Optical deflection module

Abstract

To provide an optical deflection module capable of equalizing emission light in a light emission surface by a simple structure, and to provide an optical deflection module capable of adjusting the intensity of emission light in a light emission surface by a simple structure.SOLUTION: An optical deflection module has: a light guiding layer that guides light; and a distribution Bragg reflection mirror layer that is formed on one surface of the light guiding layer and has a light incident surface where the light is incident and a light emission surface where the light emits, in the light guiding layer on the surface opposite to the light guiding layer. A reflectance to the light of the distribution Bragg reflection mirror layer in an area where the light emission surface is formed changes according to a distance from the light incident surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical deflection module. [Background technology]

[0002] In recent years, there has been a growing interest in devices that deflect and scan laser light emitted from semiconductor lasers, etc. Optical deflection modules with various structures have been proposed.

[0003] For example, Patent Document 1 discloses an optical deflection module that has an optical waveguide layer sandwiched between two Bragg mirror layers, with the surface of one of the two Bragg mirror layers serving as a light exit surface, and that emits light propagating through the optical waveguide layer from the light exit surface.

[0004] The optical deflection module of Patent Document 1 is provided with a light emitting layer for compensating for a decrease in output light caused by attenuation of light propagating through an optical waveguide layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5930231 Summary of the Invention [Problem to be solved by the invention]

[0006] For example, in the optical deflection module of Patent Document 1, in order to prevent the reduction of the emitted light, it is necessary to provide an active layer and a structure for supplying a current to the active layer, which causes a problem that the structure of the module becomes complicated. This structural complexity can lead to, for example, an increase in the production cost of the module and a decrease in the yield.

[0007] The present invention has been made in consideration of the above-mentioned points, and has an object to provide an optical deflection module capable of homogenizing the emitted light in the light emission surface with a simple structure. Another object of the present invention is to provide an optical deflection module capable of adjusting the intensity of the emitted light in the light emission 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-guiding layer that guides light; and a distributed Bragg reflector layer formed on one surface of the light-guiding layer and having a light entrance surface through which the light enters the light-guiding layer and a light exit surface from which the light exits, on a surface opposite the light-guiding layer, wherein the reflectance of the distributed Bragg reflector layer for the light in the region where the light exit surface is formed varies depending on the distance from the light entrance surface. [Brief description of the drawings]

[0009] [Figure 1] 1 is a top view of an optical deflection module according to a first embodiment. [Diagram 2] 1 is a cross-sectional view of an optical deflection module according to a first embodiment. [Diagram 3] 5 is a diagram showing the intensity of the emitted light of the optical deflection module in accordance with the first embodiment. FIG. [Figure 4] FIG. 11 is a cross-sectional view of an optical deflection module according to a second embodiment. [Diagram 5] 10 is a diagram showing the intensity of the emitted light of the optical deflection module in accordance with the second embodiment. FIG. [Figure 6] FIG. 11 is a top view of the optical deflection module according to the third embodiment. [Figure 7] FIG. 11 is a cross-sectional view of an optical deflection module according to a third embodiment. [Figure 8] FIG. 11 is a cross-sectional view of an optical deflection module according to a third embodiment. [Figure 9] 13 is a diagram showing the intensity of the emitted light of the optical deflection module according to the third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. EXAMPLES

[0011] A configuration of an optical deflection module 10 according to a first embodiment of the present invention will be described below with reference to Fig. 1. Fig. 1 is a top view showing the optical deflection module 10 according to the first embodiment.

[0012] 1, the optical deflection module 10 has a rectangular planar shape. On the upper surface of the optical deflection module 10, a light incident surface IS which is an incident surface of light entering the optical deflection module 10 and a light exit surface ES which is an exit surface of light exiting the optical deflection module 10 are provided.

[0013] Fig. 2 is a cross-sectional view taken along line 2-2 in Fig. 1. The substrate 11 is a plate-like substrate having the same planar shape as that of the optical deflection module 10. Specifically, for example, the substrate 11 is a GaAs substrate.

[0014] The lower reflective layer 13 is a layer forming a distributed Bragg reflector (DBR) structure formed by a semiconductor multilayer film stacked on the substrate 11 in a direction perpendicular to the upper surface of the substrate 11. Specifically, for example, the lower reflective layer 13 is an AlAs / GaAs semiconductor multilayer film in which thin films of AlAs and thin films of GaAs are stacked alternately.

[0015] The thickness of each layer of the semiconductor multilayer film is determined based on the wavelength of the incident light IL incident from the light incident surface IS. Specifically, for example, the thickness of each layer of the semiconductor multilayer film is preferably set to ¼ of the wavelength of the incident light IL within the layer.

[0016] The light guide layer 15 is provided on the upper surface of the lower reflective layer 13 and is a layer capable of guiding light incident from the light incident surface IS. Specifically, for example, the light guide layer 15 is a layer made of GaAs.

[0017] The upper reflective layer 17 as a distributed Bragg reflector layer is a layer forming a distributed Bragg reflector (DBR) structure formed by semiconductor multilayer films stacked on the light guide layer 15 in a direction perpendicular to the upper surface of the substrate 11. That is, the upper reflective layer 17 and the lower reflective layer 13 sandwich the light guide layer 15 therebetween.

[0018] For example, the upper reflective layer 17 is an AlAs / GaAs semiconductor multilayer film in which thin AlAs films and thin GaAs films are alternately laminated. As with the lower reflective layer 13, the thickness of each 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 thickness of each layer of the semiconductor multilayer film is preferably ¼ the wavelength of the incident light IL within the layer.

[0019] The upper reflective layer 17 has a cutout portion 17A cut into a rectangular parallelepiped shape from above the optical deflection module at one end in the longitudinal direction of the optical deflection module 10. The cutout portion 17A terminates within the upper reflective layer 17 and is exposed by the cutout portion 17A, with the surface facing upward being the above-mentioned light incident surface IS.

[0020] The upper surface of the upper reflective layer 17 other than the region where the cutout portion 17A is formed serves as the light exit surface ES described above. The light exit surface ES forms an inclined surface that approaches the upper surface of the substrate 11 as it moves away from the cutout portion 17A. That is, as it moves away from the cutout portion 17A, the number of layers in the semiconductor multilayer film of the upper reflective layer 17 decreases, and the thickness of the upper reflective layer 17 decreases.

[0021] Such an inclined surface can be formed, for example, by laminating a semiconductor multilayer film on the light guide layer 15 and then performing etching using a 3D photomask (grayscale mask).

[0022] In addition, in the region below the light exit surface ES in the direction perpendicular to the top surface of the substrate 11, the number of layers in the semiconductor multilayer film of the upper reflective layer 17 is smaller than the number of layers in the semiconductor multilayer film of the lower reflective layer 13. That is, the reflectance of the lower reflective layer 13 to the incident light IL is greater than that of the upper reflective layer 17. As an example, in this embodiment, the lower reflective layer 13 is configured by laminating 40 pairs of layers, each of which is made of AlAs / GaAs, and the upper reflective layer 17 is configured by laminating 20 pairs of layers, each of which is made of AlAs / GaAs, at its thickest portion.

[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 FIG. 2, in the above-mentioned optical deflection module 10, when light is incident into the optical waveguide from the light incident surface IS, the light in the optical waveguide propagates (waveguided) within the light guiding layer 15 while being reflected by the lower reflective layer 13 and the upper reflective layer 17 provided on the lower and upper surfaces of the light guiding layer 15.

[0025] As described above, the upper reflective layer 17 is configured to have a lower optical reflectance than the lower reflective layer 13, and therefore, of the light propagating through the light guide layer 15, the light that leaks out without being reflected by the upper reflective layer 17 is emitted from a light exit surface ES on the upper surface of the upper reflective layer 17. That is, after the light propagating through the light guide layer 15 enters from the light incident surface IS, it is gradually emitted from the light exit surface ES and attenuated as it propagates away from the light incident surface IS.

[0026] Here, the internal propagation angle θi in the optical waveguide is approximately expressed by the following formula (1): In formula (1), λ is the wavelength of the incident light, and λc is the cutoff wavelength, which is the shortest wavelength of light that can be propagated in single mode in the optical waveguide.

[0027]

number

[0028] Therefore, from Snell's law, the deflection angle θr of light emitted from the exit surface on the upper surface of the upper reflective layer 17 of the optical deflection module 10 is expressed by the following formula (2): In formula (2), n is the average refractive index of the optical waveguide.

[0029]

number

[0030] As can be seen from the above formula, according to the light 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 configured such that light propagating through the light guide layer 15 gradually leaks out from the upper reflective layer 17, like the optical deflection module 10 of this embodiment, the light propagating through the light guide layer is attenuated little by little as it propagates. Therefore, if the thickness of the upper reflective layer 17, i.e., the number of layers of the semiconductor multilayer film of the upper reflective layer 17, is constant over the entire lower part of the light exit surface ES, the intensity of the light exiting from the light exit surface ES becomes smaller as it moves away from the light incident surface IS.

[0032] In the optical deflection module 10 of this embodiment, as described above, the number of layers in the semiconductor multilayer film of the upper reflective layer 17 decreases as the distance from the cutout portion 17A that provides the light incident surface IS increases, and the thickness of the upper reflective layer 17 decreases. Therefore, the reflectance of the upper reflective layer 17 decreases as the distance from the light incident surface IS increases, and the proportion of light leaking 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 exit surface ES caused by the attenuation of the light propagating through the light guide layer 15.

[0033] Fig. 3 shows a graph of the intensity of the emitted light EL from the light exit surface ES in a region along the cross section shown in Fig. 2. In this graph, the horizontal axis represents the distance L from the light entrance surface IS along the cross section of Fig. 2, and the vertical axis represents the intensity of the emitted light EL. Fig. 3 shows a case where the light intensity of the emitted light EL is constant across the light exit surface ES.

[0034] As described above, in the light deflection module 10 of this embodiment, the number of layers of the semiconductor multilayer film of the upper reflective layer 17 is reduced according to the attenuation rate of light propagating through the light guide layer 15, that is, according to the distance from the light incident surface IS. Therefore, according to the light deflection module 10 of this embodiment, the intensity of the emitted light EL can be made constant across the light exit surface ES, as shown in FIG.

[0035] 2 illustrates a case where the inclination of the light exit surface ES, which is the upper surface of the upper reflective layer 17, is constant and the light exit surface ES is straight in cross section. However, when the light intensity of the emitted light EL is constant across the light exit surface ES, the inclination of the light exit surface may change midway depending on, for example, the attenuation rate of light propagating through the light guide layer 15. Furthermore, the light exit surface ES may be curved in cross section.

[0036] Also, 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 of the upper reflective layer 17 according to the distance from the light incident surface IS, for example. For example, if it is desired to weaken the intensity of the desired emitted light EL the farther it is from the light incident surface IS, the number of layers of the semiconductor multilayer film of the upper reflective layer 17 may be increased to increase the reflectance of the upper reflective layer 17 the farther it is from the light incident surface IS. EXAMPLES

[0037] Second embodiment An optical deflection module 20 according to the present invention will be described. The optical deflection module 20 according to the second embodiment is a module intended to give a Gaussian distribution to the intensity of the output light EL in the longitudinal direction of the optical deflection module 20.

[0038] Fig. 4 shows a cross-sectional view of the optical deflection module 20 in the same cross section as Fig. 2. The optical deflection module 20 of the second embodiment has the same configuration as the optical deflection module 10 of the first embodiment, except for the shape of the upper reflective layer 17. Therefore, in the following description, descriptions of layers other than the upper reflective layer 17 will be omitted. In Fig. 4, the shape of the light exit surface ES of the optical deflection module 10 of the first embodiment is indicated by a dashed line.

[0039] 4, in the optical deflection module 20, the shape of the light exit surface ES is recessed toward the substrate 11 from the region around a plane CS that includes the center line in the longitudinal direction of the light exit surface ES and is perpendicular to the cross section, based on the shape of the optical deflection module 10. That is, the thickness of the upper reflective layer 17, in other words the reflectance of the upper reflective layer 17, is smallest in the central region in the longitudinal direction of the light exit surface ES.

[0040] Fig. 5 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 Fig. 4. As in Fig. 3, in this graph, the horizontal axis represents the distance L from the light incident surface IS along the cross section of Fig. 4, and the vertical axis represents the intensity of the emitted light EL.

[0041] As described above, in the light deflection module 20, the thickness of the upper reflective layer 17 is decreased according to the distance from the light incident surface IS, and the shape of the light exit surface ES is recessed around the area around the surface CS of the light exit surface ES. In this way, it is possible to make the intensity distribution of the exit light EL a Gaussian distribution or a distribution close to it, as shown in FIG.

[0042] The shape of the light exit surface ES in the cross section shown in Fig. 4 may be obtained by combining an ideal Gaussian distribution shape obtained by inverting it upside down with the inclined shape of the light exit surface ES in Example 1. In this way, it is possible to obtain a distribution of the exit light EL that is symmetric in the direction along the cross section of Fig. 4, taking into account the attenuation of light in the light guide layer 15.

[0043] As described above, in the light deflection module 20, the reflectance of the upper reflective layer 17 changes according to the distance from the light incident surface IS and according to the desired output intensity distribution of the output light EL output from the light exit surface ES.

[0044] The intensity distribution of the output light EL having a Gaussian distribution realized by the optical deflection module 20 does not change much even when it propagates. Therefore, for example, the intensity distribution of the incident light is not disturbed even when the light is incident on a light detection module or the like after being output from the optical deflection module 20, and it becomes easy to process a signal generated by the incident light.

[0045] As in Example 1, the shape of the light exit surface ES of the optical deflection module 20 can also be formed, for example, by stacking a semiconductor multilayer film on the light-guiding layer 15 and then performing etching using a 3D photomask (grayscale mask). EXAMPLES

[0046] Third Embodiment A light deflection module 30 according to a third embodiment of the present invention will be described below. The light deflection module 30 is a module intended to impart a circular distribution to the intensity of the output light EL.

[0047] 6 shows a top view of the light deflection module 30. The light deflection module 30 of the third embodiment has the same configuration as the light deflection module 10 of the first embodiment, except for the aspect ratio of the top surface shape and the shape of the upper reflective layer 17. Therefore, in the following description, descriptions of layers other than the upper reflective layer 17 will be omitted.

[0048] As shown in Fig. 6, the light exit surface ES of the optical deflection module 30 has a recess formation region RR (within the dashed line in the figure) in the center. Within the recess formation region RR, a donut-shaped (annular) recess RP is formed with a central point P as the center. In Fig. 6, to make the shape easier to understand, a gradation is applied, with deep recesses being darker and shallow recesses being lighter.

[0049] Fig. 7 shows a cross-sectional view taken along line 7-7 passing through the center point P in Fig. 6, and Fig. 8 shows a cross-sectional view taken along section 8-8 in Fig. 6. Note that in Figs. 7 and 8, the shape of the light exit surface ES of the light deflection module 10 of the first embodiment is indicated by a dashed line.

[0050] As shown in FIGS. 7 and 8, the shape of the light exit surface ES is based on the shape of the light deflection module 10, and has an annular recess RP.

[0051] The cross section shown in Fig. 7, i.e., the cross section passing through the center point P, is a cross section taken along the center line of the annular recess RP. Therefore, in Fig. 7, the two recesses RP1 and RP2 are shown as being aligned along this cross section. Furthermore, the recess RP2 is deeper than the recess RP1.

[0052] The cross section shown in Fig. 8 is a cross section of a region close to the end of the annular recess RP, and therefore, in Fig. 8, it is shown as if one shallow recess was formed.

[0053] Fig. 9 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 Fig. 7. As in Fig. 3, in this graph, the horizontal axis represents the distance L from the light incident surface IS along the cross section of Fig. 7, and the vertical axis represents the intensity of the emitted light EL.

[0054] As described above, in the light deflection module 30, the thickness of the upper reflective layer 17 is decreased according to the distance from the light incident surface IS, and the light exit surface ES is formed with an annular recess RP centered on the central point P of the light exit surface ES. That is, in the light deflection module 30, an annular region having a lower reflectance than the surrounding area is formed in the light exit surface ES.

[0055] By doing so, it is possible to make the intensity distribution of the output light EL a distribution having an annular region where the light intensity is high and a region where the light intensity is low that is surrounded by the annular region.

[0056] In addition, Fig. 9 shows a light intensity distribution having two peaks according to the cross-sectional shape shown in Fig. 7. In addition, the recess RP2 farther from the light incident surface IS is formed deeper than the recess RP1, that is, the reflectance of the upper reflective layer 17 is lower in the region where the recess RP2 is provided. Therefore, regardless of the attenuation of light in the light guide layer 15, a symmetric light intensity distribution is realized.

[0057] The shape of the annular recess may be obtained by combining an ideal light intensity distribution shape obtained by inverting it upside down with the inclined shape of the light exit surface ES of Example 1. In this way, it is possible to obtain a symmetric distribution of the exit light EL over the entire light exit surface ES, taking into account the attenuation of light in the light guide layer 15.

[0058] As described above, in the light deflection module 30, the reflectance of the upper reflective layer 17 changes according to the distance from the light incident surface IS and according to the desired output intensity distribution of the output light EL output from the light exit surface ES.

[0059] The output light EL having a circular distribution realized by the optical deflection module 30 is not significantly affected by lens aberration. Therefore, for example, when the output light EL output from the optical deflection module 30 is condensed by a lens, it is easy to reduce the spot diameter of the condensed beam.

[0060] As in the first and second embodiments, the shape of the light exit surface ES of the optical deflection module 30 can also be formed, for example, by stacking a semiconductor multilayer film on the light-guiding 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 are formed of 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] 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 in the above-described embodiment are merely examples and can be appropriately selected according to the application, etc. [Explanation of symbols]

[0064] 10, 20, 30 Light deflection module 11 Substrate 13 Lower reflective layer 15 Light guiding layer 17 Upper reflective layer IS light incidence surface ES light exit surface

Claims

[Claim 1] a light guiding layer through which light is guided; a first distributed Bragg reflector layer formed on one surface of the light guide layer and having a light incident surface through which the light enters the light guide layer and a light exit surface through which the light exits, on a surface opposite to a surface facing the light guide layer; a second distributed Bragg reflector layer formed on the other surface of the light guiding layer; 1. An optical deflection module comprising:

Images