JP2021114489A - Semiconductor laser and atomic oscillator - Google Patents

Abstract

To provide a semiconductor laser in which the current density at the top of an opening part of a current constriction layer can be reduced.SOLUTION: A semiconductor laser includes a first mirror layer, a second mirror layer, an active layer disposed between the first mirror layer and the second mirror layer, a current constriction layer disposed between the first mirror layer and the second mirror layer, a contact layer disposed in the second mirror layer, and an electrode including a connection part to be connected to the contact layer. The current constriction layer includes an opening that becomes a route of current. The shape of the opening is a quadrangle including a first side, a second side, a third side, and a fourth side in a plan view. L12>L1, L12>L2, L23>L2, L23>L3, L34>L3, L34>L4, L41>L4, and L41>L1 are satisfied.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.

In Patent Document 1, as a method for forming a current constriction layer, a laminated structure processed into a mesapost is oxidized in a water vapor atmosphere, and the AlAs layer is oxidized from the outer peripheral side of the mesapost to form a current constriction layer. The method is described. Further, Patent Document 1 describes that when the AlAs layer is oxidized to form a current constriction layer, the shape of the opening serving as the current inflow region of the current constriction layer becomes substantially square. Further, in a plan view, an annular p-side electrode surrounding the opening of the current constriction layer is described.

JP-A-2009-117540

When the shape of the opening of the current constriction layer is quadrangular, the current applied from the electrodes is concentrated on the vertices of the quadrangle, which may cause defects in the semiconductor layer constituting the semiconductor laser. When a defect occurs in the semiconductor layer in this way, the defect becomes a resistor or light is absorbed by the defect, causing fluctuations in characteristics. For example, when a defect acts as a resistance and generates heat, the temperature of the semiconductor laser fluctuates and the wavelength fluctuates. Further, for example, when light is absorbed by a defect, the light output decreases.

One aspect of the semiconductor laser according to the present invention includes a first mirror layer, a second mirror layer, an active layer arranged between the first mirror layer and the second mirror layer, and the first mirror layer. The current includes a current constriction layer arranged between the second mirror layer and the second mirror layer, a contact layer arranged in the second mirror layer, and an electrode having a connecting portion connected to the contact layer. The constriction layer has an opening that serves as a path for current, and the shape of the opening is a quadrangle having a first side, a second side, a third side, and a fourth side in a plan view, and is a plan view. The shortest distance between the connection portion and the first side is L1, the shortest distance between the connection portion and the second side is L2 in plan view, and the connection portion and the connection portion are in plan view. The shortest distance between the third side is L3, the shortest distance between the connection portion and the fourth side is L4 in plan view, and the connection portion and the first side are in plan view. Let L12 be the shortest distance between the second side and the first apex, and in plan view, the shortest distance between the connecting portion and the second apex formed by the second side and the third side. Is L23, and the shortest distance between the connecting portion and the third apex formed by the third side and the fourth side is L34 in a plan view. Assuming that the shortest distance between the side and the fourth apex formed by the first side is L41, L12> L1, L12> L2, L23> L2, L23> L3, L34> L3, L34> L4, L41> Satisfy L4, L41> L1.

One aspect of the semiconductor laser according to the present invention includes a first mirror layer, a second mirror layer, an active layer arranged between the first mirror layer and the second mirror layer, and the first mirror layer. The current includes a current constriction layer arranged between the second mirror layer and the second mirror layer, a contact layer arranged in the second mirror layer, and an electrode having a connecting portion connected to the contact layer. The constriction layer has an opening that serves as a path for electric current, and the shape of the opening is a quadrangle in a plan view, and the connection portion and an extension line of the diagonal line of the quadrangle intersect in a plan view. do not.

One aspect of the atomic oscillator according to the present invention detects a semiconductor laser, an atomic cell containing an alkali metal atom irradiated with light emitted from the semiconductor laser, and the intensity of light transmitted through the atomic cell. The semiconductor laser is arranged between the first mirror layer, the second mirror layer, the first mirror layer, and the second mirror layer, including a light receiving element that outputs a detection signal. An active layer, a current constriction layer arranged between the first mirror layer and the second mirror layer, a contact layer arranged in the second mirror layer, and a connection portion connected to the contact layer. The current constriction layer has an opening that serves as a path for the current, and the shape of the opening is the first side, the second side, the third side, and the fourth side in a plan view. It is a quadrangle having sides, and the shortest distance between the connecting portion and the first side is L1 in a plan view, and the shortest distance between the connecting portion and the second side is L2 in a plan view. In plan view, the shortest distance between the connecting portion and the third side is L3, in plan view, the shortest distance between the connecting portion and the fourth side is L4, and in plan view, the above. The shortest distance between the connecting portion and the first apex formed by the first side and the second side is L12, and the connecting portion, the second side, and the third side form in a plan view. The shortest distance between the second apex and the second apex is L23, and the shortest distance between the connecting portion and the third apex formed by the third side and the fourth side is L34 in the plan view. When the shortest distance between the connecting portion and the fourth apex formed by the fourth side and the first side is L41, L12> L1, L12> L2, L23> L2, L23> L3, L34. > L3, L34> L4, L41> L4, L41> L1.

One aspect of the atomic oscillator according to the present invention detects a semiconductor laser, an atomic cell containing an alkali metal atom irradiated with light emitted from the semiconductor laser, and the intensity of light transmitted through the atomic cell. The semiconductor laser is arranged between the first mirror layer, the second mirror layer, the first mirror layer, and the second mirror layer, including a light receiving element that outputs a detection signal. The active layer, the current constriction layer arranged between the first mirror layer and the second mirror layer, the contact layer arranged in the second mirror layer, and the connecting portion connected to the contact layer. The current constriction layer includes an electrode having an electric current, and the current constriction layer has an opening that serves as a path for electric current, and the shape of the opening is a quadrangle in a plan view, and the connection portion and the quadrangle in a plan view. Does not intersect the diagonal extension of.

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 figure for demonstrating the positional relationship between a connection part and an opening. 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 the modification of 1st Embodiment. The figure for demonstrating the positional relationship between a connection part and an opening. The plan view which shows typically the semiconductor laser which concerns on 2nd Embodiment. The cross-sectional view which shows typically the semiconductor laser which concerns on 2nd Embodiment. The cross-sectional view which shows typically the semiconductor laser which concerns on 2nd Embodiment. The figure for demonstrating the positional relationship between a connection part and an opening. The plan view which shows typically the semiconductor laser which concerns on the modification of 2nd Embodiment. The figure for demonstrating the positional relationship between a connection part and an opening. The figure which shows the structure of the atomic oscillator which concerns on 3rd Embodiment. The figure for demonstrating an example of the frequency signal generation system which concerns on 4th Embodiment.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unreasonably limit the content 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. Note that FIGS. 1 and 2 show an X-axis, a Y-axis, and a Z-axis 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: Vertical).
Cavity Surface Emitting Laser). As shown in FIGS. 1 and 2, 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 50, a contact layer 60, and a resin. It includes a layer 70, a first electrode 80, and a second electrode 82.

The substrate 10 is, for example, an n-type GaAs substrate.

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. The first mirror layer 20 is configured by alternately laminating high refractive index layers and low refractive index layers. The high refractive index layer is, for example, an n-type Al _0.12 Ga _0.88 As layer doped with silicon. The low refractive index layer is, for example, an n-type Al _0.9 Ga _0.1 As layer doped with silicon. The number of layers of the high refractive index layer and the low refractive index layer 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 on the side opposite to the substrate 10 side with respect to the active layer 30. The second mirror layer 40 is arranged between the active layer 30 and the contact layer 60. The second mirror layer 40 is, for example, a p-type semiconductor layer. The second mirror layer 40 is different in conductive type from the first mirror layer 20. 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 and low refractive index layers. The high refractive index layer is, for example, a carbon-doped p-type Al _0.12 Ga _0.88 As layer. The low refractive index layer is, for example, a carbon-doped p-type Al _0.9 Ga _0.1 As layer. The number of layers of the high refractive index layer and the low refractive index layer is, for example, 3 pairs or more and 40 pairs or less.

The first mirror layer 20, the active layer 30, and the second mirror layer 40 form a resonator that resonates the light generated in the active layer 30.

The current constriction layer 50 is arranged between the first mirror layer 20 and the second mirror layer 40. In the example shown in FIG. 2, the current constriction layer 50 is arranged inside the second mirror layer 40. The current constriction layer 50 may be arranged, for example, on the active layer 30. The current constriction layer 50 is, for example, a layer in which the Al _x Ga _1-x As layer (x ≧ 0.95) is oxidized. The current constriction layer 50 is provided with an opening 59 that serves as a current path. The current constriction layer 50 can prevent the current injected into the active layer 30 from spreading in the plane of the active layer 30.

The contact layer 60 is arranged on the second mirror layer 40. The contact layer 60 is a p-type semiconductor layer. The contact layer 60 is, for example, a carbon-doped p-type GaAs layer.

A part of the first mirror layer 20, the active layer 30, the second mirror layer 40, the current constriction layer 50, and the contact layer 60 constitute the laminated body 2. As shown in FIG. 2, the laminated body 2 has a columnar shape. 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. The shape of the laminated body 2 is, for example, a circle 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 resin layer 70 is arranged on the side surface of the laminated body 2. The resin layer 70 is partially arranged on the upper surface of the laminated body 2. The material of the resin layer 70 is, for example, polyimide.

The first electrode 80 is arranged on the first mirror layer 20. The first electrode 80 is in ohmic contact with the first mirror layer 20. The first electrode 80 is electrically connected to the first mirror layer 20. As the first electrode 80, for example, one in which the AuGe layer, the Ni layer, the Ti layer, and the Au layer are laminated in this order from the first mirror layer 20 side is used. The first electrode 80 is one electrode for injecting an electric current into the active layer 30. Although not shown, the first electrode 80 may be provided on the lower surface of the substrate 10.

The second electrode 82 is arranged on the contact layer 60. The second electrode 82 is in ohmic contact with the contact layer 60. In the illustrated example, the second electrode 82 is further arranged on the resin layer 70. The second electrode 82 is electrically connected to the second mirror layer 40 via the contact layer 60. As the second electrode 82, for example, one in which the AuGe layer, the Ni layer, the Ti layer, and the Au layer are laminated in this order from the contact layer 60 side is used. The second electrode 82 is the other electrode for injecting an electric current into the active layer 30.

The second electrode 82 is electrically connected to the pad 84. In the illustrated example, the second electrode 82 is electrically connected to the pad 84 via the lead wire 86. The pad 84 and the lead-out wiring 86 are provided on the resin layer 70. The material of the pad 84 and the lead-out wiring 86 is, for example, the same as the material of the second electrode 82.

FIG. 3 is a diagram for explaining the positional relationship between the connection portion 8 connected to the contact layer 60 of the second electrode 82 and the opening 59 of the current constriction layer 50. Note that FIG. 3 shows only the second electrode 82 and the contact layer 60.

The second electrode 82 has a connecting portion 8 connected to the contact layer 60. As shown in FIG. 2, the second electrode 82 is connected to the contact layer 60 at the connecting portion 8. The connection portion 8 is a portion where the second electrode 82 is in contact with the contact layer 60, and a current is applied from the connection portion 8 to the contact layer 60. The connecting portion 8 is, for example, a portion where the second electrode 82 is in ohmic contact with the contact layer 60.

As shown in FIG. 3, the shape of the opening 59 of the current constriction layer 50 is a quadrangle having a first side 51, a second side 52, a third side 53, and a fourth side 54 in a plan view. The opening 59 is a first apex 55 formed by the first side 51 and the second side 52, a second apex 56 formed by the second side 52 and the third side 53, and the third side 53 and the fourth side in a plan view. It is a quadrangle having a third vertex 57 formed by the side 54 and a fourth vertex 58 formed by the fourth side 54 and the first side 51.

In the example shown in FIG. 3, the shape of the opening 59 is square in a plan view. The current constriction layer 50 is formed by oxidizing the oxidized layer 50a shown in FIGS. 4 and 5 described later from the side surface of the laminated body 2. The opening 59 formed in the current constriction layer 50 is a portion of the oxidized layer 50a that remains without being oxidized. Since the semiconductor layer to be the oxidized layer 50a has anisotropy in the oxidation rate depending on the crystal orientation, the shape of the opening 59 reflects the anisotropy in the oxidation rate depending on the crystal orientation. For example, when the oxidized layer 50a is composed of an Al _x Ga _1-x As layer (x ≧ 0.95), the shape of the opening 59 is, for example, a quadrangle. Further, when the shape of the laminated body 2 is a circle in a plan view, the shape of the opening 59 is, for example, a square.

Here, as shown in FIG. 3, the shortest distance between the connecting portion 8 and the first side 51 in a plan view is L1, and the shortest distance between the connecting portion 8 and the second side 52 in a plan view is L2. Let L3 be the shortest distance between the connecting portion 8 and the third side 53 in a plan view, and L4 be the shortest distance between the connecting portion 8 and the fourth side 54 in a plan view. Further, the shortest distance between the connecting portion 8 and the first vertex 55 in the plan view is L12, the shortest distance between the connecting portion 8 and the second vertex 56 in the plan view is L23, and the connecting portion 8 in the plan view. The shortest distance between the apex 57 and the third apex 57 is L34, and the shortest distance between the connecting portion 8 and the fourth apex 58 in a plan view is L41. In this case, in the semiconductor laser 100, the connection portion 8 and the opening 59 satisfy the following positional relationship (hereinafter, also referred to as “first positional relationship”).

L12> L1, L12> L2
L23> L2, L23> L3
L34> L3, L34> L4
L41> L4, L41> L1

In the example shown in FIG. 3, the opening 59 is located inside the opening 7 of the connecting portion 8 in a plan view. The shape of the opening 7 of the connecting portion 8 matches the shape of the opening of the second electrode 82. The opening 7 of the connecting portion 8 is a first straight line portion 8a parallel to the first side 51, a second straight line portion 8b parallel to the second side 52, and a third straight line parallel to the third side 53 in a plan view. A portion 8c, a fourth straight portion 8d parallel to the fourth side 54, a first curved portion 9a connecting the first straight portion 8a and the second straight portion 8b, a second straight portion 8b, and a third straight portion. A second curved portion 9b connecting the 8c, a third curved portion 9c connecting the third straight portion 8c and the fourth straight portion 8d, and a second connecting the fourth straight portion 8d and the first straight portion 8a. It has a shape having four curved portions 9d.

The first straight line portion 8a is parallel to the first side 51 of the opening 59, and the second straight line portion 8b is parallel to the second side 52 of the opening 59. The first curved portion 9a is an arc centered on the first apex 55 of the opening 59. Therefore, the shortest distance L12 between the connecting portion 8 and the first apex 55 of the opening 59 is the radius of the arc formed by the first curved portion 9a. Further, the shortest distance L1 between the connecting portion 8 and the first side 51 is the shortest distance between the first straight line portion 8a and the first side 51, and is the shortest distance between the connecting portion 8 and the second side 52. The distance L2 is the shortest distance between the second straight line portion 8b and the second side 52. Here, the radius of the arc formed by the first curved portion 9a is from the shortest distance between the first straight line portion 8a and the first side 51 and the shortest distance between the second straight line portion 8b and the second side 52. Is also big. Therefore, L12> L1 and L12> L2 are satisfied.

Similarly, the second straight line portion 8b is parallel to the second side 52 of the opening 59, and the third straight line portion 8c is parallel to the third side 53 of the opening 59. The second curved portion 9b is an arc centered on the second apex 56 of the opening 59. Therefore, the shortest distance L23 between the connecting portion 8 and the second apex 56 of the opening 59 is the radius of the arc formed by the second curved portion 9b. Further, the shortest distance L2 between the connecting portion 8 and the second side 52 is the shortest distance between the second straight line portion 8b and the second side 52, and is the shortest distance between the connecting portion 8 and the third side 53. The distance L3 is the shortest distance between the third straight line portion 8c and the third side 53. Here, the radius of the arc formed by the second curved portion 9b is based on the shortest distance between the second straight portion 8b and the second side 52 and the shortest distance between the third straight portion 8c and the third side 53. Is also big. Therefore, L23> L2 and L23> L3 are satisfied.

Similarly, the third straight line portion 8c is parallel to the third side 53 of the opening 59, and the fourth straight line portion 8d is parallel to the fourth side 54 of the opening 59. The third curved portion 9c is an arc centered on the third apex 57 of the opening 59. Therefore, the shortest distance L34 between the connecting portion 8 and the third apex 57 of the opening 59 is the radius of the arc formed by the third curved portion 9c. Further, the shortest distance L3 between the connecting portion 8 and the third side 53 is the shortest distance between the third straight line portion 8c and the third side 53, and the shortest distance between the connecting portion 8 and the fourth side 54. The distance L4 is the shortest distance between the fourth straight line portion 8d and the fourth side 54. Here, the radius of the arc formed by the third curved portion 9c is based on the shortest distance between the third straight portion 8c and the third side 53 and the shortest distance between the fourth straight portion 8d and the fourth side 54. Is also big. Therefore, L34> L3 and L34> L4 are satisfied.

Similarly, the fourth straight line portion 8d is parallel to the fourth side 54 of the opening 59, and the first straight line portion 8a is parallel to the first side 51 of the opening 59. The fourth curved portion 9d is an arc centered on the fourth apex 58 of the opening 59. Therefore, the shortest distance L41 between the connecting portion 8 and the fourth apex 58 of the opening 59 is the radius of the arc formed by the fourth curved portion 9d. Further, the shortest distance L4 between the connecting portion 8 and the fourth side 54 is the shortest distance between the fourth straight line portion 8d and the fourth side 54, and the shortest distance between the connecting portion 8 and the first side 51. The distance L1 is the shortest distance between the first straight line portion 8a and the first side 51. Here, the radius of the arc formed by the fourth curved portion 9d is from the shortest distance between the fourth straight line portion 8d and the fourth side 54 and the shortest distance between the first straight line portion 8a and the first side 51. Is also big. Therefore, L41> L4 and L41> L1 are satisfied.

In the example shown in FIG. 3, the shortest distance L12 between the connecting portion 8 and the first vertex 55, the shortest distance L23 between the connecting portion 8 and the second vertex 56, and the connecting portion 8 and the third vertex 57. The shortest distance between L34 and the shortest distance between the connecting portion 8 and the fourth vertex 58 is equal to L41. That is, in the semiconductor laser 100, the connection portion 8 and the opening 59 satisfy the positional relationship of L12 = L23 = L34 = L41 (hereinafter, also referred to as “second positional relationship”).

Further, in the example shown in FIG. 3, the shortest distance L1 between the connecting portion 8 and the first side 51, the shortest distance L2 between the connecting portion 8 and the second side 52, and the connecting portion 8 and the third side The shortest distance L3 between 53 and the shortest distance L4 between the connecting portion 8 and the fourth side 54 are equal to each other. That is, in the semiconductor laser 100, the connection portion 8 and the opening 59 satisfy the positional relationship of L1 = L2 = L3 = L4 (hereinafter, also referred to as “third positional relationship”).

In the example shown in FIG. 3, the opening 7 of the connecting portion 8 is symmetrical with respect to the first extension line L10 and symmetrical with respect to the second extension line L20. The first extension line L10 and the second extension line L20 are extensions of two diagonal lines of a quadrangle formed by the opening 59. In the illustrated example, one of the two diagonals of the quadrangle is parallel to the Y-axis and the other is parallel to the X-axis. Therefore, the first extension line L10 is a straight line parallel to the Y axis and passing through the center of the quadrangle, and the second extension line L20 is a straight line parallel to the X axis and passing through the center of the quadrangle.

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. Action effect The semiconductor laser 100 satisfies the relationship of L12> L1 and L12> L2. That is, in a plan view, the shortest distance between the connecting portion 8 and the first vertex 55 is L12, which is larger than the shortest distance L1 between the connecting portion 8 and the first side 51, and the connecting portion 8 and the first side 51. It is larger than the shortest distance L2 between the two sides 52. Therefore, the current density of the first vertex 55 can be reduced.

For example, in the case of L12 ≦ L1 and L12 ≦ L2, the current concentrates on the first apex 55 and the current density becomes high, causing defects in the active layer 30, the first mirror layer 20, the second mirror layer 40, and the like. There is. This defect may cause fluctuations in the characteristics of the semiconductor laser. On the other hand, in the semiconductor laser 100, the relationship of L12> L1 and L12> L2 is satisfied, and the first vertex 55 can be made farther from the connecting portion 8 than the first side 51 and the second side 52. The current density of the apex 55 can be reduced. As a result, the possibility that the current is concentrated on the first apex 55 and a defect is generated can be reduced.

Similarly, in the semiconductor laser 100, the relationship of L23> L2 and L23> L3 is satisfied. That is, in a plan view, the shortest distance L23 between the connecting portion 8 and the second vertex 56 is larger than the shortest distance L2 between the connecting portion 8 and the second side 52, and the connecting portion 8 and the third It is larger than the shortest distance L3 with the side 53. As a result, the second apex 56 can be made farther from the connecting portion 8 than the second side 52 and the third side 53, and the current density of the second apex 56 can be reduced.

Similarly, in the semiconductor laser 100, the relationship of L34> L3 and L34> L4 is satisfied. That is, in a plan view, the shortest distance between the connecting portion 8 and the third vertex 57 is L34, which is larger than the shortest distance L3 between the connecting portion 8 and the third side 53, and the connecting portion 8 and the third side 53. It is larger than the shortest distance L4 between the four sides 54. Therefore, the third apex 57 can be made farther from the connecting portion 8 than the third side 53 and the fourth side 54, and the current density of the third apex 57 can be reduced.

Similarly, in the semiconductor laser 100, the relationship of L41> L4 and L41> L1 is satisfied. That is, in a plan view, the shortest distance between the connecting portion 8 and the fourth vertex 58 is L41, which is larger than the shortest distance L4 between the connecting portion 8 and the fourth side 54, and the connecting portion 8 and the fourth side 54. It is larger than the shortest distance L1 with one side 51. Therefore, the fourth apex 58 can be made farther from the connecting portion 8 than the fourth side 54 and the first side 51, and the current density of the fourth apex 58 can be reduced.

As described above, in the semiconductor laser 100, the current densities of the four vertices of the opening 59 of the current constriction layer 50 can be reduced, so that the possibility of defects can be reduced. As a result, the semiconductor laser 100 can have high characteristic stability.

For example, a semiconductor laser used as a light source of an atomic oscillator is required to have high characteristic stability. For example, in an atomic oscillator provided with a Cs gas cell, a semiconductor laser having a wavelength of 895 nm is used as a light source. This semiconductor laser has an extremely high permissible fluctuation amount of wavelength of several to several tens of femtometres per day and ^{an extremely high permissible fluctuation amount of light output per day of 10-4} to ^10-3%. Stability is required. Therefore, the current is concentrated at the apex of the opening 59 to cause a minute defect, and even a small variation in the characteristics caused by the minute defect may not be tolerated. As described above, the semiconductor laser 100 can be used as a light source for an atomic oscillator because the current density at the apex of the opening 59 can be reduced and the semiconductor laser 100 has high characteristic stability.

The semiconductor laser 100 satisfies L12 = L23 = L34 = L41. Therefore, the difference in current densities at the four vertices of the opening 59 can be reduced. Therefore, in the semiconductor laser 100, it is possible to prevent the current from concentrating on one apex and causing defects.

1.3. Manufacturing Method of Semiconductor Laser Next, a manufacturing method of the semiconductor laser 100 will be described with reference to the drawings. 4 and 5 are cross-sectional views schematically showing a manufacturing process of the semiconductor laser 100.

As shown in FIG. 4, the first mirror layer 20, the active layer 30, the second mirror layer 40, the oxidized layer 50a which is oxidized to become the current constriction layer 50, and the contact layer 60 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 60, the second mirror layer 40, the oxidized layer 50a, the active layer 30, and the first mirror layer 20 are patterned to form the laminated body 2. Patterning is performed, for example, by photolithography and etching.

As shown in FIG. 5, the oxidized layer 50a is oxidized to form the current constriction layer 50. The oxidized layer 50a is, for example, an Al _x Ga _1-x As layer (x ≧ 0.95). For example, by throwing the substrate 10 provided with the laminated body 2 into a water vapor atmosphere of about 400 ° C., the Al _x Ga _1-x As layer (x ≧ 0.95) is oxidized from the side surface to form an opening. A current constriction layer 50 having 59 is formed. Since the _{oxidized layer 50a composed of the Al x} Ga _1-x As layer has anisotropy in the oxidation rate depending on the crystal orientation, the shape of the opening 59 is, for example, a square in a plan view.

As shown in FIG. 2, 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.

Next, the second electrode 82 is formed on the contact layer 60 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 vapor deposition method and a lift-off method. As shown in FIG. 3, the second electrode 82 is patterned so that the connecting portion 8 and the opening 59 satisfy the first positional relationship, the second positional relationship, and the third positional relationship.

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.

1.4. Modification Example FIG. 6 is a plan view schematically showing the semiconductor laser 110 according to the modification of the first embodiment. FIG. 7 is a diagram for explaining the positional relationship between the connection portion 8 connected to the contact layer 60 of the second electrode 82 and the opening 59. Note that FIG. 6 corresponds to FIG. 1 and FIG. 7 corresponds to FIG. Hereinafter, in the semiconductor laser 110 according to the present modification, the members having the same functions as the constituent members of the semiconductor laser 100 according to the first embodiment described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In the semiconductor laser 100 described above, as shown in FIG. 3, the shape of the opening 59 was square in a plan view. On the other hand, in the semiconductor laser 110, as shown in FIG. 7, the shape of the opening 59 is a rhombus in a plan view.

In the semiconductor laser 110, as shown in FIG. 6, the laminated body 2 has a first strain applying portion 2a, a second strain applying portion 2b, and a resonance portion 2c in a plan view.

The first distortion applying portion 2a and the second strain applying portion 2b sandwich the resonance portion 2c in a plan view. The first strain applying portion 2a protrudes from the resonance portion 2c in the Y-axis + direction. The second strain applying portion 2b projects from the resonance portion 2c in the Y-axis-direction. The first strain applying portion 2a and the second strain applying portion 2b are provided integrally with the resonance portion 2c. The laminated body 2 has a shape in which the longitudinal direction is along the Y axis in a plan view by providing the first strain applying portion 2a and the second strain applying portion 2b.

The resonance portion 2c is provided between the first strain applying portion 2a and the second strain applying portion 2b. The length of the resonance portion 2c along the X axis is larger than the length of the first strain applying portion 2a along the X axis or the length of the second strain applying portion 2b along the X axis. The shape of the resonance portion 2c is, for example, a circle in a plan view. The resonance portion 2c resonates the light generated in the active layer 30. That is, the resonance portion 2c constitutes a resonator.

The first strain-imparting unit 2a and the second strain-imparting unit 2b impart strain to the active layer 30 to polarize the light generated in the active layer 30. When the first strain applying portion 2a and the second strain applying portion 2b apply strain to the active layer 30, stress is generated in the active layer 30 in a predetermined direction. As a result, the resonant 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, the fact that light is polarized means that the vibration direction of the electric field of light is constant.

In the semiconductor laser 110, as described above, the shape of the laminate 2 is a shape whose longitudinal direction is along the Y axis in a plan view. Therefore, the shape of the opening 59 is, for example, a shape in which the longitudinal direction is the Y axis in a plan view. It becomes a rhombus along.

In the semiconductor laser 110, similarly to the semiconductor laser 100, the opening 7 of the connecting portion 8 is a first straight line portion 8a parallel to the first side 51 and a second straight line portion 8b parallel to the second side 52 in a plan view. The first curved line portion 9a connecting the third straight line portion 8c parallel to the third side 53, the fourth straight line portion 8d parallel to the fourth side 54, and the first straight line portion 8a and the second straight line portion 8b. A second curved line portion 9b connecting the second straight line portion 8b and the third straight line portion 8c, a third curved line portion 9c connecting the third straight line portion 8c and the fourth straight line portion 8d, and a fourth straight line portion. It has a shape having a fourth curved portion 9d connecting the 8d and the first straight portion 8a.

In the semiconductor laser 110, similarly to the semiconductor laser 100, the connection portion 8 and the opening 59 satisfy the first positional relationship. Therefore, in the semiconductor laser 110, the current densities of the four vertices of the opening 59 of the current constriction layer 50 can be reduced, and high characteristic stability can be obtained. Further, in the semiconductor laser 110, similarly to the semiconductor laser 100, the connection portion 8 and the opening 59 satisfy the second positional relationship and the third positional relationship.

The method for manufacturing the semiconductor laser 110 is to manufacture the semiconductor laser 100 except that the first strain applying portion 2a, the second strain applying portion 2b, and the resonance portion 2c are formed in the step of forming the laminated body 2. The method is the same, and the description thereof will be omitted. Since the laminated body 2 has the first strain applying portion 2a and the second strain applying portion 2b, in the step of oxidizing the oxidized layer 50a to form the current constriction layer 50, the shape of the opening 59 is, for example, a flat surface. It becomes a rhombus visually.

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. 8 is a plan view schematically showing the semiconductor laser 200 according to the second embodiment. FIG. 9 is a sectional view taken along line IX-IX of FIG. 8 schematically showing the semiconductor laser 200 according to the second embodiment. FIG. 10 is a sectional view taken along line XX of FIG. 8 schematically showing the semiconductor laser 200 according to the second embodiment.

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

As shown in FIGS. 9 and 10, the semiconductor laser 200 has an insulating layer 90. The insulating layer 90 is arranged on the contact layer 60. The insulating layer 90 is arranged between the contact layer 60 and the second electrode 82. The insulating layer 90 further covers the side surface of the laminate 2. The insulating layer 90 is, for example, an oxide film or a nitride film of a metal such as tantalum, aluminum, or titanium, or an oxide film or a nitride film of silicon. The insulating layer 90 functions as a protective film for protecting the laminate 2 from moisture, oxygen, and the like.

The insulating layer 90 has a contact hole 92 to which the second electrode 82 and the contact layer 60 are connected. The second electrode 82 is arranged on the insulating layer 90 and is connected to the contact layer 60 via the contact hole 92. That is, the shape of the contact hole 92 determines the shape of the connecting portion 8 of the second electrode 82. As described above, in the semiconductor laser 200, since the connecting portion 8 of the second electrode 82 can be formed by using the insulating layer 90 having the contact hole 92, the second electrode 82 is formed directly on the contact layer 60, for example. Compared with the case, the degree of freedom in the shape of the connecting portion 8 is high.

FIG. 11 is a diagram for explaining the positional relationship between the connection portion 8 connected to the contact layer 60 of the second electrode 82 and the opening 59. Note that FIG. 11 corresponds to FIG.

In the semiconductor laser 200, as shown in FIG. 11, the connecting portion 8 has a first portion 6a, a second portion 6b, a third portion 6c, and a fourth portion 6d. The first portion 6a, the second portion 6b, the third portion 6c, and the fourth portion 6d are separated from each other.

In a plan view, the connecting portion 8 and the first extension line L10 and the second extension line L20, which are extensions of the two diagonal lines of the quadrangle formed by the opening 59, do not intersect. The first extension line L10 passes between the fourth portion 6d and the first portion 6a, and between the second portion 6b and the third portion 6c. The second extension line L20 passes between the third portion 6c and the fourth portion 6d, and between the first portion 6a and the second portion 6b. Therefore, the connecting portion 8 does not intersect the first extension line L10 and the second extension line L20.

In the semiconductor laser 200, similarly to the semiconductor laser 100, the connection portion 8 and the opening 59 satisfy the first positional relationship, the second positional relationship, and the third positional relationship.

The connecting portion 8 has, for example, a shape in which a portion overlapping the first extension line L10 and a portion overlapping the second extension line L20 are cut out from the ring centered on the center of the opening 59. That is, the connecting portion 8 has a shape in which portions near the four vertices of the opening 59 are cut out from the ring. The width of the notched portion is, for example, a size that satisfies the first positional relationship, the second positional relationship, and the third positional relationship. The connecting portion 8 is, for example, symmetrical with respect to the first extension line L10 and symmetrical with respect to the second extension line L20 in a plan view.

2.2. Action effect In the semiconductor laser 200, the connecting portion 8 and the diagonal extension lines L10 and L20 of the quadrangle formed by the opening 59 do not intersect in a plan view. Therefore, in the semiconductor laser 200, for example, the current densities of the four vertices of the opening 59 can be reduced as compared with the case where the connecting portion 8 and the extension lines L10 and L20 intersect. As a result, the semiconductor laser 200 can have high characteristic stability.

In the semiconductor laser 200, the connection portion 8 and the opening 59 satisfy the first positional relationship. Therefore, in the semiconductor laser 200, similarly to the semiconductor laser 100, the current densities of the four vertices of the opening 59 of the current constriction layer 50 can be reduced, and high characteristic stability can be obtained.

2.3. Manufacturing Method of Semiconductor Laser Next, a manufacturing method of the semiconductor laser 200 will be described.

In the method of manufacturing the semiconductor laser 200, in the step of forming the current constriction layer 50, then forming the insulating layer 90 covering the laminate 2, and forming the second electrode 82, the second electrode 82 is formed through the contact hole 92. Connect to the contact layer 60. The other steps are the same as the method for manufacturing the semiconductor laser 100 described above, and the description thereof will be omitted.

2.4. Modification Example FIG. 12 is a plan view schematically showing the semiconductor laser 210 according to the modification of the second embodiment. FIG. 13 is a diagram for explaining the positional relationship between the connection portion 8 connected to the contact layer 60 of the second electrode 82 and the opening 59. Note that FIG. 12 corresponds to FIG. 8 and FIG. 13 corresponds to FIG. Hereinafter, in the semiconductor laser 210 according to the present modification, 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.

In the semiconductor laser 200 described above, as shown in FIG. 11, the shape of the opening 59 was square in a plan view. On the other hand, in the semiconductor laser 210, as shown in FIG. 13, the shape of the opening 59 is a rhombus in a plan view.

In the semiconductor laser 210, as shown in FIG. 12, the laminated body 2 has a first strain applying portion 2a, a second strain applying portion 2b, and a resonance portion 2c in a plan view. Therefore, the semiconductor laser 210 can stabilize the polarization of the light generated in the active layer 30.

In the semiconductor laser 210, similarly to the semiconductor laser 200, the connecting portion 8 and the extension lines L10 and L20 do not intersect in a plan view. Therefore, in the semiconductor laser 210, the current densities of the four vertices of the opening 59 can be reduced, and high characteristic stability can be obtained.

Similar to the semiconductor laser 200, the semiconductor laser 210 satisfies the first positional relationship, the second positional relationship, and the third positional relationship.

The connecting portion 8 has, for example, a shape in which a portion overlapping the first extension line L10 and a portion overlapping the second extension line L20 are cut out from the elliptical ring centered on the center of the opening 59. That is, the connecting portion 8 has a shape in which portions near the four vertices of the opening 59 are cut out from the elliptical ring. The width of the notched portion is, for example, a size that satisfies the first positional relationship, the second positional relationship, and the third positional relationship. The connecting portion 8 is, for example, symmetrical with respect to the first extension line L10 and symmetrical with respect to the second extension line L20 in a plan view.

In the semiconductor laser 210, similarly to the semiconductor laser 200, the connecting portion 8 and the extension lines L10 and L20 do not intersect in a plan view. Therefore, in the semiconductor laser 210, the current densities of the four vertices of the opening 59 of the current constriction layer 50 can be reduced, and high characteristic stability can be obtained.

The method for manufacturing the semiconductor laser 210 is to manufacture the semiconductor laser 200 except that the first strain applying portion 2a, the second strain applying portion 2b, and the resonance portion 2c are formed in the step of forming the laminated body 2. The method is the same, and the description thereof will be omitted.

3. 3. Third Embodiment Next, the atomic oscillator according to the third embodiment will be described with reference to the drawings. FIG. 14 is a diagram showing the configuration of the atomic oscillator 500 according to the third embodiment.

The atomic oscillator 500 has a quantum interference effect (CPT) in which when an alkali metal atom is simultaneously irradiated with two resonance lights having specific different wavelengths, the two resonance lights are transmitted without being absorbed by the alkali metal atoms. : Coherent Population Trapping) is used as an atomic oscillator. The phenomenon caused by this quantum interference effect is also called an electromagnetically induced transparency (EIT) phenomenon. Further, the atomic oscillator according to the present invention may be an atomic oscillator utilizing a double resonance phenomenon caused by light and microwaves.

The atomic oscillator 500 includes the semiconductor laser 100 according to the first embodiment as a light source. Although not shown, the atomic oscillator 500 may include the semiconductor laser 200 according to the second embodiment as a light source.

As shown in FIG. 14, the atomic oscillator 500 includes a light emitting element module 510, a neutral density filter 522, a lens 524, a 1/4 wave plate 526, an atomic cell 530, a light receiving element 540, and a heater 550. It includes a temperature sensor 560, a coil 570, and a control circuit 580.

The light emitting element module 510 includes a semiconductor laser 100, a Perche element 512, and a temperature sensor 514. The semiconductor laser 100 emits linearly polarized light LL containing two types of light having different frequencies. The temperature sensor 514 detects the temperature of the semiconductor laser 100. The Perche element 512 controls the temperature of the semiconductor laser 100.

The neutral density filter 522 reduces the intensity of the light LL emitted from the semiconductor laser 100. The lens 524 adjusts the emission angle of the light LL. Specifically, the lens 524 makes the light LL parallel light. The 1/4 wave plate 526 converts two types of light contained in the light LL having different frequencies from linearly polarized light to circularly polarized light.

The atomic cell 530 is irradiated with the light emitted from the semiconductor laser 100. The atomic cell 530 transmits the light LL emitted from the semiconductor laser 100. The atomic cell 530 contains an alkali metal atom. The alkali metal atom has an energy level of a three-level system consisting of two different ground levels and an excited level. The light LL emitted from the semiconductor laser 100 is incident on the atomic cell 530 via the neutral density filter 522, the lens 524, and the quarter wave plate 526.

The light receiving element 540 detects the intensity of the excitation light LL that has passed through the atomic cell 530, and outputs a detection signal according to the intensity of the light. As the light receiving element 540, for example, a photodiode can be used.

The heater 550 controls the temperature of the atomic cell 530. The heater 550 heats the alkali metal atoms contained in the atomic cell 530 and puts at least a part of the alkali metal atoms into a gas state.

The temperature sensor 560 detects the temperature of the atomic cell 530. The coil 570 generates a magnetic field that Zeeman splits a plurality of degenerate energy levels of alkali metal atoms in the atomic cell 530. Coil 570 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 500 can be improved.

The control circuit 580 includes a temperature control circuit 582, a temperature control circuit 584, a magnetic field control circuit 586, and a light source control circuit 588.

The temperature control circuit 582 controls the energization of the Perche element 512 so that the temperature of the semiconductor laser 100 becomes a desired temperature based on the detection result of the temperature sensor 514. The temperature control circuit 584 controls the energization of the heater 550 so that the inside of the atomic cell 530 has a desired temperature based on the detection result of the temperature sensor 560. The magnetic field control circuit 586 controls the energization of the coil 570 so that the magnetic field generated by the coil 570 is constant.

The light source control circuit 588 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 540. Here, the EIT phenomenon occurs when these two types of light become a resonance light pair having a frequency difference corresponding to the energy difference between the two base levels of the alkali metal atom contained in the atomic cell 530. The light source control circuit 588 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) Is output as a clock signal of the atomic oscillator 500.

The control circuit 580 is provided, for example, on an IC (Integrated Circuit) chip mounted on a substrate (not shown). The control circuit 580 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.

4. Fourth Embodiment Next, the frequency signal generation system according to the fourth 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. 15 is a schematic configuration diagram showing a clock transmission system 900.

The clock transmission system 900 includes the atomic oscillator 500 according to the third 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. 15, 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 500 and generates an N-system clock signal Nclk. The clock supply device 901 has a terminal 910 into which a frequency signal from the atomic oscillator 500 is input. The atomic oscillator 500 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 Nclk on the main signal, and transmits the N system clock signal Nclk to the lower clock supply device 905. The clock supply device 903 has an atomic oscillator 500 and generates an E-system clock signal Eclk. The clock supply device 903 has a terminal 911 into which a frequency signal from the atomic oscillator 500 is input. The atomic oscillator 500 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 Eclk on the main signal, and transmits the E-system clock signal Eclk 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 Nclk 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 Eclk 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 fourth 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 fourth 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 equipment, 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 instruments include automobiles.
Instruments such as aircraft and ships can be mentioned. Examples of the moving body include automobiles, aircrafts, ships and the like.

5. Others The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the present invention.

For example, the connection portion 8 of the semiconductor laser 100 according to the first embodiment shown in FIG. 3 described above may be realized by using the insulating layer 90 having the contact hole 92 shown in FIG. That is, a contact hole 92 having the same shape as that of the connecting portion 8 shown in FIG. 3 may be formed in the insulating layer 90 to provide the connecting portion 8.

Further, for example, the connection portion 8 of the semiconductor laser 200 according to the second embodiment shown in FIG. 11 described above is realized by directly forming the second electrode 82 on the contact layer 60 as shown in FIG. You may. That is, the second electrode 82 in the shape of the connecting portion 8 shown in FIG. 11 may be formed directly on the contact layer 60.

Further, for example, the connection portion 8 of the semiconductor laser 100 according to the first embodiment has a first straight line portion 8a, a second straight line portion 8b, a third straight line portion 8c, and a fourth straight line portion 8d. Each of these portions is not limited to one straight line, and may be a curved line, a plurality of straight lines, or a shape in which these are combined, as long as the first positional relationship is satisfied.

Further, for example, the connecting portion 8 of the semiconductor laser 100 according to the first embodiment has a first curved portion 9a, a second curved portion 9b, a third curved portion 9c, and a fourth curved portion 9d. Each of these portions is not limited to a single arc, and may be a curved line, a plurality of straight lines, or a shape in which these are combined, as long as the first positional relationship is satisfied.

The above-described embodiments and modifications are merely examples, and the present invention is not limited thereto. For example, each embodiment and each modification can be combined as appropriate.

The present invention includes a configuration substantially the same as the configuration described in the embodiment, 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. Further, the present invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

The following contents are derived from the above-described embodiments and modifications.

One aspect of the semiconductor laser is an active layer arranged between the first mirror layer, the second mirror layer, the first mirror layer and the second mirror layer, the first mirror layer and the second mirror layer. The current constriction layer includes a current constriction layer arranged between the mirror layer, a contact layer arranged in the second mirror layer, and an electrode having a connection portion connected to the contact layer. It has an opening that serves as a path for current, and the shape of the opening is a quadrangle having a first side, a second side, a third side, and a fourth side in a plan view, and the connection in a plan view. The shortest distance between the portion and the first side is L1, the shortest distance between the connection portion and the second side in plan view is L2, and the connection portion and the third side in plan view. The shortest distance between the two is L3, the shortest distance between the connection portion and the fourth side is L4 in plan view, and the connection portion, the first side, and the second side are in plan view. The shortest distance between the first apex and the second apex is L12, and the shortest distance between the connecting portion and the second apex between the second side and the third side is L23 in a plan view. In plan view, the shortest distance between the connection portion and the third apex formed by the third side and the fourth side is L34, and in plan view, the connection portion and the fourth side. When the shortest distance between the first side and the fourth apex is L41, L12> L1, L12> L2, L23> L2, L23> L3, L34> L3, L34> L4, L41> Satisfy L4, L41> L1.

In this semiconductor laser, since the connection portion and the opening of the current constriction layer satisfy the above relationship, the current densities of the four vertices of the opening of the current constriction layer can be reduced. Therefore, this semiconductor laser can reduce the possibility of defects and can have high characteristic stability.

In one aspect of the semiconductor laser, L12 = L23 = L34 = L41 may be satisfied.

With this semiconductor laser, the difference in current density between the four vertices of the opening can be reduced. Therefore, in this semiconductor laser, it is possible to prevent the current from concentrating on one apex and causing defects.

One aspect of the semiconductor laser is an active layer arranged between the first mirror layer, the second mirror layer, the first mirror layer and the second mirror layer, the first mirror layer and the second mirror layer. The current constriction layer includes a current constriction layer arranged between the mirror layer, a contact layer arranged in the second mirror layer, and an electrode having a connecting portion connected to the contact layer. It has an opening that serves as a path for electric current, and the shape of the opening is a quadrangle in a plan view, and the connection portion and an extension of the diagonal line of the quadrangle do not intersect in a plan view.

In this semiconductor laser, since the connecting portion and the extension line of the diagonal line of the quadrangle do not intersect in a plan view, the current densities of the four vertices of the opening are compared with the case where the connecting portion and the extension line intersect, for example. Can be reduced. Thereby, it is possible to have high characteristic stability.

In one aspect of a semiconductor laser, the quadrangle has a first side, a second side, a third side, and a fourth side, and in plan view, the shortest distance between the connecting portion and the first side. L1 is defined as the shortest distance between the connecting portion and the second side in plan view, and L3 is defined as the shortest distance between the connecting portion and the third side in plan view. The shortest distance between the connecting portion and the fourth side is L4, and the shortest distance between the connecting portion and the first apex formed by the first side and the second side in a plan view. Is L12, and the shortest distance between the connecting portion and the second apex formed by the second side and the third side in a plan view is L23, and in a plan view, the connecting portion and the first The shortest distance between the three sides and the third apex formed by the fourth side is L34, and in a plan view, the connecting portion, the fourth apex formed by the fourth side and the first side, and the fourth apex formed by the fourth side and the first side. When the shortest distance between them is L41, L12> L1, L12> L2, L23> L2, L23> L3, L34> L3, L34> L4, L41> L4, and L41> L1 may be satisfied.

In this semiconductor laser, since the connection portion and the opening of the current constriction layer satisfy the above relationship, the current densities of the four vertices of the opening of the current constriction layer can be reduced.

In one aspect of the semiconductor laser, L12 = L23 = L34 = L41 may be satisfied.

With this semiconductor laser, the difference in current density between the four vertices of the opening can be reduced. Therefore, in this semiconductor laser, it is possible to prevent the current from concentrating on one apex and causing defects.

In one aspect of a semiconductor laser, an insulating layer arranged between the electrode and the contact layer and having a contact hole for connecting the electrode and the contact layer may be included.

In this semiconductor laser, the first mirror layer, the second mirror layer, the active layer, the contact layer and the like can be protected from moisture, oxygen and the like.

One aspect of the atomic oscillator is to detect and detect a semiconductor laser, an atomic cell containing an alkali metal atom irradiated with light emitted from the semiconductor laser, and the intensity of light transmitted through the atomic cell. The semiconductor laser includes a light receiving element that outputs a signal, and the semiconductor laser includes an active layer arranged between a first mirror layer, a second mirror layer, the first mirror layer, and the second mirror layer. An current constriction layer arranged between the first mirror layer and the second mirror layer, a contact layer arranged in the second mirror layer, and an electrode having a connecting portion connected to the contact layer. The current constriction layer has an opening that serves as a path for the current, and the shape of the opening is a quadrangle having a first side, a second side, a third side, and a fourth side in a plan view. In plan view, the shortest distance between the connecting portion and the first side is L1, and in plan view, the shortest distance between the connecting portion and the second side is L2, and in plan view. The shortest distance between the connecting portion and the third side is L3, the shortest distance between the connecting portion and the fourth side is L4 in plan view, and the connecting portion and the connecting portion are defined in plan view. The shortest distance between the first side and the first apex formed by the second side is L12, and in a plan view, the connecting portion and the second apex formed by the second side and the third side The shortest distance between them is L23, and the shortest distance between the connection portion and the third apex formed by the third side and the fourth side is L34 in a plan view, and the connection portion is defined as a plan view. When the shortest distance between the fourth side and the fourth apex formed by the first side is L41, L12> L1, L12> L2, L23> L2, L23> L3, L34> L3, L34. > L4, L41> L4, L41> L1 are satisfied.

One aspect of the atomic oscillator is to detect and detect a semiconductor laser, an atomic cell containing an alkali metal atom irradiated with light emitted from the semiconductor laser, and the intensity of light transmitted through the atomic cell. The semiconductor laser includes a light receiving element that outputs a signal, and the semiconductor laser includes an active layer arranged between a first mirror layer, a second mirror layer, 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 contact layer arranged in the second mirror layer, and an electrode having a connecting portion connected to the contact layer. The current constriction layer has an opening that serves as a path for electric current, and the shape of the opening is a quadrangle in a plan view, and an extension of the connection portion and the diagonal line of the quadrangle in a plan view. It does not intersect the line.

2 ... Laminated body, 2a ... 1st strain applying portion, 2b ... 2nd strain applying portion, 2c ... Resonating portion, 6a ... 1st part, 6b ... 2nd part, 6c ... 3rd part, 6d ... 4th part, 7 ... Opening, 8 ... Connection part, 8a ... 1st straight line part, 8b ... 2nd straight line part, 8c ... 3rd straight line part, 8d ... 4th straight line part, 9a ... 1st curved part, 9b ... 2nd curved part , 9c ... 3rd curve part, 9d ... 4th curve part, 10 ... substrate, 20 ... first mirror layer, 30 ... active layer, 40 ... second mirror layer, 50 ... current constriction layer, 50a ... oxidized layer, 51 ... 1st side, 52 ... 2nd side, 53 ... 3rd side, 54 ... 4th side, 55 ... 1st vertex, 56 ... 2nd vertex, 57 ... 3rd vertex, 58 ... 4th vertex, 59 ... Opening, 60 ... contact layer, 70 ... resin layer, 80 ... first electrode, 82 ... second electrode, 84 ... pad, 86 ... lead wiring, 90 ... insulating layer, 92 ... contact hole, 100 ... semiconductor laser, 110 ... Semiconductor laser, 200 ... Semiconductor laser, 210 ... Semiconductor laser, 500 ... Atomic oscillator, 510 ... Light emitting element module, 512 ... Perche element, 514 ... Temperature sensor, 522 ... Dimming filter, 524 ... Lens, 526 ... 1/4 Wave plate, 530 ... atomic cell, 540 ... light receiving element, 550 ... heater, 560 ... temperature sensor, 570 ... coil, 580 ... control circuit, 582 ... temperature control circuit, 584 ... temperature control circuit, 586 ... magnetic field control circuit, 588 … 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 ... SDH device, 907 ... SDH device, 908 ... Master clock, 909 ... master clock, 910 ... terminal, 911 ... terminal

Claims (8)

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,
The contact layer arranged on the second mirror layer and
An electrode having a connecting portion connected to the contact layer and
Including
The current constriction layer has an opening that serves as a current path.
The shape of the opening is a quadrangle having a first side, a second side, a third side, and a fourth side in a plan view.
In a plan view, the shortest distance between the connecting portion and the first side is L1.
In a plan view, the shortest distance between the connecting portion and the second side is L2.
In a plan view, the shortest distance between the connecting portion and the third side is L3.
In a plan view, the shortest distance between the connecting portion and the fourth side is L4.
In a plan view, the shortest distance between the connecting portion and the first vertex formed by the first side and the second side is L12.
In a plan view, the shortest distance between the connecting portion and the second vertex formed by the second side and the third side is L23.
In a plan view, the shortest distance between the connecting portion and the third vertex formed by the third side and the fourth side is L34.
In a plan view, when the shortest distance between the connecting portion and the fourth vertex formed by the fourth side and the first side is L41.
L12> L1, L12> L2
L23> L2, L23> L3
L34> L3, L34> L4
L41> L4, L41> L1
A semiconductor laser that meets the requirements. In claim 1,
A semiconductor laser that satisfies L12 = L23 = L34 = L41. 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,
The contact layer arranged on the second mirror layer and
An electrode having a connecting portion connected to the contact layer and
Including
The current constriction layer has an opening that serves as a current path.
The shape of the opening is a quadrangle in a plan view.
A semiconductor laser in which the connection portion and the extension line of the diagonal line of the quadrangle do not intersect in a plan view. In claim 3,
The quadrangle has a first side, a second side, a third side, and a fourth side.
In a plan view, the shortest distance between the connecting portion and the first side is L1.
In a plan view, the shortest distance between the connecting portion and the second side is L2.
In a plan view, the shortest distance between the connecting portion and the third side is L3.
In a plan view, the shortest distance between the connecting portion and the fourth side is L4.
In a plan view, the shortest distance between the connecting portion and the first vertex formed by the first side and the second side is L12.
In a plan view, the shortest distance between the connecting portion and the second vertex formed by the second side and the third side is L23.
In a plan view, the shortest distance between the connecting portion and the third vertex formed by the third side and the fourth side is L34.
In a plan view, when the shortest distance between the connecting portion and the fourth vertex formed by the fourth side and the first side is L41.
L12> L1, L12> L2
L23> L2, L23> L3
L34> L3, L34> L4
L41> L4, L41> L1
A semiconductor laser that meets the requirements. In claim 4,
A semiconductor laser that satisfies L12 = L23 = L34 = L41. In any one of claims 1 to 5,
A semiconductor laser comprising an insulating layer arranged between the electrode and the contact layer and having a contact hole for connecting the electrode and the contact layer. With a semiconductor laser
An atomic cell containing an alkali metal atom, which is irradiated with light emitted from the semiconductor laser, and an atomic cell containing an alkali metal atom.
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,
The contact layer arranged on the second mirror layer and
An electrode having a connecting portion connected to the contact layer and
Including
The current constriction layer has an opening that serves as a current path.
The shape of the opening is a quadrangle having a first side, a second side, a third side, and a fourth side in a plan view.
In a plan view, the shortest distance between the connecting portion and the first side is L1.
In a plan view, the shortest distance between the connecting portion and the second side is L2.
In a plan view, the shortest distance between the connecting portion and the third side is L3.
In a plan view, the shortest distance between the connecting portion and the fourth side is L4.
In a plan view, the shortest distance between the connecting portion and the first vertex formed by the first side and the second side is L12.
In a plan view, the shortest distance between the connecting portion and the second vertex formed by the second side and the third side is L23.
In a plan view, the shortest distance between the connecting portion and the third vertex formed by the third side and the fourth side is L34.
In a plan view, when the shortest distance between the connecting portion and the fourth vertex formed by the fourth side and the first side is L41.
L12> L1, L12> L2
L23> L2, L23> L3
L34> L3, L34> L4
L41> L4, L41> L1
Atomic oscillator that meets. With a semiconductor laser
An atomic cell containing an alkali metal atom, which is irradiated with light emitted from the semiconductor laser, and an atomic cell containing an alkali metal atom.
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,
The contact layer arranged on the second mirror layer and
An electrode having a connecting portion connected to the contact layer and
Including
The current constriction layer has an opening that serves as a current path.
The shape of the opening is a quadrangle in a plan view.
An atomic oscillator in which the connection portion and the extension line of the diagonal line of the quadrangle do not intersect in a plan view.

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