JPH0918084A - Surface light emitting semiconductor laser and manufacture thereof - Google Patents

Abstract

PURPOSE: To enable an energy peak space in a far field pattern to be optionally changed corresponding to a space between two luminous spots in a near field pattern. CONSTITUTION: A first and a second reflecting mirror, 103 and 111, and an optical resonator composed of semiconductor layers 104, 105, 106, and 109 provided between the mirrors 103 and 111 are provided onto a semiconductor substrate 102. The second clad layer 106 and the contact layer 109 out of the layers are formed into columnar parts 114a and 114b. A phase shifter layer 115 formed of material different from air in refractive index is provided to a region on the surface of the second reflecting mirror 111 confronting the columnar part 114b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting semiconductor laser having a plurality of light emitting spots, and more particularly to a surface emitting semiconductor laser capable of emitting a laser beam most suitable for forming a small beam spot by utilizing super resolution. Type semiconductor laser.

[0002]

2. Description of the Related Art In semiconductor laser application equipment such as an optical reading device and an optical measuring device, it is desired to image a laser beam having a small beam spot on a projection surface. Japanese Patent Laid-Open No. 12622/1990 discloses a technique of forming a laser beam having a small beam spot on a projection surface by utilizing super-resolution. The principle of this super-resolution will be described with reference to FIGS. 9 and 10.

In FIG. 9, from the semiconductor laser 10,
Laser light with a predetermined emission angle is emitted from a single emission spot, and this laser light passes through an aperture 12 having a circular hole, so that only laser light within a predetermined emission angle range with high energy intensity is extracted. Be done. Thereafter, this laser light is converted into parallel light 1 through the first lens 14 and
The lens 18 forms an image on the inclined surface 20.

Here, a light shield 16 is arranged on the optical axis between the first and second lenses 14 and 18. The parallel light 1 before passing through the light shield 16 has a cross section AA in FIG.
As shown in FIG. 10A, the laser light has a circular cross section. When the parallel light 1 passes through the light shield 16, the BB line in FIG.
As shown in FIG. 10B, which is a sectional view, the parallel light 1 is divided into two by the light shield 16.

The above-mentioned super-resolution is a phase-synchronized laser beam, and a laser beam with a small beam spot is imaged on the projection surface 20 due to the interference effect of two laser beams that are close to each other. Say that.

Here, the energy intensity of the parallel light after passing through the light shield 16 has two energy peaks as shown in FIG. 10C showing the beam intensity distribution in the CC cross section of FIG. It is divided into light. On the other hand, the laser light imaged on the projection surface 20 is shown in FIG.
Has an energy peak in the center, and
It is a laser beam with a small beam spot.

However, as described above, when the laser light from a single light emission spot is divided into two using the light shield 16, as shown in FIG. 10C, the energy intensity is the highest. It can be seen that the light in the central area is blocked and the light utilization rate decreases. Japanese Unexamined Patent Publication No. 2-162222
As disclosed in the publication, in order to enhance the super-resolution effect, the light-shielding width of the light-shielding body 16 must be widened, and the light utilization rate further decreases accordingly.

In JP-A-2-12622, it is pointed out that the reduction of the light utilization rate is a conventional problem. Then, instead of the light shield 16 shown in FIG. 9, a beam splitter is arranged and a central region of high energy intensity is provided. The invention of splitting into two laser beams while utilizing light is disclosed.

However, in this technique, in addition to the fact that a beam splitter is indispensable, an interval (preferably 2) between two laser beams divided for enhancing the effect of super-resolution is provided.
(3 cm) is essential, and there is an inherent problem that the structure of the optical system becomes complicated.

On the other hand, the applicant of the present application has filed Japanese Patent Laid-Open No. 4-3630.
As disclosed in Japanese Patent No. 81, there is disclosed a technique in which at least a cladding layer of an optical resonator is formed as a plurality of columnar portions and a plurality of phase-synchronized laser beams are emitted from the end faces of the respective columnar portions. .

FIG. 11 is a beam intensity distribution in a far-field pattern (far field pattern, hereinafter also referred to as FFP) of laser light emitted from a plurality of light emission spots 22 and 24 of a semiconductor laser disclosed in Japanese Patent Laid-Open No. 4-363081. Is shown. As shown in FIG. 11, a beam 26 having a relatively large diameter having an energy peak at a radiation angle of 0 degree is obtained due to the interference effect between the two laser beams having the same phase.
As it is, it cannot be applied to an optical reader or the like that requires a small-diameter beam. It should be noted that in the FFP, the sub-peak 28 occurs in the range of the predetermined radiation angle.

Further, according to this technique, the distance between the light emission spots 22 and 24 on the light emitting surface of one surface-emitting type semiconductor laser (center-to-center distance between columnar portions) is 20 μm or less because of phase synchronization. Must be set. Therefore, even when the surface emitting semiconductor laser is used to form light with a small beam spot utilizing the above-mentioned super-resolution effect, a near-field image (near field pattern, hereinafter referred to as NF) is formed.
The distance between the two energy peaks in (also referred to as P) is
There is a problem that the optical system must be expanded by using the optical system, and the optical system is similarly complicated.

Therefore, an object of the present invention is to reduce the light utilization rate of the laser light emitted from a plurality of light emission spots, and without complicating the optical system.
An object of the present invention is to provide a surface-emitting type semiconductor laser capable of arbitrarily changing the energy peak interval in a far-field image with respect to the interval between two emission spots in a near-field image, and a method for manufacturing the same.

Another object of the present invention is to provide a surface-emitting type device capable of controlling the position of interference of laser light by arbitrarily setting the positions of a plurality of light emission spots and the phase of laser light emitted therefrom. A semiconductor laser and a method for manufacturing the same are provided.

[0015]

According to a first aspect of the present invention, there is provided an optical resonator including a pair of first and second reflecting mirrors and a plurality of semiconductor layers between them, and a direction perpendicular to the semiconductor substrate. Via the second reflecting mirror on the light emitting side,
In a surface emitting semiconductor laser that oscillates laser light from a plurality of light emission spots, a phase formed of a material having a refractive index different from that of air in a partial region facing at least one light emission spot on the second reflection mirror. A shifter layer is provided.

FIG. 5 shows the principle of arbitrarily controlling the positions of interference of laser beams from a plurality of emission spots, in other words, the intervals of a plurality of beam spots in the far-field pattern of the laser beams in the invention of claim 1. It will be described with reference to FIG.

In the figure, from, for example, two emission spots 30 and 32 on the emission surface of the surface emitting semiconductor laser,
Laser beams having different phases are emitted. For example, if a phase shift layer is arranged on the second electrode on the light emission side at a position facing the light emission spot 32, the phase of the laser light from the light emission spot 30 with respect to the phase of the laser light from the light emission spot 32 is emitted. The phase of the laser light can be phase-shifted by (-λ / 2), for example.

The phase of the laser beam 30a that apparently goes straight in FIG. 5 from the light emission spot 30 is compared with the phase of the laser beam 30a that apparently goes straight in FIG.
The phase of a is shifted by (−λ / 2). On the other hand, the laser beam 30b emitted from the light emission spot 30 in an apparently obliquely upward direction in FIG. 5 has a different optical path length from the laser beam 30a, and thus has the same phase difference (−λ / 2) as the laser beam 32a. ) Has occurred. The two laser beams 30b and 32a deviated by the same phase difference interfere with each other and have an energy peak at the position of the radiation angle + θ from the center in the far field image.

Further, the laser beam 32b, which is apparently directed obliquely upward in FIG. 5 from the light emission spot 32, has a phase difference of −λ / 2−λ / 2 = 0 with respect to the laser beam 30a. There is no phase difference between 30a and 32b and they interfere with each other, and as a result, there is an energy peak at the radiation angle -θ in the far field image. That is, the radiation angle having the energy peak can be changed by the phase difference of the laser light.

Letting L be the distance from the emission spots 30 and 32 to the far-field image, the distance W between the two beams which has an energy peak at the radiation angle (± θ) in the far-field image is W = 2L × tan θ. … (1)

Further, the distance between the light emitting spots 30 and 32 is P, and the laser beam 30a from the light emitting spot 30 is used.
, And the phase difference between the laser beams 30a and 32a from the respective emission spots 30 and 32 is α, in order to reach the energy peak at the emission angle (± θ), [(L · tan θ + P / 2) ² + L ² ] ^1/2 = [(L · tan θ−P / 2) ² + L ² ] ^1/2 + α + m · λ (2) is satisfied.

Here, the coefficient m is defined by the respective emission spots 30,
It means that the difference in optical path length from 32 to the position of the radiation angle (± θ) in the far-field image is an integer multiple of the wavelength λ in addition to the phase difference α, and m = 0, ± 1, ± Although it can take values such as 2, FIG. 5 shows a case where m = ± 1. m = ± 2, ±
When a large absolute value such as 3 is adopted, the energy peak in the far-field image becomes small.

As is apparent from the equations (1) and (2), by arbitrarily setting the light emission spot interval P and the phase difference α, the position or direction where the laser light interferes, in other words, the beam in the far field image. It is possible to change the interval W arbitrarily.

By the way, the two energy peaks in the far-field pattern have a phase difference (-λ /
Although it is shifted by 2), when forming by super-resolution, by adjusting the phase of the laser light having one of the energy peaks in the middle of the optical path, two laser lights of the same phase are This can be obtained, and effective super-resolution imaging can be realized by the interference effect of the two laser beams.

Here, a desired phase difference may be provided between the two laser beams guided in the resonator in the surface-emitting type semiconductor laser, but it is extremely difficult to manufacture such an optical resonator. Have difficulty. On the other hand, according to the invention of claim 1, the phase shifter layer is locally provided on the second reflection mirror on the light emitting side, so that the phases of the laser light guided in the resonator are aligned. It is possible to give an arbitrary phase difference by interposing the phase shifter layer in the above state. Further, since the light emitting portion is on the same plane on the semiconductor laser, the adjustment of the optical system becomes easy.

The invention of claim 2 is in common with the invention of claim 1 in that a phase shifter layer is locally provided on the second reflecting mirror. In the invention of claim 2, among the multi-layered semiconductor layers formed between the pair of first and second reflection mirrors, at least the cladding layer is etched into a plurality of pillars to form a plurality of pillars. doing. Further, an insulating burying layer is buried around the plurality of columnar portions.

According to this semiconductor laser, the laser light is emitted from each of the end faces of the plurality of columnar portions,
It can have a plurality of emission spots. Since the plurality of columnar portions of the optical resonator are embedded by the insulating burying layer, the current injected into the optical resonator and the light generated thereby are prevented from diffusing to the outside. Laser light can be emitted with high efficiency, and the threshold current can be reduced.

In the third aspect of the present invention, the second reflecting mirror is composed of a dielectric mirror formed by alternately forming a plurality of layers of the first layer and the second layer. In this case, by forming the phase shifter layer with a single film layer made of the same material as the first layer or the second layer, the second reflection mirror and the phase shifter layer are continuously formed in the same chamber. Can be formed.

According to the invention of claim 4, the absorption coefficient of the phase shifter layer with respect to the wavelength of the laser light is set to 100 cm ^-1 or less. With this, it is possible to reduce a decrease in only the energy peak of the laser light on the side emitted through the phase shifter layer.

Claims 5 and 6 respectively define a laser manufacturing method according to each of the inventions of claims 1 and 2.

According to each of these inventions, the pair of first and second pairs
After forming the reflection mirror and the multi-layered semiconductor layer formed therebetween, the phase shifter layer is locally formed on the second reflection mirror. As a result, by changing the material and film thickness of the phase shifter layer without changing the manufacturing process of the optical resonator, an arbitrary phase difference can be set for the laser beams emitted from the plurality of light emission spots. Is possible.

The invention of claim 7 defines a manufacturing process suitable for the structure defined in claim 3. According to the present invention, a single film layer made of the same material as any one of the first layer and the second layer forming the dielectric mirror as the second reflection mirror is formed, and then the single film layer is formed. By locally etching this single film layer, the phase shifter layer can be locally formed on the second reflecting mirror.

In the invention of claim 8, in the film forming step,
The single film layer is formed to a thickness equal to or larger than a design value for obtaining a predetermined phase shifter amount, and then, in the subsequent removing step, the single film layer is entirely etched before the local etching. Thus, the film thickness can be set to the above design value.

According to the ninth aspect of the invention, in performing the removing step of the seventh or eighth aspect, the single film layer is irradiated with light having a predetermined wavelength at the time of etching to detect the reflection spectrum thereof. Then, by measuring the reflectance profile, the etching amount of the single film layer can be accurately controlled.

[0035]

An embodiment of the present invention will be described below with reference to the drawings.

(Laser Structure) FIG. 1 is a perspective view schematically showing a cross section of a light emitting portion of a surface emitting semiconductor laser device according to an embodiment of the present invention.

The semiconductor laser device 100 shown in FIG.
An n-type Al _0.8 Ga _0.2 As layer and an n-type Al _0.15 Ga _0.85 As layer are alternately laminated on the n-type GaAs substrate 102 to _obtain a wavelength of 8
40 pairs of distributed reflection multilayer mirrors (hereinafter referred to as "DB") having a reflectance of 99.5% or more for light near 00 nm.
(Also referred to as "R mirror") 103, n-type Al _0.7 Ga _0.3
First cladding layer 104 made of As layer, n ^- type GaAs
Quantum well active layer 105 comprising a well layer and an n ^- type Al _0.3 Ga _0.7 As barrier layer, the well layer comprising 21 layers
(In the case of the present embodiment, it is an active layer of a multi-quantum well structure (MQW)), a second cladding layer 106 made of a p-type Al _0.7 Ga _0.3 As layer and a p ⁺ -type Al _0.15 Ga _0.85.
A contact layer 109 made of an As layer is sequentially laminated. Then, a part of the second cladding layer 106 is etched into a circular shape as viewed from the top surface of the semiconductor laminate,
A plurality of, for example, two first and second columnar portions 114a, 1
14b is formed. The first and second columnar portions 114
If the cross sections of a and 114b parallel to the substrate 102 are both rectangular with long sides and short sides, the direction of the polarization plane of the laser light emitted from the oscillation region of each columnar portion is aligned with the short side direction. You can

The first and second columnar portions 114a, 11
The separation groove 110 is formed between 4b by the above-described etching. In the region including the separation groove 110, the peripheral regions of the first and second columnar portions 114a and 114b are
A first insulating layer 107 made of a silicon oxide film (SiO _x film) such as SiO ₂ formed by a thermal CVD method and a second insulating layer 108 made of a heat resistant resin such as polyimide are embedded.

The first insulating layer 107 is the second cladding layer 10
6 and the contact layer 109, the second insulating layer 108 is continuously formed along the surface of the contact layer 109 and the first insulating layer 107.

As the second insulating layer 108, in addition to the above-mentioned heat-resistant resin such as polyimide, a silicon oxide film (SiO _x film) such as SiO ₂ or a silicon nitride film (Si such as Si ₃ N ₄ ) is used.
N _X film), silicon carbide film such as SiC (SiC _X film), S
OG (SiO _x such as SiO ₂ by spin-on-glass method)
Insulating silicon compound film such as film, or polycrystalline I
It may be a group I-VI compound semiconductor film (for example, ZnSe). Among these insulating films, a silicon oxide film such as SiO ₂ which can be formed at a low temperature, polyimide or SOG
It is preferable to use a membrane. Furthermore, it is preferable to use the SOG film because it is easy to form and the surface becomes flat easily.

Here, the silicon oxide film (SiO _x
The first insulating layer 107 made of a film has a film thickness of 500 to 2000 angstroms and is formed by a thermal CVD method under normal pressure. The second insulating layer 108 made of a heat resistant resin or the like is necessary for flattening the surface of the element. For example, a heat-resistant resin has a high resistance, but moisture is likely to remain in the film, and if it is brought into direct contact with the semiconductor layer, voids may form at the interface with the semiconductor when the device is energized for a long time. Occurs and deteriorates the characteristics of the element. Therefore, when a thin film such as the first insulating layer 107 is inserted at the boundary with the semiconductor layer as in this embodiment, the first insulating layer 107 serves as a protective film and the above-mentioned deterioration does not occur. For forming the silicon oxide film (SiO _x film) forming the first insulating layer, plasma CV is used.
Although there are various methods such as D method and reactive vapor deposition method, a film formation method by atmospheric pressure thermal CVD method using SiH ₄ (monosilane) gas and O ₂ (oxygen) gas and N ₂ (nitrogen) gas as a carrier gas is available. Most suitable. The reason is that the reaction is carried out at atmospheric pressure,
Further, since the film is formed under the condition that the amount of O ₂ is excessive, the SiO _x film has a small oxygen deficiency and becomes a dense film, and the step coverage is good, and the side surfaces and the stepped portions of the columnar portions 114a and 114b are flat. That is, the same film thickness as the part can be obtained.

The buried layer is not limited to the first and second insulating layers 107 and 108, and the buried layer may be formed of, for example, a II-VI group compound semiconductor epitaxial layer.

Further, it is composed of, for example, Cr and an Au--Zn alloy.
The contact metal layer (upper electrode) 112 is
Current contact layer 109 is formed in contact with
Will be the electrode for. The upper electrode of this contact layer 109
The part not covered by the pole 112 is exposed in a circular shape.
You. Then, the exposed surface of the contact layer 109 (hereinafter,
This area is referred to as "opening 113")
Then, the first layer such as SiO _TwoSiO such as_xLayer and second layer
If Ta_TwoO_FiveLayers are laminated alternately, and the wavelength around 800 nm
7 pairs of light with a reflectance of 98.5-99.5%
A dielectric multilayer film mirror 111 is formed. These first
The thickness of each of the 1st and 2nd layers is guided inside the optical resonator.
Refraction of wavelength λ in each layer
When the rate is n, it is set to λ / 4n. Also,
Under the n-type GaAs substrate 102, for example, Ni and Au-
The metal layer for electrodes (lower electrode) 101 made of Ge alloy is formed
Has been established.

A characteristic structure of the semiconductor laser of this embodiment is that the phase shifter layer 115 is locally formed on the upper surface of the upper dielectric multilayer mirror 111. In the present embodiment, the phase shifter layer 115 is the second columnar portion 1
It is provided only at a position facing the end face of 14b. When the phase shifter layer 115 is formed of the same material as either the first layer or the second layer constituting the dielectric multilayer film mirror 111 formed below, the phase shifter layer 115 will be described later. 111 and the phase shifter layer 115 can be formed in the same chamber.

Here, when the oscillation wavelength is λ, the refractive index of air is n ₁ and the refractive index of the phase shifter layer 115 is n ₂ , it is necessary for the phase shifter layer 115 to shift by the phase difference α. The thickness d of the phase shifter layer 115 satisfies the following formula.

N ₁ × d−n ₂ × d = α Therefore, when setting the phase difference of (−λ / 2) in the phase shifter layer 115 as in the present embodiment, 2n ₁ × d + λ. = 2n ₂ × d.

Since the refractive index of air n ₁ = 1, n ₂ = 1
When the phase shifter layer 115 of No. 1 is used, its thickness d = λ / 2
If n ₂ = 3, then d = λ / 4.

Further, the phase shifter layer 115 preferably has an absorption coefficient with respect to the wavelength of the laser light of 100 cm ⁻¹ or less, and by doing so, the energy absorbed in the phase shifter layer 115 can be almost ignored.

(Laser Oscillation Operation in Optical Resonator) A forward voltage is applied between the upper electrode 112 and the lower electrode 101 (in the case of the present embodiment, from the upper electrode 112 to the lower electrode 1).
Current is applied (voltage is applied in the direction of 01). The injected current is converted into light in the quantum well active layer 105, and the DBR mirror 103 and the dielectric multilayer film mirror 11 are converted.
The light is amplified as it reciprocates between the reflecting mirrors composed of 1 and 1. Moreover, the current injected into the optical resonator and the generated and amplified light are first and second embedded in the periphery of the first and second columnar portions 114a and 114b.
It is confined by the insulating layers 107 and 108, and the laser oscillation operation can be efficiently performed.

Then, the opening 113 (contact layer 10
9 exposed surface) and the dielectric multilayer mirror 111,
Laser light is emitted in a direction perpendicular to the substrate 102.

Here, the first and second columnar portions 114a,
Two laser beams emitted from 114b via the dielectric multilayer mirror 111 have the same phase. The reason for this is that, firstly, the active layer 105 is
This is because they are continuous in the lateral direction below the columnar portions 114a and 114b and are influenced by light in each oscillation region. Secondly, the center-to-center distance P (see FIG. 1) of each columnar portion 114a, 114b is arranged close to, for example, 3 to 20 μm, and the light generated in each columnar portion 114a, 114b affects each other and The phases are synchronized.

Therefore, a near-field image (NF) of the laser light emitted from the two light emission spots of the semiconductor laser 100 is obtained.
The interval between the light emission spots in P) is almost the same as the center-to-center distance P described above, and is a distance as close as 3 to 20 μm. The polarization planes of the laser light emitted from the two emission spots are also aligned with the short sides of the rectangular cross sections of the columnar portions 114a and 114b. The direction of the plane of polarization of the laser light can be aligned in the direction of its short side even if the cross section of the columnar portion is not circular but is circular, for example, if the opening 113 of the upper electrode 112 is rectangular.

In this embodiment, since the laser beam having a small beam spot diameter is formed on the projection surface by utilizing the effective super-resolution, a far field image (FFP) is used without using a complicated optical system. In order to arbitrarily set the beam spot interval of, the phase shifter layer 115 is locally provided on the upper surface of the dielectric multilayer mirror 111. Hereinafter, the principle of expanding the beam spot interval in FFP will be described with reference to FIG.

(Regarding the light emission spot interval in FFP)
The two emission spots 30 and 32 shown in FIG.
Two emission spots on the same virtual emission surface as the surface of the phase shifter layer 115 shown in FIG. 1 are shown. Therefore, the distance between the two emission spots 30 and 32 is such that the center-to-center distance P of the first and second columnar portions 114a and 114b is P = 3 to 20.
μm.

As described above, the laser light 30a from the first light emission spot 30 and the second light emission spot 32 are used.
And the laser beam 32b from
Due to these interference effects, a beam spot having an energy peak at the emission angle (-θ) can be obtained as an FFP at a position separated by a distance L from the virtual light emitting surface.

Similarly, the laser light 32a from the second light emission spot 32 and the laser light 30b from the first light emission spot 30 have a phase difference (-λ /) with respect to the laser light 30a and 32b. 2) has occurred, and due to the interference effect of the laser beams 30b and 32a having the same phase difference, F
Laser light having an energy peak at the emission angle (+ θ) can be obtained as FP.

In FIG. 5, the horizontal axis of NFP shows the distance between the light emission spots, while the horizontal axis of FFP shows the emission angle. As described above, the distance W between the two energy peaks in the FFP depends on the phase difference of the laser light emitted from the semiconductor laser 100 and the distance P between the light emission spots, and these two parameters are set arbitrarily. By doing so, the beam spot interval W on the FFP can be arbitrarily changed.

In order to realize super resolution, the larger the distance W is, the more effective it is. However, when the semiconductor laser 100 is used to construct an optical reading apparatus utilizing super resolution,
Considering the practical size of the optical system, the distance W may be set to, for example, 2 to 3 cm. (Imaging Operation Using Super-Resolution) Next, the semiconductor laser 100 is applied to, for example, an optical reading device, and an optical system is used to emit laser light having a small beam spot diameter by utilizing super-resolution. The operation for forming an image on the upper surface will be described with reference to FIGS. 6 and 7.

FIG. 6 schematically shows an optical system arranged between the semiconductor laser 100 and the projection surface 120 of this embodiment. First and second lenses 122 and 124 are arranged on the optical axis connecting the semiconductor laser 100 and the projection surface 120. Further, a phase adjusting plate 126 is arranged between the two lenses 122 and 124.

The first lens 122 is used for the semiconductor laser 10
The lens is arranged at a position separated by a distance L from 0, and is a lens for converting laser light emitted from the semiconductor laser 100 into parallel light. In addition, the upper broken line shown in FIG.
Shows the optical path of the laser light having an energy peak at the radiation angle (-θ) on the FFP at the position where the lens 122 is arranged. Similarly, the lower broken line in FIG. 6 indicates the optical path of laser light having an energy peak at the emission angle (+ θ).

A- at the position of the first lens 122 in FIG.
The intensity distribution of the laser light in the A section is shown in FIG. As shown in the figure, the light intensity distribution has an energy peak at each radiation angle (± θ). However, the laser beam at the emission angle (+ θ) is
There is a phase difference (−λ / 2) with respect to the laser light at θ).

The phase adjusting plate 126 has a phase of laser light having an energy peak at a radiation angle (+ θ) and a radiation angle (−).
This is for matching the phase of the laser light having an energy peak in (θ), and in this embodiment, (−λ / 2)
Only the phase is shifted. As a result, BB of FIG.
As shown in FIG. 7B, which is a cross section, the phases of laser light having energy peaks are matched with the emission angle (± θ).

As described above, the two laser beams having the same phase and the energy peak interval set to, for example, 2 to 3 cm interfere with each other and pass through the second lens 124, and then on the projection surface 120. The beam spot imaged on can be made smaller in diameter due to the principle of super-resolution.

As described above, according to the present embodiment, since it is not necessary to divide a single laser beam by using a light shield or a beam splitter as in the conventional case, the laser beam is emitted from the semiconductor laser 100. A super-resolution can be obtained on the projection surface 120 without lowering the light utilization rate of the generated laser light and without complicating the optical system.

The phase adjusting plate 126 is not necessarily provided in the middle of the optical path of the laser light having the energy peak at the emission angle (+ θ), but in the middle of the optical path of the laser light having the energy peak at the emission angle (−θ). Can also be provided. In other words, the phase adjusting plate 126 can be provided in the optical path of the laser light on the side that does not pass through the phase shifter layer 115. In this way, if the light energies absorbed by the phase shifter layer 115 and the phase adjusting plate 126 are set to be substantially the same, the energy intensity at the emission angle (± θ) can be maintained substantially the same. If the absorption coefficient of the phase shifter layer 115 and the phase adjusting plate 126 are both 100 cm ⁻¹ or less for the wavelength of the laser light, the energy absorbed by them can be ignored.

(Manufacturing Process) Next, a manufacturing process of the surface-emitting type semiconductor laser 100 shown in FIG. 1 will be described. 2A to 2C, 3A to 3C, and 4
(A) and (B) show the manufacturing process of the surface emitting semiconductor laser device.

On the n-type GaAs substrate 102, n-type Al _0.15
A Ga _0.85 As layer and an n-type Al _0.8 Ga _0.2 As layer are alternately laminated to form 40 pairs of DBR mirrors 103 having a reflectance of 99.5% or more for light near a wavelength of 800 nm as a lower mirror. Furthermore, n-type Al _0.7 Ga _0.3 As
After forming the layer (first clad layer) 104, n ⁻ type Ga
Active layer 105 having a quantum well structure (MQW) in which As well layers and n ⁻ -type Al _0.3 Ga _0.7 As barrier layers are alternately laminated.
To form Then, a p-type Al _0.7 Ga _0.3 As layer (second
Clad layer) 106, and p-type Al _0.15 Ga _0.85 As
Layers (contact layers) 109 are sequentially stacked (FIG. 2A).
reference).

Each of the above layers is formed by metalorganic vapor phase epitaxy (MOV).
PE: Metal-Organic Vapor Pha
It was epitaxially grown by the se epitaxy method. At this time, for example, the growth temperature is 750 ° C., the growth pressure is 150 Torr, the organic metal of TMGa (trimethylzinc) and TMAl (trimethylaluminum) is used as the group III source, AsH ₃ is used as the group V source, and H is used as the n-type dopant.
₂ Se , P-type dopant as DEZn (diethyl zinc)
Was used.

After the formation of each layer, the S layer of about 250 angstrom is formed on the epitaxial layer by using the atmospheric pressure thermal CVD method.
A protective layer I composed of an iO ₂ layer is formed. By covering the semiconductor layer on which the protective layer I is laminated, surface contamination during the process is prevented.

Next, reactive ion beam etching (R
The columnar portions 114a and 114b covered with the resist pattern R1 are left by the IBE) method, and the separation groove 1 is provided between them.
While forming 10, the second clad layer 106 is partially etched. By performing this etching process, the columnar portions 114a and 114b have the same cross section as the contour shape of the resist pattern R1 thereon (FIG. 2B).
reference). Further, since the RIBE method is used, the side surfaces of the columnar portions 114a and 114b are substantially vertical, and there is almost no damage to the epitaxial layer. The RIBE conditions were, for example, a pressure of 60 mPa, an input microwave power of 150 W, an extraction voltage of 350 V, and a mixed gas of chlorine and argon was used as an etching gas.

After that, the resist pattern R1 is removed, and a SiO ₂ layer (first insulating film) 107 of about 1000 Å is formed on the surface by atmospheric pressure thermal CVD.
The process conditions at this time are, for example, a substrate temperature of 45.
SiH ₄ (monosilane) and oxygen were used as raw materials at 0 ° C., and nitrogen was used as a carrier gas. Furthermore, SOG (Spin on Gra
ss) film 108L, and then, for example, at 80 ° C. for 1
Minutes, 150 ° C for 2 minutes, 300 ° C for 30 minutes,
Baking in nitrogen (see FIG. 2C).

Next, the SOG film 108L and the SiO ₂ film 10
7 was etched back and flattened so as to be flush with the exposed surface of the contact layer 109 (see FIG. 3A). A reactive ion etching (RIE) method using a parallel plate electrode is adopted for etching, and as a reaction gas,
SF ₆ , CHF ₃ and Ar were used in combination.

Next, the upper electrode 112, which contacts the contact layer 109 in a ring shape, was formed by a known lift-off method (see FIG. 3B). The contact layer 109 is exposed through the circular opening of the upper electrode 112, and a dielectric multilayer mirror (upper mirror) is provided so as to sufficiently cover this exposed surface.
111 is formed by a known lift-off method (FIG. 3).
(C)). The upper mirror 111 is formed by alternately stacking, for example, 7 pairs of SiO ₂ layers and Ta ₂ O ₅ layers by using an electron beam evaporation method, and is 98.5 to 99.5% for light near a wavelength of 800 nm. Has a reflectance of. The vapor deposition speed at this time is, for example, 5 angstrom / min for SiO ₂ .
The Ta ₂ O ₅ layer was 2 Å / min.

The phase shifter layer 115 shown in FIG. 1 is locally formed on the upper mirror 111. In order to form the phase shifter layer 115, as shown in FIG. 4A, a single film layer 116 made of a material having a refractive index different from that of air is formed on the entire surface of the upper mirror 111 with a predetermined thickness. .

Single film layer 116 to be the phase shifter layer 115
It is preferable that the upper mirror 111 is formed of the same layer as either the first layer (for example, SiO ₂ ) or the second layer (Ta ₂ O ₅ ) constituting the upper mirror 111. This is because the single film layer 116 can be formed in the same chamber subsequent to the upper mirror 111 by the electron beam evaporation method. As the film thickness of this single film layer 116, in order to obtain a film thickness as designed so that the phase of the laser light can be shifted by, for example, (−λ / 2), the film thickness is formed during the film forming process. You can also do it. Others, single film layer 116
Can be formed to a thickness equal to or larger than the designed value, and the etching amount can be controlled during the entire surface etching to set the designed value.

Next, as shown in FIG. 4B, a resist film 117 formed by a photolithography process is used to leave only a single film layer 116 in a region facing one columnar portion 114b and leave the other. Regions are locally etched. Prior to this, it is also possible to perform the entire surface etching to set the film thickness to the above-mentioned design value. This single film layer 11
As the etching method of 6, the RIE method or the RIBE is used.
Method can be used.

Then, Ni and A are formed on the lower surface of the substrate 102.
The lower electrode 101 made of a uGe alloy is formed to complete the surface emitting semiconductor laser device.

Here, the single film layer 116 is applied to the upper mirror 11.
When the first layer constituting No. 1 is formed of, for example, SiO _2, it is important to control the etching amount of the SiO ₂ layer in both the above local etching and the entire surface etching. Accordingly, the RIE apparatus used in the etching of the SiO ₂ layers in this embodiment, to introduce a method that can measure the reflectance of the SiO ₂ layer during etching, it was decided to measure the amount of etching.

FIG. 8 shows a schematic diagram of a parallel plate type RIE apparatus incorporating a reflectance measuring means. In this RIE apparatus, an electrode 162 connected to an RF oscillator 161 and a mesh-shaped counter electrode 164 are provided in the etching chamber 160 so as to face each other. A gas supply unit 170 and a vacuum pump 166 for exhaust are connected to the etching chamber 160. Then, the electrode 16 in the etching chamber 160
An observation window 168 is provided on the wall surface facing 2 and a light source 172 and a photodetector 174 are installed outside the observation window 168. Then, the light emitted from the light source 172 reaches the substrate S through the observation window 168, and the reflected light reaches the photodetector 174 through the observation window 168. In this RIE apparatus, the SiO ₂ layer is etched by a normal mechanism and the light source 17
The reflectance of the etching surface can be monitored by detecting the light from the light source 2.

The reflectivity changes depending on the remaining film thickness of the SiO ₂ layer. With respect to the wavelength λ of the measurement light source 172, the reflectance takes a maximum value and a minimum value each time the remaining film thickness becomes (λ / 4n).
When the O ₂ layer is completely etched, there is no change in reflectance. Here, n is the refractive index of the SiO ₂ layer. Therefore,
By measuring the reflectance during etching by RIE and monitoring the extreme value of the reflectance curve, the etching amount of the SiO ₂ layer can be controlled.

As described above, the phase shifter layer 115 can be accurately formed by using the etching whose reflectance is monitored.

The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the present invention.

In the above-mentioned embodiment, the two columnar portions are formed in the optical resonator, but the number is not limited to two and may be three or four. In this case, the phase shifter layer may be provided at a position facing one or more columnar portions. Also,
When one columnar portion is formed in the optical resonator, a plurality of openings may be formed in the second electrode on the light emitting side so as to face the region facing the end face of the one columnar portion. . As a result, even for surface emitting semiconductor lasers that obtain multiple emission spots,
The present invention can be applied. Furthermore, the optical resonator is not necessarily limited to one having a columnar portion, and the second resonator on the light emission side
The present invention can be applied to a surface emitting semiconductor laser in which a plurality of openings of the electrode are formed in a region facing the optical resonator to obtain a plurality of light emission spots.

[0084]

According to the surface emitting semiconductor lasers of the first to fifth aspects, the laser light guided inside the optical resonator is locally provided on the light emitting side while the phases thereof are matched. With the phase shifter layer, a phase difference can be provided, and the position or direction in which a plurality of laser lights interfere is controlled, and the energy peak interval in the far-field image is based on the phase difference of the laser light and the emission spot interval. It can be changed arbitrarily.
Therefore, the energy peak interval in the far-field image can be set arbitrarily, and a surface-emitting type semiconductor laser suitable for laser application equipment such as an optical reading device and an optical measuring device can be provided.

According to the method of manufacturing a surface-emitting type semiconductor laser described in claims 4 to 9, it is not always necessary to change the manufacturing process of the phase-locking type optical resonator in which the phases of the laser beams in a plurality of oscillation regions match each other. It is possible to arbitrarily change the energy peak interval in the far-field pattern, without being accompanied by it, and by arbitrarily setting the material and the film thickness of the phase shifter layer formed after the manufacture of this optical resonator. .

[0086]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a cross section of a surface-emitting type semiconductor laser according to an example of the present invention.

2A to 2C are cross-sectional views showing a manufacturing process of the surface-emitting type semiconductor laser shown in FIG.

3A to 3C are schematic cross-sectional views showing a manufacturing process performed subsequent to the process shown in FIG.

4A and 4B are schematic cross-sectional views showing a manufacturing process performed subsequent to the process of FIG.

FIG. 5 is a principle explanatory diagram for explaining that the energy peak interval in a far-field image widens.

6 is a schematic explanatory view showing an optical system of an optical reading device using the surface-emitting type semiconductor laser shown in FIG.

7A and 7B are cross-sectional views taken along line A- of FIG.
It is a characteristic view which shows the intensity distribution of the laser beam in A and BB.

8 is a cross-sectional view schematically showing an RIE device used in an etching process for forming a phase shifter layer of the surface-emitting type semiconductor laser shown in FIG.

FIG. 9 is a schematic explanatory diagram for explaining the principle of image formation using super-resolution.

10 (A) and (B) are respectively A- in FIG.
10A and 10B show beam shapes in A and BB cross sections, FIG. 9C shows a beam intensity distribution in a CC cross section of FIG. 9, and FIG. 9D is a diagram showing a beam intensity distribution on a radiation surface.

FIG. 11 is a distribution diagram of beam intensities in a far-field image of laser light from a plurality of light emission spots.

[Explanation of symbols]

 100 semiconductor laser 101 first electrode 102 semiconductor substrate 103 first reflection mirror 104, 105, 106, 109 multi-layered semiconductor layer 107, 108 buried layer 111 second reflection mirror 112 second electrode 113 opening 114a, 114b First and second columnar portions 115 Phase shifter layer

Claims (9)

[Claims] 1. A second reflection mirror on the light emitting side, which has an optical resonator composed of a pair of first and second reflection mirrors and a multi-layered semiconductor layer between the reflection mirrors, and which is oriented toward the direction perpendicular to the semiconductor substrate. In a surface-emitting type semiconductor laser that oscillates laser light from a plurality of light emission spots via, through a material having a refractive index different from that of air in a partial region facing at least one light emission spot on the second reflection mirror. A surface-emitting type semiconductor laser comprising the formed phase shifter layer. 2. A surface-emitting type semiconductor laser that oscillates a laser beam in a direction perpendicular to a semiconductor substrate, wherein a first electrode formed on the lower side of the semiconductor substrate and a first electrode formed on the semiconductor substrate. And a multi-layered semiconductor layer formed on the first reflection mirror and including at least an active layer and a clad layer, and at least the clad layer of the multi-layered semiconductor layer is etched into a plurality of pillars. A plurality of columnar portions, an insulating burying layer embedded around the plurality of columnar portions, and a second electrode having a light emitting hole formed at a position facing the plurality of columnar portions. A second reflecting mirror formed to cover the light emitting hole, and air on a part of the second reflecting mirror facing the at least one columnar portion. Material with different refractive index Surface-emitting type semiconductor laser and having a phase shifter layer formed Te. 3. The first reflection mirror according to claim 1, wherein the second reflection mirror is a dielectric mirror formed by alternately forming a plurality of first layers and a plurality of second layers, and the phase shifter layer includes the phase shifter layer. A surface-emitting type semiconductor laser, wherein a single film layer made of the same material as the first layer or the second layer is formed with a predetermined thickness. 4. The surface emitting semiconductor laser according to claim 1, wherein the phase shifter layer has an absorption coefficient of 100 cm ⁻¹ or less for a wavelength of laser light. 5. A second reflection mirror on the light emission side, which has an optical resonator composed of a pair of first and second reflection mirrors and a multi-layered semiconductor layer between them, and which faces the light emitting side in a direction perpendicular to the semiconductor substrate. A method of manufacturing a surface-emitting type semiconductor laser in which laser light is oscillated from a plurality of light emission spots via, through which at least one light emission spot on the second reflection mirror is opposed after forming the second reflection mirror. And a step of forming a phase shifter layer formed of a material having a refractive index different from that of air in a partial area of the surface emitting semiconductor laser. 6. A method of manufacturing a surface-emitting type semiconductor laser that oscillates laser light in a direction perpendicular to a semiconductor substrate, comprising the steps of forming a first electrode on the lower side of the semiconductor substrate, and forming a first electrode on the semiconductor substrate. Forming a reflection mirror of No. 1, a step of forming a multi-layer semiconductor layer including at least an active layer and a clad layer on the first reflection mirror, and at least the clad layer of the multi-layer semiconductor layer. To form a plurality of columnar parts by etching into a plurality of columnar parts, a step of forming an insulating burying layer around the plurality of columnar parts, and a step of facing the plurality of columnar parts. Forming a second electrode having a light emitting hole at a position, forming a second reflecting mirror covering the light emitting hole, and at least on the second reflecting mirror, and at least 1 of the above Some regions of Jo portion facing, surface-emitting type semiconductor laser manufacturing method characterized in that it comprises a step of forming a phase shifter layer of material that the air and the refractive index are different, the. 7. The method according to claim 5 or 6, wherein the step of forming the second reflecting mirror includes the steps of forming a first layer and a second layer.
A plurality of layers are alternately formed to form a dielectric mirror, and the step of forming the phase shifter layer includes forming a single film layer made of the same material as the first layer or the second layer. A film forming step of forming a film having a predetermined thickness on the second reflecting mirror, and leaving the single film layer only in the partial area on the second reflecting mirror, A method of manufacturing a surface-emitting type semiconductor laser, comprising: a step of locally etching and removing the single film layer. 8. The film forming step according to claim 7, wherein the single film layer is formed to have a film thickness equal to or larger than a film thickness on a design value for obtaining a predetermined phase shifter amount, and in the removing step, the local film is formed. A method for manufacturing a surface-emitting type semiconductor laser, comprising the step of etching the entire single film layer to set the film thickness on the design value before the etching. 9. The removing step according to claim 7, wherein the single film layer is irradiated with light having a predetermined wavelength during etching, the reflection spectrum of the single film layer is detected, and the reflectance profile is measured. A method of manufacturing a surface-emitting type semiconductor laser, comprising a step of controlling an etching amount of the single film layer.