Optical deflection module
The optical deflection module addresses structural complexity and intensity variation by using distributed Bragg reflectors with varying reflectance, ensuring consistent or adjustable light emission and reducing production costs.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- PIONEER IP
- Filing Date
- 2026-05-22
- Publication Date
- 2026-07-24
AI Technical Summary
Existing optical deflection modules with active layers and complex structures face increased production costs and decreased yield due to structural complexity, leading to a decrease in emitted light intensity.
An optical deflection module with a light guide layer and distributed Bragg reflector layers having varying reflectance based on distance from the light incident surface, allowing for homogeneous or intensity-adjusted light emission with a simple structure.
The module maintains consistent or adjustable light intensity across the emission surface, reducing attenuation and complexity, thereby improving production efficiency and yield.
Smart Images
Figure 2026121560000001_ABST
Abstract
Description
Technical Field
[0005]
[0001] The present invention relates to an optical deflection module.
Background Art
[0002] In recent years, regarding devices that deflect and scan laser light emitted from semiconductor lasers and the like, optical deflection modules with various structures have been proposed.
[0003] For example, Patent Document 1 discloses an optical deflection module having an optical waveguide layer sandwiched between two Bragg mirror layers, and using the surface of one of the two Bragg mirror layers as an optical output surface to emit the light propagating through the optical waveguide layer from the optical output surface.
[0004] <L000016>The optical deflection module of Patent Document 1 is provided with a light emitting layer for compensating for the decrease in emitted light due to the attenuation of light during propagation in the optical waveguide layer.
Prior Art Documents
Patent Documents
[0005]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0006] For example, in an optical deflection module such as that of Patent Document 1, in order to prevent a decrease in emitted light, it is necessary to provide an active layer and a structure for supplying current to the active layer, resulting in a problem that the structure of the module becomes complicated. This complexity of the structure can, for example, lead to an increase in the production cost of the module and a decrease in the yield.
[0007] The present invention has been made in view of the above-mentioned points, and one of its objectives is to provide an optical deflection module that can homogenize the emitted light within the light-emitting surface with a simple structure. Another objective is to provide an optical deflection module that can adjust the intensity of the emitted light within the light-emitting surface with a simple structure. [Means for solving the problem]
[0008] The invention described in claim 1 is an optical deflection module comprising: a light guide layer through which light is guided; and a distributed Bragg reflector layer formed on one surface of the light guide layer and having a light incident surface through which light is emitted on one surface opposite to the light guide layer, wherein the reflectance of the distributed Bragg reflector layer to the light in the region where the light emission surface is formed changes with respect to the distance from the light incident surface. [Brief explanation of the drawing]
[0009] [Figure 1] This is a top view of the optical deflection module according to Example 1. [Figure 2] This is a cross-sectional view of the optical deflection module according to Example 1. [Figure 3] This figure shows the intensity of the emitted light from the optical deflection module according to Example 1. [Figure 4] This is a cross-sectional view of the light deflection module according to Example 2. [Figure 5] This figure shows the intensity of the emitted light from the optical deflection module according to Example 2. [Figure 6] This is a top view of the optical deflection module according to Example 3. [Figure 7] This is a cross-sectional view of the light deflection module according to Example 3. [Figure 8] This is a cross-sectional view of the light deflection module according to Example 3. [Figure 9] This figure shows the intensity of the emitted light from the optical deflection module according to Example 3. [Modes for carrying out the invention]
[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment
[0011] Hereinafter, referring to FIG. 1, the configuration of the optical deflection module 10 according to Embodiment 1 of the present application will be described. FIG. 1 is a top view showing the optical deflection module 10 according to Embodiment 1.
[0012] [[ID=—14]]As shown in FIG. 1, the optical deflection module 10 has a rectangular planar shape. On the upper surface of the optical deflection module 10, an optical incident surface IS which is an incident surface of light incident into the optical deflection module 10 and an optical emission surface ES which is an emission surface of light emitted from the optical deflection module 10 are provided.
[0013] FIG. 2 is a cross-sectional view taken along the line 2-2 of FIG. 1. The substrate 11 is a plate-shaped substrate having the same planar shape as the planar shape of the optical deflection module 10. Specifically, for example, the substrate 11 is a GaAs substrate. <000n080>
[0014] The lower reflection layer 13 is a layer that forms a distributed Bragg reflector (DBR) structure formed by a semiconductor multilayer film laminated on the substrate 11 in a direction perpendicular to the upper surface of the substrate 11. Specifically, for example, this lower reflection layer 13 is an AlAs / GaAs semiconductor multilayer film in which thin films of AlAs and GaAs are alternately laminated.
[0015] The layer thickness of each layer of this semiconductor multilayer film is determined based on the wavelength of the incident light IL incident from the optical incident surface IS. Specifically, for example, the layer thickness of each layer of the semiconductor multilayer film is preferably set to a thickness of 1 / 4 of the wavelength of the incident light IL in the layer.
[0016] The light guiding layer 15 is provided on the upper surface of the lower reflection layer 13 and is a layer capable of guiding the light incident from the optical incident surface IS. Specifically, for example, the light guiding layer 15 is a layer made of GaAs.
[0017] The upper reflective layer 17 as the distributed Bragg reflector layer is a layer that forms a distributed Bragg reflector (DBR) structure formed by a semiconductor multilayer film laminated in a direction perpendicular to the upper surface of the substrate 11 on the light guiding layer 15. That is, the upper reflective layer 17 and the lower reflective layer 13 sandwich the light guiding layer 15 together.
[0018] For example, this upper reflective layer 17 is an AlAs / GaAs semiconductor multilayer film in which thin films of AlAs and GaAs are alternately laminated. Similar to the lower reflective layer 13, the layer thickness per layer of the semiconductor multilayer film of the upper reflective layer 17 is determined based on the wavelength of the incident light IL incident from the light incident surface IS. Specifically, the layer thickness per layer of the semiconductor multilayer film is preferably set to a thickness of 1 / 4 of the wavelength of the incident light IL in the layer.
[0019] The upper reflective layer 17 has a notch portion 17A that is cut out in a rectangular parallelepiped shape from above the light deflection module at one end in the longitudinal direction of the light deflection module 10. The notch portion 17A terminates within the upper reflective layer 17, is exposed by the notch portion 17A, and the surface facing upward is the above-described light incident surface IS.
[0020] The upper surface of the upper reflective layer 17 other than the region where the notch portion 17A is formed serves as the above-described light emission surface ES. The light emission surface ES forms an inclined surface that approaches the upper surface of the substrate 11 as it moves away from the notch portion 17A. That is, as the distance from the notch portion 17A increases, the number of layers of the semiconductor multilayer film of the upper reflective layer 17 decreases, and the thickness of the upper reflective layer 17 decreases.
[0021] <Furthermore, in the region below the light emission surface ES in a direction perpendicular to the upper surface of the substrate 11, the number of semiconductor multilayer layers in the upper reflective layer 17 is smaller than the number of semiconductor multilayer layers in the lower reflective layer 13. That is, the reflectance for incident light IL is greater in the lower reflective layer 13 than in the upper reflective layer 17. As an example, in this embodiment, the lower reflective layer 13 is composed of 40 layers of AlAs / GaAs, and the upper reflective layer 17 is composed of 20 layers of AlAs / GaAs at its thickest point.
[0023] Hereinafter, the lower reflective layer 13, the light guide layer 15, and the upper reflective layer 17 will be collectively referred to as an optical waveguide.
[0024] As shown in Figure 2, in the optical deflection module 10 described above, when light enters the optical waveguide from the light incident surface IS, the light in the optical waveguide propagates (guides) within the optical waveguide while being reflected by the lower reflective layer 13 and the upper reflective layer 17 provided on the lower and upper surfaces of the optical guide layer 15.
[0025] As described above, the upper reflective layer 17 is configured to have a lower light reflectivity than the lower reflective layer 13. Therefore, of the light propagating within the light guide layer 15, the light that is not reflected by the upper reflective layer 17 and leaks out is emitted from the light emission surface ES on the upper surface of the upper reflective layer 17. In other words, the light propagating through the light guide layer 15 is initially incident from the light incident surface IS, and as it propagates away from the light incident surface IS, it is gradually emitted from the light emission surface ES and attenuated.
[0026] Here, the internal propagation angle θi in the optical waveguide is approximately expressed by equation (1) below. In equation (1), λ is the wavelength of the incident light, and λc is the cutoff wavelength, which is the shortest wavelength of light that can propagate in single mode in the optical waveguide.
[0027]
number
[0028] Therefore, according to Snell's Law, the deflection angle θr of light emitted from the exit surface of the upper reflective layer 17 of the optical deflection module 10 is expressed by equation (2) below. In equation (2), n is the average refractive index of the optical waveguide.
[0029]
number
[0030] As can be seen from the above formula, with the optical deflection module 10 of this embodiment, the deflection angle θr can be changed by changing the wavelength of the light incident on the light incident surface IS.
[0031] As described above, in the case of an optical deflection module with a configuration such as the optical deflection module 10 of this embodiment, in which light propagating through the light guide layer 15 leaks out little by little from the upper reflective layer 17 and is emitted, the light propagating through the light guide layer propagates while gradually attenuating. Therefore, if the thickness of the upper reflective layer 17, that is, the number of semiconductor multilayer films of the upper reflective layer 17, is the same throughout the entire lower part of the light emission surface ES, the intensity of the light emitted from the light emission surface ES becomes smaller the further it is from the light incident surface IS.
[0032] In the optical deflection module 10 of this embodiment, as described above, the further away from the notch 17A that provides the light incident surface IS, the fewer layers of the semiconductor multilayer film in the upper reflective layer 17 there are, and the thinner the upper reflective layer 17 becomes. Therefore, the further away from the light incident surface IS, the lower the reflectivity of the upper reflective layer 17 becomes, and the proportion of light leaking out from the light guide layer 15 increases. As a result, it is possible to reduce the decrease in the intensity of the light emitted from the light emission surface ES caused by the attenuation of light propagating through the light guide layer 15.
[0033] Figure 3 shows a graph of the intensity of the emitted light EL from the light-emitting surface ES in a region along the cross-section shown in Figure 2. In this graph, the horizontal axis represents the distance L from the light-incident surface IS along the cross-section of Figure 2, and the vertical axis represents the intensity of the emitted light EL. Figure 3 shows the case where the light intensity of the emitted light EL is constant across the light-emitting surface ES.
[0034] As described above, in the optical deflection module 10 of this embodiment, the number of semiconductor multilayer films in the upper reflective layer 17 is reduced according to the attenuation rate of the light propagating through the light guide layer 15, that is, according to the distance from the light incident surface IS. Therefore, with the optical deflection module 10 of this embodiment, as shown in Figure 3, the intensity of the emitted light EL can be kept constant across the light emission surface ES.
[0035] In Figure 2, the inclination of the light-emitting surface ES, which is the upper surface of the upper reflective layer 17, is constant, and the case where the light-emitting surface ES is a straight line in cross-section is illustrated. However, if the light intensity of the emitted light EL is kept constant across the light-emitting surface ES, the inclination of the light-emitting surface may change along the way, for example, depending on the attenuation rate of the light propagating through the light guide layer 15. Alternatively, the light-emitting surface ES may be curved in cross-section.
[0036] Furthermore, depending on the desired intensity distribution of the emitted light EL, it is possible to arbitrarily change the number of layers of the semiconductor multilayer film in the upper reflective layer 17 according to the distance from the light incident surface IS. For example, if it is desired that the intensity of the emitted light EL weakens as the distance from the light incident surface IS increases, the number of layers of the semiconductor multilayer film in the upper reflective layer 17 can be increased as the distance from the light incident surface IS increases, thereby increasing the reflectivity of the upper reflective layer 17. [Examples]
[0037] The optical deflection module 20 of Example 2 of the present invention will now be described. The optical deflection module 20 of Example 2 is a module intended to give the intensity of the emitted light EL a Gaussian distribution in the longitudinal direction of the optical deflection module 20.
[0038] Figure 4 shows a cross-sectional view of the optical deflection module 20 in the same cross-section as in Figure 2. Note that the optical deflection module 20 of Example 2 has the same configuration as the optical deflection module 10 of Example 1, except for the different shape of the upper reflective layer 17. Therefore, in the following description, explanations other than the upper reflective layer 17 will be omitted. In Figure 4, the shape of the optical emission surface ES of the optical deflection module 10 of Example 1 is shown by a dashed line.
[0039] As shown in Figure 4, in the optical deflection module 20, the shape of the light-emitting surface ES is recessed toward the substrate 11, with the region around the plane CS that includes the center line in the longitudinal direction of the light-emitting surface ES and is perpendicular to the cross-section, based on the shape of the optical deflection module 10. In other words, the thickness of the upper reflective layer 17, or in other words, the reflectance of the upper reflective layer 17, is smallest in the central region in the longitudinal direction of the light-emitting surface ES.
[0040] Figure 5 shows a graph of the intensity of the emitted light EL from the light-emitting surface ES in the region along the cross-section shown in Figure 4. Similar to Figure 3, in this graph, the horizontal axis represents the distance L from the light-incident surface IS along the cross-section of Figure 4, and the vertical axis represents the intensity of the emitted light EL.
[0041] As described above, in the optical deflection module 20, the thickness of the upper reflective layer 17 is reduced in proportion to the distance from the optical incident surface IS, and the shape of the optical emission surface ES is made concave, mainly in the region around the surface CS of the optical emission surface ES. By doing so, as shown in Figure 5, it is possible to make the intensity distribution of the emitted light EL a Gaussian distribution or a distribution close to it.
[0042] Furthermore, the shape of the light-emitting surface ES in the cross-section shown in Figure 4 may be determined by combining the shape obtained by inverting the ideal Gaussian distribution shape with the inclined shape of the light-emitting surface ES in Example 1. In this way, it is possible to obtain a symmetrical distribution of emitted light EL in the direction along the cross-section of Figure 4, taking into account the attenuation of light in the light guide layer 15.
[0043] As described above, in the optical deflection module 20, the reflectance of the upper reflective layer 17 changes according to the distance from the optical incident surface IS and according to the desired output intensity distribution of the emitted light EL emitted from the optical emission surface ES.
[0044] The emitted light EL, which has a Gaussian distribution and is realized by the optical deflection module 20, does not change its intensity distribution much even when it propagates. Therefore, for example, the intensity distribution of the incident light does not become disturbed even when it is incident on a light detection module or the like after being emitted from the optical deflection module 20, making it easier to process the signal generated by the incident light.
[0045] Similar to Example 1, the shape of the light-emitting surface ES of the light deflection module 20 can also be formed, for example, by stacking a semiconductor multilayer film on the light guide layer 15 and then performing etching using a 3D photomask (grayscale mask). [Examples]
[0046] The optical deflection module 30 of Embodiment 3 of the present invention will be described below. The optical deflection module 30 is a module intended to give the intensity of the emitted light EL an annular distribution.
[0047] Figure 6 shows a top view of the optical deflection module 30. Note that the optical deflection module 30 of Example 3 has the same configuration as the optical deflection module 10 of Example 1, except for differences in the aspect ratio of the top surface shape and the shape of the upper reflective layer 17. Therefore, in the following description, explanations other than those of the upper reflective layer 17 will be omitted.
[0048] As shown in Figure 6, the light-emitting surface ES of the light deflection module 30 has a recess-forming region RR (indicated by the dashed line in the figure) in the center. Within the recess-forming region RR, a donut-shaped (annular) recess RP is formed with the center point P at the center. In Figure 6, a gradient is used, with darker colors for deeper recesses and lighter colors for shallower recesses, to make the shape easier to understand.
[0049] Figure 7 shows a cross-sectional view along the line 7-7 passing through the center point P in Figure 6, and Figure 8 shows a cross-sectional view along the 8-8 section of Figure 6. In Figures 7 and 8, the shape of the light emission surface ES of the light deflection module 10 of Example 1 is shown by a dashed line.
[0050] As shown in Figures 7 and 8, the shape of the light emission surface ES is based on the shape of the light deflection module 10, with an annular recess RP provided.
[0051] The cross-section shown in Figure 7, that is, the cross-section passing through the center point P, is a cross-section of the annular recess RP cut along the center line. Therefore, in Figure 7, the two recesses RP1 and RP2 are shown aligned along this cross-section. Furthermore, recess RP2 is deeper than recess RP1.
[0052] The cross-section shown in Figure 8 is a cross-section of the region near the end of the annular recess RP. Therefore, in Figure 8, it is shown that one shallow recess has been formed.
[0053] Figure 9 shows a graph of the intensity of the emitted light EL from the light-emitting surface ES in the region along the cross-section shown in Figure 7. Similar to Figure 3, in this graph, the horizontal axis represents the distance L from the light-incident surface IS along the cross-section of Figure 7, and the vertical axis represents the intensity of the emitted light EL.
[0054] As described above, in the optical deflection module 30, the thickness of the upper reflective layer 17 is reduced in proportion to the distance from the light incident surface IS, and an annular recess RP is formed on the light emission surface ES with the center point P of the light emission surface ES at the center of the light emission surface ES. In other words, in the optical deflection module 30, an annular region with a lower reflectivity than the surrounding area is formed within the light emission surface ES.
[0055] By doing so, it is possible to create an intensity distribution of the emitted light EL that has a ring-shaped region of high light intensity and a region of low light intensity surrounded by the ring-shaped region.
[0056] Figure 9 shows a light intensity distribution with two peaks corresponding to the cross-sectional shape shown in Figure 7. Furthermore, the recess RP2, which is further from the light incident surface IS, is formed deeper than the recess RP1; that is, the reflectivity of the upper reflective layer 17 is lower in the region where recess RP2 is provided. Therefore, a symmetrical light intensity distribution is achieved regardless of the attenuation of light in the light guide layer 15.
[0057] The shape of the annular recess may be determined by combining the shape obtained by inverting the ideal light intensity distribution shape with the inclined shape of the light emission surface ES in Example 1. In this way, it is possible to obtain a symmetrical distribution of emitted light EL across the entire light emission surface ES, taking into account the attenuation of light in the light guide layer 15.
[0058] As described above, in the optical deflection module 30, the reflectivity of the upper reflective layer 17 changes according to the distance from the optical incident surface IS and according to the desired output intensity distribution of the emitted light EL emitted from the optical emission surface ES.
[0059] The annularly distributed emitted light EL, realized by the light deflection module 30, is not significantly affected by lens aberrations. Therefore, for example, when the emitted light EL from the light deflection module 30 is focused by a lens, it becomes easy to reduce the spot diameter of the focused beam.
[0060] Similar to Examples 1 and 2, the shape of the light-emitting surface ES of the light deflection module 30 can also be formed, for example, by stacking a semiconductor multilayer film on the light guide layer 15 and then performing etching using a 3D photomask (grayscale mask).
[0061] In the above embodiment, the lower reflective layer 13 and the upper reflective layer 17 were formed from a semiconductor multilayer film made of AlAs / GaAs. However, the semiconductor multilayer film forming the lower reflective layer 13 and the upper reflective layer 17 is not limited to this. For example, the semiconductor multilayer film forming the lower reflective layer 13 and the upper reflective layer 17 may be a semiconductor multilayer film made of GaAlAs / GaAs.
[0062] Furthermore, the semiconductor multilayer film forming the lower reflective layer 13 and the upper reflective layer 17 may be a semiconductor multilayer film made of InGaAsP / InP. When the semiconductor multilayer film is made of InGaAsP / InP, for example, the material of the substrate 11 is In and the material of the light guide layer 15 is InGaAsP.
[0063] The various configurations and other elements in the above-described embodiments are merely examples and can be appropriately selected depending on the application and other factors. [Explanation of symbols]
[0064] 10, 20, 30 Optical deflection modules 11 circuit boards 13 Lower Reflecting Layer 15 Light guide layer 17 Upper reflective layer IS light incidence surface ES light exit surface
Claims
[Claim 1] A light-guiding layer that guides light, A first distributed Bragg reflector layer is formed on one surface of the light guide layer, and on one surface opposite to the surface facing the light guide layer, the surface has a light incident surface into which the light enters the light guide layer and a light exit surface from which the light exits. A second distributed Bragg mirror layer formed on the other surface of the light guide layer, A light deflection module characterized by having the following features.