Two-dimensional photonic crystal laser

Abstract

Provided is a two-dimensional photonic crystal laser capable of approximately uniformizing the intensity distribution of light in the cross section of a laser beam. A two-dimensional photonic crystal laser (10) is provided with: an active layer (11); a two-dimensional photonic crystal layer (12) which is provided on one surface side of the active layer (11) and in which different refractive index regions (122) having a refractive index different from the refractive index of the base material (121) are periodically two-dimensionally arranged within the plate-shaped base material (121); and a first electrode (171) and a second electrode (172) provided so as to sandwich the active layer (11) and the two-dimensional photonic crystal layer (12) in the lamination direction, in which the first electrode (171) has an opening (175), a projection (1721) of a circumscribed circle of the second electrode (172) onto the first electrode (171) is located within the opening (175), and at least a portion of the periphery of the opening (175) of the first electrode (171) protrudes into the projection (1721).

Description

Technical Field

[0001] The invention relates to a two-dimensional photonic crystal laser which uses a two-dimensional photonic crystal to amplify light. Background Art

[0002] A two-dimensional photonic crystal laser generally has a stacked body obtained by sandwiching an active layer and a two-dimensional photonic crystal layer with a pair of cladding layers, and also has a pair of electrodes (electrode pair) so as to sandwich the stacked body. The active layer generates light of a specific emission wavelength range by injecting carriers (holes, electrons) by the electrode pair. The two-dimensional photonic crystal layer has a structure in which a different refractive index region whose refractive index is different from that of the parent material is periodically arranged in a two-dimensional manner in a plate-like parent material. The different refractive index region includes a hole (air) formed in the parent material, or a component embedded in the parent material and having a refractive index different from that of the parent material.

[0003] In such a two-dimensional photonic crystal laser, among the light generated in the active layer, only the light of the specified wavelength corresponding to the period length of the configuration of the different refractive index region is amplified in the two-dimensional photonic crystal layer to perform laser oscillation, and the laser beam is emitted in a direction perpendicular to the two-dimensional photonic crystal layer. However, since there are electrodes in a direction perpendicular to the two-dimensional photonic crystal layer, the laser beam may be blocked by the electrodes depending on the position and shape of the electrodes.

[0004] Therefore, in the two-dimensional photonic crystal laser described in Patent Document 1, one of the pair of electrodes (the electrode provided on the surface of the substrate 96) is formed using a window electrode 971 (see Fig. 27 ), the window electrode 971 is provided with a window 975 formed by hollowing out a part of the conductive material of the plate. The electrode 972 on the opposite side of the window electrode 971 is provided on the surface 9421 of the second cladding layer 942 and does not have a window. In this two-dimensional photonic crystal laser, the laser beam emitted to the window electrode 971 side in two directions perpendicular to the two-dimensional photonic crystal layer 92 is not obstructed by the window electrode 971, but is taken out to the outside of the two-dimensional photonic crystal laser 90 through the window 975. On the other hand, the laser beam emitted to the electrode 972 side is directly lost, but if a reflective layer (not shown) is provided on the surface 9421 of the second cladding layer 942, the laser beam can be emitted to the window electrode 971 side. In addition, in Fig. 27 The first cladding layer 941 is marked with reference numeral 941, which cooperates with the second cladding layer 942 to limit the light emission at the active layer 91 to a direction perpendicular to each layer (thereby promoting the amplification of light in the two-dimensional photonic crystal layer 92).

[0005] In the two-dimensional photonic crystal laser described in Patent Document 1, the area of ​​electrode 972 is smaller than the area of ​​window 975. When projected onto window-shaped electrode 971, electrode 972 is entirely arranged at a position inside window 975. Thus, current 98 flowing between window-shaped electrode 971 and electrode 972 is distributed in a cross section ( Fig. 27 When observed in the cross section shown in FIG. 1 , the current flows in a V-shape. Thus, a ring-shaped current distribution is formed in which the current density decreases near the center at a position separated to some extent from the surface 9421 of the second cladding layer 942 in the cross section parallel to the active layer 91 and the two-dimensional photonic crystal layer 92. Therefore, in the two-dimensional photonic crystal laser described in Patent Document 1, an attempt is made to make the current density in the current injection region in the active layer 91, that is, the light emitting region 981, as uniform as possible by configuring the active layer 91 as close as possible to the surface 9421 of the second cladding layer 942.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: International Publication No. WO2007 / 029538

[0009] Patent Document 2: Japanese Patent Application Publication No. 2008-243962

[0010] Patent Document 3: International Publication No. WO2017 / 150387 Summary of the invention

[0011] Problem that the invention aims to solve

[0012] In the two-dimensional photonic crystal laser described in Patent Document 1, even if the active layer is arranged at a position close to the mounting surface as described above, the current density near the center of the light emitting region 981 is smaller than the current density around it. Therefore, the light emission intensity in the active layer 91 also produces unevenness depending on the position. Furthermore, for the laser beam generated in the active layer 91 and oscillated by amplification in the two-dimensional photonic crystal layer 92, the intensity of the light near the center of its cross section is also lower than the intensity of the light around it.

[0013] The problem to be solved by the present invention is to provide a two-dimensional photonic crystal laser that can make the current density distribution in the light emitting region of the active layer closer to uniform than before.

[0014] Solutions for solving problems

[0015] The two-dimensional photonic crystal laser according to the present invention, which has been made to solve the above-mentioned problems, comprises:

[0016] Active layer;

[0017] a two-dimensional photonic crystal layer provided on one surface side of the active layer, wherein different refractive index regions having a refractive index different from that of the base material are periodically arranged two-dimensionally in a plate-like base material; and

[0018] a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged so as to sandwich the active layer and the two-dimensional photonic crystal layer in a stacking direction;

[0019] wherein the first electrode has an opening,

[0020] The projection of the circumscribed circle of the second electrode onto the first electrode is located within the opening,

[0021] At least a portion of a periphery of the opening of the first electrode protrudes into the projection.

[0022] With respect to the two-dimensional photonic crystal laser involved in the present invention, at least a portion of the periphery of the opening of the first electrode extends into the projection of the circumscribed circle of the second electrode onto the first electrode, thereby making it easier to supply current near the center of the light-emitting region of the active layer compared to the two-dimensional photonic crystal laser that used a window-shaped electrode without such an extension. Thus, the current density distribution in the light-emitting region of the active layer can be made nearly uniform. In addition, for the laser beam generated in the light-emitting region, which is oscillated by amplification in the two-dimensional photonic crystal layer and emitted to the outside through the opening (the opening becomes the "window" of the first electrode), the intensity reduction of the light near the center of its cross section can also be suppressed.

[0023] In addition, if the projection of the circumscribed circle of the second electrode onto the first electrode is located entirely outside the opening of the first electrode, current cannot be properly supplied from the sub-region to the vicinity of the center of the light-emitting region in the active layer. Therefore, in the present invention, the projection of the circumscribed circle of the second electrode onto the first electrode is located within the opening of the first electrode. Here, although the projection may be located entirely within the opening, it is sufficient as long as at least a portion of the projection is located within the opening (i.e., the portion other than the portion is located outside the opening).

[0024] In the two-dimensional photonic crystal laser involved in the present invention, it is preferred that the projection of the second electrode onto the first electrode (this projection is called "second projection") is located in the opening of the first electrode, and at least a portion of the periphery of the opening extends into the second projection.

[0025] In this way, not only is the projection of the circumscribed circle of the second electrode onto the first electrode located within the opening of the first electrode, but the projection of the second electrode itself onto the first electrode (second projection) is located within the opening of the first electrode, and at least a portion of the periphery of the opening extends into the second projection, thereby enabling current to be more reliably supplied to the vicinity of the center of the light-emitting area of ​​the active layer.

[0026] In this way, in a structure in which the second projection is located within the opening of the first electrode and at least a portion of the periphery of the opening extends into the second projection, the following structure can be adopted: a non-conductive portion is formed on the second electrode along at least a portion of the projection of the portion of the first electrode extending into the second projection, i.e., the third projection, onto which a non-conductive portion is formed.

[0027] The portion of the first electrode extending into the second projection shields the laser beam emitted from the two-dimensional photonic crystal layer. Therefore, by forming a non-conductive portion in at least a portion of the third projection of the second electrode, the current injected into the portion of the active layer and the two-dimensional photonic crystal layer corresponding to the projection of the portion of the first electrode is suppressed, thereby suppressing the light emission at the portion, thereby preventing the laser beam generated by the light emission at the portion from being shielded by the sub-region 4712 and wasted. As a result, the light emission efficiency can be improved.

[0028] In the two-dimensional photonic crystal laser according to the present invention, the first electrode may include a main region surrounding the projection or the second projection, and a linear sub-region extending from the main region into the projection.

[0029] By using the first electrode having such a linear sub-region, a large amount of current can be easily supplied to the center of the light-emitting region through the sub-region. Although only one sub-region may be provided, it is preferable to provide multiple sub-regions to supply more current to the center of the light-emitting region.

[0030] In addition, in the first electrode having such a linear sub-region, it is preferred to have multiple sub-regions of different lengths. In the case where multiple sub-regions are arranged from the main region toward the opening, when sub-regions of the same length are used, the density of the sub-region near the center of the opening is higher than the density of the surrounding sub-regions. In contrast, by using sub-regions of different lengths to adjust the density of the sub-region near the center of the opening, the current density near the center of the active layer can be adjusted. In addition, the structure having multiple sub-regions of different lengths only needs to include at least two sub-regions of different lengths, and also includes a case where a part of these multiple sub-regions (a number less than the "multiple") of the sub-regions are of the same length. In addition, by using multiple sub-regions of different lengths and different widths, thicknesses and / or materials, or by using multiple sub-regions of different lengths but different widths, thicknesses and / or materials, the current density near the center of the active layer can also be adjusted.

[0031] In the two-dimensional photonic crystal laser according to the present invention, the first electrode can be physically divided into a plurality of electrodes.

[0032] Here, the case where the first electrode is “physically divided” into a plurality of electrodes includes a case where a space is provided between the divided electrodes, a case where an object formed of an insulator or a semiconductor is inserted between them, and the like.

[0033] In the two-dimensional photonic crystal laser involved in the present invention, depending on the extent of the extension of the first electrode into the projection, the current density near the center of the light-emitting region is sometimes larger or smaller than the current density around it compared to the desired current density distribution. In this case, by physically dividing the first electrode into a plurality of electrodes and adjusting the magnitude of the current supplied from these plurality of electrodes, the current density in the light-emitting region can be made close to the desired distribution. In addition, when the temperature in the light-emitting region produces an undesirable spatial distribution during the use of the two-dimensional photonic crystal laser, it is preferred to adjust the magnitude of the current supplied from the plurality of electrodes to suppress the spatial distribution.

[0034] When the first electrode is arranged at a position farther from the active layer than the second electrode, the light-emitting region in the active layer is close to the shape of the second electrode. In this case, regardless of whether the first electrode has an opening, the current density near the center of the light-emitting region is smaller than the current density around the center due to the position of the first electrode, thereby causing the light-emitting intensity near the center to weaken. Therefore, by arranging the first electrode to exist within the projection of the circumscribed circle of the second electrode onto the first electrode, the current density near the center of the light-emitting region can be increased, thereby suppressing the light-emitting intensity near the center from weakening.

[0035] That is, another embodiment of the two-dimensional photonic crystal laser according to the present invention includes:

[0036] Active layer;

[0037] a two-dimensional photonic crystal layer provided on one surface side of the active layer, wherein different refractive index regions having a refractive index different from that of the base material are periodically arranged two-dimensionally in a plate-like base material; and

[0038] a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged so as to sandwich the active layer and the two-dimensional photonic crystal layer in a stacking direction;

[0039] wherein the first electrode is disposed at a position farther from the active layer than the second electrode,

[0040] At least a portion of the first electrode exists within a projection of a circumscribed circle of the second electrode onto the first electrode.

[0041] Effects of the Invention

[0042] According to the two-dimensional photonic crystal laser of the present invention, the current density distribution in the light emitting region of the active layer can be made closer to uniform than before. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a perspective view showing a first embodiment of the two-dimensional photonic crystal laser according to the present invention.

[0044] Figure 2 1 is a plan view showing the structure of a two-dimensional photonic crystal layer in the two-dimensional photonic crystal laser according to the first embodiment.

[0045] Figure 3 This is a plan view showing a projection of the first electrode in the two-dimensional photonic crystal laser according to the first embodiment represented by a solid line and the second electrode represented by a dotted line.

[0046] Figure 4A is Figure 3 The AA cross section in FIG. 1 is a diagram showing a path where current flows in the two-dimensional photonic crystal laser according to the first embodiment.

[0047] Figure 4B is Figure 3 The BB cross section in FIG. 1 is a diagram showing a path where current flows in the two-dimensional photonic crystal laser according to the first embodiment.

[0048] Figure 5 This is a longitudinal sectional view of a two-dimensional photonic crystal laser showing a modification of the first embodiment.

[0049] Figure 6This is a graph showing the results of obtaining the distribution of the current density in the active layer by calculation for the two-dimensional photonic crystal lasers according to the first embodiment and the comparative example.

[0050] Fig. 7A This is a diagram showing the results of calculating the light density distribution in the active layer of the two-dimensional photonic crystal laser according to the first embodiment.

[0051] Figure 7B This is a diagram showing the results of calculating the light density distribution in the active layer of the two-dimensional photonic crystal laser of the comparative example.

[0052] Fig. 8A This is a diagram showing the result of calculating the light density distribution in the cross section of the laser beam obtained by the two-dimensional photonic crystal laser according to the first embodiment.

[0053] Figure 8B This is a diagram showing the results of calculating the light density distribution in the cross section of a laser beam obtained by a two-dimensional photonic crystal laser of a comparative example.

[0054] Fig. 9 It is a perspective view showing a second embodiment of the two-dimensional photonic crystal laser according to the present invention.

[0055] Fig.10 This is a plan view showing a projection of a first electrode in the two-dimensional photonic crystal laser according to the second embodiment, which is shown by a solid line, and a second electrode, which is shown by a dotted line.

[0056] Fig.11 This is a graph showing the results of calculating the distribution of the current density in the active layer of the two-dimensional photonic crystal laser according to the second embodiment and the two-dimensional photonic crystal laser according to the comparative example.

[0057] Fig.12 This is a graph showing the results of calculating the temperature distribution in the active layer of the two-dimensional photonic crystal laser according to the second embodiment and the two-dimensional photonic crystal laser according to the comparative example.

[0058] Fig.13 This is a photograph showing the appearance of the manufactured two-dimensional photonic crystal laser according to the second embodiment.

[0059] Fig.14 This is a graph showing the results of obtaining the distribution of emission intensity through an experiment using the manufactured two-dimensional photonic crystal laser according to the second embodiment.

[0060] Fig.15This is a diagram showing the shape of the cross section of the laser beam for four examples in which the ratio between the first current and the second current is different in the two-dimensional photonic crystal laser according to the second embodiment.

[0061] Fig.16A This is a graph showing examples of the difference in resonant frequency caused by manufacturing errors in the two-dimensional photonic crystal layer, for a case where the current density distribution is not adjusted (dashed line) and a case where the current density distribution is adjusted to alleviate the difference in resonant frequency caused by the position within the two-dimensional photonic crystal layer (with the center of the region where the current is injected as a reference) (solid line) in the two-dimensional photonic crystal laser of the second embodiment.

[0062] Fig. 16B It is shown in Fig.16A Graphs of the normalized current density distribution (normalized current density distribution normalized by the maximum current density value) when the current density distribution is not adjusted and when the current density distribution is adjusted to mitigate the difference in resonant frequency in the example.

[0063] Fig. 16C It is shown in Fig.16A Graphs showing the cross-sectional shape of the laser beam in the example where no adjustment of the current density distribution is performed (left figure) and where adjustment is performed to alleviate the difference in resonance frequency (right figure).

[0064] Fig.17 It is a perspective view showing a third embodiment of the two-dimensional photonic crystal laser according to the present invention.

[0065] Fig.18 This is a plan view showing a projection of a first electrode in the two-dimensional photonic crystal laser according to the third embodiment, which is shown by a solid line, and a second electrode, which is shown by a dotted line.

[0066] Fig.19 It is a perspective view showing a fourth embodiment of the two-dimensional photonic crystal laser according to the present invention.

[0067] Fig. 20 1 and 2 are plan views showing a first electrode (left diagram) and a second electrode (right diagram) in a two-dimensional photonic crystal laser according to a fourth embodiment.

[0068] Fig.21A is a plan view showing a modified example of the first electrode.

[0069] Fig.21B is a plan view showing another modified example of the first electrode.

[0070] Fig. 21C is a plan view showing another modified example of the first electrode.

[0071] Fig.21Dis a plan view showing another modified example of the first electrode.

[0072] Fig.21E is a plan view showing another modified example of the first electrode.

[0073] Fig.21F is a plan view showing another modified example of the first electrode.

[0074] Figure 21G is a plan view showing another modified example of the first electrode.

[0075] Fig. 22 This is a longitudinal sectional view of a two-dimensional photonic crystal laser showing another modified example of the first embodiment.

[0076] Fig.23 It is a plan view showing a modification of the first electrode according to the third embodiment.

[0077] Fig.24 is a plan view showing a modified example of the second electrode.

[0078] Fig.25A is a plan view showing another modification of the second electrode.

[0079] Fig.25B is a plan view showing another modification of the second electrode.

[0080] Fig.25C is a plan view showing another modification of the second electrode.

[0081] Fig.26 This is a top view showing a projection of a first electrode in a two-dimensional photonic crystal laser according to another modification example, shown by a solid line, and a second electrode, shown by a dotted line.

[0082] Fig. 27 This is a longitudinal sectional view showing an example of a conventional two-dimensional photonic crystal laser having a window-shaped electrode. DETAILED DESCRIPTION

[0083] use Figure 1 to Figure 26 An embodiment of the two-dimensional photonic crystal laser according to the present invention will be described.

[0084] (1) First Embodiment

[0085] (1-1) Structure of Two-Dimensional Photonic Crystal Laser of First Embodiment

[0086] like Figure 1As shown, the two-dimensional photonic crystal laser 10 of the first embodiment has a structure in which the first electrode 171, the substrate 16, the first cladding layer 141, the active layer 11, the spacer layer 13, the two-dimensional photonic crystal layer 12, the second cladding layer 142 and the second electrode 172 are stacked in this order. However, the order of the active layer 11 and the two-dimensional photonic crystal layer 12 may be reversed from the above order. Figure 1 In the figure, for convenience, the first electrode 171 is shown as the upper side and the second electrode 172 is shown as the lower side, but the orientation of the two-dimensional photonic crystal laser 10 when used is not limited to the orientation shown in the figure. Next, the structure of each layer and electrode is described.

[0087] The active layer 11 emits light having a predetermined wavelength range when charges are injected from the first electrode 171 and the second electrode 172. As a material for the active layer 11, for example, InGaAs / AlGaAs multiple quantum well (emission wavelength range: 935 nm to 945 nm) can be used.

[0088] like Figure 2 As shown, the two-dimensional photonic crystal layer 12 is obtained by arranging different refractive index regions 122 having a refractive index different from that of the matrix 121 at each lattice point of the two-dimensional lattice in a plate-like matrix 121. Figure 2 In the figure, only a part of the two-dimensional photonic crystal layer 12 is shown in an enlarged manner. In the actual two-dimensional photonic crystal layer 12, many different refractive index regions 122 are arranged in the same range as the outer edge of the first electrode 171. Figure 2 In the example shown, a square lattice is used, but other two-dimensional lattices such as a rectangular lattice and a triangular lattice may also be used. The lattice point period (length) a of the square lattice is appropriately determined according to the material of the base material 121 and the range of the emission wavelength in the active layer 11. For example, p-type GaAs (p-type semiconductor) can be used as the material of the base material 121. For the different refractive index region 122, holes are typically used, but a component having a refractive index different from that of the base material 121 may be used instead of holes.

[0089] In addition, Figure 2In the example shown, a region formed by a combination of two holes, a first different refractive index region 1221 and a second different refractive index region 1222 (a component having a refractive index different from that of the base material 121 may be used instead of the hole) is used as one different refractive index region 122. Here, the first different refractive index region 1221 uses a region whose planar shape is larger than the planar shape of the second different refractive index region 1222, but the two may be set to the same size. By using a different refractive index region formed by a combination of two holes or components like this, it is possible to suppress light from being locally present in a part of the two-dimensional photonic crystal layer 12, thereby causing the laser beam to oscillate from a large range within the two-dimensional photonic crystal layer 12 (see patent documents 2 and 3). In addition, in the present invention, the different refractive index region is not limited to Figure 2 In the example shown, a region with a different refractive index including only one cavity or component or a region with a different refractive index including more than three cavities or components may also be used. Figure 2 In the example shown, a circle is used, but other shapes such as a triangle or a quadrilateral may be used.

[0090] The first cladding layer 141 and the second cladding layer 142 have the function of injecting charges from the first electrode 171 and the second electrode 172, and have the function of suppressing the leakage of the in-plane guided light guided parallel to the two-dimensional photonic crystal layer 12 from the layer. In order to play the former role, for example, the first cladding layer 141 can be made of an n-type semiconductor (e.g., n-type Al 0.37 Ga 0.63 As), the second cladding layer 142 can be made of a p-type semiconductor (e.g., p-type Al 0.37 Ga 0.63 As) (In addition, the reason for using the material of the base material 121 of the two-dimensional photonic crystal layer 12 as a p-type semiconductor is the same as the former role in the second cladding layer 142).

[0091] The spacer layer 13 is provided to prevent the electrons injected from the first electrode 171 from passing through the active layer 11 (thereby combining with the holes at a position closer to the first electrode 171 than the active layer 11) while allowing the holes injected from the second electrode 172 to pass through the spacer layer 13 and be introduced into the active layer 11. The material of the spacer layer 13 can be, for example, p-type Al 0.45 Ga 0.55 As.

[0092] The substrate 16 is thick enough compared to other layers to maintain the overall mechanical strength of the two-dimensional photonic crystal laser 10 and to make the distance between the first electrode 171 and the active layer 11 larger than the distance between the second electrode 172 and the active layer 11. For the same reason as the first cladding layer 141, the material of the substrate 16 is an n-type semiconductor.

[0093] The second electrode 172 is formed of a conductive material and has a circular planar shape. Figure 1 In order to illustrate the shape of the second electrode 172 , the second electrode 172 is depicted as being separated below the second covering layer 142 . However, in reality, the second electrode 172 is in contact with the lower surface of the second covering layer 142 .

[0094] The first electrode 171 is formed of a conductive material, such as Figure 3 As shown, it has a shape composed of a main region 1711 and a sub-region 1712. The main region 1711 has a ring-shaped plane shape obtained by hollowing out the inside of the first circle (the outer edge 17111 of the first electrode 171) with a second circle 17112, and the diameter of the second circle 17112 is smaller than the diameter of the outer edge 17111 and has the same center as the outer edge 17111. The sub-region 1712 has a linear shape extending from the circumference of the second circle 17112 to the inside of the second circle 17112. The portion of the second circle 17112 where the sub-region 1712 does not exist is the opening 175 of the first electrode 171. The opening 175 becomes a window for the laser beam to pass through.

[0095] In the first embodiment, 40 sub-regions 1712 are provided at intervals of 9° so as to extend radially from the center of the second circle 17112. However, no sub-regions 1712 are formed between the center of the second circle 17112 and a predetermined distance, and no sub-regions 1712 exist near the center. Among the 40 sub-regions 1712, 10 sub-regions 1712 provided at intervals of 36° are longer than the other 30 sub-regions 1712 and extend to the position closest to the center of the second circle 17112. In addition, 10 sub-regions 1712 provided at positions deviated by 18° from these 10 sub-regions 1712 are longer than the other 20 sub-regions 1712 and extend to a position closer to the center of the second circle 17112 than these 20 sub-regions 1712. In this way, by providing a plurality of sub-regions 1712 with different lengths inside the main region 1711 , the density of the sub-regions 1712 near the center of the second circle 17112 and near the main region 1711 can be made nearly uniform.

[0096] Since the second electrode 172 is circular, the circumscribed circle of the second electrode 172 is consistent with the second electrode 172 itself. The projection of the circumscribed circle of the second electrode 172 onto the first electrode 171 (the "projection") and the projection of the second electrode 172 itself onto the first electrode 171 (the "second projection") are located within the opening 175. Hereinafter, in the present embodiment, these "projections" and "second projections" are collectively referred to as "projections 1721". A portion of the sub-region 1712 extends from the circumference of the second circle 17112 into the projection 1721. Therefore, a portion of the periphery of the opening 175 also extends into the projection 1721.

[0097] (1-2) Operation of the Two-Dimensional Photonic Crystal Laser of the First Embodiment

[0098] Next, the operation of the two-dimensional photonic crystal laser 10 according to the first embodiment will be described. A predetermined voltage is applied between the first electrode 171 and the second electrode 172, so that a current flows between the two electrodes. Figure 4A and Figure 4B The path of this current is described. Figure 4A Shown in Figure 3 The current path in the AA section is Figure 4B The path of the current in the BB section is shown in FIG. The AA section is a section perpendicular to each layer of the two-dimensional photonic crystal laser 10 and passes through the center of the second circle 17112 but not through the sub-region 1712. The BB section is a section perpendicular to each layer of the two-dimensional photonic crystal laser 10 and passes through the center of the second circle 17112 and the sub-region 1712.

[0099] like Figure 4A As shown in FIG. 1 , in the AA cross section, there is no sub-region 1712, so the current 98 flows between the main region 1711 of the first electrode 171 and the second electrode 172. In this cross section, at the position of the active layer 11, in the region where the current 18 is injected, that is, the light emitting region 181, the current density of the current supplied to the center of the light emitting region 181 is smaller than the current density of the surroundings. On the other hand, as shown in FIG. Figure 4B As shown, the sub-region 1712 exists in the BB cross section, thereby the current density of the current supplied to the center of the light-emitting region 181 can be made higher than that in the AA cross section. Therefore, by providing the sub-region 1712 (a portion of the first electrode 171 extending into the projection 1721) in the first electrode, the current density near the center of the light-emitting region 181 can be made higher than that in the case where the sub-region 1712 does not exist, and the current density of the entire light-emitting region 181 can be made close to uniform.

[0100] By injecting current into the light emitting region 181 of the active layer 11 in this manner, light having a wavelength within a predetermined wavelength range corresponding to the material of the active layer 11 is generated from the light emitting region 181. The intensity of the light emission is also nearly uniform in the entire light emitting region 181 in accordance with the current density. The light emission generated in this way is selectively amplified by resonance of light of a resonance wavelength corresponding to the period length of the square lattice in the two-dimensional photonic crystal layer 12, thereby performing laser oscillation.

[0101] The oscillated laser beam is emitted from both surfaces of the two-dimensional photonic crystal layer 12 in a direction perpendicular to the two-dimensional photonic crystal layer 12. The laser beam emitted toward the first electrode 171 side passes through the opening 175 and is taken out to the outside of the two-dimensional photonic crystal laser 10. On the other hand, the laser beam incident on the second electrode 172 among the laser beams emitted toward the second electrode 172 side is reflected by the second electrode 172 and goes toward the first electrode 171 side, passes through the opening 175 and is taken out to the outside of the two-dimensional photonic crystal laser 10. The laser beam that reaches the periphery of the second electrode 172 among the laser beams emitted toward the second electrode 172 side passes through the lower surface of the second cladding layer 142. If a reflection portion (not shown) for reflecting the laser beam is pre-arranged around the second electrode 172, the laser beam is reflected by the reflection portion and goes toward the first electrode 171 side, passes through the opening 175 and is taken out to the outside of the two-dimensional photonic crystal laser 10.

[0102] Corresponding to the distribution of luminous intensity in the luminous region 181, in the cross section of the laser beam taken out to the outside of the two-dimensional photonic crystal laser 10, the light intensity distribution is also close to a single peak (a distribution with the largest value at the center and gradually decreasing as it moves away from the center) compared to the case where the sub-region 1712 does not exist.

[0103] Preferably, in the first electrode 171, the area included in the inner side of the projection 1721 is larger than the area included in the outer side of the projection 1721. Thus, it is possible to avoid the current density from being concentrated near the outer edge of the light-emitting region 181, thereby improving the uniformity of the current density in the light-emitting region 181. In this case, it is also possible that, instead of directly forming the conductive material constituting the first electrode 171 on the upper surface of the substrate 16, an insulating film 1718 made of an insulating material is formed on the upper surface of the substrate 16, and then a conductive material ( Figure 5 When such an insulating film is provided, in the region where the conductive material is provided, only the portion where the insulating film 1718 is not provided functions as the first electrode 171, so that the inner and outer areas of the projection 1721 in the first electrode 171 can be adjusted by the insulating film.

[0104] exist Figure 6In the figure, the results of calculating the current density in the active layer for the two-dimensional photonic crystal laser of the first embodiment and the comparative example are shown in a graph. In the calculation of the first embodiment, the distance between the first electrode 171 and the active layer 11 (in the direction perpendicular to the active layer 11) is set to 0.15 mm, and the distance between the second electrode 172 and the active layer 11 (in the direction perpendicular to the active layer 11) is set to 3.7 μm. That is, the first electrode 171 is arranged at a position farther from the active layer 11 than the second electrode 172. At a position outside the projection 1721, the above-mentioned insulating film is provided between the first electrode 171 and the substrate 16 throughout the entire conductive material constituting the first electrode 171. The diameter of the second electrode 172 is set to 3 mm, and the diameter of the second circle 17112 is set to 3.4 mm. In addition, regarding the length of the sub-region 1712, the length of the longest 10 sub-regions 1712 is set to 1.65mm, the length of the second longest 10 sub-regions 1712 is set to 1.50mm, and the length of the shortest 20 sub-regions 1712 is set to 1.25mm. Regarding the width of the sub-region 1712, the width of the longest 10 sub-regions 1712 and the second longest 10 sub-regions 1712 is set to 0.017mm, and the width of the shortest 20 sub-regions 1712 is set to 0.013mm. In addition, calculations were performed for three cases where the thickness of the sub-region 1712 was 10μm, 20μm, and 30μm. As a comparative example, calculations were performed for a two-dimensional photonic crystal laser having a structure in which the sub-region 1712 was removed from the two-dimensional photonic crystal laser 10 of the first embodiment (the structure other than this is the same as the first embodiment). The first embodiment and the comparative example are both set to apply a voltage of 1.6V between the first electrode 171 and the second electrode 172 and perform calculations. The calculation results are shown with the value at a position 1.5 mm away from the center of the light emitting region (a position directly above the outer edge of the second electrode 172 ) being normalized to “1”.

[0105] according to Figure 6 In the graph of FIG. 1 , in the comparative example, the value obtained by dividing the current density at the outer edge of the light-emitting region (the horizontal axis value of the graph is ±1.5 mm) by the current density at the center of the light-emitting region (the horizontal axis value of the graph is 0 mm) is less than 0.2, while in the first embodiment, it is 0.9 to 1.2 (if taken to the second decimal place, it is 0.94 to 1.17), which is a value higher than the value in the comparative example. This result shows that the uniformity of the current density in the light-emitting region of the first embodiment is higher than that of the comparative example.

[0106] In addition, if the three calculation results of the first embodiment are compared, it can be seen that the greater the thickness of the sub-region 1712, the greater the current density in the center of the light-emitting region. This is because, when the width of the sub-region 1712 is the same, the greater the thickness, the smaller the resistance, and more current flows in the sub-region 1712.

[0107] To summarize further, the lower the resistance of the portion within the projection 1721 of the first electrode 171, the higher the current density at the center of the light-emitting region can be. Specifically, the thickness or width of the sub-region 1712 within the projection 1721 can be increased or the number of sub-regions 1712 can be increased.

[0108] Next, assuming that the thickness of the sub-region 1712 in the first embodiment is 10 μm and that of the comparative example, the light density distribution in the active layer and the light density distribution in the cross section of the emitted laser beam are calculated. Fig. 7A The optical density distribution in the active layer is shown in FIG. Figure 7B The light density distribution in the active layer is shown in FIG. Fig. 8A The light density distribution in the cross section of the laser beam is shown in FIG. Figure 8B The light density distribution in the cross section of the laser beam is shown in . Compared with the comparative example, in the first embodiment, the difference between the light density near the center and the light density near the end is small in both the active layer and the cross section of the laser beam, and a nearly uniform light density distribution is obtained.

[0109] (2) Second Embodiment

[0110] (2-1) Structure of Two-Dimensional Photonic Crystal Laser of Second Embodiment

[0111] exist Fig. 9 The structure of the two-dimensional photonic crystal laser 20 of the second embodiment is shown in FIG. The two-dimensional photonic crystal laser 20 of the second embodiment has the same structure as the two-dimensional photonic crystal laser 10 of the first embodiment, except that the structures of the first electrode 271 and the opening 275 are different from the structures of the first electrode 171 and the opening 175 of the first embodiment. Therefore, the components other than the first electrode 271 and the opening 275 are marked with the same reference numerals as the components in the first embodiment, and the description is omitted. Below, the structure of the first electrode 271 and the opening 275 is described.

[0112] like Fig.10As shown, the first electrode 271 has a shape composed of a main region 2711, a first sub-region 2712, and a second sub-region 2713. The main region 2711 has a planar shape obtained by hollowing out the inner side of the first circle (the outer edge 27111 of the first electrode 271) with a second circle 27112, and the diameter of the second circle 27112 is smaller than the diameter of the outer edge 27111 and has the same center as the outer edge 27111. The first sub-region 2712 has a linear shape extending from the periphery of the second circle 27112 to the inside of the second circle 27112. Twelve first sub-regions 2712 are arranged at intervals of 30° in a manner extending radially from the center of the second circle 27112, but no first sub-region 2712 is formed between the center and a specified distance. Fig.10 In the example shown, all first sub-areas 2712 have the same length, but a length of Fig.13 As shown, there are a plurality of first sub-regions 2712 with different lengths. The main region 2711 and the first sub-regions 2712 are physically integrated.

[0113] The second sub-region 2713 is arranged within the second circle 27112 and is formed of a linear conductor physically separated from the main region 2711 and the first sub-region 2712. Twelve second sub-regions 2713 are provided at intervals of 30° at positions deviated from the first sub-region 2712 by 15° in a manner extending radially from the center of the second circle 27112. The length of the second sub-region 2713 is shorter than that of the first sub-region 2712, and the second sub-region 2713 is arranged at a position close to the circumference of the second circle 27112. In the present embodiment, a portion of each of the first sub-region 2712 and the second sub-region 2713 is located within the projection (and second projection) 1721 of the second electrode 172 onto the first electrode 271, but either the first sub-region 2712 or the second sub-region 2713 may be arranged outside the projection 1721. In addition, in the present embodiment, all the second sub-regions 2713 have the same length, but a plurality of second sub-regions having different lengths may be used. The length of the second sub-region 2713 may be the same as or longer than the first sub-region 2712 .

[0114] The plurality of conductors of the second sub-region 2713 are electrically connected to the plurality of electrode pads 2731 embedded in the main region 2711 in a one-to-one correspondence. Each electrode pad 2731 is separated from the main region 2711 by a groove (air) 2732. Some (two or more) or all of the plurality of second sub-regions 2713 may be electrically connected to each other. Instead of the groove (air) 2732, an insulating material formed of an insulator or a material formed of a semiconductor having a higher resistance than that of a conductor may be used.

[0115] In the second embodiment, a portion of the second circle 27112 excluding the first sub-region 2712 and the second sub-region 2713 serves as the opening 275 .

[0116] (2-2) Operation of Two-Dimensional Photonic Crystal Laser According to Second Embodiment

[0117] Next, the operation of the two-dimensional photonic crystal laser 20 of the second embodiment is described. A predetermined voltage (referred to as "first voltage") is applied between the main region 2711 and the first sub-region 2712 of the first electrode 271, and a predetermined voltage (referred to as "second voltage") is also applied between the second sub-region 2713 of the first electrode 271 and the second electrode 172. Thus, a first current I1 flows between the main region 2711 and the first sub-region 2712 and the second electrode 172, and a second current I2 flows between the second sub-region 2713 and the second electrode 172. In addition, the first voltage and the second voltage can be set to different values ​​(or the same value). In addition, only one of the first voltage and the second voltage can be applied.

[0118] The first sub-region 2712 of the first electrode 271 extends into the projection 1721 of the circumscribed circle of the second electrode (or the second electrode itself), so the current density formed near the center of the active layer 11 by the first current I1 is greater than the current density when the first sub-region 2712 does not exist, and the current density near the center of the active layer 11 may be higher than the current density around. On the other hand, the second sub-region 2713 is only configured to a position outside the first sub-region 2712, so the second current I2 has a greater tendency to form a current density distribution in which the current density near the center is smaller than the current density around the first current I1. Therefore, in the case of a current density distribution in which the current density near the center of the active layer 11 is higher than the current density around the first current I1, the values ​​of the first voltage and the second voltage are adjusted to increase the proportion of the current density distribution formed by the second current I2, thereby being adjusted to make the current density distribution obtained by combining these first current I1 and second current I2 close to uniform.

[0119] Alternatively, when a non-uniform temperature distribution is generated during use of the two-dimensional photonic crystal laser 20 , the current density distribution may be adjusted by adjusting the values ​​of the first voltage and the second voltage so as to make the temperature distribution close to uniform.

[0120] In addition, due to manufacturing errors when making the two-dimensional photonic crystal layer 12, the spacing (lattice point spacing) of the different refractive index regions 122 and the size of the different refractive index regions 122 sometimes differ by position. Or, sometimes an uneven temperature distribution is generated during the use of the two-dimensional photonic crystal laser 20. In these cases, there is the following situation: the resonant frequency (resonant wavelength) of light at each position in the two-dimensional photonic crystal layer 12 differs by position (frequency distribution), so that a part of the position does not contribute to the laser oscillation or produces multi-mode oscillation, causing the shape of the laser beam to be disordered. In such a case, by adjusting the current density distribution by changing the voltage applied from the multiple electrode pads 2731 respectively, it is possible to reduce the influence of the frequency distribution in the two-dimensional photonic crystal layer 12 and improve the shape of the laser beam.

[0121] By adjusting the current density distribution in the active layer 11 in this way, the distribution of the luminous intensity in the active layer 11 can be nearly uniform. In addition, the intensity distribution of the light generated in the active layer 11 in the cross section of the laser beam generated by amplifying the light in the two-dimensional photonic crystal layer 12 is also nearly uniform.

[0122] exist Fig.11 In the figure, the result obtained by calculating the current density in the active layer 11 for the two-dimensional photonic crystal laser 20 of the second embodiment is shown in a graph. Here, when the first current I1 and the second current I2 are combined to flow a current of 100A, calculations are performed for 6 cases with different ratios of the first current I1 to the second current I2. As a result, when the first current I1 is 80A and the second current I2 is 20A, the current density of the entire light emitting area is closest to uniformity.

[0123] exist Fig.12 The following figure shows the situation in which the two-dimensional photonic crystal laser 20 of the second embodiment is operated continuously. Fig.11 The temperature distribution near the active layer 11 was calculated for six cases with different ratios of the first current I1 to the second current I2. The result was that when the first current I1 was 60A and the second current I2 was 40A (at Fig.12 The temperature distribution is closest to uniform.

[0124] If an uneven temperature distribution is generated in the light emitting region, a refractive index distribution is generated in the two-dimensional photonic crystal layer 12, and the oscillation mode may become unstable. In contrast, by adjusting the ratio of the first current I1 to the second current I2 during continuous operation, the temperature distribution is made close to uniform, thereby obtaining stable laser oscillation.

[0125] Next, the results of manufacturing a two-dimensional photonic crystal laser according to the second embodiment and measuring the emission intensity in the active layer 11 are described. Fig.13 The appearance of the manufactured two-dimensional photonic crystal laser is shown in FIG. In the two-dimensional photonic crystal laser, 20 first sub-regions (sub-regions that are not physically separated from the main region 2711) 2712 are arranged at intervals of 18°. Among these first sub-regions, 10 first sub-regions 2712 arranged at intervals of 36° extend to a position closer to the center of the second circle 27112 than the other 10 first sub-regions 2712. 20 second sub-regions (sub-regions that are physically separated from the main region 2711) 2713 are arranged at intervals of 18°. Each second sub-region 2713 is arranged between two adjacent first sub-regions 2712 in a manner that the distance from the two first sub-regions 2712 is equal.

[0126] exist Fig.14 The measurement results of the luminous intensity in the active layer 11 of the manufactured two-dimensional photonic crystal laser are shown in FIG. The measurement was performed for three cases where a current of 20A was passed by merging the first current I1 and the second current I2, and the ratio of the first current I1 to the second current I2 was different. As a result, when the first current I1 was 17.5A and the second current I2 was 2.5A, the current density of the entire luminous area was closest to uniform, and a roughly flat current density distribution was obtained throughout the entire luminous area.

[0127] exist Fig.15 The cross-sectional shape of the laser beam emitted from the fabricated two-dimensional photonic crystal laser 20 is shown in FIG. Here, experiments were conducted for four cases where a current of 90A was passed by combining the first current I1 and the second current I2, and the ratio of the first current I1 to the second current I2 was different. Fig.15 As can be seen from the four photos shown, if the ratio of the first current I1 to the second current I2 is changed, the cross-sectional shape of the beam changes. For example, when the first current I1 shown in the upper left of the figure is 40.5A and the second current I2 is 49.5A, a laser beam with a ring-shaped and slightly expanded cross-sectional shape near the center is darker than the surrounding area. If the first current I1 is increased and the second current I2 is reduced from this state, the cross-sectional shape changes to a single peak shape near the center that is brighter than the surrounding area, and the expansion of the cross section also becomes smaller.

[0128] Next, an example is shown in which the current density distribution is adjusted when the resonant frequency distribution of light is generated in the two-dimensional photonic crystal layer 12 due to manufacturing errors such as the lattice point spacing and the size of the different refractive index region 122. Fig.16AAn example of such a frequency distribution is shown in FIG. In this figure, the current density distribution in a longitudinal section where a current is injected into a circular area (current injection area) in the active layer 11 and passes through the center of the current injection area is shown. The dotted line in this figure shows the frequency distribution generated when the same voltage is applied (the same potential is given) from multiple electrode pads 2731 (no adjustment of the current density distribution is performed), and the dotted line shows the tendency of the frequency to decrease from one end of the current injection area in the longitudinal section toward the other end (if the numerical value of the position shown in the figure is used, it is from the negative side to the positive side).

[0129] Therefore, the voltage applied from each electrode pad 2731 is adjusted so that the current density on the other end side is smaller than that in the case where the current density distribution is not adjusted, and the difference between the current density and the current density in this case becomes larger from the one end toward the other end ( Fig. 16B ). As a result, Fig.16A As shown by the solid line in the figure, the frequency distribution is closer to being uniform than when the current density distribution is not adjusted.

[0130] Moreover, regarding the cross-sectional shapes of the laser beams in both cases, as Fig. 16C As shown in FIG. 1 , when the current density distribution is adjusted, the shape becomes closer to a circle corresponding to the shape of the current injection region, compared to when the current density distribution is not adjusted.

[0131] (3) Third Embodiment

[0132] exist Fig.17 The structure of the two-dimensional photonic crystal laser 30 of the third embodiment is shown in FIG. The two-dimensional photonic crystal laser 30 of the third embodiment has the same structure as the two-dimensional photonic crystal laser 10 of the first embodiment, except that the structure of the first electrode 371 is different from the first electrode 171 of the first embodiment. Therefore, the components other than the first electrode 371 are marked with the same reference numerals as the components of the first embodiment, and the description is omitted. Next, the structure of the first electrode 371 is described.

[0133] like Fig.18 As shown in FIG. 1 , the first electrode 371 is formed by radially arranging a plurality of linear conductive materials. A portion of the conductive materials of the first electrode 371, specifically, a portion of the inner side of the radially arranged conductive materials, is arranged within a projection 1721 of the second electrode 172 onto the first electrode 371. The first electrode 371 does not have an area corresponding to the main area, sub-area, and opening in the first and second embodiments.

[0134] A distance L1 between the first electrode 371 and the surface of the active layer 11 on the first electrode 371 side is set longer than a distance L2 between the second electrode 171 and the surface of the active layer 11 on the second electrode 172 side. That is, the first electrode 371 is arranged farther from the active layer 11 than the second electrode 172.

[0135] The operation of the two-dimensional photonic crystal laser 30 of the third embodiment is described. A current flows between the first electrode 371 and the second electrode 172 by applying a predetermined voltage between the two electrodes. Here, since the first electrode 371 is arranged at a position farther from the active layer 11 than the second electrode 172, the area close to the shape of the second electrode 172 in the active layer 11 becomes a current injection area and a light emitting area. In this embodiment, a part of the conductive material of the first electrode 371 is arranged within the projection 1721 of the second electrode 172 onto the first electrode 371, thereby increasing the current density near the center of the current injection area of ​​the active layer 11. As a result, it is possible to suppress the luminous intensity from weakening near the center of the light emitting area, and it is also possible to suppress the intensity of light near the center from weakening in the cross section of the laser beam obtained by amplification in the two-dimensional photonic crystal layer 12.

[0136] (4) Fourth Embodiment

[0137] exist Fig.19 The structure of the two-dimensional photonic crystal laser 40 of the fourth embodiment is shown in FIG. The two-dimensional photonic crystal laser 40 of the fourth embodiment has the same structure as the two-dimensional photonic crystal laser 10 of the first embodiment, except that the structures of the first electrode 471 and the second electrode 472 are different from the first electrode 171 of the first embodiment. Therefore, the components other than the first electrode 471 and the second electrode 472 are marked with the same reference numerals as the components of the first embodiment, and the description is omitted. The main region 4711 of the first electrode 471 has the same structure as the main region 1711 of the first embodiment, and the linear sub-region 4712 has a structure extending from the main region 4711 to a position closer to the inside than the projection (second projection) 4720 of the circumscribed circle of the second electrode 472, except for its length and width, like the sub-region 1712 of the first embodiment. In addition, the first electrode 171 of the first embodiment can also be directly used for the two-dimensional photonic crystal laser 40 of the fourth embodiment. Below, the structure of the second electrode 472 is centered for description.

[0138] exist Fig. 204 shows the structure of the first electrode 471 and the second electrode 472 in a plan view. The second electrode 472 has a non-conductive portion 4722 formed by cutting off a portion of a plate-like conductor, and a conductive portion 4721 other than the non-conductive portion 4722. The non-conductive portion 4722 is provided in a region corresponding to a third projection, which is a projection of a portion of the first electrode 471 extending to the second projection 4720, that is, a portion of the sub-region 4712 that is closer to the inside than the second projection 4720, onto the second electrode 472. In addition, the non-conductive portion 4722 may be formed by forming a film of an insulating material on a portion of the plate-like conductor corresponding to the non-conductive portion 4722, instead of cutting off a portion of the conductor.

[0139] The laser beam amplified and emitted in the two-dimensional photonic crystal layer 12 passes through the opening 475 of the first electrode 471, and on the other hand, is shielded by the sub-region 4712. Therefore, in this embodiment, by setting the region corresponding to the third projection in the second electrode 472 as the non-conductive portion 4722, the current injected into the portion corresponding to the projection of the sub-region 4712 in the active layer 11 and the two-dimensional photonic crystal layer 12 is suppressed, thereby suppressing the light emission in this portion. As a result, it is possible to suppress the laser beam generated by the light emission in this portion from being shielded by the sub-region 4712 and wasted, and the light emission efficiency can be improved.

[0140] In the fourth embodiment, the non-conductive portion 4722 has the same shape, size and position as the third projection as a whole, but if the non-conductive portion 4722 is formed on at least a portion of the third projection, the effect of improving the light emitting efficiency is achieved. In addition, in the fourth embodiment, the first electrode 471 obtained by combining the main region 4711 and the linear sub-region 4712 is used, but instead, when a first electrode having an opening where the second projection is located and at least a portion of the periphery of the opening protrudes into the second projection is used, if at least a portion of the projection of the protruding portion to the second electrode is set as a non-conductive portion, the same effect as the fourth embodiment is achieved.

[0141] (5) Modification

[0142] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0143] For example, in the first embodiment and the second embodiment, the first electrodes 171 are arranged at equal intervals (in Figure 3 The interval is 9°, Fig.10In the embodiment, a plurality of sub-regions 1712, a first sub-region 2712, and a second sub-region 2713 are respectively provided at intervals of 36°, but they may also be provided at unequal intervals. In addition, a plurality of sub-regions having different widths, thicknesses, and materials may also be used. Furthermore, in the first embodiment and the second embodiment, a plurality of sub-regions are provided on the first electrodes 171 and 271, but only one sub-region may be provided. The conductive material of the first electrode 371 in the third embodiment and the first electrode 471 in the fourth embodiment may also be arranged at unequal intervals, or only one may be provided.

[0144] In the above embodiment, the sub-region 1712, the first sub-region 2712, the second sub-region 2713, and the sub-region 4712 having a linear shape are used, but sub-regions having shapes other than these may also be used. Fig.21A As shown in FIG. 1 , the first electrode 171A includes a sub-region 1712A having a strip-shaped shape whose width varies depending on the position, as shown in FIG. Fig.21B As shown in the figure, the first electrode 171B has a curved sub-region 1712B. Alternatively, a sub-region with different thickness and material depending on the position can be used. In addition, a sub-region with various shapes such as a triangle or a part of a polygon, a circle or an ellipse or a part of them can be used.

[0145] Alternatively, you can use Fig. 21C As shown in the figure, a first electrode 171C is provided with a sub-region 1712C composed of a first sub-region 1712C1 and a plurality of second sub-regions 1712C2 arranged concentrically in an annular shape, wherein the first sub-region 1712C1 extends from the periphery of the second circle 17112C of the main region 1711C to the inside of the second circle 17112C, and the second sub-regions 1712C2 are respectively connected to the first sub-region 1712C. In this case, the number of the first sub-regions 1712C1 may be multiple, and the number of the second sub-regions 1712C2 may be only one. In addition, the second sub-region 1712C2 is not limited to an annular region, and a quadrilateral frame-shaped region or the like may also be used.

[0146] Alternatively, you can use Fig.21D As shown in FIG. 17 , the main region 1711D is divided into a first electrode 171D of a plurality of electrodes. Fig.21DIn the example of the embodiment, the first electrode 171 is divided into a plurality of parts by adding radially extending slits 17113 at equal intervals in the circumferential direction to the main region 1711 of the first electrode 171 of the first embodiment. In addition, the slits 17113 may be added at unequal intervals. The portion of the inner side of the annular region formed by the main region 1711D and the slits 17113, excluding the sub-region 1712, corresponds to the opening (window) 175D.

[0147] Alternatively, you can use Fig.21E As shown in the figure, after the main region 1711 of the first electrode 171 of the first embodiment is divided into two in the radial direction by adding a slit 17114 in the circumferential direction, the first electrode 171E is obtained by adding radially extending slits 17115 at equal intervals in the circumferential direction to the two electrodes. In addition, the slits 17115 can also be added at unequal intervals in either or both of the two electrodes. The first electrode 171E has an inner main region 1711E1 and an outer main region 1711E2, wherein the inner main region 1711E1 is arranged at a radially inner position in a manner of being divided into a plurality of parts, and the outer main region 1711E2 is arranged at a radially outer position than the inner main region 1711E1 in a manner of being divided into a plurality of parts. A first sub-region 1712E1 is provided from the inner main region 1711E1 divided into a plurality of regions toward the center of the circle (but not reaching the center), and a second sub-region 1712E2 is provided from the outer main region 1711E2 divided into a plurality of regions toward the center of the circle (but not reaching the center). The second sub-region 1712E2 passes through the slit 17115 provided in the inner main region 1711E1, and the front end thereof extends into the projection 1721 of the circumscribed circle of the second electrode 172. In the region inside the inner main region 1711E1, the portion where the first sub-region 1712E1 and the second sub-region 1712E2 are not provided corresponds to the opening (window) 175E.

[0148] Alternatively, the first electrode 171F ( Fig.21F ), the sub-region 1712G is a first electrode 171G ( Figure 21G )wait.

[0149] In the second embodiment, the first sub-region 2712 and the second sub-region 2713 are alternately provided, but a plurality of first sub-regions 2712 or second sub-regions 2713 may be provided continuously. In addition, in the second embodiment, the first sub-region 2712 is not physically separated from the main region 2711, but the first sub-region 2712 may be physically separated from the main region 2711 like the second sub-region 2713, and the voltage application is controlled independently of each other for the main region 2711, the first sub-region 2712, and the second sub-region 2713. In addition, the first electrode may be divided into four or more electrodes, and the voltage application is controlled independently of each other for each electrode. For example, the plurality of second sub-regions 2713 in the second embodiment can be regarded as respectively independent divided electrodes, and the voltage application is controlled independently of each other for the main region 2711 and the first sub-region 2712 and these plurality of second sub-regions 2713.

[0150] In a part of the first embodiment, an insulating film 1718 is provided between the conductive material of the first electrode 171 and the substrate 16 in a region outside the projection 1721 of the second electrode 172, but such an insulating film may be used in other embodiments and modified examples. When an insulating film is provided in the opening (window), a material transparent to the laser beam is used as the insulating material of the insulating film.

[0151] The second electrode 172 can also be formed by forming an insulating film 1728 on the portion of the lower surface of the second cladding layer 142 where the second electrode 172 is not provided, and then forming a conductive material on the entire lower surface of the second cladding layer 142 and the lower surface of the insulating film 1728 (see Figure 5 The conductive material after film formation can function as a reflector 1727 that reflects the laser beam. The insulating material used as the insulating film 1728 can be either a transparent material or an opaque material to the laser beam.

[0152] The following structure may be used instead of the insulating film 1718 on the first electrode 171 side and / or the insulating film 1728 on the second electrode 172 side. For example, in the above example, a component that does not form an ohmic contact with the first electrode 171 and / or the second electrode 172, or a component having a high contact resistance with these electrodes, may be provided at the position where the insulating film 1718 and / or the insulating film 1728 are provided. Alternatively, instead of the insulating film 1718, an opposite polarity region 1718A (see Fig. 22). Similarly, instead of the insulating film 1728, an opposite polarity region 1728A formed of an n-type semiconductor having a polarity opposite to that of the p-type semiconductor constituting the second cladding layer 142 may be provided in a portion in the thickness direction of the second cladding layer 142 and outside the projection 1721 (see Fig. 22 ). These opposite polarity regions 1718A and opposite polarity regions 1728A hinder the conduction of electrons conducted in the substrate 16 or the first cladding layer 141 and the conduction of holes conducted in the second cladding layer 142, thereby playing the same role as an insulating film. Alternatively, instead of forming the opposite polarity regions 1718A and / or 1728A, it is also possible to insulate by injecting ions (e.g., hydrogen ions) at the same position as them. In addition, the various methods cited in this paragraph can also be used in the fourth embodiment when forming a non-conductive portion on the second electrode.

[0153] The shape of the opening of the main region of the first electrode is circular in the above embodiment, but is not limited thereto and may be, for example, a square, a regular hexagonal region, or an amorphous shape.

[0154] In the third embodiment, the first electrode 371 is formed so that a portion of the first electrode 371 is arranged within the projection 1721 of the second electrode 172 onto the first electrode 371. However, for example, Fig.23 As shown, the first electrode 371A is entirely arranged within the projection 1721 .

[0155] The shape of the outer edge of the first electrode and the second electrode is not limited to the circular shape in the above-mentioned embodiment, and may also be a square, a regular hexagon or an amorphous shape. In the case where the second electrode is a shape other than a circle, the shape of the circumscribed circle of the second electrode is inconsistent with the shape of the second electrode itself (for example, refer to Fig.24 The square second electrode 172S and its circumscribed circle 1723S shown in the figure are not included, but at least the projection of the circumscribed circle onto the first electrode is located within the opening of the first electrode, and at least a portion of the periphery of the opening extends into the projection. In addition, in this case, it is preferred that the projection of the second electrode itself onto the first electrode, i.e., the second projection, is located within the opening of the first electrode, and at least a portion of the periphery of the opening extends into the second projection.

[0156] The shape and size of the light-emitting region in the active layer depend on the shape and size of the outer edges of the first electrode and the second electrode, but it is preferred that the shape and size of the outer edges of the first electrode and the second electrode be set so that the diameter of the inscribed circle of the light-emitting region is greater than 1 mm. According to the present invention, the current density distribution can be made nearly uniform over the entire large light-emitting region where the diameter of the inscribed circle is greater than 1 mm.

[0157] In the above embodiment, the second electrode 172 formed of one conductor is used, but a second electrode divided into a plurality of conductors may be used. Fig.25A The second electrode 172A may be obtained by dividing the conductor into a plurality of concentric circles as shown in FIG. 1 , or the second electrode 172B may be obtained by arranging the divided conductor into a square lattice (or other lattice). In these examples, the divided conductors are electrically independent of each other, so the current density distribution in the active layer 11 can be controlled by controlling the current flowing from each conductor. Fig.25C In the second electrode 172C shown, a conductor 172C1 divided into a plurality of concentric circles is electrically connected to a conductor 172C2 extending radially. In this case, although the current flowing from each conductor cannot be controlled, the current density distribution in the active layer 11 can be adjusted by the difference in the arrangement of the conductors 172C1 and 172C2.

[0158] In the above embodiment, the first electrode is formed by combining the main region and the sub-region, but the first electrode is not limited to such a shape. Fig.26 As shown, the first electrode 171H is provided so that the inner edge 17112H of the ring-shaped conductive material 1711H is located inside the projection (or second projection) 1721 of the second electrode 172. In this case, the area inside the edge 17112H becomes the opening (window) 175H.

[0159] [Way]

[0160] It is obvious to those skilled in the art that the above-mentioned exemplary embodiments are specific examples of the following aspects.

[0161] (First) A two-dimensional photonic crystal laser according to one embodiment of the present invention is characterized by comprising:

[0162] Active layer;

[0163] a two-dimensional photonic crystal layer provided on one surface side of the active layer, wherein different refractive index regions having a refractive index different from that of the base material are periodically arranged two-dimensionally in a plate-like base material; and

[0164] a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged so as to sandwich the active layer and the two-dimensional photonic crystal layer in a stacking direction;

[0165] wherein the first electrode has an opening,

[0166] The projection of the circumscribed circle of the second electrode onto the first electrode is located within the opening,

[0167] At least a portion of a periphery of the opening of the first electrode protrudes into the projection.

[0168] (Second Item) The two-dimensional photonic crystal laser involved in the second item is characterized in that, in the two-dimensional photonic crystal laser involved in the first item, the first electrode has a main region surrounding the projection and a linear sub-region extending from the main region into the projection.

[0169] (Item 3) The two-dimensional photonic crystal laser involved in the third item is characterized in that, in the two-dimensional photonic crystal laser involved in the first item, the projection of the second electrode onto the first electrode, i.e., the second projection, is located within the opening, and at least a portion of the periphery of the opening extends into the second projection.

[0170] (Item 4) The two-dimensional photonic crystal laser involved in the fourth item is characterized in that, in the two-dimensional photonic crystal laser involved in the third item, a non-conductive portion is formed on the second electrode as at least a portion of the projection of the portion of the first electrode extending into the second projection onto the second electrode, i.e., the third projection.

[0171] (Item 5) The two-dimensional photonic crystal laser involved in Item 5 is characterized in that, in the two-dimensional photonic crystal laser involved in Item 3 or Item 4, the first electrode has a main region surrounding the second projection and a linear sub-region extending from the main region into the second projection.

[0172] (Item 6) The two-dimensional photonic crystal laser involved in Item 6 is characterized in that, in the two-dimensional photonic crystal laser involved in Item 2 or Item 5, it has a plurality of sub-regions having different lengths, widths, thicknesses and materials or two or more thereof.

[0173] (Item 7) The two-dimensional photonic crystal laser according to Item 7 is characterized in that, in the two-dimensional photonic crystal laser according to any one of Items 1 to 6, the first electrode is physically divided into a plurality of electrodes.

[0174] (Item 8) The two-dimensional photonic crystal laser involved in Item 8 is characterized in that, in the two-dimensional photonic crystal laser involved in any one of Items 1 to 7, the area of ​​the inner part of the projection in the first electrode is larger than the area of ​​the outer part of the projection.

[0175] (Item 9) The two-dimensional photonic crystal laser involved in Item 9 is characterized in that, in the two-dimensional photonic crystal laser involved in any one of Items 1 to 8, the different refractive index region is a region obtained by combining two components having a hole or a refractive index different from the refractive index of the base material.

[0176] (Item 10) The two-dimensional photonic crystal laser according to Item 10 is characterized in that it has:

[0177] Active layer;

[0178] a two-dimensional photonic crystal layer provided on one surface side of the active layer, wherein different refractive index regions having a refractive index different from that of the base material are periodically arranged two-dimensionally in a plate-like base material; and

[0179] a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged so as to sandwich the active layer and the two-dimensional photonic crystal layer in a stacking direction;

[0180] wherein the first electrode is disposed at a position farther from the active layer than the second electrode,

[0181] At least a portion of the first electrode exists within a projection of a circumscribed circle of the second electrode onto the first electrode.

[0182] (Item 11) The two-dimensional photonic crystal laser involved in Item 11 is characterized in that, in the two-dimensional photonic crystal laser involved in any one of Items 1 to 10, a value obtained by dividing the current density at the outer edge of the light-emitting region in the active layer when a voltage is applied between the first electrode and the second electrode by the current density at the center of the light-emitting region is greater than 0.2 and less than 1.2.

[0183] (Item 12) The two-dimensional photonic crystal laser according to Item 12 is characterized in that, in the two-dimensional photonic crystal laser according to Item 11, the diameter of the inscribed circle of the light emitting region is greater than 1 mm.

[0184] Description of Reference Numerals

[0185] 10, 20, 30, 40, 90: two-dimensional photonic crystal laser; 11, 91: active layer; 12, 92: two-dimensional photonic crystal layer; 121: base material; 122: different refractive index region; 1221: first different refractive index region; 1222: second different refractive index region; 13: spacer layer; 141, 941: first cladding layer; 142, 942: second cladding layer; 16, 96: substrate; 171, 171A, 171B, 171C, 171D, 171E, 171 F, 171G, 171H, 271, 371, 371A, 471: first electrode; 1711, 1711C, 1711D, 2711, 4711: main area; 1711H: conductive material of the first electrode; 17111, 27111: first circle (outer edge of the first electrode); 17112, 17112C, 27112: second circle; 17112H: inner edge of the conductive material; 17113: slit of the main area; 1712, 1712A , 1712B, 1712C, 1711D, 2712, 4712: sub-region; 1712C1: first sub-region; 1712C2: second sub-region; 1718, 1728: insulating film; 1718A, 1728A: opposite polarity region; 172, 172A, 172B, 172C, 172S, 472: second electrode; 1721: projection of the second electrode onto the first electrode; 1723S: circumscribed circle of the second electrode; 1727: reflecting portion; 1728: Insulating film; 175, 175A, 175D, 175E, 175H, 275, 475, 975: opening (window); 18, 98: current; 181, 981: light-emitting area; 2731: electrode pad; 2732: groove (air); 4720: second projection; 4721: conductive part of the second electrode; 4722: non-conductive part of the second electrode; 9421: surface of the second coating layer; 971: window electrode; 972: electrode; 9721: projection of electrode 972.

Claims

1. A two-dimensional photonic crystal laser, characterized in that: have: Active layer; a two-dimensional photonic crystal layer provided on one surface side of the active layer, wherein different refractive index regions having a refractive index different from that of the base material are periodically arranged two-dimensionally in a plate-like base material; and a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged so as to sandwich the active layer and the two-dimensional photonic crystal layer in a stacking direction; wherein the first electrode has an opening, The projection of the circumscribed circle of the second electrode onto the first electrode is located within the opening, At least a portion of a periphery of the opening of the first electrode protrudes into the projection.

2. The two-dimensional photonic crystal laser according to claim 1, characterized in that: The first electrode includes a main region surrounding the projection and a linear sub-region extending from the main region into the projection.

3. The two-dimensional photonic crystal laser according to claim 1, characterized in that: A second projection of the second electrode onto the first electrode is located within the opening, and at least a portion of the periphery of the opening extends into the second projection.

4. The two-dimensional photonic crystal laser according to claim 3, characterized in that: A non-conductive portion is formed on the second electrode in at least a portion of a third projection which is a projection of a portion of the first electrode extending into the second projection onto the second electrode.

5. The two-dimensional photonic crystal laser according to claim 3, characterized in that: The first electrode includes a main region surrounding the second projection and a linear sub-region extending from the main region into the second projection.

6. The two-dimensional photonic crystal laser according to claim 2 or 5, characterized in that: The plurality of sub-regions are provided with different lengths, widths, thicknesses and materials or two or more thereof.

7. The two-dimensional photonic crystal laser according to any one of claims 1 to 5, characterized in that: The first electrode is physically divided into a plurality of electrodes.

8. The two-dimensional photonic crystal laser according to any one of claims 1 to 5, characterized in that: An area of ​​a portion of the first electrode inside the projection is larger than an area of ​​an portion outside the projection.

9. The two-dimensional photonic crystal laser according to any one of claims 1 to 5, characterized in that: The different refractive index region is a region formed by combining two holes or members having a refractive index different from that of the base material.

10. A two-dimensional photonic crystal laser, characterized in that: have: Active layer; a two-dimensional photonic crystal layer provided on one surface side of the active layer, wherein different refractive index regions having a refractive index different from that of the base material are periodically arranged two-dimensionally in a plate-like base material; and a first electrode and a second electrode, wherein the first electrode and the second electrode are arranged so as to sandwich the active layer and the two-dimensional photonic crystal layer in a stacking direction; wherein the first electrode is disposed at a position farther from the active layer than the second electrode, At least a portion of the first electrode exists within a projection of a circumscribed circle of the second electrode onto the first electrode.

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