Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133602—Direct backlight
  • G02F1/133603—Direct backlight with LEDs
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
  • G02B26/02—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the intensity of light
• • G—PHYSICS
  • G02—OPTICS
  • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
  • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
  • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
  • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
  • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
  • G02F1/1333—Constructional arrangements; Manufacturing methods
  • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
  • G02F1/1336—Illuminating devices
  • G02F1/133617—Illumination with ultraviolet light; Luminescent elements or materials associated to the cell
• • 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
  • H01S5/041—Optical pumping
• • 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
  • H01S5/18—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
  • H01S5/183—Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities having only vertical cavities, e.g. vertical cavity surface-emitting lasers [VCSEL]

Definitions

• the present invention relates to a display device for producing colored light which uses a vertical cavity laser array.
• Optic axis herein refers to the direction in which propagating light does not see birefringence.
• Polarizer and analyzer herein refer to elements that polarize electromagnetic waves. However, the one closer to the source of the light will be called a polarizer while the one closer to the viewer will be called an analyzer.
• Polarizing elements herein refers to both the polarizer and analyzer.
• Azimuthal angle ⁇ and tilt angle ⁇ are herein used to specify the direction of an optic axis.
• the azimuthal angle ⁇ is used, as their tilt angle ⁇ is zero.
• FIG. 1 shows the definition of the azimuthal angle ⁇ and tilt angle ⁇ to specify the direction of the optic axis 1 with respect to the x-y-z coordinate system 3.
• the x-y plane is parallel to the display surface 5, and the z-axis is parallel to the display normal direction 7.
• the azimuthal angle ⁇ is the angle between the y-axis and the projection of the optic axis 9 onto the x-y plane.
• the tilt angle ⁇ is the angle between the optic axis 1 and the x-y plane.
• LCD liquid crystal display
• a liquid crystal cell is placed between a pair of polarizers. Light that enters the display is polarized by the initial polarizer. As the light passes through the liquid crystal cell, the molecular orientation of the liquid crystal material affects the polarized light such that it either passes through the analyzer or it is blocked by the analyzer. The orientation of the liquid crystal molecules can be altered by applying a voltage across the cell, thus enabling varying amounts of light intensity to pass through the LCD pixels. By employing this principle, minimal energy is required to switch the LCD.
• the typical liquid crystal cell contains a color filter array (CFA) comprised of red, green, and blue transmitting pixels.
• CFA color filter array
• BLU backlight unit
• FWHM full-width at half maximum
• a transmissive LCD is illuminated by a backlight unit, including a light source, light guide plate (LGP), reflector, diffuser, collimating films, and a reflective polarizer.
• the reflective polarizer is used to recycle and reflect light of the undesired polarization. However, not all of the light of the undesired polarization is recycled and not all of the recycled light exits the BLU with the correct polarization state.
• LCDs are quickly replacing CRTs and other types of electronic displays for computer monitors, televisions, and other office and household displays.
• LCD's suffer from poor contrast ratios at larger viewing angles. Unless the contrast ratio is improved at large viewing angles, the penetration of LCDs into certain markets will be limited. The poor contrast ratio is typically due to increased brightness of the display's dark state. LCDs are optimized such that the display has the highest contrast ratio within a narrow viewing cone centered on axis (at zero degrees viewing angle).
• PL-LCD photoluminescent
• This display employs a backlight unit of narrow band frequency, a liquid crystal modulator, and a photoluminescent output screen for producing color.
• the PL-LCD light source utilizes wavelengths that are in the UV, which would accelerate the breakdown of the liquid crystal materials.
• the PL-LCD light source is much less efficient than the standard cold cathode fluorescent lamps (CCFLs) used in typical LCD displays. In general, it would be beneficial to produce a display that did not suffer from the problems associated with typical LCD displays.
• OLED displays overcome some of these disadvantages, however, they currently suffer from short lifetimes and higher manufacturing costs. Part of the higher manufacturing cost is inherent in the OLED design, such as the need to pixelate the OLED emitter region and the greater complexity of thin film transistors (TFTs) for current driven devices.
• TFTs thin film transistors
• a display apparatus for producing colored pixelated light comprising: a) a backlight unit for producing pump-beam light; b) a vertical cavity laser array device including: i) a structure for modulating the properties of the device at spaced locations so as to provide an array of spaced laser pixels which have higher net gain than the interpixel regions; and ii) an active region which includes portions for producing different colored light in response to the pump-beam light; c) a light shutter; and d) a beam expander disposed over the light shutter for increasing the angular cone of view of the selected colored light.
• ADVANTAGES It is an advantage of the present invention to use a pixelated two- dimensional vertical cavity surface emitting laser (VCSEL) array as the light source for a liquid crystal display.
• VCSEL vertical cavity surface emitting laser
• Each color element contains thousands of micron-sized laser pixels, which are mutually incoherent. This leads to each color element producing multimode laser light.
• the pixel size being 3 to 5 microns in diameter
• the divergence angle of the multimode laser light is on the order of 3-5°. This small divergence angle enables a 1 :1 correspondence between the laser's color elements and the liquid crystal display's color elements.
• the liquid crystal viewing angle compensation films can be removed from the display structure.
• the multimode laser light output from the two-dimensional vertical cavity laser array can be polarized preferentially along one direction.
• the bottom polarizer element and its associated reflective polarizer element can be deleted as elements of the LCD display.
• FIG. 1 shows a perspective which is useful in understanding the definition of the tilt and azimuthal angles to specify a direction of an optic axis
• FIG. 2 shows a side cross sectional schematic of an optically pumped two-dimensional VCSEL array device
• FIG. 3 shows a top view of a two-dimensional VCSEL array device containing red, green, and blue emitting elements in which each element is composed of thousands of micron-sized laser pixels
• FIG. 4 shows a side view of another embodiment of an optically pumped two-dimensional VCSEL array device which includes absorbing elements
• FIG. 5 shows a side cross sectional view of another embodiment of an optically pumped two-dimensional VCSEL array device which includes dyed photoresist absorbing elements
• FIG. 6 shows a side cross sectional view of another embodiment of an optically pumped two-dimensional VCSEL array device which includes planarized absorbing elements
• FIG. 7 shows a side cross sectional view of another embodiment of an optically pumped two-dimensional VCSEL array device which includes an etched dielectric stack
• FIG. 8 shows a side cross sectional view of another embodiment of an optically pumped two-dimensional VCSEL array device which includes an etched dielectric stack that has been planarized
• FIG. 9 is a simplified schematic of the display device containing the VCSEL array device
• FIG. 10 is a simplified schematic of a linear LED-array driven backlight unit pumping the VCSEL array device
• FIG. 11 is a simplified schematic of a planar LED-array driven backlight unit pumping the VCSEL array device
• FIG. 12 is a simplified schematic of a cold cathode fluorescent lamp driven backlight unit pumping the VCSEL array device
• FIG. 13 is simplified schematic of another embodiment of a cold cathode fluorescent lamp driven backlight unit pumping the VCSEL array device
• FIG. 14 is a simplified schematic of the liquid crystal cell and its components, including the analyzer.
• DETAILED DESCRIPTION OF THE INVENTION The invention is enabled by a light source that produces light output which is both nearly collimated and single wavelength. In addition, the light source must contain red, green, and blue emitting elements from a common substrate whose size is on the scale of 80 x 240 ⁇ m.
• FIG. 3 shows a top view of the two-dimensional VCSEL array device 100 where on the surface of the VCSEL needs to be defined red, green, and blue (RGB) emitting elements 205 which are composed of thousands of micron-sized laser pixels 200 separated by interpixel regions 210.
• RGB red, green, and blue
• an active region 130 be composed of organic-based gain media.
• ZnO nanoparticles (with preferred diameters less than 10 nm) either undoped or doped with impurities, such as, Mn 2+ or Eu 2+ .
• impurities such as, Mn 2+ or Eu 2+ .
• the laser pixels 200 need to be the same size and positioned in a periodic array. However, having single mode laser output from each emitting element 205 would result in speckle, which is not desirable for display applications.
• the individual laser pixels 200 be incoherent amongst themselves so as to result in multimode laser output from each emitting element 205. Even though the laser pixels 200 do not exchange intensity and phase information between themselves, in order to obtain nearly collimated and single wavelength output from each emitting element 205, each laser pixel needs to produce single mode output. As a result, the preferred diameter of the laser pixels 200 is in the range of 2.5 to 4.5 ⁇ m, where smaller diameters result in increased scattering loss and larger diameters result in unwanted higher-order transverse modes.
• the generalized methodology for producing a two-dimensional array of laser pixels is to modulate the net gain of the VCSEL device.
• This modulation of the net gain can be obtained by a number of ways, such as selectively spoiling the emissive properties of the gain media in the active region 130, selectively pumping the gain media in the active region 130, and selectively etching one of the dielectric mirrors (stacks).
• a straightforward way to spoil the emissive properties of an organic-based gain media is to expose it to high levels of UV radiation.
• an absorbing layer can be selectively deposited below the active region 130 (in the area underneath the interpixel regions 210) such that it absorbs a pump- beam light 180 prior to it entering the active region 130.
• the interpixel regions 210 are defined by where the net gain is lowered (through either spoiling the emissive properties or by absorbing the pump-beam light 180), while the two-dimensional array of laser pixels 200 corresponds to the regions where the net gain is unmodified.
• the modulation is obtained by performing a two-dimensional etch of one of the dielectric stacks, such that, the interpixel regions 210 correspond to the etched areas (lower overall reflectance at the lasing wavelength) of the dielectric stack, whereas the unetched areas (higher overall reflectance at the lasing wavelength) correspond to the laser pixels 200.
• the size of the laser pixels 200 can be randomly varied from site to site, as well as placing the pixels on a randomly-arranged two-dimensional array.
• the substrate 110 should be light transmissive.
• the substrate 110 can be transparent glass or plastic.
• the bottom dielectric stack 120 which is composed of alternating high and low refractive index dielectric materials.
• the bottom dielectric stack 120 is designed to be reflective to laser light over a predetermined range of wavelengths. Typical high and low refractive index materials are TiO 2 and SiO 2 , respectively.
• the bottom dielectric stack 120 can be deposited by plasma-enhanced chemical vapor deposition, electron-beam (e-beam) deposition, or sputtering. Additional methodologies are polymeric extrusion, and sol-gel and colloidal depositions, as commonly practiced in the art. As is well known in the art, the light output from VCSEL devices typically does not have a preferred orientation and can vary as a function of light intensity. Ways for fixing the polarization can be broken into two groups: 1) have the oscillator strength of the lasing transition be different for the transverse electric (TE) and transverse magnetic (TM) polarizations; and 2) have the dielectric stack reflectance be different for the two polarizations.
• TE transverse electric
• TM transverse magnetic
• the first approach is difficult to implement for gain media comprised of amorphous organic compounds.
• the reflectance of either the top or bottom dielectric stacks is modified in order to make it birefringent. It has been shown for inorganic VCSEL devices that a 4% difference in the threshold modal gains between the TE and TM polarizations will result in greater than a 100:1 polarization mode suppression ratio (PMSR), Y. Ju, et al., Appl. Phys. Lett. 71, 741 (1997).
• PMSR polarization mode suppression ratio
• the simplest route to enable this modal difference for amorphous organic laser systems is to replace one of the layers of the dielectric stack (preferably the stack with the lower peak reflectance) with a birefringent layer 126.
• these birefringent layers can have the index of refraction in the two polarization directions differing by as much as 0.25, with a 0.16 index difference being more common. It is simple to calculate using standard transfer matrix techniques that the modal difference between the two polarizations will be on the order of 22% if one of the stack layers (whose peak reflectance is on the order of 99%) is replaced by the birefringent layer 126, for which the index difference is 0.16. Since this modal difference is far greater than the one measured by Y.
• the resulting PMSR should be much larger than 100:1.
• the VCSEL array device 100 is described with reference to including a birefringent layer 126 in order to polarize the laser light 190, as is well known in the art, Y. Ju, et al., Appl. Phys. Lett. 71, 741 (1997), other ways can be employed to polarize the laser light 190 from the VCSEL array device 100.
• the birefringent layer 126 shown in FIG. 2, includes an alignment layer 128 and a birefringent material 129, and is deposited over the bottom dielectric stack 120.
• the birefringent layer 126 can also be disposed between the active region 130 and a top dielectric stack 140.
• the birefringent layer 126 can also be disposed within one of the dielectric stacks.
• the alignment layer 128 can be oriented by the following techniques.
• the alignment layer contains a photo- orientable or photo-alignable material and can be oriented by a photo-alignment technique.
• Photo-orientable materials include, for example, photo-isomerization polymers, photo-dimerization polymers, and photo-decomposition polymers.
• the photo-orientable materials are cinnamic acid derivatives as disclosed in U.S. Patent 6,160,597.
• Such materials can be oriented and simultaneously crosslinked by irradiation with linearly polarized UV light.
• the alignment layer can also be oriented by mechanical rubbing, which is well known in the art.
• the photo-alignment process can be accomplished by using an apparatus as described in commonly assigned U.S. Patent Application Publication 2004/0008310 Al, the disclosure of which is herein incorporated by reference.
• the birefringent material 129 is typically a liquid crystalline monomer when it is first disposed on the alignment layer 128, and is crosslinked by UV irradiation, or polymerized by other ways such as heat.
• the birefringent material 129 can be a positive dielectric material, whose optic axis 1 has an average tilt angle between 0° and 20°.
• the birefringent material 129 can also be a negative dielectric material, whose optic axis 1 has an average tilt angle between 0° and 20°.
• the birefringent material 129 is comprised of diacrylate or diepoxide with positive birefringence as disclosed in U.S. Patent 6,160,597 (Schadt, et al.) and U.S. Patent 5,602,661 (Schadt, et al.).
• the optic axis 1 in the birefringent material 129 is usually untilted relative to the layer plane, and is uniform across the thickness direction.
• the active region 130 is deposited over the bottom dielectric stack 120 or birefringent layer 126, when it is included in the device.
• the active region 130 is not a bulk layer but a multilayer composite.
• the active region 130 contains one or more periodic gain regions 160, which are separated by spacer layers 170.
• the thickness of the periodic gain regions 160 is typically less than 50 nm, with a preferred thickness of 5 to 30 nm.
• the thicknesses of the spacer layers 170 are chosen such that the periodic gain region(s) is aligned with the antinodes of the laser cavity's standing electromagnetic field (e-field).
• Employing periodic gain region(s) 160 in the active region 130 results in larger power conversion efficiencies and a large reduction in the unwanted spontaneous emission.
• the active region 130 includes one or more periodic gain regions 160 and spacer layers 170 disposed on either side of the periodic gain region(s) and arranged so that the periodic gain region(s) is aligned with the antinodes of the device's standing wave electromagnetic field.
• the periodic gain region(s) 160 is composed of either small- molecular weight organic material, polymeric organic material, or inorganic-based nanoparticles, which fluoresce with a high quantum efficiency.
• the small- molecular weight organic material is typically deposited by high-vacuum (10 ⁇ 6 Torr) thermal evaporation, while the conjugated polymers and inorganic nanoparticles are usually formed by spin casting.
• substituted or “substituent” means any group or atom other than hydrogen.
• group when the term “group” is used, it is meant that when a substituent group contains a substitutable hydrogen, it is also intended to encompass not only the substituent's unsubstituted form, but also its form further substituted with any substituent group or groups as herein mentioned, so long as the substituent does not destroy properties necessary for device utility.
• a substituent group can be halogen or can be bonded to the remainder of the molecule by an atom of carbon, silicon, oxygen, nitrogen, phosphorous, sulfur, selenium, or boron.
• the substituent can be, for example, halogen, such as chloro, bromo or fluoro; nitro; hydroxyl; cyano; carboxyl; or groups which can be further substituted, such as alkyl, including straight or branched chain or cyclic alkyl, such as methyl, trifluoromethyl, ethyl, t-butyl, 3-(2,4-di-t-pentylphenoxy) propyl, and tetradecyl; alkenyl, such as ethyl ene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy, 2-methoxyethoxy, sec-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy, 2-(2,4-di-t-pentylphenoxy)ethoxy, and 2-dodecyloxyethoxy; aryl such as phenyl, 4-t-
• the substituents can themselves be further substituted one or more times with the described substituent groups.
• the particular substituents used can be selected by those skilled in the art to attain the desired properties for a specific application and can include, for example, electron- withdrawing groups, electron-donating groups, and steric groups.
• the substituents can be joined together to form a ring such as a fused ring unless otherwise provided.
• the above groups and substituents thereof can include those having up to 48 carbon atoms, typically 1 to 36 carbon atoms and usually less than 24 carbon atoms, but greater numbers are possible depending on the particular substituents selected.
• Substitution can include fused ring derivatives such as but not limited to benzo-, dibenzo-, naphtha-, or dinaphtho-fused derivatives. These fused ring derivatives can be further substituted as well.
• the organic-based periodic gain region(s) 160 can be comprised of a single host material, but more commonly includes a host material doped with a guest compound (dopant) or compounds where light emission comes primarily from the dopant and can be of any color. These host- dopant combinations are advantageous since they result in very small unpumped scattering/absorption losses for organic-based gain media (can be less than 1 cm "1 ).
• the dopant is usually chosen from highly fluorescent dyes, but phosphorescent compounds, e.g., transition metal complexes as described for OLED applications in WO 98/55561, WO 00/18851, WO 00/57676, and WO 00/70655 are also useful. Dopants are typically coated as 0.01 to 10% by weight into the host material, wherein they can be selected to provide emitted light having hues of either red, green, or blue.
• An example of a useful host-dopant combination for red emitting layers is Alq as the host material and 1% L39 [4-(dicyanomethylene)-2-t-butyl-6-(l,l,7,7-tetramethyljulolidyl-9-enyl)-4H- pyran] as the dopant.
• An important relationship for choosing a dye as a dopant is a comparison of the absorption of the dopant material and emission of the host material. For efficient energy transfer (via Forster energy transfer) from the host to the dopant molecule, a necessary condition is that the absorption of the dopant overlaps the emission of the host material.
• Forster energy transfer which involves a radiationless transfer of energy between the host and dopant molecules.
• An important relationship for choosing the host material is that the absorption of the host material significantly overlaps the emission spectrum of the pump-beam light 180.
• the absorption of the host material or a host material plus a dopant is small at the laser emission wavelength of the VCSEL array device 100.
• An acceptable level of absorption is that the absorption coefficient of the host plus dopant combination is less than 10 cm "1 at the wavelength of the laser emission.
• Useful fluorescent emissive materials includes polycyclic aromatic compounds as described in I.B.
• Tertiary aromatic amines with more than two amine groups can be used including oligomeric materials.
• Another class of useful emissive materials include aromatic tertiary amines, where the latter is understood to be a compound containing at least one trivalent nitrogen atom that is bonded only to carbon atoms, at least one of which is a member of an aromatic ring.
• the aromatic tertiary amine can be an arylamine, such as a monoarylamine, diarylamine, triarylamine, or an oligomeric arylamine.
• Exemplary monomeric triarylamines are illustrated by Klupfel, et al. U.S. Patent 3,180,730.
• Other suitable triarylamines substituted with one or more vinyl radicals and/or comprising at least one active hydrogen containing group are disclosed by Brantley, et al. U.S. Patents 3,567,450 and 3,658,520.
• a more preferred class of aromatic tertiary amines are those which include at least two aromatic tertiary amine moieties as described in U.S. Patents 4,720,432 and 5,061 ,569.
• Such compounds include those represented by structural Formula A wherein: Qi and Q 2 are independently selected aromatic tertiary amine moieties; and G is a linking group such as an arylene, cycloalkylene, or alkylene group of a carbon to carbon bond.
• At least one of Qi or Q 2 contains a polycyclic fused ring structure, e.g., a naphthalene.
• G is an aryl group, it is conveniently a phenylene, biphenylene, or naphthalene moiety.
• a useful class of triarylamines satisfying structural Formula A and containing two triarylamine moieties is represented by structural Formula B R2 I B Rl— C- R 3 R 4 where: Ri and R 2 each independently represent a hydrogen atom, an aryl group, or an alkyl group or Ri and R 2 together represent the atoms completing a cycloalkyl group; and R and R 4 each independently represent an aryl group, which is in turn substituted with a diaryl substituted amino group, as indicated by structural Formula C R5
• R 5 and R 6 are independently selected aryl groups.
• at least one of R 5 or R 6 contains a polycyclic fused ring structure, e.g., a naphthalene.
• the host material can comprise a substituted or unsubstituted triarylamine compound.
• Another class of aromatic tertiary amines is the tetraaryldiamines. Desirable tetraaryldiamines include two diarylamino groups, such as indicated by Formula C, linked through an arylene group.
• Useful tetraaryldiamines include those represented by Formula D wherein: each Are is an independently selected arylene group, such as a phenylene or anthracene moiety; n is an integer of from 1 to 4; and Ar, R 7 , R 8 , and R 9 are independently selected aryl groups.
• at least one of Ar, R 7 , R 8 , and R 9 is a polycyclic fused ring structure, e.g., a naphthalene.
• the various alkyl, alkylene, aryl, and arylene moieties of the foregoing structural Formulae A, B, C, D, can each in turn be substituted.
• Typical substituents include alkyl groups, alkoxy groups, aryl groups, aryloxy groups, and halogens such as fluoride, chloride, and bromide.
• the various alkyl and alkylene moieties typically contain from 1 to about 6 carbon atoms.
• the cycloalkyl moieties can contain from 3 to about 10 carbon atoms, but typically contain five, six, or seven carbon atoms, e.g. cyclopentyl, cyclohexyl, and cycloheptyl ring structures.
• the aryl and arylene moieties are usually phenyl and phenylene moieties.
• the emissive material can be formed of a single or a mixture of aromatic tertiary amine compounds.
• a triarylamine such as a triarylamine satisfying the Formula B
• a tetraaryldiamine such as indicated by Formula D.
• the host material can include a substituted or unsubstituted dicarbazole-biphenyl compound.
• aromatic tertiary amines is the following: 4,4'-NN'-dicarbazole-l,l '-biphenyl (CBP) (DI); 4,4'-Bis[ ⁇ -(l -naphthyl)- ⁇ -phenylamino]biphenyl (D2); 4,4'-Bis[N-(l -na ⁇ hthyl)-N-(2-naphthyl)amino]bi ⁇ henyl (D3); 4,4'-Bis[N-(2-naphthyl)-N- /?-tolylamino]biphenyl (D4); 1 , 1 -Bis(4-di- -tolylaminophenyl)cyclohexane; 1,1 -Bis(4-di- ?-tolylaminophenyl)-4-phenylcyclohexane; 4,4'-Bis(diphen
• the host material can comprise a substituted or unsubstituted aza- aromatic compound.
• the host material can comprise a substituted or unsubstituted acridine, quinoline, purine, phenazine, phenoxazine, or phenanthroline compound.
• Carbazole derivatives are useful hosts.
• Useful examples of phenanthroline materials include 2,9-dimethyl-4,7-diphenyl-l,10- phenanthroline and 4,7-diphenyl-l,10-phenanthroline.
• Host and dopant molecules include, but are not limited to, those disclosed in U.S.
• Metal complexes of 8-hydroxyquinoline and similar derivatives constitute one class of useful host materials capable of supporting electroluminescence, and are particularly suitable for light emission of wavelengths longer than 500 nm, e.g., green, yellow, orange, and red.
• M represents a metal
• n is an integer of from 1 to 3
• Z independently in each occurrence represents the atoms completing a nucleus having at least two fused aromatic rings.
• the metal can be monovalent, divalent, trivalent, or tetravalent metal.
• the metal can, for example, be an alkali metal, such as lithium, sodium, or potassium; an alkaline earth metal, such as magnesium or calcium; an earth metal, such aluminum or gallium, or a transition metal such as zinc or zirconium.
• any monovalent, divalent, trivalent, or tetravalent metal known to be a useful chelating metal can be employed.
• Z completes a heterocyclic nucleus containing at least two fused aromatic rings, at least one of which is an azole or azine ring. Additional rings, including both aliphatic and aromatic rings, can be fused with the two required rings, if required. To avoid adding molecular bulk without improving on function the number of ring atoms is usually maintained at 18 or less.
• the host material can comprise a substituted or unsubstituted chelated oxinoid compound.
• CO-1 Aluminum trisoxine [alias, tris(8-quinolinolato)aluminum(III)]
• CO-2 Magnesium bisoxine [alias, bis(8-quinolinolato)magnesium(II)]
• CO-3 Bis[benzo ⁇ f ⁇ -8-quinolinolato]zinc (II)
• CO-4 Bis(2-methyl-8-quinolinolato)aluminum(III)- ⁇ -oxo-bis(2-methyl-8- quinolinolato) aluminum(III);
• CO-5 Indium trisoxine [alias, tris(8-quinolinolato)indium]
• CO-6 Aluminum tris(5-methyloxine) [alias, tris(5-methyl-8-quinolinolato) aluminum(III)]
• CO-7 Lithium oxine [alias, (8-quinolinolato)lithium(
• the host material can include a substituted or unsubstituted anthracene compound.
• a substituted or unsubstituted anthracene compound derivatives of 9,10-di-(2-naphthyl)anthracene (Formula F) constitute one class of useful hosts capable of supporting photoluminescence, and are particularly suitable for light emission of wavelengths longer than 400 nm, e.g. blue, green, yellow, orange or red.
• R 1 , R 2 , R 3 , R 4 , R 5 , and R 6 represent one or more substituents on each ring where each substituent is individually selected from the following groups: Group 1: hydrogen, or alkyl of from 1 to 24 carbon atoms; Group 2: aryl or substituted aryl of from 5 to 20 carbon atoms; Group 3: carbon atoms from 4 to 24 necessary to complete a fused aromatic ring of anthracenyl, pyrenyl, or perylenyl; Group 4: heteroaryl or substituted heteroaryl of from 5 to 24 carbon atoms as necessary to complete a fused heteroaromatic ring of furyl, thienyl, pyridyl, quinolinyl or other heterocyclic systems; Group 5: alkoxylamino, alkylamino, or arylamino of from 1 to 24 carbon atoms; and Group 6: fluorine, chlorine, bromine or cyano.
• Illustrative examples include 9,10-di-(2-naphthyl)anthracene (FI) and 2-t-butyl-9,10-di-(2-naphthyl)anthracene (F2).
• Other anthracene derivatives can be useful as a host, including derivatives of 9,10-bis-(4-(2,2'- diphenylethenyl)phenyl)anthracene.
• Benzazole derivatives constitute another class of useful hosts capable of supporting photoluminescence, and are particularly suitable for light emission of wavelengths longer than 400 nm, e.g., blue, green, yellow, orange or red.
• n is an integer of 3 to 8;
• Z is O, NR or S; and
• R and R' are individually hydrogen; alkyl of from 1 to 24 carbon atoms, for example, propyl, t-butyl, heptyl, and the like; aryl or hetero-atom substituted aryl of from 5 to 20 carbon atoms for example phenyl and naphthyl, furyl, thienyl, pyridyl, quinolinyl and other heterocyclic systems; or halo such as chloro, fluoro; or atoms necessary to complete a fused aromatic ring; and
• L is a linkage unit including alkyl, aryl, substituted alkyl, or substituted aryl, which conjugately or unconjugately connects the multiple benzazoles together.
• the host material can comprise a substituted or unsubstituted benzoxazole compound, a substituted or unsubstituted benzothiazole compound, or a substituted or unsubstituted benzimidazole compound.
• the host material can comprise a substituted or unsubstituted oxazole compound, a substituted or unsubstituted triazole compound, or a substituted or unsubstituted oxadiazole compound.
• oxazole compounds include l,4-bis(5- phenyloxazol-2-yl)benzene, 1 ,4-bis(4-methyl-5-phenyloxazol-2-yl)benzene, and l,4-bis(5-(p-biphenyl)oxazol-2-yl)benzene.
• oxadiazole compounds include 2-(4-biphenylyl)-5-phenyl-l,3,4-oxadiazole and 2-(4- biphenylyl)-5-(4-tert-butylphenyl)-l,3,4-oxadiazole.
• triazole compounds include 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl- 1 ,2,4-triazole.
• Distyrylarylene derivatives are also useful as host materials or dopant materials. Many examples are described in U.S. Patent 5,121,029.
• Useful examples include 1 ,4-bis(2-methylstyryl)- benzene, 4,4'-(9, 10-anthracenediyldi-2, 1 -ethenediyl)bis(N,N-bis(4-methylphenyl)- benzenamine, 4,4'-(l,4-naphthalenediyldi-2,l-ethenediyl)bis(N,N-bis(4- methylphenyl)benzenamine, and 4,4'-(l,4-phenylenedi-2,l-ethenediyl)bis(N,N-(4- tolyl))benzeneamine.
• the organic-based dopant is selected to provide emission between 300-1700 nm.
• the dopant can be selected from fluorescent or phosphorescent dyes.
• Useful fluorescent dopants include materials as described as host materials above.
• Other useful fluorescent dopants include, but are not limited to, derivatives of substituted or unsubstituted anthracene, tetracene, xanthene, perylene, rubrene, coumarin, rhodamine, and quinacridone, dicyanomethylenepyran compounds, thiopyran compounds, polymethine compounds, pyrilium and thiapyrilium compounds, fluorene derivatives, periflanthene derivatives, indenoperylene derivatives, bis(azinyl)amine boron compounds, bis(azinyl)methane compounds, napthyridine, fluoranthene, furan, indole, thiaphene, benzoxanthene, pyrene, peropyrene, terphenyl, quaterphenyl, quinquephenyl
• emissive materials include various heterocyclic optical brighteners as described in U.S. Patent 4,539,507.
• the emissive material can also be a polymeric material, a blend of two or more polymeric materials, or a doped polymer or polymer blend.
• the emissive material can also include more than one nonpolymeric and polymeric material with or without dopants. Typical dopants are listed previously for nonpolymeric molecules. Nonpolymeric dopants can be molecularly dispersed into the polymeric host, or the dopant could be added by copolymerizing a minor constituent into the host polymer.
• Typical polymeric materials include, but are not limited to, substituted and unsubstituted poly(p-phenylenevinylene) (PPV) derivatives, substituted and unsubstituted poly(p-phenylene) (PPP) derivatives, substituted and unsubstituted polyfluorene (PF) derivatives, substituted and unsubstituted poly(p-pyridine), substituted and unsubstituted poly(p- pyridalvinylene) derivatives, and substituted, unsubstituted poly(p-phenylene) ladder and step-ladder polymers, and copolymers thereof as taught by Diaz- Garcia, et al. in U.S. Patent 5,881,083 and references therein.
• the substituents include but are not limited to alkyls, cycloalkyls, alkenyls, aryls, heteroaryls, alkoxy, aryloxys, amino, nitro, thio, halo, hydroxy, and cyano.
• Typical polymers are poly(p-phenylene vinylene), dialkyl-, diaryl-, diamino-, or dialkoxy- substituted PPV, mono alkyl-mono alkoxy-substituted PPV, mono aryl-substituted PPV, 9,9'-dialkyl or diaryl-substituted PF, 9,9'-mono alky-mono aryl substituted PF, 9-mono alky or aryl substituted PF, PPP, dialkyl-, diamino-, diaryl-, or dialkoxy-substituted PPP, mono alkyl-, aryl-, alkoxy-, or amino-substituted PPP.
• polymeric materials can be used such as poly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole, polyaniline, and copolymers such as poly(3 ,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) also called PEDOT/PSS.
• PVK poly(N-vinylcarbazole)
• polythiophenes polypyrrole
• polyaniline polyaniline
• copolymers such as poly(3 ,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) also called PEDOT/PSS.
• the organic materials mentioned above are suitably deposited through sublimation, but can be deposited from a solvent with an optional binder to improve film formation. If the material is a polymer, solvent deposition is usually preferred.
• the material to be deposited by sublimation can be vaporized from a sublimator "boat" often comprised of
• Patent 6,237,529 can be first coated onto a donor sheet and then sublimed in closer proximity to the substrate. Layers with a mixture of materials can utilize separate sublimator boats or the materials can be pre-mixed and coated from a single boat or donor sheet. As shown in FIG. 3 and discussed above, the VCSEL array contains red, green, and blue emitting pixels with dimensions on the order of 80 x 240 ⁇ m. The emission color is determined by the combination of the length of the lasing path and the fluorescence spectrum of the gain media contained in the periodic gain region 160. Patterned deposition of the gain media contained in the periodic gain region 160 can be achieved using shadow masks, integral shadow masks (U.S.
• Patent 5,294,870 spatially-defined thermal dye transfer from a donor sheet (U.S. Patents 5,688,551; 5,851,709; and 6,066,357) and inkjet methods (U.S. Patent 6,066,357). If the periodic gain region 160 is more than one layer, then the patterned deposition needs to be repeated accordingly. Most organic-based laser devices are sensitive to moisture or oxygen, or both, so they are commonly sealed in an inert atmosphere such as nitrogen or argon.
• Desiccant such as alumina, bauxite, calcium sulfate, clays, silica gel, zeolites, alkaline metal oxides, alkaline earth metal oxides, sulfates, or metal halides and perchlorates can be incorporated into the sealed device.
• Methods for encapsulation and desiccation include, but are not limited to, those described in U.S. Patent 6,226,890.
• barrier layers such as SiOx, Teflon, and alternating inorganic/polymeric layers are known in the art for encapsulation.
• spacer layer 170 it is preferred to use a material that is highly transparent to both the laser light 190 and the pump-beam light 180.
• 1 -Bis-(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane (TAPC) is chosen as the spacer material, since it has very low absorption throughout the visible and near UV spectrum and its index of refraction is slightly lower than that of most organic host materials. This refractive index difference is useful since it helps in maximizing the overlap between the standing e-field antinodes and the periodic gain region(s) 160.
• the spacer layer 170 can also be composed of inorganic materials, such as SiO 2 , since it has low absorption and its index of refraction is less than that of organic host materials.
• the materials can be deposited either by thermal evaporation, e-beam at low deposition temperatures (around 70°C), or colloidal methods.
• the lower net gain regions 150 are produced by locally spoiling the emissive properties of the periodic gain region(s) 160.
• An effective way to form the lower net gain regions 150 is to use standard photolithographic masks and UV exposing apparatus in order to produce a patterned UV exposure of the periodic gain region(s) 160.
• the UV exposed areas correspond to the interpixel region 210
• the unexposed areas correspond to the laser pixels 200.
• the shape of the laser pixels 200 is circular; however, other pixel shapes are possible, such as rectangular.
• the size of the laser pixels 200 is in the range of 2.5 to 20 microns.
• the preferred laser pixel 200 diameter is 2.5 to 4.5 ⁇ m.
• the interpixel spacing is in the range of 0.25 to 4 ⁇ m.
• the spaced laser pixels 200 can have the same or different sizes and the spacings between pixels can have the same or different lengths to cause the output of the VCSEL array device 100 to produce locally single or multimode laser output.
• the emissive intensity of the periodic gain region(s) 160 can be locally modulated by ways other than high intensity UV radiation, such as those ways commonly practiced in the art.
• the deposition of the top dielectric stack 140 Following the growth of the active region 130 and the production of the lower net gain regions 150 is the deposition of the top dielectric stack 140.
• the top dielectric stack 140 is spaced from the bottom dielectric stack 120 and reflective to light over a predetermined range of wavelengths. Its composition is analogous to that of the bottom dielectric stack.
• the top dielectric stack 140 Since the top dielectric stack 140 is deposited over an active region 130 that contains organics (for the case of organic-based gain media), its deposition temperature must be kept low in order to avoid melting the organics. As a result, a typical deposition temperature for the top dielectric stack 140 is 100°C or lower.
• the top dielectric stack can be deposited by conventional ways, such as e-beam, low-energy sputtering, or colloidal deposition. In order to obtain effective lasing performance, it is preferred that the peak reflectivities of the top and bottom dielectric stacks be greater than 99%, where smaller values result in larger lasing linewidths.
• the VCSEL array device 100 is optically driven by an incident pump-beam light 180 and emits laser light 190.
• the pump-beam can be incoherent LED light.
• FIG. 2 shows laser light 190 through the top dielectric stack 140.
• the laser structure could be optically pumped through the top dielectric stack 140 with the laser light 190 through the substrate 110 by proper design of the dielectric stack reflectance properties.
• the operation of the VCSEL array device 100 occurs by the following ways.
• the pump-beam light 180 transmits through the substrate 110 and the bottom dielectric stack 120 and is absorbed by the periodic gain region(s) 160, wherein some fraction of the pump-beam energy is re-emitted as longer wavelength laser light at the position of the laser pixels 200.
• the top dielectric stack peak reflectance When the pump-beam light 180 enters through the substrate 110, to ensure that the laser light 190 mainly exits through the top dielectric stack 140, it is necessary to choose the top dielectric stack peak reflectance to be smaller than the bottom dielectric stack 120 peak reflectance. To improve the power conversion efficiency of the device, it is common practice to add additional dielectric layers to both dielectric stacks, such that, the top dielectric stack 140 is highly reflective to the pump-beam light 180 and the bottom dielectric stack 120 is highly transmissive to the pump-beam light 180. As discussed above, another way for spatially modulating the net gain of the periodic gain region(s) 160 is to modulate the excitation of the periodic gain region(s) 160 by the pump-beam light 180. Another embodiment of the present invention is given in FIG.
• laser array device 102 which contains absorbing elements 155.
• the absorbing elements 155 be placed adjacent to the active region 130.
• the composition of the absorbing elements 155 is any material that absorbs the pump-beam light 180 and only minimally absorbs and scatters the laser light 190. It is preferred that at the emission wavelengths of the pump-beam light 180, the absorbing elements' 155 absorption coefficient is greater than 10 4 cm "1 .
• the thickness of the absorbing elements 155 is chosen such that a significant percentage of the pump-beam light 180 is absorbed by the elements.
• a preferred absorption fraction is greater than 25%.
• the first way is to deposit a uniform dye layer 157 and use patterned UV light to modify selectively the abso ⁇ tion coefficient of the dye layer 157. As discussed above with reference to FIG. 2, the UV light can be patterned using conventional photolithographic masks.
• dyed photoresists are well known in the art, and are spin cast and patterned by standard photolithographic techniques.
• the active region 130 and the top dielectric stack 140 are deposited in sequence. Since the absorbing elements 155 need to be placed between the birefringent layer 126 and the active region 130, and absorb a portion of the pump-beam light 180, it is necessary for the pump-beam light 180 to enter through the substrate 110.
• the absorbing elements 155 There are also other ways, as commonly practiced in the art, to produce the absorbing elements 155.
• etched pits can be formed in a transparent layer (such as SiO 2 ), over which can be deposited the absorbing elements 155 material.
• CMP chemical mechanical polishing
• the positions of the absorbing elements 155 correspond to the inte ⁇ ixel region 210, while the remaining areas correspond to the laser pixels 200.
• the shape of the laser pixels 200 is circular; however, other pixel shapes are possible, such as rectangular.
• the size of the laser pixels 200 is in the range of 2.5 to 20 microns. For single transverse mode laser operation, the preferred laser pixel 200 diameter is 2.5 to 4.5 ⁇ m.
• the inte ⁇ ixel spacing is in the range of 0.25 to 4 ⁇ m.
• the spaced laser pixels 200 can have the same or different sizes and the spacings between pixels can have the same or different lengths to cause the output of the laser array device 102 or 103 to produce locally single or multimode laser output.
• FIG. 6 shows another embodiment of the present invention.
• This laser array device 104 is a variation of the one illustrated in FIG. 5.
• the active region 130 is grown directly on the absorbing elements 155.
• the active region 130 and the top dielectric stack 140 are deposited on a non- planar (corrugated) surface for the case of the absorbing elements formed by dyed photoresist (note that the case of growing in the etch pits followed by CMP results in a planar surface).
• the absorbing elements 155 are planarized by a planarization layer 158, using techniques well known in the art, prior to depositing the active region 130.
• the planarization layer 158 material is deposited by suitable processes. Next, using CMP techniques, which are well known in the art, the planarization layer 158 material is polished until it is flush (or within a couple tens of nanometers) with the top surface of the absorbing elements 155.
• a second embodiment of the planarization layer 158 is to use polymethyl-methacrylate (PMMA). In this case PMMA is spun cast over the spaced apart absorbing elements 155 to a thickness range of .5 to 3.0 ⁇ m, followed by a conventional bake at 150 to 220°C.
• PMMA polymethyl-methacrylate
• FIG. 7 shows another embodiment of the present invention, laser array device 106.
• the way for spatially modulating the net gain of the VCSEL device is to etch selectively (reflectance modulation) the bottom dielectric stack 120.
• the etched surface of the bottom dielectric stack be removed from the position of the active region 130 where the intensity of the standing electromagnetic field (e-field) is highest.
• the bottom dielectric stack 120 is deposited in two parts, a first portion 121 and a second portion 125, whereby the reflectance modulation is obtained by forming an etched region 151 in the surface of the first portion of the bottom dielectric stack 121.
• the first portion of the bottom dielectric stack 121 contain at most 3 to 5 dielectric layers which reflect the laser light. For cases where additional dielectric layers are added to the bottom stack for reflecting the pump-beam light 180 back into the active region 130, these layers are to be deposited first in the first portion of the bottom dielectric stack 121.
• the patterned etched region 151 is formed in the first portion of the bottom dielectric stack 121 by using standard photolithographic and etching techniques, thus forming a two-dimensional array of circular pillars on the surface of the first portion of the bottom dielectric stack 121.
• the shape of the laser pixels is circular; however, other pixel shapes are possible, such as rectangular.
• the inte ⁇ ixel spacing is in the range of 0.25 to 4 ⁇ m.
• the second portion of the bottom dielectric stack 125 is deposited over the first portion of the bottom dielectric stack 121 after having formed the etched region 151. As shown schematically in FIG. 7, the second portion of the bottom dielectric stack 125 fills the etched region 151.
• the second portion of the bottom dielectric stack 125 is composed of alternating layers of high and low refractive index dielectric materials, such as TiO 2 and SiO 2 , respectively.
• the second portion can be deposited by e- beam, PECVD, sputtering, sol-gel methods or colloidal deposition.
• FIG. 8 shows another embodiment of the present invention, laser array device 108. This device is a variation of the one illustrated in FIG. 7.
• the second portion of the bottom dielectric stack 125 is grown directly on the etched region 151.
• the stack is deposited on a non-planar (corrugated) surface.
• deposition on a corrugated surface can lead to columnar growth of the stacks.
• the etched surface of the first portion of the bottom dielectric stack 121 is planarized by a planarization layer 158 prior to depositing the second portion of the bottom dielectric stack 125.
• a planarization layer 158 is polyimide for the Ta 2 O 5 -SiO 2 or TiO 2 -SiO 2 multilayer stack systems. Following the production of the etched regions 151, 2 to 3 microns of polyimide are deposited on the surface of the first portion of the bottom dielectric stack 121 by spin casting and then hardened by a bake at temperatures ranging from 180 to 250°C.
• a second embodiment of the planarization layer 158 is SiO 2 for the Ta 2 ⁇ 5 -Si ⁇ 2 multilayer dielectric stack system.
• the top layer of the first portion of the bottom dielectric stack 121 is a thin layer of Si N 4 .
• the silicon nitride can be deposited by plasma-enhanced chemical vapor deposition (CVD) at a temperature range of 300-400°C and in a thickness range of 10 to 200 nm.
• CVD plasma-enhanced chemical vapor deposition
• the planarization layer 158 of SiO 2 is deposited at a thickness of 0.75 to 2.0 ⁇ m by either CVD or thermal evaporation.
• CMP is used with another common slurry to polish the SiO 2 until it is flush (or within a couple tens of nanometers) with the top of the silicon nitride layer.
• a third embodiment of the planarization layer 158 is PMMA for any multilayer dielectric stack system.
• PMMA is spun cast over the etched surface of the first portion of the bottom dielectric stack 121 to a thickness range of .5 to 3.0 ⁇ m, followed by a conventional bake at 150 to 220°C.
• a conventional bake at 150 to 220°C is another methodology.
• a simplified liquid crystal display can be made.
• the more simplified LCD typically contains a backlight unit 220, the VCSEL array device 100, a polarizer layer 305, a light shutter layer 310, and a beam expander 320.
• the backlight unit 220 provides the pump-beam light 180 for the VCSEL array device 100.
• the VCSEL array device 100 provides a colored, pixelated light source for the light shutter layer 310. If the VCSEL array device 100 includes the birefringent layer 126, then its output is also polarized and the polarizer layer 305 can be limited. Otherwise the polarizer layer 305 passes one polarization of the laser light 190 to the light shutter layer 310.
• the light shutter layer 310 either passes or blocks polarized light in a pixelated structure.
• the beam expander 320 takes the light exiting the light shutter layer 310 and expands its viewing cone.
• the backlight unit 220 as shown in FIGS.
• the 10-13 for producing the pump-beam light 180 is comprised of a diffuser 240 and either light emitting diodes (LEDs) 230 or a cold cathode fluorescent lamp (CCFL) 280.
• the diffuser 240 homogenizes the light incident on the VCSEL array device 100.
• the LEDs 230 are typically either in a linear array 250 illuminating the edge of a waveguide 260, which then redirects the light such that it is illuminating the VCSEL array device 100, or in a planar array 270 directly illuminating the VCSEL array device 100.
• the CCFL 280 is typically either illuminating the edge of the waveguide 260, which redirects the light such that it is illuminating the VCSEL array device 100, or oriented in rows 300 underneath the diffuser and directly illuminating the VCSEL array device 100.
• the small divergence angle of the VCSEL array device 100 enables a 1 : 1 correspondence between the laser array's emitting elements 205 and the light shutter layer's 310 color elements.
• the light shutter layer 310 only needs to modulate the colored light incident from the VCSEL array device 100; thus, limiting the efficiency loss associated with color filter arrays.
• An additional feature of the near collimation of the light output from the VCSEL array device 100 is that the viewing angle compensation films can be removed from the display structure. Also due to the natural collimation (3-5° divergence angle) of the VCSEL array device 100 light output, is that the collimating films, which are typically included in the backlight unit 220, can be removed. As a result of the limitation of the viewing angle compensation films and the collimating films from the display structure, the cost of the liquid crystal display device can be reduced. However, to prevent light leakage from neighboring pixels, the very small divergence of the VCSEL array device 100 light output must be accounted for.
• the size of the laser array's emitting elements 205 must be slightly reduced in order that the laser light upon traversing into the light shutter layer 310 will subtend the proper pixel dimension of approximately 80 x 240 ⁇ m.
• the size of the emitting elements can be adjusted by selectively depositing metal between the bottom dielectric stack 120 and the substrate 110.
• Preferred metals are Al or Ag which can be selectively deposited by well known evaporation techniques. These metals are highly reflective of the pump-beam light 180 and will cause the recycling of the pump-beam light 180 until it passes between the metal depositions.
• the multimode laser light output from the two-dimensional vertical cavity laser array will be polarized preferentially along one direction.
• the bottom polarizer element and its associated reflective polarizer element are not needed in the backlight unit 220. Removal of these elements from the display structure results in a cost savings.
• no effort can be made to preferentially polarize the VCSEL output. In that case it will be necessary to add the polarizer layer 305 in between the top of the VCSEL array device 100 and the bottom of the light shutter layer 310.
• the light shutter layer 310 is typically a liquid crystal cell 330 with an analyzer 340 on the side farthest from the VCSEL array device 100.
• the liquid crystal cell 330 is analogous to conventional liquid crystal cells except that it does not contain a CFA.
• the liquid crystal cell 330 does not require a CFA since the light output from the VCSEL array device 100 is pixelated into red, green, and blue laser light emission.
• the liquid crystal cell 330 comprises liquid crystal substrates 350 on the top and bottom.
• the liquid crystal substrates 350 in the liquid crystal cell 330 can include either glass plates or plastic substrates.
• the thickness of the liquid crystal substrates 350 should be sufficiently thin to prevent parallax, which would result in light leakage through adjacent pixels.
• the thickness of the liquid crystal substrates 350 should preferably be less then 0.5 mm.
• Both of the liquid crystal substrates 350 are coated with a patterned transparent conductor layer 360. Typical transparent conductors are indium tin oxide.
• On top of each of the transparent conductor layers 360 is coated an alignment layer 370.
• an alignment layer 370 is coated the liquid crystal material 380.
• the liquid crystal cell 330 modulates the light intensity output from the VCSEL array device 100 by orienting the liquid crystal molecules upon selective application of voltages.
• the liquid crystal cell 330 can also contain thin film transistors at each pixel location, permitting the display to be driven actively. However, the invention does not require a specific drive scheme.
• the light shutter layer 310 also contains the analyzer 340 which resolves the polarized light output from the liquid crystal cell 330.
• Those skilled in the art will appreciate that other light shutters can be used with the present invention.
• An example is a light shutter produced by electrowetting. In this light switch, as demonstrated by Hayes, et al., Nature, 425, 383 (2003), the application of an electric field changes the degree to which dye- containing oil droplets cover the surface of each pixel. In effect, the electric field modifies the hydrophobicity of the pixel surface.
• each pixel upon exiting the beam expander 320, each pixel should be as clearly distinguishable as prior to entering the beam expander 320.
• the expansion of the viewing cone by the beam expander 320 can be adjusted accordingly.
• optic axis x-y-z coordinate system display surface display normal direction optic axis

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