JP2891133B2 - Surface emitting laser, surface emitting laser array, and optical information processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting laser and a surface emitting laser array used for optical communication and an optical computer, and more particularly to a surface emitting laser, a surface emitting laser array capable of arbitrarily controlling a polarization direction, and an optical information processing apparatus. Things.

[0002]

2. Description of the Related Art A high-density semiconductor laser array is required as a light source for optical communications and optical computers.
In a semiconductor laser array, several semiconductor lasers are arranged at an appropriate pitch, and each is independently driven.

[0003] As a main method of fabricating a semiconductor laser array conventionally used, semiconductor lasers fabricated separately are aligned and fused to the same heat sink using a low melting point alloy such as solder or AuSn. There is a method by flip chip bonding. In this case, since the alignment is performed by a mechanical method, there are disadvantages that the pitch cannot be reduced and the accuracy is poor.

[0004] On the other hand, there is a monolithic fabrication method in which a single substrate is fabricated. As shown in FIG. 22, the edge-emitting type stripe laser is manufactured by arranging mesa stripes at appropriate intervals. By dividing the electrodes individually, it is possible to move each laser separately. Further, in this type of semiconductor laser array, the pitch and position accuracy of the semiconductor lasers are determined by optical exposure, so that an accuracy of μm order can be obtained.

[0005] However, since the edge emitting type laser array can perform only one-dimensional array, there is a limit in the number and density of the array, and a semiconductor laser in which many semiconductor lasers required as a light source for optical information processing are integrated. Not suitable for arrays.

On the other hand, the surface emitting laser shown in FIG. 23 emits light in a direction perpendicular to the substrate, and thus has an advantage that a two-dimensional array is easy and a high-density matrix array is manufactured. Excellent coupling efficiency to optical components. Therefore, for an optical switch, an optical interconnection, or the like, a surface emitting laser array capable of high precision and high density is considered to be promising in consideration of coupling to an optical element or a fiber or the size of an array element.

[0007] Further, it is desirable that the polarization direction be stable in application of the semiconductor laser array to optical communication and optical computers. This is not only due to the use of polarization-dependent optical elements in the optical information processing system configuration, but also polarization instability in the entire system due to polarization dependence in any system due to the end face reflection of the elements. In order to

Regarding the polarization of a semiconductor laser array, which is important in optical communications and optical computers, the end-emitting type semiconductor laser is a special array-based laser except that the pitch is as small as the wavelength and mode coupling occurs. There is no polarization limiting effect and the polarization characteristics of each element are maintained. Therefore, in the array, the polarization parallel to the substrate due to the TE mode predominates.

On the other hand, in the case of a surface emitting laser, since there is no limiting factor for the polarization, polarization may appear in a random direction in each element, and the polarization direction may be unstable, and switching may occur due to driving current or temperature. is there.

A vertical cavity surface emitting laser, which is one of the surface emitting lasers, has a resonator formed by two sets of upper and lower semiconductor multilayer reflective films as disclosed in Japanese Patent Application No. 3-34754, and is formed on a substrate. This is a semiconductor laser that emits light in the vertical direction. Compared to edge-emitting stripe lasers, they have features such as a narrower emission angle, a larger vertical mode interval, and easier arraying.

At present, in a system such as an optical communication system using a semiconductor laser as a light source, it is indispensable to use a beam splitter or a polarizer depending on the direction of polarization. is important.

There have been several reports on attempts to control the polarization of a vertical cavity surface emitting laser, but there are two main types.

One is an attempt to impart anisotropy to the reflectivity of the multilayer reflective film by Mitsuaki Shimiz.
u et ga Japanese Journal of Applied
Physics Vol.30, page L1015-L1017 (J
aperture Journal of Applier
d Physics Vol. 30, PP. L1015
As shown in (10-17, 1991), there is an example in which only two opposing sides of the upper semiconductor multilayer film are covered with a metal having a high reflectance, but the experimental results have confirmed the effectiveness of this method. Absent.

Another method is to apply anisotropic stress to the active layer by using Toshikazu Mukai.
Hara et al., Japanese Journal of Applied Physics, Vol. 31, pp. 1389-1390 (J
aperture Journal of Applier
d Physics, 31, pp. 1389-139
0, 1992), the substrate is dug into an ellipse and anisotropic stress is applied to obtain polarized light parallel to the long axis. However, when stress is applied to the substrate, heat due to temperature change is obtained. It is not realistic because it is susceptible to swelling, packaging, and stress generated during handling.

In other cases, as disclosed in Japanese Patent Application Laid-Open No. 1-265584, there is an attempt to provide a rectangular high-refractive-index waveguide in the light-emitting portion and pass polarized light parallel to its long side. It is questionable whether light is effectively confined in the wave part, and it is considered that the polarization control effect using the light is not strong.

As disclosed in Japanese Patent Application Laid-Open No. 4-242989, there is an example of a type of gain confinement type laser in which anisotropic gain is provided by an electrode having an anisotropic shape. Since the light is weakly diverging and the ratio (light confinement coefficient) confined under the electrode is very small, the anisotropy of the gain given by the change in the electrode shape is very weak. Therefore, it is considered that the polarization control effect using this is small.

Japanese Patent Application Laid-Open No. 4-144183 discloses an example in which the polarization control is attempted by making the vertical resonator portion anisotropically having two axes. FIG. 10 shows a view of this element as viewed from above. This publication does not disclose anything about the physical basis of polarization control, but only states that a polarization parallel to the long axis can be obtained. The fact that a surface emitting laser having a rhombic cross section as shown in FIG. 10 (b) has no polarization control effect is disclosed in IEE Photonics Technology Letters Vol.
One page (IEEE Photonics Techn)
logic Letters, 6, pp. 40-42
1994), a surface emitting laser having an elliptical cross section (FIG. 10A), which is another embodiment, is sufficiently described in [Prior Art] of JP-A-1-266584. It is described that there is no significant polarization control effect, and it was not possible to control the polarization direction simply by making the cross-sectional shape of the resonator anisotropic.

[0018]

When a semiconductor laser array is manufactured by arranging separately manufactured semiconductor lasers, in the case of an edge-emitting semiconductor laser array, an edge-emitting laser having polarization parallel to a substrate is moved in a desired direction. The polarization of the laser array can be set arbitrarily by arranging the substrates in an inclined manner. However, in this case, it is difficult to arrange the laser array by fusion to the same heat sink with reference to the normal substrate surface, and the fabrication is extremely difficult. Will be difficult.

When the polarization direction of the conventional semiconductor laser array is monolithically fabricated on the same substrate, the polarization direction of the edge-emitting type semiconductor laser array is only a component parallel to the substrate. Although various attempts have been made, polarization control has not been sufficiently performed, and thus the surface-emitting laser array has completely different polarizations for individual laser elements.

Further, in the conventional example, only data on a few elements are shown. Actually, several tens of elements due to poor reproducibility factors such as scratches at the time of device fabrication, stress and return light at the time of device evaluation. Are that the polarization directions are aligned. Therefore, in the evaluation of the polarization control, even if the polarization direction of at least about fifty elements is examined, it is necessary that the polarization control be still good.

The above-mentioned conventional surface emitting laser has another problem in addition to the inability to control the polarization. For one, the semiconductor laser does not show linearly polarized light, so that the polarization direction is not determined. In addition, the diameter of the cross section perpendicular to the light waveguide direction is large, so that the transverse mode or longitudinal mode may not be single. In the case of multiple modes, the polarization is not necessarily in the same direction in each mode. Therefore, the control of the polarization needs to be realized with a device that exhibits linear polarization and is small enough to obtain a single mode.

Further, since there is no concept of a laser array in which the polarization direction is arbitrarily set, there is no actual example of a system using the laser array. However, as will be described later, if the polarization direction is arbitrarily set in one array, Various system applications, such as optical path control using polarization and polarization multiplexing communication, can be considered.

An object of the present invention is to provide a surface emitting laser which oscillates in a single transverse mode in which the polarization direction of at least 50 or more surface emitting elements can be aligned in a certain direction, and further, a monolithic laser using the same. An object of the present invention is to provide a surface emitting laser array in which the polarization direction of each element in one array can be set arbitrarily.

It is another object of the present invention to provide various optical information processing devices such as optical path control using polarization set arbitrarily in a laser array and polarization multiplexing communication.

[0025]

A surface emitting laser according to the present invention comprises an intermediate layer comprising an active layer and a light confinement layer sandwiching the active layer on a semiconductor substrate, and first and second layers above and below the intermediate layer.
A surface emitting laser having a semiconductor multilayer reflective film, wherein only the first semiconductor multilayer reflective film has a post structure;
The distance between the bottom of the structure and the active layer is about one wavelength in optical length,
The side surface of the first semiconductor multilayer reflective film has a set of planes parallel to each other, the cross-sectional diameter of the first semiconductor multilayer reflective film parallel to the substrate is smaller than the cross-sectional diameter of the second semiconductor reflective film, and Oscillations in one transverse mode (0th mode) and single longitudinal mode (0th mode) are formed on the pair of mutually parallel planes, among sides constituting a cross section of the first semiconductor multilayer reflective film. most rather long, sides in, characterized <br/> have a polarized light parallel to the sides.

The surface emitting laser according to the present invention is a pair of upper and lower distributed reflection type (DBR; Distr) comprising a semiconductor periodic multilayer film.
A vertical resonator is constituted by an integrated Bragg Reflector reflector, an intermediate layer sandwiched between the upper and lower reflectors comprises an active layer and a light confinement layer, and only the upper reflector has side walls perpendicular or perpendicular to the substrate. And the active layer other than the lower portion of the post structure has an inactive region, and the cross-sectional area of the post structure is sufficiently small to have a fundamental single transverse mode (zero order mode) and a single longitudinal mode. The light emitted in the mode that oscillates in the mode is linearly polarized light, and the distance between the bottom of the post structure and the active layer is one wave at the optical length.
The cross-section of the post structure, which is approximately long and parallel to the substrate, has a pair of parallel sides facing each other, the parallel sides are straight lines, and the parallel sides are longer and parallel than the straight lines connecting their opposite end points. equal to or longer linear than the side without the presence in the cross section, straight and Ri graphic der linearly and light is similar to a straight line to the extent that feel straight line, have a polarized light parallel to the parallel sides
Characterized in that it.

Further, the distance between the lowermost portion of the post structure of the upper reflector and the active layer is about one wavelength.

The surface emitting laser array of the present invention is characterized in that the polarization of each element is set in an arbitrary direction in one monolithic surface emitting laser array.

Each surface emitting laser of the surface emitting laser array has an intermediate layer comprising an active layer and a light confinement layer sandwiching the active layer on a semiconductor substrate, and first and second layers above and below the intermediate layer.
And a second semiconductor multilayer reflective film, wherein only the first semiconductor multilayer reflective film has a post structure, and a cross section of the first semiconductor multilayer reflective film oscillates in a single fundamental transverse mode. The cross-sectional shape of the post structure is anisotropic and imparts anisotropy to the transverse mode shape, and the distance between the lowermost portion of the post structure of the upper reflective film and the active layer is about one optical length. The direction of the post is arbitrarily set for each element.

Each surface emitting laser of the surface emitting laser array is characterized in that the polarization is alternately different by 90 degrees between adjacent lasers.

Each of the surface emitting lasers in the surface emitting laser array is characterized in that the polarization direction is shifted by 30 degrees.

The surface emitting laser array includes a group of surface emitting laser arrays having the same polarization direction, and one or several surface emitting lasers having different polarization directions from the group of surface emitting laser arrays having the same polarization direction. Is defined as one unit, and is configured by an array group of a plurality of units.

An optical interconnection device according to the present invention comprises a surface emitting laser array in which the polarization of each light emitting element is set in an arbitrary direction, and a polarizing element for separating light from the surface emitting laser array into mutually different polarized components. And characterized in that:

An optical interconnection apparatus according to the present invention includes the surface emitting laser array, and a polarization beam splitter for splitting light from the surface emitting laser array into transmission signal light and control signal light. I do.

Further, the control signal light is monitor light for a surface emitting laser array.

According to the free space optical connection method of the present invention, the polarization of each light emitting element is set in an arbitrary direction in the surface emitting laser array, and the light emitted from the surface emitting laser is divided into a polarization optical element for dividing a polarization component. Light is incident, and the optical path of each light emitting element is determined by setting the polarization direction.

The stereoscopic image display apparatus of the present invention is characterized in that a laser matrix array whose polarization is alternately different by 90 degrees is used as a light source.

An optical switch network according to the present invention includes a switch node having a semiconductor laser array for emitting at least two laser beams having polarization directions different from each other by 90 degrees and exhibiting linear polarization, and a light receiving element corresponding to each of the semiconductor lasers; A polarization reflection unit that reflects one polarized light component emitted from the switch node to guide the light to a light receiving element in a different switch node by changing an optical path.

A polarization multiplexing transmission apparatus according to the present invention comprises: a semiconductor laser array for emitting at least two laser beams having polarization directions different from each other by 90 degrees and exhibiting linear polarization; one optical fiber for transmitting the two laser beams; And an optical element for condensing the two laser lights and guiding the laser light to the one fiber.

The polarization shift keying type coherent optical communication device of the present invention is characterized in that it has a light source that alternately modulates two laser lights showing linearly polarized light whose polarization directions of the respective light emitting elements are different by 90 degrees in the surface emitting laser array. And

[0041]

For example, as described in Max Born and Emil Wolf, "Principles of Optics I" translated by Toru Hirakawa and Eiji Yokota (Tokai University Press, 1988, 6th pp. 51-73), reflection on a plane is generally Polarized light parallel to the plane has low transmittance, and perpendicular polarized light has high transmittance. Therefore, in a post structure having a straight line in a cross section, that is, a post structure having a flat surface on the side surface as in the present invention, a polarization component parallel to the side surface has a small diffraction loss due to transmission of light out of the post. Conversely, a polarization component perpendicular to the side surface has a large diffraction loss due to transmission of light outside the post. As a result, polarized light parallel to the plane side surface becomes dominant. Originally, in a vertical resonator using a DBR, light reciprocates up and down, and the influence on the side of the post is small. However, in the present invention, since the post size is small enough to obtain the fundamental transverse mode, the post size is affected by the diffraction loss on the side surface of the post. Further, in the present invention, the upper DBR is post-processed to confine the light in the lateral direction, but the lower DBR is post-processed.
Since the BR reflector is not processed, the lateral confinement of light is small at the lower DBR and the light spreads. As a result, an oblique component appears in the traveling direction of the reciprocating light, and the post is more susceptible to the diffraction loss on the side surface.

Further, in the present invention, since the distance between the bottom of the post structure and the active layer is as short as about one optical length, the above-mentioned plane side surface can be affected at a position where the light intensity is strong.

In the present invention, since the polarization direction of the surface emitting laser can be set to one direction, a monolithic semiconductor laser array of high density and high precision can arbitrarily change the polarization direction of each element in one array. A semiconductor laser array that can be set can be obtained.

Further, since the polarization direction is arbitrary, various functions can be provided in combination with a polarization dependent optical component such as a polarization beam splitter.

[0045]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the surface emitting laser according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the surface emitting laser of the present invention. This is a laser that forms a resonator with upper and lower two sets of GaAs / AlAs semiconductor multilayer reflective films 2 and 6 and emits light in a direction perpendicular to the substrate. The intermediate layer is an InGaAs active layer 3
And an AlGaAs light confinement layer 4. The upper, anode-side semiconductor multilayer reflective film 2 is processed into a post shape by reactive ion beam etching. The active layer 3 other than the lower portion of the post is modified into the inactive region 5 by proton implantation. Further, etching is performed to penetrate to the lower cathode side semiconductor multilayer reflective film 6, and the cathode 7 is taken there. The anode 1 covers the entire post with an electrode material. A current flows between the cathode 7 and the anode 1 to perform laser oscillation. The cross section 8 of this surface emitting laser is 6 μm ×
Use a rectangle of 5 μm.

In the surface emitting laser having this structure, when the size of the cross section of the post is smaller than 6.5 μm × 6.5 μm, both the horizontal mode and the vertical mode become single modes, and show linearly polarized light. For example, as shown in Kikuhiko Okubo, "Optical Fiber Technology of ISDN itself (Rigaku Corporation), page 1-17, in the case of a single mode optical fiber, the size of the core diameter 9 at which a single mode is obtained is shown in FIG. As shown in FIG. 2, the mode size 11 is slightly larger than the core diameter 9.

Similarly, in this embodiment, as shown in FIG. 3, the post diameter is so small that a single mode can be obtained.
Is slightly larger than post size 12. Therefore, it is affected by the structure of the post side surface, and the polarization control by the post shape works effectively.

Conversely, in the case of a post having a large diameter where a single mode cannot be obtained as in the conventional example, the polarization control by the structure of the post side surface does not occur essentially.

Originally, in the single mode, light travels straight, so that the influence of the side surface is small. However, in the embodiment, only the upper DBR is processed, so that the lower DBR has no factor to confine light in the lateral direction. Therefore, as shown in FIG. 5, the light spreads at the lower part and has an oblique component. Therefore, the structure is more susceptible to the influence of the post side surface.

The post section 8 of the present invention is rectangular. Therefore, the post side is surrounded by a plane. As shown in FIG. 5, the light leaking from the inside of the post 13 to the outside of the post is the polarized light 1 that is parallel to the polarized light 15 that is perpendicular to the plane of the post side surface 17.
The value greater than 6 is as described above.

In the surface emitting laser of the present embodiment having a rectangular post structure of 6 × 5 μm, the loss of the polarized light 15 perpendicular to the long side 18 and the short side 19 increases on both the long side 18 and the short side 19. On the other hand, as shown in FIG. 6, since the ratio of the total loss from each side is simply substantially equal to the length ratio, the loss of polarized light perpendicular to the long side on the long side 18 increases. As a result, polarized light perpendicular to the short side, that is, parallel to the long side (polarized light perpendicular to the short side) becomes dominant.

In the surface emitting laser having the structure used in this embodiment, Kosaka et al., IEEE Photonics Technology Letters, vol. 6, p. 323 (H. Kosakae).
tal. , IEEE Photonics Lette
(rs 6,323, 1994), when the length of one side is smaller than 6 μm, the diffraction loss sharply increases.
Therefore, in the present invention utilizing the loss, the size is set to 6 μm
It is very effective to reduce the diameter based on the diameter.

Considering the light field, as shown in FIG. 4, when the active layer 3 is farthest away, it becomes weak. Therefore, in order to obtain the best effect in the embodiment, the post bottom 2
It is desirable that the distance between 4 and the active layer 3 be short. However, if it is too close, current will only flow through the end of the post and will not be injected into the center. As a result, high injection is required for laser oscillation, and the transverse mode becomes unstable. Therefore, there is an optimum value for the distance between the post and the active layer, and good results are obtained at the optical length of about 1 shown in the embodiment.

FIG. 7 shows that the cross-sectional size is changed from 6 × 6 μm to 6 × 6 μm.
For a surface emitting laser 8 × 8 matrix array (64 elements) changed to 3.5 μm every 0.25 μm,
The ratio of the direction of polarized light is shown. When the size of the short side is reduced from 6 μm, the polarization parallel to the short side once increases. This is, for example, “Microwave” by Eitaro Abe (University of Tokyo Press: 198
As is well known in a general rectangular micro waveguide described on page 54, 3rd edition, the polarization of the fundamental mode is originally parallel to the short side in the rectangular waveguide as shown in FIG. (The figure shows the case where there is no leakage loss outside the waveguide.)
Moreover, where the size of the long side and the short side does not change much, there is not much difference in the loss on the side of the polarized light perpendicular to the long side and the short side, so the polarization control effect is small, and the basic polarized light by the rectangular shape This is because the direction becomes dominant. Further shortening the length of the short side increases the loss of polarized light in the vertical direction on the side surface of the long side, so that polarized light parallel to the long side gradually becomes dominant, and polarized light parallel to the long side remains.

Further, by optimizing the distance between the active layer and the post, the light field at the post can be strengthened and the influence of the loss can be increased. 5 μm in this embodiment
In the following, the polarization became 100% parallel to the long side, and complete polarization control was realized. The rectangular shape is 6 × 4.25μ in FIG.
It is considered that the reason why the value of m was not 100% was that some of the post shapes were broken during the fabrication of the device.

FIG. 9 shows a cross section of a post structure other than a rectangle according to the embodiment of the present invention. As shown in the figure, the shape of the post in this embodiment is not limited to a rectangle, and it is sufficient that the longest set of sides in the cross section is longer than the other sides.

In this embodiment, the GaAs / AlAs material is used, but another material may be used. In that case, the cross-sectional size changes with the optical length of the oscillation wavelength.

The sides constituting the cross section of the post structure parallel to the substrate of the present embodiment need not be straight as long as the light is within a range in which light can be felt as straight (less than one wavelength).

An embodiment of the surface emitting laser array of the present invention will be described below with reference to the drawings.

FIG. 11 shows the arrangement of the first embodiment of the surface emitting laser array according to the present invention. The individual semiconductor lasers use the surface emitting laser of the above embodiment. In a refractive index guided surface emitting laser using a post structure, the cross section of the post is made sufficiently small to be about 6 μm at which a fundamental transverse mode can be obtained, and the post is cross-sectioned so that polarization is defined in one direction.

The substrate is polished to a thickness of 100 μm, and the doping is 4 × 10 ¹⁸ cm ^{-3 for the} electrode contact portion and 1 × 10 ¹⁸ cm ^-3 or less for the semiconductor multilayer reflective film. As shown in FIG. 11, the rectangular posts are arranged so as to be different from each other by 90 degrees.

FIG. 12 is a diagram showing the polarization direction in the array of the present invention. The polarization direction 2 is 125 μm as shown in FIG.
Alternating polarizations of approximately 90 degrees are obtained alternately in an 8 × 8 64 matrix array with a pitch.

When a fiber array 103 as shown in FIG. 13 is coupled to this array, crosstalk can be greatly reduced by interposing a polarizer between the laser array and the fiber array. The tolerance for the displacement can be at least ^21/2 times.

FIG. 14 shows a second embodiment of the surface emitting laser array according to the present invention.

FIG. 14 shows a rectangular post surface emitting laser used in the first embodiment of the surface emitting laser array having a polarization direction of 30.
This is a surface emitting laser array shifted by degrees. At this time,
When the light passes through the polarizer, the transmitted light intensity becomes cos 30 degrees, cos 60 degrees, and cos 90 degrees with respect to the output of the first laser light.
Degree, that is, 0.87, 0.5, and 0 times, so that the light intensity in the array can be changed without requiring a special driving circuit.

In the present embodiment, the deviation angle of the polarization direction of the surface emitting laser of the rectangular post is set to 30 degrees. However, the present invention is not limited to this.
s30, cos45,..., cos90 times, that is, 0.97, 0.87, 0.7,.

Hereinafter, an example of an optical information processing apparatus to which the surface emitting laser array of the present invention is applied will be described.

FIG. 15 shows a first embodiment of the optical interconnection to which the surface emitting laser array of the present invention is applied.

In FIG. 15, the structure of the light source is such that a transmission signal array composed of eight longitudinally polarized lasers 123 is added with a control signal laser composed of one horizontal polarized laser 120 to make one unit, and these are arranged in parallel. Eight are arranged. The light emitted from the light source is a polarizing beam splitter (PBS) 11.
At 8, the laser light from the transmission signal array is transmitted, and the control signal light 123 having a polarization direction different from that of the transmission signal light 122 by 90 degrees is separately extracted. Driving of the semiconductor lasers is performed collectively for each row of the transmission signal array including eight elements. The control signal is transmitted as a signal used for centralized management such as a signal indicating that the column is being transmitted.

FIG. 16 shows a second embodiment of the optical interconnection to which the surface emitting laser array of the present invention is applied.

In the surface emitting laser array of the present embodiment, one row composed of nine laser arrays is simultaneously driven. Of these, only the middle one is monolithically formed with the polarization direction shifted by 15 degrees. As a result, an optical output of about 3% can be separated by the polarizing beam splitter (PBS) 118, and the separated monitor light 125 for APC is converted into an automatic output control device (APC: Auto Power Control).
ller) monitor light.

FIG. 17 shows a third embodiment of the optical interconnection to which the surface emitting laser array of the present invention is applied.

In the surface emitting laser array of this embodiment, a laser array in which the polarization directions of the two central elements are shifted by 45 degrees is formed. The output light of the horizontally polarized laser 120 is split by the polarizing beam splitter (PBS) 118 to the upper part of the PBS 118, and the output light of the vertically polarized laser 123 passes through the polarizing beam splitter 118. Further, the output light of the 45-degree polarized laser 133 is divided into two equal parts, ie, transmission and reflection to the upper part of the PBS, and is separated into half intensity lights 134 for different polarization directions.

In this embodiment, the polarization is set for each column in one stage. However, by setting each individual element and performing multi-stage connection, more complicated free space optical path determination can be realized in the optical interconnection. Needless to say.

FIG. 18 shows an embodiment of a stereoscopic video display apparatus to which the surface emitting laser array of the present invention is applied.

The light emitting section 135 of the stereoscopic video display apparatus of the present invention is constituted by a laser matrix array 136, and the individual elements are arranged so that the polarization directions are perpendicular to each other. It is built in an array.

For example, by displaying the right-view image with vertical polarization and the left-view image with horizontal polarization, a stereoscopic image can be viewed using polarized glasses. By using the surface emitting laser array of the present invention, it is not necessary to use a matrix-type polarizing filter, which has been conventionally required, and therefore, it is possible to prevent thermal deterioration of the filter due to light absorption by the polarizing filter and decrease in brightness of the screen. .

FIG. 19 shows a 4 × optical switch network of the present invention.
4 shows an embodiment of the shuffle network of FIG.

In FIG. 19, the switch node 119 is
A surface emitting laser that emits polarized light 115 parallel to the paper surface, a surface emitting laser that emits polarized light 116 perpendicular to the paper surface, and a photodetector (not shown) corresponding to each semiconductor laser are configured as one unit.

The switch node 119 having the above configuration has four rows and three rows.
Are arranged in a row, and a polarizing beam splitter (PBS) 1 is disposed between the switch nodes 119.
18 and the polarization beam splitter 1
18 and a total reflection mirror 117 are arranged, and a laser beam is made incident on a switch node 119 adjacent to the switch node 119 facing by the polarizing beam splitter 118. The total reflection mirror 117 causes the laser light to be incident on the switch node 119 adjacent to the switch node 119 facing the switch node 119.

In this embodiment, the optical path is distributed by a simple optical system composed of one polarization beam splitter 118 or a combination of one polarization beam splitter 118 and a total reflection mirror 117 for two semiconductor lasers having different polarization directions. Can be configured.

In this embodiment, the number of lasers at the switch node is two. However, the number of lasers is not limited to two, and two or more lasers are possible.

In this embodiment, the optical switch network is in the direction parallel to the plane of the paper. In addition to this, the optical switch network can also be configured in the direction perpendicular to the plane of the paper.

FIG. 20 shows an embodiment of the polarization multiplex transmission apparatus of the present invention.

The light source is composed of a semiconductor laser that emits polarized light 115 parallel to the paper and a semiconductor laser that emits polarized light 116 perpendicular to the paper. Light emitted from each of the semiconductor lasers is collimated by a PML (parallel plate lens) 126 and further condensed by a converging convex lens to form a single mode fiber (SMF: Single).
(Mode Fiber) 128. SM
Since the orthogonal relationship of polarization is maintained in F128, two lasers having polarizations whose polarization directions are different by 90 degrees are separately modulated, and polarization multiplexing transmission can be performed by one SMF128.

Although the light is no longer linearly polarized during the transmission of the SMF 128, the orthogonal relationship is maintained. Therefore, the original two linearly polarized lights can be converted by passing the Soleil-Ubbine phase compensator 129 to the receiving side, and further separated by the polarizing beam splitter 118. The light is received by the photodetector 130.

FIG. 21 shows an embodiment of the optical communication apparatus according to the present invention. In the present embodiment, polarization shift keying (polarization shift) using two laser elements is performed.
keying) transmission device was used as an example.

In polarization shift keying transmission, which is a type of coherent optical communication, conventionally, the signal modulation on the transmission side uses a polarization modulation element using liquid crystal. When a polarization modulation element using liquid crystal is used, the modulation speed is at most 1000 bi.
s / s, which is slow, which has been a problem of speeding up optical information processing.

On the other hand, in the present invention, the laser array composed of two semiconductor lasers whose polarizations are perpendicular to each other is alternately illuminated to perform modulation. Therefore, the modulation speed of each laser is as high as several Gbit / s, and high-speed modulation is performed. Is possible.

Single mode fiber (SMF) 128
Is propagated, and the local light 131 is merged by the merger 32,
After passing through the polarization beam splitter 118, the photodetector 130 detects a beat component, thereby performing transmission by the polarization shift keying method.

[0092]

Since the surface emitting laser of the present invention can completely control the polarization, it can be applied to optical computing and optical communication without using an optical element such as a polarizing element for aligning the polarization of the elements. And the system can be simplified.

By using the laser array according to the present invention in which the polarization direction is arbitrarily set, various functions such as a polarization multiplexing transmission device and a free space optical path determination method are realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a structure of a surface emitting laser having a rectangular cross section.

FIG. 2 is a diagram showing a relationship between a core diameter and a mode size in a single mode fiber.

FIG. 3 is a diagram showing a relationship between a post size and a mode size in a rectangular section post.

FIG. 4 is a diagram for explaining polarization dependence of leakage loss on a side surface of a post.

FIG. 5 is a diagram showing that the total loss is large on the long side.

FIG. 6 is a diagram illustrating a shape of a light field in a vertical cross section of the surface emitting laser.

FIG. 7 is a diagram showing post-size dependence of the ratio of polarization.

FIG. 8 is a diagram illustrating a polarization direction of a fundamental mode in a rectangular waveguide.

FIG. 9 is a diagram showing an example of a cross-sectional shape other than a rectangle applicable to the present invention.

FIG. 10 is a diagram showing a cross-sectional shape of a conventional surface emitting laser.

FIG. 11 is a diagram illustrating a surface emitting laser matrix array of the present invention having polarizations that differ by 90 degrees alternately.

FIG. 12 is a diagram showing a polarization direction of the laser array shown in FIG.

FIG. 13 is a diagram showing a two-dimensional fiber array.

FIG. 14 is a diagram showing a surface emitting laser array of the present invention having polarizations different by 30 degrees.

FIG. 15 is a diagram showing a laser matrix array including columns of a one-dimensional array of eight transmission lasers and one control laser having different polarization directions.

FIG. 16 is a diagram showing a laser matrix array composed of columns of a one-dimensional array of lasers using one of nine lasers as APC monitor light.

FIG. 17 is a diagram showing free-space optical path determination using a laser matrix array in which polarization is set for each column.

FIG. 18 is a diagram illustrating a stereoscopic display device using a laser matrix array having alternately perpendicular polarizations.

FIG. 19 is a diagram showing a 4 × 4 shuffle net of the present invention using an array having vertically polarized light as a light source.

FIG. 20 is a diagram illustrating polarization multiplexing transmission of the present invention.

FIG. 21 is a diagram showing a polarization shift keying type optical transmission device of the present invention using one array having vertical polarization as a light source.

FIG. 22 is a view showing a conventional monolithic edge-emitting stripe laser array.

FIG. 23 is a diagram illustrating a surface emitting laser having a post structure.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 anode 2 post-shaped anode-side multilayer reflective film 3 InGaAs active layer 4 light confinement layer 5 inactive region by ion implantation 6 cathode-side semiconductor multilayer reflective film 7 cathode 8 surface emitting laser cross section 9 core 10 clad 11 mode size 12 post size 13 Inside post 14 Outside post 15 Polarization perpendicular to the side 16 Polarization parallel to the side 17 Post side 18 Long side 19 Short side 20 Post cross section 21 Loss on the long side Polarization perpendicular to the long side 22 Loss on the short side Polarization perpendicular to the short side 23 Field of light 24 Post structure bottom surface 25 Rectangular waveguide 26 Polarization direction 101 Rectangular post 102 Polarization direction 103 Optical fiber array 104 Electrode 105 Silicon oxide 106 Mesa stripe 107 Active layer 108 Anode 109 Anode semiconductor Multilayer reflective film 110 InGaAs active layer 111 light Confinement layer 112 Passivation region 113 Cathode-side semiconductor multilayer film 114 Cathode 115 Polarization parallel to the paper 116 Polarization perpendicular to the paper 117 Total reflection mirror 118 Polarization beam splitter 119 Switch node 120 Horizontally polarized laser 121 Control signal light 122 Transmission Signal light 123 Vertically polarized laser 124 15-degree polarized laser 125 APC (Auto Power Contro)
monitor light 126 PML (Planar Micro Lens)
s) 127 Converging convex lens 128 SMF (Single Mode Five)
r) 129 Babinet Soleil phase compensator 130 PD (Photo Detector) 131 Local light 132 Combiner 133 45 degree polarized laser 134 1/2 intensity light 135 Light emitting unit 136 Laser matrix array with alternately perpendicular polarization

────────────────────────────────────────────────── ─── Continuation of the front page (56) References Proceedings of the 55th Annual Meeting of the Japan Society for the Study of Natural Sciences, Fall 22p-S-5 p. 975 Appl. Phys. Lett. 66 [8] (1995) p. 908-910 Electron, Lett. 31 [18] (1995) p. 1573-1574 (58) Field surveyed (Int.Cl. ⁶ , DB name) H01S 3/18

Claims (15)

(57) [Claims] 1. A surface emitting laser comprising: an intermediate layer comprising an active layer and a light confinement layer sandwiching the active layer on a semiconductor substrate; and first and second semiconductor multilayer reflective films above and below the intermediate layer. Only the first semiconductor multilayer reflective film has a post structure, and the distance between the lowermost portion of the post structure and the active layer is equal to the optical length.
At about the wavelength, the side surface of the first semiconductor multilayer reflective film has a set of planes parallel to each other, and the cross-sectional diameter of the first semiconductor multilayer reflective film parallel to the substrate is larger than the cross-sectional diameter of the second semiconductor reflective film. The pair of mutually small sides, which are small and oscillate in a single transverse mode (0th-order mode) and a single longitudinal mode (0th-order mode), and constitute a cross section of the first semiconductor multilayer reflective film, rather longest sides in the plane parallel, parallel to the sides
A surface emitting laser having polarized light . 2. A pair of distributed reflection type (DBR; Distributed Bragg) comprising a semiconductor periodic multilayer film.
g Reflector) A vertical resonator is constituted by a reflector, an intermediate layer sandwiched between the upper and lower reflectors comprises an active layer and a light confinement layer, and only the upper reflector has a side wall perpendicular or perpendicular to the substrate. The post structure has a close angle, the active layer other than the lower part of the post structure has an inactive region, and the cross-sectional area of the post structure is sufficiently small to be a fundamental single transverse mode (zero order mode) and a single longitudinal mode. the light emitted by the magnitude of oscillation in is linear polarized light, and the post structure bottom
The distance from the active layer is about one wavelength in optical length, and the cross section of the post structure parallel to the substrate has a pair of parallel sides facing each other,
A parallel side is a straight line, a parallel side is longer than a straight line connecting its opposite end points, and a straight line equal to or longer than the parallel side does not exist in the cross section. graphic der similar to the straight line to the extent that the feel is, this
A surface-emitting laser having a polarization parallel to a parallel side of the surface-emitting laser. 3. A surface emitting laser array, wherein the polarization of each element is set in an arbitrary direction in one monolithic surface emitting laser array. 4. The surface emitting laser of the surface emitting laser array comprises an intermediate layer comprising an active layer and a light confinement layer sandwiching the active layer on a semiconductor substrate, and first and second semiconductors above and below the intermediate layer. A surface emitting laser having a multilayer reflective film, wherein only the first semiconductor multilayer reflective film has a post structure,
The cross section of the first semiconductor multilayer reflective film is small enough to oscillate in a single fundamental transverse mode, and the cross-sectional shape of the post structure is anisotropic and gives anisotropy to the transverse mode shape. 5. The surface emitting laser array according to claim 4, wherein the distance between the lowermost portion of the post structure and the active layer is about one optical length, and the direction of the post is arbitrarily set for each element. 5. The surface emitting laser array according to claim 4, wherein the surface emitting lasers of the surface emitting laser array alternately differ in polarization by 90 degrees between adjacent ones. 6. The surface emitting laser array according to claim 4, wherein the polarization directions of the surface emitting lasers of the surface emitting laser array are shifted by 30 degrees. 7. A surface-emitting laser array comprising a group of surface-emitting laser arrays having the same polarization direction and one or several surface-emitting lasers having different polarization directions from the group of surface-emission laser arrays having the same polarization direction. 5. The surface-emitting laser array according to claim 4, wherein the unit is a unit, and the array comprises a plurality of units. 8. A surface emitting laser array in which the polarization of each light emitting element is set in an arbitrary direction, and a polarizing element for separating light from the surface emitting laser array into mutually different polarized components. Optical interconnection device. 9. A surface emitting laser array according to claim 8, further comprising: a polarizing beam splitter for splitting light from the surface emitting laser array into transmission signal light and control signal light. Optical interconnection equipment. 10. The optical interconnection device according to claim 10, wherein said control signal light is monitor light for a surface emitting laser array. 11. The polarization of each light emitting element is set in an arbitrary direction in a surface emitting laser array, and light emitted from the surface emitting laser is made incident on a polarization optical element for dividing a polarization component. A free space optical connection method, wherein an optical path of each light emitting element is determined by setting. 12. A three-dimensional image display apparatus characterized in that a laser matrix array whose polarization is alternately different by 90 degrees is used as a light source. 13. A switch node having at least two laser beams having polarization directions different from each other by 90 degrees and exhibiting linearly polarized light, a switch node having a light receiving element corresponding to each of the semiconductor lasers, and a switch node emitted from the switch node. An optical switch network, comprising: a polarization reflection unit that reflects one polarized component and changes the optical path to guide the light to a light receiving element in a different switch node. 14. A semiconductor laser array for emitting at least two laser beams having polarization directions different from each other by 90 degrees and exhibiting linear polarization, one optical fiber for transmitting the two laser beams, and transmitting the two laser beams. A polarization multiplexing transmission device comprising: an optical element for condensing and guiding the light to the one fiber. 15. A polarization shift keying type coherent optical communication device comprising: a light source that alternately modulates two laser lights having linear polarizations of 90 degrees different from each other in a surface emitting laser array. .