JP2021069038A - Atomic oscillator and frequency signal generation system - Google Patents

Abstract

To provide an atomic oscillator having a stable temperature distribution of atomic cells, and a frequency signal generation system.SOLUTION: An atomic oscillator 1 includes a light emitting element 10, an atomic cell 31 in which an alkali metal atom is housed and light LL emitted from the light emitting element 10 is incident, a heater 33 that covers the atomic cell 31 and heats the atomic cell 31 to first temperature T1, a temperature control element 36 that includes a first portion 361 that is heated to the first temperature T1 by the heater 33, and a second portion 363 that is in contact with the atomic cell 31 and is controlled by the Peltier effect to second temperature T2 which is lower than the first temperature T1, and arranged between the heater 33 and the atomic cell 31, and a light receiving element 32 that detects the light LL transmitted through the atomic cell 31.SELECTED DRAWING: Figure 2

Description

The present invention relates to an atomic oscillator and a frequency signal generation system.

As an oscillator having high-precision oscillation characteristics over a long period of time, an atomic oscillator that oscillates based on the energy transition of alkali metal atoms such as rubidium and cesium is known.
In the atomic oscillator, an alkali metal atom is enclosed in a gas cell, and the gas cell is heated to a predetermined temperature by a heater in order to keep the alkali metal atom in a gaseous state. However, since the gaseous alkali metal atoms in the gas cell decrease due to aged deterioration, there is a problem that the performance of the atomic oscillator deteriorates after long-term use.
For example, in Patent Document 1, a heat radiating portion is arranged at a position separated from a heat transfer portion that heats the gas cell, and instead of gasifying all the alkali metal atoms in the gas cell, a part thereof is a portion where the temperature of the gas cell is low. It is deposited on the heat dissipation part and enclosed as a liquid. Therefore, the decrease of gaseous alkali metal atoms due to aging is compensated by vaporizing from liquid alkali metal atoms.

Japanese Unexamined Patent Publication No. 2015-122597

However, in the atomic oscillator described in Patent Document 1, since the heat radiating portion releases the heat of the gas cell to the outside to lower the temperature of a part of the gas cell, the degree of cooling of the gas cell is easily affected by the temperature of the outside air. There is a problem that it is difficult to stabilize the temperature distribution of the gas cell.

The atomic oscillator includes a light emitting element, an atomic cell in which an alkali metal atom is housed and light emitted from the light emitting element is incident, a heater that covers the atomic cell and heats the atomic cell to a first temperature, and the above. The heater and the said portion include a first portion heated to the first temperature by the heater and a second portion in contact with the atomic cell and controlled to a second temperature lower than the first temperature by the Perche effect. It includes a temperature control element arranged between the atomic cells and a light receiving element for detecting the light transmitted through the atomic cells.

The atomic oscillator preferably includes a constant current source connected to the temperature control element.

In the above atomic oscillator, the temperature of the surface on which the light of the atomic cell is incident and the temperature of the surface on which the light of the atomic cell is emitted are preferably higher than the second temperature.

In the above atomic oscillator, the temperature control element is a Peltier element including a first temperature control surface, a second temperature control surface, and a semiconductor layer connecting the first temperature control surface and the second temperature control surface. The first portion is the first temperature control surface of the Peltier element, the second portion is the second temperature control surface of the Peltier element, and the heater is directed toward the atomic cell. It is preferable that the first portion, the semiconductor layer, and the second portion are arranged in this order.

In the above atomic oscillator, the temperature control element includes a first metal and a second metal different from the first metal, and the second portion includes the first metal and the second metal. It is preferable that it is a joint with a metal of.

In the above atomic oscillator, the first portion is preferably a portion of the first metal in contact with the heater and a portion of the second metal in contact with the heater.

In the atomic oscillator, the first portion comprises a shield disposed between the heater and the atomic cell and heated to the first temperature by the heater, the first portion being the shield of the first metal. It is preferably a contacting portion.

In the above atomic oscillator, the temperature control element is preferably a coil that generates a magnetic field.

In the above atomic oscillator, it is preferable that the first portion of the temperature control element and the constant current source are connected by a third metal.

The frequency signal generation system includes an atomic oscillator and a processing unit that processes a frequency signal from the atomic oscillator. The atomic oscillator contains a light emitting element and an alkali metal atom, and is emitted from the light emitting element. An atomic cell into which light is incident, a heater that covers the atomic cell and heats the atomic cell to a first temperature, a first portion that is heated to the first temperature by the heater, and a perche that is in contact with the atomic cell. A temperature control element arranged between the heater and the atomic cell, including a second portion controlled to a second temperature lower than the first temperature by the effect, and light transmitted through the atomic cell. Includes a light receiving element to detect.

The schematic diagram which shows the atomic oscillator which concerns on 1st Embodiment. The cross-sectional view which shows typically the atomic oscillator which concerns on 1st Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 1st Embodiment. FIG. 3 is a cross-sectional view taken along the line AA of FIG. The cross-sectional view which shows typically the atomic cell unit which concerns on 2nd Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 3rd Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 4th Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 5th Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 6th Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 7th Embodiment. The cross-sectional view which shows typically the atomic cell unit which concerns on 8th Embodiment. The schematic block diagram which shows the frequency signal generation system which concerns on 9th Embodiment.

1. 1. First Embodiment First, the atomic oscillator 1 according to the first embodiment will be described with reference to the drawings.
FIG. 1 is a schematic view showing an atomic oscillator 1 according to the present embodiment.

The atomic oscillator 1 has a quantum interference effect (CPT) in which when an alkali metal atom is simultaneously irradiated with two resonance lights having specific different wavelengths, the two resonance lights are transmitted without being absorbed by the alkali metal atoms. : Coherent Population Trapping) is used as an atomic oscillator. The phenomenon caused by this quantum interference effect is also called an electromagnetically induced transparency (EIT) phenomenon. Further, the atomic oscillator 1 according to the present embodiment may be an atomic oscillator utilizing a double resonance phenomenon caused by light and microwaves.

As shown in FIG. 1, the atomic oscillator 1 includes a light emitting element 10, an optical system unit 20, an atomic cell unit 30, and a control unit 40 that controls the light emitting element 10 and the atomic cell unit 30.

The light emitting element 10 emits linearly polarized light LL containing two types of light having different frequencies. The light emitting element 10 is a vertical cavity surface emitting laser (VCSEL) or the like.

The optical system unit 20 is arranged between the light emitting element 10 and the atomic cell unit 30. The optical system unit 20 includes a neutral density filter 21, a lens 22, and a quarter wave plate 23.

The neutral density filter 21 reduces the intensity of the light LL emitted from the light emitting element 10. The lens 22 adjusts the radiation angle of the light LL. Specifically, the lens 22 makes the light LL parallel light. The quarter wave plate 23 converts two types of light contained in the light LL having different frequencies from linearly polarized light to circularly polarized light.

The atomic cell unit 30 includes an atomic cell 31, a light receiving element 32, a heater 33, a temperature sensor 34, a coil 35, and a temperature control element 36.

The atomic cell 31 transmits the light LL emitted from the light receiving element 32. The atomic cell 31 contains an alkali metal atom. The alkali metal atom has an energy level of a three-level system consisting of two different ground levels and an excited level. The light LL emitted from the light emitting element 10 is incident on the atomic cell 31 through the neutral density filter 21, the lens 22, and the quarter wave plate 23.

The light receiving element 32 receives and detects the light LL that has passed through the atomic cell 31. The light receiving element 32 is, for example, a photodiode.

The heater 33 controls the atomic cell 31 so that it reaches the first temperature T1. The heater 33 heats the alkali metal atoms contained in the atomic cell 31 and puts at least a part of the alkali metal atoms into a gas state. The first temperature T1 is, for example, 60 ° C. or higher and 70 ° C. or lower.

The temperature sensor 34 detects the temperature of the atomic cell 31. The temperature sensor 34 is, for example, various temperature sensors such as a thermistor and a thermoelectric pair.
The coil 35 applies a magnetic field in a predetermined direction to the alkali metal atom housed in the atomic cell 31 to Zeeman split the energy level of the alkali metal atom.

When an alkali metal atom is irradiated with a circularly polarized resonance light pair in a state where the alkali metal atom is Zeeman-divided, the alkali metal atom having a desired energy level among a plurality of Zeeman-divided levels of the alkali metal atom The number is relatively large relative to the number of alkali metal atoms at other energy levels. Therefore, the number of atoms that express the desired EIT phenomenon increases, and the desired EIT signal becomes large. As a result, the oscillation characteristics of the atomic oscillator 1 can be improved.

The temperature control element 36 utilizes the Perche effect to cool a part of the atomic cell 31 so as to have a second temperature T2 lower than the first temperature T1. The second temperature T2 is, for example, a temperature lower than the first temperature T1 by 1 ° C. or more. The temperature control element 36 is, for example, a Peltier element.

The control unit 40 includes a temperature control circuit 41, a constant current source 42, a magnetic field control circuit 43, and a light source control circuit 44.

The temperature control circuit 41 controls the energization of the heater 33 so that the inside of the atomic cell 31 has a desired temperature based on the detection result of the temperature sensor 34.

The constant current source 42 passes a direct current through the temperature control element 36 and controls a part of the atomic cell 31 so as to reach the second temperature T2.

The magnetic field control circuit 43 controls the energization of the coil 35 so that the magnetic field generated by the coil 35 becomes constant.

The light source control circuit 44 controls the frequencies of two types of light contained in the light LL emitted from the light receiving element 32 so that the EIT phenomenon occurs based on the detection result of the light receiving element 32. Here, the EIT phenomenon occurs when these two types of light become a resonance light pair having a frequency difference corresponding to an energy difference between two base levels of an alkali metal atom housed in an atomic cell 31. The light source control circuit 44 includes a voltage-controlled oscillator (not shown) whose oscillation frequency is controlled so as to stabilize in synchronization with the control of two types of light frequencies, and this voltage-controlled oscillator (VCO). : Voltage Controlled Oscillator) output signal is output as clock signal CLK which is the output signal of the atomic oscillator 1.

Next, a specific configuration of the atomic oscillator 1 will be described.
FIG. 2 is a cross-sectional view schematically showing the atomic oscillator 1 according to the first embodiment. FIG. 3 is a cross-sectional view schematically showing the atomic cell unit 30 according to the first embodiment. FIG. 4 is a cross-sectional view taken along the line AA of FIG. Further, in FIGS. 2 to 4 and 5 to 11 described later, the X-axis, the Y-axis, and the Z-axis are shown as three axes orthogonal to each other.

As shown in FIG. 2, the atomic oscillator 1 includes a light emitting element 10, an optical system unit 20, an atomic cell unit 30, a control unit 40, and an outer container 50.

The light emitting element 10 is arranged on the light source substrate 11. The light source substrate 11 is arranged on a heat insulating member 53 provided on the outer base 51, and is fixed to the outer base 51 together with the heat insulating member 53 by, for example, a screw (not shown). The light emitting element 10 is electrically connected to the light source control circuit 44 of the control unit 40.

The optical system unit 20 is arranged on the outer base 51 via the heat insulating member 53. The optical system unit 20 includes a neutral density filter 21, a lens 22, a quarter wave plate 23, and a holder 24 that holds them. The holder 24 is fixed to the outer base 51 together with the heat insulating member 53 by, for example, a screw (not shown).

The holder 24 is provided with a through hole, which is a passage region for light LL. In the through hole, the neutral density filter 21, the lens 22, and the 1/4 wave plate 23 are arranged in this order from the light emitting element 10 side.

The atomic cell unit 30 is arranged on the outer base 51 via the heat insulating member 53, and is fixed to the outer base 51 together with the heat insulating member 53 by, for example, a screw (not shown).
As shown in FIGS. 3 and 4, the atomic cell unit 30 includes an atomic cell 31, a light receiving element 32, a heater 33, a temperature sensor 34, a coil 35, a temperature control element 36, and a shield serving as an inner container. 37 and. The atomic cell 31, the heater 33, and the shield 37 have a cylindrical shape in the longitudinal direction along the X axis, the shield 37 is arranged inside the heater 33, and the atomic cell 31 and the light receiving element 32 are inside the shield 37. , The temperature sensor 34, the coil 35, and the temperature control element 36 are arranged.

The atomic cell 31 contains gaseous alkali metals such as rubidium, cesium, and sodium. If necessary, the atomic cell 31 may contain a rare gas such as argon or an inert gas such as nitrogen as a buffer gas together with the alkali metal atom.

The light LL emitted from the light emitting element 10 is incident on the atomic cell 31. The material of the wall portion of the atomic cell 31 is, for example, glass. The wall portion of the atomic cell 31 defines the internal space S of the atomic cell 31. The internal space S of the atomic cell 31 is, for example, the saturated vapor pressure of the alkali metal atom. The light LL emitted from the light emitting element 10 passes through the internal space S. For example, a liquid alkali metal atom 60 is present on the surface of the atomic cell 31 on the internal space S side at a position where the atomic cell 31 and the temperature control element 36 are in contact with each other. As a result, when the alkali metal atom of the gas in the internal space S is reduced due to the reaction with the wall portion of the atomic cell 31, the liquid alkali metal atom 60 is vaporized, and the concentration of the alkali metal atom of the gas in the internal space S is reduced. Can be kept constant.

The light receiving element 32 detects the light LL transmitted through the atomic cell 31 and is arranged on the side opposite to the light emitting element 10 side of the atomic cell 31. The light receiving element 32 is electrically connected to the light source control circuit 44 of the control unit 40.

The heater 33 houses the atomic cell 31, the light receiving element 32, the temperature sensor 34, the coil 35, the temperature control element 36, and the shield 37, and covers the atomic cell 31. The heater 33 is electrically connected to the temperature control circuit 41 of the control unit 40.
The heater 33 heats the atomic cell 31 so as to reach the first temperature T1 based on the temperature information of the temperature sensor 34 arranged in the atomic cell 31. The heater 33 may cover the entire atomic cell 31 with a sheet heater, for example, or may be a combination of a heat generating element and a metal having high thermal conductivity such as copper.

A plurality of temperature sensors 34 are arranged in the atomic cell 31 and detect the temperature of the atomic cell 31. The number and arrangement of the temperature sensors 34 are not limited as long as the heater 33 can heat the atomic cells 31 to the first temperature T1. For example, the temperature sensor 34 may be one or may be arranged outside the shield 37.
The coil 35 is, for example, a solenoid type coil provided by winding along the outer circumference of the atomic cell 31, or a pair of Helmholtz type coils facing each other via the atomic cell 31. The coil 35 generates a magnetic field inside the atomic cell 31 in the direction along the optical axis LA of the optical LL. As a result, the gap between different degenerate energy levels of the alkali metal atom contained in the atomic cell 31 can be widened by Zeeman splitting to improve the resolution and reduce the line width of the EIT signal.
The temperature sensor 34 and the coil 35 are electrically connected to the temperature control circuit 41 and the magnetic field control circuit 43 of the control unit 40.

A plurality of temperature control elements 36 are arranged between the heater 33 for heating the atomic cell 31 to the first temperature T1 and the atomic cell 31, and are the first temperature control surface P1 and the second portion 363 which are the first portion 361. It is a Peltier element including a second temperature control surface P2 and a semiconductor layer 362 connecting the first temperature control surface P1 and the second temperature control surface P2. From the heater 33 toward the atomic cell 31, the first portion 361, the semiconductor layer 362, and the second portion 363 are arranged in this order. The temperature control element 36 is electrically connected to the constant current source 42 of the control unit 40 by two wirings (not shown) from the first portion 361.
The first portion 361 of the temperature control element 36 is heated to the first temperature T1 by the heater 33, and the second portion 363 in contact with the atomic cell 31 is controlled to the second temperature T2 lower than the first temperature T1 by the Perche effect. Therefore, a part of the atomic cell 31 in contact with the second portion 363 of the temperature control element 36 is cooled to the second temperature T2, which is lower than the first temperature T1. This is because a direct current is passed through the temperature control element 36 from the constant current source 42, so that a temperature difference can be generated between the first temperature control surface P1 and the second temperature control surface P2 by the Perche effect, and the atomic cell 31 can be generated. This is because the second temperature control surface P2 in contact with the second temperature control surface P2 can absorb heat.
Therefore, in the internal space S of the cooled atomic cell 31, the liquid alkali metal atom 60 in which the gaseous alkali metal atom is cooled and liquefied can be generated.

The position of the temperature control element 36 along the optical axis LA is arbitrary, but is preferably near the center of the atomic cell 31. For example, it may be arranged in a range of 1/3 or more and 2/3 or less of the length along the optical axis LA of the atomic cell 31. Since the portion having the second temperature T2 can be separated from both the surface M1 on which the light LL of the atomic cell 31 is incident and the surface M2 from which the light of the atomic cell 31 is emitted, a liquid alkali metal atom on the surface M1 and the surface M2. 60 can be hard to adhere. As a result, the intensity of the light LL incident on the atomic cell 31 and the intensity of the light LL emitted from the atomic cell 31 are less likely to decrease, so that the decrease in the frequency accuracy of the atomic oscillator 1 can be suppressed.

The atomic cell 31 is heated by the heater 33 so that the temperature of the surface M1 and the temperature of the surface M2 become the first temperature T1 which is higher than the second temperature T2.

The shield 37 houses the atomic cell 31, the light receiving element 32, the temperature sensor 34, the coil 35, and the temperature control element 36, and is arranged inside the heater 33. A transparent member 37a such as glass is arranged on the wall portion of the shield 37 on the light emitting element 10 side. Therefore, the light LL emitted from the light emitting element 10 can be incident on the atomic cell 31.

The material of the shield 37 is, for example, iron, silicon iron, permalloy, supermalloy, sendust, copper and the like. By using such a material, the atomic cell 31 can block magnetism from the outside. As a result, it is possible to suppress the influence of the alkali metal atoms in the atomic cell 31 by the magnetism from the outside and to stabilize the oscillation characteristics of the atomic oscillator 1. Here, "suppressing" includes a case where a certain event is completely stopped from occurring and a case where the degree of the certain event is reduced.

As shown in FIG. 2, the control unit 40 has a circuit board 45. The circuit board 45 is fixed to the outer base 51 via a plurality of lead pins 54. An IC (Integrated Circuit) chip (not shown) is arranged on the circuit board 45, and the IC chip functions as a temperature control circuit 41, a magnetic field control circuit 43, and a light source control circuit 44. The IC chip is electrically connected to the light emitting element 10 and the atomic cell unit 30.

The outer container 50 houses the light emitting element 10, the optical system unit 20, the atomic cell unit 30, and the control unit 40. The outer container 50 has an outer base portion 51 and an outer lid portion 52 that is separate from the outer base portion 51. The material of the outer container 50 is, for example, the same as that of the shield 37. Therefore, the outer container 50 can block the magnetism from the outside, and can suppress the influence of the alkali metal atom in the atomic cell 31 by the magnetism from the outside.

In the present embodiment, the configuration is such that four temperature control elements 36 are arranged, but the present invention is not limited to this, and the number of temperature control elements 36 may be one or more.

In the atomic oscillator 1 of the present embodiment, since the atomic cell 31 is arranged inside the heater 33 whose temperature is stabilized, the temperature of the atomic cell 31 is not easily affected by the temperature of the outside air. Further, by using the Perche effect for cooling and creating a constant temperature difference between the first portion 361 and the second portion 363 based on the temperature of the heater 33, a part of the atomic cell 31 is formed inside the heater 33. Since the temperature of the heater 33 is less likely to fluctuate even when the heater 33 is cooled, the temperature distribution of the atomic cell 31 can be stabilized. Therefore, a highly accurate atomic oscillator 1 can be obtained.

Further, since the temperature control element 36 is connected to the constant current source 42, the temperature difference caused by the Perche effect is kept constant. Therefore, the second portion 363 in contact with the atomic cell 31 of the temperature control element 36 can be stably controlled to the second temperature T2.

Further, since the temperature of the surface M1 on which the light LL of the atomic cell 31 is incident and the temperature of the surface M2 from which the light LL of the atomic cell 31 is emitted are higher than the second temperature T2, the alkali metal atoms of the gas are on the two surfaces. Does not precipitate as a liquid, so that it does not block light and stable oscillation characteristics can be obtained.

Further, since the temperature control element 36 is arranged in the order of the first portion 361, the semiconductor layer 362, and the second portion 363 from the heater 33 toward the atomic cell 31, the first temperature control surface P1 serving as the first temperature T1 A temperature difference can be generated between the temperature control surface P2 and the second temperature control surface P2 due to the Perche effect, and heat can be absorbed by the second temperature control surface P2 in contact with the atomic cell 31. Therefore, a part of the atomic cell 31 can be cooled while the temperature distribution of the atomic cell 31 is stably maintained.

2. Second Embodiment Next, the atomic oscillator 1a according to the second embodiment will be described with reference to FIG.
FIG. 5 is a cross-sectional view schematically showing the atomic cell unit 30a according to the second embodiment.

The atomic oscillator 1a of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configuration of the atomic cell unit 30a is different from that of the atomic oscillator 1 of the first embodiment. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

In the atomic cell unit 30a of the atomic oscillator 1a, as shown in FIG. 5, the temperature control element 36 is arranged in the order of the first portion 361, the semiconductor layer 362, and the second portion 363 from the light emitting element 10 side, and the first portion The 361 is heated to the first temperature T1, and the second portion 363 is cooled to the second temperature T2 by the Perche effect.
A heat transfer member 70 for transferring the heat of the heater 33 is arranged between the atomic cell 31 and the coil 35 and between the light receiving element 32 and the shield 37.
On the light receiving element 32 side of the temperature control element 36, a heat transfer member 71 in contact with the second portion 363 and the atomic cell 31 is arranged. The heat transfer member 71 is separated from the heat transfer member 70 and the shield 37. The heat transfer member 71 can transfer the heat of the second portion 363 cooled to the second temperature T2 to the atomic cell 31 and cool a part of the atomic cell 31 in contact with the heat transfer member 71. Therefore, in the internal space S of the atomic cell 31 in contact with the heat transfer member 71, the liquid alkali metal atom 60 in which the gaseous alkali metal atom is cooled and liquefied can be generated.

The material of the heat transfer member 70 and the heat transfer member 71 is preferably a material having high thermal conductivity without hindering the magnetic field from the coil 35 to the atomic cell 31, and is, for example, a metal such as aluminum.

With such a configuration, the temperature distribution of the atomic cell 31 can be stabilized while a part of the atomic cell 31 is cooled. Further, since the portion to be cooled is on the light receiving element 32 side of the atomic cell 31, that is, near the surface M2, the intensity of the light LL irradiated on the gaseous alkali metal atom in the atomic cell 31 is unlikely to fluctuate. Therefore, it is possible to suppress a decrease in frequency accuracy of the atomic oscillator 1.

3. 3. Third Embodiment Next, the atomic oscillator 1b according to the third embodiment will be described with reference to FIG.
FIG. 6 is a cross-sectional view schematically showing the atomic cell unit 30b according to the third embodiment.

The atomic oscillator 1b of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configuration of the atomic cell unit 30b is different from that of the atomic oscillator 1 of the first embodiment. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 6, the atomic cell unit 30b of the atomic oscillator 1b has a temperature control element 36 arranged in the order of the first portion 361, the semiconductor layer 362, and the second portion 363 from the light emitting element 10 side, and the light receiving element 32 side. A temperature control element 36 arranged in the order of the first portion 361, the semiconductor layer 362, and the second portion 363 is arranged between the atomic cell 31 and the coil 35, and the heat transfer member 72 is arranged between the two temperature control elements 36. Is placed. Since the two second portions 363 are cooled to the second temperature T2 by the Perche effect, the heat transfer member 72 is cooled to the second temperature T2, and a part of the atomic cell 31 in contact with the heat transfer member 72 is cooled. be able to. Therefore, in the internal space S of the atomic cell 31 in contact with the heat transfer member 72, the liquid alkali metal atom 60 in which the gaseous alkali metal atom is cooled and liquefied can be generated.
Further, a heat transfer member 70 for holding the heat of the heater 33 is arranged between the atomic cell 31, the coil 35, and the shield 37.

With such a configuration, the temperature distribution of the atomic cell 31 can be stabilized while a part of the atomic cell 31 is cooled.

4. Fourth Embodiment Next, the atomic oscillator 1c according to the fourth embodiment will be described with reference to FIG. 7.
FIG. 7 is a cross-sectional view schematically showing the atomic cell unit 30c according to the fourth embodiment.

The atomic oscillator 1c of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configuration of the atomic cell unit 30c and the configuration of the temperature control element 36c are different from those of the atomic oscillator 1 of the first embodiment. is there. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 7, the atomic cell unit 30c of the atomic oscillator 1c is provided with a through hole 33c in the heater 33, and the shield 37 is also provided with a through hole 37c at a position overlapping the through hole 33c. In the through holes 33c and 37c, a temperature control element 36c composed of a first metal 38a and a second metal 38b different from the first metal 38a is arranged.
In the temperature control element 36c, a second portion 392, which is a joint portion between the first metal 38a and the second metal 38b, is arranged in contact with the atomic cell 31, a portion in contact with the heater 33 of the first metal 38a, and a portion in contact with the heater 33. , The first portion 391, 393, which is a portion of the second metal 38b in contact with the heater 33, is arranged in contact with the heater 33. Further, the first portions 391 and 393 are electrically connected to the constant current source 42 by the third metals 38c and 38d serving as wiring. In this embodiment, a part of the wiring from the first metal 38a and the second metal 38b to the constant current source 42 is not shown. Further, the first portion 391, 393 may be covered with the first metal 38a and the second metal 38b, which may not be in direct contact with the heater 33.

Generally, when both ends of two different metal wires are connected to each other and a temperature difference is applied between the two contacts, an electromotive force is generated. On the contrary, when a current and a voltage are passed through the two contacts, a temperature difference can be generated between the two contacts, and a Perche effect can be obtained.
Therefore, the temperature control element 36c can have a constant temperature difference from the second portion 392 with reference to the first portion 391, 393 heated to the first temperature T1 by the heater 33 due to the Perche effect. Therefore, the second portion 392 can be cooled to the second temperature T2, and a part of the atomic cell 31 in contact with the second portion 392 can be cooled by absorbing heat.
Examples of the combination of the first metal 38a and the second metal 38b include chromel and alumel, chromel and constantan, platinum rhodium alloy and platinum, nichrome and gold-iron alloy, and the like.

According to this configuration, by contacting the second portion 392, which is the junction between the first metal 38a and the second metal 38b of the temperature control element 36c, with the atomic cell 31, the second portion 392 becomes an atom due to the Perche effect. A part of the atomic cell 31 can be cooled while absorbing the heat of the cell 31 and maintaining the temperature distribution of the atomic cell 31 in a stable manner.

Further, by having a portion in contact with the heater 33 of the first metal 38a and a portion in contact with the heater 33 of the second metal 38b, the first portion 391, 393 utilizes the Perche effect, and the first portion 391 , 393 can be used as a reference to make a constant temperature difference from the second part 392. Therefore, while maintaining a stable temperature distribution of the atomic cell 31, the part in contact with the second part 392 of the atomic cell 31 Can be cooled.

Further, since the first portion 391, 393 and the constant current source 42 are connected by the third metal 38c, 38d, by using an inexpensive material for the third metal 38c, 38d, the atomic oscillator 1c is lowered. Cost can be reduced.

5. Fifth Embodiment Next, the atomic oscillator 1d according to the fifth embodiment will be described with reference to FIG.
FIG. 8 is a cross-sectional view schematically showing the atomic cell unit 30d according to the fifth embodiment.

The atomic oscillator 1d of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configuration of the atomic cell unit 30d and the configuration of the temperature control element 36d are different from those of the atomic oscillator 1 of the first embodiment. is there. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 8, in the atomic cell unit 30d of the atomic oscillator 1d, the second portion 392 of the temperature control element 36d is arranged in contact with the atomic cell 31, and the first portions 391 and 393 of the temperature control element 36d are shields 37. It is placed in contact with.

According to this configuration, since the first portion 391 of the first metal 38a is in contact with the shield 37 heated to the first temperature T1 by the heater 33, the first portion in contact with the shield 37 is utilized by utilizing the Perche effect. With the temperature of 391 as a reference, a constant temperature difference can be obtained from the second portion 392. Therefore, the portion of the atomic cell 31 in contact with the second portion 392 can be cooled while maintaining the stable temperature distribution of the atomic cell 31.

6. Sixth Embodiment Next, the atomic oscillator 1e according to the sixth embodiment will be described with reference to FIG.
FIG. 9 is a cross-sectional view schematically showing the atomic cell unit 30e according to the sixth embodiment.

The atomic oscillator 1e of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configuration of the atomic cell unit 30e and the configuration of the temperature control element 36e are different from those of the atomic oscillator 1 of the first embodiment. is there. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

In the atomic cell unit 30e of the atomic oscillator 1e, as shown in FIG. 9, the second portion 392 of the temperature control element 36e is arranged in contact with the atomic cell 31, and the first portions 391 and 393 of the temperature control element 36e are shields 37. It is placed in contact with. The third metals 38c and 38d, which are the wirings from the first metal 38a and the second metal 38b to the constant current source 42, are twisted and arranged between the coil 35 and the shield 37.

According to this configuration, the same effect as that of the fifth embodiment can be obtained. Further, since the third metals 38c and 38d to be the wiring are twisted together, the generation of the current magnetic field due to the wiring can be suppressed, and stable oscillation characteristics can be obtained.

7. Seventh Embodiment Next, the atomic oscillator 1f according to the seventh embodiment will be described with reference to FIG.
FIG. 10 is a cross-sectional view schematically showing the atomic cell unit 30f according to the seventh embodiment.

The atomic oscillator 1f of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configuration of the atomic cell unit 30f and the configuration of the temperature control element 36f are different from those of the atomic oscillator 1 of the first embodiment. is there. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 10, the atomic cell unit 30f of the atomic oscillator 1f includes a cylindrical first metal 70a covering the atomic cell 31 and a cylindrical second metal 70b covering the atomic cell 31 and the light receiving element 32. A temperature control element 36f composed of ,, is arranged. The first metal 70a and the second metal 70b are joined at the central portion in the longitudinal direction of the atomic cell 31, and this joint portion is in contact with the atomic cell 31 as the second portion 392. The end of the first metal 70a opposite to the second portion 392 is the first portion 391, and the end of the second metal 70b opposite to the second portion 392 is the first portion 393. Since each is in contact with the shield 37 heated by the heater 33, use the Perche effect to make a constant temperature difference from the second part 392 based on the temperature of the first part 391, 393 that is in contact with the shield 37. Can be done.

According to this configuration, since the atomic cell 31 is covered with the first metal 70a and the second metal 70b having a shape having a larger heat capacity than the wire rod or the like, the temperature distribution of the atomic cell 31 is maintained stably. In the state, the portion of the atomic cell 31 in contact with the second portion 392 can be cooled.

8. Eighth Embodiment Next, 1 g of the atomic oscillator according to the eighth embodiment will be described with reference to FIG.
FIG. 11 is a cross-sectional view schematically showing 30 g of the atomic cell unit according to the eighth embodiment.

The atomic oscillator 1g of the present embodiment is the same as the atomic oscillator 1 of the first embodiment except that the configurations of the atomic cell unit 30g and the temperature control element 36g are different from those of the atomic oscillator 1 of the first embodiment. is there. The differences from the first embodiment described above will be mainly described, and the same items will be designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 11, in the atomic cell unit 30 g of the atomic oscillator 1 g, a temperature control element 36 g composed of a coil is arranged between the atomic cell 31 and the heater 33. The temperature control element 36g comprises a coil composed of a first metal 35a, a second metal 35b, and third metals 35c and 35d. The first metal 35a and the second metal 35b are joined at the central portion in the longitudinal direction of the atomic cell 31, and this joining portion becomes the second portion 392. A heat transfer member 74 in contact with the second portion 392 and the atomic cell 31 is arranged between the second portion 392 and the atomic cell 31. A third metal 35c is joined to the first portion 391 of the end opposite to the second portion 392 of the first metal 35a, and the end of the second metal 35b opposite to the second portion 392. A third metal 35d is joined to the first portion 393. Since the first part 391, 393 is heated by the heater 33 to become the first temperature T1, the temperature of the first part 391, 393 is used as a reference to make a constant temperature difference from the second part 392. be able to. Therefore, the heat transfer member 74 in contact with the second portion 392 can be cooled, and a part of the atomic cell 31 in contact with the heat transfer member 74 can be cooled.

According to this configuration, since the coil for generating a magnetic field is configured by the temperature control element 36 g, a magnetic field in a predetermined direction can be applied to the alkali metal atoms in the atomic cell 31 to obtain stable oscillation characteristics. Further, since the number of parts can be reduced as compared with the case where the temperature control element 36 g and the coil are separate, the size and cost of the atomic oscillator 1 g can be reduced.

9. Ninth Embodiment Next, the frequency signal generation system according to the ninth embodiment will be described with reference to FIG. The following clock transmission system (timing server) 90 is an example of a frequency signal generation system.
FIG. 12 is a schematic configuration diagram showing a frequency signal generation system according to a ninth embodiment.

The clock transmission system 90 includes 1 to 1 g of the atomic oscillator according to the present embodiment. In the following, as an example, the clock transmission system 90 including the atomic oscillator 1 will be described.

The clock transmission system 90 is a system that matches the clocks of each device in the time division multiplexing network, and has an N (Normal) system and an E (Emergency) system redundant configuration.

As shown in FIG. 12, the clock transmission system 90 is the upper level of the A station, the N system clock supply device 901 and the SDH (Synchronous Digital Hierarchy) device 902, and the upper level of the B station, which is the E system. The clock supply device 903 and the SDH device 904, and the lower clock supply device 905 and the SDH device 906, 907 of the C station are provided. The clock supply device 901 has an atomic oscillator 1 and generates an N-system clock signal. The atomic oscillator 1 in the clock supply device 901 generates a clock signal in synchronization with a more accurate clock signal from the master clocks 908 and 909 including the atomic oscillator using cesium. The clock supply devices 901 and 903 correspond to a processing unit that processes a frequency signal from the atomic oscillator 1.

The SDH device 902 transmits and receives a main signal based on the clock signal from the clock supply device 901, superimposes the N system clock signal on the main signal, and transmits the N system clock signal to the lower clock supply device 905. The clock supply device 903 has an atomic oscillator 1 and generates an E-system clock signal. The atomic oscillator 1 in the clock supply device 903 generates a clock signal in synchronization with a more accurate clock signal from the master clocks 908 and 909 including the atomic oscillator using cesium.

The SDH device 904 transmits and receives a main signal based on the clock signal from the clock supply device 903, superimposes the E system clock signal on the main signal, and transmits the clock signal to the lower clock supply device 905. The clock supply device 905 receives the clock signals from the clock supply devices 901 and 903, and generates a clock signal in synchronization with the received clock signal.

The clock supply device 905 usually generates a clock signal in synchronization with the N-system clock signal from the clock supply device 901. Then, when an abnormality occurs in the N system, the clock supply device 905 generates a clock signal in synchronization with the clock signal of the E system from the clock supply device 903. By switching from the N system to the E system in this way, stable clock supply can be ensured and the reliability of the clock path network can be improved. The SDH device 906 transmits and receives a main signal based on the clock signal from the clock supply device 905. Similarly, the SDH device 907 transmits and receives a main signal based on the clock signal from the clock supply device 905. As a result, the device of station C can be synchronized with the device of station A or station B.

The frequency signal generation system according to this embodiment is not limited to the clock transmission system 90. The frequency signal generation system includes a system in which the atomic oscillator 1 is mounted and is composed of various devices that utilize the frequency signal of the atomic oscillator 1 and a plurality of devices.

The frequency signal generation system according to the present embodiment is, for example, a smartphone, a tablet terminal, a clock, a mobile phone, a digital still camera, a liquid ejection device (for example, an inkjet printer), a personal computer, a television, a video camera, a video tape recorder, and a car navigation system. Devices, pagers, electronic notebooks, electronic dictionaries, calculators, electronic game devices, word processors, workstations, videophones, security TV monitors, electronic binoculars, POS (point of sales) terminals, medical equipment (eg electronic thermometers, blood pressure monitors, etc.) Blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope, electrocardiograph), fish finder, GNSS (Global Navigation Satellite System) frequency standard, various measuring devices, instruments (for example, automobiles, aircraft, ships) Instruments), flight simulators, terrestrial digital broadcasting systems, mobile phone base stations, mobile objects (automobiles, aircraft, ships, etc.).

The contents derived from the embodiment will be described below.

The atomic oscillator includes a light emitting element, an atomic cell in which an alkali metal atom is housed and light emitted from the light emitting element is incident, a heater that covers the atomic cell and heats the atomic cell to a first temperature, and the above. The heater and the said portion include a first portion heated to the first temperature by the heater and a second portion in contact with the atomic cell and controlled to a second temperature lower than the first temperature by the Perche effect. It includes a temperature control element arranged between the atomic cells and a light receiving element for detecting the light transmitted through the atomic cells.

According to this configuration, since the atomic cell is arranged inside the temperature stabilized by the heater, the temperature of the atomic cell is not easily affected by the temperature of the outside air. In addition, even if a part of the atomic cell is cooled inside the heater by using the Perche effect for cooling and creating a constant temperature difference between the first part and the second part based on the temperature of the heater. Since the temperature of the heater is less likely to fluctuate, the temperature distribution of the atomic cell can be stabilized. Therefore, a highly accurate atomic oscillator can be obtained.

The atomic oscillator preferably includes a constant current source connected to the temperature control element.

According to this configuration, since the temperature control element is connected to the constant current source, the second portion of the temperature control element in contact with the atomic cell can be stably controlled to the second temperature by utilizing the Perche effect. ..

In the above atomic oscillator, the temperature of the surface on which the light of the atomic cell is incident and the temperature of the surface on which the light of the atomic cell is emitted are preferably higher than the second temperature.

According to this configuration, the temperature of the surface on which the light of the atomic cell is incident and the temperature of the surface on which the light of the atomic cell is emitted are higher than the second temperature, so that gaseous alkali metal atoms are liquefied on the two surfaces. Since it does not adhere, it does not block light and stable oscillation characteristics can be obtained.

In the above atomic oscillator, the temperature control element is a Peltier element including a first temperature control surface, a second temperature control surface, and a semiconductor layer connecting the first temperature control surface and the second temperature control surface. The first portion is the first temperature control surface of the Peltier element, the second portion is the second temperature control surface of the Peltier element, and the heater is directed toward the atomic cell. It is preferable that the first portion, the semiconductor layer, and the second portion are arranged in this order.

According to this configuration, since the temperature control elements are arranged in the order of the first portion, the semiconductor layer, and the second portion from the heater to the atomic cell, the first temperature control surface and the second temperature control, which are the first temperatures, are arranged. A temperature difference can be generated between the surface and the surface by the Perche effect, and heat can be absorbed by the second temperature control surface in contact with the atomic cell. Therefore, a part of the atomic cell can be cooled while the temperature distribution of the atomic cell is stably maintained.

In the above atomic oscillator, the temperature control element includes a first metal and a second metal different from the first metal, and the second portion includes the first metal and the second metal. It is preferable that it is a joint with a metal of.

According to this configuration, by contacting the second portion, which is the junction between the first metal and the second metal of the temperature control element, with the atomic cell, the second portion absorbs the heat of the atomic cell due to the Perche effect. , A part of the atomic cell can be cooled while the temperature distribution of the atomic cell is stably maintained.

In the above atomic oscillator, the first portion is preferably a portion of the first metal in contact with the heater and a portion of the second metal in contact with the heater.

According to this configuration, the temperature of the first portion on the heater side is utilized by utilizing the Perche effect in the portion of the first metal in contact with the heater and the portion of the second metal in contact with the heater. Since a constant temperature difference can be obtained from the second portion based on the above, the portion in contact with the second portion of the atomic cell can be cooled while the temperature distribution of the atomic cell is stably maintained.

In the atomic oscillator, the first portion comprises a shield disposed between the heater and the atomic cell and heated to the first temperature by the heater, the first portion being the shield of the first metal. It is preferably a contacting portion.

According to this configuration, since the first part of the first metal is in contact with the shield heated to the first temperature by the heater, the Perche effect is used and the temperature of the first part in contact with the shield is used as a reference. It is possible to make a constant temperature difference from the second part. Therefore, it is possible to cool the portion in contact with the second portion of the atomic cell while maintaining the temperature distribution of the atomic cell in a stable manner.

In the above atomic oscillator, the temperature control element is preferably a coil that generates a magnetic field.

According to this configuration, by configuring a coil that generates a magnetic field with a temperature control element, a magnetic field in a predetermined direction can be applied to the alkali metal atoms in the atomic cell, and stable oscillation characteristics can be obtained. Further, since the number of parts can be reduced as compared with the case where the temperature control element and the coil are separate, the size and cost of the atomic oscillator can be reduced.

In the above atomic oscillator, it is preferable that the first portion of the temperature control element and the constant current source are connected by a third metal.

According to this configuration, since the first portion and the constant current source are connected by the third metal, the cost of the atomic oscillator can be reduced by using an inexpensive material for the third metal.

The frequency signal generation system includes an atomic oscillator and a processing unit that processes a frequency signal from the atomic oscillator. The atomic oscillator contains a light emitting element and an alkali metal atom, and is emitted from the light emitting element. An atomic cell into which light is incident, a heater that covers the atomic cell and heats the atomic cell to a first temperature, a first portion that is heated to the first temperature by the heater, and a perche that is in contact with the atomic cell. A temperature control element arranged between the heater and the atomic cell, including a second portion controlled to a second temperature lower than the first temperature by the effect, and light transmitted through the atomic cell. Includes a light receiving element to detect.

According to this configuration, since it is provided with a high-precision atomic oscillator, it is possible to provide a high-performance frequency signal generation system.

1,1a, 1b, 1c, 1d, 1e, 1f, 1g ... Atomic oscillator, 10 ... Light source, 11 ... Light source substrate, 20 ... Optical system unit, 21 ... Dimming filter, 22 ... Lens, 23 ... 1/4 Frequency plate, 24 ... holder, 30 ... atomic cell unit, 31 ... atomic cell, 32 ... light receiving element, 33 ... heater, 34 ... temperature sensor, 35 ... coil, 36 ... temperature control element, 37 ... shield, 40 ... control unit , 41 ... Temperature control circuit, 42 ... Constant current source, 43 ... Magnetic field control circuit, 44 ... Light source control circuit, 45 ... Circuit board, 50 ... Outer container, 51 ... Outer base, 52 ... Outer lid, 53 ... Insulation member , 54 ... lead pin, 60 ... liquid alkali metal atom, 90 ... clock transmission system as a frequency signal generation system, 361 ... first part, 362 ... semiconductor layer, 363 ... second part, LA ... optical axis, LL ... light , M1 ... surface, M2 ... surface, P1 ... first temperature control surface, P2 ... second temperature control surface, S ... internal space, T1 ... first temperature, T2 ... second temperature.

Claims (10)

Light emitting element and
An atomic cell in which an alkali metal atom is housed and light emitted from the light emitting element is incident.
A heater that covers the atomic cell and heats the atomic cell to a first temperature,
The heater includes a first portion heated to the first temperature by the heater and a second portion in contact with the atomic cell and controlled to a second temperature lower than the first temperature by the Perche effect. A temperature control element arranged between the atomic cells and
A light receiving element that detects light transmitted through the atomic cell, and the like.
Atomic oscillator. A constant current source connected to the temperature control element.
The atomic oscillator according to claim 1. The temperature of the surface on which the light of the atomic cell is incident and the temperature of the surface on which the light of the atomic cell is emitted are higher than the second temperature.
The atomic oscillator according to claim 1 or 2. The temperature control element is a Peltier element including a first temperature control surface, a second temperature control surface, and a semiconductor layer connecting the first temperature control surface and the second temperature control surface.
The first portion is the first temperature control surface of the Peltier element.
The second portion is the second temperature control surface of the Peltier element.
From the heater to the atomic cell, the first portion, the semiconductor layer, and the second portion are arranged in this order.
The atomic oscillator according to any one of claims 1 to 3. The temperature control element includes a first metal and a second metal different from the first metal.
The second portion is a joint portion between the first metal and the second metal.
The atomic oscillator according to claim 2 or 3. The first portion is a portion of the first metal in contact with the heater and a portion of the second metal in contact with the heater.
The atomic oscillator according to claim 5. Includes a shield located between the heater and the atomic cell and heated to the first temperature by the heater.
The first portion is a portion of the first metal in contact with the shield.
The atomic oscillator according to claim 5. The temperature control element is a coil that generates a magnetic field.
The atomic oscillator according to claim 5. The first portion of the temperature control element and the constant current source are connected by a third metal.
The atomic oscillator according to any one of claims 5 to 8. Atomic oscillator and
A processing unit for processing a frequency signal from the atomic oscillator is provided.
The atomic oscillator
Light emitting element and
An atomic cell in which an alkali metal atom is housed and light emitted from the light emitting element is incident.
A heater that covers the atomic cell and heats the atomic cell to a first temperature,
The heater includes a first portion heated to the first temperature by the heater and a second portion in contact with the atomic cell and controlled to a second temperature lower than the first temperature by the Perche effect. A temperature control element arranged between the atomic cells and
A light receiving element that detects light transmitted through the atomic cell, and the like.
Frequency signal generation system.

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