US20130027443A1 - Light emission device, light emission device driving method, and projector - Google Patents
Light emission device, light emission device driving method, and projector Download PDFInfo
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- US20130027443A1 US20130027443A1 US13/644,663 US201213644663A US2013027443A1 US 20130027443 A1 US20130027443 A1 US 20130027443A1 US 201213644663 A US201213644663 A US 201213644663A US 2013027443 A1 US2013027443 A1 US 2013027443A1
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- light emission
- gain
- emission device
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y20/00—Nanooptics, e.g. quantum optics or photonic crystals
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/005—Projectors using an electronic spatial light modulator but not peculiar thereto
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/40—Arrangement of two or more semiconductor lasers, not provided for in groups H01S5/02 - H01S5/30
- H01S5/4025—Array arrangements, e.g. constituted by discrete laser diodes or laser bar
- H01S5/4031—Edge-emitting structures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/50—Amplifier structures not provided for in groups H01S5/02 - H01S5/30
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
- H01S5/0425—Electrodes, e.g. characterised by the structure
- H01S5/04252—Electrodes, e.g. characterised by the structure characterised by the material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
- H01S5/0425—Electrodes, e.g. characterised by the structure
- H01S5/04254—Electrodes, e.g. characterised by the structure characterised by the shape
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/04—Processes or apparatus for excitation, e.g. pumping, e.g. by electron beams
- H01S5/042—Electrical excitation ; Circuits therefor
- H01S5/0425—Electrodes, e.g. characterised by the structure
- H01S5/04256—Electrodes, e.g. characterised by the structure characterised by the configuration
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1082—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region with a special facet structure, e.g. structured, non planar, oblique
- H01S5/1085—Oblique facets
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/34326—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer based on InGa(Al)P, e.g. red laser
Definitions
- the present invention relates to a light emission device, a light emission device driving method, and a projector.
- JP-A-11-64789 proposes a method for reducing speckle noise by moving a screen and varying speckle patterns, for example.
- JP-A-11-64789 introduces other problems such as limitation to the type of screen, the need of a motor for moving the screen and other components, and generation of noise from the motor and the like.
- JP-A-4-115585 proposes a method for arraying a light source.
- JP-A-4-115585 uses a laser device as a light emission device for the light source.
- a laser device as a light emission device for the light source.
- An advantage of some aspects of the invention is to provide a novel type of arrayed light emission device and driving method of the light emission device capable of reducing speckle noise and increasing output. It is another advantage of some aspects of the invention to provide a projector including the light emission device.
- a light emission device includes: a first clad layer; an active layer disposed above the first clad layer; a second clad layer disposed above the active layer; a first electrode electrically connected with the first clad layer; and second electrodes electrically connected with the second clad layer. At least a part of the active layer forms a plurality of gain areas.
- the plural second electrodes are provided in correspondence with the plural gain areas.
- the plural gain areas extend from a first side of the active layer to a second side of the active layer opposed to the first side while inclined to a vertical line of the first side in the plan view. At least a first gain area and a second gain area included in the plural gain areas form a set of gain areas.
- a plurality of the sets of the gain areas are provided.
- the first gain area and the second gain area included in each set of the gain areas are disposed in this order in a second direction perpendicular to a first direction extending from the first side to the second side in the plan view.
- the second electrodes disposed above the plural first gain areas are electrically connected with one another by a first common electrode.
- the second electrode disposed above the plural second gain areas are electrically connected with one another by a second common electrode.
- the light emission device which is arrayed and capable of reducing speckle noise and achieving high output can be provided.
- a phrase “electrically connected” is used in sentences such as “a particular component (hereinafter referred to as D component) is electrically connected with another particular component (hereinafter referred to as C component).
- this sentence contains both a condition in which the C component and the D component are electrically connected with each other by direct contact and a condition in which the C component and the D component are electrically connected with each other via a further component interposed between the C and D components.
- each of the plural sets of the gain areas further includes a third gain area.
- the first gain area, the second gain area, and the third gain area included in each of the plural sets of the gain areas may be disposed in this order in the second direction in the plan view.
- the second electrodes disposed above the plural third gain areas may be electrically connected with one another by a third common electrode.
- the light emission device which is arrayed and capable of reducing speckle noise and achieving high output can be provided.
- the light emission device of the first aspect may be configured such that an end surface on the first side and an end surface on the second side do not overlap with each other in each of the plural gain areas in the plan view as viewed from the first side.
- oscillation of laser beams generated in the first gain areas and the second gain areas can be securely reduced or prevented.
- the light emission device of the first aspect may be configured such that the end surface on the first side is shifted from the end surface on the second side in the second direction in each of the plural gain areas.
- the end surface on the first side in the first gain area may overlap with the end surface on the second side in the second gain area adjacent to the first gain area in the plan view as viewed from the first side.
- each distance between the first gain areas and the second gain areas decreases, and the light emission density increases.
- the high-output and compact light emission device can be provided.
- the light emission device of the first aspect may be configured such that the second electrodes contact a contact layer allowing ohmic contact with the second electrodes.
- Each plane shape of the plural gain areas may be the same as each plane shape of the contact surfaces of the second electrodes in contact with the contact layer.
- the contact resistance of the second electrodes can be reduced by the contact layer.
- the light emission device of the first aspect may be configured such that the first common electrode and the second common electrode are conductive layers.
- the first common electrode and the second common electrode may extend in the second direction in the plan view.
- the light emission device can be composed of one chip.
- a method for driving the light emission device of the first aspect includes: supplying voltage to the first common electrode such that lights can be emitted from the respective end surfaces in the plural first gain areas; and stopping the supply of voltage to the first common electrode and supplying voltage to the second common electrode such that lights can be emitted from the respective end surfaces in the plural second gain areas.
- the light emission device which is arrayed and capable of reducing speckle noise and achieving high output can be driven by the method.
- a projector includes: the light emission device according to the first aspect of the invention; a light modulation device which modulates light emitted from the light emission device according to image information; and a projection device which projects an image formed by the light modulation device.
- FIG. 1 is a plan view schematically showing a light emission device according to an embodiment.
- FIG. 2 is a cross-sectional view schematically illustrating the light emission device according to the embodiment.
- FIG. 3 illustrates an active layer of the light emission device according to the embodiment as viewed from a first side.
- FIG. 4 is a plan view schematically illustrating the light emission device according to the embodiment.
- FIG. 5 is a plan view schematically illustrating the light emission device according to the embodiment.
- FIG. 6 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment.
- FIG. 7 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment.
- FIG. 8 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment.
- FIG. 9 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment.
- FIG. 10 is a plan view schematically illustrating a light emission device according to a first modified example of the embodiment.
- FIG. 11 is a cross-sectional view schematically illustrating a light emission device according to a second modified example of the embodiment.
- FIG. 12 schematically illustrating a projector according to the embodiment.
- FIG. 1 is a plan view schematically illustrating the light emission device 100 .
- FIG. 2 is a cross-sectional view schematically illustrating the light emission device 100 taken along a line II-II in FIG. 1 .
- FIG. 1 does not show insulation portions 116 for easy understanding of the figure.
- the light emission device 100 constituted by a semiconductor light emission device in InGaAlP (red) will be discussed.
- the light emission device 100 includes a first clad layer 104 , an active layer 106 , a second clad layer 108 , a first electrode 112 , second electrodes 114 , a first common electrode 180 , and a second common electrode 182 .
- the light emission device 100 can further include a substrate 102 , a contact layer 110 , and the insulation portions 116 .
- the substrate 102 is a first conductive type (such as n-type) GaAs substrate, for example.
- the first clad layer 104 is provided on the substrate 102 .
- the first clad layer 104 is an n-type AlGaP layer, for example.
- a buffer layer may be formed between the first substrate 102 and the first clad layer 104 .
- the buffer layer is an n-type GaAs layer, an InGaP layer or the like. The buffer layer increases crystallinity of the layers formed above the buffer layer.
- the active layer 106 is provided on the first clad layer 104 .
- the active layer 106 has multiple quantum well (MQW) structure which laminates three layers of quantum well structure constituted by InGaP well layer and InGaAlP barrier layer, for example.
- the active layer 106 has a rectangular parallelepiped shape (including cube shape) or other shapes. As illustrated in FIG. 1 , the active layer 106 has a first side 105 and a second side 107 .
- the first side 105 and the second side 107 are opposed to each other. According to the example shown in the figure, the first side 105 and the second side 107 extend parallel with each other.
- a part of the active layer 106 constitutes a plurality of gain areas.
- a first gain area 162 and a second gain area 164 included in the plural gain areas constitute each set of gain areas 160 (gain area set 160 ). That is, each set of the gain area sets 160 has the two gain areas 162 and 164 .
- each set of the gain area sets 160 may have three or more gain areas (see FIG. 10 showing a first modified example described later) with no specific limitation to the number of the gain areas.
- the gain areas 162 and 164 extend from the first side 105 to the second side 107 while inclined to a vertical line P of the first side 105 .
- This arrangement reduces or prevents oscillation of laser beams generated in the gain areas 162 and 164 .
- the first gain areas 162 and the second gain areas 164 are inclined to the vertical line P at the same angle. It is therefore considered that the first gain areas 162 and the second gain areas 164 extend parallel with one another.
- Each shape of the gain areas 162 and 164 in the plan view is parallelogram, for example.
- Each of the first gain areas 162 has a first end surface 170 disposed on the first side 105 , and a second end surface 172 disposed on the second side 107 .
- the first end surface 170 is shifted from the second end surface 172 in a second direction (+Y direction) perpendicular to a first direction (+X direction) extending from the first side 105 to the second side 107 .
- the end surfaces 170 and 172 can be provided as emission slopes for emitting lights generated in the first gain areas 162 .
- Each of the second gain areas 164 has a third end surface 174 disposed on the first side 105 , and a fourth end surface 176 disposed on the second side 107 .
- the third end surface 174 is shifted from the fourth end surface 176 in the second direction.
- the end surfaces 174 and 176 can be provided as emission slopes for emitting lights generated in the second gain areas 164 .
- each reflectance of the sides 105 and 107 is as small as 0% or close to 0% in the wavelength range of the lights generated in the gain areas 162 and 164 .
- the reflectance of the sides 105 and 107 can be decreased by covering the sides 105 and 107 with anti-reflection film.
- the anti-reflection film is dielectric multilayer film, for example.
- the anti-reflection film may be multilayer film produced by laminating SiO 2 layer and SiON layer in this order from the first side 105 .
- emission of lights can be made allowed only from either the first end surface 170 or the second end surface 172 of each of the first gain areas 162 , for example, by providing reflection film (total reflection film or dielectric multilayer film mirror) on either the first side 105 or the second side 107 .
- the gain area sets 160 are plural sets of gain areas disposed in the second direction (+Y direction).
- the example shown in the figure includes three sets of the gain area sets 160 , but the number of sets of the gain area sets 160 is not specifically limited.
- the first gain area 162 and the second gain area 164 included in each set of the gain area sets 160 are disposed in this order in the second direction. It is thus considered that the first gain area 162 and the second gain area 164 are alternately disposed.
- FIG. 3 is a plan view illustrating the active layer 106 as viewed from the first side 105 .
- the first end surface 170 and the second end surface 172 do not overlap with each other in the first gain area 162 .
- the third end surface 174 and the fourth end surface 176 do not overlap with each other in the second gain area 164 .
- direct multiple reflection of lights generated in the first gain area 162 does not occur between the first end surface 170 and the second end surface 172 .
- direct multiple reflection of lights generated in the second gain area 164 does not occur between the third end surface 174 and the fourth end surface 176 .
- a shift width x between the first end surface 170 and the second end surface 172 in the first gain area 162 may have any length as long as the length has a positive value as illustrated in FIG. 3 .
- the first end surface 170 of one of the two adjoining first gain areas 162 does not overlap with the second end surface 172 of the other first gain area 162 in the plan view as viewed from the first side 105 (see FIG. 1 ).
- the third end surface 174 of one of the two adjoining second gain areas 164 does not overlap with the fourth end surface 176 of the other second gain area 164 .
- the first end surface 170 of the first gain area 162 can overlap with the fourth end surface 176 of the second gain area 164 in the plan view as viewed from the first side 105 as illustrated in FIG. 3 .
- the distance between the first gain area 162 and the second gain area 164 decreases, and thus light emission density increases.
- the first gain area 162 and the second gain area 164 alternately emit lights.
- direct multiple reflection does not occur between the end surfaces 170 and 176 even when the end surfaces 170 and 176 overlap with each other.
- the second clad layer 108 is provided on the active layer 106 .
- the second clad layer 108 is a second conductive type (such as p-type) AlGaP layer or the like.
- the p-type second clad layer 108 , the active layer 106 not doped, and the n-type first clad layer 104 constitute a pin diode.
- Each of the first clad layer 104 and the second clad layer 108 has a larger band gap width and a smaller refractive index than those of the active layer 106 .
- the active layer 106 has a function of amplifying light.
- the first clad layer 104 and the second clad layer 108 between which the active layer 106 is sandwiched have a function of confining injection carriers (electrons and positive holes) and light.
- the electrons and positive holes are re-combined in the gain areas 162 and 164 of the active layer 106 .
- This re-combination causes light emission, and induced stimulated emission which occurs from the start point corresponding to the light emission position in a manner of chain reaction.
- the light intensity is amplified in the gain areas 162 and 164 .
- a part of lights generated in the first gain areas 162 is amplified within the first gain areas 162 , and emitted through the first end surfaces 170 or the second end surfaces 172 .
- the gain areas 162 and 164 are light propagation areas (waveguide areas).
- the contact layer 110 is provided on the second clad layer 108 .
- the contact layer 110 is constituted by a layer allowing ohmic contact with the second electrodes 114 , for example.
- the contact layer 110 reduces contact resistance of the second electrodes 114 .
- the contact layer 110 is a p-type GaAs layer, for example.
- the first electrode 112 is formed on the entire area of the lower surface of the substrate 102 .
- the first electrode 112 can contact the layer allowing ohmic contact with the first electrode 112 (the substrate 102 in the example shown in the figure).
- the first electrode 112 is electrically connected with the first clad layer 104 via the substrate 102 .
- the first electrode 112 is one of the electrodes for driving the light emission device 100 .
- the first electrode 112 is produced by laminating a Cr layer, an AuGe layer, an Ni layer, and an Au layer in this order from the substrate 102 , for example.
- a second contact layer (not shown) may be formed between the first clad layer 104 and the substrate 102 and exposed by dry-etching or other method. In this case, the first electrode 112 is disposed on the second contact layer. By this method, single-sided electrode structure can be formed. This structure is particularly effective when the substrate 102 has insulation characteristics.
- the second electrodes 114 are disposed on the contact layer 110 .
- the plural second electrodes 114 are provided in correspondence with the plural gain areas 162 and 164 .
- the surfaces of the second electrodes 114 contacting the contact layer 110 have plane shapes similar to those of the gain areas 162 and 164 .
- the current paths between the electrodes 112 and 114 are determined by the plane shapes of the second electrodes 114 , for example, and the plane shapes of the gain areas 162 and 164 are determined in accordance with the determined current paths.
- the second electrodes 114 are electrically connected with the second clad layer 108 via the contact layer 110 .
- the second electrodes 114 correspond to the other electrode for driving the light emission device 100 .
- the second electrodes 114 are produced by laminating a Cr layer, an AuZn layer, and an Au layer in this order from the contact layer 110 , for example.
- the insulation portions 116 are disposed on the contact layer 110 and between the plural second electrodes 114 . It is thus considered that the insulation portions 116 contact the contact layer 110 positioned above the active layer 106 not having the gain areas 162 or 164 .
- Each of the insulation portions 116 is an SiN layer, an SiO 2 layer, or a polyimide layer, for example.
- the first common electrode 180 and the second common electrode 182 are formed above the second electrodes 114 .
- the first common electrode 180 electrically connects the second electrodes 114 disposed above the plural first gain areas 162 .
- contact holes 190 are formed on the insulation portions 116 positioned above the first gain areas 162 , and the first common electrode 180 and the second electrodes 114 are connected by the contact holes 190 filled with the first common electrode 180 .
- the second common electrode 182 electrically connects the second electrodes 114 disposed above the plural second gain areas 164 . It is thus considered that the insulation portions 116 are provided above the second electrodes 114 in the areas other than the contact holes 190 . As illustrated in FIG.
- the common electrodes 180 and 182 extend in the second direction (+Y axis direction) in the plan view, for example. That is, the common electrodes 180 and 182 cross the gain areas 162 and 164 (the second electrodes 114 ).
- the common electrodes 180 and 182 are conductive layers, and more specifically, layers of material containing copper, aluminum, gold, and others, for example. Though not shown in the figure, the plural second electrodes 114 may be electrically connected with one another by wire bonding.
- FIGS. 4 and 5 illustrate the driving method of the light emission device 100 .
- the light emission device 100 in InGaAlP may be constituted by materials in various systems capable of forming light emission gain areas. Incase of semiconductor material, semiconductor in AlGaN, InGaN, GaAs, AlGaAs, InGaAs, InGaAsP, ZnCdSe, or in others may be employed.
- the light emission device 100 is applicable to a light source for a projector, a display, an illumination device, a measuring device and the like.
- the light emission device 100 in this embodiment has the following characteristics, for example.
- the gain areas 162 and 164 extend from the first side 105 to the second side 107 while inclined to the vertical line P as described above. Moreover, the end surfaces 170 and 174 on the first side 105 do not overlap with the end surfaces 172 and 176 on the second side 107 in the gain areas 162 and 164 , respectively, in the plan view as viewed from the first side 105 . Accordingly, oscillation of laser beams generated in the gain areas 162 and 164 can be reduced or prevented, and thus speckle noise can be decreased. Furthermore, before emitted to the outside, the lights generated in the gain areas 162 and 164 receive gains while traveling through the gain areas 162 and 164 . Thus, higher output lights can be produced by the light emission device 100 than by a typical LED (light emitting diode) in related art. Accordingly, the light emission device provided in this embodiment is a novel light emission device capable of reducing speckle noise and achieving high output.
- the first end surface 170 of the first gain area 162 and the fourth end surface 176 of the second gain area 164 adjacent to the first gain area 162 overlap with each other in the plan view as viewed from the first side 105 .
- the distance between the first gain area 162 and the second gain area 164 decreases, and the light emission density increases.
- the light emission device 100 becomes a high-output and compact device.
- lights are alternately emitted from the first gain areas 162 and the second gain areas 164 as explained above. Accordingly, direct multiple reflection does not occur between the first end surfaces 170 and the fourth end surfaces 176 even when both the surfaces 170 and 176 overlap with each other, and thus oscillation of laser beams can be reduced or prevented.
- the light emission device 100 lights are alternately emitted from the first gain areas 162 and the second gain areas 164 .
- thermal interference between the adjoining gain areas 162 and 164 can be prevented or reduced.
- the thermal interference herein refers to transmission of heat generated within one gain area to another gain area next to the one gain area. The thermal interference lowers light output and changes light emission wavelength in some cases. However, this problem does not occur in the light emission device 100 .
- the plural second electrodes 114 can be electrically connected with one another by the common electrodes 180 and 182 constituted by conductive layers.
- the light emission device 100 can be composed of one chip.
- the plural second electrodes can be electrically connected by wire bonding, for example.
- FIGS. 6 through 9 are cross-sectional views schematically illustrating respective steps for manufacturing the light emission device 100 .
- epitaxial growths of the first clad layer 104 , the active layer 106 , the second clad layer 108 , and the contact layer 110 are allowed on the substrate 102 in this order.
- MOCVD metal organic chemical vapor deposition
- MBE molecular beam epitaxy
- first parts 116 a of the insulation portions 116 are formed on the contact layer 110 . More specifically, the first parts 116 a are produced by forming an insulation layer (not shown) on the entire area and patterning the insulation layer. The contact layer 110 is exposed by the patterning.
- the insulation layer is formed by CVD (chemical vapor deposition) method, coating method or other method.
- the patterning is performed by photolithography, etching or other technology.
- the plural second electrodes 114 are formed on the exposed areas of the contact layer 110 (i.e., on the areas of the contact layer 110 not having the first portions 116 a ).
- the second electrodes 114 are produced by vacuum deposition method or the like.
- second parts 116 b of the insulation portions 116 and the contact holes 190 are produced by providing an insulation layer (not shown) on the entire area and patterning the insulation layer.
- the contact holes 190 are formed in such a manner that the second electrodes 114 can be exposed through the contact holes 190 .
- the common electrodes 180 and 182 are formed as illustrated in FIGS. 1 and 2 .
- the common electrodes 180 and 182 are produced by vacuum deposition method, sputtering method, or plating method, for example.
- the first common electrode 180 is so constructed as to connect the plural second electrodes 114 positioned above the first gain areas 162 with one another.
- the second common electrode 182 is so constructed as to connect the plural second electrodes 114 positioned above the second gain areas 164 with one another.
- the first electrode 112 is formed on the lower surface of the substrate 102 .
- the first electrode 112 is produced by vacuum deposition method, for example.
- the first electrode 112 may be formed before the second electrodes 114 are produced.
- the light emission device 100 capable of reducing speckle noise and providing high output can be produced.
- Light emission devices 200 and 300 according to modified examples of this embodiment are now described with reference to the drawings. According to the light emission devices 200 and 300 , the same reference numbers are given to parts having functions similar to those of constituent parts of the light emission device 100 in this embodiment, and the same detailed explanation is not repeated.
- FIG. 10 is a plan view schematically illustrating the light emission device 200 in correspondence with FIG. 1 .
- FIG. 10 does not show the insulation portions 116 for easy understanding of the figure.
- each set of the gain area sets 160 of the light emission device 200 has the first gain area 162 , the second gain area 164 , and a third gain area 266 .
- the first gain area 162 , the second gain area 164 , and the third gain area 266 included in each set of the plural gain area sets 160 are disposed in this order in the second direction (+Y direction) in the plan view.
- the shape, function and the like of the third gain area 266 are similar to those of the first gain area 162 and the second gain area 164 described above.
- the second electrodes 114 provided above the plural third gain areas 266 are electrically connected with one another by a third common electrode 284 .
- the third common electrode 284 is disposed between the first common electrode 180 and the second common electrode 182 .
- the first common electrode 180 , the second common electrode 182 , and the third common electrode 284 may be positioned in this order in the first direction (+X direction), for example.
- the shape, function and the like of the third common electrode 284 are similar to those of the first common electrode 180 and the second common electrode 182 described above.
- the distance between the adjoining first gain areas 162 becomes longer than that of the light emission device 100 .
- the effect of thermal interference can be further prevented or reduced.
- FIG. 11 is a cross-sectional view schematically illustrating the light emission device 300 in correspondence with FIG. 2 .
- the light emission device 100 is an example of a so-called gain waveguide type.
- the light emission device 300 is of a so-called refractive index waveguide type.
- columnar portions 311 are constituted by the contact layer 110 and a part of the second clad layer 108 as illustrated in FIG. 11 .
- the plane shapes of the columnar portions 311 are the same as those of the gain areas 162 and 164 .
- the current paths between the electrodes 112 and 114 are determined by the plane shapes of the columnar portions 311 , for example, and the plane shapes of the gain areas 162 and 164 are determined based on the determined shapes of the current paths.
- the columnar portions 311 may be formed by parts containing the contact layer 110 , the second clad layer 108 , and the active layer 106 , for example, or by parts further containing the first clad layer 104 .
- the sides of the columnar portions 311 may be inclined.
- the insulation portions 116 may be provided on the sides of the columnar portions 311 .
- the insulation portions 116 may be positioned in contact with the side surfaces of the columnar portions 311 .
- Current between the electrodes 112 and 114 can flow in the columnar portions 311 sandwiched between the insulation portions 116 while avoiding the insulation portions 116 .
- the insulation portions 116 may have smaller refractive index than that of the active layer 106 . In this case, lights can be efficiently confined within the gain areas 162 and 164 in the plane direction.
- FIG. 12 schematically illustrates the projector 400 .
- FIG. 12 does not show a housing of the projector 400 for easy understanding of the figure.
- the projector 400 containing the light emission device 100 as an example of the invention is herein discussed.
- the projector 400 has a red light source (light emission device) 100 R, a green light source (light emission device) 100 G, and a blue light source (light emission device) 100 B, each of which is constituted by the light emission device 100 according to this embodiment.
- the projector 400 includes transmission type liquid crystal light valves (light modulation devices) 404 R, 404 G, and 404 B for modulating lights emitted from the light sources 100 R, 100 G, and 100 B according to image information, a projection lens (projection device) 408 for expanding images formed by the liquid crystal light valves 404 R, 404 G, and 404 B and projecting the expanded images on a screen (display surface) 410 .
- the projector 400 may further include a cross dichroic prism (color combining unit) 406 for combining the lights received from the liquid crystal light valves 404 R, 404 G, and 404 B and guiding the combined light to the projection lens 408 .
- the projector 400 further includes equalizing systems 402 R, 402 G, and 402 B for equalizing illuminance distributions of lights emitted from the light sources 100 R, 100 G, and 100 B at positions downstream from the respective light sources 100 R, 100 G, and 100 B on the optical path, and applies lights having illuminance distributions equalized by the equalizing systems 402 R, 402 G, and 402 B to the liquid crystal light valves 404 R, 404 G, and 404 B.
- Each of the equalizing systems 402 R, 402 G, and 402 B contains a hologram 402 a and a field lens 402 b , for example.
- the cross dichroic prism 406 is produced by affixing four rectangular prisms, and contains a dielectric multilayer film for reflecting red light and a dielectric multilayer film for reflecting blue light disposed in a cross shape on the inner surface of the prism.
- the three color lights are combined by these dielectric multilayer films to form light representing a color image.
- the combined light is projected on the screen 410 by the projection lens 408 as a projection system such that an expanded image can be displayed on the screen 410 .
- speckle noise can be reduced by the red light source 400 R, the green light source 400 G, and the blue light source 400 B.
- a clear image can be displayed by the projector 400 .
- transmission type liquid crystal light valves are used as the light modulation devices in this example, light valves other than of liquid crystal type, or of reflection type may be employed. Examples of these light valves include reflection type liquid crystal light valves, digital micromirror devices and the like.
- the structure of the projection system may be changed according to the selected types of light valves as necessary.
- the light emission device 100 is applicable to a scanning-type image display apparatus (projector) including a scanning unit as an image forming device which displays images having a desired size on a display surface by applying light from the light emission device 100 to a screen for scanning.
- a scanning-type image display apparatus projector
- a scanning unit as an image forming device which displays images having a desired size on a display surface by applying light from the light emission device 100 to a screen for scanning.
Abstract
A light emission device includes: first and second clad layers sandwiching an active layer; a first electrode connected with the first clad layer; and second electrodes connected with the second clad layer, at least part of the active layer forms gain areas corresponding to the second electrodes, the gain areas extend from a first side to a second side of the active layer while inclined to a vertical of the first side, at least first and second gain areas form a set of gain areas and a plurality of sets are provided, the first and second gain areas in each set are disposed perpendicular to a direction extending from the first side to the second side, the second electrodes above the first gain areas are interconnected by a first common electrode, and the second electrodes above the second gain areas are interconnected by a second common electrode.
Description
- This is a continuation application of U.S. Ser. No. 13/370,638 filed Feb. 10, 2012, which is a continuation application of U.S. Ser. No. 12/792,090 filed Jun. 2, 2010, now U.S. Pat. No. 8,139,618 issued Mar. 20, 2012, which claims priority to Japanese Patent Application No. 2009-144941 filed Jun. 18, 2009, all of which are incorporated by reference herein in their entireties.
- 1. Technical Field
- The present invention relates to a light emission device, a light emission device driving method, and a projector.
- 2. Related Art
- Recently, a laser device capable of emitting laser beams having high luminance and preferable color reproducibility has been expected as a light emission device suited for a light source of a display apparatus such as a projector and a display. According to this laser device, however, speckle noise generated by mutual interference between irregular reflection lights on a screen surface can be a problem in some cases. For overcoming this problem, JP-A-11-64789 proposes a method for reducing speckle noise by moving a screen and varying speckle patterns, for example.
- However, the method disclosed in JP-A-11-64789 introduces other problems such as limitation to the type of screen, the need of a motor for moving the screen and other components, and generation of noise from the motor and the like.
- In addition, for meeting the recent demand for high output, JP-A-4-115585 proposes a method for arraying a light source.
- The method shown in JP-A-4-115585 uses a laser device as a light emission device for the light source. Thus, the problem of speckle noise still arises.
- An advantage of some aspects of the invention is to provide a novel type of arrayed light emission device and driving method of the light emission device capable of reducing speckle noise and increasing output. It is another advantage of some aspects of the invention to provide a projector including the light emission device.
- A light emission device according to a first aspect of the invention includes: a first clad layer; an active layer disposed above the first clad layer; a second clad layer disposed above the active layer; a first electrode electrically connected with the first clad layer; and second electrodes electrically connected with the second clad layer. At least a part of the active layer forms a plurality of gain areas. The plural second electrodes are provided in correspondence with the plural gain areas. The plural gain areas extend from a first side of the active layer to a second side of the active layer opposed to the first side while inclined to a vertical line of the first side in the plan view. At least a first gain area and a second gain area included in the plural gain areas form a set of gain areas. A plurality of the sets of the gain areas are provided. The first gain area and the second gain area included in each set of the gain areas are disposed in this order in a second direction perpendicular to a first direction extending from the first side to the second side in the plan view. The second electrodes disposed above the plural first gain areas are electrically connected with one another by a first common electrode. The second electrode disposed above the plural second gain areas are electrically connected with one another by a second common electrode.
- According to this structure, the light emission device which is arrayed and capable of reducing speckle noise and achieving high output can be provided.
- In the following description of the invention, a term “above” is used in sentences such as “a particular object (hereinafter referred to as B) is provided above another particular object (hereinafter referred to as A)”. According to the description of the invention, this sentence contains both a condition in which the B is provided directly on the A and a condition in which the B is provided above the A with a further object interposed between B and A.
- In addition, in the description of the invention, a phrase “electrically connected” is used in sentences such as “a particular component (hereinafter referred to as D component) is electrically connected with another particular component (hereinafter referred to as C component). According to the description of the invention, this sentence contains both a condition in which the C component and the D component are electrically connected with each other by direct contact and a condition in which the C component and the D component are electrically connected with each other via a further component interposed between the C and D components.
- the light emission device of the first aspect may be configured such that each of the plural sets of the gain areas further includes a third gain area. The first gain area, the second gain area, and the third gain area included in each of the plural sets of the gain areas may be disposed in this order in the second direction in the plan view. The second electrodes disposed above the plural third gain areas may be electrically connected with one another by a third common electrode.
- According to this structure, the light emission device which is arrayed and capable of reducing speckle noise and achieving high output can be provided.
- The light emission device of the first aspect may be configured such that an end surface on the first side and an end surface on the second side do not overlap with each other in each of the plural gain areas in the plan view as viewed from the first side.
- According to this structure, oscillation of laser beams generated in the first gain areas and the second gain areas can be securely reduced or prevented.
- The light emission device of the first aspect may be configured such that the end surface on the first side is shifted from the end surface on the second side in the second direction in each of the plural gain areas. The end surface on the first side in the first gain area may overlap with the end surface on the second side in the second gain area adjacent to the first gain area in the plan view as viewed from the first side.
- According to this structure, each distance between the first gain areas and the second gain areas decreases, and the light emission density increases. Thus, the high-output and compact light emission device can be provided.
- The light emission device of the first aspect may be configured such that the second electrodes contact a contact layer allowing ohmic contact with the second electrodes. Each plane shape of the plural gain areas may be the same as each plane shape of the contact surfaces of the second electrodes in contact with the contact layer.
- According to this structure, the contact resistance of the second electrodes can be reduced by the contact layer.
- The light emission device of the first aspect may be configured such that the first common electrode and the second common electrode are conductive layers. The first common electrode and the second common electrode may extend in the second direction in the plan view.
- According to this structure, the light emission device can be composed of one chip.
- A method for driving the light emission device of the first aspect, the method includes: supplying voltage to the first common electrode such that lights can be emitted from the respective end surfaces in the plural first gain areas; and stopping the supply of voltage to the first common electrode and supplying voltage to the second common electrode such that lights can be emitted from the respective end surfaces in the plural second gain areas.
- According to this light emission device driving method, the light emission device which is arrayed and capable of reducing speckle noise and achieving high output can be driven by the method.
- A projector according to a second aspect of the invention includes: the light emission device according to the first aspect of the invention; a light modulation device which modulates light emitted from the light emission device according to image information; and a projection device which projects an image formed by the light modulation device.
- According to this projector, speckle noise can be reduced, and thus a clear image can be displayed.
- The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
-
FIG. 1 is a plan view schematically showing a light emission device according to an embodiment. -
FIG. 2 is a cross-sectional view schematically illustrating the light emission device according to the embodiment. -
FIG. 3 illustrates an active layer of the light emission device according to the embodiment as viewed from a first side. -
FIG. 4 is a plan view schematically illustrating the light emission device according to the embodiment. -
FIG. 5 is a plan view schematically illustrating the light emission device according to the embodiment. -
FIG. 6 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment. -
FIG. 7 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment. -
FIG. 8 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment. -
FIG. 9 is a cross-sectional view schematically illustrating a manufacturing step of the light emission device according to the embodiment. -
FIG. 10 is a plan view schematically illustrating a light emission device according to a first modified example of the embodiment. -
FIG. 11 is a cross-sectional view schematically illustrating a light emission device according to a second modified example of the embodiment. -
FIG. 12 schematically illustrating a projector according to the embodiment. - A
light emission device 100 according to an embodiment of the invention is now described with reference to the drawings.FIG. 1 is a plan view schematically illustrating thelight emission device 100.FIG. 2 is a cross-sectional view schematically illustrating thelight emission device 100 taken along a line II-II inFIG. 1 .FIG. 1 does not showinsulation portions 116 for easy understanding of the figure. In this embodiment, thelight emission device 100 constituted by a semiconductor light emission device in InGaAlP (red) will be discussed. - As illustrated in
FIGS. 1 and 2 , thelight emission device 100 includes a firstclad layer 104, anactive layer 106, a secondclad layer 108, afirst electrode 112,second electrodes 114, a firstcommon electrode 180, and a secondcommon electrode 182. Thelight emission device 100 can further include asubstrate 102, acontact layer 110, and theinsulation portions 116. - The
substrate 102 is a first conductive type (such as n-type) GaAs substrate, for example. - The first
clad layer 104 is provided on thesubstrate 102. The firstclad layer 104 is an n-type AlGaP layer, for example. Though not shown in the figure, a buffer layer may be formed between thefirst substrate 102 and the firstclad layer 104. The buffer layer is an n-type GaAs layer, an InGaP layer or the like. The buffer layer increases crystallinity of the layers formed above the buffer layer. - The
active layer 106 is provided on the firstclad layer 104. Theactive layer 106 has multiple quantum well (MQW) structure which laminates three layers of quantum well structure constituted by InGaP well layer and InGaAlP barrier layer, for example. Theactive layer 106 has a rectangular parallelepiped shape (including cube shape) or other shapes. As illustrated inFIG. 1 , theactive layer 106 has afirst side 105 and asecond side 107. Thefirst side 105 and thesecond side 107 are opposed to each other. According to the example shown in the figure, thefirst side 105 and thesecond side 107 extend parallel with each other. - A part of the
active layer 106 constitutes a plurality of gain areas. Afirst gain area 162 and asecond gain area 164 included in the plural gain areas constitute each set of gain areas 160 (gain area set 160). That is, each set of the gain area sets 160 has the twogain areas FIG. 10 showing a first modified example described later) with no specific limitation to the number of the gain areas. - As illustrated in the plan view of
FIG. 1 , thegain areas first side 105 to thesecond side 107 while inclined to a vertical line P of thefirst side 105. This arrangement reduces or prevents oscillation of laser beams generated in thegain areas first gain areas 162 and thesecond gain areas 164 are inclined to the vertical line P at the same angle. It is therefore considered that thefirst gain areas 162 and thesecond gain areas 164 extend parallel with one another. Each shape of thegain areas - Each of the
first gain areas 162 has afirst end surface 170 disposed on thefirst side 105, and asecond end surface 172 disposed on thesecond side 107. According to the example shown in the figure, thefirst end surface 170 is shifted from thesecond end surface 172 in a second direction (+Y direction) perpendicular to a first direction (+X direction) extending from thefirst side 105 to thesecond side 107. The end surfaces 170 and 172 can be provided as emission slopes for emitting lights generated in thefirst gain areas 162. Each of thesecond gain areas 164 has athird end surface 174 disposed on thefirst side 105, and afourth end surface 176 disposed on thesecond side 107. According to the example shown in the figure, thethird end surface 174 is shifted from thefourth end surface 176 in the second direction. The end surfaces 174 and 176 can be provided as emission slopes for emitting lights generated in thesecond gain areas 164. In this case, it is preferable that each reflectance of thesides gain areas sides sides first side 105. Moreover, though not shown in the figure, emission of lights can be made allowed only from either thefirst end surface 170 or thesecond end surface 172 of each of thefirst gain areas 162, for example, by providing reflection film (total reflection film or dielectric multilayer film mirror) on either thefirst side 105 or thesecond side 107. - The gain area sets 160 are plural sets of gain areas disposed in the second direction (+Y direction). The example shown in the figure includes three sets of the gain area sets 160, but the number of sets of the gain area sets 160 is not specifically limited. The
first gain area 162 and thesecond gain area 164 included in each set of the gain area sets 160 are disposed in this order in the second direction. It is thus considered that thefirst gain area 162 and thesecond gain area 164 are alternately disposed. -
FIG. 3 is a plan view illustrating theactive layer 106 as viewed from thefirst side 105. As illustrated inFIG. 3 , thefirst end surface 170 and thesecond end surface 172 do not overlap with each other in thefirst gain area 162. Similarly, thethird end surface 174 and thefourth end surface 176 do not overlap with each other in thesecond gain area 164. According to this arrangement, direct multiple reflection of lights generated in thefirst gain area 162 does not occur between thefirst end surface 170 and thesecond end surface 172. Similarly, direct multiple reflection of lights generated in thesecond gain area 164 does not occur between thethird end surface 174 and thefourth end surface 176. As a result, direct resonator is not formed, and thus oscillation of laser beams generated in thegain areas first end surface 170 and thesecond end surface 172 in thefirst gain area 162, for example, may have any length as long as the length has a positive value as illustrated inFIG. 3 . - Though not shown in
FIG. 3 , thefirst end surface 170 of one of the two adjoining first gain areas 162 (the adjoiningfirst gain areas 162 with thesecond gain area 164 interposed therebetween) does not overlap with thesecond end surface 172 of the otherfirst gain area 162 in the plan view as viewed from the first side 105 (seeFIG. 1 ). Similarly, thethird end surface 174 of one of the two adjoiningsecond gain areas 164 does not overlap with thefourth end surface 176 of the othersecond gain area 164. When thefirst end surface 170 of the onefirst gain area 162 overlaps with thesecond end surface 172 of the otherfirst gain area 162, there is a possibility that direct multiple reflection occurs even between the end surfaces of the different types of the gain areas depending on the efficiency of confinement of the gain areas. However, in case of the arrangement of the end surfaces in this embodiment, direct multiple reflection does not occur, and thus oscillation of laser beams generated in thegain areas - On the other hand, the
first end surface 170 of thefirst gain area 162 can overlap with thefourth end surface 176 of thesecond gain area 164 in the plan view as viewed from thefirst side 105 as illustrated inFIG. 3 . According to this arrangement, the distance between thefirst gain area 162 and thesecond gain area 164 decreases, and thus light emission density increases. As will be described later, thefirst gain area 162 and thesecond gain area 164 alternately emit lights. Thus, direct multiple reflection does not occur between the end surfaces 170 and 176 even when the end surfaces 170 and 176 overlap with each other. - As illustrated in
FIG. 2 , the secondclad layer 108 is provided on theactive layer 106. The secondclad layer 108 is a second conductive type (such as p-type) AlGaP layer or the like. - For example, the p-type second clad
layer 108, theactive layer 106 not doped, and the n-type first cladlayer 104 constitute a pin diode. Each of the firstclad layer 104 and the secondclad layer 108 has a larger band gap width and a smaller refractive index than those of theactive layer 106. Theactive layer 106 has a function of amplifying light. The firstclad layer 104 and the secondclad layer 108 between which theactive layer 106 is sandwiched have a function of confining injection carriers (electrons and positive holes) and light. - When forward bias voltage of a pin diode is applied between the
first electrode 112 and thesecond electrodes 114 by thelight emission device 100, the electrons and positive holes are re-combined in thegain areas active layer 106. This re-combination causes light emission, and induced stimulated emission which occurs from the start point corresponding to the light emission position in a manner of chain reaction. As a result, the light intensity is amplified in thegain areas first gain areas 162 is amplified within thefirst gain areas 162, and emitted through the first end surfaces 170 or the second end surfaces 172. Similarly, a part of lights generated in thesecond gain area 164 is amplified within thesecond gain areas 164, and emitted through the third end surfaces 174 or the fourth end surfaces 176. It is thus considered that thegain areas - The
contact layer 110 is provided on the secondclad layer 108. Thecontact layer 110 is constituted by a layer allowing ohmic contact with thesecond electrodes 114, for example. Thecontact layer 110 reduces contact resistance of thesecond electrodes 114. Thecontact layer 110 is a p-type GaAs layer, for example. - The
first electrode 112 is formed on the entire area of the lower surface of thesubstrate 102. Thefirst electrode 112 can contact the layer allowing ohmic contact with the first electrode 112 (thesubstrate 102 in the example shown in the figure). Thefirst electrode 112 is electrically connected with the firstclad layer 104 via thesubstrate 102. Thefirst electrode 112 is one of the electrodes for driving thelight emission device 100. Thefirst electrode 112 is produced by laminating a Cr layer, an AuGe layer, an Ni layer, and an Au layer in this order from thesubstrate 102, for example. A second contact layer (not shown) may be formed between the firstclad layer 104 and thesubstrate 102 and exposed by dry-etching or other method. In this case, thefirst electrode 112 is disposed on the second contact layer. By this method, single-sided electrode structure can be formed. This structure is particularly effective when thesubstrate 102 has insulation characteristics. - The
second electrodes 114 are disposed on thecontact layer 110. The pluralsecond electrodes 114 are provided in correspondence with theplural gain areas second electrodes 114 contacting thecontact layer 110 have plane shapes similar to those of thegain areas electrodes second electrodes 114, for example, and the plane shapes of thegain areas second electrodes 114 are electrically connected with the secondclad layer 108 via thecontact layer 110. Thesecond electrodes 114 correspond to the other electrode for driving thelight emission device 100. Thesecond electrodes 114 are produced by laminating a Cr layer, an AuZn layer, and an Au layer in this order from thecontact layer 110, for example. - As illustrated in
FIG. 2 , theinsulation portions 116 are disposed on thecontact layer 110 and between the pluralsecond electrodes 114. It is thus considered that theinsulation portions 116 contact thecontact layer 110 positioned above theactive layer 106 not having thegain areas insulation portions 116 is an SiN layer, an SiO2 layer, or a polyimide layer, for example. - The first
common electrode 180 and the secondcommon electrode 182 are formed above thesecond electrodes 114. The firstcommon electrode 180 electrically connects thesecond electrodes 114 disposed above the pluralfirst gain areas 162. According to the example shown inFIG. 2 , contact holes 190 are formed on theinsulation portions 116 positioned above thefirst gain areas 162, and the firstcommon electrode 180 and thesecond electrodes 114 are connected by the contact holes 190 filled with the firstcommon electrode 180. Similarly, the secondcommon electrode 182 electrically connects thesecond electrodes 114 disposed above the pluralsecond gain areas 164. It is thus considered that theinsulation portions 116 are provided above thesecond electrodes 114 in the areas other than the contact holes 190. As illustrated inFIG. 1 , thecommon electrodes common electrodes gain areas 162 and 164 (the second electrodes 114). Thecommon electrodes second electrodes 114 may be electrically connected with one another by wire bonding. - A driving method of the
light emission device 100 is now explained.FIGS. 4 and 5 illustrate the driving method of thelight emission device 100. - Initially, as illustrated in
FIG. 4 , voltage is supplied from an external power source (not shown) to the firstcommon electrode 180. As a result, lights 10 are emitted from the respective end surfaces 170 and 172 of the pluralfirst gain areas 162. - Then, as illustrated in
FIG. 5 , voltage supply to the firstcommon electrode 180 is cut off to stop light emission from the end surfaces 170 and 172 of thefirst gain areas 162. Subsequently, voltage is supplied to the secondcommon electrode 182. As a result, lights 20 are emitted from the respective end surfaces 174 and 176 of the pluralsecond gain areas 164. - These steps are repeated to alternately apply the
lights - While the
light emission device 100 in InGaAlP has been described in this embodiment, thelight emission device 100 may be constituted by materials in various systems capable of forming light emission gain areas. Incase of semiconductor material, semiconductor in AlGaN, InGaN, GaAs, AlGaAs, InGaAs, InGaAsP, ZnCdSe, or in others may be employed. - The
light emission device 100 according to this embodiment is applicable to a light source for a projector, a display, an illumination device, a measuring device and the like. - The
light emission device 100 in this embodiment has the following characteristics, for example. - According to the
light emission device 100, thegain areas first side 105 to thesecond side 107 while inclined to the vertical line P as described above. Moreover, the end surfaces 170 and 174 on thefirst side 105 do not overlap with the end surfaces 172 and 176 on thesecond side 107 in thegain areas first side 105. Accordingly, oscillation of laser beams generated in thegain areas gain areas gain areas light emission device 100 than by a typical LED (light emitting diode) in related art. Accordingly, the light emission device provided in this embodiment is a novel light emission device capable of reducing speckle noise and achieving high output. - According to the
light emission device 100, thefirst end surface 170 of thefirst gain area 162 and thefourth end surface 176 of thesecond gain area 164 adjacent to thefirst gain area 162 overlap with each other in the plan view as viewed from thefirst side 105. In this case, the distance between thefirst gain area 162 and thesecond gain area 164 decreases, and the light emission density increases. Thus, thelight emission device 100 becomes a high-output and compact device. In addition, lights are alternately emitted from thefirst gain areas 162 and thesecond gain areas 164 as explained above. Accordingly, direct multiple reflection does not occur between the first end surfaces 170 and the fourth end surfaces 176 even when both thesurfaces - According to the
light emission device 100, lights are alternately emitted from thefirst gain areas 162 and thesecond gain areas 164. Thus, thermal interference between the adjoininggain areas light emission device 100. - According to the
light emission device 100, the pluralsecond electrodes 114 can be electrically connected with one another by thecommon electrodes light emission device 100 can be composed of one chip. When constitution by one chip is difficult, the plural second electrodes can be electrically connected by wire bonding, for example. - The manufacturing method of the
light emission device 100 according to this embodiment is now described with reference to the drawings.FIGS. 6 through 9 are cross-sectional views schematically illustrating respective steps for manufacturing thelight emission device 100. - As illustrated in
FIG. 6 , epitaxial growths of the firstclad layer 104, theactive layer 106, the secondclad layer 108, and thecontact layer 110 are allowed on thesubstrate 102 in this order. For epitaxial growths, MOCVD (metal organic chemical vapor deposition) method, MBE (molecular beam epitaxy) method or the like is used. - As illustrated in
FIG. 7 ,first parts 116 a of theinsulation portions 116 are formed on thecontact layer 110. More specifically, thefirst parts 116 a are produced by forming an insulation layer (not shown) on the entire area and patterning the insulation layer. Thecontact layer 110 is exposed by the patterning. The insulation layer is formed by CVD (chemical vapor deposition) method, coating method or other method. The patterning is performed by photolithography, etching or other technology. - As illustrated in
FIG. 8 , the pluralsecond electrodes 114 are formed on the exposed areas of the contact layer 110 (i.e., on the areas of thecontact layer 110 not having thefirst portions 116 a). Thesecond electrodes 114 are produced by vacuum deposition method or the like. - As illustrated in
FIG. 9 ,second parts 116 b of theinsulation portions 116 and the contact holes 190 are produced by providing an insulation layer (not shown) on the entire area and patterning the insulation layer. The contact holes 190 are formed in such a manner that thesecond electrodes 114 can be exposed through the contact holes 190. - Then, the
common electrodes FIGS. 1 and 2 . Thecommon electrodes common electrode 180 is so constructed as to connect the pluralsecond electrodes 114 positioned above thefirst gain areas 162 with one another. The secondcommon electrode 182 is so constructed as to connect the pluralsecond electrodes 114 positioned above thesecond gain areas 164 with one another. Then, thefirst electrode 112 is formed on the lower surface of thesubstrate 102. Thefirst electrode 112 is produced by vacuum deposition method, for example. Thefirst electrode 112 may be formed before thesecond electrodes 114 are produced. - Manufacture of the
light emission device 100 is now completed by these steps. - According to the manufacturing method of the
light emission device 100, thelight emission device 100 capable of reducing speckle noise and providing high output can be produced. -
Light emission devices light emission devices light emission device 100 in this embodiment, and the same detailed explanation is not repeated. - (1) The
light emission device 200 in a first modified example is initially explained.FIG. 10 is a plan view schematically illustrating thelight emission device 200 in correspondence withFIG. 1 .FIG. 10 does not show theinsulation portions 116 for easy understanding of the figure. - As illustrated in
FIG. 10 , each set of the gain area sets 160 of thelight emission device 200 has thefirst gain area 162, thesecond gain area 164, and athird gain area 266. Thefirst gain area 162, thesecond gain area 164, and thethird gain area 266 included in each set of the plural gain area sets 160 are disposed in this order in the second direction (+Y direction) in the plan view. The shape, function and the like of thethird gain area 266 are similar to those of thefirst gain area 162 and thesecond gain area 164 described above. - The
second electrodes 114 provided above the pluralthird gain areas 266 are electrically connected with one another by a thirdcommon electrode 284. According to the example shown in the figure, the thirdcommon electrode 284 is disposed between the firstcommon electrode 180 and the secondcommon electrode 182. However, the firstcommon electrode 180, the secondcommon electrode 182, and the thirdcommon electrode 284 may be positioned in this order in the first direction (+X direction), for example. The shape, function and the like of the thirdcommon electrode 284 are similar to those of the firstcommon electrode 180 and the secondcommon electrode 182 described above. - According to the
light emission device 200 having thethird gain areas 266, the distance between the adjoiningfirst gain areas 162, for example, becomes longer than that of thelight emission device 100. Thus, the effect of thermal interference can be further prevented or reduced. - (2) The
light emission device 300 in a second modified example is now explained.FIG. 11 is a cross-sectional view schematically illustrating thelight emission device 300 in correspondence withFIG. 2 . - The
light emission device 100 is an example of a so-called gain waveguide type. However, thelight emission device 300 is of a so-called refractive index waveguide type. - According to the
light emission device 300,columnar portions 311 are constituted by thecontact layer 110 and a part of the secondclad layer 108 as illustrated inFIG. 11 . The plane shapes of thecolumnar portions 311 are the same as those of thegain areas electrodes columnar portions 311, for example, and the plane shapes of thegain areas columnar portions 311 may be formed by parts containing thecontact layer 110, the secondclad layer 108, and theactive layer 106, for example, or by parts further containing the firstclad layer 104. In addition, the sides of thecolumnar portions 311 may be inclined. - The
insulation portions 116 may be provided on the sides of thecolumnar portions 311. Theinsulation portions 116 may be positioned in contact with the side surfaces of thecolumnar portions 311. Current between theelectrodes columnar portions 311 sandwiched between theinsulation portions 116 while avoiding theinsulation portions 116. Theinsulation portions 116 may have smaller refractive index than that of theactive layer 106. In this case, lights can be efficiently confined within thegain areas - A
projector 400 according to this embodiment is now described.FIG. 12 schematically illustrates theprojector 400.FIG. 12 does not show a housing of theprojector 400 for easy understanding of the figure. Theprojector 400 containing thelight emission device 100 as an example of the invention is herein discussed. - The
projector 400 has a red light source (light emission device) 100R, a green light source (light emission device) 100G, and a blue light source (light emission device) 100B, each of which is constituted by thelight emission device 100 according to this embodiment. - The
projector 400 includes transmission type liquid crystal light valves (light modulation devices) 404R, 404G, and 404B for modulating lights emitted from thelight sources light valves projector 400 may further include a cross dichroic prism (color combining unit) 406 for combining the lights received from the liquid crystallight valves projection lens 408. - The
projector 400 further includes equalizingsystems light sources light sources systems light valves systems hologram 402 a and afield lens 402 b, for example. - Three color lights modulated by the respective liquid crystal
light valves dichroic prism 406. This prism is produced by affixing four rectangular prisms, and contains a dielectric multilayer film for reflecting red light and a dielectric multilayer film for reflecting blue light disposed in a cross shape on the inner surface of the prism. The three color lights are combined by these dielectric multilayer films to form light representing a color image. Then, the combined light is projected on thescreen 410 by theprojection lens 408 as a projection system such that an expanded image can be displayed on thescreen 410. - According to the
projector 400, speckle noise can be reduced by the red light source 400R, the green light source 400G, and the blue light source 400B. Thus, a clear image can be displayed by theprojector 400. - While the transmission type liquid crystal light valves are used as the light modulation devices in this example, light valves other than of liquid crystal type, or of reflection type may be employed. Examples of these light valves include reflection type liquid crystal light valves, digital micromirror devices and the like. The structure of the projection system may be changed according to the selected types of light valves as necessary.
- Moreover, the
light emission device 100 is applicable to a scanning-type image display apparatus (projector) including a scanning unit as an image forming device which displays images having a desired size on a display surface by applying light from thelight emission device 100 to a screen for scanning. - The invention is not limited to the embodiment and the modified examples described herein only as examples. Thus, the embodiment and the modified examples can be combined, for example, for practicing the invention.
- While the specific embodiment according to the invention has been described and depicted in detail, it is easily understood for those skilled in the art that various modifications and changes can be made without departing from the substantial scope of the invention for providing the novel points and advantages. As such, all modified examples of the embodiment are included in the scope of the invention.
Claims (4)
1. A light emission device comprising:
an active layer including a first gain area and a second gain area; and
an electrode disposed on the active layer;
wherein the first gain area and the second gain area extend from one side of the active layer at an angle relative to a normal of the one side in plan view, and
the first gain area and the second gain area alternately emit light by sending current to the electrode.
2. The light emission device according to claim 1 , wherein:
the first gain area and the second gain area are disposed adjacent to one another.
3. A projector comprising:
the light emission device according to claim 1 ;
a light modulation device which modulates light emitted from the light emission device according to image information; and
a projection device which projects an image formed by the light modulation device.
4. The light emission device according to claim 1 , wherein the first gain area and the second gain area are provided in pluralities and the first and second gain areas are alternately disposed in the active layer.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US13/644,663 US20130027443A1 (en) | 2009-06-18 | 2012-10-04 | Light emission device, light emission device driving method, and projector |
Applications Claiming Priority (5)
Application Number | Priority Date | Filing Date | Title |
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JP2009-144941 | 2009-06-18 | ||
JP2009144941A JP5447799B2 (en) | 2009-06-18 | 2009-06-18 | Light emitting device, driving method thereof, and projector |
US12/792,090 US8139618B2 (en) | 2009-06-18 | 2010-06-02 | Light emission device, light emission device driving method, and projector |
US13/370,638 US8304786B2 (en) | 2009-06-18 | 2012-02-10 | Light emission device, light emission device driving method, and projector |
US13/644,663 US20130027443A1 (en) | 2009-06-18 | 2012-10-04 | Light emission device, light emission device driving method, and projector |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US13/370,638 Continuation US8304786B2 (en) | 2009-06-18 | 2012-02-10 | Light emission device, light emission device driving method, and projector |
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US20130027443A1 true US20130027443A1 (en) | 2013-01-31 |
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ID=43354343
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US12/792,090 Expired - Fee Related US8139618B2 (en) | 2009-06-18 | 2010-06-02 | Light emission device, light emission device driving method, and projector |
US13/370,638 Expired - Fee Related US8304786B2 (en) | 2009-06-18 | 2012-02-10 | Light emission device, light emission device driving method, and projector |
US13/644,663 Abandoned US20130027443A1 (en) | 2009-06-18 | 2012-10-04 | Light emission device, light emission device driving method, and projector |
Family Applications Before (2)
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US12/792,090 Expired - Fee Related US8139618B2 (en) | 2009-06-18 | 2010-06-02 | Light emission device, light emission device driving method, and projector |
US13/370,638 Expired - Fee Related US8304786B2 (en) | 2009-06-18 | 2012-02-10 | Light emission device, light emission device driving method, and projector |
Country Status (2)
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US (3) | US8139618B2 (en) |
JP (1) | JP5447799B2 (en) |
Families Citing this family (2)
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JP5447799B2 (en) * | 2009-06-18 | 2014-03-19 | セイコーエプソン株式会社 | Light emitting device, driving method thereof, and projector |
JP2014132302A (en) * | 2013-01-07 | 2014-07-17 | Seiko Epson Corp | Illumination device and projector |
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Also Published As
Publication number | Publication date |
---|---|
US20100322273A1 (en) | 2010-12-23 |
US8139618B2 (en) | 2012-03-20 |
JP2011003686A (en) | 2011-01-06 |
US20120140190A1 (en) | 2012-06-07 |
JP5447799B2 (en) | 2014-03-19 |
US8304786B2 (en) | 2012-11-06 |
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