Atomic clock structure

Abstract

The purpose of the present invention is to miniaturize an atomic clock structure comprising a gas cell.　This atomic clock structure (100) comprises: a gas cell (GC) comprising a plate-shaped substrate having an internal space filled with gas, the gas cell (GC) also comprising, in a lateral surface located at an end of the substrate in the longitudinal direction (Y-axis direction) thereof, a laser light introduction port optically connected to the internal space; a first holder (HD1) fixed to the side surface of the gas cell (GC); a laser element (3) fixed to an inner surface of the first holder (HD1); and a photodetector (4) disposed at a position where the laser light having passed through the gas cell (GC) is incident.

Description

Atomic clock structure

[0001] The present disclosure relates to structures for atomic clocks.

[0002] Atomic clocks are known as devices for measuring time accurately. There are several types of atomic clocks. In recent years, atomic clocks of a type that irradiates a gas in a gas cell with laser light, such as CPT (Coherent Population Trapping), have been gaining attention. Gas containing an alkali metal such as rubidium (Rb) or cesium (Cs) is sealed in the gas cell. Various types of measurement methods are conceivable. Physical structural components of atomic clocks, i.e., atomic clock structures equipped with a laser element, a photodetector, and a gas cell, are also being studied. Patent Documents 1 to 3 disclose atomic clocks equipped with a gas cell.

[0003] JP 2009-273088 A JP 2019-007763 A JP 2016-171419 A

[0004] Miniaturization of structures for atomic clocks with gas cells is expected.

[0005] The atomic clock structure disclosed herein comprises a plate-shaped substrate having an internal space filled with gas, a gas cell having a laser light inlet optically coupled to the internal space in a side surface located at an end of the longitudinal direction of the substrate, a first holder fixed to the side surface of the gas cell, a laser element fixed to the inner surface of the first holder, and a photodetector positioned at a position where laser light passing through the gas cell is incident.

[0006] FIG. 1 is an exploded perspective view of an atomic clock structure including a gas cell according to a first embodiment. FIG. 2 is a longitudinal sectional view of the gas cell according to the first embodiment. FIG. 3 is a horizontal sectional view of the gas cell according to the first embodiment. FIG. 4 is a diagram showing a longitudinal sectional configuration of an atomic clock structure including a heater. FIG. 5 is a diagram showing a longitudinal sectional configuration of an atomic clock structure including a heater. FIG. 6 is a diagram showing a longitudinal sectional configuration of an atomic clock. FIG. 7 is a block diagram of an atomic clock. FIG. 8 is a longitudinal sectional view of a gas cell according to a second embodiment. FIG. 9 is a longitudinal sectional view of a gas cell according to a third embodiment. FIG. 10 is a longitudinal sectional view of a gas cell according to a fourth embodiment. FIG. 11 is a longitudinal sectional view of a gas cell according to a fifth embodiment. FIG. 12 is a longitudinal sectional view of a gas cell according to a sixth embodiment. FIG. 13 is a longitudinal sectional view of a gas cell according to a seventh embodiment. FIG. 14 is a horizontal sectional view of a gas cell. FIG. 15 is a horizontal sectional view of a gas cell. FIG. 16 is a horizontal sectional view of a gas cell. FIG. 17 is a horizontal sectional view of a gas cell. FIG. 18 is a horizontal sectional view of a gas cell. FIG. 19 is a horizontal cross-sectional view of a gas cell. FIG. 20 is a horizontal cross-sectional view of a gas cell. FIG. 21 is a horizontal cross-sectional view of a gas cell. FIG. 22 is a horizontal cross-sectional view of a gas cell. FIG. 23 is a horizontal cross-sectional view of a gas cell. FIG. 24 is a perspective view of a first holder provided with a laser element. FIG. 25 is a perspective view of an atomic clock structure. FIG. 26 is a diagram showing a longitudinal cross-sectional configuration of an atomic clock structure. FIG. 27(A) is a front view of the atomic clock structure, and FIG. 27(B) is a plan view of the atomic clock structure. FIG. 28(A) is a front view of the atomic clock structure, and FIG. 28(B) is a plan view of the atomic clock structure. FIG. 29(A) is a front view of the atomic clock structure, and FIG. 29(B) is a plan view of the atomic clock structure. FIG. 30(A) is a front view of the atomic clock structure, and FIG. 30(B) is a plan view of the atomic clock structure. Fig. 31(A) is a front view of the atomic clock structure, and Fig. 31(B) is a plan view of the atomic clock structure. Fig. 32(A) is a longitudinal cross-sectional view of the atomic clock structure, and Fig. 32(B) is a plan view of the atomic clock structure. Fig. 33(A) is a plan view of an example structure near the first holder, and Fig. 33(B) is a plan view of another example structure near the first holder. Fig. 34 is a plan view of an example structure near the second holder.Figure 35(A) is a front view of the atomic clock structure, Figure 35(B) is a plan view of the atomic clock structure, and Figure 35(C) is a side view of the atomic clock structure. Figure 36(A) is a front view of the atomic clock structure, Figure 36(B) is a plan view of the atomic clock structure, and Figure 36(C) is a side view of the atomic clock structure. Figure 37(A) is a front view of the atomic clock structure, Figure 37(B) is a plan view of the atomic clock structure, and Figure 37(C) is a side view of the atomic clock structure. Figure 38(A) is a front view of the atomic clock structure, and Figure 38(B) is a plan view of the atomic clock structure.

[0007] The gas cell and atomic clock structure according to the embodiment will be described below. Note that the same elements will be denoted by the same reference numerals, and duplicated explanations will be omitted.

[0008] FIG. 1 is an exploded perspective view of an atomic clock structure including a gas cell according to a first embodiment.

[0009] The atomic clock structure 100 includes a gas cell GC and a laser light inlet W of the gas cell GC. ＩＮ a laser element 3 optically coupled to the gas cell GC, and a laser beam output port W ＯＵＴ and a photodetector 4 optically coupled thereto via a laser diode. The laser element 3 may be a vertical cavity surface emitting laser (VCSEL), and the photodetector 4 may be a photodiode, although other types of elements may also be used.

[0010] The laser element 3 is fixed to a first holder, which will be described later, and the photodetector 4 is fixed to a second holder, which will be described later. That is, the atomic clock structure includes a plate-shaped substrate having an internal space filled with gas, and a laser light inlet W optically coupled to the internal space is provided in a side surface (S1) located at an end in the longitudinal direction of the substrate. ＩＮ a first holder (see FIG. 24) fixed to the side surface (S1) of the gas cell GC; a laser element 3 fixed to the inner surface of the first holder; and a photodetector 4 arranged at a position where laser light passing through the gas cell GC is incident.

[0011] An optical component 5 is interposed between the gas cell GC and the laser element 3. The optical component 5 is one or more optical elements selected from a group of optical elements such as a lens, an optical filter, and a quarter-wave plate. The optical component 5 may include all of a lens, an optical filter, and a quarter-wave plate, and these optical elements may be arranged in order from the laser element 3 side toward the gas cell GC.

[0012] The gas cell GC includes a plate-shaped substrate having an internal space IS filled with gas. The plate-shaped substrate is formed by combining a substrate 1 and a lid member 2. In the description, an XYZ Cartesian coordinate system is set. The thickness direction of the substrate 1 is the Z axis, the longitudinal direction of the substrate 1 is the Y axis, and the width direction of the substrate 1 is the X axis, and these axes are perpendicular to each other. A laser light introduction port W optically coupled to the internal space IS is provided on a first side surface S1 of the plate-shaped substrate. ＩＮ The laser light L emitted from the laser element 3 is ＩＮ travels in the Y-axis direction and passes through the optical component 5 through the laser light introduction port W ＩＮ The gas cell GC is connected to the laser light inlet W ＩＮ and the internal space IS. ＩＮ is one end face of the optical waveguide 1A. The optical waveguide 1A extends along the Y axis.

[0013] The laser light introduced into the optical waveguide 1A travels in the Y-axis direction within the optical waveguide 1A and is emitted from the other end face of the optical waveguide 1A. The laser light emitted from the optical waveguide 1A is irradiated onto a gas in the internal space IS. This gas contains an alkali metal such as cesium (Cs) or rubidium (Rb). This gas may also contain a rare gas.

[0014] If this gas contains an alkali metal, absorption of the laser light occurs according to its energy level. By controlling the energy level and frequency of the laser light, the absorption rate of the laser light in the gas changes. If the control signal given to the laser element 3 is feedback-controlled so that it matches the specific energy level difference of the alkali atoms that make up the gas, the frequency (clock) of the output signal from the feedback control circuit will be an accurate value.

[0015] The laser light propagates along the Y-axis in the internal space IS and passes through it. The laser light is incident on one end face of the first window member 1B and exits from the other end face (laser light exit port W ＯＵＴ In other words, the gas cell GC has a laser beam output port W optically coupled to the internal space IS on a second side surface S2 opposite to the first side surface S1 of the plate-like substrate. ＯＵＴ The laser beam output port W ＯＵＴ The laser light L emitted from ＯＵＴ is incident on the photodetector 4.

[0016] The gas cell GC is provided with a first auxiliary space 1D and a second auxiliary space 1E that communicate with the internal space IS and allow a portion of the gas source material in the internal space IS to remain. That is, a solid source material containing an alkali metal is placed in advance in the first auxiliary space 1D and the second auxiliary space 1E. During manufacturing, when this solid source material is heated to vaporize it and converted into gas in the internal space, some of the source material (including impurities, etc.) may remain in the first auxiliary space 1D and the second auxiliary space 1E.

[0017] The gas cell GC includes a lid member 2 fixed to the upper surface of a substrate 1. The upper surface of the substrate 1 is parallel to the XY plane. The lid member 2 is used to seal the internal space IS. An adhesive can be interposed between the lid member 2 and the substrate 1. One or both of the materials of the substrate 1 and the lid member 2 can be semiconductors or metals, respectively. One or both of the materials of the substrate 1 and the lid member 2 can also be glass or resin, respectively. If either the material of the substrate 1 or the lid member 2 is a heat-melting material, they can be bonded by applying heat and pressure to their interface. In this example, the material of the substrate 1 is silicon (Si), and the material of the lid member 2 is also silicon (Si).

[0018] FIG. 2 is a vertical cross-sectional view of the gas cell according to the first embodiment.

[0019] An optical waveguide 1A is disposed on the first side surface S1 of the plate-shaped substrate. The optical waveguide 1A can be formed by etching the top surface of the substrate 1 to form a groove, and then filling the groove with a laser light transmitting material. An example of the laser light transmitting material is glass (SiO ２ ) No optical waveguide is formed in the lid member 2. Except for the absence of an optical waveguide, the shape of the lid member 2 is the same as the shape of the substrate 1. In other words, the lid member 2 has a first auxiliary space and a second auxiliary space that are the same in shape as the first auxiliary space 1D and the second auxiliary space 1E shown in FIG.

[0020] The main space of the internal space IS of the gas cell GC is composed of a first recess 1C formed in the substrate 1 and a second recess 2C formed in the lid member 2. The depth direction of the first recess 1C is the negative direction of the Z axis, and the depth direction of the second recess 2C is the positive direction of the Z axis. The first recess 1C is connected to the first auxiliary space 1D via a first source gas inlet 1D1. Similarly, the second recess 2C is connected to the first auxiliary space (not shown) of the lid member 2 via a second source gas inlet 2D1. Similarly, the first recess 1C is connected to the second auxiliary space 1E (see FIG. 1) via a source gas inlet (not shown). Similarly, the second recess 2C is connected to the second auxiliary space (not shown) of the lid member 2 via a source gas inlet (not shown).

[0021] A first window material 1B is embedded in the region on the second side surface S2 side of the first recess 1C. Similarly, a second window material 2B is embedded in the region on the second side surface S2 side of the second recess 2C. These window materials can be formed by embedding a laser light transmitting material in the region on the second side surface side after forming each recess. An example of the laser light transmitting material is glass (SiO ２ This may be formed by preparing a block of window material in a separate process and fixing the block within the region on the second side surface of the recess.

[0022] The dimension L1 in the thickness direction (Z-axis direction) of the internal space IS of the gas cell GC is set to be small. In a plane (XY plane) perpendicular to this thickness direction (Z-axis direction), the optical path length L2 of the laser light traveling along the Y-axis within the internal space IS is greater than the dimension L1. In other words, the relationship of dimension L1 < optical path length L2 is satisfied. In this example, the optical path length L2 within the internal space IS is also the dimension of the internal space IS in the Y-axis direction.

[0023] It is also possible to use a structure in which the laser light is reflected so that it travels back and forth inside the internal space IS along the Y-axis direction. In this structure, the relationship L1 < L2 is also satisfied. To allow the laser light to travel back and forth, the angles of the wall surfaces at both ends of the Y-axis direction that define the internal space IS may be slightly inclined from the XZ plane, and a reflective film may be provided on these wall surfaces.

[0024] The dimension L1 satisfies 0.1 μm≦L1≦1000 μm. If L1 is smaller than the lower limit, it becomes practically difficult to introduce laser light. If L1 exceeds the upper limit, the gas cell cannot be sufficiently miniaturized. More preferably, the dimension L1 satisfies 1 μm≦L1≦500 μm. This gas cell GC is thinner than existing structures, and therefore can be installed in small devices such as mobile phones.

[0025] The optical path length L2 (dimension) can be set, for example, to 100 μm≦L2≦5000 μm. If L2 is smaller than the lower limit, the amount of gas for the atomic clock will be insufficient. If L2 exceeds the upper limit, the gas cell cannot be made sufficiently small.

[0026] 3 is a horizontal cross-sectional view of the gas cell according to the first embodiment, which is an XY cross-sectional view taken along the line III-III shown in FIG.

[0027] As shown in the figure, the first auxiliary space 1D and the second auxiliary space 1E are also located in the horizontal cross section of the substrate 1 where the internal space IS exists. Since the first auxiliary space 1D and the second auxiliary space 1E are formed from recesses, these recesses can be formed simultaneously when the first recess 1C is formed. The recesses can be formed by etching or the like.

[0028] The horizontal cross-sectional shape of the optical waveguide 1A is rectangular. The optical waveguide 1A extends along the Y-axis direction. The XZ cross-sectional shape of the optical waveguide 1A is also rectangular, but it can also be trapezoidal or triangular. A rectangle is an easy shape to process and can also sufficiently transmit laser light.

[0029] The horizontal cross-sectional shape of the internal space IS includes a trapezoid. The second width X2 of the internal space IS on the photodetector side is wider than the first width X1 on the laser element side. Even if the laser light widens as it approaches the photodetector, it can still be detected sufficiently.

[0030] In the horizontal cross section, the first and second source gas inlets 1D1 and 1E1 communicate with the hypotenuse of the trapezoidal internal space IS, respectively communicating with the first auxiliary space 1D and the second auxiliary space 1E. In the horizontal cross section, the first auxiliary space 1D is rectangular, and the first center line DX1 of the path from the first source gas inlet 1D1 to the first source gas inlet 1D1 is oriented toward the XZ plane including the end face on the exit side of the gas cell. Similarly, in the horizontal cross section, the second auxiliary space 1E is rectangular, and the second center line EX1 of the path from the second auxiliary space 1E to the second source gas inlet 1E1 is oriented toward the XZ plane including the end face on the exit side of the gas cell. The window material can also be arranged so that it is not located on the extension of these center lines. The shape of the gas introduction path can also prevent adhesion of source material to the optical waveguide and window material when introducing gas into the internal space. The shape of each auxiliary space can also be circular, elliptical, or other shapes other than rectangular.

[0031] FIG. 4 is a diagram showing a vertical cross-sectional configuration of an atomic clock structure equipped with a heater.

[0032] In the figure, the laser element 3, photodetector 4, optical components 5, and gas cell GC are shown with gaps between them to clearly explain the structure. These elements can also be placed in close contact, if necessary. The atomic clock structure 100 includes a second heater H2 attached to the upper lid member 2 that constitutes a plate-shaped substrate. The atomic clock structure 100 also includes a coil CL that surrounds the plate-shaped substrate (substrate 1 and lid member 2) along the Y-axis direction. The coil CL applies a static magnetic field to the inside of the gas cell, suppressing the influence of external magnetic fields such as geomagnetism. Heating by the second heater H2 can vaporize the raw material. Additionally, the second heater H2 can be used to control the gas pressure in the internal space IS, if necessary, or to control the temperature of the laser element 3 located nearby.

[0033] FIG. 5 is a diagram showing a vertical cross-sectional configuration of an atomic clock structure equipped with a heater.

[0034] This atomic clock structure 100 has a structure in which a first heater H1 is further attached to the lower surface of the substrate 1 in the atomic clock structure 100 shown in Fig. 4. The first heater H1 can function in the same way as the second heater H2.

[0035] FIG. 6 is a diagram showing the vertical cross-sectional structure of an atomic clock.

[0036] The atomic clock 200 includes a wiring substrate 10, an atomic clock structure 100 mounted on the wiring substrate 10, and a control circuit 20 mounted on the wiring substrate 10. The control circuit 20 processes electrical signals in the atomic clock structure 100 and outputs a clock signal. The control circuit 20 can supply a drive signal to the laser element 3, receive a signal from the photodetector 4, generate a feedback signal from the received signal, and generate a drive signal for the laser element 3 from the feedback signal. The control circuit 20 can also control the power supplied to the first heater H1 and the second heater H2 based on the feedback signal or independently of the feedback signal.

[0037] FIG. 7 is a block diagram of an atomic clock.

[0038] The control circuit 20 includes a drive circuit 20A that generates a drive signal (drive current) and a feedback control circuit 20B that receives the output signal of the photodetector 4 and performs feedback control of the drive signal. In a laser light irradiation type atomic clock, a laser light is irradiated onto a gas cell and output light from the gas cell is detected. The output light intensity changes due to the energy level transition of the gas. In an atomic clock, the output signal of the photodetector 4 is feedback controlled to generate a drive signal of a specific frequency so as to obtain the desired output light intensity that correlates with the energy level difference in the alkali atoms, and this frequency is used to measure time. The number of pulses contained in the signal of this frequency is counted to generate a clock signal S ＯＵＴ You can also output the following.

[0039] The feedback control circuit 20B detects the level of the low-frequency component of the photodetector 4 and adjusts the frequency and amplitude of the drive signal output from the drive circuit 20A so that the detection level meets the target conditions. For example, the feedback control circuit 20B may include a synchronous detection circuit to which the output signal of the photodetector 4 is input, a loop filter to which an error signal from the synchronous detection circuit is input, a local oscillator to which a control signal output from the loop filter is input, and a high-frequency synthesizer to which the output of the local oscillator is input. The drive signal output from the high-frequency synthesizer is input to the drive circuit 20A. The feedback control circuit 20B can also obtain an accurate frequency by utilizing the phenomenon of coherent population trapping (CPT). In this case, the drive signal modulates the output frequency of the laser element, generating laser light with two sideband frequencies. When the difference frequency between these sideband frequencies matches a transition frequency corresponding to a specific energy level difference of an alkali atom, CPT resonance occurs. During CPT resonance, the intensity of the transmitted light increases, so by monitoring the level of the low frequency component of the photodetector 4, it is possible to obtain the frequency corresponding to the specific energy level difference of the atom.

[0040] It is also possible to change the wavelength of the laser light output from the laser element 3. The wavelength of the laser light can also be controlled by the temperature generated by the laser element 3 by the drive signal itself, the temperature of the laser element 3 controlled by the power supplied to the heater, or the pressure applied to the laser element 3 when a piezoelectric element is attached to the laser element 3. Such control can be performed as necessary. Many types of control methods are known for atomic clocks, so an appropriate one can be adopted.

[0041] FIG. 8 is a vertical cross-sectional view of a gas cell according to the second embodiment.

[0042] This gas cell GC is obtained by integrating the first window material 1B and the second window material 2B in the gas cell shown in Fig. 2, and this integration forms the first window material 1B. This gas cell has the advantage of increasing light transmittance because there are no seams between the window materials.

[0043] FIG. 9 is a vertical cross-sectional view of a gas cell according to the third embodiment.

[0044] This gas cell GC is obtained by removing the first window material 1B from the gas cell shown in Fig. 8 from the recess and attaching it as a third window material GCB to the side surfaces of the substrate 1 and the lid material 2 on the light-emitting surface side. This gas cell has the advantage of being easier to manufacture than the structure shown in Fig. 8.

[0045] FIG. 10 is a vertical cross-sectional view of a gas cell according to the fourth embodiment.

[0046] This gas cell GC is obtained by changing the lid member 2 of the gas cell shown in Fig. 9 to a simple plate. That is, the lower surface of the lid member 2 is flat. This has the advantage that the lid member 2 does not need to be processed.

[0047] FIG. 11 is a vertical cross-sectional view of a gas cell according to the fifth embodiment.

[0048] This gas cell GC is the gas cell shown in Fig. 10 with a thinner lid member 2. That is, the thickness of the lid member 2 is smaller than the thickness of the substrate 1. This structure has the advantage of enabling further miniaturization of the gas cell.

[0049] FIG. 12 is a vertical cross-sectional view of a gas cell according to the sixth embodiment.

[0050] In this gas cell GC, the depth of the first recess 1C in the substrate 1 shown in FIG. 11 is the same as the depth of the optical waveguide 1A, and the thickness of the substrate 1 is reduced. This structure has the advantage of further miniaturizing the gas cell. It is also possible to omit the formation of the first recess 1C and instead place a frame-shaped plate material of the same thickness as the optical waveguide 1A between the substrate 1 and the lid material 2. If a deeper recess is required, a structure can be adopted in which a frame-shaped plate material is placed on the substrate 1, an optical waveguide and a window material are placed on top of that, a frame-shaped plate material is further stacked on top of that, and the lid material 2 is placed on top of that. In this structure, resin, glass, or the like may be interposed between the plates as needed.

[0051] FIG. 13 is a vertical cross-sectional view of a gas cell according to the seventh embodiment.

[0052] This gas cell GC is formed by attaching a lid member 2 to the upper surface of a substrate 1 having a first recess 1C. The substrate 1 and the lid member 2 are made of a laser light transmitting material (SiO ２ ) In order to suppress light from outside, the periphery of the gas cell can be covered with a light-shielding material. It is also possible to include a light-shielding material such as carbon in the region of the laser light-transmitting material that does not transmit the laser light.

[0053] FIG. 14 is a horizontal cross-sectional view of the gas cell.

[0054] In this gas cell, the horizontal cross-sectional shape of the internal space IS in the gas cell shown in Fig. 3 is modified from a trapezoid to a rectangle. That is, the width of the internal space IS in the X-axis direction is constant (second width X2). This structure can increase the gas capacity in the horizontal plane more than the structure shown in Fig. 3.

[0055] FIG. 15 is a horizontal cross-sectional view of the gas cell.

[0056] This gas cell is an example of the gas cell shown in Figure 14, in which the position of the first auxiliary space 1D is set within the wall surface on the laser light incident surface side of the substrate 1. The first auxiliary space 1D is adjacent to the optical waveguide 1A. The first auxiliary space 1D is in communication with the inside of the first recess 1C via a first source gas inlet 1D1. As in the above example, an auxiliary space and a source gas inlet communicating with it may be provided in a position within the lid member opposite the first auxiliary space 1D and the first source gas inlet 1D1. With this structure, the thickness of the wall located outside the second width X2 of the internal space IS can be made thinner, enabling further miniaturization.

[0057] FIG. 16 is a horizontal cross-sectional view of the gas cell.

[0058] This gas cell is an example of the gas cell shown in Figure 15, in which the second auxiliary space 1E is set within the wall surface on the laser light incident surface side of the substrate 1. The second auxiliary space 1E is adjacent to the optical waveguide 1A. The second auxiliary space 1E is connected to the inside of the first recess 1C via the second source gas inlet 1E1. As in the above example, an auxiliary space and a source gas inlet communicating with it may be provided in a position within the lid member opposite the second auxiliary space 1E and the second source gas inlet 1E1. With this structure, the gas cell has multiple auxiliary spaces, so the volume of each auxiliary space can be reduced, and the thickness of the wall surface on the light incident surface side can also be reduced, allowing for further miniaturization.

[0059] FIG. 17 is a horizontal cross-sectional view of the gas cell.

[0060] This gas cell is similar to the gas cell shown in FIG. 15 except that the number of first auxiliary spaces 1D is increased, and each first auxiliary space 1D is connected to the inside of the first recess 1C via a first source gas inlet 1D1. The positions of these first auxiliary spaces 1D do not have to be on the same horizontal plane, and they may be distributed along the thickness direction. As in the above example, auxiliary spaces and source gas inlets connected thereto may be provided in positions within the lid opposite the first auxiliary spaces 1D and the first source gas inlet 1D1. With this structure, the gas cell has multiple distributed auxiliary spaces, which can increase the uniformity of the source gas flow during gas introduction.

[0061] FIG. 18 is a horizontal cross-sectional view of the gas cell.

[0062] This gas cell is an example in which the positions of the first auxiliary space 1D and the second auxiliary space 1E in the gas cell shown in FIG. 16 have been moved to within the wall surface on the laser light emission surface side of the substrate 1. The first auxiliary space 1D is in communication with the first recess 1C via a first source gas inlet 1D1. The second auxiliary space 1E is in communication with the first recess 1C via a second source gas inlet 1E1. As in the above example, an auxiliary space and a source gas inlet communicating therewith may be provided in a position within the lid member opposite the auxiliary space and source gas inlet formed in the substrate 1. This gas cell can achieve the same effects as the gas cell shown in FIG. 16. The horizontal shape of the auxiliary space is not limited to a circle and can be various shapes such as an ellipse.

[0063] FIG. 19 is a horizontal cross-sectional view of the gas cell.

[0064] Although the auxiliary space is not shown in the figure, the auxiliary space described above can be used. The gas cell of this example is an example in which the second width X2 of the internal space IS is set small in the gas cell of Figure 14. The auxiliary space can also be provided in the wall surfaces located at both ends in the width direction. In this case, the gas cell can be made smaller.

[0065] FIG. 20 is a horizontal cross-sectional view of the gas cell.

[0066] Although the auxiliary space is not shown in the figure, an auxiliary space such as that described above can be employed. The gas cell of this example is an example in which the longitudinal direction of the optical waveguide 1A is tilted with respect to the Y-axis in the gas cell of FIG. 15 . The second width X2 of the first window member 1B on the laser light emission side can be set to the second width X2 of the internal space IS. In this gas cell, the optical path length L2 of the laser light traveling within the internal space IS can be set to be longer than the dimension of the internal space IS in the Y-axis direction. The laser light within the internal space IS can be configured to be reflected by the inner wall surface of the substrate 1. A reflective film may be provided on this inner wall surface. In this case, the gas cell can be made smaller.

[0067] FIG. 21 is a horizontal cross-sectional view of the gas cell.

[0068] Although the auxiliary space is not shown in the figure, an auxiliary space such as that described above can be employed. The gas cell of this example is an example in which, in the gas cell of Figure 20, multiple optical waveguides 1A are provided in the wall surface on the laser light incident surface side, and the longitudinal direction of each optical waveguide 1A is parallel to the Y axis. This structure, which includes multiple optical waveguides 1A, can increase the amount of incident laser light.

[0069] FIG. 22 is a horizontal cross-sectional view of the gas cell.

[0070] Although the auxiliary space is not shown in the figure, the auxiliary space described above can be used. The gas cell of this example is an example in which the position of the internal space IS is asymmetric with respect to the X-axis position of the optical waveguide 1A in the gas cell of Figure 15. This structure also makes it possible to reduce the size of the gas cell.

[0071] FIG. 23 is a horizontal cross-sectional view of the gas cell.

[0072] Although the auxiliary space is not shown in the figure, an auxiliary space such as that described above can be employed. The gas cell of this example is an example in which the position of the first window material 1B in the gas cell shown in FIG. 15 has been moved to within the wall surface on the laser light incident surface side. If necessary, a reflective film M1 may be provided on the inner wall surface located at the end of the internal space IS in the Y-axis direction. Examples of materials for the reflective film M1 include metals such as aluminum. Laser light introduced from the optical waveguide 1A into the internal space IS is reflected by the reflective film M1, output to the outside through the first window material 1B, and introduced to the photodetector. Since the optical path length L2 of the laser light within the internal space IS is lengthened by reflection, the dimension of the gas cell in the Y-axis direction is reduced. In this structure, the laser element and the photodetector are arranged adjacent to each other along the X-axis direction.

[0073] As described above, the auxiliary space that serves as the supply source of the gas raw material can have various positions, shapes, dimensions, and quantities as long as it is in communication with the internal space, and is not limited to the above examples. In any case, the gas generated by decomposition of the raw material in the auxiliary space is supplied to the internal space. Note that, although it is preferable that the substrate has an optical waveguide, a structure in which laser light is introduced using a simple through-hole without an optical waveguide is also possible.

[0074] The atomic clock structure 100 described above includes a plate-shaped substrate 1 having an internal space filled with gas, and a laser light inlet W optically coupled to the internal space IS in a side surface located at an end in the longitudinal direction (e.g., Y-axis direction) of the substrate 1. ＩＮ The laser light that has passed through the gas cell GC is incident on a photodetector 4. A laser element 3 fixed on a holder is optically coupled to the gas cell GC.

[0075] Next, the holder will be described.

[0076] FIG. 24 is a perspective view of the first holder on which the laser element is provided.

[0077] A connection surface S10 located at the end of the first holder HD1 in the Y-axis direction is fixed to the side surface (XZ plane) of the gas cell GC. The first holder HD1 has an inner surface S11 to which the laser element 3 is fixed via a submount 31 (subcarrier). The laser element 3 in this example is fixed on the submount 31. The submount 31 is fixed to the inner surface S11. An adhesive can be used to fix each element.

[0078] The first holder HD1 includes a first spacer portion SP1 that defines the distance between the inner surface S11 and the connection surface S10. The inner surface S11 is the inner surface of the first main body portion B1. The pair of first spacer portions SP1 each extend from the position of the inner surface S11 in a direction toward the connection surface S10. The submount 31 is located between the pair of first spacer portions SP1. One or more first leg portions LG1 are integrally provided on the lower side (-Z direction side) of the first main body portion B1. The lower end surfaces of the first leg portions LG1 are fixed to the lower substrate (e.g., a heat sink).

[0079] A plurality of wiring patterns are formed on the inner surface S11 of the first body portion B1, and the laser element 3 is electrically connected to the wiring patterns. The first wiring patterns 32A formed on the inner surface S11 are connected to the first bonding wires W. ３１１ The laser element 3 is electrically connected to a wiring pattern 311 on the submount 31 via a conductive adhesive 31B made of silver paste (a mixture of silver powder and epoxy resin) or the like between the wiring pattern 311 and the lower surface of the laser element 3. The lower surface of the laser element 3 is connected to a first potential. The upper surface of the laser element 3 is connected to a second potential. A drive current is supplied to the laser element 3 in accordance with the potential difference between the first and second potentials. For example, the first potential is electrically connected to the cathode of the laser diode, and the second potential is electrically connected to the anode of the laser diode.

[0080] The upper surface of the laser element 3 is connected to the second bonding wire W. ３１２ The wiring pattern 312 is electrically connected to the wiring pattern 312 on the submount 31 via the third bonding wire W. ３１３ The second wiring pattern 33A is formed on the inner surface S11 of the submount 31.

[0081] The first wiring pattern 32A is electrically connected to a first electrode pad 32B formed on the upper surface S12 of the first body portion B1, and the second wiring pattern 33A is electrically connected to a second electrode pad 33B formed on the upper surface S12 of the first body portion B1.

[0082] When the first holder HD1 is attached to the gas cell, the space inside the holder defined by the first spacer part SP1 forms openings that are open on both ends in the Z-axis direction. Of these openings, the first opening OP1 located on the underside opens toward the heat sink to which the first leg part LG1 is attached, and allows heat generated in the laser element 3 to escape to the heat sink side.

[0083] FIG. 25 is a perspective view of an atomic clock structure.

[0084] A first holder HD1 is fixed to one end of the gas cell GC in the longitudinal direction (light transmission direction: Y-axis), and a second holder HD2 is fixed to the other end. The atomic clock structure 100 includes a heat sink 11 having a surface to which the lower surfaces of the first holder HD1 and the second holder HD2 are fixed. The heat sink 11 can include a metal material (e.g., Cu) that has high heat dissipation properties.

[0085] The first holder HD1 has one or more first legs LG1 positioned between it and the heat sink 11, and the first legs LG1 form a gap between the heat sink 11 and the gas cell GC. The second holder HD2 has one or more second legs LG2 positioned between it and the heat sink 11, and the second legs LG2 form a gap between the heat sink 11 and the gas cell GC. A first heater H1 can be placed in this gap, if necessary.

[0086] The first heater H1 is connected to one or more bonding wires W ３１６ The connection terminals 35 are formed on the first holder HD1, and can be electrically connected to terminals 35C on the wiring board 10 via bonding wires.

[0087] The first electrode pad 32B formed on the first holder HD1 is connected to the fourth bonding wire W ３１４ The second electrode pad 33B formed on the first holder HD1 is electrically connected to the first terminal 32C on the wiring board 10 via the fifth bonding wire W. ３１５ , and is electrically connected to the second terminal 33C on the wiring board 10 via the

[0088] The atomic clock structure 100 includes a resin layer 61 interposed between the first holder HD1 and the gas cell GC. The resin layer 61 (adhesive layer) is interposed between the first spacer portion SP1 (connection surface S10 in FIG. 24 ) of the first holder HD1 and the side surface of the gas cell GC. The resin layer 61 contains a thermosetting resin such as epoxy resin.

[0089] The second holder HD2 has the same shape as the first holder HD1. The second holder HD2 includes a pair of second spacer portions SP2 extending from the ends of the second main body portion B2 in the X-axis direction toward the gas cell GC. A second resin layer 62 (adhesive layer) is interposed between the second spacer portions SP2 and the side surfaces of the gas cell GC. The second resin layer 62 includes a thermosetting resin such as epoxy resin.

[0090] One or more photodetectors 4 are fixed on the inner surface S21 of the second holder HD2. The photodetector 4 may be, for example, a photodiode, and may have a first electrode on its lower surface and a second electrode on its upper surface. For example, a reverse bias voltage is applied to the photodiode. The first electrode is electrically connected to the anode of the photodiode. The second electrode is electrically connected to the anode of the photodiode. This second electrode may be provided on the upper surface of the photodiode.

[0091] The first electrode on the lower surface of the photodetector 4 is connected to a wiring pattern 43A formed on the inner surface S21 of the second holder HD2. The second electrode on the upper surface of the photodetector 4 is connected to a bonding wire W ４１３ , and is connected to the wiring pattern 42A formed on the inner surface S21 of the second holder HD2.

[0092] The wiring pattern 42A is connected to an electrode pad 42B formed on the upper surface S22 of the second holder HD2, and a bonding wire W ４１４ 42C on the wiring board 10 via the terminal 42C.

[0093] The wiring pattern 43A is connected to an electrode pad 43B formed on the upper surface S22 of the second holder HD2, and a bonding wire W ４１５ , and is electrically connected to a terminal 43C on the wiring board 10 via the terminal 43C.

[0094] The first holder HD1 and the second holder HD2 preferably have high electrical resistivity and high thermal conductivity. That is, these holders preferably have an electrical resistivity of 15 μΩcm or more and a thermal conductivity of 20 W / mK or more. Examples of materials that satisfy these conditions include silicon nitride, alumina, silicon, and silicon carbide. This allows electrode pads and wiring patterns to be formed on the holders, and heat from the holders can be transferred to the heat sink 11. That is, wiring patterns (32A, 33A, 32B, 33B (see FIG. 24)) are provided on the first holder HD1, and these wiring patterns are electrically connected to the laser element 3 via bonding wires.

[0095] It is preferable that the first holder HD1 has a thermal conductivity of at least 5 W / mK or more. If the material satisfies this condition, heat can be dissipated efficiently. As a material that satisfies this condition, the first holder HD1 and the second holder HD2 can contain ceramic. As this ceramic or high resistance material (insulating material), aluminum nitride (AlN), silicon carbide (SiC), alumina (Al ２ O ３ ), silicon nitride (Si ３ N ４ The material may include at least one material selected from the group consisting of:

[0096] FIG. 26 is a diagram showing a longitudinal cross-sectional configuration of an atomic clock structure.

[0097] The gas cell GC including the above-described wiring substrate 10 is housed in a case 101 (package). The case 101 can be made of metal or an insulating material and can include a first external terminal E1 and a second external terminal E2 for receiving and transmitting electrical signals from the internal elements, as needed. The first external terminals E1 are plural and can be used to supply current to the laser element 3. The second external terminals E2 are plural and can output signals received from the photodetector 4. The case 101 can include external terminals for supplying power to a heater or a coil (magnet), as needed. The pressure in the internal space VM of the case 101 can be set to a vacuum.

[0098] The above-described atomic clock structure can be modified in many ways.

[0099] FIG. 27(A) is a front view of the atomic clock structure, and FIG. 27(B) is a plan view of the atomic clock structure.

[0100] The atomic clock structure 100 of this example differs from the atomic clock structure 100 shown in Figure 25 in that the first holder HD1 also has one or more legs LG11 on the upper part, and the second holder HD2 also has one or more legs LG21 on the upper part. The rest of the structure is the same as the example in Figure 25. The upper leg can also function as a spacer for a member located above the gas cell GC. The rest of the configuration is the same as the structure shown in Figure 25.

[0101] The first holder HD1 has a first opening OP1 that opens to the heat sink 11 side, but also has an opening that opens upward. The second holder HD2 has a second opening OP2 that opens to the heat sink 11 side, but also has an opening that opens upward. These heat dissipation and opening structures are used in the holders in Figures 24 to 34.

[0102] FIG. 28(A) is a front view of the atomic clock structure, and FIG. 28(B) is a plan view of the atomic clock structure.

[0103] The atomic clock structure 100 of this example differs from the atomic clock structure 100 shown in FIG. 27 in that the legs of the first holder HD1 are eliminated, the lower surface of the first spacer portion SP1 extends to the upper surface of the heat sink 11, and the legs of the second holder HD2 are eliminated, and the lower surface of the second spacer portion SP2 extends to the upper surface of the heat sink 11. The upper legs shown in FIG. 27 are also eliminated, and the positions of the upper surfaces of the first spacer portion SP1 and the second spacer portion SP2 extend upward. The rest of the structure is the same as the example of FIG. 27. There may or may not be a gap between adjacent legs in the X-axis direction shown in FIG. 27. This structure has the advantage of reducing processing costs because the structure of the spacer portion is simplified.

[0104] FIG. 29(A) is a front view of the atomic clock structure, and FIG. 29(B) is a plan view of the atomic clock structure.

[0105] The atomic clock structure 100 of this example differs from the atomic clock structure 100 shown in FIG. 25 in that the legs are removed and the heat sink 11 instead has a recess 11D. The rest of the structure is the same as the example of FIG. 25 . The heat sink 11 has a first protrusion PJ1 and a second protrusion PJ2 located at positions separated along the Y-axis direction, with a recess 11D between them. The number of protrusions may be two or more. In the atomic clock structure 100 of this example, the heat sink 11 has one or more first protrusions PJ1 located between the first holder HD1. The heat sink 11 has one or more second protrusions PJ2 located between the second holder HD2. These protrusions form a gap (one or more recesses) between the heat sink 11 and the gas cell GC. Without forming legs on the holder, a space is secured in which a heater or the like can be placed, and the gas cell GC can be suspended above the heat sink 11.

[0106] FIG. 30(A) is a front view of the atomic clock structure, and FIG. 30(B) is a plan view of the atomic clock structure.

[0107] The atomic clock structure 100 of this example differs from the atomic clock structure 100 shown in Fig. 25 in that an opening 39 is formed in the first spacer portion SP1 and an opening 49 is formed in the second spacer portion SP2. The other structures are the same as those in the example of Fig. 25. The openings 39 and 49 make it possible to improve heat dissipation characteristics.

[0108] FIG. 31(A) is a front view of the atomic clock structure, and FIG. 31(B) is a plan view of the atomic clock structure.

[0109] The atomic clock structure 100 of this example differs from the atomic clock structure 100 shown in Fig. 27 in that a second heat sink 11U is arranged on the upper legs LG11 and LG21. The second heat sink 11U can have a pair of cutout portions at both ends on the Y axis for arranging the above-mentioned bonding wires, and the upper surfaces of the first body portion B1 (and second body portion B2) can be viewed through the openings of the cutout portions.

[0110] Fig. 32(A) is a longitudinal cross-sectional view of the atomic clock structure, and Fig. 32(B) is a plan view of the atomic clock structure. Fig. 32(A) is a YZ cross-section passing through the center position in the X-axis direction of the atomic clock structure shown in Fig. 32(B), and the gas cell GC, heater H1, coil (or thin-film magnet) CL, laser element 3, submount 31, and photodetector 4 are shown without being cross-sectional.

[0111] The atomic clock structure 100 of this example includes a case for accommodating a gas cell, and this case includes an upper substrate 101U, a lower substrate 101L, and a rectangular, annular frame 101C. The frame 101C is disposed between the upper substrate 101U and the lower substrate 101L. The upper surface of the frame 101C is fixed to the lower surface of the upper substrate 101U, and the lower surface of the frame 101C is fixed to the upper surface of the lower substrate 101L. The pressure in the internal space VM inside the opening of the frame 101C can be set to a vacuum.

[0112] The lower substrate 101L has a protrusion 101D that protrudes toward the space within the opening of the frame 101C. A heater H1 is disposed and fixed on the top surface of the protrusion 101D of the lower substrate 101L. One terminal of the heater H1 is connected to an internal wiring E11 that passes through the lower substrate 101L, and the other terminal is connected to an internal wiring (not shown). The heater H1 can be heated by supplying a current between the internal wirings.

[0113] The upper substrate 101U has a protrusion 101D that protrudes toward the space within the opening of the frame 101C. A coil (or permanent magnet (thin-film magnet)) CL is disposed and fixed on the top surface of the protrusion 101D of the upper substrate 101U. When the coil CL is disposed, one terminal of the coil CL is connected to internal wiring E12 that passes through the upper substrate 101U, and the other terminal is connected to internal wiring (not shown). When the coil CL (inductor) is used to generate a magnetic field, a magnetic field is generated around the coil CL by supplying current between these internal wirings, and the magnetic field can be introduced into the gas cell GC. Note that if the coil CL is a permanent magnet, there is no need to introduce current.

[0114] A heat sink 11 having an opening is provided around the periphery of the convex portion 101D, and a first leg LG1 of the first holder HD1 and a second leg LG2 of the second holder HD2 are fixed to the upper surface of the lower heat sink 11. An upper first leg LG11 of the first holder HD1 and an upper second leg LG21 of the second holder HD2 are fixed to the lower surface of the upper second heat sink 11U.

[0115] A first bonding wire W electrically connected to the cathode of the laser element 3 extends from the submount 31 of the laser element 3. ３１１ extends, and the first bonding wire W ３１１is connected to output terminal 32F. A bonding wire electrically connected to the anode of laser element 3 also extends from submount 31 of laser element 3, and this bonding wire is connected to output terminal 33F. Both output terminal 32F and output terminal 33F are internal wiring that penetrates lower substrate 101L, and these terminals can be electrically connected to a laser element drive circuit provided outside the case.

[0116] A bonding wire W electrically connected to the cathode of the photodetector 4 ４１１ is connected to output terminal 42F. Another bonding wire electrically connected to the anode of photodetector 4 is connected to output terminal 43F. Output terminal 42F and output terminal 43F are both internal wiring that passes through lower substrate 101L, and these terminals can be electrically connected to an optical signal detection circuit provided outside the case.

[0117] FIG. 33A is a plan view of an example of a structure in the vicinity of the first holder, and FIG. 33B is a plan view of another example of a structure in the vicinity of the first holder.

[0118] As shown in Figure 33(A), an optical component 5 can be attached to the light incident surface of the gas cell GC. The optical component 5 includes at least a lens, an optical filter, or a quarter-wave plate. The optical component 5 can be attached to the light incident surface of the gas cell GC using an optical adhesive for optical components. Because the thickness of the optical adhesive is thin, the line at the interface between the optical component 5 and the gas cell GC represents the optical adhesive.

[0119] As shown in Figure 33(B), an optical component 5 can also be attached to the light-emitting surface of the laser element 3. The optical component 5 can be attached to the light-incident surface of the laser element 3 using an optical adhesive for optical components. Because the thickness of the optical adhesive is thin, the line of the interface between the optical component 5 and the laser element 3 represents the optical adhesive.

[0120] Examples of optical adhesives that can be used include acrylic optical adhesives containing acrylate ester-based compounds, epoxy optical adhesives containing epoxy resins, silicone optical adhesives containing silicone polymers, and UV-curable silicone optical adhesives containing silicone and an ultraviolet curing agent.

[0121] FIG. 34 is a plan view of an example of a structure in the vicinity of the second holder.

[0122] A plurality of photodetectors 4 are fixed to the inner surface of the second holder HD2. Each photodetector 4 may be a photodiode. When the second holder HD2 includes a plurality of photodetectors 4, the value of the output signal of one photodetector 4 can be corrected using the values ​​of the other photodetectors 4. When the second holder HD2 includes a plurality of photodetectors 4, if one photodetector 4 fails, the other photodetectors 4 can function as a spare photodetector 4.

[0123] 35(A) is a front view of the atomic clock structure, FIG. 35(B) is a plan view of the atomic clock structure, and FIG. 35(C) is a side view of the atomic clock structure.

[0124] The atomic clock structure 100 includes a gas cell GC into which laser light is incident in the thickness direction of a substrate 50. The gas cell GC includes a through-hole 50H. The through-hole 50H is formed at least in the substrate 50, but may be partially formed in the first transparent substrate 51 and / or the second transparent substrate 52. The through-hole 50H is an internal space IS of the substrate 50, and is filled with a gas containing an alkali metal (e.g., rubidium or cesium). A first transparent substrate 51 is bonded and fixed to the lower surface of the substrate 50. A second transparent substrate 52 is bonded and fixed to the upper surface of the substrate 50. The first transparent substrate 51 closes one open end of the through-hole 50H. The second transparent substrate 52 closes the other open end of the through-hole 50H. The gas cell GC includes a plate-shaped substrate 50 having an internal space IS filled with gas.

[0125] The material of the substrate 50 can be an insulator (glass or resin), a semiconductor (e.g., Si), or a metal (e.g., containing Cu, Al, or Fe). In this example, the material of the substrate 50 is silicon (Si). The first transparent substrate 51 and the second transparent substrate 52 are made of a material that is transparent to the laser light from the laser element 3. One example of a material for the first transparent substrate 51 and the second transparent substrate 52 is glass. An adhesive can be used to fix the elements, but if either the substrate 50 or the transparent substrate is made of a material that melts in response to heat, they can also be bonded by applying heat and pressure to their interface.

[0126] The gas cell GC has a laser light inlet optically coupled to the internal space IS in a first surface SE located at one end of the substrate 50 in the thickness direction (Z-axis direction). This laser light inlet is the opening on the light incident side of the through-hole 50H or the laser light incident surface of the first transparent substrate 51 that closes the through-hole 50H, and this opening end face is located within the first surface SE. The first surface SE includes the interface between the first transparent substrate 51 and the gas cell GC. A first spacer portion SP1 of the first holder HD1 is fixed to the first surface SE of the gas cell GC via a first resin layer 61.

[0127] The gas cell GC has a laser light emission port optically coupled to the internal space IS in a second surface SX located at the other end of the substrate 50 in the thickness direction (Z-axis direction). This laser light emission port is the opening on the light emission side of the through-hole 50H or the laser light emission surface of the second transparent substrate 52 that closes the through-hole 50H, and this opening end face is located within the second surface SX. The second surface SX includes the interface between the second transparent substrate 52 and the gas cell GC. The second spacer portion SP2 of the second holder HD2 is fixed to the second surface SX of the gas cell GC via a second resin layer 62.

[0128] The laser element 3 is fixed to the inner surface of the first holder HD1. The photodetector 4 is disposed at a position where the laser light that has passed through the gas cell GC is incident, and receives the laser light. The laser light emitted from the laser element 3 travels along the Z-axis direction (thickness direction of the substrate 50), transmits through the first transparent substrate 51, passes through the through-hole 50H formed in the substrate 50, transmits through the second transparent substrate 52, and reaches the photodetector 4.

[0129] The shape of the first holder HD1 can be the same as that shown in FIG. 29 , but in this example, the gap defined by the first spacer portion SP1 is smaller than that shown in FIG. 29 . The first spacer portion SP1 can define the distance (including the thickness of the first resin layer 61) between the holder inner surface on which the submount 31 is provided and the first surface SE of the substrate 50 on the laser light incident side. The holder inner surface (XY plane) is the inner surface of the first main body portion B1. Each of the pair of first spacer portions SP1 extends from the holder inner surface (XY plane) toward the substrate 50. The submount 31 is located between the pair of first spacer portions SP1. A heat sink 11 (substrate) is provided on the underside (−Z direction side) of the first main body portion B1. The back surface (XY plane) of the first main body portion B1 of the first holder HD1 is fixed to the surface of the heat sink 11 with an adhesive or the like.

[0130] The shape of the second holder HD2 can be the same as the shape of the first holder HD1. The second spacer portion SP2 of the second holder HD2 can define the distance (including the thickness of the second resin layer 62) between the holder inner surface on which the photodetector 4 is provided and the second surface SX on the laser light emission side of the substrate 50. The holder inner surface (XY plane) is the inner surface of the second main body portion B2. The pair of second spacer portions SP2 each extend from the position of the holder inner surface (XY plane) in a direction toward the substrate 50. The photodetector 4 is located between the pair of second spacer portions SP2.

[0131] The atomic clock structure 100 includes a heat sink 11 to which a first holder HD1 is fixed, and the first holder HD1 includes a first opening OP1 that connects the space in which the laser element 3 is arranged to the outside of the first holder HD1. In other words, no holder material is located on an extension line in the X-axis direction within the first opening OP1. This also improves the lateral heat dissipation effect.

[0132] The second holder HD2 has a second opening OP2 that connects the space in which the photodetector 4 is arranged to the outside of the second holder HD2. In other words, no holder material is located on the extension line of the X-axis direction within the second opening OP2. This also improves the heat dissipation effect on the photodetector 4 side. Of course, this heat is transferred to the heat sink 11 due to the thermal conductivity of the first holder HD1 and the second holder HD2 themselves.

[0133] 36(A) is a front view of the atomic clock structure, FIG. 36(B) is a plan view of the atomic clock structure, and FIG. 36(C) is a side view of the atomic clock structure.

[0134] This atomic clock structure 100 differs from the atomic clock structure 100 shown in FIGS. 35(A) to 35(C) in the direction of the opening of the holder.

[0135] In the first holder HD1, a pair of first spacer portions SP1 extend along the longitudinal direction (Y-axis direction) of the heat sink 11 in a planar view (when the XY plane is viewed from the Z-axis direction), and the space between these first spacer portions SP1 is open in the Y-axis direction, forming a first opening OP1.

[0136] In the second holder HD2, a pair of second spacer portions SP2 extend along the longitudinal direction (Y-axis direction) of the heat sink 11 when viewed in a plane, and the space between these second spacer portions SP2 is open in the Y-axis direction, forming a second opening OP2.

[0137] Other structures in this atomic clock structure 100 are the same as those in the atomic clock structure 100 shown in FIGS. 35(A) to 35(C).

[0138] 37(A) is a front view of the atomic clock structure, FIG. 37(B) is a plan view of the atomic clock structure, and FIG. 37(C) is a side view of the atomic clock structure.

[0139] The atomic clock structure 100 includes a first holder HD1 and a second holder HD2 fixed onto a heat sink 11. The thickness direction of the heat sink 11 is the Z-axis direction, the longitudinal direction is the Y-axis direction, and the width direction is the X-axis direction. In this example, the heat sink 11 has a larger longitudinal dimension than a width dimension in a plan view.

[0140] The first holder HD1 includes a first main body portion B1 and a pair of first spacer portions SP1 extending from the first main body portion B1 toward the substrate 50 (Y-axis direction). The lower surfaces of the first main body portion B1 and the first spacer portions SP1 are fixed to the heat sink 11. A submount 31 and a laser element 3 are disposed in the space between the pair of first spacer portions SP1. The submount 31 is fixed on the inner surface (XZ plane) of the first holder HD1. As in the above example, the laser element 3 is fixed on the submount 31. As a result, the laser element 3 is fixed to the inner surface (XZ plane) of the first holder HD1.

[0141] The second holder HD2 includes a second main body portion B2 and a pair of second spacer portions SP2 extending from the second main body portion B2 toward the substrate 50 (in the -Y-axis direction). The lower surfaces of the second main body portion B2 and the second spacer portions SP2 are fixed to the heat sink 11. The photodetector 4 is disposed in the space between the pair of second spacer portions SP2. The photodetector 4 is fixed on the inner surface (XZ plane) of the second holder HD2.

[0142] The atomic clock structure 100 includes a gas cell GC into which laser light is incident in the thickness direction of a substrate 50. The gas cell GC includes a through-hole 50H. The through-hole 50H is formed at least in the substrate 50, but may be partially formed in the first transparent substrate 51 and / or the second transparent substrate 52. The through-hole 50H is an internal space IS of the substrate 50, and is filled with a gas containing an alkali metal (e.g., rubidium or cesium). A first transparent substrate 51 is bonded and fixed to one side of the substrate 50. A second transparent substrate 52 is bonded and fixed to the other side of the substrate 50. The first transparent substrate 51 closes one open end of the through-hole 50H. The second transparent substrate 52 closes the other open end of the through-hole 50H. The gas cell GC includes a plate-shaped substrate 50 having an internal space IS filled with gas.

[0143] The material of the substrate 50 can be an insulator (glass or resin), a semiconductor (e.g., Si), or a metal (e.g., containing Cu, Al, or Fe). In this example, the material of the substrate 50 is silicon (Si). The first transparent substrate 51 and the second transparent substrate 52 are made of a material that is transparent to the laser light from the laser element 3. One example of a material for the first transparent substrate 51 and the second transparent substrate 52 is glass. An adhesive can be used to fix the elements, but if either the substrate 50 or the transparent substrate is made of a material that melts in response to heat, they can also be bonded by applying heat and pressure to their interface.

[0144] The gas cell GC has a laser light inlet optically coupled to the internal space IS in a first surface SE located at one end of the substrate 50 in the thickness direction (Y-axis direction). This laser light inlet is the opening on the light incident side of the through-hole 50H or the laser light incident surface of the first transparent substrate 51 that closes the through-hole 50H, and this opening end face is located within the first surface SE. The first surface SE includes the interface between the first transparent substrate 51 and the gas cell GC. The first spacer portion SP1 of the first holder HD1 is fixed to the first surface SE of the gas cell GC via a first resin layer 61.

[0145] The gas cell GC has a laser light emission port optically coupled to the internal space IS in a second surface SX located at the other end of the substrate 50 in the thickness direction (Y-axis direction). This laser light emission port is the opening on the light emission side of the through-hole 50H or the laser light emission surface of the second transparent substrate 52 that closes the through-hole 50H, and this opening end face is located within the second surface SX. The second surface SX includes the interface between the second transparent substrate 52 and the gas cell GC. The second spacer portion SP2 of the second holder HD2 is fixed to the second surface SX of the gas cell GC via a second resin layer 62.

[0146] The photodetector 4 is disposed at a position where the laser light that has passed through the gas cell GC is incident. The laser light emitted from the laser element 3 travels along the Y-axis direction (the thickness direction of the substrate 50), passes through the first transparent substrate 51, passes through the through-hole 50H formed in the substrate 50, passes through the second transparent substrate 52, and reaches the photodetector 4.

[0147] The first holder HD1 has a first opening OP1 that connects the space in which the laser element 3 is arranged to the outside of the first holder HD1. No holder material is located on the extension line in the Z-axis direction within the first opening OP1, but the heat sink 11 is located there. This improves the heat dissipation effect of the first holder HD1.

[0148] The second holder HD2 has a second opening OP2 that connects the space in which the photodetector 4 is arranged to the outside of the second holder HD2. No holder material is located on the extension line in the Z-axis direction within the second opening OP2, but the heat sink 11 is located there. This also improves the heat dissipation effect of the second holder HD2.

[0149] FIG. 38(A) is a front view of the atomic clock structure, and FIG. 38(B) is a plan view of the atomic clock structure.

[0150] The gas cell provided with the first and second holders is referred to as a gas cell unit UT. The gas cell unit UT can be fixed to a heat sink 11, and a heater for adjusting the temperature and a coil (or a permanent magnet) for generating a magnetic field inside the gas cell can be arranged around the gas cell unit UT.

[0151] In the atomic clock structure, a third heater H3 and a fourth heater H4 can be arranged at both ends of the gas cell unit UT in the Y-axis direction. A third coil (or permanent magnet) CL3 can be arranged outside the third heater H3. A fourth coil (or permanent magnet) CL4 can be arranged outside the fourth heater H4.

[0152] In the atomic clock structure, a fifth heater H5 and a sixth heater H6 can be arranged at both ends of the gas cell unit UT in the X-axis direction. A fifth coil (or permanent magnet) CL5 can be arranged outside the fifth heater H5. A sixth coil (or permanent magnet) CL6 can be arranged outside the sixth heater H6.

[0153] The seventh heater H7 and the eighth heater H8 can be disposed inside the gas cell unit UT. As described above, heaters and coils (or permanent magnets) can also be disposed at both ends of the gas cell unit UT in the Z-axis direction.

[0154] The arrangement of the heater and coil (permanent magnet) is not limited to the above, and several of the above elements may be selected and arranged around the gas cell unit UT as needed. The heater may be a resistance heating system, but infrared or induction heating may also be used. The heater arrangement is not limited to the above structure. The coil structure may be a solenoid coil, a spiral coil, a planar coil, or the like, and various arrangements may be adopted. The permanent magnet may also be a thin-film magnet. Known types of permanent magnets include alnico magnets (an alloy containing iron, aluminum, nickel, and cobalt), ferrite magnets, neodymium magnets (an alloy containing iron, neodymium, and boron), and samarium-cobalt magnets (an alloy containing samarium and cobalt).

[0155] As described above, the device according to the above embodiment has the following features.

[0156] The atomic clock structure 100 according to the first embodiment includes a plate-shaped substrate 1 having an internal space filled with gas, and a laser light introduction port W optically coupled to the internal space IS in a side surface located at an end in the longitudinal direction (e.g., Y-axis direction) of the substrate 1. ＩＮ a first holder HD1 fixed to the side surface of the gas cell GC; a laser element 3 fixed to the inner surface of the first holder HD1; and a photodetector 4 arranged at a position where laser light that has passed through the gas cell GC is incident.

[0157] The atomic clock structure 100 according to the second embodiment comprises a heat sink 11 to which a first holder HD1 is fixed, and the first holder HD1 has an opening OP1 on the heat sink 11 side.

[0158] In the atomic clock structure 100 according to the third aspect, the first holder HD1 has one or more legs LG1 positioned between it and the heat sink 11, and the legs LG1 form a gap between the heat sink 11 and the gas cell GC.

[0159] In the atomic clock structure 100 according to the fourth aspect, the heat sink 11 has one or more convex portions located between it and the first holder HD1, and the convex portions form a gap between the heat sink and the gas cell.

[0160] In the atomic clock structure 100 according to the fifth aspect, the first holder HD1 has an electrical resistivity of 15 μΩcm or more and a thermal conductivity of 20 W / mK or more.

[0161] The atomic clock structure 100 according to the sixth aspect includes a wiring pattern provided on the first holder HD1, and the wiring pattern is electrically connected to the laser element.

[0162] In the atomic clock structure 100 according to the seventh aspect, the first holder HD1 has a thermal conductivity of 5 W / mK or more.

[0163] In the atomic clock structure 100 according to the eighth aspect, the first holder HD1 includes ceramic.

[0164] In the atomic clock structure 100 according to the ninth aspect, the ceramic contains at least one material selected from the group consisting of aluminum nitride, silicon carbide, alumina, and silicon nitride.

[0165] The atomic clock structure according to the tenth aspect includes a resin layer 61 interposed between the first holder HD1 and the gas cell GC.

[0166] In the atomic clock structure 100 according to the eleventh aspect, the resin layer 61 contains a thermosetting resin.

[0167] The atomic clock structure according to the twelfth aspect comprises a plate-shaped substrate 1 having an internal space IS filled with gas, a gas cell GC having a laser light inlet (Figures 35 to 37) optically coupled to the internal space IS in a surface located at an end in the thickness direction of the substrate 1, a first holder HD1 fixed to the surface of the gas cell GC, a laser element 3 fixed to the inner surface of the first holder HD1, and a photodetector 4 arranged at a position where laser light passing through the gas cell GC is incident.

[0168] The atomic clock structure 100 according to the thirteenth aspect comprises a heat sink 11 to which a first holder HD1 is fixed, and the first holder HD1 comprises an opening OP1 that connects the space in which the laser element 3 is arranged to the outside of the first holder HD1.

[0169] Some of the gas cells GC described above include a plate-shaped substrate 1 having an internal space IS filled with gas, and a laser light inlet optically coupled to the internal space IS on the side of the substrate 1.

[0170] Some of the gas cells GC described above have a laser light emission port optically coupled to the internal space IS on the side surface opposite to the side surface of the substrate 1 .

[0171] In some of the gas cells GC described above, the thickness dimension L1 of the internal space IS and the optical path length L2 of the laser light traveling within the internal space IS in a plane perpendicular to the thickness direction satisfy the relationship L1 < L2.

[0172] In some of the above-mentioned gas cells GC, the dimension L1 satisfies 0.1 μm≦L1≦1000 μm.

[0173] Some of the gas cells GC described above have auxiliary spaces that communicate with the internal space IS and allow a portion of the gas source to remain.

[0174] In some of the gas cells GC described above, an auxiliary space is also located within the horizontal cross section of the substrate 1 where the internal space IS exists.

[0175] In some of the gas cells GC described above, the gas contains an alkali metal.

[0176] Some of the gas cells GC described above include an optical waveguide disposed between the laser light inlet and the internal space IS.

[0177] In some of the above-described gas cells GC, the horizontal cross-sectional shape of the optical waveguide 1A is rectangular.

[0178] In some of the above-described gas cells GC, the horizontal cross-sectional shape of the internal space IS includes a trapezoid.

[0179] In some of the above-described gas cells GC, the horizontal cross-sectional shape of the internal space IS includes a rectangle.

[0180] Some of the gas cells GC described above include a heater attached to the substrate 1 .

[0181] Some of the atomic clock structures described above include any of the gas cells GC described above, a laser element 3 optically coupled to the laser light inlet, and a photodetector 4 optically coupled to the internal space IS.

[0182] As described above, the gas cell and atomic clock structure described above can be miniaturized. If an atomic clock can be miniaturized sufficiently, it can be mounted in a variety of devices. For example, a miniaturized atomic clock can be mounted in a mobile phone, an automobile, a robot, a drone, a global positioning system (GPS), a security system, or the like.

[0183] Although various exemplary embodiments have been described above, various omissions, substitutions, and modifications may be made without being limited to the above-described exemplary embodiments. Furthermore, elements from different embodiments may be combined to form other embodiments. It will be understood from the above description that various embodiments of the present disclosure have been described herein for illustrative purposes, and that various modifications may be made without departing from the scope and spirit of the present disclosure. Accordingly, the various embodiments disclosed herein are not intended to be limiting, with the true scope and spirit being indicated by the appended claims.

[0184] 1, 50...substrate, 11...heat sink, 3...laser element, 4...photodetector, 101D...protrusion, OP1...first opening, OP2...second opening, 61...first resin layer, 62...second resin layer, 100...atomic clock structure, GC...gas cell, HD1...first holder, IS...internal space, L ＩＮ , L ＯＵＴ ...laser light, LG1, LG11, LG21...legs, S11...inner surface, SE, SX...surface, VM...internal space, W ＩＮ ...Laser light inlet.

Claims

1. An atomic clock structure comprising: a gas cell having a plate-shaped substrate with an internal space filled with gas, the gas cell having a laser light inlet optically coupled to the internal space in a side surface located at an end of the longitudinal direction of the substrate; a first holder fixed to the side surface of the gas cell; a laser element fixed to the inner surface of the first holder; and a photodetector arranged at a position where laser light passing through the gas cell is incident.

2. An atomic clock structure as claimed in claim 1, wherein the first holder has a heat sink fixed thereto, and the first holder has an opening between the laser element and the heat sink.

3. The atomic clock structure according to claim 2, wherein the first holder has one or more legs positioned between the first holder and the heat sink, the legs forming a gap between the heat sink and the gas cell.

4. The atomic clock structure according to claim 2, wherein the heat sink has one or more protrusions located between the heat sink and the first holder, and the protrusions form a gap between the heat sink and the gas cell.

5. The atomic clock structure according to claim 1, wherein the first holder has an electrical resistivity of 15 μΩcm or more and a thermal conductivity of 20 W / mK or more.

6. The atomic clock structure according to claim 1, further comprising a wiring pattern provided on said first holder, said wiring pattern being electrically connected to said laser element.

7. The atomic clock structure according to claim 1, wherein the first holder has a thermal conductivity of 5 W / mK or more.

8. The atomic clock structure of claim 1, wherein the first holder comprises a ceramic.

9. The atomic clock structure according to claim 8, wherein the ceramic contains at least one material selected from the group consisting of aluminum nitride, silicon carbide, alumina, and silicon nitride.

10. The atomic clock structure according to claim 1, further comprising a resin layer interposed between the first holder and the gas cell.

11. The atomic clock structure according to claim 10, wherein the resin layer includes a thermosetting resin.

12. An atomic clock structure comprising: a gas cell having a plate-shaped substrate with an internal space filled with gas, the gas cell having a laser light inlet optically coupled to the internal space in a surface located at an end of the substrate in the thickness direction; a first holder fixed to the surface of the gas cell; a laser element fixed to the inner surface of the first holder; and a photodetector arranged at a position where laser light passing through the gas cell is incident.

13. An atomic clock structure as described in claim 11, wherein the first holder has a fixed heat sink, and the first holder has an opening that connects the space in which the laser element is arranged to the outside of the first holder.

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