JP2020181863A - Semiconductor laser and atomic oscillator - Google Patents

Abstract

To provide a semiconductor laser capable of increasing a tensile stress generated in a resonance part regardless of a width of an oxidation region.SOLUTION: A semiconductor laser includes a first mirror layer, a second mirror layer, an active layer, a current constriction layer, a first region, and a second region. The first mirror layer, the second mirror layer, the active layer, the current constriction layer, the first region, and the second region constitute a laminate. The first region and the second region constitute an oxidation region of the laminate. In a plan view, the laminate includes a first portion, a second portion, and a third portion arranged between the first portion and the second portion and resonates light generated in the active layer. In the plan view, the first portion, the second portion, and the third portion are arranged along a first axis passing through the center of the third portion. In the plan view, the oxidation region of the first portion crosses a second axis orthogonal to the first axis at least three times.SELECTED DRAWING: Figure 3

Description

The present invention relates to semiconductor lasers and atomic oscillators.

The surface emitting semiconductor laser is used, for example, as a light source of an atomic oscillator using CPT (Coherent Population Trapping), which is one of the quantum interference effects. Such a semiconductor laser has two mirror layers and an active layer arranged between the two mirror layers. Further, the semiconductor laser has a current constriction layer for preventing the current injected into the active layer from spreading in the plane of the active layer.

As such a semiconductor laser, for example, Patent Document 1 describes an n-type Al _0.12 Ga _0.88 As layer and an n-type Al _0.9 Ga _0.1 As layer on an n-type GaAs substrate. A first mirror layer consisting of 40.5 pairs, an active layer, and a second layer consisting of 20 pairs of a p-type Al _0.12 Ga _0.88 As layer and a p-type Al _0.9 Ga _0.1 As layer. A semiconductor laser having a laminated structure with a mirror is disclosed.

In Patent Document 1, the layer of the second mirror is changed to a layer having a large composition ratio of Al, and the layer is oxidized from the side surface to form a current constriction layer. When the current constriction layer is formed, the Al _0.9 Ga _0.1 As layer constituting the first mirror and the second mirror is also oxidized to form an oxidized region.

Further, in a surface emitting semiconductor laser, since the resonator generally has an isotropic structure, it is difficult to control the polarization direction of the light emitted from the resonator. Therefore, in Patent Document 1, a distortion applying portion that imparts distortion to the resonance portion is provided to polarize the light.

Japanese Unexamined Patent Publication No. 2015-119138

The oxidized region is formed by replacing arsenic in the Al _0.9 Ga _0.1 As layer with oxygen, but the volume is reduced at that time. Therefore, if the width of the oxidation region of the strain applying portion is increased, the tensile stress generated in the resonance portion can be increased.

However, when the width of the oxidized region of the strain applying portion is increased, the width of the oxidized region of the resonance portion is also increased. Therefore, the stress generated in the resonance portion becomes large, and a defect may occur in the resonance portion. If a defect occurs in the resonance portion, the characteristics of the semiconductor laser will change.

The present invention has been made to solve at least a part of the above-mentioned problems, and can be realized as the following aspects or application examples.

The semiconductor laser according to this application example includes a first mirror layer, a second mirror layer, an active layer arranged between the first mirror layer and the second mirror layer, the first mirror layer, and the above. A current constriction layer arranged between the second mirror layer, a first region continuously provided with the first mirror layer and containing a plurality of first oxide layers, and a continuous second mirror layer. The first mirror layer, the second mirror layer, the active layer, the current constriction layer, the first region, and the second region, which are provided and include a second region including a plurality of second oxide layers. Consists of a laminated body, the first region and the second region constitute an oxidized region of the laminated body, and the laminated body has a first portion, a second portion, and the first portion in a plan view. The first portion, the second portion, and the third portion are arranged between the first portion and the second portion and have a third portion that resonates the light generated in the active layer. Arranged along a first axis passing through the center of the third portion in plan view, the oxidized region of the first portion intersects a second axis orthogonal to the first axis at least three times in plan view. To do.

In the semiconductor laser according to the present application example, the first portion has a recess, and the second axis may intersect the oxidation region of the wall portion constituting the recess.

In the semiconductor laser according to the present application example, the length of the recessed space along the first axis may be larger than the length of the recessed space along the second axis.

In the semiconductor laser according to this application example, the depth of the recess and the height of the laminate may be equal.

In the semiconductor laser according to this application example, the depth of the recess may be larger than the height of the laminate.

In the semiconductor laser according to the present application example, the length of the first portion along the second axis may be larger than the length of the third portion along the second axis.

The atomic oscillator according to this application example detects the intensity of the semiconductor laser, the atomic cell containing the alkali metal atom irradiated with the light emitted from the semiconductor laser, and the light transmitted through the atomic cell. The semiconductor laser includes a light receiving element that outputs a detection signal, and the semiconductor laser is an active layer arranged between a first mirror layer, a second mirror layer, and the first mirror layer and the second mirror layer. A current constriction layer arranged between the first mirror layer and the second mirror layer, and a first region continuously provided with the first mirror layer and containing a plurality of first oxide layers. The first mirror layer, the second mirror layer, the active layer, the current constriction layer, and the like, which are provided continuously with the second mirror layer and include a second region including a plurality of second oxide layers. The first region and the second region constitute a laminated body, the first region and the second region constitute an oxidation region of the laminated body, and the laminated body is a first portion in a plan view. And a third portion arranged between the first portion and the second portion and resonating the light generated in the active layer, the first portion and the second portion. The portion and the third portion are arranged along a first axis passing through the center of the third portion in plan view, and the oxidized region of the first portion is orthogonal to the first axis in plan view. Crosses the second axis at least three times.

The plan view which shows typically the semiconductor laser which concerns on 1st Embodiment. The cross-sectional view which shows typically the semiconductor laser which concerns on 1st Embodiment. The plan view which shows typically the semiconductor laser which concerns on 1st Embodiment. The cross-sectional view which shows typically the semiconductor laser which concerns on 1st Embodiment. The cross-sectional view which shows typically the manufacturing process of the semiconductor laser which concerns on 1st Embodiment. The cross-sectional view which shows typically the manufacturing process of the semiconductor laser which concerns on 1st Embodiment. The cross-sectional view which shows typically the manufacturing process of the semiconductor laser which concerns on 1st Embodiment. The plan view which shows typically the semiconductor laser which concerns on a comparative example. The plan view which shows typically the semiconductor laser which concerns on 1st modification of 1st Embodiment. The plan view which shows typically the semiconductor laser which concerns on the 2nd modification of 1st Embodiment. FIG. 5 is a cross-sectional view schematically showing a semiconductor laser according to a third modification of the first embodiment. The plan view which shows typically the semiconductor laser which concerns on 2nd Embodiment. The plan view which shows typically the semiconductor laser which concerns on 1st modification of 2nd Embodiment. The plan view which shows typically the semiconductor laser which concerns on the 2nd modification of 2nd Embodiment. The plan view which shows typically the semiconductor laser which concerns on the 3rd modification of 2nd Embodiment. The plan view which shows typically the semiconductor laser which concerns on 4th modification of 2nd Embodiment. The plan view which shows typically the semiconductor laser which concerns on 3rd Embodiment. The cross-sectional view which shows typically the semiconductor laser which concerns on 3rd Embodiment. The plan view which shows typically the semiconductor laser which concerns on the modification of 3rd Embodiment. The figure which shows the structure of the atomic oscillator which concerns on 4th Embodiment. The figure for demonstrating an example of the frequency signal generation system which concerns on 5th Embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the embodiments described below do not unreasonably limit the contents of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

1. 1. First Embodiment 1.1. Semiconductor Laser First, the semiconductor laser according to the first embodiment will be described with reference to the drawings. FIG. 1 is a plan view schematically showing the semiconductor laser 100 according to the first embodiment. FIG. 2 is a sectional view taken along line II-II of FIG. 1 schematically showing the semiconductor laser 100 according to the first embodiment. FIG. 3 is a plan view schematically showing the semiconductor laser 100 according to the first embodiment. FIG. 4 is a sectional view taken along line IV-IV of FIG. 3 schematically showing the semiconductor laser 100 according to the first embodiment.

For convenience, FIG. 2 shows the laminated body 2 in a simplified manner. Further, in FIG. 3, the members other than the laminated body 2 of the semiconductor laser 100 are not shown. Further, in FIGS. 1 to 4, the X-axis, the Y-axis, and the Z-axis are illustrated as three axes orthogonal to each other. Further, in the present specification, the positional relationship in the semiconductor laser 100 will be described with the second electrode 82 side as the upper side and the substrate 10 side as the lower side.

The semiconductor laser 100 is, for example, a Vertical Cavity Surface Emitting Laser (VCSEL). As shown in FIGS. 1 to 4, the semiconductor laser 100 includes a substrate 10, a first mirror layer 20, an active layer 30, a second mirror layer 40, a current constriction layer 42, a contact layer 50, and a third layer. It includes one region 60, a second region 62, a resin layer 70, a first electrode 80, and a second electrode 82.

The substrate 10 is, for example, a first conductive type GaAs substrate. The first conductive type is, for example, n type.

The first mirror layer 20 is arranged on the substrate 10. The first mirror layer 20 is arranged on the substrate 10 side with respect to the active layer 30. The first mirror layer 20 is arranged between the substrate 10 and the active layer 30. The first mirror layer 20 is, for example, an n-type semiconductor layer. The first mirror layer 20 is a Distributed Bragg Reflector (DBR) mirror. As shown in FIG. 4, the first mirror layer 20 is configured by alternately laminating high refractive index layers 24 and low refractive index layers 26. The high refractive index layer 24 is, for example, an n-type Al _0.12 Ga _0.88 As layer doped with silicon. The low refractive index layer 26 is, for example, an n-type Al _x Ga _1-x As layer doped with silicon when 0.85 ≦ x ≦ 0.90. The number of layers of the high refractive index layer 24 and the low refractive index layer 26 is, for example, 10 pairs or more and 50 pairs or less.

The active layer 30 is arranged on the first mirror layer 20. The active layer 30 is arranged between the first mirror layer 20 and the second mirror layer 40. The active layer 30 is, for example, a multiple quantum well in which three quantum well structures composed of an i-type In _0.06 Ga _0.94 As layer and an i-type Al _0.3 Ga _0.7 As layer are stacked. It has a (MQW: Multi Quantum Well) structure.

The second mirror layer 40 is arranged on the active layer 30. The second mirror layer 40 is arranged opposite to the substrate 10 with respect to the active layer 30. The second mirror layer 40 is arranged between the active layer 30 and the contact layer 50. The second mirror layer 40 is, for example, a second conductive type semiconductor layer. The second conductive type is, for example, a p type. The second mirror layer 40 is a distributed Bragg reflection type mirror. The second mirror layer 40 is configured by alternately laminating high refractive index layers 44 and low refractive index layers 46. The high refractive index layer 44 is, for example, a carbon-doped p-type Al _0.12 Ga _0.88 As layer. The low refractive index layer 46 is, for example, a carbon-doped p-type Al _x Ga _1-x As layer when 0.85 ≦ x ≦ 0.90. The number of layers of the high refractive index layer 44 and the low refractive index layer 46 is, for example, 3 pairs or more and 40 pairs or less.

The second mirror layer 40, the active layer 30, and the first mirror layer 20 form a vertical resonator type pin diode. When a forward voltage of the pin diode is applied between the first electrode 80 and the second electrode 82, recoupling of electrons and holes occurs in the active layer 30, and light emission occurs. The light generated in the active layer 30 is multiplely reflected between the first mirror layer 20 and the second mirror layer 40, and stimulated emission occurs at that time, and the intensity is amplified. Then, when the light gain exceeds the light loss, laser oscillation occurs, and the laser light is emitted from the upper surface of the contact layer 50.

The current constriction layer 42 is arranged between the first mirror layer 20 and the second mirror layer 40. The current constriction layer 42 is arranged between the active layer 30 and the second mirror layer 40. The current constriction layer 42 may be arranged, for example, on the active layer 30 or inside the second mirror layer 40. The current constriction layer 42 is, for example, a layer in which the Al _x Ga _1-x As layer is oxidized when x ≧ 0.95. The current constriction layer 42 is provided with an opening 43 that serves as a current path. The current constriction layer 42 can prevent the current injected into the active layer 30 from spreading in the plane of the active layer 30.

The contact layer 50 is arranged on the second mirror layer 40. The contact layer 50 is a p-type semiconductor layer. Specifically, the contact layer 50 is a carbon-doped p-type GaAs layer.

As shown in FIG. 4, the first region 60 is provided on the side of the first mirror layer 20 constituting the laminated body 2. The first region 60 includes a plurality of first oxide layers 6 provided continuously with the first mirror layer 20. Specifically, the first region 60 comprises a first oxide layer 6 in which a layer continuous with the low refractive index layer 26 constituting the first mirror layer 20 is oxidized, and a first mirror layer 20. The high-refractive index layer 24 and the continuous layer 4 are alternately laminated.

The second region 62 is provided on the side of the second mirror layer 40 constituting the laminated body 2. The second region 62 includes a plurality of second oxide layers 16 provided continuously with the second mirror layer 40. Specifically, the second region 62 comprises a second oxide layer 16 in which a layer continuous with the low refractive index layer 46 constituting the second mirror layer 40 is oxidized, and a second mirror layer 40. The high refractive index layer 44 and the continuous layer 14 are alternately laminated.

The first region 60 and the second region 62 constitute an oxidation region 8. As shown in FIG. 3, the oxidation region 8 is provided along the outer edge of the laminated body 2. As shown in FIG. 4, the upper surface 63 of the oxidation region 8 is inclined with respect to the upper surface 48 of the second mirror layer 40. The width W of the oxidation region 8 is, for example, 0.5 μm or more and 2.0 μm or less. The width W depends on the Al composition ratio of the low refractive index layers 26 and 46, and the larger the Al composition ratio, the larger the width W.

As shown in FIG. 4, the width W of the oxidation region 8 is the end 9a of the lowest layer among the plurality of oxide layers and the end 9b of the uppermost layer of the plurality of oxide layers on the side surface of the laminated body 2. , Is the distance between. The end 9a is the end of the lowermost oxide layer among the plurality of oxide layers, and is the end opposite to the low refractive index layer continuous with the lowermost oxide layer. The end 9a constitutes the side surface of the laminated body 2. The end 9b is the end of the uppermost oxide layer among the plurality of oxide layers, and is the end on the low refractive index layer side continuous with the uppermost oxide layer.

A part of the first mirror layer 20, the active layer 30, the second mirror layer 40, the current constriction layer 42, the contact layer 50, the first region 60, and the second region 62 constitute the laminated body 2. As shown in FIG. 2, the laminated body 2 is columnar. The laminated body 2 is arranged on the first mirror layer 20 and projects upward from the first mirror layer 20. The laminate 2 is surrounded by the resin layer 70.

As shown in FIG. 3, the laminated body 2 has a first portion 2a, a second portion 2b, and a third portion 2c in a plan view. In addition, the plan view means to see along the axis perpendicular to the substrate 10, and in the illustrated example, it means to see along the Z axis. The Z-axis is an axis perpendicular to the substrate 10, and the X-axis and the Y-axis are axes perpendicular to the Z-axis and perpendicular to each other.

The first portion 2a, the second portion 2b, and the third portion 2c are arranged along the first axis A1 in a plan view. The first portion 2a, the second portion 2b, and the third portion 2c are arranged on the first axis A1 in a plan view. The first axis A1 is an axis passing through the center C of the third portion 2c. In the illustrated example, the first axis A1 is parallel to the Y axis.

The first portion 2a, the third portion 2c, and the second portion 2b are arranged in this order along the first axis A1. The first portion 2a projects from the third portion 2c along the first axis A1 to one side. The second portion 2b projects from the third portion 2c along the first axis A1 to the other side. The first portion 2a and the second portion 2b have the same shape in a plan view.

The first portion 2a is connected to the third portion 2c. The second portion 2b is connected to the third portion 2c. That is, the first portion 2a, the second portion 2b, and the third portion 2c are integrally provided. The first portion 2a and the second portion 2b are point-symmetric with respect to the center C of the third portion 2c.

The third portion 2c resonates the light generated in the active layer 30. That is, in the third portion 2c, a resonator is formed. The planar shape of the third portion 2c is, for example, a circle.

In the semiconductor laser 100, the active layer 30 can be distorted by the first portion 2a and the second portion 2b. When the first portion 2a and the second portion 2b give strain to the active layer 30, tensile stress is generated in the active layer 30 in a predetermined direction. As a result, the third portion 2c constituting the resonator is not optically isotropic, and the light generated in the active layer 30 is polarized. Therefore, the polarization of the light generated in the active layer 30 can be stabilized. Here, when light is polarized, it means that the vibration direction of the electric field of light is constant.

As shown in FIGS. 3 and 4, the first portion 2a has a recess 90. In the example shown in FIG. 3, the first portion 2a has two recesses 90, and the two recesses 90 are arranged along the first axis A1.

As shown in FIG. 4, the recess 90 has a wall portion 92 and a space 94. The wall portion 92 has an oxidation region 8. In the illustrated example, the first mirror layer 20 has a base portion 20a and a protrusion 20b provided on the base portion 20a. The space 94 is defined by a wall portion 92 and a base portion 20a. The protrusion 20b constitutes the laminated body 2, and the laminated body 2 is arranged on the base 20a. In the illustrated example, the recess 90 is a hole in which the space 94 is surrounded by the wall portion 92 in a plan view. Although not shown, the recess 90 may be filled with the resin layer 70.

The depth H of the recess 90 and the height T of the laminated body 2 are, for example, equal. Here, the "depth H of the recess 90" is the maximum length of the space 94 of the recess 90 along the Z axis. Further, the "height T of the laminated body 2" is the shortest distance between the upper surface 4a of the laminated body 2 and the base portion 20a. The “upper surface 4a of the laminated body 2” is the surface of the laminated body 2 farthest from the substrate 10. In the illustrated example, the height T of the laminated body 2 is the Z axis between the corner portion 4c formed by the upper surface 4a of the laminated body 2 and the side surface 4b of the laminated body 2 and the base portion 20a of the first mirror layer 20. The distance along. Although not shown, the depth H may be smaller than the height T of the laminated body 2.

As shown in FIG. 3, the length L1 along the first axis A1 of the space 94 of the recess 90 is equal to, for example, the length L2 along the second axis A2 of the space 94 of the recess 90. The "length L1" is the maximum length along the first axis A1 of the space 94 of the recess 90. The "length L2" is the maximum length along the second axis A2 of the space 94 of the recess 90. When the recess 90 is a hole, the length L1 and the length L2 are the lengths of the openings of the recess 90 defined by the corners 4c, as shown in FIG. The second axis A2 is an axis orthogonal to the first axis A1 and is parallel to the X axis in the illustrated example.

As shown in FIG. 3, the length L3 of the first portion 2a along the second axis A2 is smaller than the length L4 of the third portion 2c along the second axis A2. Here, the "length L3" refers to the side surface of the first portion 2a that intersects the second axis A2 on one side of the first axis A1 and the second side of the first portion 2a on the other side of the first axis A1. The maximum distance between the side surface intersecting the axis A2. Similarly, the "length L4" is the maximum length along the second axis A2 of the third portion 2c.

As shown in FIG. 3, the oxidized region 8 of the first portion 2a intersects the second axis A2 at least three times in a plan view. The second axis A2 can be set at an arbitrary position as long as it is orthogonal to the first axis A1 and intersects the first portion 2a.

In the illustrated example, the second axis A2 passes through the recess 90 and intersects the oxidation region 8 four times. Specifically, the second axis A2 has an oxidation region 8a forming the outer edge of the first portion 2a on one side of the first axis A1 and a wall portion 92 of the recess 90 on one side of the first axis A1. Oxidation region 8b constituting the oxide region 8b forming the wall portion 92 of the recess 90 on the other side of the first axis A1 and the oxidation region forming the outer edge of the first portion 2a on the other side of the first axis A1. It intersects with 8d. As described above, in the semiconductor laser 100, the second axis A2 intersects the oxidation regions 8b and 8c forming the wall portion 92 of the recess 90 in addition to the oxidation regions 8a and 8d forming the outer edge of the first portion 2a. ..

The oxidation region 8 of the second portion 2b also intersects an axis (not shown) orthogonal to the first axis A1 at least three times, similarly to the first portion 2a.

Further, although the AlGaAs-based semiconductor laser has been described above, in the semiconductor laser according to the present embodiment, for example, GaInP-based, ZnSSe-based, InGaN-based, AlGaN-based, InGaAs-based, GaInNAs-based, depending on the oscillation wavelength, A GaAsSb-based semiconductor material may be used.

1.2. Manufacturing Method of Semiconductor Laser Next, the manufacturing method of the semiconductor laser 100 according to the first embodiment will be described with reference to the drawings. 5 to 7 are cross-sectional views schematically showing a manufacturing process of the semiconductor laser 100 according to the first embodiment.

As shown in FIG. 5, the first mirror layer 20, the active layer 30, the oxidized layer 42a which is oxidized to become the current constriction layer 42, the second mirror layer 40, and the contact layer 50 are epitaxially grown on the substrate 10. .. Examples of the method for epitaxial growth include a MOCVD (Metal Organic Chemical Vapor Deposition) method and an MBE (Molecular Beam Epitaxy) method.

Next, the contact layer 50, the second mirror layer 40, the oxidized layer 42a, the active layer 30, and the first mirror layer 20 are patterned to form the laminated body 2. Further, as shown in FIG. 4, a recess 90 is formed. Patterning is performed, for example, by photolithography and etching.

As shown in FIG. 6, the oxidized layer 42a is oxidized to form the current constriction layer 42. The oxidized layer 42a is, for example, an Al _x Ga _1-x As layer when x ≧ 0.95. For example, the substrate 10 provided with the laminated body 2 is put into a water vapor atmosphere at about 400 ° C. to oxidize the Al _x Ga _1-x As layer from the side surface to form the current constriction layer 42.

In the oxidation step of oxidizing the oxidized layer 42a to form the current constriction layer 42, for example, when 0.85 ≦ x ≦ 0.90, the Al _x Ga _1-x As layer constituting the first mirror layer 20 is formed. Arsenic is replaced with oxygen, and the first oxide layer 6 is formed as shown in FIG. As a result, the first region 60 is formed. Similarly, the arsenic in the Al _x Ga _1-x As layer constituting the second mirror layer 40 is replaced with oxygen, and the second oxide layer 16 is formed as shown in FIG. As a result, the second region 62 is formed. As shown in FIG. 4, the first region 60 and the second region 62 constituting the oxidation region 8 are formed on the outer edge of the laminated body 2 and the wall portion 92 of the recess 90.

The volumes of the first region 60 and the second region 62 are reduced by the replacement of arsenic with oxygen. As a result, the upper surface 63 of the second region 62 is inclined. Specifically, the volume of the first region 60 and the second region 62 is reduced by about 30% due to the reduction of the interstitial distance due to the strong electronegativity due to the replacement of arsenic with oxygen. As described above, in the oxidation step, the volume of the oxidation region 8 including the first region 60 and the second region 62 contracts. Therefore, the larger the volume of the oxidation region 8 of the first portion 2a and the second portion 2b, the higher the volume. The tensile stress generated in the third portion 2c by the first portion 2a and the second portion 2b can be increased.

As shown in FIG. 7, the resin layer 70 is formed so as to surround the laminated body 2. The resin layer 70 is formed by forming a layer made of polyimide resin or the like on the upper surface of the first mirror layer 20 and the entire surface of the laminate 2 by using, for example, a spin coating method, and patterning the layer. Patterning is performed, for example, by photolithography and etching. Next, the resin layer 70 is cured by heat treatment.

As shown in FIG. 2, the second electrode 82 is formed on the contact layer 50 and the resin layer 70, and the first electrode 80 is formed on the first mirror layer 20. The first electrode 80 and the second electrode 82 are formed by, for example, a combination of a vacuum deposition method and a lift-off method. The order in which the first electrode 80 and the second electrode 82 are formed is not particularly limited. Further, in the step of forming the second electrode 82, the pad 84 and the lead-out wiring 86 shown in FIG. 1 may be formed.

By the above steps, the semiconductor laser 100 can be manufactured.

1.3. Effect The semiconductor laser 100 has, for example, the following effects.

In the semiconductor laser 100, the oxidation region 8 of the first portion 2a intersects the second axis A2 orthogonal to the first axis A1 at least three times in a plan view. Therefore, in the semiconductor laser 100, as shown in FIG. 8, the oxidation region 8 is provided only on the outer edge of the laminate 2, and the oxidation region 8 is oxidized at least once more than when the oxidation region 8 intersects the second axis A2 twice. The region 8 intersects the second axis A2. Therefore, in the semiconductor laser 100, since the oxidation region 8 is provided in addition to the outer edge of the laminate 2 shown in FIG. 8, the volume of the oxidation region 8 of the first portion 2a can be increased by that amount. Therefore, the tensile stress generated in the third portion 2c by the first portion 2a can be increased. Further, in the semiconductor laser 100, the volume of the oxidation region 8 of the first portion 2a can be increased without increasing the width W of the oxidation region 8. Therefore, it is possible to reduce the possibility that a defect will occur in the third portion 2c as compared with the case where the width W is increased. As described above, in the semiconductor laser 100, the tensile stress generated in the third portion 2c by the first portion 2a can be increased regardless of the width W of the oxidation region 8. As a result, it is possible to provide a semiconductor laser 100 having a long life and stable polarization. This makes it possible to provide, for example, a semiconductor laser 100 that is suitable for an atomic oscillator and has little fluctuation in wavelength and light intensity.

As a comparative example, FIG. 8 is a plan view schematically showing a semiconductor laser in which the oxidation region 8 of the first portion 2a intersects the second axis A2 twice in a plan view. In order to increase the volume of the oxidation region 8 in the semiconductor laser of FIG. 8, it is necessary to increase the width W of the oxidation region. The first portion 2a and the third portion 2c have the same layer structure. Therefore, if the Al composition ratio of the low refractive index layers 26 and 46 is increased in order to increase the width W of the oxidation region 8 of the first portion 2a, the Al composition ratio of the low refractive index layers 26 and 46 of the third portion 2c also increases. As the size increases, the width of the oxidation region 8 of the third portion 2c also increases. As a result, defects are likely to occur in the third portion 2c.

Further, the first portion 2a and the second portion 2b are point-symmetric with respect to the center C of the third portion 2c. Therefore, in the second portion 2b, the tensile stress generated in the third portion 2c by the first portion 2a can be increased as in the case of the first portion 2a.

In the semiconductor laser 100, the Al composition ratio of the AlGaAs layers, which are the low refractive index layers 26 and 46, is, for example, 0.85. As described above, the low refractive index layers 26 and 46 are oxidized to form the oxidation region 8. When the Al composition ratio is 0.85, the width W of the oxidation region 8 can be reduced as compared with the case where the Al composition ratio is 0.90, for example. Therefore, the stress generated in the third portion 2c by the oxidation region 8 of the third portion 2c can be reduced. This makes it possible to reduce the possibility of defects in the third portion 2c. Further, in the semiconductor laser 100, as described above, since the oxidation region 8 of the first portion 2a intersects the second axis A2 at least once more, even if the width W of the oxidation region 8 becomes smaller, the first portion It is possible to prevent the tensile stress generated in the third portion 2c from being reduced by 2a.

In the semiconductor laser 100, the first portion 2a has a recess 90, and the second axis A2 intersects the oxidation region 8 of the wall portion 92 constituting the recess 90. As described above, in the oxidation step of forming the current constriction layer 42, the oxidation region 8 is formed on the wall portion 92 of the recess 90. Therefore, in the semiconductor laser 100, the volume of the oxidation region 8 of the first portion 2a can be increased as compared with the case where the first portion 2a does not have the recess 90. Therefore, the tensile stress generated in the third portion 2c by the first portion 2a can be increased.

In the semiconductor laser 100, the depth H of the recess 90 and the height T of the laminate 2 are equal. Therefore, in the semiconductor laser 100, the recess 90 can be formed in the step of forming the laminated body 2. Therefore, apart from the step of forming the laminated body 2, the manufacturing process can be simplified as compared with the case of forming the recess 90.

1.4. Modification example 1.4.1. First Modified Example Next, the semiconductor laser according to the first modified example of the first embodiment will be described with reference to the drawings. FIG. 9 is a plan view schematically showing the semiconductor laser 110 according to the first modification of the first embodiment. For convenience, the members other than the laminated body 2 are not shown in FIG.

Hereinafter, in the semiconductor laser 110 according to the first modification of the first embodiment, the same reference numerals are given to the members having the same functions as the constituent members of the semiconductor laser 100 according to the first embodiment described above, and the details thereof are given. Explanation is omitted. This is the same for the semiconductor laser according to the second and third modifications of the first embodiment described later.

In the semiconductor laser 100 described above, as shown in FIG. 3, the length L1 of the recess 90 along the first axis A1 of the space 94 is equal to the length L2 of the recess 90 along the second axis A2. It was.

On the other hand, in the semiconductor laser 110, as shown in FIG. 9, the length L1 along the first axis A1 of the space 94 of the recess 90 is the length L2 along the second axis A2 of the space 94 of the recess 90. Greater than. As described above, the first portion 2a protrudes from the third portion 2c along the first axis A1. That is, the recess 90 has a shape in which the length L1 along the protruding direction of the first portion 2a is larger than the length L2 along the second axis A2 in a plan view.

In the illustrated example, in the first portion 2a, the two recesses 90 are arranged along the second axis A2. The oxidized region 8 of the first portion 2a intersects the second axis A2 six times in a plan view.

In the semiconductor laser 110, the length L1 of the recess 90 along the first axis A1 is larger than the length L2 of the recess 90 along the second axis A2 in a plan view. Therefore, the length of the oxidation region 8 formed on the wall portion 92 of the recess 90 along the first axis A1 can be made larger than the length along the second axis A2. Therefore, in the semiconductor laser 110, the amount of contraction of the oxidation region 8 due to the replacement of arsenic with oxygen in the oxidation step along the first axis A1 is reduced as compared with the case where the length L1 is the length L2 or less in a plan view. Can be made larger. Therefore, the tensile stress generated in the third portion 2c by the first portion 2a can be further increased.

1.4.2. Second Modified Example Next, the semiconductor laser according to the second modified example of the first embodiment will be described with reference to the drawings. FIG. 10 is a plan view schematically showing the semiconductor laser 120 according to the second modification of the first embodiment. For convenience, the members other than the laminated body 2 are not shown in FIG.

In the semiconductor laser 100 described above, as shown in FIG. 3, the length L3 of the first portion 2a along the second axis A2 is smaller than the length L4 of the third portion 2c along the second axis A2. ..

On the other hand, in the semiconductor laser 120, as shown in FIG. 10, the length L3 of the first portion 2a along the second axis A2 is larger than the length L4 of the third portion 2c along the second axis A2. large.

The first portion 2a includes a narrow portion 122 having a length along the second axis A2 smaller than the third portion 2c and a wide portion 124 having a length along the second axis A2 larger than the third portion 2c. Have. The narrow portion 122 is arranged between the third portion 2c and the wide portion 124 in a plan view. The narrow portion 122 is connected to the third portion 2c and the wide portion 124.

The wide portion 124 has a recess 90. In the illustrated example, in the wide portion 124, the two recesses 90 are arranged along the second axis A2. The oxidized region 8 of the first portion 2a intersects the second axis A2 six times in a plan view.

In the semiconductor laser 120, the length L3 of the first portion 2a along the second axis A2 is larger than the length L4 of the third portion 2c along the second axis A2. Therefore, in the semiconductor laser 120, the recess 90 is more likely to be formed in the first portion 2a than in the case where the length L3 is the length L4 or less. For example, when the length L3 is the length L4 or less, the length of the recess 90 along the second axis A2 must be reduced depending on the number of the recess 90, which may make it difficult to form the recess 90. ..

14.3. Third Modified Example Next, the semiconductor laser according to the third modified example of the first embodiment will be described with reference to the drawings. FIG. 11 is a cross-sectional view schematically showing the semiconductor laser 130 according to the third modification of the first embodiment. For convenience, FIG. 11 shows the laminated body 2 in a simplified manner.

In the semiconductor laser 100 described above, as shown in FIG. 4, the depth H of the recess 90 and the height T of the laminate 2 were equal.

On the other hand, in the semiconductor laser 130, as shown in FIG. 11, the depth H of the recess 90 is larger than the height T of the laminated body 2. In the method for manufacturing the semiconductor laser 130, for example, after the laminate 2 is formed, the recess 90 is formed in the laminate 2 so that the depth H is larger than the height T.

In the semiconductor laser 130, since the depth H of the recess 90 is larger than the height T of the laminated body 2, the oxidation formed on the wall portion 92 of the recess 90 is more than the case where the depth H is the height T or less. The volume of the region 8 can be increased. Therefore, in the semiconductor laser 130, the tensile stress generated in the third portion 2c by the first portion 2a can be further increased.

2. Second Embodiment 2.1. Semiconductor laser Next, the semiconductor laser according to the second embodiment will be described with reference to the drawings. FIG. 12 is a plan view schematically showing the semiconductor laser 200 according to the second embodiment. For convenience, in FIG. 12, members other than the laminated body 2 are not shown.

Hereinafter, in the semiconductor laser 200 according to the second embodiment, the same reference numerals are given to the members having the same functions as the constituent members of the semiconductor laser 100 according to the first embodiment described above, and detailed description thereof will be omitted. ..

In the semiconductor laser 100 described above, as shown in FIG. 3, the recess 90 is a hole in which the space 94 is surrounded by the wall portion 92.

On the other hand, in the semiconductor laser 200, as shown in FIG. 12, the recess 90 is a notch portion with one end open. The recess 90 has a shape in which a wall portion having a side surface intersecting with the first axis A1 is opened in a plan view. As a result, the first portion 2a has a branched structure.

In the semiconductor laser 200, the oxidation region 8 of the first portion 2a intersects the second axis A2 at least three times in a plan view. Therefore, similarly to the semiconductor laser 100 described above, the first portion 2a forms the third portion 2c. The tensile stress generated can be increased.

Further, in the semiconductor laser 200, since the length L1 along the first axis A1 of the space 94 of the recess 90 is larger than the length L2 along the second axis A2 of the space 94 of the recess 90, the above-mentioned semiconductor laser Similar to 110, the tensile stress generated by the first portion 2a in the third portion 2c can be further increased.

When the recess 90 is a notch, as shown in FIG. 12, the length L1 is the side surface of the laminated body 2 that defines the space 94 of the recess 90, and the angle formed by the side surface 4b1 intersecting the first axis A1. It is a distance along the first axis A1 between the portion 4c and the corner portion 4c formed by the side surface 4b2 of the laminated body 2 provided with the opening of the recess 90.

2.2. Manufacturing Method of Semiconductor Laser Next, a manufacturing method of the semiconductor laser 200 according to the second embodiment will be described.

The method for manufacturing the semiconductor laser 200 according to the second embodiment is basically the same as the method for manufacturing the semiconductor laser 100 according to the first embodiment described above. Therefore, the detailed description thereof will be omitted.

2.3. Modification example 23.1. First Modified Example Next, the semiconductor laser according to the first modified example of the second embodiment will be described with reference to the drawings. FIG. 13 is a plan view schematically showing the semiconductor laser 210 according to the first modification of the second embodiment. For convenience, in FIG. 13, members other than the laminated body 2 are not shown.

Hereinafter, in the semiconductor laser 210 according to the first modification of the second embodiment, the same reference numerals are given to the members having the same functions as the constituent members of the semiconductor laser 200 according to the second embodiment described above, and the details thereof are given. Explanation is omitted. This is the same for the semiconductor laser according to the second, third, and fourth modifications of the first embodiment described later.

In the semiconductor laser 200 described above, as shown in FIG. 12, the oxidation region 8 of the first portion 2a intersects the second axis A2 four times in a plan view.

On the other hand, in the semiconductor laser 200, as shown in FIG. 13, the oxidation region 8 of the first portion 2a intersects the second axis A2 six times in a plan view. Therefore, in the semiconductor laser 210, the tensile stress generated in the third portion 2c by the first portion 2a can be made larger than that in the semiconductor laser 200, for example. In the semiconductor laser 210, the first portion 2a has two recesses 90, and the two recesses 90 are arranged along the second axis A2.

2.3.2. Second Modified Example Next, the semiconductor laser according to the second modified example of the second embodiment will be described with reference to the drawings. FIG. 14 is a plan view schematically showing the semiconductor laser 220 according to the second modification of the second embodiment. For convenience, the members other than the laminated body 2 are not shown in FIG.

In the semiconductor laser 200 described above, as shown in FIG. 12, the oxidation region 8 of the first portion 2a intersects the second axis A2 four times in a plan view.

On the other hand, in the semiconductor laser 220, as shown in FIG. 14, the oxidation region 8 of the first portion 2a intersects the second axis A2 three times in a plan view. For example, by adjusting the length of the first portion 2a along the second axis A2 and the length of the recess 90 along the second axis A2 of the space 94, as shown in FIG. The oxidation region 8 can be formed so that the entire portion 2a overlaps the oxidation region 8.

2.3.3. Third Modified Example Next, the semiconductor laser according to the third modified example of the second embodiment will be described with reference to the drawings. FIG. 15 is a plan view schematically showing the semiconductor laser 230 according to the third modification of the second embodiment. For convenience, the members other than the laminated body 2 are not shown in FIG.

In the semiconductor laser 200 described above, as shown in FIG. 12, the oxidation region 8 of the first portion 2a intersects the second axis A2 four times in a plan view.

On the other hand, in the semiconductor laser 230, as shown in FIG. 15, the oxidation region 8 of the first portion 2a intersects the second axis A2 14 times in a plan view. Therefore, in the semiconductor laser 230, the tensile stress generated in the third portion 2c by the first portion 2a can be made larger than that in the semiconductor laser 200, for example.

In the semiconductor laser 230, the first portion 2a has seven recesses 90, and the seven recesses 90 are arranged along the second axis A2. In the semiconductor laser 230, similarly to the semiconductor laser 120 described above, the length L3 of the first portion 2a along the second axis A2 is larger than the length L4 of the third portion 2c along the second axis A2. Therefore, many recesses 90 can be formed in the first portion 2a along the second axis A2.

2.3.4. Fourth Modified Example Next, the semiconductor laser according to the fourth modified example of the second embodiment will be described with reference to the drawings. FIG. 16 is a plan view schematically showing the semiconductor laser 240 according to the fourth modification of the second embodiment. For convenience, the members other than the laminated body 2 are not shown in FIG.

As shown in FIG. 16, the semiconductor laser 240 differs from the above-mentioned semiconductor laser 200 in that the length of the recess 90 along the second axis A2 of the space 94 increases with respect to the distance from the third portion 2c. .. The first portion 2a has two recesses 90, and the two recesses 90 are arranged along the second axis A2. As shown in FIG. 16, the first portion 2a has a tapered shape in a plan view.

3. 3. Third Embodiment 3.1. Semiconductor laser Next, the semiconductor laser according to the third embodiment will be described with reference to the drawings. FIG. 17 is a plan view schematically showing the semiconductor laser 300 according to the third embodiment. FIG. 18 is a cross-sectional view taken along the line XVIII-XVIII of FIG. 17 schematically showing the semiconductor laser 300 according to the third embodiment.

Hereinafter, in the semiconductor laser 300 according to the third embodiment, the members having the same functions as the constituent members of the semiconductor laser 200 according to the second embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted. ..

As shown in FIGS. 17 and 18, the semiconductor laser 300 differs from the above-mentioned semiconductor laser 200 in that it includes a columnar portion 301. For convenience, in FIG. 17, members other than the laminated body 2 and the columnar portion 301 are not shown. Further, in FIG. 18, the laminated body 2 and the columnar portion 301 are shown in a simplified manner.

As shown in FIG. 18, the columnar portion 301 includes, for example, the first layer 302, the second layer 303, the third layer 304, the fourth layer 305, the fifth layer 306, and the oxidation region 8. Have.

The first layer 302 is arranged on the first mirror layer 20. The material of the first layer 302 is the same as that of the first mirror layer 20 constituting the laminated body 2. The second layer 303 is arranged on the first layer 302. The material of the second layer 303 is the same as that of the active layer 30 constituting the laminated body 2. The third layer 304 is arranged on the second layer 303. The material of the third layer 304 is the same as that of the current constriction layer 42 constituting the laminated body 2. The fourth layer 305 is arranged on the third layer 304. The material of the fourth layer 305 is the same as that of the second mirror layer 40 constituting the laminated body 2. The fifth layer 306 is arranged on the fourth layer 305. The material of the fifth layer 306 is the same as that of the contact layer 50 constituting the laminated body 2. The oxidation region 8 is formed by oxidizing the first layer 302 and the fourth layer 305 from the side surface in the oxidation step for forming the current constriction layer 42. As described above, the columnar portion 301 has the same layer structure as the laminated body 2.

As shown in FIG. 17, the columnar portion 301 has a recess 90. The oxidized region 8 of the columnar portion 301 intersects the second axis A2 at least three times in a plan view. In the illustrated example, the oxidized region 8 of the columnar portion 301 intersects the second axis A2 four times in a plan view. The length of the columnar portion 301 along the first axis A1 is larger than the length of the columnar portion 301 along the second axis A2. The columnar portion 301 has a rotationally symmetric shape in a plan view.

The columnar portion 301 is arranged so as to be separated from the laminated body 2. Two columnar portions 301 are arranged. The laminated body 2 is arranged between the two columnar portions 301 in a plan view. In plan view, the two columnar portions 301 are point symmetric with respect to the center C of the third portion 2c.

In the semiconductor laser 300, the length of the columnar portion 301 along the first axis A1 is larger than the length of the columnar portion 301 along the second axis A2, and the oxidized region 8 of the columnar portion 301 is the third in a plan view. It intersects the 2-axis A2 at least 3 times. Therefore, the tensile stress generated in the third portion 2c by the columnar portion 301 can be increased.

3.2. Manufacturing Method of Semiconductor Laser Next, a manufacturing method of the semiconductor laser 300 according to the third embodiment will be described.

The method for manufacturing the semiconductor laser 300 according to the third embodiment is the same as the method for manufacturing the semiconductor laser 200 according to the second embodiment described above, except that the columnar portion 301 is further formed in the step of forming the laminate 2. Is similar. Therefore, the detailed description thereof will be omitted.

3.3. Modification Example Next, the semiconductor laser according to the modification of the third embodiment will be described with reference to the drawings. FIG. 19 is a plan view schematically showing the semiconductor laser 310 according to the third embodiment. For convenience, in FIG. 19, members other than the laminated body 2 and the columnar portion 301 are not shown.

Hereinafter, in the semiconductor laser 310 according to the third embodiment, the members having the same functions as the constituent members of the semiconductor laser 300 according to the third embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted. ..

In the semiconductor laser 300 described above, the oxidation region 8 of the columnar portion 301 intersects the second axis A2 four times in a plan view.

On the other hand, in the semiconductor laser 310, the oxidation region 8 of the columnar portion 301 intersects the second axis A2 six times in a plan view. Further, the oxidized region 8 of the first portion 2a intersects the second axis A2 six times in a plan view. Therefore, in the semiconductor laser 310, the tensile stress generated in the third portion 2c by the first portion 2a and the columnar portion 301 can be made larger than that in the semiconductor laser 300, for example.

4. Fourth Embodiment Next, the atomic oscillator according to the fourth embodiment will be described with reference to the drawings. FIG. 20 is a diagram showing the configuration of the atomic oscillator 400 according to the fourth embodiment.

The atomic oscillator 400 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 due to this quantum interference effect is also called an electromagnetically induced transparency (EIT) phenomenon. Further, the atomic oscillator according to the present embodiment may be an atomic oscillator utilizing a double resonance phenomenon caused by light and microwaves.

The atomic oscillator 400 includes the semiconductor laser 100 according to the first embodiment.

As shown in FIG. 20, the atomic oscillator 400 includes a light emitting element module 410, a neutral density filter 422, a lens 424, a 1/4 wave plate 426, an atomic cell 430, a light receiving element 440, and a heater 450. It includes a temperature sensor 460, a coil 470, and a control circuit 480.

The light emitting element module 410 includes a semiconductor laser 100, a Peltier element 412, and a temperature sensor 414. The semiconductor laser 100 emits linearly polarized light LL containing two types of light having different frequencies. The temperature sensor 414 detects the temperature of the semiconductor laser 100. The Peltier element 412 controls the temperature of the semiconductor laser 100.

The neutral density filter 422 reduces the intensity of the light LL emitted from the semiconductor laser 100. The lens 424 adjusts the emission angle of the light LL. Specifically, the lens 424 makes the light LL parallel light. The quarter wave plate 426 converts two types of light contained in the light LL having different frequencies from linearly polarized light to circularly polarized light.

The atomic cell 430 is irradiated with the light emitted from the semiconductor laser 100. The atomic cell 430 transmits the light LL emitted from the semiconductor laser 100. Alkali metal atoms are housed in the atomic cell 430. The alkali metal atom has an energy level of a three-level system consisting of two different basis levels and an excited level. The light LL emitted from the semiconductor laser 100 is incident on the atomic cell 430 via the neutral density filter 422, the lens 424, and the quarter wave plate 426.

The light receiving element 440 detects the intensity of the excitation light LL that has passed through the atomic cell 430, and outputs a detection signal according to the intensity of the light. As the light receiving element 440, for example, a photodiode can be used.

The heater 450 controls the temperature of the atomic cell 430. The heater 450 heats the alkali metal atoms contained in the atomic cell 430 and puts at least a part of the alkali metal atoms into a gas state.

The temperature sensor 460 detects the temperature of the atomic cell 430. The coil 470 generates a magnetic field that Zeeman splits a plurality of degenerate energy levels of alkali metal atoms in the atomic cell 430. Coil 470 can improve resolution by widening the gap between different degenerate energy levels of alkali metal atoms due to Zeeman splitting. As a result, the accuracy of the oscillation frequency of the atomic oscillator 400 can be improved.

The control circuit 480 includes a temperature control circuit 482, a temperature control circuit 484, a magnetic field control circuit 486, and a light source control circuit 488.

The temperature control circuit 482 controls the energization of the Peltier element 412 so that the temperature of the semiconductor laser 100 becomes a desired temperature based on the detection result of the temperature sensor 414. The temperature control circuit 484 controls the energization of the heater 450 so that the inside of the atomic cell 430 has a desired temperature based on the detection result of the temperature sensor 460. The magnetic field control circuit 486 controls the energization of the coil 470 so that the magnetic field generated by the coil 470 is constant.

The light source control circuit 488 controls the frequencies of two types of light contained in the light LL emitted from the semiconductor laser 100 so that the EIT phenomenon occurs based on the detection result of the light receiving element 440. 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 contained in an atomic cell 430. The light source control circuit 488 includes a voltage-controlled oscillator 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). Is output as a clock signal of the atomic oscillator 400.

The control circuit 480 is provided, for example, on an IC (Integrated Circuit) chip mounted on a substrate (not shown). The control circuit 480 may be a single IC, or may be a combination of a plurality of digital circuits or analog circuits.

The application of the semiconductor laser 100 is not limited to the light source of the atomic oscillator. The semiconductor laser 100 may be used, for example, as a laser for communication or distance measurement.

5. Fifth Embodiment Next, the frequency signal generation system according to the fifth embodiment will be described with reference to the drawings. The following clock transmission system as a timing server is an example of a frequency signal generation system. FIG. 21 is a schematic configuration diagram showing a clock transmission system 900.

The clock transmission system 900 includes the atomic oscillator 400 according to the fourth embodiment.

The clock transmission system 900 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. 21, the clock transmission system 900 includes a clock supply device 901 and an SDH (Synchronous Digital Hierarchy) device 902 of station A, a clock supply device 903 and SDH device 904 of station B, and a clock supply device of station C. 905 and SDH devices 906 and 907 are provided. The clock supply device 901 has an atomic oscillator 400 and generates an N-system clock signal. The clock supply device 901 has a terminal 910 into which a frequency signal from the atomic oscillator 400 is input. The atomic oscillator 400 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 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 400 and generates an E-system clock signal. The clock supply device 903 has a terminal 911 into which a frequency signal from the atomic oscillator 400 is input. The atomic oscillator 400 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 the fifth embodiment is not limited to the clock transmission system. The frequency signal generation system includes a system in which an atomic oscillator is mounted and is composed of various devices and a plurality of devices that utilize the frequency signal of the atomic oscillator. The frequency signal generation system includes a control unit that controls an atomic oscillator.

The frequency signal generation system according to the fifth embodiment includes, for example, a liquid discharge device such as a smartphone, a tablet terminal, a clock, a mobile phone, a digital still camera, an inkjet printer, a personal computer, a television, a video camera, a video tape recorder, and a car navigation system. Equipment, 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, fish finder, GNSS (Global) Navigation Satellite System) It may be a frequency standard, various measuring devices, instruments, a flight simulator, a terrestrial digital broadcasting system, a mobile phone base station, or a mobile body.

Examples of the medical device include an electronic thermometer, a sphygmomanometer, a blood glucose meter, an electrocardiogram measuring device, an ultrasonic diagnostic device, an electronic endoscope, and a magnetocardiograph. Examples of the above-mentioned instruments include instruments such as automobiles, aircrafts, and ships. Examples of the moving body include automobiles, aircrafts, ships and the like.

In the present invention, some configurations may be omitted, or each embodiment or modification may be combined within the range having the features and effects described in the present application.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the present invention includes substantially the same configuration as that described in the embodiments. A substantially identical configuration is, for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect. The present invention also includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. The present invention also includes a configuration that exhibits the same effects as the configuration described in the embodiment or a configuration that can achieve the same object. The present invention also includes a configuration in which a known technique is added to the configuration described in the embodiment.

2 ... Laminated body, 2a ... 1st part, 2b ... 2nd part, 2c ... 3rd part, 4a ... Top surface, 4b, 4b1, 4b2 ... Side surface, 4c ... Corner part, 6 ... First oxide layer, 8,8a , 8b, 8c, 8d ... Oxidation region, 9a, 9b ... Edge, 10 ... Substrate, 14 ... Layer, 16 ... Second oxide layer, 20 ... First mirror layer, 20a ... Base, 20b ... Projection, 24 ... High Refractive electrode layer, 26 ... Low refractive electrode layer, 30 ... Active layer, 40 ... Second mirror layer, 42 ... Current constriction layer, 42a ... Oxidized layer, 43 ... Opening, 44 ... High refractive electrode layer, 46 ... Low Refractory layer, 48 ... top surface, 50 ... contact layer, 60 ... first region, 62 ... second region, 63 ... top surface, 70 ... resin layer, 80 ... first electrode, 82 ... second electrode, 84 ... pad, 86 ... lead-out wiring, 90 ... recess, 92 ... wall part, 94 ... space, 100, 110, 120 ... semiconductor laser, 122 ... narrow part, 124 ... wide part, 130, 200, 210, 220, 230, 240, 300 ... semiconductor laser, 301 ... columnar part, 302 ... first layer, 303 ... second layer, 304 ... third layer, 305 ... fourth layer, 306 ... fifth layer, 310 ... semiconductor laser, 400 ... atomic oscillator, 410 ... light emitting element module, 412 ... Pelche element, 414 ... temperature sensor, 422 ... dimming filter, 424 ... lens, 426 ... 1/4 wave plate, 430 ... atomic cell, 440 ... light receiving element, 450 ... heater, 460 ... Temperature sensor, 470 ... Coil, 480 ... Control circuit, 482 ... Temperature control circuit, 484 ... Temperature control circuit, 486 ... Magnetic field control circuit, 488 ... Light source control circuit, 900 ... Clock transmission system, 901 ... Clock supply device, 902 ... SDH device, 903 ... clock supply device, 904 ... SDH device, 905 ... clock supply device, 906, 907 ... SDH device, 908, 909 ... master clock, 910, 911 ... terminal

Claims (7)

With the first mirror layer
With the second mirror layer
An active layer arranged between the first mirror layer and the second mirror layer,
A current constriction layer arranged between the first mirror layer and the second mirror layer,
A first region which is continuously provided with the first mirror layer and includes a plurality of first oxide layers,
A second region that is continuously provided with the second mirror layer and includes a plurality of second oxide layers,
Including
The first mirror layer, the second mirror layer, the active layer, the current constriction layer, the first region, and the second region constitute a laminated body.
The first region and the second region constitute an oxidation region of the laminate.
The laminated body is in a plan view.
The first part and
The second part and
A third portion, which is arranged between the first portion and the second portion and resonates the light generated in the active layer,
Have,
The first portion, the second portion, and the third portion are arranged along a first axis passing through the center of the third portion in a plan view.
A semiconductor laser in which the oxidized region of the first portion intersects a second axis orthogonal to the first axis at least three times in a plan view. In claim 1,
The first part has a recess
The second axis is a semiconductor laser that intersects the oxidation region of the wall portion forming the recess. In claim 2,
A semiconductor laser in which the length of the recessed space along the first axis is greater than the length of the recessed space along the second axis. In claim 2 or 3,
A semiconductor laser in which the depth of the recess and the height of the laminate are equal. In claim 2 or 3,
A semiconductor laser in which the depth of the recess is larger than the height of the laminate. In any one of claims 1 to 5,
A semiconductor laser in which the length of the first portion along the second axis is larger than the length of the third portion along the second axis. With a semiconductor laser
An atomic cell containing an alkali metal atom, which is irradiated with the light emitted from the semiconductor laser, and
A light receiving element that detects the intensity of light transmitted through the atomic cell and outputs a detection signal.
Including
The semiconductor laser is
With the first mirror layer
With the second mirror layer
An active layer arranged between the first mirror layer and the second mirror layer,
A current constriction layer arranged between the first mirror layer and the second mirror layer,
A first region which is continuously provided with the first mirror layer and includes a plurality of first oxide layers,
A second region that is continuously provided with the second mirror layer and includes a plurality of second oxide layers,
Including
The first mirror layer, the second mirror layer, the active layer, the current constriction layer, the first region, and the second region constitute a laminated body.
The first region and the second region constitute an oxidation region of the laminate.
The laminated body is in a plan view.
The first part and
The second part and
A third portion, which is arranged between the first portion and the second portion and resonates the light generated in the active layer,
Have,
The first portion, the second portion, and the third portion are arranged along a first axis passing through the center of the third portion in a plan view.
An atomic oscillator in which the oxidized region of the first portion intersects a second axis orthogonal to the first axis at least three times in a plan view.

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