent signal to obtain an electric signal, and the electric signal is processed by the first photoelectric detector, the signal amplifier and the frequency mixer in sequence to obtain an error signal;
the signal output end of the frequency mixer is connected with the signal input end of the first servo feedback control circuit, the signal output end of the first servo feedback control circuit is connected with the signal input end of the 423nm narrow linewidth laser, and the first servo feedback control circuit performs feedback control on the 423nm narrow linewidth laser according to the error signal;
the light outlet end of the 657nm ultrastable laser system faces the acousto-optic modulator, and 657nm emergent light emitted by the acousto-optic modulator enters the atomic action region;
423nm reflected light emitted by the polarized light splitting prism enters a rear window of the atomic beam tube to obtain a second fluorescent signal;
the signal output end of the second photoelectric detector is connected with the signal input end of the second servo feedback control circuit, the signal output end of the second servo feedback control circuit is connected with the signal input end of the acousto-optic modulator, the second photoelectric detector is configured to detect the second fluorescent signal, and the second servo feedback control circuit is used for regulating and controlling the acousto-optic modulator according to the second fluorescent signal.
The atomic beam optical clock as described above, wherein the signal source comprises a signal generator.
The atomic beam clock as described above, further comprising a first mirror, wherein the first mirror is configured to inject the 423nm transmitted light into the atomic beam tube front window.
The atomic beam optical clock further includes a second mirror configured to inject the 657nm laser light modulated by the acousto-optic modulator into the atomic active region.
The atomic beam optical clock further includes a third reflecting mirror for making the 423nm reflected light enter the atomic beam tube rear window.
The atomic beam optical clock as described above, wherein the 423nm narrow linewidth laser is selected from a narrow linewidth interference filter external cavity semiconductor laser or a narrow linewidth grating external cavity semiconductor laser.
The atomic beam optical clock further comprises a spectroscope, wherein the light outlet end of the acousto-optic modulator faces the spectroscope, 657nm laser enters the spectroscope through the acousto-optic modulator, and 657nm reflected light emitted by the spectroscope enters the atomic action region.
The invention provides a preparation method of an atomic beam optical clock with external modulation locking applied to detection light, wherein the preparation method is used for preparing the atomic beam optical clock and comprises the following steps:
calcium atoms are sprayed by a calcium atomic furnace to form a calcium atom beam, an atom beam pipe is sleeved outside the calcium atom beam, and the atom beam pipe sequentially comprises an atom beam pipe front window, an atom action area and an atom beam pipe rear window along the spraying direction;
423nm laser emitted from the light outlet end of the 423nm narrow linewidth laser sequentially passes through a half-wave plate and a polarization beam splitter prism to obtain 423nm transmitted light and 423nm reflected light;
the electro-optical modulator modulates the 423nm transmitted light according to a modulation signal provided by a signal source, so that the modulated 423nm transmitted light enters the front window of the atomic beam tube to form a fluorescent signal;
detecting the first fluorescent signal by using a first photoelectric detector and converting the first fluorescent signal into an electric signal, wherein the electric signal enters a mixer through the first photoelectric detector and a signal amplifier in sequence, and the mixer mixes a demodulation signal provided by a signal source with the electric signal to obtain an error signal;
the first servo feedback control circuit performs feedback control on the 423nm narrow linewidth laser according to the error signal;
modulating 657nm laser emitted from a light outlet end of a 657nm ultrastable laser system by using an acousto-optic modulator, so that the modulated 657nm laser enters the atomic action region;
enabling the 423nm reflected light to enter a rear window of the atomic beam tube to obtain a second fluorescent signal;
and detecting the second fluorescent signal by using a second photoelectric detector, wherein the second fluorescent signal enters the second servo feedback control circuit through the second photoelectric detector, and the second servo feedback control circuit regulates and controls the acousto-optic modulator according to the second fluorescent signal.
The method for manufacturing an atomic beam optical clock as described above, wherein the signal source includes a signal generator.
The method for preparing the atomic beam clock further comprises the step of splitting 657nm laser emitted by the acousto-optic modulator by using a beam splitter to obtain 657nm reflected light, wherein the 657nm reflected light enters the atomic action region.
According to the invention, the detection light is applied to the atomic beam optical clock locked by external modulation, 423nm transmission light is modulated by the electro-optical modulator before entering the front window of the atomic beam tube, and the operation of modulating the 423nm transmission light by using the electro-optical modulator can avoid introducing extra frequency noise into the system, thereby being beneficial to improving the stability of 423nm laser and further being beneficial to forming the atomic beam optical clock with higher stability.
According to the preparation method of the atomic beam optical clock with the detection light locked by external modulation, the 423nm transmission light is externally modulated by using the electro-optical modulator, so that extra frequency noise can be avoided, the stability of 423nm laser is improved, and 657nm clock laser signals are locked by a transfer detection mode, so that the atomic beam optical clock with higher stability can be formed.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the related art, the drawings used in the description of the embodiments of the present invention or the related art are briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic diagram of an atomic beam optical clock with external modulation locking for probe light according to some embodiments of the present invention.
Description of reference numerals:
1:657nm ultrastable laser system;
2: a calcium atomic furnace;
3: a 423nm narrow linewidth laser;
4: a half-wave plate;
5: a polarization splitting prism;
6: an electro-optic modulator;
7: a signal source;
8: a first photodetector;
9: a signal amplifier;
10: a mixer;
11: a first servo feedback control circuit;
12: an acousto-optic modulator;
13: a second photodetector;
14: a second servo feedback control circuit;
15: a first reflector;
16: a second reflector;
17: an atom beam tube.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic diagram of an atomic beam optical clock with external modulation locking for probe light according to some embodiments of the present invention. As shown in fig. 1, the present invention provides an atomic beam optical clock for applying external modulation locking to probe light, comprising: 657nm ultrastable laser system 1, calcium atomic furnace 2, atomic beam tube 17, 423nm narrow linewidth laser 3, half-wave plate 4, polarization beam splitter prism 5, electro-optical modulator 6, first photoelectric detector 8, signal amplifier 9, mixer 10, first servo feedback control circuit 11, acousto-optic modulator 12, second photoelectric detector 13, signal source 7 and second servo feedback control circuit 14;
wherein, the calcium atomic furnace 2 sprays calcium atoms to form calcium atomic beams, the atomic beam tube 17 is sleeved outside the calcium atomic beams, and the atomic beam tube 17 sequentially comprises an atomic beam tube front window, an atomic action area and an atomic beam tube rear window along the spraying direction;
the light outlet end of the 423nm narrow linewidth laser 3 faces the half-wave plate 4, and the light outlet end of the half-wave plate 4 faces the polarization beam splitter prism 5;
a first signal output end of the signal source 7 is connected with a signal input end of the electro-optical modulator 6, 423nm transmitted light emitted by the polarization beam splitter prism 5 enters a front window of the atomic beam tube through the electro-optical modulator 6 to form a first fluorescent signal;
the signal output end of the first photoelectric detector 8 is connected with the signal input end of a signal amplifier 9, the signal output end of the signal amplifier 9 is connected with the first signal input end of a mixer 10, and the second signal output end of the signal source 7 is connected with the second signal input end of the mixer 10; the first photodetector 8 is configured to detect and convert the first fluorescent signal to obtain an electrical signal, and the electrical signal is processed by the first photodetector 8, the signal amplifier 9 and the mixer 10 in sequence to obtain an error signal;
the signal output end of the mixer 10 is connected with the signal input end of the first servo feedback control circuit 11, the signal output end of the first servo feedback control circuit 11 is connected with the signal input end of the 423nm narrow linewidth laser 3, and the first servo feedback control circuit 11 performs feedback control on the 423nm narrow linewidth laser 3 according to the error signal;
the light-emitting end of the 657nm ultrastable laser system 1 faces the acousto-optic modulator 12, and 657nm emergent light emitted by the acousto-optic modulator 12 enters an atomic action region;
423nm reflected light emitted by the polarization beam splitter prism 5 enters a rear window of the atomic beam tube to obtain a second fluorescence signal;
a signal output of the second photodetector 13 is connected to a signal input of a second servo feedback control circuit 14, a signal output of the second servo feedback control circuit 14 is connected to a signal input of the acousto-optic modulator 12, the second photodetector 13 is configured to detect a second fluorescence signal, and the second servo feedback control circuit 14 is configured to regulate the acousto-optic modulator 12 according to the second fluorescence signal.
The calcium atomic furnace 2 is used for spraying calcium atoms, the calcium atoms form calcium atomic beams, the atomic beam tube 17 is sleeved outside the calcium atomic beams, and the atomic beam tube 17 sequentially comprises an atomic beam tube front window, an atomic action region and an atomic beam tube rear window along the spraying direction of the atoms. It can be understood that the atom beam tube front window is close to the jet orifice of the calcium atom furnace 2, the atom beam tube rear window is far away from the jet orifice of the calcium atom furnace 2, and the atom action zone is positioned between the atom beam tube front window and the atom beam tube rear window.
In the invention, a 423nm narrow linewidth laser 3 is used for emitting 423nm narrow linewidth laser, the 423nm narrow linewidth laser is emitted from the light outlet end of the 423nm narrow linewidth laser 3 and enters a half-wave plate 4, the 423nm narrow linewidth laser is emitted from the light outlet end of the half-wave plate 4 and enters a polarization beam splitter prism 5, and 423nm transmission light and 423nm reflection light are obtained after light splitting is carried out by the polarization beam splitter prism 5.
A modulation signal output by a first signal output end of a signal source 7 enters an electro-optical modulator 6 through a signal input end of the electro-optical modulator 6, the electro-optical modulator 6 modulates 423nm transmission light according to the first signal, the 423nm transmission light enters a front window of an atom beam tube after being modulated by the electro-optical modulator 6, the 423nm transmission light corresponds to a transition spectral line of atoms in the front window of the atom beam tube, and a first fluorescence signal is obtained.
The first fluorescent signal is received and detected by the first photodetector 8 and then converted into an electrical signal, the electrical signal is output from the signal output end of the first photodetector 8, enters the signal amplifier 9 through the signal input end of the signal amplifier 9 and is amplified, the amplified electrical signal is output from the signal output end of the signal amplifier 9, enters the mixer 10 through the first signal input end of the mixer 10, a demodulated signal output from the second signal output end of the signal source 7 enters the mixer 10 through the second signal input end of the mixer 10, and the mixer 10 mixes the demodulated signal with the electrical signal to obtain an error signal.
An error signal is output from a signal output end of the mixer 10 and enters the first servo feedback control circuit 11 through a signal input end of the first servo feedback control circuit 11, and the first servo feedback control circuit 11 performs feedback control on the 423nm narrow linewidth laser 3 according to the error signal, so that external modulation and locking of the 423nm narrow linewidth laser are realized.
The 657nm ultrastable laser system 1 of the invention is an integrated photoelectric system which adopts the PDH laser frequency stabilization technology as the working principle and is used for forming 657nm laser with extremely narrow line width. The 657nm laser formed by the 657nm ultrastable laser system 1 is an ultrastable 657nm ultra-narrow linewidth laser. In the invention, 657nm laser is emitted from the light outlet end of the 657nm ultrastable laser system 1 and enters the acousto-optic modulator 12, and enters the atomic action region after being modulated by the acousto-optic modulator 12 to interact with atoms in the atomic action region.
423nm reflected light enters a rear window of the atomic beam tube and continuously acts with the atoms subjected to the 657nm laser action to form a second fluorescent signal;
a second photoelectric detector 13 is used at the rear window of the atomic beam tube to receive a second fluorescence signal, the second fluorescence signal is converted into an electric signal, the electric signal carrying information of the second fluorescence signal is output from a signal output end of the second photoelectric detector 13 and enters a second servo feedback control circuit 14 through a signal input end of the second servo feedback control circuit 14, the second servo feedback control circuit 14 obtains a regulation and control signal according to the received signal, the regulation and control signal is output from a signal output end of the second servo feedback control circuit 14 and enters an acousto-optic modulator through a signal input end of the acousto-optic modulator 12, and the acousto-optic modulator 12 regulates and controls 657nm laser.
The calcium atomic furnace 2 is not particularly limited, and any device capable of spraying calcium atoms to form a calcium atom beam falls within the protection scope of the present invention.
The present invention does not particularly limit the form of transition spectral lines for detecting atoms, and a spectral line detection method commonly used in the art, such as a doppler spectrum, a saturation spectrum, or a lamb spectrum, may be selected.
The invention does not specially limit the 657nm ultrastable laser system 1, and all devices capable of forming ultrastable 657nm narrow linewidth laser are within the protection scope of the invention. In some embodiments, the 657nm ultrastable laser system 1 comprises: a 657nm narrow linewidth laser, a 657nm electro-optic modulator, a 657nm polarization beam splitter prism, a lambda/4 wave plate, an optical cavity, a 657nm photoelectric detector and a 657nm servo feedback control circuit; the 657nm laser emitted by the 657nm narrow-linewidth laser is modulated by the 657nm electro-optical modulator and then sequentially enters the 657nm polarization beam splitter prism, the lambda/4 wave plate and the optical cavity to obtain 657nm reflected light carrying optical cavity information, the 657nm photoelectric detector is used for detecting 657nm reflected light signals, the 657nm reflected light signals enter the 657nm servo feedback control circuit through the 657nm photoelectric detector, and the 657nm servo feedback control circuit regulates and controls the 657nm narrow-linewidth laser according to the optical cavity information to obtain the 657nm laser.
The 423nm narrow linewidth laser 3 is not particularly limited, and all devices capable of emitting 423nm narrow linewidth laser fall within the protection scope of the present invention. In some embodiments, the 423nm narrow linewidth laser 3 is selected from a narrow linewidth grating external cavity semiconductor laser or a narrow linewidth interference filter external cavity semiconductor laser.
The atomic beam tube 17, the half-wave plate 4, the polarization beam splitter prism 5, the electro-optical modulator 6, the signal source 7, the first photodetector 8, the signal amplifier 9, the mixer 10, the first servo feedback control circuit 11, the acousto-optical modulator 12, the second photodetector 13, and the second servo feedback control circuit 14 are not particularly limited, and the atomic beam tube 17, the half-wave plate 4, the polarization beam splitter prism 5, the electro-optical modulator 6, the signal source 7, the first photodetector 8, the signal amplifier 9, the mixer 10, the first servo feedback control circuit 11, the acousto-optical modulator 12, the second photodetector 13, and the second servo feedback control circuit 14, which are commonly used in the field, can be selected. In some embodiments, the first servo feedback control circuit 11, the second servo feedback control circuit 14, the signal amplifier 9, and the mixer 10 may be integrated circuit devices or discrete circuit devices; the signal source 7 may be a signal generator.
In the present invention, the second photodetector 13 may be the same as or different from the first photodetector 8, and the second servo feedback control circuit 14 may be the same as or different from the first servo feedback control circuit 11.
According to the atomic beam optical clock, 423nm transmitted light is externally modulated by the electro-optical modulator 6 before entering the atomic beam tube front window, so that extra frequency noise can be prevented from being introduced into the atomic beam optical clock, and the atomic beam optical clock with higher stability index can be formed. Particularly, the formed calcium atomic beam optical clock has good stability and excellent comprehensive performance, and can be carried, so that the calcium atomic beam optical clock can run outside a laboratory, and the application range of the calcium atomic beam optical clock is widened.
It will be appreciated that when other atoms are used, including strontium atoms, the wavelength of the laser need only be changed accordingly.
In the present invention, 423nm transmitted light is made to enter the atomic beam tube front window by providing a reflecting mirror, 423nm reflected light is made to enter the atomic beam light rear window, and modulated 657nm laser light is made to enter the atomic action region.
Specifically, the atomic beam clock may further include a first reflecting mirror 15, the 423nm transmitted light emitted from the polarization beam splitter 5 enters the first reflecting mirror 15, the first reflecting mirror 15 reflects the 423nm transmitted light, the optical path direction of the 423nm transmitted light is changed, and the 423nm transmitted light enters the atomic beam tube front window
The atomic beam optical clock further comprises a second reflecting mirror 16, 657nm laser emitted by the acousto-optic modulator 12 is emitted into the second reflecting mirror 16, the second reflecting mirror 16 reflects the modulated 657nm laser, the light path direction of the modulated 657nm laser is changed, and the modulated 657nm laser is emitted into an atomic action region.
The atomic beam clock may further include a third mirror, and 423nm reflected light emitted from the polarization beam splitter prism 5 enters the third mirror, and the third mirror reflects the 423nm reflected light, so that the optical path direction of the 423nm reflected light is changed, and the 423nm reflected light enters the atomic beam tube front window.
In the present invention, the first reflector 15, the second reflector 16, and the third reflector are not particularly limited, and reflectors commonly used in the art may be used, and the first reflector 15, the second reflector 16, and the third reflector may be the same or different.
In some embodiments of the present invention, the atomic beam optical clock further includes a beam splitter, the light exit end of the acousto-optic modulator 12 faces the beam splitter, 657nm laser enters the beam splitter through the acousto-optic modulator 12, and 657nm reflected light emitted from the beam splitter enters the atomic action region.
In the invention, 657nm laser emitted from the light outlet end of the acousto-optic modulator 12 enters the spectroscope, 657nm reflected light split by the spectroscope enters the atomic action region to interact with atoms, and 657nm transmitted light split by the spectroscope can be used for practical application.
The second aspect of the present invention provides a method for preparing an atomic beam optical clock with external modulation locking for probe light, the method for preparing the atomic beam optical clock comprises the following steps:
s1: the calcium atomic furnace 2 sprays calcium atoms to form calcium atomic beams, the atomic beam tube 17 is sleeved outside the calcium atomic beams, and the atomic beam tube 17 sequentially comprises an atomic beam tube front window, an atomic action area and an atomic beam tube rear window along the spraying direction;
s2: 423nm laser emitted from the light outlet end of the 423nm narrow linewidth laser 3 sequentially passes through the half-wave plate 4 and the polarization beam splitter prism 5 to obtain 423nm transmitted light and 423nm reflected light;
the electro-optical modulator 6 modulates 423nm transmitted light according to a modulation signal provided by the signal source 7, so that the modulated 423nm transmitted light enters a front window of the atomic beam tube to generate a first fluorescence signal;
the first fluorescence signal is detected and converted by using the first photoelectric detector 8 to obtain an electric signal, the electric signal sequentially passes through the first photoelectric detector 8 and the signal amplifier 9 and enters the mixer 10, and the mixer 10 performs frequency mixing processing on the demodulation signal provided by the signal source 7 and the electric signal to obtain an error signal;
the first servo feedback control circuit 11 performs feedback control on the 423nm narrow linewidth laser 3 according to the error signal;
s3: modulating 657nm laser emitted from the light outlet end of the 657nm ultrastable laser system 1 by using an acousto-optic modulator 12, so that the modulated 657nm laser enters an atomic action region;
s4: enabling 423nm reflected light to enter a rear window of the atomic beam tube to obtain a second fluorescent signal;
s5: a second fluorescence signal containing clock information is detected by using a second photodetector 13, the second fluorescence signal passes through the second photodetector 13 and enters a second servo feedback control circuit 14, and the acousto-optic modulator 12 is regulated and controlled by the second servo feedback control circuit 14 according to the second fluorescence signal.
Specifically, S1 includes: heating the calcium atomic furnace 2 to enable the calcium atomic furnace 2 to spray calcium atoms to form a calcium atomic beam, wherein the atomic beam tube 17 sleeved outside the calcium atomic beam sequentially comprises an atomic beam tube front window, an atomic action area and an atomic beam tube rear window along the atomic beam spraying direction.
S2 comprises the following steps: opening the 423nm narrow linewidth laser 3, enabling the 423nm narrow linewidth laser 3 to emit 423nm narrow linewidth laser, enabling the 423nm narrow linewidth laser to sequentially pass through the half-wave plate 4 and the polarization beam splitter prism 5, enabling the polarization beam splitter prism 5 to split the entered 423nm narrow linewidth laser, and enabling the 423nm narrow linewidth laser to be divided into two beams of 423nm transmission light and 423nm reflection light;
enabling 423nm transmitted light to be emitted into an electro-optical modulator 6, modulating the 423nm transmitted light by the electro-optical modulator 6 according to a modulation signal provided by a signal source 7, and emitting the 423nm transmitted light modulated by the electro-optical modulator 6 into the front window of the atomic beam tube in the step S1 to generate a first fluorescence signal;
then, a first photoelectric detector 8 is used for detecting and converting a first fluorescent signal generated in a front window of the atomic beam tube to obtain an electric signal, then a signal amplifier 9 is used for amplifying the electric signal, the amplified electric signal is input into a mixer 10, and the mixer 10 carries out mixing processing on a demodulation signal provided by a signal source and the amplified electric signal to obtain an error signal;
the error signal is input to the first servo feedback control circuit 11, and the first servo feedback control circuit 11 performs feedback control on the 423nm narrow linewidth laser 3 according to the error signal, so as to obtain more stable 423nm narrow linewidth laser, and further obtain more stable 423nm transmitted light and 423nm reflected light.
S3 comprises the following steps: opening the 657nm ultrastable laser system 1 to enable the 657nm ultrastable laser system 1 to emit 657nm laser, then injecting the 657nm laser into an acousto-optic modulator 12, modulating the 657nm laser by using the acousto-optic modulator 12, then injecting the modulated 657nm laser into an atomic action region, and enabling the modulated 657nm laser to interact with atoms in the atomic action region;
s4 comprises the following steps: enabling 423nm reflected light to enter a rear window of the atomic beam tube, and enabling the 423nm reflected light to continuously act with the atoms subjected to the 657nm laser action to form a second fluorescent signal;
s5 comprises the following steps: a second fluorescence signal is detected using a second photodetector 13, the second fluorescence signal passes through the second photodetector 13 into a second servo feedback control circuit 14, and the second servo feedback control circuit 14 modulates the acousto-optic modulator 12 according to the second fluorescence signal.
According to the preparation method of the atomic beam optical clock, the 423nm transmission light is modulated by the electro-optical modulator 6 outside the 423nm narrow-line-width laser 3, so that extra noise frequency can be prevented from being introduced into the atomic beam optical clock, the stability of the atomic beam optical clock can be improved, and the preparation method is simple to operate and is beneficial to wide application.
In some embodiments of the present invention, the atomic beam optical clock further includes a spectroscope for separating 657nm laser light emitted from the acousto-optic modulator 12 to obtain 657nm reflected light, and the 657nm reflected light enters the atomic action region.
In the invention, 657nm laser emitted from the light outlet end of the acousto-optic modulator 12 enters the spectroscope, 657nm reflected light split by the spectroscope enters the atomic action region to interact with atoms, and 657nm transmitted light split by the spectroscope can be used for practical application. Through the arrangement, 657nm laser can be regulated and controlled in real time, and 657nm laser with higher stability is output.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (14)
1. An atomic beam optical clock for detecting light using external modulation locking, comprising: 657nm ultrastable laser system, calcium atomic furnace, atomic beam tube, 423nm narrow linewidth laser, half-wave plate, polarization beam splitter prism, electro-optical modulator, first photoelectric detector, signal amplifier, mixer, first servo feedback control circuit, acousto-optical modulator, second photoelectric detector, signal source and second servo feedback control circuit;
the calcium atomic furnace sprays calcium atoms to form a calcium atomic beam, the atomic beam pipe is sleeved outside the calcium atomic beam, and the atomic beam pipe sequentially comprises an atomic beam pipe front window, an atomic action area and an atomic beam pipe rear window along the spraying direction;
the light outlet end of the 423nm narrow linewidth laser faces the half-wave plate, and the light outlet end of the half-wave plate faces the polarization beam splitter prism;
a first signal output end of the signal source is connected with a signal input end of the electro-optical modulator, 423nm transmitted light emitted by the polarization beam splitter prism enters a front window of the atomic beam tube through the electro-optical modulator to generate a first fluorescent signal;
a signal output end of the first photoelectric detector is connected with a signal input end of the signal amplifier, a signal output end of the signal amplifier is connected with a first signal input end of the frequency mixer, and a second signal output end of the signal source is connected with a second signal input end of the frequency mixer;
the first photoelectric detector is configured to detect and convert the first fluorescent signal to obtain an electric signal, and the electric signal is processed by the signal amplifier and the frequency mixer in sequence to obtain an error signal;
the signal output end of the mixer is connected with the signal input end of the first servo feedback control circuit, the signal output end of the first servo feedback control circuit is connected with the signal input end of the 423nm narrow linewidth laser, and the first servo feedback control circuit performs feedback control on the 423nm narrow linewidth laser according to the error signal;
the light outlet end of the 657nm ultrastable laser system faces the acousto-optic modulator, and 657nm emergent light emitted by the acousto-optic modulator enters the atomic action region;
423nm reflected light emitted by the polarization beam splitter prism enters the rear window of the atomic beam tube to obtain a second fluorescent signal;
the signal output end of the second photodetector is connected with the signal input end of the second servo feedback control circuit, the signal output end of the second servo feedback control circuit is connected with the signal input end of the acousto-optic modulator, the second photodetector is configured to detect the second fluorescent signal, and the second servo feedback control circuit is used for regulating and controlling the acousto-optic modulator according to the second fluorescent signal.
2. The atomic beam optical clock of claim 1, wherein the signal source comprises a signal generator.
3. The atomic beam clock according to any one of claims 1-2, further comprising a first mirror for directing the 423nm transmitted light into the atomic beam tube front window.
4. The atomic beam optical clock according to any one of claims 1-2, further comprising a second mirror for injecting the 657nm laser light modulated by the acousto-optic modulator into the atomic action region.
5. The atomic beam optical clock of claim 3, further comprising a second mirror for injecting the 657nm laser light modulated by the acousto-optic modulator into the atomic action region.
6. The atomic beam clock according to any one of claims 1-2 and 5, further comprising a third mirror for making the 423nm reflected light enter the atomic beam tube rear window.
7. The atomic beam clock of claim 3, further comprising a third mirror for directing the 423nm reflected light into the atomic beam tube back window.
8. The atomic beam clock according to any one of claims 1-2, 5, and 7, wherein the 423nm narrow linewidth laser is selected from a narrow linewidth grating external cavity semiconductor laser or a narrow linewidth interference filter external cavity semiconductor laser.
9. The atomic beam clock of claim 3, wherein the 423nm narrow linewidth laser is selected from a narrow linewidth grating external cavity semiconductor laser or a narrow linewidth interference filter external cavity semiconductor laser.
10. The atomic beam clock according to any one of claims 1-2, 5, 7, and 9, further comprising a beam splitter, wherein the light-emitting end of the acousto-optic modulator faces the beam splitter, 657nm laser enters the beam splitter through the acousto-optic modulator, and 657nm reflected light emitted from the beam splitter enters the atomic action region.
11. The atomic beam clock according to claim 3, further comprising a beam splitter, wherein the light-emitting end of the acousto-optic modulator faces the beam splitter, 657nm laser enters the beam splitter through the acousto-optic modulator, and 657nm reflected light emitted from the beam splitter enters the atomic action region.
12. A method for manufacturing an atomic beam optical clock using external modulation locking for probe light, the method being used for manufacturing an atomic beam optical clock according to any one of claims 1 to 11, comprising the steps of:
calcium atoms are sprayed by a calcium atomic furnace to form a calcium atomic beam, an atomic beam pipe is sleeved outside the calcium atomic beam, and the atomic beam pipe sequentially comprises an atomic beam front window, an atomic action zone and an atomic beam rear window along the spraying direction;
423nm laser emitted from the light outlet end of the 423nm narrow linewidth laser sequentially passes through a half-wave plate and a polarization beam splitter prism to obtain 423nm transmitted light and 423nm reflected light;
the electro-optical modulator modulates the 423nm transmitted light according to a modulation signal provided by a signal source, so that the 423nm transmitted light after modulation enters a front window of the atomic beam tube to form a first fluorescence signal;
detecting and converting the first fluorescent signal by using a first photoelectric detector and converting the first fluorescent signal into an electric signal, wherein the electric signal sequentially enters a mixer through a signal amplifier, and the mixer mixes a demodulation signal provided by a signal source with the electric signal to obtain an error signal;
the first servo feedback control circuit performs feedback control on the 423nm narrow linewidth laser according to the error signal;
modulating 657nm laser emitted from a light outlet end of a 657nm ultrastable laser system by using an acousto-optic modulator, so that the modulated 657nm laser enters the atomic action region;
enabling the 423nm reflected light to enter a rear window of the atomic beam tube to obtain a second fluorescent signal;
and detecting the second fluorescent signal by using a second photoelectric detector, wherein the second fluorescent signal enters the second servo feedback control circuit through the second photoelectric detector, and the second servo feedback control circuit regulates and controls the acousto-optic modulator according to the second fluorescent signal.
13. The method for manufacturing an atomic beam optical clock according to claim 12, wherein the signal source includes a signal generator.
14. The method for manufacturing an atomic beam clock according to claim 12 or 13, further comprising using a beam splitter to split 657nm laser light emitted from the acousto-optic modulator to obtain 657nm reflected light, wherein the 657nm reflected light enters the atomic action region.
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