DE-112024003156-T5 - Light-emitting device

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Abstract

A light-emitting device comprises an active layer as the light-emitting section and a phase-modulation layer 15. The phase-modulation layer 15 is optically coupled to the active layer and has a base layer and several regions with different refractive indices. These regions have a refractive index different from that of the base layer and are distributed in a two-dimensional shape in a plane perpendicular to the thickness direction. With respect to a corresponding grid point of a virtual grid, the centroid of each region with a different refractive index is located at a relative position corresponding to a phase-modulation amount of a predetermined phase distribution. The predetermined phase distribution includes a region 153 around an optical axis 21, wherein the region 153 has a two-dimensional lens pattern whose phase varies in two mutually orthogonal directions. The two-dimensional lens pattern causes a beam 245 emitted from the region 153 to be first reduced in diameter at a first position 33 and then enlarged to a ring-like shape.

Inventors

Kazuyoshi Hirose
Hiroki Kamei
Takahiro Sugiyama
Yuya Imaeda
Koyo Watanabe

Assignees

HAMAMATSU PHOTONICS K.K.

Dates

Publication Date: 20260513
Application Date: 20240718
Priority Date: 20230802

Claims (19)

A light-emitting device comprising: a light-emitting section; and a phase-modulation layer optically coupled to the light-emitting section, comprising a base layer and multiple regions with different refractive indices, wherein the multiple regions with different refractive indices have a refractive index different from that of the base layer and are distributed in a two-dimensional shape in a plane perpendicular to the thickness direction, where a centroid of each of the multiple regions with different refractive indices is located at a relative position corresponding to a phase-modulation amount of a predetermined phase distribution with respect to a corresponding lattice point of a virtual square lattice in the plane, where the predetermined phase distribution comprises regions on both sides of an optical axis in one direction, each region having a one-dimensional lens pattern whose phase changes in one direction, and where the one-dimensional lens pattern causes a first ray emitted by a region that is one of the regions on one side of the optical axis to intersect a second ray emitted by a region that is one of the regions on the other side of the optical axis at a first position and then they separate.
The light-emitting device according to Claim 1 , where the one-dimensional lens pattern is represented by the following formula (1), which contains a coordinate x in one direction with the optical axis as the origin, a distance L from the optical axis to an edge of the one-dimensional lens pattern, a positive real number α and a positive real number β [Formula 1] ϕ n o r m ( x ) = − 2 π β | x L | α where: -L ≤ x ≤ L. α < 2
The light-emitting device according to Claim 2 , where the positive real number α is set to 1.0 and the positive real number β is greater than or equal to 2.0 and less than or equal to 20.
The light-emitting device according to Claim 2 , where the positive real number α is set to greater than or equal to 0.8 and less than or equal to 1.2, and the positive real number β is greater than or equal to 2.0 and less than or equal to 10.
The light-emitting device according to Claim 2 , where the positive real number α is set to less than or equal to 0.5 and the positive real number β is greater than or equal to 5.0 and less than or equal to 20.
The light-emitting device according to one of the Claims 1 until 5 , wherein the predetermined phase distribution has a gap containing the optical axis between the region on one side of the optical axis and the region on the other side of the optical axis.
The light-emitting device according to one of the Claims 1 until 6 , wherein a further one-dimensional lens pattern, the phase of which changes in one direction, is superimposed on the one-dimensional lens pattern in each of the regions, a third beam, different from the first beam, is emitted from the further one-dimensional lens pattern from the region on one side of the optical axis, and a fourth beam, different from the second beam, is emitted from the further one-dimensional lens pattern from the region on the other side of the optical axis, and the third beam and the fourth beam intersect at a second position, different from the first position, and then separate from each other.
The light-emitting device according to Claim 7 , where the first position and the second position are located on a common virtual plane perpendicular to the optical axis.
The light-emitting device according to Claim 7 , wherein the first position is on a first virtual plane perpendicular to the optical axis and the second position is on a second virtual plane perpendicular to the optical axis and different from the first virtual plane.
A light-emitting device comprising: a light-emitting section; and a phase-modulation layer optically coupled to the light-emitting section, comprising a base layer and multiple regions with different refractive indices, wherein the multiple regions with different refractive indices have a refractive index different from that of the base layer and are distributed in a two-dimensional shape in a plane perpendicular to a thickness direction, wherein a centroid of each of the multiple regions with different refractive indices is located at a relative position corresponding to a Phase modulation amount of a predetermined phase distribution with respect to a corresponding grid point of a virtual square grid fixed in the plane, wherein the predetermined phase distribution has a region around an optical axis, the region having a two-dimensional lens pattern whose phase varies in two mutually orthogonal directions, and wherein the two-dimensional lens pattern causes a first beam emitted from the region to be reduced in diameter at a first position and then enlarged to a ring-like shape.
The light-emitting device according to Claim 10 , wherein the two-dimensional lens pattern is represented by the following formula (2) which contains a distance r from the optical axis, a distance L from the optical axis to an edge of the two-dimensional lens pattern, a positive real number α and a positive real number β [Formula 2] ϕ n o r m ( x ) = − 2 π β | r L | α where: -L≤r≤L, α<2
The light-emitting device according to Claim 11 , where the positive real number α is set to less than or equal to 1,2.
The light-emitting device according to Claim 11 , where the positive real number α is set to greater than or equal to 0.5 and less than or equal to 1.2, and the positive real number β is greater than or equal to 2.0 and less than or equal to 20.
The light-emitting device according to Claim 11 , where the positive real number α is set to greater than or equal to 0.1 and less than or equal to 0.25 and the positive real number β is greater than or equal to 5.0 and less than or equal to 50.
The light-emitting device according to one of the Claims 10 until 14 , wherein the area has a shape with an opening that contains the optical axis.
The light-emitting device according to one of the Claims 10 until 15 , wherein a further two-dimensional lens pattern, whose phase changes in both directions, is superimposed on the two-dimensional lens pattern in the area, a second beam, which differs from the first beam, is emitted from the area through the further two-dimensional lens pattern, and the second beam is first reduced in diameter at a second position, which differs from the first position, and then enlarged in diameter in a ring shape.
The light-emitting device according to Claim 16 , where the first position and the second position are located on a common virtual plane perpendicular to the optical axis.
The light-emitting device according to Claim 16 , wherein the first position is on a first virtual plane perpendicular to the optical axis and the second position is on a second virtual plane that is perpendicular to the optical axis and is different from the first virtual plane.
The light-emitting device according to one of the Claims 1 until 18 , wherein a grid spacing of the virtual square grating and an emission wavelength λ of the light-emitting section are set such that they satisfy a vibration condition at an M-point, and plane-internal wavenumber vectors in four directions, each exhibiting a wavenumber scattering corresponding to an angular scattering of the light emitted by the light-emitting device, are formed in a reciprocal grating space of the phase modulation layer, and a magnitude of at least one of the plane-internal wavenumber vectors is less than 2π/λ.

Description

Technical field The present disclosure relates to a light-emitting device. This application claims priority from Japanese patent application no. 2023-126151 , which was filed on August 2, 2023, and incorporates all content described in the Japanese application by reference. State of the art Patent reference 1 discloses a light-emitting device. The light-emitting device has a light-emitting section and a phase-modulation layer. The phase-modulation layer is optically coupled to the light-emitting section. The phase-modulation layer has a base layer and several regions with different refractive indices. The several regions with different refractive indices have a refractive index different from that of the base layer and are distributed in a two-dimensional shape in a plane perpendicular to the thickness direction. When a virtual square grating is defined in the plane, the centroid of each region with a different refractive index is spaced from a corresponding grating point and has an individual rotation angle about the corresponding grating point according to a predetermined phase distribution. A grating spacing of the virtual square grating and an emission wavelength of the light-emitting section satisfy a condition for M-point oscillation. The predetermined phase distribution includes an element for focusing the emitted light in at least one direction. Patent literature 2 discloses a light-emitting semiconductor device. The light-emitting semiconductor device emits a light image in a direction inclined to a direction perpendicular to a main surface of a semiconductor substrate. The light-emitting semiconductor device has an active layer, a cladding layer, a contact layer, a phase-modulation layer, and an electrode. The active layer is located on the main surface of the semiconductor substrate. The cladding layer is located on the active layer. The contact layer is located on the cladding layer. The phase-modulation layer is located between the semiconductor substrate and the active layer or between the active layer and the cladding layer. The electrode is located on the contact layer. The phase-modulation layer has a first region that overlaps the electrode when viewed from a thickness direction of the phase-modulation layer, and a second region that excludes the first region. The phase-modulation layer has a base layer and several regions with different refractive indices, the refractive indices of which differ from that of the base layer. When a virtual square grating is arranged in a plane perpendicular to the thickness direction of the phase modulation layer, the centroids of the multiple regions with different refractive indices contained in the second region are spaced from the grating points of the virtual square grating and exhibit a rotation angle about the corresponding grating points, corresponding to a light pattern. The light pattern is completed only by the second region of the phase modulation layer. The non-patent literature 1 discloses a method for generating a Bessel beam using an axionic lens or a metalisin. List of cited works Patent literature [Patent Literature 1] Japanese Unexamined Published Patent Application No. 2022-154929[Patent Literature 2] Japanese Unexamined Published Patent Application No. 2018-206921 Non-patented literature [Non-patent literature 1] Wei Ting Chen et al., “Generation of wavelength-independent subwavelength Bessel beams using metasurfaces”, Light: Science & Applications 6, e16259 (2017) )[Non-patent literature 2] Y. Kurosaka et al., “Effects of non-lasing band in two-dimensional photonic-crystal lasers clarified using omnidirectional band structure”, Opt. Express 20, 21773-21783 (2012) ) Overview of the invention Technical problem In current technology, devices containing a light source use optical components such as a lens as an optical system to focus the light from the light source. If miniaturization of such a light source device is required, the light source can be reduced, for example, by using a light-emitting semiconductor device. The light source device can be significantly miniaturized. On the other hand, miniaturizing optical components for focusing light is difficult and becomes a factor that hinders the miniaturization of the light source device. Therefore, the light-emitting device described in patent literature 1 includes a light-emitting section and a phase modulation layer, and the phase distribution of the phase modulation layer is designed such that the emitted light is focused in at least one direction. In this case, the distance between the object to be illuminated and the light source can vary depending on the application. For example, when a light source is used in a medical endoscope, the position of the endoscope relative to the part to be imaged, which is the irradiation target, is not predetermined. Therefore, it is necessary to allow for a certain distance between the part to be imaged and the light source. Accordingly, it is desi