WO2022172663A1 - 垂直共振器型面発光レーザ素子 - Google Patents
垂直共振器型面発光レーザ素子 Download PDFInfo
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- WO2022172663A1 WO2022172663A1 PCT/JP2022/000508 JP2022000508W WO2022172663A1 WO 2022172663 A1 WO2022172663 A1 WO 2022172663A1 JP 2022000508 W JP2022000508 W JP 2022000508W WO 2022172663 A1 WO2022172663 A1 WO 2022172663A1
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- H01S5/2054—Methods of obtaining the confinement
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- H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
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Definitions
- This technology relates to a vertical cavity surface emitting laser element that emits laser light in a direction perpendicular to the layer surface.
- a VCSEL (Vertical Cavity Surface Emitting Laser) element has a structure in which a light-emitting layer is sandwiched between a pair of reflecting mirrors.
- a current confinement structure is provided in the vicinity of the light emitting layer, and current is concentrated in a partial region (hereinafter referred to as a current injection region) in the light emitting layer due to the current confinement structure to generate spontaneous emission light.
- a pair of reflecting mirrors forms a resonator, and reflects light of a predetermined wavelength among spontaneous emission light toward the light-emitting layer, thereby causing laser oscillation.
- Non-Patent Document 1 a VCSEL device in which one of the reflecting mirrors is a concave mirror has been reported (see Non-Patent Document 1).
- an optical field constricted in the lateral direction (layer surface direction) is formed in the current injection region, and it is said that the size of the optical field can be controlled by the length of the resonator and the radius of curvature of the concave mirror. (See Non-Patent Documents 2 and 3).
- a semiconductor laser element such as a VCSEL element is generally used by providing an optical system externally to shape and adjust the emitted light. At that time, many of the external optical parts used exhibit an effect in a specific polarization direction. Therefore, the semiconductor laser device is required to have a specific polarization direction.
- anisotropy may be given to various parameters such as the structure (refractive index distribution) of the cavity (between a pair of reflecting mirrors), gain, and loss (including reflectance).
- anisotropy may be given to various parameters such as the structure (refractive index distribution) of the cavity (between a pair of reflecting mirrors), gain, and loss (including reflectance).
- each technique has strengths and weaknesses in the polarization selection system, and in general, a technique in which a plurality of polarization control methods are combined to obtain more robust polarization control is often adopted.
- One of the polarization control methods is the plane orientation of the crystal that constitutes the VCSEL element. If there is asymmetry in the crystal when viewed from the direction of light emission, then a spatial asymmetry is produced in the gain, so that the emitted light is also asymmetric, in this case with a specific polarization.
- a nitride VCSEL GaN-VCSEL
- the use of the m-plane or 20-21 plane tends to deviate polarized light in a specific direction (see Non-Patent Document 4).
- the C-plane which is often used to fabricate VCSEL elements, lacks asymmetry, and emitted light cannot be polarized in a specific manner, and is random depending on the VCSEL element.
- Polarization can also be controlled by using a plane close to the C-plane (a plane slightly inclined within several degrees from the C-plane).
- a plane close to the C-plane a plane slightly inclined within several degrees from the C-plane.
- only offsetting the C-plane has weaker polarization selectivity, and the expansion of the offset angle causes undulations called bunching on the substrate surface during crystal growth. I have a problem. This point is a problem when using the C plane. Few reports have hitherto been made on controlling the polarization in a specific direction in a GaN-VCSEL device using the C-plane.
- Another polarization control method is stress. Applying stress to the VCSEL device distorts the crystal and splits the band, making it possible to obtain polarized light in a specific direction. Still another polarization control method is to make the cavity structure asymmetric when viewed from the optical axis direction, thereby controlling the polarization in a specific direction according to the asymmetry.
- polarization is controlled by making the constriction structure in the lateral direction asymmetrical. For example, when GaAs is used, a laterally constricted structure is obtained by laterally oxidizing a layer containing high-concentration Al. known (see Non-Patent Documents 5 and 6).
- an object of the present technology is to provide a vertical cavity surface emitting laser element that has a concave mirror structure and excellent polarization controllability.
- a vertical cavity surface emitting laser device includes a first light reflecting layer, a second light reflecting layer, and a laminate.
- the first light reflecting layer reflects light of a specific wavelength.
- the second light reflecting layer reflects light of the wavelength.
- the laminate includes a first semiconductor layer made of a semiconductor material having a first conductivity type, a second semiconductor layer made of a semiconductor material having a second conductivity type, the first semiconductor layer and the second semiconductor layer. an active layer arranged between two semiconductor layers and emitting light by carrier recombination, and arranged between the first light reflecting layer and the second light reflecting layer.
- the laminate is provided with a current confinement structure that confines current and forms a current injection region in which the current concentrates.
- the first light reflecting layer is provided with a concave mirror having a concave surface on the laminate side and a convex surface on the opposite side of the laminate.
- a plan view of the current injection region viewed from the direction of the optical axis of the emitted light is defined as a first figure
- a plan view of contour lines representing the height of the concave mirror from the active layer viewed from the direction of the optical axis is defined as a second figure.
- the first figure and the second figure are not similar.
- a vertical cavity surface emitting laser device includes a first light reflecting layer, a second light reflecting layer, and a laminate.
- the first light reflecting layer reflects light of a specific wavelength.
- the second light reflecting layer reflects light of the wavelength.
- the laminate includes a first semiconductor layer made of a semiconductor material having a first conductivity type, a second semiconductor layer made of a semiconductor material having a second conductivity type, the first semiconductor layer and the second semiconductor layer. an active layer arranged between two semiconductor layers and emitting light by carrier recombination, and arranged between the first light reflecting layer and the second light reflecting layer.
- the laminate is provided with a current confinement structure that confines current and forms a current injection region in which the current concentrates.
- the first light reflecting layer is provided with a concave mirror having a concave surface on the laminate side and a convex surface on the opposite side of the laminate.
- a plan view of the current injection region viewed from the direction of the optical axis of the emitted light is defined as a first figure
- a plan view of contour lines representing the height of the concave mirror from the active layer viewed from the direction of the optical axis is defined as a second figure.
- the center of gravity of the first figure does not coincide with the center of gravity of the second figure.
- a vertical cavity surface emitting laser device includes a first light reflecting layer, a second light reflecting layer, and a laminate.
- the first light reflecting layer reflects light of a specific wavelength.
- the second light reflecting layer reflects light of the wavelength.
- the laminate includes a first semiconductor layer made of a semiconductor material having a first conductivity type, a second semiconductor layer made of a semiconductor material having a second conductivity type, the first semiconductor layer and the second semiconductor layer. an active layer arranged between two semiconductor layers and emitting light by carrier recombination, and arranged between the first light reflecting layer and the second light reflecting layer.
- the laminate is provided with a current confinement structure that confines current and forms a current injection region in which the current concentrates.
- the first light reflecting layer is provided with a concave mirror having a concave surface on the laminate side and a convex surface on the opposite side of the laminate.
- a plan view of the current injection region viewed from the direction of the optical axis of the emitted light is defined as a first figure
- a plan view of contour lines representing the height of the concave mirror from the active layer viewed from the direction of the optical axis is defined as a second figure.
- the first figure and the second figure are not perfect circles, but are similar.
- the first figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them
- the second graphic may be a closed graphic consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these, and may be a graphic dissimilar to the first graphic.
- a distance between the center of gravity of the first figure and the center of gravity of the second figure in a plane perpendicular to the direction of the optical axis may be 0.03 ⁇ m or more.
- the first figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them
- the second figure may be a circle, an ellipse, a rectangle, or a closed figure consisting of a combination of at least two of these, and may be similar to the first figure.
- the center of gravity of the first figure and the center of gravity of the second figure may coincide.
- the current confinement structure has a non-ion-implanted region into which ions are not implanted into the laminate, and an ion-implanted region provided around the non-ion-implanted region and into which ions are implanted into the laminate,
- the current injection region may be the non-ion-implanted region.
- the first semiconductor layer and the second semiconductor layer may be made of GaN.
- the first semiconductor layer may be a C-plane GaN substrate.
- the above ions may be boron ions.
- the current confinement structure has a tunnel junction region in which a tunnel junction is formed in the laminate, and a non-tunnel junction region provided around the tunnel junction region in which no tunnel junction is formed,
- the current injection region may be the tunnel junction region.
- the tunnel junction region may be formed by a buried tunnel junction.
- the tunnel junction region is formed by a tunnel junction layer into which ions are not implanted
- the non-tunnel junction region may be formed of a tunnel junction layer into which ions are implanted.
- the first semiconductor layer and the second semiconductor layer may be made of InP.
- the current confinement structure has a non-oxidized region in which the semiconductor material is not oxidized in the stacked body, and an oxidized region provided around the non-oxidized region and in which the semiconductor material is oxidized,
- the current injection region may be the non-oxidized region.
- the first semiconductor layer and the second semiconductor layer may be made of GaAs.
- the first semiconductor layer has a first surface on the side of the active layer and a second surface on the side opposite to the active layer, and the second surface is provided with a base forming a convex curved surface.
- the first light reflecting layer is a multilayer light reflecting film provided on the second surface, and the portion of the first light reflecting layer multilayer light reflecting film provided on the base serves as the concave mirror. may be formed.
- the first light reflecting layer is a multilayer light reflecting film provided on the second surface, and the portion of the first light reflecting layer multilayer light reflecting film provided on the base serves as the concave mirror. may be formed.
- the concave mirror may have a concave surface on the active layer side, and the concave surface may have a radius of curvature of 1000 ⁇ m or less.
- FIG. 1 is a cross-sectional view of a VCSEL device according to a first embodiment of the present technology
- FIG. 3 is an exploded cross-sectional view of a partial configuration of the VCSEL element
- FIG. 4 is a schematic diagram showing current injection regions and insulating regions of the VCSEL element
- FIG. It is a schematic diagram which shows the positional relationship of the electric current injection area
- It is a schematic diagram which shows the operation
- It is a schematic diagram which shows the contour line of the concave mirror with which the said VCSEL element is provided.
- FIG. 1 is a cross-sectional view of a VCSEL device according to a first embodiment of the present technology
- FIG. 3 is an exploded cross-sectional view of a partial configuration of the VCSEL element
- FIG. 4 is a schematic diagram showing current injection regions and insulating regions of the VCSEL element
- FIG. 4 is a schematic diagram showing a plane figure of contour lines of a concave mirror included in the VCSEL element.
- FIG. 4 is a schematic diagram showing a plan view of a current injection region included in the VCSEL element;
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region.
- FIG. 4 is a schematic diagram showing the relationship between the contour lines of the concave mirror provided in the VCSEL element and the plan figure of the current injection region. It is a schematic diagram which shows the manufacturing method of the said VCSEL element. It is a schematic diagram which shows the manufacturing method of the said VCSEL element. It is a schematic diagram which shows the manufacturing method of the said VCSEL element. 2 is a cross-sectional view of a VCSEL device according to a second embodiment of the present technology; FIG. 4 is a schematic diagram showing current injection regions and insulating regions of the VCSEL element; FIG.
- FIG. 2 is a cross-sectional view of a VCSEL device having another configuration, according to a second embodiment of the present technology;
- FIG. It is a schematic diagram which shows the positional relationship of the electric current injection area
- 3 is a cross-sectional view of a VCSEL device according to a third embodiment of the present technology;
- FIG. 4 is a schematic diagram showing current injection regions and insulating regions of the VCSEL element;
- the optical axis direction of light emitted from the VCSEL element is the Z direction
- one direction orthogonal to the Z direction is the X direction
- the Z direction and the direction orthogonal to the X direction are the Y direction.
- FIG. 1 is a cross-sectional view of a VCSEL element 100 according to this embodiment
- FIG. 2 is a schematic diagram showing a partial exploded configuration of the VCSEL element 100.
- the VCSEL element 100 includes a first semiconductor layer 101, a second semiconductor layer 102, an active layer 103, a first light reflecting layer 104, a second light reflecting layer 105, a first electrode 106 and a second semiconductor layer 106.
- An electrode 107 is provided.
- the first semiconductor layer 101 , the second semiconductor layer 102 and the active layer 103 are collectively referred to as a laminate 150 .
- Each of these layers has a layer surface direction along the XY plane, and includes a first electrode 106, a first light reflecting layer 104, a first semiconductor layer 101, an active layer 103, a second semiconductor layer 102, and a second electrode 107. and the second light reflecting layer 105 are laminated in this order. Therefore, the laminate 150 is arranged between the first light reflecting layer 104 and the second light reflecting layer 105 .
- the first semiconductor layer 101 is a layer made of a semiconductor having a first conductivity type and transporting carriers to the active layer 103 .
- the first conductivity type can be n-type, and the first semiconductor layer 101 can be, for example, a C-plane n-GaN substrate.
- FIG. 2 is a diagram showing the first semiconductor layer 101 and the first light reflecting layer 104 separated from each other. As shown in the figure, the first semiconductor layer 101 has a first surface 101a on the side of the active layer 103 and a second surface 101b on the side opposite to the active layer 103 .
- a base portion 101c is provided on the second surface 101b side of the first semiconductor layer 101 .
- the base portion 101c is a portion of the second surface 101b that protrudes in a convex curved shape, and has, for example, a spherical lens shape. Further, the shape of the base portion 101c is not limited to a spherical lens shape, and may be any shape as long as the second surface 101b is a convex curved surface.
- the second semiconductor layer 102 is a layer made of a semiconductor having a second conductivity type and transporting carriers to the active layer 103 .
- the second conductivity type can be p-type, and the second semiconductor layer 102 can be made of p-GaN, for example.
- the active layer 103 is arranged between the first semiconductor layer 101 and the second semiconductor layer 102 and is a layer that emits light by carrier recombination.
- the active layer 103 has a multi - quantum well structure in which quantum well layers and barrier layers are alternately laminated . can be made.
- the active layer 103 may be any layer that emits light by carrier recombination.
- the first light reflecting layer 104 reflects light of a specific wavelength (hereinafter referred to as wavelength ⁇ ) and transmits light of other wavelengths.
- the wavelength ⁇ is, for example, 445 nm.
- the first light reflecting layer 104 is a DBR (DBR ( Distributed Bragg Reflector).
- the first light reflecting layer 104 may be a semiconductor DBR made of a semiconductor material, or a dielectric DBR made of a dielectric material.
- the first light reflecting layer 104 has a concave mirror 104c.
- the first light reflecting layer 104 is laminated on the second surface 101b of the first semiconductor layer 101 with a constant thickness, and as shown in FIG.
- the side surface forms a concave surface 104d and the surface opposite to the laminate 150 forms a convex surface 104e.
- the first light reflecting layer 104 forms a concave mirror 104c.
- the diameter D (see FIG. 2) of the concave mirror 104c is 2000 ⁇ m or less
- the radius of curvature (ROC) of the concave surface 104d is 1000 ⁇ m or less
- the surface precision (RMS: Root Mean Square) is 1.0 nm or less. More preferably, the radius of curvature of the concave surface 104d is 100 ⁇ m or less.
- the second light reflecting layer 105 reflects light of wavelength ⁇ and transmits light of other wavelengths.
- the second light reflecting layer 105 is a DBR (DBR) made of a multilayer light reflecting film in which a plurality of high refractive index layers 105a and low refractive index layers 105b each having an optical film thickness of ⁇ /4 are alternately laminated.
- DBR DBR
- the second light reflecting layer 105 may be a semiconductor DBR made of a semiconductor material or a dielectric DBR made of a dielectric material.
- the first electrode 106 is provided around the concave mirror 104 c on the first light reflecting layer 104 and functions as one electrode of the VCSEL element 100 .
- the first electrode 106 can be, for example, a single-layer metal film made of Au, Ni, Ti, or the like, or a multi-layer metal film made of Ti/Au, Ag/Pd, Ni/Au/Pt, or the like.
- the second electrode 107 is arranged between the second semiconductor layer 102 and the second light reflecting layer 105 and functions as the other electrode of the VCSEL element 100 .
- the second electrode 107 can be made of a transparent conductive material such as ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide) or AlMgZnO.
- FIG. 3 is a schematic diagram showing a current confinement structure.
- the current confining structure has a current injection region 121 and an insulating region 122 (dotted regions), as shown in the figure.
- the current injection region 121 is a region into which ions are not implanted (non-ion-implanted region) and has conductivity.
- the insulating region 122 is a region that surrounds the current injection region 121 in the layer surface direction (XY direction), and is a region (ion-implanted region) that is insulated by implanting ions into the semiconductor material forming the laminate 150 . .
- the ions implanted into the insulating region 122 can be B (boron) ions.
- B ions such as O (oxygen) ions and H (hydrogen) ions that can insulate a semiconductor material may also be used.
- the current flowing through the VCSEL element 100 cannot pass through the insulating region 122 and is concentrated in the current injection region 121. That is, the current injection region 121 and the insulating region 122 form a current confinement structure.
- the insulating region 122 may not be provided in all of the first semiconductor layer 101, the active layer 103, and the second semiconductor layer 102, and may be provided in at least one of these layers. Just do it.
- FIG. 4 is a schematic diagram showing the positional relationship between the current injection region 121 and the concave mirror 104c.
- 4A is a view of the current injection region 121 and the concave mirror 104c viewed from the optical axis direction (Z direction) of the laser light emitted from the VCSEL element 100, and FIG. It is a cross-sectional view.
- concave mirror 104c is formed to include current injection region 121 when viewed from the Z direction. Further, the concave mirror 104 c is formed in a concave shape that converges light incident from the active layer 103 side onto the current injection region 121 .
- the plan view of the current injection region 121 viewed from the optical axis direction (Z direction) of the laser beam is the most layer surface of the current injection region 121, as shown in FIG. 4(b). It is a plane figure of a portion where the diameter in the direction (XY direction) is small. Since the diameter of the current injection region 121 increases with increasing distance from the interface between the second semiconductor layer 102 and the second electrode 106, the planar shape of the current injection region 121 is the shape of the current injection region 121 at the same interface.
- FIG. 5 is a schematic diagram showing the operation of the VCSEL element 100.
- FIG. A current flows between the first electrode 106 and the second electrode 107 when a voltage is applied between the first electrode 106 and the second electrode 107 .
- the current is confined by the current confinement structure and injected into the current injection region 121 as indicated by arrow C in FIG.
- This injected current causes spontaneous emission light F near the current injection region 121 of the active layer 103 .
- the spontaneous emission light F travels in the stacking direction (Z direction) of the VCSEL element 100 and is reflected by the first light reflecting layer 104 and the second light reflecting layer 105 .
- the first light reflecting layer 104 and the second light reflecting layer 105 are configured to reflect light having the oscillation wavelength ⁇ , the component of the spontaneous emission light having the oscillation wavelength ⁇ A standing wave is formed between the two light reflecting layers 105 and amplified by the active layer 103 .
- the light forming the standing wave causes lasing.
- the laser light L generated thereby passes through the second light reflecting layer 105 and is emitted from the VCSEL element 100 with the Z direction as the optical axis direction.
- the first light reflecting layer 104 is provided with a concave mirror 104c. Therefore, the light incident on the first light reflecting layer 104 is reflected in a direction corresponding to the shape of the concave mirror 104 c and focused on the current injection region 121 . Therefore, the optical field of the laser light L is controlled by the concave mirror 104c. Also, the current through the VCSEL device 100 is controlled by the current injection region 121 as described above. That is, in VCSEL device 100, the optical field and current are controlled by separate structures.
- contour lines of the concave mirror 104c and the plan figure of the current injection region 121 will be described.
- planar figure refers to contour lines and the shape of the current injection region 121 viewed from the optical axis direction (Z direction) of the laser beam L.
- FIG. 6 is a schematic diagram showing contour lines of the concave mirror 104c.
- 6(a) is a plan view showing a plane figure of contour lines T of the concave mirror 104c
- FIG. 6(b) is a schematic cross-sectional view of a part of the VCSEL element 100.
- FIG. 6B the interface between the first semiconductor layer 101 and the active layer 103 is defined as a reference plane S.
- the contour line T represents the height H of the concave surface 104d from the reference surface S with a line.
- FIG. 7 is a schematic diagram showing an example of a plan figure of contour lines T of the VCSEL element 100. As shown in FIG. 7(a) is a plan view showing a plan figure of contour lines T, and FIG. 7(b) is a schematic cross-sectional view of the VCSEL element 100. FIG. 7(a) is a plan view showing a plan figure of contour lines T, and FIG. 7(b) is a schematic cross-sectional view of the VCSEL element 100.
- FIG. 7 is a schematic diagram showing an example of a plan figure of contour lines T of the VCSEL element 100. As shown in FIG. 7(a) is a plan view showing a plan figure of contour lines T, and FIG. 7(b) is a schematic cross-sectional view of the VCSEL element 100.
- FIG. 7(a) is a plan view showing a plan figure of contour lines T
- FIG. 7(b) is a schematic cross-sectional view of the VCSEL element 100.
- polarized light having the longitudinal direction (X direction) of the ellipse as the polarization direction (hereinafter referred to as longitudinal polarized light) and the lateral direction of the ellipse (Y direction) are
- the polarization direction (hereinafter referred to as short-side polarization) differs in the substantial curvature of the concave mirror 104c. This is because the polarized light is sensitive to the curvature of the concave mirror 104c oriented to match the polarization direction. Therefore, the effective cavity length (the distance between the first light reflecting layer 104 and the second light reflecting layer 105) for each polarized light is different, and the resonant wavelength is different between longitudinally polarized light and transversely polarized light.
- the wavelength overlap between the longitudinally polarized light and the transversely polarized light is weakened, and the longitudinally polarized light and the transversely polarized light are stabilized.
- the wavelengths of the longitudinally polarized light and the transversely polarized light are the same, energy is easily exchanged between the two, and if the wavelengths are different, the energy is difficult to exchange.
- the plane figure of the contour line T is elliptical, the polarization controllability is improved compared to the case where the plane figure is a perfect circle.
- the plane figure of the contour line T is not limited to an ellipse, and may be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these, as will be described later. Of these, if the plane figure of the contour line T has a shape other than a perfect circle, the polarization controllability can be improved according to the principle described above.
- FIG. 8 is a schematic diagram showing another example of the plan figure of the current injection region 121 of the VCSEL element 100. As shown in FIG. 8A is a plan view showing a plan figure of the current injection region 121, and FIG. 8B is a schematic cross-sectional view of the VCSEL element 100. FIG. 8A
- the current injection region 121 when the plane figure of the current injection region 121 is elliptical, the current injected from the second electrode 106 to the central portion of the current injection region 121 increases. Since the second electrode 106 has a certain film resistance, the current tends to flow into the outer periphery of the current injection region 121. However, when the plan shape of the current injection region 121 is elliptical, the current is more likely to flow than when the plan shape of the current injection region 121 is a perfect circle. This is because the periphery of the injection region 121 in the lateral direction (X direction) approaches the central portion.
- the fundamental transverse mode is a profile of the beam profile (irradiation spot shape) of the laser light L, in which the amount of light is the largest in the central portion and the amount of light gradually decreases along the peripheral portion.
- the plan figure of the current injection region 121 is not limited to an ellipse, and may be a circle, an ellipse, a rectangle, or a closed figure consisting of a combination of at least two of these, as will be described later. Of these, if the plane figure of the current injection region 121 is a shape other than a perfect circle, the fundamental transverse mode can be easily stabilized according to the principle described above.
- the plan figure (first figure) of the current injection region 121 and the plan figure (second figure) of the contour line T of the concave mirror 104c have one of the following relationships.
- 9 to 23 are schematic diagrams showing examples of the plan figures of the current injection region 121 and the plan figures of the contour lines T.
- the plan figure of the current injection region 121 and the plan figure of the contour line T may be dissimilar.
- the planar figure of the current injection region 121 can be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these.
- the plan figure of the contour line T may be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these, and may be a figure dissimilar to the plan figure of the current injection region 121 .
- Either one of the plan figure of the current injection region 121 and the plan figure of the contour line T may be a perfect circle.
- center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T can be made to coincide.
- a specific example of the plan figure of the current injection region 121 and the plan figure of the contour line T when the plan figure of the current injection region 121 and the plan figure of the contour line T are not similar will be given below.
- the plan figure of the current injection region 121 is a perfect circle
- the plan figure of the contour line T can be an ellipse with the X direction as the longitudinal direction.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a perfect circle with a diameter of 5 ⁇ m
- the plan figure of the contour line T can be, for example, an ellipse with a ratio of longitudinal diameter to transverse diameter of 5:2.
- the plan figure of the current injection region 121 can be a rounded rectangle whose longitudinal direction is the X direction, and the plan figure of the contour line T can be an ellipse whose longitudinal direction is the X direction. .
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a rounded rectangle with a long side of 5 ⁇ m and a short side of 3 ⁇ m
- the plan figure of the contour line T is, for example, an ellipse with a ratio of longitudinal diameter to short side diameter of 5:2.
- the plan figure of the current injection region 121 is a rectangle having semicircular ends whose longitudinal direction is the X direction, and the plan figure of the contour line T is an ellipse whose longitudinal direction is the X direction. can do.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a shape with a width of 5 ⁇ m in the longitudinal direction and a width of 2 ⁇ m in the transverse direction
- the plan figure of the contour line T is, for example, an ellipse with a ratio of longitudinal diameter: transverse diameter of 5:2. can be shaped.
- the plane figure of the current injection region 121 is a rectangle having semicircular ends whose longitudinal direction is the direction between the X direction and the Y direction, and the plane figure of the contour line T is the X direction. can be an elliptical shape with .
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a shape with a width of 5 ⁇ m in the longitudinal direction and a width of 2 ⁇ m in the transverse direction
- the plan figure of the contour line T is, for example, an ellipse with a ratio of longitudinal diameter: transverse diameter of 5:2. can be shaped.
- the plan figure of the current injection region 121 can be a rounded triangle, and the plan figure of the contour line T can be an ellipse with the X direction as the longitudinal direction.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a triangle with rounded corners of 5 ⁇ m on each side, and the plan figure of the contour line T can be, for example, an ellipse with a ratio of longitudinal diameter to transverse diameter of 5:2. can.
- the plan figure of the current injection region 121 is a combination of a rectangle with rounded corners and an ellipse
- the plan figure of the contour line T can be an ellipse with the X direction as the longitudinal direction.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a shape with a long side of 5 ⁇ m and a short side of 3 ⁇ m
- the plan figure of the contour line T is, for example, an ellipse with a ratio of the longitudinal diameter to the transverse diameter of 5:2. be able to.
- the plan figure of the current injection region 121 is a combination of two rectangles with rounded corners, and the plan figure of the contour line T can be an ellipse with the X direction as the longitudinal direction.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, a shape with a long side of 5 ⁇ m and a short side of 3 ⁇ m
- the plan figure of the contour line T is, for example, an ellipse with a ratio of the longitudinal diameter to the transverse diameter of 5:2. be able to.
- the plan figure of the current injection region 121 is an ellipse with the Y direction as the longitudinal direction, and the plan figure of the contour line T can be a perfect circle.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, an ellipse with a width of 5 ⁇ m in the longitudinal direction and a width of 3 ⁇ m in the lateral direction.
- the plan figure of the current injection region 121 and the plan figure of the contour line T may be dissimilar. Both the plan figure of the current injection region 121 and the plan figure of the contour line T are not limited to those described above, and may be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these, as long as they are not similar. good.
- the gain of polarized light having a specific polarization direction is improved. This is because the actual curvature of the concave mirror 104c differs depending on the polarization direction, and the degree of passing through the region of the current injection region 121 where the injected current is large differs, so that the gain received from the injected current differs depending on the polarization direction. . This stabilizes the polarized light whose polarization direction is in a specific direction, so that the controllability of the polarized light of the VCSEL element 100 can be improved.
- plan figure of the current injection region 121 and the plan figure of the contour line T may be similar and not perfect circles.
- the planar figure of the current injection region 121 can be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these, and not a perfect circle.
- the plan figure of the contour line T may be a circle, an ellipse, a rectangle, or a closed figure consisting of a combination of at least two of these, not a perfect circle, but similar to the plan figure of the current injection region 121.
- center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T can be made to coincide.
- Specific examples of the plan view of the current injection region 121 and the contour lines T when the plan view of the current injection region 121 and the contour lines T are similar but not circular will be given below.
- the plan figure of the current injection region 121 is an ellipse with the X direction as the longitudinal direction, and the plan figure of the contour line T can be an ellipse similar to the plan figure of the current injection region 121. can.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plan figure of the current injection region 121 can be, for example, an ellipse with a longitudinal diameter of 5 ⁇ m and a transverse diameter of 2 ⁇ m. It can be oval.
- the plan figure of the current injection region 121 is a rectangle with semicircular ends extending in the X direction, and the plan figure of the contour line T is similar to the plan figure of the current injection region 121 . It can be rectangular with some semi-circular ends.
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plane figure of the current injection region 121 can have, for example, a shape with a width of 5 ⁇ m in the longitudinal direction and a width of 2 ⁇ m in the lateral direction
- the plan figure of the contour line T can have a shape with a width in the longitudinal direction: width in the lateral direction of 5:2, for example. can be
- the plan figure of the current injection region 121 is a rounded triangle
- the plan figure of the contour line T can be a rounded triangle similar to the plan figure of the current injection region 121 .
- the center of gravity of the plan figure of the current injection region 121 and the center of gravity of the plan figure of the contour line T coincide with each other.
- the plane figure of the current injection region 121 can be, for example, a rounded triangle with each side of 5 ⁇ m.
- plan figure of the current injection region 121 and the plan figure of the contour line T may be similar and not perfectly circular. Both the plan figure of the current injection region 121 and the plan figure of the contour line T are not limited to those described above. .
- the effective curvature of the concave mirror 104c differs depending on the polarization direction. have different resonance wavelengths. Therefore, the wavelength overlap between the respective polarized light is weakened, and the respective polarized lights are stabilized.
- the plan shape of the current injection region 121 is not a perfect circle, the periphery of the current injection region 121 approaches the center, so that the current injected from the second electrode 106 to the center of the current injection region 121 increases. , the fundamental transverse mode becomes easier to stabilize.
- the plan figure of the contour line T and the plan figure of the current injection region 121 are similar, the effect of improving the stability of the polarization and the effect of improving the stability of the fundamental transverse mode are superimposed. It is possible to improve the controllability of polarization.
- the center of gravity of the plan figure of the current injection region 121 and the plan figure of the contour line T can be different.
- the planar figure of the current injection region 121 can be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these.
- the plan figure of the contour line T can be a circle, an ellipse, a rectangle, or a closed figure consisting of a combination of at least two of these, and the center of gravity can be different from the plan figure of the current injection region 121 .
- the distance between the center of gravity of the plan figure of the current injection region 121 and the plan figure of the contour line T on the plane (XY plane) perpendicular to the optical axis direction (Z direction) is preferably 0.03 ⁇ m or more.
- the plan figure of the current injection region 121 and the plan figure of the contour line T may or may not be similar.
- a specific example of the plan view of the current injection region 121 and the plan view of the contour lines T when the center of gravity of the plan view of the current injection region 121 and the plan view of the contour lines T is different will be given below.
- the plan figure of the current injection region 121 is a perfect circle, and the plan figure of the contour line T can also be a perfect circle.
- the center of gravity P1 of the plan figure of the current injection region 121 and the center of gravity P2 of the plan figure of the contour line T are different in the Y direction.
- the plane figure of the current injection region 121 can be, for example, a perfect circle with a diameter of 4 ⁇ m.
- the distance (Y direction) between the center of gravity P1 and the center of gravity P2 can be set to 0.5 ⁇ m, for example.
- the plan figure of the current injection region 121 is an ellipse with the X direction as the longitudinal direction
- the plan figure of the contour line T can be an ellipse with the X direction as the longitudinal direction.
- the center of gravity P1 of the plan figure of the current injection region 121 and the center of gravity P2 of the plan figure of the contour line T are different in the longitudinal direction (X direction).
- the plan figure of the current injection region 121 can be, for example, an ellipse with a longitudinal diameter of 8 ⁇ m and a transverse diameter of 4 ⁇ m. It can be oval.
- the distance (X direction) between the center of gravity P1 and the center of gravity P2 can be set to 0.5 ⁇ m, for example.
- the plan figure of the current injection region 121 is an ellipse with the X direction as the longitudinal direction
- the plan figure of the contour line T can be an ellipse with the X direction as the longitudinal direction.
- the center of gravity P1 of the plan figure of the current injection region 121 and the center of gravity P2 of the plan figure of the contour line T are different in the lateral direction (Y direction).
- the plan figure of the current injection region 121 can be, for example, an ellipse with a longitudinal diameter of 8 ⁇ m and a transverse diameter of 4 ⁇ m. It can be oval.
- the distance (Y direction) between the center of gravity P1 and the center of gravity P2 can be set to 0.5 ⁇ m, for example.
- the plan figure of the current injection region 121 is an ellipse with the X direction as the longitudinal direction
- the plan figure of the contour line T can be a perfect circle.
- the center of gravity P1 of the plan figure of the current injection region 121 and the center of gravity P2 of the plan figure of the contour line T are different in the longitudinal direction (X direction) and lateral direction (Y direction) of the current injection region 121 .
- the plan figure of the current injection region 121 can be, for example, a perfect circle with a diameter of 4 ⁇ m
- the plan figure of the contour line T can be, for example, an ellipse with a ratio of longitudinal diameter to transverse diameter of 5:2.
- the distance (XY direction) between the center of gravity P1 and the center of gravity P2 can be set to 0.5 ⁇ m, for example.
- the center of gravity of the plane figure of the current injection region 121 and the plane figure of the contour line T can be different.
- Both the plan figure of the current injection region 121 and the plan figure of the contour line T are not limited to those described above, and may be a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of these.
- the gain of polarized light having a specific polarization direction is improved. This is because the center of gravity of the two plan figures differs, and the degree of passing through the region of the current injection region 121 where the injected current is large differs depending on the polarization direction, so the gain received from the injected current differs depending on the polarization direction. . This stabilizes the polarized light whose polarization direction is in a specific direction, so that the controllability of the polarized light of the VCSEL element 100 can be improved.
- the plane figure of the current injection region 121 and the plane figure of the contour line T have any one of the above relationships, so that lateral (XY direction) asymmetry with respect to light and current can be provided to improve the controllability of the polarization of the VCSEL element 100 . Since the VCSEL element 100 does not use crystal asymmetry for polarization control, it is possible to fabricate the VCSEL element 100 using a substrate (such as a C-plane substrate) having no crystal asymmetry.
- FIG. 24 to 26 are schematic diagrams showing the manufacturing method of the VCSEL element 100.
- FIG. First as shown in FIG. 24, a laminate 150 is produced.
- the laminate 150 can be produced by laminating the active layer 103 and the second semiconductor layer 102 on the first semiconductor layer 101 (substrate).
- the active layer 103 and the second semiconductor layer 102 can be laminated by a metal organic-chemical vapor deposition (MOCVD) method or the like.
- MOCVD metal organic-chemical vapor deposition
- insulating regions 122 are formed.
- the insulating region 122 can be formed by implanting ions into the stacked body 150 from the second semiconductor layer 102 side.
- the current injection region 121 which is a region into which ions are not implanted, can be formed.
- the base 101c is formed on the second surface 101b of the first semiconductor layer 101. Then, as shown in FIG. Specifically, after polishing the second surface 101b, a patterned resist layer is formed on the second surface 101b, and the resist layer is heated and reflowed to obtain a resist pattern.
- the resist pattern is made to have the same shape (or similar shape) as the base portion 101c.
- the base 101c can be formed by etching the rest pattern and the second surface 101b. This etching can be, for example, reactive ion etching (RIE).
- the first light reflecting layer 104, the second light reflecting layer 105, the first electrode 106, and the second electrode 107 are formed respectively, and the VCSEL element 100 shown in FIG. 1 can be manufactured.
- Each of these layers can be formed by a sputtering method, a vacuum deposition method, or the like.
- the VCSEL element 100 can be manufactured as described above. It should be noted that the method for manufacturing the VCSEL element 100 is not limited to the one shown here, and it is also possible to manufacture the VCSEL element 100 by other manufacturing methods.
- the interface between the first semiconductor layer 101 and the active layer 103 is defined as a reference plane S
- the contour line T of the concave mirror 104c is a line representing the height of the concave surface 104d from the reference plane S (see FIG. 6).
- a line representing the height of the convex surface 104e from the surface S may be used as the contour line T.
- the reference plane S may be the interface between the second electrode 107 and the second light reflecting layer 105 instead of the interface between the first semiconductor layer 101 and the active layer 103 .
- the concave mirror 104c is laminated on the base portion 101c provided in the first semiconductor layer 101 and is formed in a concave mirror shape, it is not limited to this.
- a structure made of a dielectric material, a synthetic resin, or the like and having the same shape as the base portion 101c is provided. 104c may be formed.
- the first semiconductor layer 101 is made of an n-type semiconductor material and the second semiconductor layer 102 is made of a p-type semiconductor material
- the first semiconductor layer 101 is made of a p-type semiconductor material
- the second semiconductor layer 102 is made of a p-type semiconductor material.
- the VCSEL element 100 may also have other configurations that enable the operation of the VCSEL element 100 described above.
- VCSEL Very Cavity Surface Emitting Laser
- FIG. 27 is a cross-sectional view of a VCSEL element 200 according to this embodiment.
- the VCSEL device 200 includes a substrate 201, a first semiconductor layer 202, a second semiconductor layer 203, a third semiconductor layer 204, an active layer 205, a tunnel junction layer 206, a first light reflecting layer 207, a It comprises two light reflecting layers 208 , a first electrode 209 , a second electrode 210 and an insulating film 211 .
- the first semiconductor layer 202 , the second semiconductor layer 203 , the third semiconductor layer 204 , the active layer 205 and the tunnel junction layer 206 are collectively referred to as a laminate 250 .
- Each of these layers has a layer surface direction along the XY plane, and includes a first light reflecting layer 207, a substrate 201, a first semiconductor layer 202, an active layer 205, a second semiconductor layer 203, a third semiconductor layer 204,
- the layers are stacked in the order of the second light reflecting layer 208 . Therefore, the stack 250 is arranged between the first light reflecting layer 207 and the second light reflecting layer 208 .
- a substrate 201 supports each layer of the VCSEL element 200 .
- Substrate 201 can be, for example, a (101) plane semi-insulating InP substrate.
- the substrate 201 has a first surface 201a on the side of the active layer 205 and a second surface 201b opposite to the active layer 205.
- a base portion 201c is provided on the second surface 101b side of the substrate 201 .
- the base portion 201c is a portion of the second surface 201b that protrudes in a convex curved shape, and has, for example, a spherical lens shape.
- the shape of the base portion 201c is not limited to a spherical lens shape, and may be any shape as long as the second surface 201b is a convex curved surface.
- the first semiconductor layer 202 is a layer made of a semiconductor having a first conductivity type and transporting carriers to the active layer 205 .
- the first conductivity type can be n-type, and the first semiconductor layer 202 can be a layer made of n-InP, for example.
- the second semiconductor layer 203 is made of a semiconductor of the second conductivity type and transports carriers to the active layer 205 .
- the second conductivity type can be p-type, and the second semiconductor layer 203 can be a layer made of p-InP, for example.
- the third semiconductor layer 204 is a layer made of a semiconductor having the first conductivity type and transporting carriers to the tunnel junction layer 206 .
- the third semiconductor layer 204 can be, for example, a layer made of n-InP.
- the active layer 205 is arranged between the first semiconductor layer 202 and the second semiconductor layer 203 and is a layer that emits light by carrier recombination.
- the active layer 205 has a multi-quantum well structure in which multiple layers of quantum well layers and barrier layers are alternately laminated.
- the quantum well layers are made of, for example, InGaAsP
- the barrier layers are made of, for example, InGaAsP having a composition different from that of the quantum well layers. can be made.
- the active layer 205 may be any layer that emits light by carrier recombination.
- Tunnel junction layer 206 forms a buried tunnel junction.
- the tunnel junction layer 206 is arranged between the central portion of the second semiconductor layer 203 and the central portion of the third semiconductor layer 204 .
- the tunnel junction layer 206 has a first layer 206a on the second semiconductor layer 203 side and a second layer 206b on the third semiconductor layer 204 side.
- the first layer 206a is a layer of the second conductivity type with a high impurity concentration, and can be made of, for example, p + -AlInGaAs.
- the second layer 206b is a layer of the first conductivity type with a high impurity concentration, and can be made of, for example, n + -InP.
- the active layer 205, the second semiconductor layer 203 and the third semiconductor layer 204 are removed at their outer peripheral portions to form a mesa (plateau structure) M.
- the tunnel junction layer 206 is arranged so as to be positioned in the center of the mesa M when viewed in the Z direction.
- the first light reflecting layer 207 reflects light of a specific wavelength (hereinafter referred to as wavelength ⁇ ) and transmits light of other wavelengths.
- the wavelength ⁇ is, for example, a specific wavelength within 1300-1600 nm.
- the first light reflecting layer 207 is a DBR (DBR) made of a multilayer light reflecting film in which a plurality of high refractive index layers 207a and low refractive index layers 207b each having an optical film thickness of ⁇ /4 are alternately laminated.
- DBR DBR
- the second light reflecting layer 207 may be a semiconductor DBR made of a semiconductor material, or a dielectric DBR made of a dielectric material.
- the first light reflecting layer 207 has a concave mirror 207c.
- the first light reflecting layer 207 is laminated on the second surface 201b of the substrate 201 with a constant thickness, and the surface on the side of the laminate 250 forms a concave surface 207d according to the shape of the base 201c provided on the second surface 201b, The surface opposite the laminate 250 forms a convex surface 207e. Thereby, the first light reflecting layer 207 forms a concave mirror 207c.
- the concave mirror 207c preferably has a radius of curvature (ROC) of 1000 ⁇ m or less and a root mean square (RMS) of 1 nm or less. may have a radius of curvature of 400 ⁇ m.
- ROC radius of curvature
- RMS root mean square
- the second light reflecting layer 208 reflects light of wavelength ⁇ and transmits light of other wavelengths.
- the second light reflecting layer 208 is a DBR (DBR) made of a multilayer light reflecting film in which a plurality of high refractive index layers 208a and low refractive index layers 208b each having an optical film thickness of ⁇ /4 are alternately laminated.
- DBR DBR
- the second light reflecting layer 208 may be a semiconductor DBR made of a semiconductor material or a dielectric DBR made of a dielectric material.
- the first electrode 209 is provided around the mesa M on the first semiconductor layer 202 and functions as one electrode of the VCSEL element 200 .
- the first electrode 209 can be, for example, a single-layer metal film made of Au, Ni, or Ti, or a multi-layer metal film made of Ti/Au, Ag/Pd, Ni/Au/Pt, or the like.
- the second electrode 210 is provided around the second light reflecting layer 208 on the third semiconductor layer 204 and functions as the other electrode of the VCSEL element 200 .
- the second electrode 210 can be, for example, a single-layer metal film made of Au, Ni, or Ti, or a multi-layer metal film made of Ti/Au, Ag/Pd, Ni/Au/Pt, or the like.
- the insulating film 211 is provided around the second electrode 210 on the side surface of the mesa M and the upper surface of the mesa M, and insulates the outer circumference of the mesa M. As shown in FIG.
- the insulating film 211 is made of any insulating material.
- FIG. 28 is a schematic diagram showing a current confinement structure.
- the current confinement structure has a current injection region 221 and an insulating region 222, as shown in the figure.
- a current injection region 221 is a region (tunnel junction region) in which a tunnel junction is formed by the tunnel junction layer 206, and current is passed through the tunnel junction.
- the insulating region 222 surrounds the current injection region 221 in the layer surface direction (XY direction) and is a region (non-tunnel junction region) that does not pass current because no tunnel junction is formed.
- the current flowing through the VCSEL element 200 concentrates in the current injection region 221 because it cannot pass through the insulating region 222 . That is, the current injection region 221 and the insulating region 222 form a current confinement structure.
- FIG. 29 is a schematic diagram showing the positional relationship between the current injection region 221 and the concave mirror 207c.
- 29(a) is a view of the current injection region 221 and the concave mirror 207c viewed from the optical axis direction (Z direction) of the laser light emitted from the VCSEL element 200
- FIG. 29(b) is a schematic of the VCSEL element 200. It is a cross-sectional view.
- the concave mirror 207c is formed so as to include the current injection region 221 when viewed from the Z direction. Further, the concave mirror 207c is formed in a concave shape that converges the light incident from the active layer 205 side onto the current injection region 221. As shown in FIG.
- the VCSEL device 200 operates similarly to the VCSEL device 100 according to the first embodiment. That is, when a voltage is applied between the first electrode 209 and the second electrode 210 , current flows between the first electrode 209 and the second electrode 210 . The current is confined by the current confinement structure and injected into the current injection region 221 . The spontaneous emission light generated by this injected current is reflected by the first light reflecting layer 207 and the second light reflecting layer 208 to generate laser oscillation. The laser light generated thereby passes through the second light reflecting layer 208 and is emitted from the VCSEL element 200 with the Z direction as the optical axis direction.
- the first light reflecting layer 207 is provided with a concave mirror 207c. Therefore, the light incident on the second light reflecting layer 207 is reflected in a direction corresponding to the shape of the concave mirror 207 c and focused on the current injection region 221 . Therefore, the optical field of the laser light is controlled by the concave mirror 207c. Also, the current through the VCSEL device 200 is controlled by the current injection region 221 as described above. That is, in the VCSEL device 200, the optical field and current are controlled by separate structures.
- contour lines of the concave mirror 207c and the plan figure of the current injection region 221 will be described.
- planar figure refers to contour lines and the shape of the current injection region 221 viewed from the optical axis direction (Z direction) of the laser beam.
- FIG. 30 is a schematic diagram showing contour lines of the concave mirror 207c.
- 30(a) is a plan view showing a plane figure of contour lines T of the concave mirror 207c
- FIG. 30(b) is a schematic cross-sectional view of part of the VCSEL element 200.
- FIG. 30B the interface between the first semiconductor layer 202 and the active layer 205 is defined as a reference plane S.
- the contour line T represents the height H of the concave surface 207d from the reference plane S with a line.
- the relationship between the plan figure (first figure) of the current injection region 221 and the plan figure (second figure) of the contour line T is the same as in the first embodiment. That is, the plan figure of the current injection region 221 and the plan figure of the contour line T can be dissimilar (see FIGS. 9 to 16). Also, the plan figure of the current injection region 221 and the plan figure of the contour line T may be similar and not perfect circles (see FIGS. 17 to 19). Furthermore, the center of gravity of the plan figure of the current injection region 221 and the plan figure of the contour line T can be different (see FIGS. 20 to 23). As described in the first embodiment, it is possible to improve the controllability of the polarization of the VCSEL element 200 by adopting such a configuration.
- the plane figure of the current injection region 221 and the plane figure of the contour line T have one of the above relationships, thereby providing lateral (XY direction) asymmetry with respect to light and current, It is possible to improve the controllability of the polarization of the VCSEL element 200 .
- the first layer 206a and the second layer 206b are removed by photolithography and etching. A portion is removed to form the tunnel junction layer 206 .
- the shape of the tunnel junction layer 206 can be freely controlled by photolithography.
- a third semiconductor layer 204 is laminated on the tunnel junction layer 206, and a mesa M is formed by photolithography and etching. Thereby, a laminate 250 is formed on the substrate 201 .
- the VCSEL element 200 can be manufactured by providing the base portion 201c on the substrate 201 and laminating the first light reflecting layer 207, the second light reflecting layer 208, and the like by the same method as in the first embodiment. VCSEL device 200 can also be manufactured by other manufacturing methods.
- the current confinement structure is provided by the embedded tunnel junction of the tunnel junction layer 206.
- the current confinement structure may be provided by ion implantation into the tunnel junction layer 206 as follows. It is possible.
- FIG. 31 is a cross-sectional view of a VCSEL device 200 having insulating regions 223 formed by ion implantation.
- the tunnel junction layer 206 is disposed entirely between the second semiconductor layer 203 and the third semiconductor layer 204, and the peripheral region of the tunnel junction layer 206 includes an insulating region 223 (dotted region). ) is provided.
- FIG. 32 is a schematic diagram showing a current confinement structure in this configuration.
- the current confinement structure is composed of a current injection region 221 and an insulating region 223, as shown in the figure.
- the current injection region 221 is formed by the tunnel junction layer 206 into which ions are not implanted.
- the insulating region 223 surrounds the current injection region 221 in the layer plane direction (XY direction) and is a region insulated by implanting ions into the tunnel junction layer 206 .
- the ions implanted into the ion implantation region can be B (boron) ions.
- ions such as O (oxygen) ions and H (hydrogen) ions that can insulate a semiconductor material may also be used.
- the current flowing through the VCSEL element 200 concentrates in the current injection region 221 because it cannot pass through the insulating region 223 . That is, the current injection region 221 and the insulating region 223 form a current confinement structure.
- the laminated body 250 is laminated on the substrate 201 to fabricate the VCSEL element 200.
- the laminated body 250 is laminated on another supporting substrate, the supporting substrate is removed, and the laminated body 250 is used as the substrate.
- 201 may be joined.
- the substrate 201 can be, for example, a semi-insulating Si substrate.
- the interface between the first semiconductor layer 202 and the active layer 205 is defined as a reference plane S
- the contour line T of the concave mirror 207c is a line representing the height of the concave surface 207d from the reference plane S.
- the contour line T may be a line representing the height of the convex surface 207e of .
- the reference surface S may be the interface between the third semiconductor layer 204 and the second light reflecting layer 208 instead of the interface between the first semiconductor layer 202 and the active layer 205 .
- the concave mirror 207c is laminated on the base portion 201c provided on the substrate 201 and formed in a concave mirror shape, but it is not limited to this.
- a structure made of a dielectric material, a synthetic resin, or the like and having the same shape as the base 201c is provided, and a concave mirror 207c is formed on the first light reflecting layer 207 by this structure. You may
- the first semiconductor layer 202 and the third semiconductor layer 204 are made of an n-type semiconductor material
- the second semiconductor layer 203 is made of a p-type semiconductor material. It may be made of a p-type semiconductor material and the second semiconductor layer 203 may be made of an n-type semiconductor material.
- the first layer 206a of the tunnel junction layer 206 can be an n-type layer with a high impurity concentration
- the second layer 206b can be a p-type layer with a high impurity concentration.
- the VCSEL element 200 may have other configurations that enable the operation of the VCSEL element 200 to be implemented.
- a VCSEL (Vertical Cavity Surface Emitting Laser) device according to a third embodiment of the present technology will be described.
- the VCSEL element according to this embodiment differs from the VCSEL element according to the first embodiment mainly in the current confinement structure.
- FIG. 33 is a cross-sectional view of a VCSEL element 300 according to this embodiment.
- the VCSEL element 300 includes a substrate 301, a first semiconductor layer 302, a second semiconductor layer 303, an active layer 304, an oxidized constricting layer 305, a first light reflecting layer 306, a second light reflecting layer 307, A first electrode 308 , a second electrode 309 and an insulating film 310 are provided.
- the first semiconductor layer 302 , the second semiconductor layer 303 , the active layer 304 and the oxidized constricting layer 305 are collectively referred to as a laminate 350 .
- Each of these layers has a layer plane direction along the XY plane, and includes a first light reflecting layer 306, a substrate 301, a first semiconductor layer 302, an active layer 304, a second semiconductor layer 303, an oxidized constricting layer 305, a
- the two light reflecting layers 307 are laminated in this order. Therefore, the stack 350 is arranged between the first light reflecting layer 306 and the second light reflecting layer 307 .
- a substrate 301 supports each layer of the VCSEL element 300 .
- Substrate 301 can be, for example, a (101) plane semi-insulating GaAs substrate.
- the substrate 301 has a first surface 301a on the side of the active layer 304 and a second surface 301b opposite to the active layer 304.
- a base portion 301c is provided on the second surface 301b side of the substrate 301 .
- the base portion 301c is a portion of the second surface 301b that protrudes in a convex curved shape, and has, for example, a spherical lens shape.
- the shape of the base portion 301c is not limited to a spherical lens shape, and may be any shape as long as the second surface 301b is a convex curved surface.
- the first semiconductor layer 302 is a layer made of a semiconductor having a first conductivity type and transporting carriers to the active layer 304 .
- the first conductivity type can be n-type, and the first semiconductor layer 302 can be a layer made of n-GaAs, for example.
- the second semiconductor layer 303 is made of a semiconductor of the second conductivity type and transports carriers to the active layer 304 .
- the second conductivity type can be p-type, and the second semiconductor layer 303 can be a layer made of p-GaAs, for example.
- the active layer 304 is arranged between the first semiconductor layer 302 and the second semiconductor layer 303 and is a layer that emits light by carrier recombination.
- the active layer 304 has a multi-quantum well structure in which quantum well layers and barrier layers are alternately laminated.
- the quantum well layers can be made of GaAs, and the barrier layers can be made of AlGaAs.
- the active layer 304 may be any layer that emits light by carrier recombination.
- the oxidized confinement layer 305 forms a current confinement structure.
- the oxidized constricting layer 305 has an unoxidized region 305a where the semiconductor material is not oxidized and an oxidized region 305b where the semiconductor material is oxidized.
- the non-oxidized region 305a is made of a material of the second conductivity type with a high impurity concentration, such as p + -AlAs.
- the oxidized region 305b is made of a material obtained by oxidizing the constituent material of the non-oxidized region 305a, and can be made of AlAs oxide, for example.
- the first light reflecting layer 306 reflects light of a specific wavelength (hereinafter referred to as wavelength ⁇ ) and transmits light of other wavelengths.
- the wavelength ⁇ is, for example, a specific wavelength within the range of 850-1400 nm.
- the first light reflecting layer 306 is a DBR (DBR) made of a multilayer light reflecting film in which a plurality of high refractive index layers 306a and low refractive index layers 306b each having an optical film thickness of ⁇ /4 are alternately laminated.
- DBR DBR
- the first light reflecting layer 306 may be a semiconductor DBR made of a semiconductor material, or a dielectric DBR made of a dielectric material.
- the first light reflecting layer 306 has a concave mirror 306c.
- the first light reflecting layer 306 is laminated with a constant thickness on the second surface 301b of the substrate 301, and the surface on the side of the laminate 350 forms a concave surface 306d according to the shape of the base portion 301c provided on the second surface 301b, The surface opposite the laminate 350 forms a convex surface 306e.
- the first light reflecting layer 306 thereby forms a concave mirror 306c.
- the concave mirror 306c preferably has a radius of curvature (ROC) of 1000 ⁇ m or less and a root mean square (RMS) of 1 nm or less. may have a radius of curvature of 400 ⁇ m.
- ROC radius of curvature
- RMS root mean square
- the second light reflecting layer 307 reflects light of wavelength ⁇ and transmits light of other wavelengths.
- the second light-reflecting layer 307 is a DBR (DBR ( Distributed Bragg Reflector).
- the second light reflective layer 307 can be a semiconductor DBR made of a semiconductor material.
- the active layer 304, the second semiconductor layer 303, the oxidized constricting layer 305 and the second light reflecting layer 307 are removed at their outer peripheral portions to form a mesa (plateau structure) M.
- a first electrode 308 is provided around the mesa M on the first semiconductor layer 302 and functions as one electrode of the VCSEL element 300 .
- the first electrode 308 can be, for example, a single-layer metal film made of Au, Ni, Ti, or the like, or a multi-layer metal film made of Ti/Au, Ag/Pd, Ni/Au/Pt, or the like.
- a second electrode 309 is provided on the second light reflecting layer 307 and functions as the other electrode of the VCSEL element 300 .
- the second electrode 309 can be, for example, a single-layer metal film made of Au, Ni, or Ti, or a multi-layer metal film made of Ti/Au, Ag/Pd, Ni/Au/Pt, or the like.
- the insulating film 310 is provided around the second electrode 309 on the side surface of the mesa M and the upper surface of the mesa M, and insulates the outer periphery of the mesa M.
- the insulating film 310 is made of any insulating material.
- FIG. 34 is a schematic diagram showing a current confinement structure.
- the current confining structure has a current injection region 321 and an insulating region 322 as shown in the figure.
- the current injection region 321 is a region having conductivity due to the non-oxidized region 305a.
- the insulating region 322 surrounds the current injection region 221 in the layer plane direction (XY direction) and is a region that does not have conductivity due to the oxidized region 305b that is insulated by oxidation.
- the current flowing through the VCSEL element 300 concentrates in the current injection region 321 because it cannot pass through the insulating region 322 . That is, in the VCSEL element 300, the current confinement structure is formed by the oxidized confinement layer 305. FIG.
- FIG. 35 is a schematic diagram showing the positional relationship between the current injection region 321 and the concave mirror 306c.
- 35(a) is a diagram of the current injection region 321 and the concave mirror 306c viewed from the optical axis direction (Z direction) of the laser light emitted from the VCSEL element 300
- FIG. 35(b) is a schematic diagram of the VCSEL element 300. It is a cross-sectional view.
- the concave mirror 306c is formed so as to include the current injection region 321 when viewed from the Z direction.
- the concave mirror 306c is formed in a concave shape that converges light incident from the active layer 304 side onto the current injection region 321. As shown in FIG.
- the VCSEL device 300 operates similarly to the VCSEL device 300 according to the first embodiment. That is, when a voltage is applied between the first electrode 308 and the second electrode 309 , current flows between the first electrode 308 and the second electrode 309 . A current is confined by the current confinement structure and injected into the current injection region 321 . The spontaneous emission light generated by this injected current is reflected by the first light reflecting layer 306 and the second light reflecting layer 307 to generate laser oscillation. The laser light generated thereby passes through the second light reflecting layer 307 and is emitted from the VCSEL element 300 with the Z direction as the optical axis direction.
- the first light reflecting layer 306 is provided with a concave mirror 306c. Therefore, the light incident on the second light reflecting layer 306 is reflected in a direction corresponding to the shape of the concave mirror 306 c and focused on the current injection region 321 . Therefore, the optical field of the laser light is controlled by the concave mirror 306c. Also, the current through the VCSEL device 300 is controlled by the current injection region 321 as described above. That is, in VCSEL device 300, the optical field and current are controlled by separate structures.
- contour lines of the concave mirror 306c and the plan figure of the current injection region 321 will be described.
- planar figure refers to contour lines and the shape of the current injection region 321 viewed from the optical axis direction (Z direction) of the laser beam.
- FIG. 36 is a schematic diagram showing contour lines of the concave mirror 306c.
- 36(a) is a plan view showing a plane figure of contour lines T of the concave mirror 306c
- FIG. 36(b) is a schematic cross-sectional view of a portion of the VCSEL element 300.
- FIG. 36B the interface between the first semiconductor layer 302 and the active layer 304 is defined as a reference plane S.
- the contour line T represents the height H of the concave surface 306d from the reference surface S with a line.
- the relationship between the plan figure (first figure) of the current injection region 321 and the plan figure (second figure) of the contour line T is the same as in the first embodiment. That is, the plan figure of the current injection region 321 and the plan figure of the contour line T can be dissimilar (see FIGS. 9 to 16). Also, the plan figure of the current injection region 321 and the plan figure of the contour line T may be similar and not perfect circles (see FIGS. 17 to 19). Furthermore, the center of gravity of the plan figure of the current injection region 321 and the plan figure of the contour line T can be different (see FIGS. 20 to 23). As described in the first embodiment, it is possible to improve the controllability of the polarization of the VCSEL element 300 by adopting such a configuration.
- the planar figure of the current injection region 321 and the planar figure of the contour line T have one of the above relationships, thereby providing lateral (XY direction) asymmetry with respect to light and current, It is possible to improve the controllability of the polarization of the VCSEL element 300 .
- the mesa M is formed by photolithography and etching.
- the material of the oxidized constricting layer 305 is oxidized from the outer peripheral side by a method such as heating the laminated body 350 in a water vapor atmosphere to form an oxidized region 305b.
- the shape of the non-oxidized region 305a viewed from the Z direction can be controlled by the shape of the mesa M viewed from the Z direction.
- the VCSEL element 300 can be manufactured by providing the base portion 301c on the substrate 301 and laminating the first light reflecting layer 306, the second light reflecting layer 307, and the like by the same method as in the first embodiment.
- VCSEL device 300 can also be manufactured by other manufacturing methods.
- the laminated body 350 is laminated on the substrate 301 to fabricate the VCSEL element 300.
- the laminated body 350 is laminated on another supporting substrate, and the supporting substrate is removed to form the laminated body 350 on the substrate.
- 301 may be joined.
- the substrate 301 can be, for example, a semi-insulating Si substrate.
- the laminated body 350 and the substrate 301 are bonded, by shifting the positions of the base portion 301c of the substrate 301 and the non-oxidized region 305a when viewed from the Z direction, the plan figure of the contour line T of the concave mirror 306c and the current injection region 321 are shifted. It is possible to make the center of gravity of the two plane figures different.
- the interface between the first semiconductor layer 302 and the active layer 304 is defined as a reference plane S
- the contour line T of the concave mirror 306c is a line representing the height of the concave surface 306d from the reference plane S.
- the contour line T may be a line representing the height of the convex surface 306e of .
- the reference plane S may be the interface between the second semiconductor layer 303 and the second light reflecting layer 307 instead of the interface between the first semiconductor layer 302 and the active layer 304 .
- the concave mirror 306c is laminated on the base 301c provided on the substrate 301 and formed into a concave mirror shape, it is not limited to this.
- a structure made of a dielectric material, a synthetic resin, or the like and having the same shape as the base 301c is provided. You may
- the first semiconductor layer 302 is made of an n-type semiconductor material and the second semiconductor layer 303 is made of a p-type semiconductor material
- the first semiconductor layer 302 is made of a p-type semiconductor material
- the second semiconductor layer 303 is made of a p-type semiconductor material.
- the non-oxidized region 305a of the oxidized constricting layer 305 can be made of an n-type material with a high impurity concentration.
- the VCSEL element 300 may have other configurations that enable the operation of the VCSEL element 300 to be implemented.
- the present technology can also have the following configuration.
- the laminate is provided with a current constriction structure that constricts current and forms a current injection region in which the current concentrates
- the first light reflecting layer is provided with a concave mirror having a concave surface on the side of the laminate and a convex surface on the side opposite to the laminate, A plan view of the current injection region viewed from the direction of the optical axis of the emitted light is defined as a first figure, and a plan view of contour lines representing the height of the concave mirror from the active layer viewed from the direction
- a vertical cavity surface emitting laser device (2) a first light reflecting layer that reflects light of a specific wavelength; a second light reflecting layer that reflects light of the wavelength; a first semiconductor layer made of a semiconductor material having a first conductivity type; a second semiconductor layer made of a semiconductor material having a second conductivity type; an active layer disposed therebetween for emitting light due to carrier recombination, and a laminate disposed between the first light reflective layer and the second light reflective layer;
- the laminate is provided with a current constriction structure that constricts current and forms a current injection region in which the current concentrates
- the first light reflecting layer is provided with a concave mirror having a concave surface on the side of the laminate and a convex surface on the side opposite to the laminate, A plan view of the current injection region viewed from the direction of the optical axis of the emitted light is defined as a first figure, and a plan view of contour lines representing the height of the concave
- the center of gravity of the first graphic does not coincide with the center of gravity of the second graphic.
- a first light reflecting layer that reflects light of a specific wavelength; a second light reflecting layer that reflects light of the wavelength; a first semiconductor layer made of a semiconductor material having a first conductivity type; a second semiconductor layer made of a semiconductor material having a second conductivity type; an active layer disposed therebetween for emitting light due to carrier recombination, and a laminate disposed between the first light reflective layer and the second light reflective layer;
- the laminate is provided with a current constriction structure that constricts current and forms a current injection region in which the current concentrates,
- the first light reflecting layer is provided with a concave mirror having a concave surface on the side of the laminate and a convex surface on the side opposite to the laminate, A plan view of the current injection region viewed from the direction of the optical axis of the emitted light is defined as a first figure, and a plan view of contour lines representing the
- the first figure and the second figure are not perfect circles but are similar to each other.
- Vertical cavity surface emitting laser device (4) The vertical cavity surface emitting laser device according to (1) above,
- the first figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them
- the second figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them, and is a figure dissimilar to the first figure.
- the vertical cavity surface emitting laser device according to (2) above A vertical cavity surface emitting laser device, wherein a distance between the center of gravity of the first figure and the center of gravity of the second figure in a plane perpendicular to the direction of the optical axis is 0.03 ⁇ m or more.
- the vertical cavity surface emitting laser device according to (3) above The first figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them,
- the second figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them, and is similar to the first figure.
- Vertical cavity surface emitting laser device The first figure is a closed figure consisting of a circle, an ellipse, a rectangle, or a combination of at least two of them.
- the vertical cavity surface emitting laser device according to any one of (1) to (7) above, The current confinement structure has a non-ion-implanted region into which ions are not implanted into the laminate, and an ion-implanted region provided around the non-ion-implanted region and into which ions are implanted into the laminate, The vertical cavity surface emitting laser device, wherein the current injection region is the non-ion-implanted region.
- the vertical cavity surface emitting laser device according to any one of (1) to (7) above,
- the current confinement structure has a tunnel junction region in which a tunnel junction is formed in the laminate, and a non-tunnel junction region provided around the tunnel junction region in which no tunnel junction is formed,
- the vertical cavity surface emitting laser device, wherein the current injection region is the tunnel junction region.
- the vertical cavity surface emitting laser device according to (12) above, The vertical cavity surface emitting laser device, wherein the tunnel junction region is formed by a buried tunnel junction.
- the vertical cavity surface emitting laser device according to any one of (1) to (7) above,
- the current confinement structure has a non-oxidized region in which the semiconductor material is not oxidized in the stacked body, and an oxidized region provided around the non-oxidized region and in which the semiconductor material is oxidized,
- the vertical cavity surface emitting laser device, wherein the current injection region is the non-oxidized region.
- the vertical cavity surface emitting laser device has a first surface on the side of the active layer and a second surface on the side opposite to the active layer, and the second surface is provided with a base forming a convex curved surface.
- the first light reflecting layer is a multilayer light reflecting film provided on the second surface, and the portion of the first light reflecting layer multilayer light reflecting film provided on the base serves as the concave mirror.
- the vertical cavity surface emitting laser device according to any one of (1) to (17) above, further comprising a substrate having a first surface on the side of the active layer and a second surface on the side opposite to the active layer, the second surface being provided with a base portion forming a convex curved surface;
- the first light reflecting layer is a multilayer light reflecting film provided on the second surface, and the portion of the first light reflecting layer multilayer light reflecting film provided on the base serves as the concave mirror.
- the vertical cavity surface emitting laser device according to any one of (1) to (19) above,
- the concave mirror has a concave surface that faces the active layer, and the concave surface has a radius of curvature of 1000 ⁇ m or less.
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Abstract
Description
上記第1の光反射層は、特定の波長の光を反射する。
上記第2の光反射層は、上記波長の光を反射する。
上記積層体は、第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、上記第1の半導体層と上記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、上記第1の光反射層と上記第2の光反射層の間に配置されている。
上記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられている。
上記第1の光反射層には、上記積層体側の面が凹面、上記積層体とは反対側の面が凸面となる凹面鏡が設けられている。
出射光の光軸方向から上記電流注入領域を見た平面図形を第1の図形とし、上記凹面鏡の上記活性層からの高さを表す等高線を上記光軸方向から見た平面図形を第2の図形とすると、上記第1の図形と上記第2の図形は相似ではない。
上記第1の光反射層は、特定の波長の光を反射する。
上記第2の光反射層は、上記波長の光を反射する。
上記積層体は、第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、上記第1の半導体層と上記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、上記第1の光反射層と上記第2の光反射層の間に配置されている。
上記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられている。
上記第1の光反射層には、上記積層体側の面が凹面、上記積層体とは反対側の面が凸面となる凹面鏡が設けられている。
出射光の光軸方向から上記電流注入領域を見た平面図形を第1の図形とし、上記凹面鏡の上記活性層からの高さを表す等高線を上記光軸方向から見た平面図形を第2の図形とすると、上記第1の図形の重心と上記第2の図形の重心は一致しない。
上記第1の光反射層は、特定の波長の光を反射する。
上記第2の光反射層は、上記波長の光を反射する。
上記積層体は、第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、上記第1の半導体層と上記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、上記第1の光反射層と上記第2の光反射層の間に配置されている。
上記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられている。
上記第1の光反射層には、上記積層体側の面が凹面、上記積層体とは反対側の面が凸面となる凹面鏡が設けられている。
出射光の光軸方向から上記電流注入領域を見た平面図形を第1の図形とし、上記凹面鏡の上記活性層からの高さを表す等高線を上記光軸方向から見た平面図形を第2の図形とすると、上記第1の図形と上記第2の図形は共に真円形ではなく、相似である。
上記第2の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、上記第1の図形とは相似でない図形であってもよい。
上記第2の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、上記第1の図形と相似である図形であってもよい。
上記電流注入領域は上記トンネル接合領域であってもよい。
上記非トンネル接合領域は、イオンが注入されたトンネル接合層により形成されていてもよい。
上記電流注入領域は上記非酸化領域であってもよい。
上記第1の光反射層は上記第2の面上に設けられた多層光反射膜であり、上記第1の光反射層多層光反射膜のうち上記基部上に設けられた部分が上記凹面鏡を形成してもよい。
上記第1の光反射層は上記第2の面上に設けられた多層光反射膜であり、上記第1の光反射層多層光反射膜のうち上記基部上に設けられた部分が上記凹面鏡を形成してもよい。
本技術の第1の実施形態に係るVCSEL(Vertical Cavity Surface Emitting Laser:垂直共振器型面発光レーザ)素子について説明する。本開示の各図において、VCSEL素子から出射される光の光軸方向をZ方向とし、Z方向に直交する一方向をX方向、Z方向及びX方向に直交する方向をY方向とする。
図1は本実施形態に係るVCSEL素子100の断面図であり、図2はVCSEL素子100の一部構成を分解して示す模式図である。これらの図に示すように、VCSEL素子100は、第1半導体層101、第2半導体層102、活性層103、第1光反射層104、第2光反射層105、第1電極106及び第2電極107を備える。このうち、第1半導体層101、第2半導体層102及び活性層103を併せて積層体150とする。
VCSEL素子100の動作について説明する。図5は、VCSEL素子100の動作を示す模式図である。第1電極106と第2電極107の間に電圧を印加すると、第1電極106と第2電極107の間に電流が流れる。電流は電流狭窄構造により狭窄され、図5に矢印Cとして示すように電流注入領域121に注入される。
凹面鏡104cの等高線と電流注入領域121の平面図形について説明する。なお、以下の説明において「平面図形」とは、レーザ光Lの光軸方向(Z方向)から見た等高線及び電流注入領域121の形状を指す。
図6は、凹面鏡104cの等高線を示す模式図である。図6(a)は、凹面鏡104cの等高線Tの平面図形を示す平面図であり、図6(b)はVCSEL素子100の一部の模式的断面図である。図6(b)に示すように、第1半導体層101と活性層103の界面を基準面Sとする。等高線Tは、基準面Sからの凹面104dの高さHを線で表したものである。
図7は、VCSEL素子100の等高線Tが有する平面図形の一例を示す模式図である。図7(a)は、等高線Tの平面図形を示す平面図であり、図7(b)はVCSEL素子100の模式的断面図である。
図8は、VCSEL素子100の電流注入領域121が有する平面図形の他の例を示す模式図である。図8(a)は、電流注入領域121の平面図形を示す平面図であり、図8(b)はVCSEL素子100の模式的断面図である。
VCSEL素子100では、電流注入領域121の平面図形(第1の図形)と凹面鏡104cの等高線Tの平面図形(第2の図形)が以下に示すいずれかの関係を有する。図9乃至図23は、電流注入領域121の平面図形と等高線Tの平面図形の例を示す模式図である。各図において図(a)は、等高線T及び電流注入領域121の平面図形を示す平面図であり、図(b)はVCSEL素子100の模式的断面図である。
電流注入領域121の平面図形と等高線Tの平面図形は相似ではないものとすることができる。具体的には、電流注入領域121の平面図形は円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形とすることができる。等高線Tの平面図形は円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、電流注入領域121の平面図形とは相似でない図形とすることができる。電流注入領域121の平面図形と等高線Tの平面図形はどちらか一方であれば真円形であってもよい。また、電流注入領域121の平面図形の重心と等高線Tの平面図形の重心は一致するものとすることができる。以下、電流注入領域121の平面図形と等高線Tの平面図形が相似ではない場合の、電流注入領域121の平面図形と等高線Tの平面図形の具体例を挙げる。
電流注入領域121の平面図形と等高線Tの平面図形は相似であって、真円形ではないものとすることができる。具体的には、電流注入領域121の平面図形は円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、真円形ではないものとすることができる。等高線Tの平面図形は円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって真円形ではなく、電流注入領域121の平面図形と相似である図形とすることができる。また、電流注入領域121の平面図形の重心と等高線Tの平面図形の重心は一致するものとすることができる。以下、電流注入領域121の平面図形と等高線Tの平面図形が相似であって真円形ではない場合の、電流注入領域121の平面図形と等高線Tの平面図形の具体例を挙げる。
電流注入領域121の平面図形と等高線Tの平面図形は重心が相違するものとすることができる。具体的には、電流注入領域121の平面図形は円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形とすることができる。等高線Tの平面図形は円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形とすることができ、重心が電流注入領域121の平面図形とは相違するものとすることができる。光軸方向(Z方向)に垂直な平面(X-Y平面)における、電流注入領域121の平面図形と等高線Tの平面図形の重心間の距離は0.03μm以上が好適である。電流注入領域121の平面図形と等高線Tの平面図形は相似であってもよく、相似でなくてもよい。以下、電流注入領域121の平面図形と等高線Tの平面図形は重心が相違する場合の、電流注入領域121の平面図形と等高線Tの平面図形の具体例を挙げる。
以上のようにVCSEL素子100では、電流注入領域121の平面図形と等高線Tの平面図形が上記いずれかの関係を有することにより、光と電流に対して横方向(X-Y方向)の非対称性を設け、VCSEL素子100の偏光の制御性を向上させることが可能である。VCSEL素子100では偏光制御に結晶の非対称性を利用しないため、結晶が非対称性を有しない基板(C面基板等)を利用してVCSEL素子100を作製することも可能である。
VCSEL素子100の製造方法について説明する。図24乃至図26は、VCSEL素子100の製造方法を示す模式図である。まず、図24に示すように積層体150を作製する。積層体150は、第1半導体層101(基板)上に活性層103及び第2半導体層102を積層して作製することができる。活性層103及び第2半導体層102は有機金属化学的気相成長(MOCVD;Metal Organic-Chemical Vapor Deposition)法等により積層することができる。
上記説明において、第1半導体層101と活性層103の界面を基準面Sとし、凹面鏡104cの等高線Tは基準面Sからの凹面104dの高さを表す線とした(図6参照)が、基準面Sからの凸面104eの高さを表す線を等高線Tとしてもよい。また、基準面Sは、第1半導体層101と活性層103の界面ではなく、第2電極107と第2光反射層105の界面としてもよい。
本技術の第2の実施形態に係るVCSEL(Vertical Cavity Surface Emitting Laser:垂直共振器型面発光レーザ)素子について説明する。本実施形態に係るVCSEL素子は、第1の実施形態に係るVCSEL素子に対して主に電流狭窄構造が異なる。
図27は本実施形態に係るVCSEL素子200の断面図である。同図に示すように、VCSEL素子200は、基板201、第1半導体層202、第2半導体層203、第3半導体層204、活性層205、トンネル接合層206、第1光反射層207、第2光反射層208、第1電極209、第2電極210及び絶縁膜211を備える。このうち、第1半導体層202、第2半導体層203、第3半導体層204、活性層205及びトンネル接合層206を併せて積層体250とする。
VCSEL素子200は第1の実施形態に係るVCSEL素子100と同様に動作する。即ち、第1電極209と第2電極210の間に電圧を印加すると、第1電極209と第2電極210の間に電流が流れる。電流は電流狭窄構造により狭窄され、電流注入領域221に注入される。この注入電流によって生じた自然放出光は第1光反射層207及び第2光反射層208によって反射され、レーザ発振を生じる。これにより生じたレーザ光は、第2光反射層208を透過し、Z方向を光軸方向としてVCSEL素子200から出射される。
凹面鏡207cの等高線と電流注入領域221の平面図形について説明する。なお、以下の説明において「平面図形」とは、レーザ光の光軸方向(Z方向)から見た等高線及び電流注入領域221の形状を指す。
図30は、凹面鏡207cの等高線を示す模式図である。図30(a)は、凹面鏡207cの等高線Tの平面図形を示す平面図であり、図30(b)はVCSEL素子200の一部の模式的断面図である。図30(b)に示すように、第1半導体層202と活性層205の界面を基準面Sとする。等高線Tは、基準面Sからの凹面207dの高さHを線で表したものである。
VCSEL素子200において、電流注入領域221の平面図形(第1の図形)と等高線Tの平面図形(第2の図形)の関係については第1の実施形態と同様である。即ち、電流注入領域221の平面図形と等高線Tの平面図形は相似ではないものとすることができる(図9乃至図16参照)。また、電流注入領域221の平面図形と等高線Tの平面図形は相似であって、真円形ではないものとすることができる(図17乃至図19参照)。さらに、電流注入領域221の平面図形と等高線Tの平面図形は重心が相違するものとすることができる(図20乃至図23参照)。第1の実施形態において説明したように、このような構成とすることによりVCSEL素子200の偏光の制御性を向上させることが感応である。
VCSEL素子200においても、電流注入領域221の平面図形と等高線Tの平面図形が上記いずれかの関係を有することにより、光と電流に対して横方向(X-Y方向)の非対称性を設け、VCSEL素子200の偏光の制御性を向上させることが可能である。
VCSEL素子200の製造方法では、基板201上に第2層206bまでの各層を有機金属化学的気相成長法等により積層した後、フォトリソグラフィ及びエッチングにより第1層206a及び第2層206bの不要部分を除去し、トンネル接合層206を形成する。トンネル接合層206はフォトリソグラフィにより、自由に形状を制御することが可能である。
VCSEL素子200では上記のように、トンネル接合層206による埋め込みトンネル接合によって電流狭窄構造が設けられるものとしたが、次のように、トンネル接合層206へのイオン注入によって電流狭窄構造を設けることも可能である。
上記説明では、基板201上に積層体250を積層し、VCSEL素子200を作製するものとしたが、他の支持基板上に積層体250を積層し、支持基板を除去して積層体250を基板201に接合してもよい。この場合、基板201は例えば半絶縁性Si基板とすることができる。この製造方法では、積層体250と基板201の接合時に、Z方向から見た基板201の基部201cとトンネル接合層206の位置をずらすことにより、凹面鏡207cの等高線Tの平面図形と電流注入領域221の平面図形の重心を相違させることが可能である。
本技術の第3の実施形態に係るVCSEL(Vertical Cavity Surface Emitting Laser:垂直共振器型面発光レーザ)素子について説明する。本実施形態に係るVCSEL素子は、第1の実施形態に係るVCSEL素子に対して主に電流狭窄構造が異なる。
図33は本実施形態に係るVCSEL素子300の断面図である。同図に示すように、VCSEL素子300は、基板301、第1半導体層302、第2半導体層303、活性層304、酸化狭窄層305、第1光反射層306、第2光反射層307、第1電極308、第2電極309及び絶縁膜310を備える。このうち、第1半導体層302、第2半導体層303、活性層304及び酸化狭窄層305を併せて積層体350とする。
VCSEL素子300は第1の実施形態に係るVCSEL素子300と同様に動作する。即ち、第1電極308と第2電極309の間に電圧を印加すると、第1電極308と第2電極309の間に電流が流れる。電流は電流狭窄構造により狭窄され、電流注入領域321に注入される。この注入電流によって生じた自然放出光は第1光反射層306及び第2光反射層307によって反射され、レーザ発振を生じる。これにより生じたレーザ光は、第2光反射層307を透過し、Z方向を光軸方向としてVCSEL素子300から出射される。
凹面鏡306cの等高線と電流注入領域321の平面図形について説明する。なお、以下の説明において「平面図形」とは、レーザ光の光軸方向(Z方向)から見た等高線及び電流注入領域321の形状を指す。
図36は、凹面鏡306cの等高線を示す模式図である。図36(a)は、凹面鏡306cの等高線Tの平面図形を示す平面図であり、図36(b)はVCSEL素子300の一部の模式的な断面図である。図36(b)に示すように、第1半導体層302と活性層304の界面を基準面Sとする。等高線Tは、基準面Sからの凹面306dの高さHを線で表したものである。
VCSEL素子300において、電流注入領域321の平面図形(第1の図形)と等高線Tの平面図形(第2の図形)の関係については第1の実施形態と同様である。即ち、電流注入領域321の平面図形と等高線Tの平面図形は相似ではないものとすることができる(図9乃至図16参照)。また、電流注入領域321の平面図形と等高線Tの平面図形は相似であって、真円形ではないものとすることができる(図17乃至図19参照)。さらに、電流注入領域321の平面図形と等高線Tの平面図形は重心が相違するものとすることができる(図20乃至図23参照)。第1の実施形態において説明したように、このような構成とすることによりVCSEL素子300の偏光の制御性を向上させることが感応である。
VCSEL素子300においても、電流注入領域321の平面図形と等高線Tの平面図形が上記いずれかの関係を有することにより、光と電流に対して横方向(X-Y方向)の非対称性を設け、VCSEL素子300の偏光の制御性を向上させることが可能である。
VCSEL素子300の製造方法では、基板301上に第2光反射層307までの各層を、有機金属化学的気相成長法等によって積層した後、フォトリソグラフィ及びエッチングによりメサMを形成する。続いて、積層体350を水蒸気雰囲気下で加熱する等の方法で酸化狭窄層305の材料を外周側から酸化させ、酸化領域305bを形成する。この際、Z方向から見たメサMの形状によって、同方向から見た非酸化領域305aの形状を制御することができる。
上記説明では、基板301上に積層体350を積層し、VCSEL素子300を作製するものとしたが、他の支持基板上に積層体350を積層し、支持基板を除去して積層体350を基板301に接合してもよい。この場合、基板301は例えば半絶縁性Si基板とすることができる。この製造方法では、積層体350と基板301の接合時に、Z方向から見た基板301の基部301cと非酸化領域305aの位置をずらすことにより、凹面鏡306cの等高線Tの平面図形と電流注入領域321の平面図形の重心を相違させることが可能である。
本開示中に記載された効果はあくまで例示であって限定されるものでは無く、また他の効果があってもよい。上記の複数の効果の記載は、それらの効果が必ずしも同時に発揮されるということを意味しているのではない。条件等により、少なくとも上記した効果のいずれかが得られることを意味しており、本開示中に記載されていない効果が発揮される可能性もある。また、本開示において説明した特徴部分のうち、少なくとも2つの特徴部分を任意に組み合わせることも可能である。
(1)
特定の波長の光を反射する第1の光反射層と、
上記波長の光を反射する第2の光反射層と、
第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、上記第1の半導体層と上記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、上記第1の光反射層と上記第2の光反射層の間に配置された積層体と
を具備し、
上記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられ、
上記第1の光反射層には、上記積層体側の面が凹面、上記積層体とは反対側の面が凸面となる凹面鏡が設けられ、
出射光の光軸方向から上記電流注入領域を見た平面図形を第1の図形とし、上記凹面鏡の上記活性層からの高さを表す等高線を上記光軸方向から見た平面図形を第2の図形とすると、上記第1の図形と上記第2の図形は相似ではない
垂直共振器型面発光レーザ素子。
(2)
特定の波長の光を反射する第1の光反射層と、
上記波長の光を反射する第2の光反射層と、
第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、上記第1の半導体層と上記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、上記第1の光反射層と上記第2の光反射層の間に配置された積層体と
を具備し、
上記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられ、
上記第1の光反射層には、上記積層体側の面が凹面、上記積層体とは反対側の面が凸面となる凹面鏡が設けられ、
出射光の光軸方向から上記電流注入領域を見た平面図形を第1の図形とし、上記凹面鏡の上記活性層からの高さを表す等高線を上記光軸方向から見た平面図形を第2の図形とすると、上記第1の図形の重心と上記第2の図形の重心は一致しない
垂直共振器型面発光レーザ素子。
(3)
特定の波長の光を反射する第1の光反射層と、
上記波長の光を反射する第2の光反射層と、
第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、上記第1の半導体層と上記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、上記第1の光反射層と上記第2の光反射層の間に配置された積層体と
を具備し、
上記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられ、
上記第1の光反射層には、上記積層体側の面が凹面、上記積層体とは反対側の面が凸面となる凹面鏡が設けられ、
出射光の光軸方向から上記電流注入領域を見た平面図形を第1の図形とし、上記凹面鏡の上記活性層からの高さを表す等高線を上記光軸方向から見た平面図形を第2の図形とすると、上記第1の図形と上記第2の図形は共に真円形ではなく、相似である
垂直共振器型面発光レーザ素子。
(4)
上記(1)に記載の垂直共振器型面発光レーザ素子であって、
上記第1の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であり、
上記第2の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、上記第1の図形とは相似でない図形である
垂直共振器型面発光レーザ素子。
(5)
上記(2)記載の垂直共振器型面発光レーザ素子であって、
上記光軸方向に垂直な平面内における、上記第1の図形の重心と上記第2の図形の重心の距離は0.03μm以上である
垂直共振器型面発光レーザ素子。
(6)
上記(3)記載の垂直共振器型面発光レーザ素子であって、
上記第1の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であり、
上記第2の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、上記第1の図形と相似である図形である
垂直共振器型面発光レーザ素子。
(7)
上記(1)又は(3)に記載の垂直共振器型面発光レーザ素子であって、
上記第1の図形の重心と上記第2の図形の重心は一致する
垂直共振器型面発光レーザ素子。
(8)
上記(1)から(7)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記電流狭窄構造は、上記積層体にイオンが注入されていない非イオン注入領域と、上記非イオン注入領域の周囲に設けられ、上記積層体にイオンが注入されたイオン注入領域とを有し、上記電流注入領域は上記非イオン注入領域である
垂直共振器型面発光レーザ素子。
(9)
上記(8)記載の垂直共振器型面発光レーザ素子であって、
上記第1の半導体層及び第2の半導体層は、GaNからなる
垂直共振器型面発光レーザ素子。
(10)
上記(9)記載の垂直共振器型面発光レーザ素子であって、
上記第1の半導体層は、C面GaN基板である
垂直共振器型面発光レーザ素子。
(11)
上記(8)から(10)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記イオンはホウ素イオンである
垂直共振器型面発光レーザ素子。
(12)
上記(1)から(7)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記電流狭窄構造は、上記積層体においてトンネル接合が形成されたトンネル接合領域と、上記トンネル接合領域の周囲に設けられ、トンネル接合が形成されていない非トンネル接合領域とを有し、
上記電流注入領域は上記トンネル接合領域である
垂直共振器型面発光レーザ素子。
(13)
上記(12)記載の垂直共振器型面発光レーザ素子であって、
上記トンネル接合領域は埋め込みトンネル接合により形成されている
垂直共振器型面発光レーザ素子。
(14)
上記(12)記載の垂直共振器型面発光レーザ素子であって、
上記トンネル接合領域は、イオンが注入されていないトンネル接合層により形成され、
上記非トンネル接合領域は、イオンが注入されたトンネル接合層により形成されている
垂直共振器型面発光レーザ素子。
(15)
上記(12)から(14)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
請求項12に記載の垂直共振器型面発光レーザ素子であって、
上記第1の半導体層及び第2の半導体層は、InPからなる
垂直共振器型面発光レーザ素子。
(16)
上記(1)から(7)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記電流狭窄構造は、上記積層体において半導体材料が酸化されていない非酸化領域と、上記非酸化領域の周囲に設けられ、半導体材料が酸化された酸化領域とを有し、
上記電流注入領域は上記非酸化領域である
垂直共振器型面発光レーザ素子。
(17)
上記(16)記載の垂直共振器型面発光レーザ素子であって、
上記第1の半導体層及び第2の半導体層は、GaAsからなる
垂直共振器型面発光レーザ素子。
(18)
上記(1)から(17)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記第1の半導体層は、上記活性層側の第1の面と上記活性層とは反対側の第2の面を有し、上記第2の面には凸型曲面を形成する基部が設けられ、
上記第1の光反射層は上記第2の面上に設けられた多層光反射膜であり、上記第1の光反射層多層光反射膜のうち上記基部上に設けられた部分が上記凹面鏡を形成する
垂直共振器型面発光レーザ素子。
(19)
上記(1)から(17)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記活性層側の第1の面と上記活性層とは反対側の第2の面を有し、上記第2の面には凸型曲面を形成する基部が設けられた基板をさらに具備し、
上記第1の光反射層は上記第2の面上に設けられた多層光反射膜であり、上記第1の光反射層多層光反射膜のうち上記基部上に設けられた部分が上記凹面鏡を形成する
垂直共振器型面発光レーザ素子。
(20)
上記(1)から(19)のうちいずれか一つに記載の垂直共振器型面発光レーザ素子であって、
上記凹面鏡は、上記活性層側の面である凹面を有し、上記凹面は曲率半径が1000μm以下である
垂直共振器型面発光レーザ素子。
201、301…基板
101、202、302…第1半導体層
102、203、303…第2半導体層
204…第3半導体層
103、205、304…活性層
206…トンネル接合層
305…酸化狭窄層
104、207、306…第1光反射層
104c、207c、306c…凹面鏡
105、208、307…第2光反射層
106、209、308…第1電極
107、210、309…第2電極
121、221、321…電流注入領域
122、222、322…絶縁領域
150、250、350…積層体
Claims (20)
- 特定の波長の光を反射する第1の光反射層と、
前記波長の光を反射する第2の光反射層と、
第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、前記第1の半導体層と前記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、前記第1の光反射層と前記第2の光反射層の間に配置された積層体と
を具備し、
前記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられ、
前記第1の光反射層には、前記積層体側の面が凹面、前記積層体とは反対側の面が凸面となる凹面鏡が設けられ、
出射光の光軸方向から前記電流注入領域を見た平面図形を第1の図形とし、前記凹面鏡の前記活性層からの高さを表す等高線を前記光軸方向から見た平面図形を第2の図形とすると、前記第1の図形と前記第2の図形は相似ではない
垂直共振器型面発光レーザ素子。 - 特定の波長の光を反射する第1の光反射層と、
前記波長の光を反射する第2の光反射層と、
第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、前記第1の半導体層と前記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、前記第1の光反射層と前記第2の光反射層の間に配置された積層体と
を具備し、
前記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられ、
前記第1の光反射層には、前記積層体側の面が凹面、前記積層体とは反対側の面が凸面となる凹面鏡が設けられ、
出射光の光軸方向から前記電流注入領域を見た平面図形を第1の図形とし、前記凹面鏡の前記活性層からの高さを表す等高線を前記光軸方向から見た平面図形を第2の図形とすると、前記第1の図形の重心と前記第2の図形の重心は一致しない
垂直共振器型面発光レーザ素子。 - 特定の波長の光を反射する第1の光反射層と、
前記波長の光を反射する第2の光反射層と、
第1の伝導型を有する半導体材料からなる第1の半導体層と、第2の伝導型を有する半導体材料からなる第2の半導体層と、前記第1の半導体層と前記第2の半導体層の間に配置され、キャリア再結合による発光を生じる活性層とを備え、前記第1の光反射層と前記第2の光反射層の間に配置された積層体と
を具備し、
前記積層体には、電流を狭窄し、電流が集中する電流注入領域を形成する電流狭窄構造が設けられ、
前記第1の光反射層には、前記積層体側の面が凹面、前記積層体とは反対側の面が凸面となる凹面鏡が設けられ、
出射光の光軸方向から前記電流注入領域を見た平面図形を第1の図形とし、前記凹面鏡の前記活性層からの高さを表す等高線を前記光軸方向から見た平面図形を第2の図形とすると、前記第1の図形と前記第2の図形は共に真円形ではなく、相似である
垂直共振器型面発光レーザ素子。 - 請求項1に記載の垂直共振器型面発光レーザ素子であって、
前記第1の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であり、
前記第2の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、前記第1の図形とは相似でない図形である
垂直共振器型面発光レーザ素子。 - 請求項2に記載の垂直共振器型面発光レーザ素子であって、
前記光軸方向に垂直な平面内における、前記第1の図形の重心と前記第2の図形の重心の距離は0.03μm以上である
垂直共振器型面発光レーザ素子。 - 請求項3に記載の垂直共振器型面発光レーザ素子であって、
前記第1の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であり、
前記第2の図形は、円形、楕円形、矩形又はこれらの少なくとも2つの組み合わせからなる閉図形であって、前記第1の図形と相似である図形である
垂直共振器型面発光レーザ素子。 - 請求項1又は3に記載の垂直共振器型面発光レーザ素子であって、
前記第1の図形の重心と前記第2の図形の重心は一致する
垂直共振器型面発光レーザ素子。 - 請求項1から3のうちいずれか1項に記載の垂直共振器型面発光レーザ素子であって、
前記電流狭窄構造は、前記積層体にイオンが注入されていない非イオン注入領域と、前記非イオン注入領域の周囲に設けられ、前記積層体にイオンが注入されたイオン注入領域とを有し、前記電流注入領域は前記非イオン注入領域である
垂直共振器型面発光レーザ素子。 - 請求項8に記載の垂直共振器型面発光レーザ素子であって、
前記第1の半導体層及び第2の半導体層は、GaNからなる
垂直共振器型面発光レーザ素子。 - 請求項9に記載の垂直共振器型面発光レーザ素子であって、
前記第1の半導体層は、C面GaN基板である
垂直共振器型面発光レーザ素子。 - 請求項8に記載の垂直共振器型面発光レーザ素子であって、
前記イオンはホウ素イオンである
垂直共振器型面発光レーザ素子。 - 請求項1から3のうちいずれか1項に記載の垂直共振器型面発光レーザ素子であって、
前記電流狭窄構造は、前記積層体においてトンネル接合が形成されたトンネル接合領域と、前記トンネル接合領域の周囲に設けられ、トンネル接合が形成されていない非トンネル接合領域とを有し、
前記電流注入領域は前記トンネル接合領域である
垂直共振器型面発光レーザ素子。 - 請求項12に記載の垂直共振器型面発光レーザ素子であって、
前記トンネル接合領域は埋め込みトンネル接合により形成されている
垂直共振器型面発光レーザ素子。 - 請求項12に記載の垂直共振器型面発光レーザ素子であって、
前記トンネル接合領域は、イオンが注入されていないトンネル接合層により形成され、
前記非トンネル接合領域は、イオンが注入されたトンネル接合層により形成されている
垂直共振器型面発光レーザ素子。 - 請求項12に記載の垂直共振器型面発光レーザ素子であって、
前記第1の半導体層及び第2の半導体層は、InPからなる
垂直共振器型面発光レーザ素子。 - 請求項1から3のうちいずれか1項に記載の垂直共振器型面発光レーザ素子であって、
前記電流狭窄構造は、前記積層体において半導体材料が酸化されていない非酸化領域と、前記非酸化領域の周囲に設けられ、半導体材料が酸化された酸化領域とを有し、
前記電流注入領域は前記非酸化領域である
垂直共振器型面発光レーザ素子。 - 請求項16に記載の垂直共振器型面発光レーザ素子であって、
前記第1の半導体層及び第2の半導体層は、GaAsからなる
垂直共振器型面発光レーザ素子。 - 請求項1から3のうちいずれか1項に記載の垂直共振器型面発光レーザ素子であって、
前記第1の半導体層は、前記活性層側の第1の面と前記活性層とは反対側の第2の面を有し、前記第2の面には凸型曲面を形成する基部が設けられ、
前記第1の光反射層は前記第2の面上に設けられた多層光反射膜であり、前記第1の光反射層多層光反射膜のうち前記基部上に設けられた部分が前記凹面鏡を形成する
垂直共振器型面発光レーザ素子。 - 請求項1から3のうちいずれか1項に記載の垂直共振器型面発光レーザ素子であって、
前記活性層側の第1の面と前記活性層とは反対側の第2の面を有し、前記第2の面には凸型曲面を形成する基部が設けられた基板をさらに具備し、
前記第1の光反射層は前記第2の面上に設けられた多層光反射膜であり、前記第1の光反射層多層光反射膜のうち前記基部上に設けられた部分が前記凹面鏡を形成する
垂直共振器型面発光レーザ素子。 - 請求項1から3のうちいずれか1項に記載の垂直共振器型面発光レーザ素子であって、
前記凹面鏡は、前記活性層側の面である凹面を有し、前記凹面は曲率半径が1000μm以下である
垂直共振器型面発光レーザ素子。
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