JP6627335B2 - Quantum interference devices, atomic oscillators, and electronics - 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 high-precision oscillation characteristics in the long term, an atomic oscillator that oscillates based on energy transition of atoms of an alkali metal such as rubidium and cesium is known.

  In general, the operating principle of an atomic oscillator is roughly classified into a method using a double resonance phenomenon by light and a microwave, and a method using a quantum interference effect (CPT: Coherent Population Trapping) by two kinds of light having different wavelengths. Is done. Since an atomic oscillator using the quantum interference effect can be made smaller than an atomic oscillator using the double resonance phenomenon, it is expected that it is mounted on various devices in recent years (for example, see Patent Document 1).

  An atomic oscillator utilizing the quantum interference effect includes, for example, as disclosed in Patent Document 1, a gas cell in which a gaseous alkali metal is sealed, and a light source that emits a resonance light pair that resonates the alkali metal in the gas cell. And a photodetector (light receiving unit) for detecting a pair of resonance light transmitted through the gas cell. In such an atomic oscillator, when the frequency difference between the two types of resonance light is a specific value, both of the two types of resonance light are transmitted without being absorbed by the alkali metal in the gas cell (EIT). An EIT signal, which is a steep signal generated by the EIT phenomenon, is detected by a photodetector, and the EIT signal is used as a reference signal.

JP 2014-17824 A

  Here, from the viewpoint of increasing short-term frequency stability, the EIT signal preferably has a small line width (half width) and a high intensity. Therefore, for example, the atomic oscillator according to Patent Document 1 uses a circularly polarized resonance light pair for the purpose of improving the intensity of the EIT signal.

  However, in the atomic oscillator according to Patent Literature 1, since only the resonance light pair circularly polarized in the same direction irradiates the alkali metal in the gas cell, the distribution of the magnetic quantum number of the alkali metal is biased. . Therefore, the number of metal atoms having a desired magnetic quantum number contributing to the EIT decreases, and as a result, the intensity of the EIT signal cannot be sufficiently improved.

  An object of the present invention is to provide a quantum interference device capable of effectively improving the intensity of an EIT signal, and to provide an atomic oscillator, an electronic device, and a moving object including the quantum interference device.

The above object is achieved by the present invention described below.
The quantum interference device of the present invention, an atomic cell having an internal space in which metal is enclosed,
A first light source unit that emits a pair of resonance lights that are circularly polarized in the same direction and resonate the metal toward the atomic cell,
A second component that has a polarization component in a direction parallel to the propagation direction of the resonance light pair in the internal space and emits adjustment light for resonating the metal to the atom cell in a direction that intersects the resonance light pair. And a light source unit.

  According to such a quantum interference device, in addition to the resonance light pair circularly polarized in the same direction as each other, the adjustment light having a polarization component in a direction parallel to the propagation direction of the resonance light pair in the atom cell. Irradiates the metal in the atomic cell in a direction that intersects the resonance light pair, thereby offsetting or relaxing the bias of the magnetic quantum number distribution due to the resonance light pair with the adjustment light, and adjusting the distribution of the magnetic quantum number distribution of the metal. Unevenness can be reduced. Therefore, it is possible to increase the number of metal atoms having a desired magnetic quantum number contributing to the EIT, and consequently, to use the circularly polarized resonance light pair to remarkably exhibit the effect of improving the intensity of the EIT signal. it can. Therefore, the intensity of the EIT signal can be effectively improved.

  In addition, since the adjustment light is incident on the atomic cell in a direction crossing the resonance light pair, even if the adjustment light transmits through the atomic cell, the adjustment light is incident on the light receiving unit that detects the resonance light pair transmitted through the atomic cell. Can be prevented or reduced. Therefore, the S / N ratio of the EIT signal can be increased.

The quantum interference device of the present invention preferably includes a magnetic field generation unit that generates a magnetic field in a direction along a propagation direction of the resonance light pair in the internal space.
Thereby, the intensity of the EIT signal can be effectively improved.

  In the quantum interference device according to the aspect of the invention, it is preferable that the magnetic field generation unit includes a Helmholtz coil.

  This allows the adjustment light to be incident on the atomic cell with the magnetic field generating unit being close to the atomic cell.

  In the quantum interference device according to the aspect of the invention, it is preferable that the adjustment light be circularly polarized light or elliptically polarized light.

  Thereby, it is possible to realize the adjustment light having the polarization component in the direction along the propagation direction of the resonance light pair in the atom cell.

  In the quantum interference device according to the aspect of the invention, it is preferable that the second light source unit includes a light-emitting element and a quarter-wave plate disposed between the light-emitting element and the atom cell.

  This makes it possible to generate circularly or elliptically polarized adjustment light. Further, by rotating the quarter-wave plate about the axis of the light from the light emitting element, it is also possible to adjust the size of the desired polarization component of the adjustment light.

In the quantum interference device of the present invention, it is preferable that the adjustment light is linearly polarized light.
Thereby, it is possible to realize the adjustment light having the polarization component in the direction along the propagation direction of the resonance light pair in the atom cell. Further, the size of the desired polarization component of the adjustment light can be efficiently increased.

  In the quantum interference device according to the aspect of the invention, it is preferable that the second light source unit includes a light emitting element and a polarizer disposed between the light emitting element and the atom cell.

  This makes it possible to generate linearly polarized adjustment light. In addition, by rotating the polarizer around the axis of the light from the light emitting element, it is possible to adjust the size of the desired polarization component of the adjustment light.

In the quantum interference device according to the aspect of the invention, the atomic cell may include an incident-side window that receives the resonance light pair, an emission-side window that emits the resonance light pair, the incident-side window, and the emission-side window. And a body portion disposed between the body portion and the inner side space together with the entrance side window portion and the exit side window portion,
It is preferable that the adjustment light is transmitted through the body portion and enters the internal space.
This allows the adjustment light to be incident on the atomic cell in a direction crossing the resonance light pair.

In the quantum interference device of the present invention, the resonance light pair is a D1 line,
Preferably, the adjustment light is a D2 line.
Thereby, the intensity of the EIT signal can be efficiently improved.

An atomic oscillator according to the present invention includes the quantum interference device according to the present invention.
Accordingly, it is possible to provide an atomic oscillator including the quantum interference device that can effectively improve the intensity of the EIT signal.

An electronic device according to the present invention includes the quantum interference device according to the present invention.
This makes it possible to provide an electronic device including the quantum interference device that can effectively improve the intensity of the EIT signal.

A mobile object according to the present invention includes the quantum interference device according to the present invention.
Accordingly, it is possible to provide a moving object including the quantum interference device that can effectively improve the intensity of the EIT signal.

FIG. 1 is a schematic diagram illustrating an atomic oscillator (quantum interference device) according to a first embodiment of the present invention. FIG. 3 is a diagram for simply explaining an energy state of an alkali metal atom. 5 is a graph illustrating a relationship between a frequency difference between two lights emitted from a light source unit and an intensity of light detected by a light receiving unit. FIG. 2 is a schematic diagram illustrating a light source unit, an atomic cell, and a magnetic field generation unit included in the atomic oscillator illustrated in FIG. 1. FIG. 5 is a cross-sectional view of the atomic cell shown in FIG. It is a figure which shows an example of the relationship between the energy state of a cesium atom, a resonance light pair (1st resonance light, 2nd resonance light), and adjustment light (3rd resonance light). A diagram showing a magnetic quantum number of the distribution of sodium atoms, (a) represents a diagram showing a distribution of when irradiated with resonant light of sigma ₊ circularly polarized light, (b), the sigma _- a circularly polarized resonant light It is a figure which shows the distribution at the time of irradiation. 5 is a graph showing the relationship between the power density of adjustment light (re-pump light) and the number of distributions of magnetic sublevels of cesium atoms in the configuration shown in FIG. It is a schematic diagram for explaining a light source part, an atomic cell, and a magnetic field generation part provided in an atomic oscillator according to a second embodiment of the present invention. 10 is a graph showing the relationship between the power density of adjustment light (re-pump light) and the distribution number of magnetic sublevels of cesium atoms in the configuration shown in FIG. 9. It is a cross-sectional view of an atomic cell provided in an atomic oscillator according to a third embodiment of the present invention. FIG. 1 is a diagram illustrating a schematic configuration in a case where an atomic oscillator of the present invention is used in a positioning system using a GPS satellite. It is a figure showing an example of a mobile of the present invention.

  Hereinafter, a quantum interference device, an atomic oscillator, an electronic device, and a moving object 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 (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, and may be applied to devices such as a magnetic sensor and a quantum memory. It is possible.

<First embodiment>
FIG. 1 is a schematic diagram showing an atomic oscillator (quantum interference device) according to the first embodiment of the present invention. FIG. 2 is a diagram for simply explaining the energy state of an alkali metal atom. FIG. 3 is a graph illustrating a relationship between a frequency difference between two lights emitted from the light source unit and an intensity of light detected by the light receiving unit.

  An atomic oscillator 1 shown in FIG. 1 is an atomic oscillator utilizing a quantum interference effect. As shown in FIG. 1, the atomic oscillator 1 includes an atomic cell 2 (gas cell), a light source unit 3, a light receiving unit 4, a heater 5 (temperature adjusting unit), a temperature sensor 6, a magnetic field generating unit 7, , A control unit 8.

First, the principle of the atomic oscillator 1 will be briefly described.
As shown in FIG. 2, the alkali metal has a three-level energy level including two ground levels (a first ground level and a second ground level) and an excited level. Here, the first ground level is in a lower energy state than the second ground level.

When the alkali metal is irradiated with the first resonance light and the second resonance light, which are two kinds of resonance lights having different frequencies, the difference (ω ₁₎ between the frequency ω ₁ of the first resonance light and the frequency ω ₂ of the second resonance light −ω ₂ ), the light absorptivity (light transmittance) of the resonance lights 1 and 2 in the alkali metal changes.

The difference (ω ₁ −ω ₂ ) between the frequency ω ₁ of the first resonance light and the frequency ω ₂ of the second resonance light is a frequency corresponding to the energy difference ΔE between the first ground level and the second ground level. , The excitation from the first ground level and the second ground level to the excited level is stopped. At this time, both the first resonance light and the second resonance light are transmitted without being absorbed by the alkali metal. Such a phenomenon is called a CPT phenomenon or an electromagnetically induced transparency (EIT).

For example, the frequency omega ₁ of the first resonant light is fixed, when gradually changing the frequency omega ₂ of the second resonance light, the frequency omega ₁ of the first resonance light difference between the frequency omega ₂ of the second resonance light ( ω ₁ −ω ₂ ) matches the frequency ω ₀ corresponding to the energy difference ΔE between the first ground level and the second ground level, the intensity of the first resonance light and the second resonance light transmitted through the alkali metal. Rises 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, by using such an EIT signal as a reference, a highly accurate oscillator can be configured.

Hereinafter, each part of the atomic oscillator 1 will be briefly described.
[Gas cell]
The atomic cell 2 is filled with a gaseous alkali metal such as rubidium, cesium, and sodium. In addition, a rare gas such as argon or neon, or an inert gas such as nitrogen may be sealed as a buffer gas together with the alkali metal gas in the atomic cell 2 as necessary.

  As will be described in detail later, the atomic cell 2 has a body having a through-hole and a pair of windows closing the opening of the through-hole of the body, whereby the gaseous alkali metal is sealed. Internal space is formed.

[Light emitting part]
The light source unit 3 has a function of emitting light LL including the above-described first resonance light and second resonance light that constitute a resonance light pair that resonates the alkali metal atoms in the atomic cell 2.

  Further, the light LL emitted from the light source unit 3 includes third resonance light in addition to the first resonance light and the second resonance light.

  The first resonance light is light (probe light) that excites the alkali metal atoms in the atomic cell 2 from the first ground level to the excitation level. On the other hand, the second resonance light is light (coupling light) that excites the alkali metal atoms in the atomic cell 2 from the above-mentioned second ground level to the excited level. Here, the first resonance light and the second resonance light are circularly polarized in the same direction. The third resonance light is “adjustment light” (repump light) for adjusting the magnetic quantum number of the alkali metal in the atomic cell 2. The light source unit 3 will be described later in detail. Note that "circularly polarized light" means that when focusing on either the electric field component or the magnetic field component of a light wave, the vibration direction rotates at the frequency of the light wave in a plane perpendicular to the light traveling direction. Is light whose amplitude is constant irrespective of its direction, in other words, light in which the vibration of an electric field (or magnetic field) draws a circle as it propagates.

[Light receiving section]
The light receiving unit 4 has a function of detecting the intensity of the light LL transmitted through the atomic cell 2 (particularly, a resonance light pair composed of the first resonance light and the second resonance light).

  The light receiving unit 4 is not particularly limited as long as it can detect the intensity of the light LL as described above. For example, a light detector such as a photodiode that outputs a signal corresponding to the intensity of the received light is used. (Light receiving element) can be used.

[heater]
The heater 5 (temperature control unit) has a function of heating the above-described atomic cell 2 (more specifically, the alkali metal in the atomic cell 2). Thereby, the alkali metal in the atomic cell 2 can be maintained in a gaseous state having an appropriate concentration.

  The heater 5 includes, for example, a heating resistor that generates heat when energized. The heating resistor may be provided in contact with the atomic cell 2 or may be provided in a non-contact state with the atomic cell 2.

  The heater 5 is not limited to the above-described embodiment as long as it can heat the atomic cell 2, and various heaters can be used. Alternatively, the temperature of the atomic cell 2 may be adjusted by using a Peltier element instead of or in combination with the heater 5.

[Temperature sensor]
The temperature sensor 6 has a function of detecting the temperature of the heater 5 or the atomic cell 2.
This temperature sensor 6 is arranged, for example, in contact with the heater 5 or the atomic cell 2.

  Each of the temperature sensors 6 is not particularly limited, and various known temperature sensors such as a thermistor and a thermocouple can be used.

[Magnetic field generator]
The magnetic field generator 7 has a function of applying a magnetic field to the alkali metal in the atomic cell 2. Thereby, the gap between a plurality of different energy levels in which the alkali metal atoms in the atomic cell 2 are degenerated can be expanded by Zeeman splitting, and the resolution can be improved. As a result, the accuracy of the oscillation frequency of the atomic oscillator 1 can be improved.

  Here, the magnetic field from the magnetic field generation unit 7 is along (in parallel or substantially parallel to) the traveling directions of the first resonance light and the second resonance light in the atomic cell 2. From the viewpoint of efficiently causing the first resonance light and the second resonance light to act on the alkali metal in the atomic cell 2, the direction of the magnetic field from the magnetic field generating unit 7 in the atomic cell 2 is the first resonance light. It is preferably from 0 ° to 30 °, more preferably from 0 ° to 20 °, even more preferably from 0 ° to 10 ° with respect to the traveling direction of the light and the second resonance light. .

  The magnetic field generator 7 is configured to include a pair of coils provided to face each other via the atomic cell 2 so as to form a Helmholtz type. The magnetic field generator 7 may include a coil wound along the outer periphery of the atomic cell 2 so as to form a solenoid type.

  The magnetic field generated by the magnetic field generator 7 is a constant magnetic field (DC magnetic field), but an AC magnetic field may be superimposed.

[Control unit]
The control unit 8 has a function of controlling the light source unit 3, the heater 5, and the magnetic field generation unit 7, respectively.

  The control unit 8 includes a light source control unit 82 that controls the light source unit 3, a temperature control unit 81 that controls the temperature of the alkali metal in the atomic cell 2, and a magnetic field control unit 83 that controls the magnetic field from the magnetic field generation unit 7. And

The light source control unit 82 has a function of controlling the frequencies of the first resonance light and the second resonance light emitted from the light source unit 3 based on the detection result of the light receiving unit 4 described above. More specifically, the light source control unit 82 controls the first resonance light and the first resonance light emitted from the light source unit 3 so that the above-described frequency difference (ω ₁ −ω ₂ ) becomes the above-described frequency ω ₀ inherent to the alkali metal. The frequency of the second resonance light is controlled.

  More specifically, although not shown, the light source control unit 82 includes, for example, a frequency control unit, a voltage controlled crystal oscillator (VCXO), a phase locked loop (PLL), and the like. ,have.

  The frequency control unit detects the EIT state in the atomic cell 2 based on the light receiving intensity of the light receiving unit 4, and outputs a control voltage according to the detection result. Thus, the frequency control unit controls the voltage-controlled crystal oscillator so that the light receiving unit 4 detects the EIT signal.

  The voltage-controlled crystal oscillator is controlled by a frequency control unit to have a desired oscillation frequency, and oscillates at a frequency of, for example, several MHz to several tens MHz. The output signal of the voltage-controlled crystal oscillator is input to the phase locked loop and output as the output signal of the atomic oscillator 1.

The phase locked loop frequency multiplies the output signal from the voltage controlled crystal oscillator. As a result, the phase locked loop oscillates at half the frequency corresponding to the energy difference ΔE between the two different ground levels of the alkali metal atom. The signal (high-frequency signal) thus multiplied is input to a first light source 311 of a first light source unit 31 described later as a drive signal after a DC bias current is superimposed thereon. This modulates a light emitting element such as a semiconductor laser included in the first light source 311 to convert the first resonance light and the second resonance light, which are two lights having a frequency difference (ω ₁ −ω ₂ ) of ω _0. It can be emitted. Here, the current value of the DC bias current is controlled to a predetermined value by a bias control unit (not shown). Thereby, the center wavelength of the first resonance light and the second resonance light can be controlled as desired.

  Further, the temperature control unit 81 controls energization of the heater 5 based on the detection result of the temperature sensor 6. Thereby, the atomic cell 2 can be maintained within a desired temperature range. For example, the temperature of the atomic cell 2 is adjusted by the heater 5 to, for example, about 70 ° C.

  Further, the magnetic field control unit 83 controls energization to the magnetic field generation unit 7 so that the magnetic field generated by the magnetic field generation unit 7 becomes constant.

The control unit 8 described above is provided, for example, on an IC chip mounted on a substrate.
The configuration of the atomic oscillator 1 has been briefly described above.

(Detailed description of light source unit, atomic cell and magnetic field generation unit)
FIG. 4 is a schematic diagram for explaining a light source unit, an atomic cell, and a magnetic field generation unit included in the atomic oscillator shown in FIG.

  As shown in FIG. 4, the light source unit 3 includes a first light source unit 31 that emits a resonance light pair LL1 including the first resonance light and the second resonance light as the first light, and an adjustment light LL2 including the third resonance light. As a second light.

  The first light source unit 31 includes a first light source 311 (first light emitting element) and a 波長 wavelength plate 312. In the first light source unit 31, a λ / 2 wavelength plate may be disposed between the first light source 311 and the 波長 wavelength plate 312. In this case, the first light source 311 may be installed in a posture rotated by 90 ° around the optical axis. In the first light source unit 31, a lens may be disposed between the first light source 311 and the atomic cell 2. Thereby, the resonance light pair LL1 in the atomic cell 2 can be made parallel light.

  The first light source 311 has a function of emitting the linearly polarized resonance light pair LL1a. The first light source 311 is not particularly limited as long as it can emit light including the resonance light pair LL1a, and is, for example, a semiconductor laser such as an edge emitting laser or a vertical cavity surface emitting laser (VCSEL). Note that “linearly polarized light” is light in which the vibration surface of an electromagnetic wave (light) is within one plane, in other words, light in which the vibration direction of an electric field (or magnetic field) is constant.

  The 波長 wavelength plate 312 is a birefringent element that generates a phase difference π / 2 (90 °) between orthogonal polarization components. The 波長 wavelength plate 312 has a function of converting the resonance light pair LL1a from the first light source 311 from linearly polarized light to circularly polarized (including elliptically polarized light) resonance light LL1. Thereby, the resonance light pair LL1 including the first resonance light and the second resonance light described above can be generated.

  As described above, the first light source unit 31 emits the resonance light pair LL1 using the light from the first light source 311.

  On the other hand, the second light source unit 32 includes a second light source 321 (second light emitting element), a polarizer 322, and a 波長 wavelength plate 323. In the second light source unit 32, a lens may be disposed between the second light source 321 and the atomic cell 2. Thereby, the adjustment light LL2 in the atomic cell 2 can be made parallel light.

  The second light source 321 has a function of emitting light LL2a including linearly polarized resonance light. In particular, the light LL2a has a larger line width than the above-described resonance light pair LL1a from the first light source 311. Thereby, as described later, it is possible to generate the adjustment light LL2 having a larger line width than the resonance light pair LL1. The second light source 321 is not particularly limited as long as it can emit light LL2a having a line width larger than the resonance light pair LL1a. For example, a semiconductor such as an edge emitting laser or a vertical cavity surface emitting laser (VCSEL) is used. It is a light emitting element such as a laser, a light emitting diode (LED), and an organic electroluminescent (organic EL) element.

  In particular, it is preferable that the second light source 321 emits non-polarized light, for example, a light emitting diode. That is, it is preferable that the second light source unit 32 generates the adjustment light LL2 using the light from the light emitting diode that forms the second light source 321. Thus, it is possible to generate the adjustment light LL2 having a wide line width with a relatively simple configuration.

  The light LL2a from the second light source 321 is incident on the polarizer 322, and the light LL2b passes through and extracts the resonance light LL2b including only a linear polarization component in a specific direction included in the light LL2a. The resonance light LL2b is linearly polarized in a direction parallel to the propagation direction of the resonance light pair LL1 in the atomic cell 2 (in other words, the direction C of the magnetic field of the magnetic field generator 7 described later). When a semiconductor laser such as an edge emitting laser that emits polarized light or a vertical cavity surface emitting laser (VCSEL) is used as the second light source 321, the polarizer 322 may be omitted. In this case, the second light source 321 may be installed so that the light LL2a from the second light source 321 becomes the resonance light LL2b.

  The quarter-wave plate 323 has a function of converting the resonance light LL2b generated by the polarizer 322 from linearly polarized light to circularly polarized light (including elliptically polarized light) LL2. Thereby, the adjustment light LL2 serving as the third resonance light described above can be generated. Here, the adjustment light LL2 has a polarization component in a direction parallel to the propagation direction of the resonance light pair LL1 in the atomic cell 2 (in other words, the direction C of the magnetic field of the magnetic field generation unit 7 described later). In the present embodiment, the polarization direction of the linearly polarized resonance light LL2b (b2 direction shown in FIG. 4) is different from the polarization direction of the linearly polarized resonance light pair LL1a (b1 direction in FIG. 4). Orthogonal direction). Therefore, when the resonance light pair LL1 generated by the 波長 wavelength plate 312 is right circularly polarized light, the adjustment light LL2 generated by the quarter wavelength plate 323 is left circularly polarized light, while the resonance light pair LL1 is left polarized. In the case of circularly polarized light, the adjustment light LL2 is right circularly polarized light.

  As described above, the second light source unit 32 emits the adjustment light LL2 using the light from the second light source 321.

  The atomic cell 2 is irradiated with the resonance light pair LL1 and the adjustment light LL2 from the first light source unit 31 and the second light source unit 32 configured as described above.

  As shown in FIG. 4, the atomic cell 2 has a body 21 and a pair of windows 22 and 23 provided with the body 21 interposed therebetween. In this atomic cell 2, the body 21 is disposed between the pair of windows 22 and 23, and the internal space S in which the gaseous alkali metal is sealed is divided into the body 21 and the pair of windows 22. , 23 form (configure) sections.

  More specifically, the body 21 has a plate shape, and a through hole 211 is formed in the body 21 in the thickness direction of the body 21. In the present embodiment, the cross section of the through hole 211 has a rectangular shape as shown in FIG. Further, the outer shape of the cross section of the body portion 21 is also a rectangle corresponding to the shape of the through hole 211. Further, the body portion 21 has transparency to the adjustment light LL2. The left portion of the body 21 in FIG. 5 is an incident side window (third light transmitting portion) through which the adjustment light LL2 enters the internal space S of the atomic cell 2, and the body 21 in FIG. The right part is an emission-side window (fourth light transmission part) from which the adjustment light LL2 is emitted from the interior space S of the atomic cell 2.

  The constituent material of the body portion 21 is not particularly limited as long as the body portion 21 has transparency to the adjustment light LL2, but it is preferable to use a glass material from the viewpoint that the atomic cell 2 can be easily manufactured. .

  A window 22 is joined to one surface of the body 21, and a window 23 is joined to the other surface of the body 21. Thus, the one end opening of the through hole 211 is closed by the window 22, and the other end opening of the through hole 211 is closed by the window 23.

  The method of joining the body portion 21 and the windows 22 and 23 is determined according to these constituent materials, and is not particularly limited as long as it can be joined in an airtight manner. A method, a direct bonding method, a surface activated bonding method, or the like can be used.

  Each of the windows 22 and 23 joined to the body 21 has a plate shape, and has transparency to the above-described resonance light pair LL1. One of the windows 22 is an incident-side window (first light transmitting portion) through which the resonance light pair LL1 enters the internal space S of the atomic cell 2, and the other window 23 is a window of the atomic cell 2. An emission-side window portion (second light transmission portion) from which the resonance light pair LL1 exits from inside the internal space S.

  The constituent materials of the windows 22 and 23 are not particularly limited as long as they have the above-described transmittance for the light LL. However, from the viewpoint that the atomic cell 2 can be easily manufactured, a glass material is used. Preferably, it is used.

  A gaseous alkali metal is mainly contained in the internal space S, which is a space inside the through hole 211 closed by the windows 22 and 23.

  In the internal space S of the atomic cell 2 configured as described above, the optical axis a1 of the resonance light pair LL1 is parallel to the axis a along the direction in which the windows 22 and 23 of the atomic cell 2 are aligned. On the other hand, the optical axis a2 of the adjustment light LL2 intersects the axis a and the optical axis a1 at the intersection P. In FIG. 4, the optical axis a1 coincides with the axis a, but the optical axis a1 may be inclined at an angle of 10 ° or less with respect to the axis a.

  Then, the resonance light pair LL1 enters the internal space S of the atomic cell 2 through the window 22, and the adjustment light LL2 enters through the body 21. As shown in FIG. 5, in the atomic cell 2, the width W2 of the adjustment light LL2 is larger than the width W1 of the resonance light pair LL1. The width W2 of the adjustment light LL2 is smaller than the width W in the atomic cell 2.

  The resonance light pair LL <b> 1 that has entered the internal space S exits through the window 23. The adjustment light LL2 that has entered the internal space S exits through the body 21. Here, on the side where the resonance light pair LL1 of the atomic cell 2 is emitted, the above-described light receiving unit 4 is arranged on the optical axis a1 or an extension thereof, and the resonance light pair LL1 passing through the atomic cell 2 receives the light. The light is received by the unit 4.

  A coil 71 that is a Helmholtz coil provided in the magnetic field generator 7 is arranged on the outer periphery of the atomic cell 2. The magnetic field generated from the coil 71 is in the direction along the axis a and the optical axis a1 (parallel or almost parallel to the axis a and the optical axis a1) in the internal space S.

(Effect of resonance light pair and adjustment light)
Hereinafter, the operation of the resonance light pair LL1 and the adjustment light LL2 will be described in detail.

FIG. 6 is a diagram illustrating an example of the relationship between the energy state of a cesium atom, a resonance light pair (first resonance light, second resonance light), and adjustment light (third resonance light). 7A and 7B are diagrams showing the distribution of the magnetic quantum number of sodium atoms. FIG. 7A is a diagram showing the distribution when σ ₊ circularly polarized resonance light is irradiated, and FIG. sigma _- is a diagram showing the distribution of when irradiated with circularly polarized light of the resonant light.

For example, when irradiating the cesium atoms sealed in the atomic cell 2 with the resonance light pair and the adjustment light, as shown in FIG. 6, the first resonance light and the second resonance light (resonance light pair) are σ ₊ The D1 line that is polarized (left circularly polarized light) is used, and the D2 line that is σ _- polarized (right circularly polarized light) is used as the third resonance light (adjustment light). The first resonance light and the second resonance light may be σ _- polarized light, the third resonance light may be σ ₊ polarization, and the first resonance light and the second resonance light may be D2 line and the third resonance light. May be the D1 line.

Cesium atom is a kind of alkali metal atoms _has a ground level of _{6S 1/2,} and two excited levels of _{6P 1/2} and _{6P 3/2,} the. In addition, each level of 6S _1/2 , 6P _1/2 , and 6P _3/2 has a fine structure split into a plurality of energy levels. Specifically, the 6S _1/2 level has two ground levels of F = 3, 4, the 6P _1/2 level has two excited levels of F ′ = 3, 4, The 6P _3/2 level has four excitation levels of F ″ = 2, 3, 4, 5.

The cesium atom in the first ground level of F = 3 of 6S _1/2 transitions to the excitation level of F ″ = 2, 3, or 4 of F ″ = 6P _3/2 by absorbing the D2 line. But cannot transition to an excitation level of F ″ = 5. The cesium atom at the second ground level of F = 4 of 6S _1/2 transitions to any of the excitation levels of F ″ = 3, 4, or 5 of 6P _3/2 by absorbing the D2 line. But cannot transition to the excitation level of F ″ = 2. These are based on a transition selection rule assuming an electric dipole transition. Conversely, a cesium atom at any of the excitation levels of F ″ = 3, 4 of 6P _3/2 emits a D2 line and a ground level of F = 3 or F = 4 of 6S _1/2 ( Either the original ground level or the other ground level). Such a 6S _1/2 F = 3, 4 ground levels and 6P _3/2 F ″ = A three-level consisting of any one of the three or four excitation levels is called a Λ-type three level because a Λ-type transition is possible by absorption and emission of the D2 line. Similarly, the three levels consisting of the two ground levels of F = 3 and 4 of 6S _1/2 and the excitation level of F ′ = 3 and 4 of 6P _1/2 are also the absorption levels of the D1 line. Since Λ-type transition by light emission is possible, Λ-type three levels are formed.

On the other hand, the cesium atom at the excitation level of F ″ = 2 of 6P _3/2 emits the D2 line and always becomes the ground level of F = 3 of 6S _1/2 (original ground level). Similarly, the cesium atom at the excited level of F ″ = 5 of 6P _3/2 emits the D2 line, and necessarily emits the ground level of F = 4 of 6S _1/2 (the original ground level). ). Therefore, the three levels consisting of two ground levels of F = 3 and 4 of 6S _1/2 and an excitation level of F ″ = 2 or F ″ = 5 of 6P _3/2 are absorbed and emitted by the D2 line. Does not form a Λ-type three level.

Such a cesium atom has a wavelength of D1 line in vacuum of 894.593 nm, a wavelength of D2 line in vacuum of 852.347 nm, and a hyperfine splitting frequency (ΔE) of 6S _1/2. 9.1926 GHz.

Note that an alkali metal atom other than a cesium atom similarly has two ground levels and an excited level that form a Λ-type three level. Here, the sodium atom has a D1 line wavelength in a vacuum of 589.756 nm, a D2 line wavelength in a vacuum of 589.158 nm, and a 3S _1/2 hyperfine splitting frequency (ΔE). 1.7716 GHz. Furthermore, rubidium ⁽⁸⁵ Rb) atom is the wavelength of the D1 line is 794.979nm in vacuum, the wavelength of the D2 line is 780.241nm in _{vacuum, 5S 1/2} of hyperfine splitting frequency ( ΔE) is 3.0357 GHz. Furthermore, rubidium ⁽⁸⁷ Rb) atom is the wavelength of the D1 line is 794.979nm in vacuum, the wavelength of the D2 line is 780.241nm in _{vacuum, 5S 1/2} of hyperfine splitting frequency ( ΔE) is 6.8346 GHz.

For example, as shown in FIG. 7, a sodium atom, which is one kind of alkali metal atom, has two ground levels and an excited level that form a Λ-type three level, and has a 3S _1/2 F = 1. The first ground level has three magnetic quantum numbers of m _F1 = −1, 0, and 1, and the second ground level of 3S _1/2 of F = 2 is m _F2 = −2, −1. , 0, 1, 2 and 3P1 / 2 F ′ = 2 excitation levels are m _{F ′} = −2, −1, 0, 1, 2 Having a number.

When a sodium atom at the ground level of F = 1 or F = 2 is irradiated with a pair of σ ₊ circularly polarized light, a magnetic quantum number increases by one, as shown in FIG. Is excited to an excited level. At this time, the distribution of the sodium atom at the ground level of F = 1 or F = 2 changes in a direction in which the magnetic quantum number is larger.

On the other hand, when a sodium atom at the ground level of F = 1 or F = 2 is irradiated with a σ _- circularly polarized resonance light pair, the magnetic quantum number is reduced by one as shown in FIG. Excited to an excited level by a rule. At this time, the distribution of the sodium atom at the ground level of F = 1 or F = 2 changes in the direction of the smaller magnetic quantum number.

  In FIG. 7, for convenience of explanation, the distribution of the magnetic quantum number is shown by taking a sodium atom having a simple structure as an example. However, in other alkali metal atoms, the ground level and the excitation level are each 2F + 1. The number of magnetic quantum numbers (magnetic sub-levels) changes, and the distribution of magnetic quantum numbers changes according to the above selection rule.

  As described above, if the alkali metal in the atomic cell 2 is irradiated with the resonance light pair LL1 and the adjustment light LL2 from the same direction, one of the resonance light pair and the adjustment light is right circularly polarized light, and the other is left polarization. By using circularly polarized light, the bias of the magnetic quantum number of the alkali metal can be reduced.

  As described above, in the atomic oscillator 1, the adjustment light LL2 is applied to the atomic cell 2 in a direction orthogonal (crossing) to the resonance light pair LL1. In the present embodiment, the adjustment light LL2 is circularly polarized. For this reason, the adjustment light LL2 acts on the alkali metal in the atomic cell 2 as light in a polarization state in which 50% of π-polarized light, 25% of right-handed circularly-polarized light, and 25% of left-handed circularly-polarized light are superimposed. Here, since the components of the right circularly polarized light and the left circularly polarized light of the adjustment light LL2 are the same as each other, the magnetic quantum number does not change due to these components.

  FIG. 8 is a graph showing the relationship between the power density of the adjustment light (re-pump light) and the distribution number of magnetic sublevels of cesium atoms in the configuration shown in FIG.

For example, cesium is used as an alkali metal in the atomic cell 2, the power density (photon flux density) of the resonance light pair LL1 is fixed ( ² mW / cm ² ), and the power density of the adjustment light LL2 is changed (from 0 mW / cm ^2). Cesium atom with a stable magnetic quantum number m _F3 = 0 with respect to the magnetic quantum number of the first ground level F = 3 of the cesium atom when changed in the range up to 5 mW / cm ² ). As shown in FIG. 8, the number increases as the power density of the adjustment light LL2 increases.

On the other hand, with respect to the magnetic quantum number of the second ground level F = 4 of the cesium atom, the number of the cesium atoms at which the magnetic quantum number m _F4 = 0 is stable with respect to the magnetic field is determined when the power density of the adjustment light LL2 is 0 mW / cm. ² when ultra 4.5 mW / cm ² or less, has increased as compared with the case of not irradiating the adjustment light LL2. Further, the number of cesium atoms where the magnetic quantum number m _F4 = 0 becomes the maximum (maximum value 1.60%) when the power density of the adjustment light LL2 is 0.7 mW / cm ² . Therefore, the adjustment light LL2 works most efficiently when the power density of the adjustment light LL2 is 0.7 mW / cm ² .

  From the above viewpoint, when the power density of the resonance light pair LL1 is P1 and the power density of the adjustment light LL2 is P2, P2 / P1 is preferably more than 0 and 2.25 or less, and 0.1 or less. It is more preferably not less than 1.0 and more preferably not less than 0.2 and not more than 0.6. Thereby, the operation of the adjustment light LL2 can be made efficient.

According to the atomic oscillator 1 described above, in addition to the resonance light pair LL1 circularly polarized in the same direction, the propagation direction of the resonance light pair LL1 in the atomic cell 2 (the direction of the magnetic field of the magnetic field generation unit 7) Adjustment light LL2 having a polarization component parallel to C) (a polarization component acting as π-polarized light) is applied to the alkali metal in the atomic cell 2 in a direction intersecting (perpendicular to) the resonance light pair LL1. I do. Accordingly, the bias of the distribution of the magnetic quantum numbers due to the resonance light pair LL1 is offset or reduced by the adjustment light LL2, and the bias of the distribution of the magnetic quantum numbers of the alkali metal can be reduced. Therefore, the number of alkali metal atoms having a desired magnetic quantum number that contributes to the EIT (for example, in the case of a cesium atom, the number of atoms where the magnetic quantum numbers m _F3 = 0 and m _F4 = 0) can be increased. As a result, the effect of improving the intensity of the EIT signal can be remarkably exhibited by using the circularly polarized resonance light pair LL1. Therefore, the intensity of the EIT signal can be effectively improved.

  Further, since the adjustment light LL2 is incident on the atomic cell 2 in a direction intersecting (perpendicular to the present embodiment) with the resonance light pair LL1, even if the adjustment light LL2 passes through the atomic cell 2, the resonance light transmitted through the atomic cell 2 may be used. The adjustment light LL2 can be prevented or reduced from entering the light receiving unit 4 that detects the light pair LL1. Therefore, the S / N ratio of the EIT signal can be increased.

  Here, since the magnetic field generation unit 7 generates a magnetic field in the internal space S in a direction along the propagation direction of the resonance light pair LL1, the intensity of the EIT signal can be effectively improved.

  Further, since the magnetic field generator 7 includes the coil 71 which is a Helmholtz coil, the adjustment light LL2 is transmitted to the atomic cell 2 through a pair of coils constituting the coil 71 in a state where the magnetic field generator 7 is close to the atomic cell 2. Can be incident.

  In the present embodiment, the adjustment light LL2 is circularly polarized light or elliptically polarized light. Thereby, the adjustment light LL2 having the polarization component in the direction along the propagation direction of the resonance light pair LL1 in the atomic cell 2 can be realized.

  Further, as described above, the second light source unit 32 includes the second light source 321 which is a light emitting element, and the 波長 wavelength plate 323 disposed between the second light source 321 and the atomic cell 2. . Thereby, the adjustment light LL2 of the circularly polarized light or the elliptically polarized light can be generated. Further, by rotating the quarter-wave plate 323 about the axis of the light from the second light source 321, it is also possible to adjust the size of the desired polarization component of the adjustment light LL2.

  Further, as described above, the atomic cell 2 includes the window portion 22 that is the incident side window portion for receiving the resonance light pair LL1, the window portion 23 that is the emission side window portion for emitting the resonance light pair LL1, and the window portion. And a body portion 21 disposed between the window portion 22 and the window portion 23 to form the internal space S together with the window portion 22 and the window portion 23. The adjustment light LL2 passes through the body portion 21 and The light enters the internal space S. This allows the adjustment light LL2 to be incident on the atomic cell 2 in a direction intersecting the resonance light pair LL1.

  When the resonance light pair LL1 is the D1 line and the adjustment light LL2 is the D2 line, the intensity of the EIT signal can be efficiently improved.

<Second embodiment>
Next, a second embodiment of the present invention will be described.

  FIG. 9 is a schematic diagram for explaining a light source unit, an atomic cell, and a magnetic field generating unit included in an atomic oscillator according to a second embodiment of the present invention. FIG. 10 is a graph showing the relationship between the power density of the adjustment light (re-pump light) and the number of magnetic sublevel distributions of cesium atoms in the configuration shown in FIG.

  This embodiment is the same as the above-described first embodiment except that the configuration of the second light source unit is different.

  In the following description, the second embodiment will be described focusing on differences from the above-described embodiment, and the description of the same items will be omitted. 9 and 10, the same components as those in the above-described embodiment are denoted by the same reference numerals.

  The atomic oscillator 1A shown in FIG. 10 includes a second light source unit 32A. The second light source unit 32A is the same as the second light source unit 32 of the above-described first embodiment except that the quarter wavelength plate 323 is omitted, and the resonance light LL2b generated by the polarizer 322 and the adjustment light are used as they are. Irradiate the atomic cell 2 as LL2.

  That is, the second light source unit 32A includes the second light source 321 which is a light emitting element, and the polarizer 322 disposed between the second light source 321 and the atomic cell 2. Thereby, the linearly-polarized adjustment light LL2 can be generated. In addition, by rotating the polarizer 322 about the axis of the light from the second light source 321, it is possible to adjust the size of the desired polarization component of the adjustment light LL2.

  Further, since the adjustment light LL2 is linearly polarized light, it is possible to efficiently increase the size of a desired polarization component included in the adjustment light LL2.

For example, cesium is used as an alkali metal in the atomic cell 2, the power density (photon flux density) of the resonance light pair LL1 is fixed ( ² mW / cm ² ), and the power density of the adjustment light LL2 is changed (from 0 mW / cm ^2). Cesium atom with a stable magnetic quantum number m _F3 = 0 with respect to the magnetic quantum number of the first ground level F = 3 of the cesium atom when changed in the range up to 5 mW / cm ² ). As shown in FIG. 11, the number increases as the power density of the adjustment light LL2 increases.

On the other hand, with respect to the magnetic quantum number of the second ground level F = 4 of the cesium atom, the number of the cesium atoms at which the magnetic quantum number m _F4 = 0 is stable with respect to the magnetic field is larger than that when the adjustment light LL2 is not irradiated. is increasing. The number of cesium atoms where the magnetic quantum number m _F4 = 0 becomes the maximum (the maximum value is 2.32%) when the power density of the adjustment light LL2 is 1.1 mW / cm ² . Therefore, the adjustment light LL2 works most efficiently when the power density of the adjustment light LL2 is 1.1 mW / cm ² .

  From the above viewpoint, when the power density of the resonance light pair LL1 is P1 and the power density of the adjustment light LL2 is P2, P2 / P1 is preferably 0.1 or more and 2.5 or less. It is more preferably from 0.2 to 1.5, and even more preferably from 0.3 to 0.8. Thereby, the operation of the adjustment light LL2 can be made efficient.

  According to the second embodiment described above, the intensity of the EIT signal can be effectively improved.

<Third embodiment>
Next, a third embodiment of the present invention will be described.

FIG. 11 is a cross-sectional view of an atomic cell provided in an atomic oscillator according to a third embodiment of the present invention.
This embodiment is the same as the above-described first embodiment except that the configuration of the atomic cell is different.

  In the following description, the third embodiment will be described with a focus on differences from the above-described embodiment, and a description of similar items will be omitted. In FIG. 11, the same components as those in the above-described embodiment are denoted by the same reference numerals.

  In the atomic cell 2B provided in the atomic oscillator of the present embodiment, as shown in FIG. The light shielding film 24 is provided on the emission side of the body portion 21 for the adjustment light LL2. Thereby, it is possible to reduce the possibility that the adjustment light LL2 becomes stray light and adversely affects the characteristics.

  The constituent material of the light-shielding film 24 is not particularly limited as long as the light-shielding film 24 can have a light-shielding property. For example, a resin material, a metal material, or the like can be used. Those that can be prevented are preferred. The method for forming the light-shielding film 24 is not particularly limited. In the case of the present embodiment, for example, the light shielding film 24 can be formed on the body portion 21 by using a known film forming method.

  According to the third embodiment described above, the intensity of the EIT signal can be effectively improved.

2. Electronic Equipment The atomic oscillator as described above can be incorporated in various electronic equipment.
Hereinafter, the electronic device of the present invention will be described.

  FIG. 12 is a diagram showing a schematic configuration when the atomic oscillator of the present invention is used in a positioning system using GPS satellites.

  The positioning system 100 shown in FIG. 12 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, for example, a receiving device 302 that receives positioning information from the GPS satellite 200 with high accuracy via an antenna 301 installed at an electronic reference point (GPS continuous observation station), and the receiving device 302 receives the positioning information. A transmission device 304 for transmitting positioning information via the antenna 303.

  Here, the receiving device 302 is an electronic device including the above-described atomic oscillator 1 of the present invention as its reference frequency oscillation source. Such a receiving device 302 has excellent reliability. The positioning information received by the receiving device 302 is transmitted by the transmitting device 304 in real time.

  The GPS receiving device 400 includes a satellite receiving unit 402 that receives positioning information from the GPS satellite 200 via the antenna 401 and a base station receiving unit 404 that receives positioning information from the base station device 300 via the antenna 403. Prepare.

3. Moving Object FIG. 13 is a diagram illustrating an example of the moving 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 on the vehicle body 1501. The atomic oscillator 1 is built in such a moving object 1500.

  The electronic device of the present invention is not limited to the above-described devices. For example, a smartphone, a tablet terminal, a clock, a mobile phone, a digital still camera, an inkjet discharge device (eg, an inkjet printer), a personal computer (mobile personal computer) , Laptop personal computers), TVs, video cameras, video tape recorders, car navigation devices, pagers, electronic organizers (including those with communication functions), electronic dictionaries, calculators, electronic game machines, word processors, workstations, videophones, Security TV monitor, electronic binoculars, POS terminal, medical equipment (for example, electronic thermometer, sphygmomanometer, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish finder, various measuring devices, instruments ( An example If, gages for vehicles, aircraft, and ships), a flight simulator, terrestrial digital broadcasting, cellular base stations, can be applied to the GPS module or the like.

  As described above, the quantum interference device, the atomic oscillator, the electronic device, and the moving object of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.

  Further, the configuration of each part of the present invention can be replaced with any configuration that exhibits the same function as the above-described embodiment, and any configuration can be added. Further, in the present invention, arbitrary configurations of the above-described embodiments may be combined.

DESCRIPTION OF SYMBOLS 1 ... Atomic oscillator, 1A ... Atomic oscillator, 2 ... Atomic cell, 2B ... Atomic cell, 3 ... Light source part, 4 ... Light receiving part, 5 ... Heater, 6 ... Temperature sensor, 7 ... Magnetic field generation part, 8 ... Control part, DESCRIPTION OF SYMBOLS 21 ... Body part, 22 ... Window part, 23 ... Window part, 24 ... Light shielding film, 31 ... First light source part, 32 ... Second light source part, 32A ... Second light source part, 71 ... Coil, 81 ... Temperature control part , 82: light source control unit, 83: magnetic field control unit, 100: positioning system, 200: GPS satellite, 211: through hole, 300: base station device, 301: antenna, 302: receiving device, 303: antenna, 304: transmission Apparatus, 311 first light source, 312 １ ／ wavelength plate, 321 second light source, 322 polarizer, 323 １ ／ wavelength plate, 400 GPS receiver, 401 antenna, 402 satellite receiver , 403: antenna, 404: base station reception Reference numeral 1500: moving body, 1501: body, 1502: wheel, a: axis, a1: optical axis, a2: optical axis, b1, b2, C: direction, LL: light, LL1: resonance light pair, LL1a: resonance Light pair, LL2 adjustment light, LL2a light, LL2b resonance light, S internal space, P intersection

Claims (8)

An atomic cell having an internal space in which metal is enclosed,
A first light source unit that emits a pair of resonance lights that are circularly polarized in the same direction and resonate the metal toward the atomic cell,
Wherein have parallel polarization component in the propagation direction of the resonant light pair resonating the metal, the adjustment light is circularly polarized light or elliptically polarized light in the internal space, in a direction intersecting the resonant light pair A second light source that emits light to the atomic cell.   2. The quantum interference device according to claim 1, further comprising a magnetic field generation unit that generates a magnetic field in a direction along a propagation direction of the resonance light pair in the internal space.   The quantum interference device according to claim 2, wherein the magnetic field generator includes a Helmholtz coil. 4. The quantum interference device according to claim 1, wherein the second light source unit includes a light emitting device and a １ ／ wavelength plate disposed between the light emitting device and the atom cell. 5. apparatus. The atomic cell is arranged between the incident side window for receiving the resonance light pair, the emission side window for emitting the resonance light pair, and the incident side window and the emission side window. A body portion forming the internal space together with the entrance-side window portion and the emission-side window portion,
The adjustment light is quantum interference device according to any one of claims 1 to 4 enters the interior space through the said body portion. The resonance light pair is a D1 line;
The adjustment light is quantum interference device according to any one of 5 claims 1 is D2 line. An atomic oscillator comprising the quantum interference device according to any one of claims 1 to 6 . An electronic apparatus comprising the quantum interference device according to any one of claims 1 to 6 .

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