JP7215266B2 - Surface emitting laser element, light source device and detection device - Google Patents

Description

The present invention relates to a surface emitting laser element, a light source device and a detection device.

A vertical cavity surface emitting laser (VCSEL) is a semiconductor laser that emits laser light in a direction perpendicular to a substrate. Compared to edge-emitting semiconductor lasers that emit light parallel to the substrate, surface-emitting lasers have advantages such as low threshold current oscillation, single longitudinal mode oscillation, and the ability to form a two-dimensional array. characteristics.

Application fields of surface-emitting lasers include light sources for optical writing systems in printers, excitation light sources for solid-state lasers, and light sources for three-dimensional sensors and range finding sensors. In these application fields, it is desired that the light emitted from the surface emitting laser element has a single transverse mode and a high output. For this purpose, it is important to suppress the oscillation of the high-order transverse mode, and various attempts have been made so far. For example, a surface-emitting laser device has been disclosed for the purpose of improving the stability of the polarization direction while controlling the oscillation of higher-order transverse modes (Patent Document 1).

According to the surface-emitting laser device described in Patent Document 1, although the intended purpose can be achieved, there is room for further study on the structure for suppressing higher-order transverse modes.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface emitting laser device, a light source device, and a detection device capable of obtaining high output while suppressing high-order transverse modes.

According to one aspect of the disclosed technology, a surface-emitting laser element includes a laser structure that emits light having an oscillation wavelength of λ from an emission surface, and a laser structure provided in an emission region of the emission surface, and a second laser structure in the center of the emission region. and a film that makes a second reflectance of the peripheral portion around the central portion lower than the reflectance of 1, and the second reflectance is 0.984 times or more the first reflectance. 0.998 times or less, the optical thickness of the film in the peripheral portion is set to be shifted from an odd multiple of λ/4, and is λ/4±αλ, and α is 0.05 or more and 0.18 It is below .

According to the disclosed technique, high output can be obtained while suppressing high-order transverse modes.

1 is a top view showing a surface emitting laser device according to a first embodiment; FIG. 1 is a cross-sectional view showing a surface emitting laser device according to a first embodiment; FIG. FIG. 4 is a cross-sectional view (part 1) showing a method of manufacturing the surface-emitting laser element 100 according to the first embodiment; FIG. 2 is a cross-sectional view (part 2) showing the method of manufacturing the surface-emitting laser device 100 according to the first embodiment; 3 is a cross-sectional view (No. 3) showing the method of manufacturing the surface-emitting laser element 100 according to the first embodiment; FIG. 4 is a cross-sectional view (No. 4) showing the method of manufacturing the surface-emitting laser device 100 according to the first embodiment; FIG. 5 is a cross-sectional view (No. 5) showing the method of manufacturing the surface-emitting laser device 100 according to the first embodiment; FIG. It is a top view which shows an example of an etching mask. FIG. 4 is a top view showing an example of a resist pattern; 4 is a graph showing the relationship between the reflectance of the upper semiconductor multilayer film reflector and the reflectance within the emission area. 5 is a graph showing injection current (I)-optical output (L) characteristics of the first reference example and the second reference example. 5 is a graph showing injection current (I)-optical output (L) characteristics of the first embodiment, the first reference example, and the second reference example. FIG. 5 is a top view showing a surface emitting laser device according to a second embodiment; FIG. 5 is a cross-sectional view showing a surface-emitting laser device according to a second embodiment; It is a top view which shows the 1st modification of 1st Embodiment. It is a top view which shows the 2nd modification of 1st Embodiment. FIG. 11 is a top view showing a surface emitting laser device according to a third embodiment; FIG. 10 is a cross-sectional view showing a surface-emitting laser device according to a third embodiment; It is a figure which shows the outline|summary of the range finder as an example of a detection apparatus.

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration may be denoted by the same reference numerals, thereby omitting redundant description. In the following description, the laser oscillation direction is defined as the Z-axis direction, and two mutually orthogonal directions within a plane perpendicular to the Z-axis direction are defined as the X-axis direction and the Y-axis direction. Also, the positive Z-axis direction is defined as upward. However, the surface emitting laser element or the like can be used upside down, and can be arranged at any angle.

(First embodiment)
First, the first embodiment will be described. The first embodiment relates to a surface emitting laser device. FIG. 1A is a top view showing the surface emitting laser device according to the first embodiment. FIG. FIG. 1B is a cross-sectional view showing the surface emitting laser device according to the first embodiment. FIG. 1B corresponds to a cross-sectional view taken along line II in FIG. 1A.

As shown in FIGS. 1A and 1B, a surface-emitting laser device 100 according to the first embodiment is a surface-emitting laser with an oscillation wavelength of 940 nm, and includes a substrate 101, a lower semiconductor multilayer reflector 103, a lower It has a spacer layer 104, an active layer 105, an upper spacer layer 106, an upper semiconductor multilayer reflector 107, a contact layer 109, a p-side electrode 113, an n-side electrode 114, and an adjustment film 115. there is A substrate 101, a lower semiconductor multilayer reflector 103, a lower spacer layer 104, an active layer 105, an upper spacer layer 106, an upper semiconductor multilayer reflector 107, a contact layer 109, a p-side electrode 113, An n-side electrode 114 and are included in the laser structure 120 .

For the substrate 101, for example, the normal direction of the mirror-polished surface (principal surface) of the surface is 15 degrees (θ=15 degrees) toward the crystal orientation [111] A direction with respect to the crystal orientation [100] direction. It is a tilted n-GaAs single crystal semiconductor substrate. That is, the substrate 101 is a so-called tilted substrate. Note that the substrate is not limited to the above.

The lower semiconductor multilayer reflector 103 is laminated on the +Z side (upper side) of the substrate 101 via a buffer layer (not shown), and includes a low refractive index layer 103a made of n-Al _0.9 Ga _0.1 As. It has about 30 pairs with the high refractive index layer 103b made of n-Al _0.2 Ga _0.8 As. A composition gradient layer (not shown) having a thickness of 20 nm in which the composition is gradually changed from one composition to the other is provided between the refractive index layers in order to reduce the electrical resistance. there is Each refractive index layer is set to have an optical thickness of λ/4, where λ is the oscillation wavelength, including 1/2 of the adjacent composition gradient layer. Note that when the optical thickness is λ/4, the actual thickness D of the layer is D=λ/4n (where n is the refractive index of the medium of the layer).

The lower spacer layer 104 is laminated on the +Z side (upper side) of the lower semiconductor multilayer reflector 103 and is a layer made of non-doped AlGaInP. The material of the lower spacer layer 104 is not limited to non-doped AlGaInP, and may be, for example, non-doped AlGaAs.

The active layer 105 is laminated on the +Z side (upper side) of the lower spacer layer 104 and has a triple quantum well structure including three quantum well layers and four barrier layers. Each quantum well layer is made of InGaAs and each barrier layer is made of AlGaAs.

The upper spacer layer 106 is laminated on the +Z side (upper side) of the active layer 105 and is a layer made of non-doped AlGaInP. The material of the upper spacer layer 106 is not limited to non-doped AlGaInP like the lower spacer layer 104, but may be non-doped AlGaAs, for example.

A portion composed of the lower spacer layer 104, the active layer 105 and the upper spacer layer 106 is also called a resonator structure, and its thickness is set to be the optical thickness of one wavelength. The active layer 105 is provided at the center of the resonator structure, which is the position corresponding to the antinode in the standing wave distribution of the electric field, so as to obtain a high stimulated emission probability.

The upper semiconductor multilayer film reflector 107 is laminated on the +Z side (upper side) of the upper spacer layer 106, and includes a low refractive index layer 107a made of p-Al _0.9 Ga _0.1 As and p-Al _0.2 Ga ₀ It has about 20 pairs with the high refractive index layer 107b made of _0.8 As. A composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other is provided between the refractive index layers in order to reduce the electrical resistance. Each refractive index layer includes 1/2 of the adjacent composition gradient layer and is set to have an optical length of λ/4 (λ: oscillation wavelength).

In one of the low refractive index layers 107a in the upper semiconductor multilayer film reflector 107, a selectively oxidized layer 108 made of p-AlAs is inserted with a thickness of about 30 nm. The insertion position of the selectively oxidized layer 108 is a position corresponding to the second node from the active layer 105 in the electric field standing wave distribution. The selectively oxidized layer 108 comprises a non-oxidized region 108b and a surrounding oxidized region 108a.

The contact layer 109 is laminated on the +Z side (upper side) of the upper semiconductor multilayer film reflector 107 and is a layer made of p-GaAs.

The adjustment film 115 is provided on the +Z side (upper side) of the contact layer 109 and in the emission region 112 of the emission surface 120A of the laser structure 120 . The adjustment film 115 includes a dielectric film 111 provided in an annular shape in the peripheral portion 112P around the central portion 112C of the emission region 112, and the reflectance of the peripheral portion 112P is lower than the reflectance of the central portion C. there is The optical thickness of the dielectric film 111 is set to be offset from an odd multiple of λ/4, eg, λ/4±0.1λ. In the emission region 112, the ratio (R _low /R _high ) of the reflectance (R _high ) of the central portion 112C and the reflectance (R _low ) of the peripheral portion 112P, which is the portion provided with the dielectric film 111, is 0. It is in the range of 0.984 or more and 0.998 or less. That is, the reflectance (R _low ) of the peripheral portion 112P is 0.984 to 0.998 times the reflectance (R _high ) of the central portion 112C. For example, the area of the central portion 112C of the emission region 112 is 85% or less of the area of the non-oxidized region 108b. The reflectance (R _high ) of the central portion 112C is an example of the first reflectance, the reflectance (R _low ) of the peripheral portion 112P is an example of the second reflectance, and the adjustment film 115 is the first reflectance. This is an example of a film that makes the second reflectance lower than the reflectance. Dielectric film 111 is an example of a first film. The adjustment film 115 is also called a mode filter.

Next, a method for manufacturing the surface emitting laser device 100 will be briefly described. Note that, as described above, a structure in which a plurality of semiconductor layers are stacked on the substrate 101 is hereinafter also referred to as a "stacked body" for the sake of convenience. 2A to 2E are cross-sectional views showing a method of manufacturing the surface emitting laser device 100 according to the first embodiment.

The laminate is formed by crystal growth by metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) (see FIG. 2A).

Here, in the case of the MOCVD method, trimethylaluminum (TMA), trimethylgallium (TMG), and trimethylindium (TMI) are used as group III raw materials, and phosphine (PH ₃ ) and arsine are used as group V raw materials. (AsH ₃ ) is used. Nitrogen tetrabromide (CBr ₄ ) and dimethyl zinc (DMZn) are used as raw materials for the p-type dopant, and hydrogen selenide (H ₂ Se) is used as the raw material for the n-type dopant.

A square resist pattern is formed on the surface of the laminate.

By the ECR etching method using Cl ₂ gas, the resist pattern is used as a photomask to form a substantially quadrangular prism mesa structure. Here, the bottom of the etch is positioned in the lower spacer layer 104 .

The photomask is now removed (see FIG. 2B).

The laminate is heat treated in water vapor. As a result, Al (aluminum) in the selectively oxidized layer 108 is selectively oxidized from the outer peripheral portion of the mesa structure, and a non-oxidized region 108b surrounded by an Al oxidized region 108a is formed in the central portion of the mesa structure. remains (see FIG. 2C). That is, a so-called oxidized constriction structure is formed, which restricts the path of the drive current for the light-emitting portion only to the central portion of the mesa structure. The non-oxidized region 108b is the current passing region. In this manner, a substantially square current passing region having a width of, for example, about 5 μm to 7 μm is formed. The degree of oxidation of the selectively oxidized layer 108 is, for example, such that the area of the central portion 112C of the emission region 112 is 85% or less of the area of the non-oxidized region 108b.

A dielectric film 111 made of SiN is formed using a chemical vapor deposition (CVD) method (see FIG. 2D). Here, the optical thickness of the dielectric film 111 is about (λ/4)−0.5 so that the reflectance of the peripheral portion 112P of the output region 112 is about 1% lower than the reflectance of the central portion 112C. 1λ (=0.15λ). Specifically, since the refractive index n of SiN is about 1.86 and the oscillation wavelength λ is 940 nm, the actual thickness of the dielectric film 111 is set to about 75 nm.

An etching mask (referred to as mask C) for opening a p-type electrode contact window is fabricated on the upper side (+Z side) of the mesa structure that will be the laser light emitting surface 120A. Here, as an example, as shown in FIG. 3A, a covering portion C1 covering the periphery of the mesa structure, the side surface of the mesa structure, and the periphery of the upper surface of the mesa structure, and the peripheral portion 112P of the emission region 112 are covered. A mask C having a covering portion C2 is produced.

The dielectric film 111 is etched with buffered hydrofluoric acid (BHF) to open a p-side electrode contact window.

Mask C is removed. The dielectric film 111 remaining in the peripheral portion 112P of the emission region 112 is included in the adjustment film 115 (see FIG. 2E).

A resist pattern M is formed in a region that will become the emission region 112 above the mesa structure, and a p-side electrode material is vapor-deposited. Here, as shown in FIG. 3B as an example, the resist pattern M includes a covering portion M1 covering the periphery of the mesa structure, the sides of the mesa structure, and the periphery of the upper surface of the mesa structure, and an adjustment film 115. and a circular covering portion M2 for covering.

A multi-layered film of Cr/AuZn/Au or a multi-layered film of Ti/Pt/Au is used as the p-side electrode material. The electrode material deposited on the emission region 112 is lifted off to form the p-side electrode 113 . A region surrounded by the p-side electrode 113 becomes the emission region 112 .

After polishing the back side of the substrate 101 to a predetermined thickness (for example, about 200 μm), the n-side electrode 114 is formed. Here, the n-side electrode 114 is a multilayer film made of AuGe/Ni/Au.

Annealing establishes ohmic conduction between the p-side electrode 113 and the n-side electrode 114 . As a result, the mesa structure becomes a light emitting portion.

After that, each chip is cut.

Then, through various post-processes, the surface-emitting laser device 100 is obtained.

Next, the effect of the surface emitting laser device 100 will be described with reference to a reference example.

In the first reference example, instead of the dielectric film 111 having the above optical thickness, the adjustment film 115 includes a dielectric film whose optical thickness is an odd multiple of λ/4. In the second reference example, it is assumed that the adjustment film 115 is not provided. FIG. 4 is a graph showing the relationship between the reflectance of the upper semiconductor multilayer film reflector and the reflectance in the emission area. FIG. 5 is a graph showing injection current (I)-optical output (L) characteristics of the first reference example and the second reference example.

In the first reference example, if the reflectance of the upper semiconductor multilayer film reflector 107 is reduced by reducing the number of layers of the upper semiconductor multilayer film reflector 107 to increase the light extraction efficiency, the reflectance of the central portion 112C And the reflectance of the peripheral portion 112P decreases. At this time, as shown in FIG. 4, the amount of decrease in reflectance is greater in the peripheral portion 112P than in the central portion 112C. When the difference in reflectance between the central portion 112C and the peripheral portion 112P increases, the adjustment film 115 not only suppresses higher-order transverse modes, but also affects the oscillation of the fundamental transverse mode. As a result, as shown in FIG. 5, in the first reference example, the oscillation threshold current increases and the output value decreases as compared with the second reference example. That is, according to the first reference example, as compared with the second reference example, the high-order transverse mode is suppressed, but the output characteristics are deteriorated. As described above, in the first reference example in which the dielectric film having an optical thickness that is an odd multiple of λ/4 is provided, high-output light extraction efficiency is improved while suppressing high-order transverse mode oscillation. A surface emitting laser device cannot be realized.

On the other hand, in the first embodiment, the optical thickness of the dielectric film 111 included in the adjustment film 115 is set to be shifted from an odd multiple of λ/4, and the reflectance (R _high ) and the reflectance (R _low ) (R _low /R _high ) is in the range of 0.984 to 0.998. According to the first embodiment, even when the reflectance of the upper semiconductor multilayer film reflector 107 is low, high-order transverse modes can be suppressed while suppressing the influence on the fundamental transverse mode, according to the following principle. . Therefore, even if the reflectance of the upper semiconductor multilayer film reflector 107 is lowered and the light extraction efficiency is increased, the divergence angle can be narrowed while ensuring good output characteristics. The principle by which the above effects are obtained will be described below.

(1) In order to increase the output of the surface emitting laser, it is conceivable to increase the light extraction efficiency.

(2) In order to increase the light extraction efficiency, it is conceivable to lower the reflectance of the upper semiconductor multilayer film reflector 107 by reducing the number of layers of the upper semiconductor multilayer film reflector 107 .

(3) When the reflectance of the upper semiconductor multilayer film reflector 107 is lowered, the reflectance is lowered both in the central portion 112C and the peripheral portion 112P.

(4) As in the first reference example, if the peripheral portion 112P is provided with a dielectric film whose optical thickness is an odd multiple of λ/4, the number of layers of the upper semiconductor multilayer reflector 107 is reduced. The decrease in reflectance becomes more pronounced in the peripheral portion 112P than in the central portion 112C (see FIG. 4).

(5) If the reflectance ratio (R _low /R _high ) is less than 0.984, the effect of suppressing the fundamental transverse mode that spreads slightly to the peripheral portion 112P works, resulting in deterioration of the characteristic of the fundamental transverse mode. It has been found to That is, it has been found that the oscillation threshold current increases and the output value decreases. Further, it has been found that when the reflectance ratio (R _low /R _high ) exceeds 0.998, the effect of the high-order transverse mode suppressing structure is reduced and the divergence angle is less likely to be narrowed.

(6) On the other hand, in the first embodiment, the adjustment film 115 including the dielectric film 111 having an appropriate optical thickness is provided. Therefore, by reducing the number of layers of the upper semiconductor multilayer reflector 107 and lowering the reflectance of the central portion 112C, the higher-order transverse mode is suppressed in the peripheral portion 112P while suppressing the deterioration of the characteristics of the fundamental transverse mode. be able to.

Here, as a specific example, characteristics when the oscillation wavelength λ of the laser structure is in the 940 nm band will be described below. If the reflectance of the upper semiconductor multilayer reflector 107 is lowered from 99.61% to 99.15%, the optical output can be increased by about 30%, but the optical thickness of the dielectric in the peripheral portion 112P is reduced by λ When fixed at an odd multiple of /4, the reflectance of the peripheral portion 112P is lowered from 98.67% to 97.09%. At this time, the reflectance ratio (R _low /R _high ) is 0.979, which is out of the range of 0.984 to 0.998. In this case, depending on the area of the central portion 112C, as shown in FIG. 5, the adjustment film 115 affects oscillation in the fundamental transverse mode, increasing the oscillation threshold current and decreasing the output value. On the other hand, if the optical thickness of the dielectric in the peripheral portion 112P is (λ/4)−0.1λ (=0.15λ), the reflectance ratio (R _low /R _high ) should be 0.993. and can be designed within the range of 0.984 to 0.998. In this case, as shown in FIG. 6, even if the adjustment film 115 is provided, neither an increase in the oscillation threshold current nor a decrease in output characteristics occurs. Also, the divergence angle can be narrowed by the action of the adjustment film 115 . FIG. 6 is a graph showing injection current (I)-optical output (L) characteristics of the first embodiment, the first reference example, and the second reference example.

Tables 1 and 2 show the shift amount αλ of the optical thickness of the dielectric film 111 from λ/4 with respect to the reflectance of the upper semiconductor multilayer film reflector 107 (reflectance of the central portion 112C) and the reflectance. The relationship with the ratio (R _low /R _high ) is shown. In Tables 1 and 2, the reflectance ratio (R _low /R _high ) within the range of 0.984 to 0.998 is underlined. It can be seen from Tables 1 and 2 that the reflectance ratio (R _low /R _high ) increases as the shift amount from λ/4 increases. When the reflectance of the upper semiconductor multilayer film reflector 107 is high (99.346 or more), the reflectance ratio (R _low /R _high ) is 0.984 to 0 even if the shift amount αλ is 0. It is in the range of .998. On the other hand, when the reflectance of the upper semiconductor multilayer film reflector 107 is low (less than 99.346), when the shift amount αλ is 0, the reflectance ratio (R _low /R _high ) is 0.984 to 0. out of the .998 range. Therefore, |αλ| is greater than zero.

By setting the shift amount αλ from λ/4 to |αλ|>0 in this way, the reflectance ratio (R _low /R _high ) can be increased, and the output characteristics can be improved. The matter was discovered by the present inventors for the first time. In particular, according to Tables 1 and 2, it is preferable that α is 0.05 or more and 0.18 or less, and that the optical thickness of the peripheral portion 112P of the adjustment film 115 is λ/4±αλ.

Furthermore, according to this embodiment, even if the reflectance of the upper semiconductor multilayer film reflector 107 is small, the reflectance ratio (R _low /R _high ) can be increased to improve the output characteristics. The reflectance (R _low ) of the peripheral portion 112P is preferably 98% or more. This is because if the reflectance (R _low ) of the peripheral portion 112P is less than 98%, the output region 112 may not have sufficient reflectance.

Note that the material of the dielectric film 111 is not limited to SiN. For example, SiNx, SiOx, TiOx, or SiON may be used as the material transparent to the oscillation wavelength λ. A similar effect can be obtained by adjusting the thickness of the dielectric film 111 according to the refractive index of each material. Further, the material of the adjustment film 115 is not limited to a dielectric material as long as it has transparency to the oscillation wavelength λ. For example, a semiconductor can be used as the material of the adjustment film 115 .

(Second embodiment)
Next, a second embodiment will be described. The second embodiment differs from the first embodiment in the configuration of the adjustment film 115 . FIG. 7A is a top view showing a surface emitting laser device according to a second embodiment. FIG. 7B is a cross-sectional view showing the surface emitting laser device according to the second embodiment. FIG. 7B corresponds to a cross-sectional view taken along line II in FIG. 7A.

As shown in FIGS. 7A and 7B, the surface-emitting laser device 200 according to the second embodiment has a dielectric film 111 formed in the entire emission region 112 in addition to the dielectric film 111 in the emission region 112. 116. The dielectric film 116 is, for example, a SiN film with an optical thickness of 2λ/4. The actual thickness of the dielectric film 116 is about 252 nm, which is substantially equal to 2λ/4n because the refractive index n of SiN is 1.86 and the oscillation wavelength is 940 nm. The adjustment film 115 includes a dielectric film 111 and a dielectric film 116 within the emission region 112 . Dielectric film 116 is an example of a second film.

A dielectric film 116 having an optical thickness of 2λ/4 is provided in the central portion 112C of the emission region 112 . A dielectric film 111 and a dielectric film 116 are provided in the peripheral portion 112P of the emission region 112. As shown in FIG. The optical thickness of the dielectric film 111 is (λ/4)−0.1λ (=0.15λ), and the optical thickness of the dielectric film 116 is 2λ/4. A dielectric film made of SiN having a nominal thickness of (3λ/4)−0.1λ (=0.65λ) is provided. A peripheral portion of the output region excluding the high-order transverse mode suppressing structure, ie, a portion where the p-side electrode is missing, is also covered with a protective film (dielectric film) having an optical thickness of 2λ/4.

The dielectric film 111 is provided on the upper surface of the mesa structure, and the periphery of the mesa structure and the side surfaces of the mesa structure are covered with a dielectric film 116 . Other configurations are the same as those of the first embodiment.

Effects similar to those of the first embodiment can also be obtained by the second embodiment.

Further, in the second embodiment, since the entire emission region 112 is covered with the dielectric film 116, oxidation and contamination of the emission region 112 can be suppressed. Although the central portion 112C is covered with the dielectric film 116, since the optical thickness of the dielectric film 116 is an even multiple of λ/4, it is possible to prevent a decrease in reflectance. An optical characteristic equivalent to that without is obtained.

Note that the planar shape of the dielectric film 111 is not limited to an annular shape. As shown in FIG. 8A, in the first embodiment, two dielectric films 111A may be provided by dividing the ring into two. Further, as shown in FIG. 8B, in the first embodiment, four dielectric films 111B obtained by dividing the ring into four may be provided. FIG. 8A is a top view showing a first modification of the first embodiment; FIG. FIG. 8B is a top view showing a second modification of the first embodiment; In the second embodiment, two dielectric films 111A may be provided by dividing the ring into two, or four dielectric films 111B may be provided by dividing the ring into four.

(Third Embodiment)
Next, a third embodiment will be described. The third embodiment differs from the first embodiment in the configuration of the adjustment film 115. FIG. FIG. 9A is a top view showing a surface emitting laser device according to the third embodiment. FIG. 9B is a cross-sectional view showing a surface emitting laser device according to the third embodiment. FIG. 9B corresponds to a cross-sectional view taken along line II in FIG. 9A.

As shown in FIGS. 9A and 9B, a surface emitting laser device 300 according to the third embodiment has a dielectric film 117 in a central portion 112C and dielectric films 111 in a central portion 112C and a peripheral portion 112P. . The dielectric film 117 is provided between the dielectric film 111 and the contact layer 109 in the thickness direction. The sum of the optical thicknesses of the dielectric films 111 and 117 in the central portion 112C is an odd multiple of λ/4. The refractive index of dielectric film 117 is lower than the refractive index of dielectric film 111 . For example, dielectric film 117 is a SiO ₂ film and the refractive index of dielectric film 117 is about 1.5. Adjustment film 115 includes dielectric film 111 and dielectric film 117 in emission region 112 . Dielectric film 117 is an example of a third film. Other configurations are the same as those of the first embodiment.

In the third embodiment, in the central portion 112C, the laminate of the dielectric films 111 and 117 functions as part of the multilayer reflector. Moreover, since only the dielectric film 111 is provided in the peripheral portion 112P, the reflectance of the peripheral portion 112P is lower than the reflectance of the central portion 112C.

Effects similar to those of the first embodiment can also be obtained by the third embodiment.

Further, in the third embodiment, since the entire emission region 112 is covered with the dielectric film 117, oxidation and contamination of the emission region 112 can be suppressed. The central portion 112C is covered with the dielectric film 111 and the dielectric film 117, which function as a part of the multilayer reflector, so that the reflectance can be increased.

(Fourth embodiment)
Next, a fourth embodiment will be described. The fourth embodiment relates to a light source device and a detection device having the surface emitting laser device according to any one of the first to third embodiments. FIG. 10 shows an outline of a distance measuring device 10 as an example of a detection device.

The distance measuring device 10 includes a light source device 11 as an example of a light source device. The distance measuring device 10 projects (irradiates) pulsed light from the light source device 11 onto the detection target 12, receives the reflected light from the detection target 12 with the light receiving element 13, and receives the reflected light. It is a TOF (Time Of Flight) distance detection device that measures the distance to the detection target 12 based on the time required.

As shown in FIG. 10, the light source device 11 has a light source 14 and an optical system 15 . The light source 14 includes a surface-emitting laser element according to any one of the first to third embodiments, and is controlled by a light source drive circuit 16 that supplies current to the light source 14 . The light source drive circuit 16 transmits a signal to the signal control circuit 17 when the light source 14 is caused to emit light. The optical system 15 has an optical element (for example, a lens, a DOE, a prism, etc.) that adjusts the divergence angle and direction of the light emitted from the light source 14, and irradiates the detection object 12 with the light.

Reflected light projected from the light source device 11 and reflected by the detection object 12 is guided to the light receiving element 13 through the light receiving optical system 18 having a light collecting action. The light receiving element 13 includes a photoelectric conversion element, and the light received by the light receiving element 13 is photoelectrically converted and sent to the signal control circuit 17 as an electric signal. The signal control circuit 17 calculates the distance to the detection object 12 based on the time difference between light projection (light emission signal input from the light source drive circuit 16) and light reception (light reception signal input from the light receiving element 13). Therefore, in the distance measuring device 10, the light receiving optical system 18 and the light receiving element 13 function as a detection system into which the light emitted from the light source device 11 and reflected by the detection object 12 is incident. Further, the signal control circuit 17 may be configured to acquire information regarding the presence or absence of the detection target 12 and the relative speed with respect to the detection target 12 based on the signal from the light receiving element 13 .

In this embodiment, since a surface emitting laser element that emits light with a single transverse mode and high output is used, it is possible to perform detection and measurement with higher accuracy.

Although the preferred embodiments and the like have been described in detail above, the present invention is not limited to the above-described embodiments and the like, and various modifications can be made to the above-described embodiments and the like without departing from the scope of the claims. Modifications and substitutions can be made.

REFERENCE SIGNS LIST 10 distance measuring device 11 light source device 13 light receiving element 15 optical system 18 light receiving optical system 100, 200, 300 surface emitting laser element 111, 111A, 111B, 116, 117 dielectric film 112 emission region 112C center portion 112P peripheral portion 115 adjustment film 120 laser structure 120A emission surface

JP 2011-181786 A

Claims (8)

a laser structure that emits light having an oscillation wavelength of λ from an emission surface;
a film provided in the output region of the output surface, the film making a second reflectance lower in a peripheral portion around the central portion than in a first reflectance in the central portion of the output region;
has
the second reflectance is 0.984 times or more and 0.998 times or less of the first reflectance;
the optical thickness of the film at the periphery is set at an odd multiple of λ/4 and is λ/4±αλ;
A surface emitting laser device, wherein α is 0.05 or more and 0.18 or less . 2. The surface emitting laser element according to claim 1, wherein said second reflectance is 98% or more. the laser structure having an oxidized constriction structure comprising an unoxidized region and an oxidized region surrounding the unoxidized region;
3. The surface emitting laser device according to claim 1, wherein the area of said central portion is 85% or less of the area of said non-oxidized region. 4. The surface emitting laser element according to claim 1 , wherein said film has a first film provided in said peripheral portion. 5. The surface emitting laser element according to claim 4 , wherein said film has a second film provided on said central portion and said peripheral portion. The first film is also provided in the central portion,
5. The surface emitting laser element according to claim 4 , wherein said film has a third film provided in said central portion. a surface-emitting laser device according to any one of claims 1 to 6 ;
an optical system into which emitted light emitted from the surface emitting laser element is incident;
A light source device comprising: a surface-emitting laser device according to any one of claims 1 to 6 ;
a detection system in which emitted light emitted from the surface emitting laser element is reflected by a target portion and the reflected light is incident;
A detection device comprising:

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