JP6264876B2 - Quantum interference devices, atomic oscillators, and electronic equipment - Google Patents

Description

  The present invention relates to a quantum interference device, an atomic oscillator, an electronic device, and a moving object.

As an oscillator having long-term highly accurate oscillation characteristics, an atomic oscillator that oscillates based on energy transition of alkali metal atoms such as rubidium and cesium is known (for example, see Patent Document 1).
In general, the operating principles of atomic oscillators are broadly divided into methods that use the double resonance phenomenon of light and microwaves, and methods that use the quantum interference effect (CPT: Coherent Population Trapping) of two types of light with different wavelengths. However, since an atomic oscillator using the quantum interference effect can be made smaller than an atomic oscillator using a double resonance phenomenon, it is expected to be mounted on various devices in recent years.

  An atomic oscillator using the quantum interference effect includes, for example, a gas cell in which gaseous metal atoms are sealed, and two types of resonance light having different frequencies in the metal atoms in the gas cell, as disclosed in Patent Document 1. A light emitting part (light source) for irradiating laser light, a light detecting part for detecting laser light transmitted through the gas cell, and an optical component provided between the light emitting part and the gas cell are provided. In such an atomic oscillator, when the frequency difference between the two types of resonance light is a specific value, both types of resonance light are transmitted without being absorbed by the metal atoms in the gas cell (EIT) : Electromagnetically Induced Transparensy) phenomenon, but an EIT signal, which is a steep signal generated with the EIT phenomenon, is detected by a photodetector.

In general, most of the laser light directed to the light detection unit is incident on the light detection unit, but a part of the laser light is reflected by the light detection unit and is directed to the light emission unit as reflected light. When the reflected light is incident on the gas cell, there is a possibility that the S / N ratio of the resonance signal is lowered or the resonance contrast is lowered.
Therefore, in the atomic oscillator described in Patent Document 1, an optical isolator is provided as a light amount reducing means in order to suppress deterioration of the characteristics of the atomic oscillator caused by reflected light entering the gas cell. This optical isolator is provided between the gas cell and the light detection unit, and attenuates the amount of reflected light incident on the gas cell to suppress the deterioration of the characteristics of the atomic oscillator.
However, the laser light emitted from the light emitting part is also reflected when entering the gas cell. For this reason, the reflected light reflected by the gas cell may be incident on the light emitting portion as it is. When this reflected light enters the light emitting part, the frequency of the laser light emitted from the light emitting part becomes unstable. As a result, there is a problem that the frequency stability of the atomic oscillator is lowered.

JP 2010-283461 A

  An object of the present invention is to provide a quantum interference device, an atomic oscillator, an electronic device, and a moving body that can suppress light emitted from a light source from being reflected by each portion and incident on the light source and having excellent frequency stability. There is to do.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Application Example 1]
The quantum interference device of the present invention includes a gas cell in which metal atoms are sealed,
A light source that emits light including a resonant light pair in the metal atom;
An optical element provided between the gas cell and the light source,
The surface of the optical element on the gas cell side is inclined with respect to a line segment connecting the light source and the gas cell.

  A part of the light emitted from the light source may be reflected by, for example, a gas cell and directed to the light source. However, the surface on the gas cell side of the optical element provided between the gas cell and the light source is inclined with respect to a line segment connecting the light source and the gas cell. Thereby, the light reflected by the gas cell and directed toward the light source is reflected by the surface of the optical element on the gas cell side. Therefore, it can suppress that the light which reflects in a gas cell and goes to a light source enters into a light source. As a result, it is possible to suppress a decrease in frequency stability of the light source caused by light that is reflected by the gas cell and directed toward the light source entering the light source. Therefore, the quantum interference device of the present invention has excellent frequency stability.

[Application Example 2]
In the quantum interference device of the present invention, it is preferable that the surface of the optical element on the light source side is inclined with respect to a line segment connecting the light source and the gas cell.
Thereby, out of the light reflected by the gas cell and directed to the light source, the light directed to the light source without being reflected by the gas cell side surface of the optical element can be reflected by the light source side surface of the optical element. Therefore, it can suppress more effectively that the light which reflects in a gas cell and goes to a light source enters into a light source.

[Application Example 3]
In the quantum interference device according to the aspect of the invention, it is preferable that the optical element is a neutral density filter.
Thereby, the light quantity which is not reflected by the surface by the side of the gas cell of an optical element among the light which reflects in a gas cell and goes to a light source can be attenuated.
[Application Example 4]
In the quantum interference device of the present invention, an optical element group including the optical element is disposed between the light source and the gas cell,
The optical element is preferably arranged on the light source side most in the optical element group.
As a result, the oscillation characteristics of the atomic oscillator can be improved as much as the optical element group is provided, and the reflected light is prevented from entering the light source by optical components other than the optical element in the optical element group. can do.

[Application Example 5]
In the quantum interference device of the present invention, it is preferable that the inclination angle θ1 of the surface on the gas cell side of the optical element with respect to a line segment connecting the light source and the gas cell is 80 ° or less.
Thereby, the effect of this invention can be exhibited notably.
[Application Example 6]
In the quantum interference device of the present invention, the inclination angle θ2 of the surface on the light source side of the optical element with respect to the line segment connecting the light source and the gas cell is larger than the radiation angle θ3 of the light emitted from the light source. preferable.
Thereby, it can suppress that the radial light radiate | emitted from the light source reflects in the surface at the side of the light source of an optical element, and injects into a light source.

[Application Example 7]
In the quantum interference device according to the aspect of the invention, it is preferable that the optical element has a portion in which the surface on the gas cell side and the surface on the light source side are parallel.
Thereby, manufacture of an optical element becomes easy.
[Application Example 8]
In the quantum interference device according to the aspect of the invention, it is preferable that the gas cell side surface of the optical element is inclined with respect to the light source side surface of the optical element.
Thereby, the inclination angle of the light source side surface and the gas cell side surface of the optical element can be appropriately set.

[Application Example 9]
The atomic oscillator according to the present invention includes the quantum interference device according to the present invention.
Thereby, an atomic oscillator having excellent reliability can be provided.
[Application Example 10]
An electronic apparatus according to the present invention includes the quantum interference device according to the present invention.
Thereby, an electronic device with excellent reliability can be provided.
[Application Example 11]
The moving body of the present invention includes the quantum interference device of the present invention.
Thereby, the moving body excellent in reliability can be provided.

It is a schematic diagram which shows schematic structure of the atomic oscillator (quantum interference apparatus) which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the energy state of an alkali metal. It is a graph which shows the relationship between the frequency difference of two light radiate | emitted from a light-projection part, and the intensity | strength of the light detected by a photon detection part. It is a perspective view of the atomic oscillator (quantum interference apparatus) shown in FIG. It is a schematic diagram for demonstrating the light emission part and gas cell part with which the atomic oscillator shown in FIG. 1 is provided. It is a schematic diagram for demonstrating the optical element group with which the atomic oscillator shown in FIG. 1 is provided. FIG. 7 is an enlarged detail view showing a first unit and an optical element in FIG. 6. It is an enlarged detail drawing which shows the 1st unit and optical element with which the atomic oscillator (quantum interference apparatus) which concerns on 2nd Embodiment of this invention is provided. It is a figure which shows schematic structure at the time of using the atomic oscillator (quantum interference apparatus) of this invention for the positioning system using a GPS satellite. It is a figure which shows an example of the moving body of this invention.

Hereinafter, a quantum interference device, an atomic oscillator, an electronic device, and a moving body of the present invention will be described in detail based on embodiments shown in the accompanying drawings.
1. Atomic oscillator (quantum interference device)
First, the atomic oscillator of the present invention (the atomic oscillator including the quantum interference device of the present invention) will be described. In the following, an example in which the quantum interference device of the present invention is applied to an atomic oscillator will be described. However, the quantum interference device of the present invention is not limited to this, for example, a magnetic sensor, a quantum memory, etc. It is also applicable to.

<First Embodiment>
FIG. 1 is a schematic diagram showing a schematic configuration of an atomic oscillator (quantum interference device) according to the first embodiment of the present invention. 2 is a diagram for explaining the energy state of the alkali metal, and FIG. 3 is a relationship between the frequency difference between the two lights emitted from the light emitting part and the intensity of the light detected by the light detecting part. It is a graph which shows.

An atomic oscillator 1 shown in FIG. 1 is an atomic oscillator using a quantum interference effect.
As shown in FIG. 1, the atomic oscillator 1 includes a first unit (light source) 2 that is a light emission side unit, a second unit 3 that is a light detection side unit, a first unit 2 and a second unit. 3 and an optical component group (optical element group) 4 provided between the first unit 2 and the second unit 3.

Here, the first unit 2 includes a light emitting unit 21 and a first package 22 that houses the light emitting unit 21.
The second unit 3 includes a gas cell 31, a light detection unit 32, a heater 33, a temperature sensor 34, a coil 35, a second package 36 that stores these, and a magnetic shield that stores the second package 36. 38.
The optical component group 4 includes an ND filter 41, a lens 42, and a polarization filter 43.

First, the principle of the atomic oscillator 1 will be briefly described.
As shown in FIG. 1, in the atomic oscillator 1, the light emitting unit 21 emits the excitation light LL toward the gas cell 31, and the light detection unit 32 detects the excitation light LL transmitted through the gas cell 31.
A gaseous alkali metal (metal atom) is enclosed in the gas cell 31, and the alkali metal has energy levels of a three-level system and has different energy levels as shown in FIG. Three ground states (ground states 1 and 2) and an excited state can be taken. Here, the ground state 1 is a lower energy state than the ground state 2.

The excitation light LL emitted from the light emitting unit 21 includes two types of resonance lights 1 and 2 having different frequencies. The two types of resonance lights 1 and 2 are irradiated onto the gaseous alkali metal as described above. Then, the optical absorptance (light transmittance) of the resonant lights 1 and 2 in the alkali metal changes according to the difference (ω1−ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2.
When the difference (ω1−ω2) between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 matches the frequency corresponding to the energy difference between the ground state 1 and the ground state 2, the ground states 1 and 2 Each excitation to the excited state stops. At this time, both the resonant lights 1 and 2 are transmitted without being absorbed by the alkali metal. Such a phenomenon is called a CPT phenomenon or an electromagnetically induced transparency (EIT) phenomenon.

  For example, when the light emitting unit 21 fixes the frequency ω1 of the resonant light 1 and changes the frequency ω2 of the resonant light 2, the difference between the frequency ω1 of the resonant light 1 and the frequency ω2 of the resonant light 2 (ω1-ω2). ) Coincides with the frequency ω 0 corresponding to the energy difference between the ground state 1 and the ground state 2, the detection intensity of the light detection unit 32 increases sharply as shown in FIG. Such a steep signal is detected as an EIT signal. This EIT signal has an eigenvalue determined by the type of alkali metal. Therefore, an oscillator can be configured by using such an EIT signal.

Hereinafter, a specific configuration of the atomic oscillator 1 of the present embodiment will be described.
4 is a perspective view of the atomic oscillator (quantum interference device) shown in FIG. 1, FIG. 5 is a schematic diagram for explaining a light emitting part and a gas cell part included in the atomic oscillator shown in FIG. 1, and FIG. FIG. 7 is a schematic diagram for explaining an optical element group included in the atomic oscillator shown in FIG. 1, and FIG. 7 is an enlarged detailed view showing the first unit and optical elements in FIG. In the following, the upper side of FIGS. 5 to 7 is also referred to as “upper” and the lower side of FIG. 5 is also referred to as “lower”. 4 to 6, only the principal ray (optical axis) of the excitation light LL is illustrated for easy understanding (the same applies to FIG. 8).

Hereinafter, each part of the atomic oscillator 1 will be described in detail sequentially.
(First unit)
As described above, the first unit 2 includes the light emitting unit 21 and the first package 22 that houses the light emitting unit 21.
[Light emitting part]
The light emitting unit 21 has a function of emitting excitation light LL that excites alkali metal atoms in the gas cell 31.

More specifically, the light emitting unit 21 emits light including two types of light (resonant light 1 and resonant light 2) having different frequencies as described above as excitation light LL.
The frequency ω1 of the resonant light 1 can excite (resonate) the alkali metal in the gas cell 31 from the ground state 1 to the excited state.
Further, the frequency ω2 of the resonance light 2 can excite (resonate) the alkali metal in the gas cell 31 from the ground state 2 to the excited state.

The light emitting unit 21 is not particularly limited as long as it can emit the excitation light LL as described above. For example, a semiconductor laser such as a vertical cavity surface emitting laser (VCSEL) can be used. .
Further, such a light emitting portion 21 is temperature-controlled to a predetermined temperature by a temperature adjusting element (a heating resistor, a Peltier element, etc.) not shown.

[First package]
The first package 22 houses the light emitting unit 21 described above.
As shown in FIG. 4, the first package 22 includes a housing whose outer shape forms a block shape. Further, for example, a plurality of leads (not shown) protrude from the first package 22, and these are electrically connected to the light emitting unit 21 through wiring. Each lead is electrically connected to the wiring board by a connector or the like (not shown). As this connector, for example, a flexible board or a socket-shaped one can be used.

A window 23 is provided on the wall of the first package 22 on the second unit 3 side. This window part 23 is provided on the optical axis (optical axis of the excitation light LL) a between the gas cell 31 and the light emitting part 21. And the window part 23 has transparency with respect to the excitation light LL mentioned above.
The window 23 is not particularly limited as long as it has transparency to the excitation light LL. For example, the window 23 may be a lens, for example, other than a lens such as a simple light-transmissive plate member. It may be an optical component.
The constituent material of the portion other than the window portion 23 of the first package 22 is not particularly limited, and for example, ceramic, metal, resin, or the like can be used.

  Here, when a portion other than the window portion 23 of the first package 22 is made of a material that is transparent to excitation light, the portion other than the window portion 23 of the first package 22 and the window portion 23 are integrated. Can be formed. Further, when a portion other than the window portion 23 of the first package 22 is made of a material that is not transmissive to excitation light, the portion other than the window portion 23 of the first package 22 and the window portion 23 are separated. These may be formed by a body, and these may be joined by a known joining method.

Moreover, it is preferable that the inside of the 1st package 22 is an airtight space. Thereby, the inside of the 1st package 22 can be made into a pressure reduction state or an inert gas enclosure state, As a result, the characteristic of the atomic oscillator 1 can be improved.
The first package 22 houses a temperature adjusting element, a temperature sensor, and the like that adjust the temperature of the light emitting unit 21 (not shown). Examples of such temperature adjusting elements include heating resistors (heaters), Peltier elements, and the like.
According to such a first package 22, the light emitting part 21 can be accommodated in the first package 22 while allowing the excitation light to be emitted from the light emitting part 21 to the outside of the first package 22.

(Second unit)
As described above, the second unit 3 stores the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, the coil 35, the second package 36 that stores them, and the second package 36. And a magnetic shield 38.
[Gas cell]
The gas cell 31 is filled with gaseous alkali metals such as rubidium, cesium, and sodium. Further, in the gas cell 31, a rare gas such as argon or neon, or an inert gas such as nitrogen may be sealed together with an alkali metal gas as a buffer gas, if necessary.

For example, as shown in FIG. 5, the gas cell 31 includes a main body 311 having a columnar through hole 311 a and a pair of windows 312 and 313 that block both openings of the through hole 311 a. Thereby, the internal space S in which the alkali metal as described above is enclosed is formed.
The material constituting the main body 311 is not particularly limited, and examples thereof include a metal material, a resin material, a glass material, a silicon material, and a crystal. From the viewpoint of workability and bonding with the window portions 312 and 313, glass is used. It is preferable to use a material or a silicon material.

The window portions 312 and 313 are airtightly joined to the main body portion 311. Thereby, the internal space S of the gas cell 31 can be made into an airtight space.
The bonding method between the main body 311 and the window portions 312 and 313 is determined according to these constituent materials and is not particularly limited. For example, a bonding method using an adhesive, a direct bonding method, an anodic bonding method, and the like. Can be used.

In addition, the material constituting the windows 312 and 313 is not particularly limited as long as it has transparency to the excitation light LL as described above, and examples thereof include silicon materials, glass materials, and crystals.
Each of such window portions 312 and 313 has transparency to the excitation light LL from the light emitting portion 21 described above. One window 312 transmits the excitation light LL incident on the gas cell 31, and the other window 313 transmits the excitation light LL emitted from the gas cell 31.
The gas cell 31 is heated by a heater 33 and the temperature is adjusted to a predetermined temperature.

[Photodetection section]
The light detection unit 32 has a function of detecting the intensity of the excitation light LL (resonance light 1 and 2) transmitted through the gas cell 31.
The light detector 32 is not particularly limited as long as it can detect the excitation light as described above. For example, a photodetector (light receiving element) such as a solar cell or a photodiode can be used.

[heater]
The heater 33 has a function of heating the above-described gas cell 31 (more specifically, an alkali metal in the gas cell 31). Thereby, the alkali metal in the gas cell 31 can be maintained in a gaseous state with a desired concentration.
The heater 33 generates heat when energized. For example, the heater 33 includes a heating resistor provided on the outer surface of the gas cell 31. Such a heating resistor is formed using, for example, a chemical vapor deposition method (CVD) such as plasma CVD or thermal CVD, a dry plating method such as vacuum deposition, a sol-gel method, or the like.

Here, when the heating resistor is provided at the entrance or exit of the excitation light LL of the gas cell 31, a material having transparency to the excitation light, specifically, for example, ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), In ₃ O ₃ , SnO ₂ , Sb-containing SnO ₂ , and transparent electrode materials such as oxides such as Al-containing ZnO.

The heater 33 is not particularly limited as long as it can heat the gas cell 31, and may be non-contact with the gas cell 31. Further, the gas cell 31 may be heated using a Peltier element instead of the heater 33 or in combination with the heater 33.
Such a heater 33 is electrically connected to a temperature control unit 62 of the control unit 6 to be described later, and energization is controlled.

[Temperature sensor]
The temperature sensor 34 detects the temperature of the heater 33 or the gas cell 31. Based on the detection result of the temperature sensor 34, the amount of heat generated by the heater 33 is controlled. Thereby, the alkali metal atom in the gas cell 31 can be maintained at a desired temperature.

The installation position of the temperature sensor 34 is not particularly limited, and may be, for example, on the heater 33 or on the outer surface of the gas cell 31.
The temperature sensor 34 is not particularly limited, and various known temperature sensors such as a thermistor and a thermocouple can be used.
Such a temperature sensor 34 is electrically connected to a temperature control unit 62 of the control unit 6 which will be described later via a wiring (not shown).

[coil]
The coil 35 has a function of generating a magnetic field in the direction (parallel direction) along the optical axis a of the excitation light LL in the internal space S by energization. Thereby, by Zeeman splitting, the gap between different energy levels in which the alkali metal atoms existing in the internal space S are degenerated can be widened, the resolution can be improved, and the line width of the EIT signal can be reduced.
The magnetic field generated by the coil 35 may be either a DC magnetic field or an AC magnetic field, or may be a magnetic field in which a DC magnetic field and an AC magnetic field are superimposed.

The installation position of the coil 35 is not particularly limited and is not shown. For example, the coil 35 may be wound around the outer periphery of the gas cell 31 so as to constitute a solenoid type, or may constitute a Helmholtz type. A pair of coils may be opposed to each other via the gas cell 31.
The coil 35 is electrically connected to a magnetic field control unit 63 of the control unit 6 described later via a wiring (not shown). Thereby, the coil 35 can be energized.

[Second package]
The second package 36 is configured by a housing whose outer shape forms a block shape, and houses the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 described above. The second package 36 directly or indirectly supports the gas cell 31, the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 inside.

A window 37 is provided on the wall of the second package 36 on the first unit 2 side. This window part 37 is provided on the optical axis a between the gas cell 31 and the light emitting part 21. And the window part 37 has transparency with respect to the excitation light mentioned above.
Note that the window portion 37 is not limited to the light transmitting material as long as it has a light transmitting property with respect to the excitation light. For example, an optical component such as a lens, a polarizing plate, a λ / 4 wavelength plate, or a neutral density filter. It may be.
The constituent material of the second package 36 other than the window portion 37 is not particularly limited, and for example, ceramic, metal, resin, or the like can be used.

[Magnetic shield]
The magnetic shield 38 is configured by a housing whose outer shape is a block shape, and houses the second package 36 therein. The magnetic shield 38 has magnetic shielding properties and has a function of shielding the alkali metal in the gas cell 31 from an external magnetic field. Thereby, the stability in the magnetic shield 38 of the magnetic field of the coil 35 can be improved. Therefore, the oscillation characteristics of the atomic oscillator 1 can be improved.

A window 382 is provided on the wall of the magnetic shield 38 on the first unit 2 side. Thereby, the light emitted from the light emitting part 21 can enter the window part 37 and the gas cell 31 of the second package 36 through the window part 382.
As a constituent material of such a magnetic shield 38, a material having magnetic shielding properties is used, and examples thereof include soft magnetic materials such as Fe and various iron-based alloys (silicon iron, permalloy, amorphous, Sendust, Kovar). Among these, from the viewpoint of excellent magnetic shielding properties, it is preferable to use an Fe—Ni alloy such as Kovar or Permalloy.

  Further, for example, a plurality of leads (not shown) protrude from the magnetic shield 38, and these are electrically connected to the light detection unit 32, the heater 33, the temperature sensor 34, and the coil 35 through wiring. ing. Each lead is electrically connected to the wiring board by a connector or the like (not shown). As this connector, for example, a flexible substrate, a socket-shaped one, or the like can be used.

[Control unit]
The control unit 6 shown in FIG. 1 has a function of controlling the heater 33, the coil 35, and the light emitting unit 21, respectively.
In the present embodiment, the control unit 6 is composed of an IC (Integrated Circuit) chip.
Such a control unit 6 includes an excitation light control unit 61 that controls the frequencies of the resonant lights 1 and 2 of the light emitting unit 21, a temperature control unit 62 that controls the temperature of the alkali metal in the gas cell 31, and the gas cell 31. A magnetic field control unit 63 that controls the magnetic field to be applied.

  The excitation light control unit 61 controls the frequencies of the resonance lights 1 and 2 emitted from the light emission unit 21 based on the detection result of the light detection unit 32 described above. More specifically, the excitation light control unit 61 is configured so that the above-described frequency difference (ω1−ω2) becomes the frequency ω0 unique to the alkali metal based on the detection result of the above-described light detection unit 32. 21 controls the frequencies of the resonance beams 1 and 2 emitted from the beam 21.

Although not shown, the excitation light control unit 61 includes a voltage-controlled crystal oscillator (oscillation circuit), and the oscillation frequency of the voltage-controlled crystal oscillator is synchronized and adjusted based on the detection result of the light detection unit 32. While being output as an output signal of the atomic oscillator 1.
Further, the temperature control unit 62 controls energization to the heater 33 based on the detection result of the temperature sensor 34. Thereby, the gas cell 31 can be maintained within a desired temperature range.
The magnetic field control unit 63 controls energization of the coil 35 so that the magnetic field generated by the coil 35 is constant.

(Optical parts group)
As shown in FIGS. 1 and 4 to 6, the optical component group 4 is disposed between the first unit 2 and the second unit 3 as described above. The optical component group 4 includes an ND filter 41, a lens 42, and a polarization filter 43. The ND filter 41, the lens 42, and the polarizing filter 43 are provided on the optical axis a between the light emitting unit 21 in the first package 22 and the gas cell 31 in the second package 36 described above. ing. In the present embodiment, the ND filter 41, the lens 42, and the polarizing filter 43 are arranged in this order from the first unit 2 side.

[ND filter]
As shown in FIG. 4, the ND filter (attenuating filter) 41 has a plate shape (disc shape), and has a function of adjusting (decreasing) the intensity of the excitation light LL incident on the gas cell 31. For this reason, even when the output of the light emission part 21 is large, the excitation light which injects into the gas cell 31 can be made into a desired light quantity.

  The ND filter 41 is provided to be inclined with respect to the optical axis a. Further, the first surface 411 which is the surface of the ND filter 41 on the first unit 2 side and the second surface 412 which is the surface of the ND filter 41 on the gas cell 31 side are configured in a plane and are parallel to each other. . These will be described later.

Note that the ND filter 41 may have portions with different light attenuation rates on the upper side and the lower side continuously or stepwise. In this case, the attenuation rate of the excitation light can be adjusted by adjusting the position of the ND filter 41 in the vertical direction.
Further, each of the ND filters 41 may have a portion where the light attenuation rate is different continuously or intermittently in the circumferential direction. In this case, the attenuation rate of the excitation light LL can be adjusted by rotating the ND filter 41 around the optical axis a.

[lens]
The lens 42 is a collimating lens having a flat surface 421 located on the light emitting portion 21 side and a curved surface 422 located on the gas cell 31 side. The lens 42 has a function of condensing the excitation light LL and making it parallel light. Thereby, in the atomic oscillator 1, the excitation light LL can be irradiated to the gas cell 31 without waste. Further, among the alkali metal atoms present in the internal space S, the number of alkali metal atoms that resonate with the excitation light LL can be increased. As a result, the intensity of the EIT signal can be increased.

[Polarizing filter]
The polarizing filter 43 is a λ / 4 wavelength plate having a flat surface 431 located on the light emitting portion 21 side and a flat surface 432 located on the gas cell 31 side. Accordingly, the excitation light LL that has become parallel light can be converted into circularly polarized light (right circularly polarized light or left circularly polarized light) by the lens 42.

  As described above, in the state where the alkali metal atoms in the gas cell 31 are Zeeman split by the magnetic field of the coil 35, if the alkali metal atoms are irradiated with excitation light of linearly polarized light, the interaction between the excitation light and the alkali metal atoms causes an alkali. This means that metal atoms are evenly distributed in a plurality of levels where Zeeman splits. As a result, the number of alkali metal atoms at a desired energy level is relatively small with respect to the number of alkali metal atoms at other energy levels, so that the number of atoms that develop a desired EIT phenomenon is reduced and desired. As a result, the oscillation characteristic of the atomic oscillator 1 is deteriorated.

On the other hand, when the alkali metal atom is irradiated with the circularly polarized excitation light in the state where the alkali metal atom in the gas cell 31 is Zeeman split by the magnetic field of the coil 35 as described above, the interaction between the excitation light and the alkali metal atom. Thus, the number of alkali metal atoms having a desired energy level among the plurality of levels in which the alkali metal atom is Zeeman split can be relatively increased with respect to the number of alkali metal atoms having other energy levels. . Therefore, the number of atoms that express the desired EIT phenomenon increases and the desired EIT signal increases, and as a result, the oscillation characteristics of the atomic oscillator 1 can be improved.
In addition, although the planar view shape of the ND filter 41, the lens 42, and the polarizing filter 43 is circular, it is not limited to this, For example, polygons, such as a quadrangle | tetragon and a pentagon, may be comprised. In addition, the ND filter 41, the lens 42, and the polarizing filter 43 are supported by the wiring board by, for example, providing a recess in a wiring board (not shown) and inserting the recess into the recess.

Now, as shown in FIG. 6, a part of the excitation light LL emitted from the first unit 2 is reflected by the second unit 3 and travels toward the first unit 2 (light emitting unit 21) as reflected light LL ′. When the reflected light LL ′ is incident on the light emitting portion 21, the frequency stability of the light emitting portion 21 is lowered depending on the amount of light, and as a result, the frequency stability of the atomic oscillator may be lowered.
Therefore, in the atomic oscillator 1, as described above, the ND filter 41 is provided between the first unit 2 and the second unit 3 and the second surface 412 is inclined with respect to the optical axis a. ing. Accordingly, the reflected light LL ′ is reflected by the second surface 412 of the ND filter 41 inclined with respect to the optical axis a. Therefore, it is possible to effectively suppress the reflected light from entering the second unit 3. As a result, it is possible to suppress the frequency stability of the light emitting portion 21 from being lowered, and the atomic oscillator 1 having excellent frequency stability can be obtained.

In the present embodiment, the optical axis a coincides with a line segment connecting the center point of the first unit 2 and the center point of the second unit 3. Specifically, it coincides with a line segment connecting the center of the light emitting part 21 and the center of the light detecting part 32.
Further, even when the excitation light LL is reflected by the window 313 of the gas cell 31 and the reflected light LL ′ is generated, a part of the light is reflected by the inclined second surface 412 of the ND filter 41 as described above. Is done. Thereby, the effect similar to the above can be acquired. The same applies to the reflected light LL ′ generated by the light detection unit 32.

  Furthermore, as described above, the ND filter 41 is disposed closest to the first unit 2 in the optical component group 4. For this reason, it is possible to prevent the reflected light LL ′ reflected by the surface 421 of the lens 42 on the first unit 2 side from entering the light emitting portion 21, and to reflect it on the surface 422 of the lens 42 on the gas cell 31 side. The reflected light LL ′ can be prevented from entering the light emitting portion 21. Further, the reflected light LL ′ reflected by the surface 431 of the polarizing filter 43 on the first unit 2 side can be prevented from entering the light emitting portion 21 and reflected by the surface 432 of the polarizing filter 43 on the gas cell 31 side. The reflected light LL ′ thus made can be prevented from entering the light emitting portion 21.

In addition, the inclination angle θ1 of the second surface 412 of the ND filter 41 with respect to the optical axis a is preferably 80 ° or less, more preferably 60 ° or less, and particularly preferably 33 °. If the inclination angle θ1 is set in the above numerical range, the above-described effects can be effectively exhibited. In particular, when the inclination angle θ1 is 33 °, the reflected light LL ′ can be effectively reflected by the second surface 412.
In the present specification, the “inclination angle of the second surface 412” means an angle (θ1 shown in FIG. 7) formed by the normal line of the second surface 412 and the optical axis a. . Similarly, the “inclination angle of the first surface 411” refers to an angle (θ2 shown in FIG. 7) formed by the normal line of the first surface 411 and the optical axis a.

In addition, when the reflected light LL ′ is reflected by the second surface 412 of the ND filter 41, it is conceivable that a part of the reflected light LL ′ passes without being reflected by the second surface 412. However, the ND filter 41 has a function of attenuating the amount of light passing therethrough. For this reason, the light quantity of the reflected light LL ′ that passes through the ND filter 41 can be attenuated, and as a result, the reflected light LL ′ can be more effectively suppressed from entering the second unit 3.
Further, the first surface 411 is also inclined with respect to the optical axis a, similarly to the second surface 412. Thereby, a part of the reflected light LL ′ whose light amount has been attenuated by the ND filter 41 is further reflected by the first surface 411. As a result, it is possible to more effectively suppress the reflected light LL ′ from entering the second unit 3.

  Here, as shown in FIG. 7, the excitation light LL is diffused radially at a radiation angle θ3. In the present specification, the “radiation angle” refers to an angle formed between the light beam a of the excitation light LL and the optical axis a. Such excitation light LL depends on a part of light (particularly the excitation light LL) depending on the radiation angle θ3, the inclination angle θ2 of the first surface 411, the separation distance between the light emitting part 21 and the gas cell 31, and the like. There is a possibility that the outermost light of the luminous flux is reflected by the first surface 411 and enters the light emitting portion 21. However, by making the inclination angle θ2 larger than the radiation angle θ3, the excitation light LL is reflected by the first surface 411 even when the separation distance between the light emitting portion 21 and the gas cell 31 is relatively small. It can prevent entering into the light emission part 21. FIG. Therefore, it is possible to obtain the atomic oscillator 1 having better frequency stability and to make the separation distance between the light emitting part 21 and the gas cell 31 relatively small and to reduce the size of the atomic oscillator 1. it can.

Note that the same effect as described above can be obtained by appropriately setting the inclination angle θ2 according to the separation distance between the light emitting portion 21 and the ND filter 41. For example, when the separation distance between the light emitting unit 21 and the ND filter 41 is relatively large, the same effect can be obtained even when the inclination angle θ2 is smaller than the radiation angle θ3.
Further, as described above, in the present embodiment, the first surface 411 and the second surface 412 are parallel. Thereby, manufacture of the ND filter 41 becomes easy. Further, in the atomic oscillator 1, the work of setting the first surface 411 and the second surface 412 can be omitted.

  In the optical component group 4, one or both of the lens 42 and the polarization filter 43 may be omitted. Moreover, each part which comprises the optical component group 4 is not limited to the kind, arrangement | positioning order, number, etc. which were mentioned above. For example, instead of the ND filter 41, an arbitrary optical element such as a lens, a polarizing filter, or a prism can be used. Thus, if the optical element has a surface that is inclined with respect to the optical axis a, the effect of the present invention can be obtained.

Second Embodiment
Next, a second embodiment of the present invention will be described.
FIG. 8 is an enlarged detailed view showing a first unit and optical elements included in the atomic oscillator (quantum interference device) according to the second embodiment of the present invention.
This embodiment is the same as the first embodiment described above except that the configuration of the optical element is different.
In the following description, the second embodiment will be described with a focus on differences from the first embodiment, and description of similar matters will be omitted. Moreover, in FIG. 8, the same code | symbol is attached | subjected about the structure similar to embodiment mentioned above.

As shown in FIG. 8, in the ND filter 41 </ b> A of the present embodiment, the second surface 412 is inclined with respect to the first surface 411. That is, the inclination angle θ4 of the first surface 411 with respect to the optical axis a is different from the inclination angle θ5 of the second surface 412 with respect to the optical axis a.
According to the present embodiment, the inclination angle θ4 is set to a desired numerical value according to, for example, the separation distance between the light emitting unit 21 and the ND filter 41, and the inclination angle θ5 is set to a desired value regardless of the inclination angle θ4. Can be set to a numerical value. In other words, the inclination angle θ4 and the inclination angle θ5 can be set independently. As a result, the frequency stability of the atomic oscillator 1 can be further improved.
The quantum interference device and atomic oscillator described above can be incorporated into various electronic devices. Such an electronic device has excellent reliability.

Hereinafter, the electronic apparatus of the present invention will be described.
2. FIG. 9 is a diagram showing a schematic configuration when the atomic oscillator (quantum interference device) of the present invention is used in a positioning system using a GPS satellite.
The positioning system 100 shown in FIG. 9 includes a GPS satellite 200, a base station device 300, and a GPS receiving device 400.

The GPS satellite 200 transmits positioning information (GPS signal).
The base station device 300 receives the positioning information from the GPS satellite 200 with high accuracy via, for example, an antenna 301 installed at an electronic reference point (GPS continuous observation station), and the reception device 302 receives the positioning information. And a transmission device 304 that transmits positioning information via the antenna 303.

Here, the receiving device 302 is an electronic device provided with the above-described atomic oscillator 1 of the present invention as its reference frequency oscillation source. Such a receiving apparatus 302 has excellent reliability. In addition, the positioning information received by the receiving device 302 is transmitted by the transmitting device 304 in real time.
The GPS receiver 400 includes a satellite receiver 402 that receives positioning information from the GPS satellite 200 via the antenna 401, and a base station receiver 404 that receives positioning information from the base station device 300 via the antenna 403. Prepare.

3. Mobile Object FIG. 10 is a diagram illustrating an example of a mobile object of the present invention.
In this figure, a moving body 1500 has a vehicle body 1501 and four wheels 1502, and is configured to rotate the wheels 1502 by a power source (engine) (not shown) provided in the vehicle body 1501. In such a moving body 1500, the atomic oscillator 1 is built.
According to such a moving body, excellent reliability can be exhibited.

  The electronic device provided with the atomic oscillator (quantum interference device) of the present invention is not limited to the above-described ones. (Personal computer, laptop personal computer), TV, video camera, video tape recorder, car navigation device, pager, electronic organizer (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, TV Telephone, crime prevention TV monitor, electronic binoculars, POS terminal, medical equipment (for example, electronic thermometer, blood pressure monitor, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments Kind (for example, Vehicle, aircraft, gauges of a ship), flight simulators, terrestrial digital broadcasting, can be applied to a mobile phone base station or the like.

The quantum interference device and the atomic oscillator of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.
In the quantum interference device and the atomic oscillator of the present invention, the configuration of each part can be replaced with any configuration that exhibits the same function, and any configuration can be added.
Moreover, you may make it combine the arbitrary structures of each embodiment mentioned above with the quantum interference apparatus and atomic oscillator of this invention.
In the embodiment, the magnetic shield may be omitted.

DESCRIPTION OF SYMBOLS 1 ... Atomic oscillator 2 ... 1st unit 3 ... 2nd unit 4 ... Optical component group 6 ... Control part 21 ... Light-emitting part 22 ... 1st package 23 ... Window part 31 ... Gas cell 32 …… Light detector 33 …… Heater 34 …… Temperature sensor 35 …… Coil 36 …… Second package 37 …… Window 38 …… Magnetic shield 41 …… ND filter 41A …… ND filter 42 …… Lens 43… ... Polarizing filter 61 ... Excitation light control part 62 ... Temperature control part 63 ... Magnetic field control part 100 ... Positioning system 200 ... GPS satellite 300 ... Base station apparatus 301 ... Antenna 302 ... Reception apparatus 303 ... Antenna 304 …… Transmitter 311 …… Main body 311a …… Through hole 312 …… Window 313 …… Window 382 …… Window 400 …… GPS receiver 401 …… Antenna 402 …… Satellite receiver 403 …… Antenna 404 …… Base station receiver 411 …… First surface 412 …… Second surface 421 …… Surface 422 …… Surface 431… ... plane 432 ... plane 1500 ... moving body 1501 ... vehicle body 1502 ... wheel LL ... excitation light LL '... reflected light S ... internal space a ... optical axis θ1 ... tilt angle θ2 ... tilt angle θ3 …… Radiation angle θ4 …… Tilt angle θ5 …… Tilt angle ω0 …… Frequency ω1 …… Frequency ω2 …… Frequency

Claims (8)

A gas cell in which metal atoms are enclosed;
A light source that emits light including a resonant light pair in the metal atom;
An optical element provided between the gas cell and the light source;
With
A surface of the optical element on the gas cell side is inclined with respect to a line segment connecting the light source and the gas cell, and is inclined with respect to a surface of the optical element on the light source side. Quantum interference device.   The quantum interference device according to claim 1, wherein a surface of the optical element on the light source side is inclined with respect to a line segment connecting the light source and the gas cell.   The quantum interference device according to claim 1, wherein the optical element is a neutral density filter. An optical element group including the optical element is disposed between the light source and the gas cell,
4. The quantum interference device according to claim 1, wherein the optical element is disposed closest to the light source in the optical element group. 5.   5. The quantum interference device according to claim 1, wherein an inclination angle θ <b> 1 of a surface on the gas cell side of the optical element with respect to a line segment connecting the light source and the gas cell is 80 ° or less.   The inclination angle θ2 of the surface on the light source side of the optical element with respect to a line segment connecting the light source and the gas cell is larger than the emission angle θ3 of the light emitted from the light source. The quantum interference device according to 1. It claims 1 to atomic oscillator comprising: a quantum interference device according to any one of 6. An electronic apparatus comprising: a quantum interference device according to any one of claims 1 to 6.

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