JPS63191417A - Laser-exciting type cesium atom oscillator - Google Patents

Abstract

PURPOSE:To obtain a small-sized oscillator which operates stably by guiding exciting light outputted by a laser for excitation by using optical fibers, etc., and projecting it on an atom beam. CONSTITUTION:An optical branching element 11 is provided to branch the laser light for excitation outputted by the laser 2 for excitation into light for level selection and light for resonance detection, which are guided to an atom beam tube by optical fibers 12 and 13. The guided light beams are collimated by lenses 14 and 15 and then while the light for level selection is projected on the atom beam in a level selection area D1 before it enters a cavity resonator 3, the light for resonance detection is projected on the atom beam in a resonance detection area D2 after it exits from the cavity resonator 3. Consequently, the laser light for excitation is transmitted by a solid element, i.e. wire, so the oscillator operates stably against external vibrations.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser-excited cesium atomic oscillator equipped with an optical system capable of realizing stable atomic beam excitation operation.

[Prior Art] A cesium atomic oscillator uses the transition frequency between electronic energy levels in the hyperfine structure of a cesium atom as a reference.
This is an oscillator that obtains an extremely stable frequency by stabilizing the oscillation frequency of the oscillator. The transition frequency used in this atomic oscillator is the level specified by the total angular momentum quantum number F = 4 and the total magnetic quantum number mF = 0 among the hyperfine levels of the ground state of cesium +33, and the total angular momentum quantum number mF = 0. The frequency ν corresponds to the energy difference between the level specified by the number F=3 and the total magnetic quantum number mF=0. (9,19263
G11z) is used. This is because this transition is least influenced by the Zeeman effect due to external magnetic fields.

Then, in order to detect the transition of the two level difference, one of the hyperfine levels (F = 3, F = 4) of the above ground state was selected, and a cesium atom using a deflecting magnet to detect the transition atom. Oscillators are currently in use.

In contrast to such conventional cesium atomic oscillators, a laser-excited cesium atomic oscillator as shown in FIG. 4 has been proposed (see, for example, Japanese Patent Application No. 61-241766).
. In the figure, reference numeral 1 denotes an atomic beam generating reactor, which generates an atomic beam whose electron energy level is at the ground state level F=3 or F=4. This atomic beam is irradiated with laser light output from the excitation laser 2 in the level selection region DI. That is, the laser beam is collimated by a lens 2a, and then branched by a half mirror 2b into light for level selection and light for resonance detection,
The former is sent to the level selection region D1 and is irradiated with the atomic beam emitted from the atomic beam generator l, and the latter is sent to the resonance detection region D2 via the mirror 2C and is irradiated with the atomic beam emitted from the atomic beam generator l.
irradiated by an atomic beam emitted from the

The laser beam is linearly polarized, and its polarization direction is parallel to the C magnetic field. In this case, the ground state level F = 3
．． The atoms in each sub-level of 4 repeatedly absorb light and spontaneously emit light, and concentrate at the ground state level F-4 mF=0.

Therefore, the cavity resonator 3 has a ground state level F=4. m
Only atoms with F=0 arrive. The cavity resonator 3 has a frequency ν. Excited by nearby microwaves. Therefore, the atoms that reached the cavity resonator 3 resonate with this microwave inside the cavity resonator 3, and the level F = 4, mF = 0.
→ Level F-3, which causes stimulated emission of mP=O. In other words, atoms that have transitioned from the ground level F = 4, mF = O to the ground level F = 3, mF = 0 are emitted from the cavity resonator 3.

As described above, this atom is irradiated with light from the excitation laser 2 in the resonance detection region D2, and is excited to an excitation level of -3=F=4. The photodetector 4 measures the intensity of spontaneously emitted light when electrons fall from this excited level to the ground level again. In this case, the output of the photodetector 4 corresponds to the number of atoms that caused the stimulated emission, in other words, the resonance output. In other words, the photodetector 4 functions as a resonance detector.

The microwave is modulated by a phase modulator 6 using the output of a low frequency oscillator 5, and has a frequency ν. Sweeps around the center. At this time, the detection signal output from the photodetector 4 uses the output of the low frequency oscillator 5 as a reference signal.
A synchronous detector 7 performs synchronous detection. This synchronous detection output is
It corresponds to the differential value of the resonance output detected by the photodetector 4, and the frequency of the microwave is the frequency ν. It becomes 0 when it matches, that is, when the resonance output reaches a maximum. When the synchronous detection output is supplied to the VCO control unit 8, the vCO control unit 8 determines that the frequency of the microwave is a value ν based on the supplied signal.

The voltage controlled oscillator (VCO) 9 is controlled so as to match the . The output of the VCO 9 is multiplied by a frequency multiplier 10 so that the frequency is ν. is converted into microwave. Then, the output of the VCO 9 is taken out as a desired frequency-stabilized output.

Note that the output frequency of the low frequency oscillator 5 is approximately 100
I-Iz. In addition, in FIG. 4, the C magnetic field applied to the cavity resonator 3 is applied to the magnetic side level m of the cesium atom.
This is for separating F, and separates the energy level of mF=0 from the energy level of mF≠0.

[Problems to be Solved by the Invention] However, the above-described laser-excited cesium atomic oscillator has the following drawbacks.

(2) Since laser light is propagated through the air using individual optical components such as the half mirror 2b and the mirror 2c, it is susceptible to external mechanical vibrations and operation becomes unstable.

■For the same reason as (■) above, there is a lack of flexibility in system configuration. Therefore, a laser-excited cesium atomic oscillator using such an excitation optical system is not suitable for a small, portable atomic oscillator.

The present invention was made against this background, and an object of the present invention is to provide a small and portable laser-excited cesium atomic oscillator that operates stably even against external vibrations.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides an atomic beam generation reactor that generates a cesium atomic beam, an excitation laser that irradiates the atomic beam with light, and an excitation laser that irradiates the atomic beam with light. A cavity resonator that causes cesium atoms brought to a certain electronic energy level by light to resonate using microwaves; a photodetector that detects the intensity of the resonance; and a photodetector that detects the intensity of the resonance based on the output of the photodetector. A laser-pumped cesium atomic oscillator comprising an oscillator controller that stabilizes the oscillation frequency of the voltage-controlled oscillator and a frequency multiplier that generates the microwave based on the output of the voltage-controlled oscillator. It is characterized by comprising an optical system having a light branching means for branching the output light and an optical fiber for guiding the branched light to a predetermined irradiation area.

Further, an optical coupling means is provided on one side of the laser beam branched by the optical branching means for coupling this laser beam with another excitation laser beam having a different wavelength, and a laser beam of two wavelengths output from the optical coupling means is provided. The method is characterized in that the atomic beam is excited by light before entering the cavity.

"Operation" According to the above means, the laser beam for excitation is transmitted by a solid-state element in a so-called wired manner. Therefore, it is possible to operate stably against external vibrations. Also,
Since light is transmitted through optical fiber, configuration regulations are reduced.
A flexible excitation optical system can be constructed.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an excitation optical system according to a first embodiment of the present invention. In this figure, components 1 to
4 is similar to a laser-excited cesium atomic oscillator not shown in FIG. Moreover, illustration of components 5 to 10 is omitted. This embodiment differs from the atomic oscillator shown in FIG. 4 in the following points.

(2) An optical branching element 11 is provided so that the excitation laser beam output from the excitation laser 2 is divided into two beams: level selection light and resonance detection light.

■The branched light is guided to the atomic beam tube using optical fibers 12 and 13.

■The guided light is transmitted through the lens 14. ．． After collimating in step 15, the light for level selection irradiates the atomic beam before entering the cavity resonator 3 in the level selection region D1, and the light for resonance detection irradiates the atomic beam in the resonance detection region D2. The point is that the atomic beam after exiting from the body resonator 3 is irradiated.

FIG. 3(a) is a diagram showing an example of the configuration of the optical branching element 11 described in "1", in which a semiconductor laser (LD) is used as the excitation laser 2.
A waveguide type device is used as the optical branching element 11, and these are integrated. As a waveguide type device, there is a device in which Ti is diffused into a LiNbo 3 substrate to form a waveguide.

According to such a configuration, the light emitted from the excitation laser 2 is split into two by the optical branching element If, and sent to the lenses 14 and 15 via the optical fiber +2.13.

The light collimated by the lens 14 is applied to the atomic beam in the level selection region D1, and the light collimated by the lens 15 is applied to the atomic beam in the resonance detection region D2.

In this way, the excitation light is transmitted through a solid-state element such as an optical fiber, so the operation is stable against external vibrations.
Miniaturization can be achieved.

Next, FIG. 2 shows the configuration of an excitation optical system according to a second embodiment of the present invention. This second embodiment is a laser-excited cesium atomic oscillator that excites an atomic beam with light of two wavelengths.

This second embodiment differs from the first embodiment in the following points.

■An optical coupling element 21 is interposed between the output end of the optical branching element II and the optical fiber 12, and the first laser beam for level selection outputted from the optical branching element 11 is connected to the optical coupling element 21. 1st
The point where it is supplied to the input end.

■The excitation laser 2 is connected to the second input end of the optical coupling cable 21.
The point is that the second light for level selection outputted from 2 is manually operated.

Note that the wavelengths of these eleventh and second lights are different; for example, the first laser light excites the cesium atom at the ground level F=3 to the excitation level F=4, and the wavelength of the second laser light is different. The laser beam excites the cesium atom at the ground level F=4 to the excited level F
' = 4.

FIG. 3(b) shows a device in which semiconductor lasers are used as the excitation lasers 2 and 22, waveguide type devices are used as the optical branching element 11 and the optical coupling element 21, and these are integrated. This device is also manufactured in the same manner as the waveguide type device 7 shown in FIG.

In such a configuration, the laser beam output from the excitation laser 2 is branched into two in the optical branching element ll.

Among the branched lights, the light for level selection is combined with the laser light from another excitation laser 22 in the optical coupling element 2I, guided by the optical fiber I2, and passed through the lens 1.
4, and the atomic beam 7 is irradiated in the level selection region DI before entering the cavity resonator 3. On the other hand, the light for resonance detection is guided to the resonance detection region D2 via the optical fiber 13 and the lens 15, and is applied to the atomic beam after exiting the cavity resonator 3.

In each of the above embodiments, if a polarization-maintaining fiber is used as the optical fiber 12.degree. 13, the atomic beam can be irradiated with light while reliably maintaining the polarization.

[Effects of the Invention] As explained below, in this invention, the excitation light output from the excitation laser is guided using an optical fiber or the like and irradiated to the atomic beam, so that the operation is improved. It is possible to create a stable and compact laser-excited cesium atomic oscillator. Therefore, it can be widely used as a portable atomic oscillator that is easy to handle.

[Brief explanation of the drawing]

1 and 2 are blocks showing the configuration of a pumping optical system of a laser-pumped cesium side oscillator according to a first embodiment and a second embodiment of the present invention, and FIG. 3 shows a semiconductor laser, an optical branch, and an optical system. This figure shows an example of integrating coupling elements.
Figure a) is used in the first embodiment, and Figure (b) is used in the second embodiment. FIG. 4 is a block diagram showing the configuration of a known laser-excited cesium atomic oscillator. l...Atomic beam generator, 2.22...Excitation laser, 3...Cavity resonator, 4...Photodetector, 5...・Low frequency oscillator, 6... Phase modulator, 7... Synchronous detector, 8... ■ CO control section, 9... VCO (voltage controlled oscillator), lO・・
... Frequency multiplier, 11... Optical branching element, 12.13...
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Claims (2)

[Claims] (1) an atomic beam generator that generates a cesium atomic beam; an excitation laser that irradiates the atomic beam with light;
A cavity resonator that uses microwaves to resonate the cesium atoms brought to a certain electronic energy level by this light, a photodetector that detects the intensity of the resonance, and a A laser-pumped cesium atomic oscillator comprising: an oscillator controller that stabilizes the oscillation frequency of the voltage-controlled oscillator; and a frequency multiplier that generates the microwave based on the output of the voltage-controlled oscillator. 1. A laser-excited cesium atomic oscillator, comprising an optical system having an optical branching means for branching light output from the oscillator, and an optical fiber for guiding the branched light to a predetermined irradiation area. (2) An optical coupling means is provided on one side of the laser beam branched by the optical branching means to couple this laser beam with another excitation laser beam having a different wavelength, and the two wavelengths output from this optical coupling means are 2. The laser-excited cesium atomic oscillator according to claim 1, wherein the atomic beam before entering the cavity is excited by a laser beam.