Quantum photonic imagers and methods of fabrication thereof

• US 7,623,560 B2
• Filed: 12/26/2007
• Issued: 11/24/2009
• Est. Priority Date: 09/27/2007
• Status: Active Grant

• Current Assignee: Ostendo Technologies Inc.
• Original Assignee: Ostendo Technologies Inc.
• Inventors: El-Ghoroury, Hussein S., McNeill, Dale A., Brown, Robert G. W., DenBoer, Huibert, Lanzone, Andrew J.
• Primary Examiner(s): Garber; Charles D
• Assistant Examiner(s): Abdelaziez; Yasser A
• Application Number:
  US11/964,642
• Publication Number:
  US 20090086170A1
• Time in Patent Office: 699 Days
• Field of Search: 353/38, 372/50.121, 372/46.013, 372/45.01, 345/46, 345/48, 348 E9024- E9026, 362551-553, 257/E27.135, 257/138, 438/22
• US Class Current: 372/50.121
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2340/06 Colour space transformation
• CPC Class Codes: G09G 3/2018 by time modulation using two or more time intervals
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: H01S 5/02345 Wire-bonding
• CPC Class Codes: H01S 5/18 Surface-emitting [SE] lasers, e.g. having both horizontal and vertical cavities
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/3063 using Mg
• CPC Class Codes: H01S 5/34326 with a well layer based on InGa(Al)P, e.g. red laser
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
• CPC Class Codes: H01S 5/4043 with vertically stacked active layers
• CPC Class Codes: H01S 5/4093 Red, green and blue [RGB] generated directly by laser action or by a combination of laser action with nonlinear frequency conversion
• CPC Class Codes: H04N 9/3161 using laser light sources using laser beams scanning the display screen H04N9/3129

Abstract

Emissive quantum photonic imagers comprised of a spatial array of digitally addressable multicolor pixels. Each pixel is a vertical stack of multiple semiconductor laser diodes, each of which can generate laser light of a different color. Within each multicolor pixel, the light generated from the stack of diodes is emitted perpendicular to the plane of the imager device via a plurality of vertical waveguides that are coupled to the optical confinement regions of each of the multiple laser diodes comprising the imager device. Each of the laser diodes comprising a single pixel is individually addressable, enabling each pixel to simultaneously emit any combination of the colors associated with the laser diodes at any required on/off duty cycle for each color. Each individual multicolor pixel can simultaneously emit the required colors and brightness values by controlling the on/off duty cycles of their respective laser diodes.

Claims

1. An emissive multicolor digital image forming (imager) device comprising;

a two dimensional array of multicolor laser emitting pixels whereby each multicolor laser emitting pixel comprises;

a plurality of laser diode semiconductor structures, each for emitting a different color, stacked vertically with a grid of vertical sidewalls electrically and optically separating each multicolor pixel from adjacent multicolor pixels within the array of multicolor pixels; and

a plurality of vertical waveguides optically coupled to the laser diode semiconductor structures to vertically emit laser light generated by the laser diode semiconductor structures from a first surface of the stack of laser diode semiconductor structures;

the stack of laser diode semiconductor structures being stacked onto a digital semiconductor structure by a second surface opposite the first surface of the stack of laser diode semiconductor structures; and

a plurality of digital semiconductor circuits in the digital semiconductor structure, each electrically coupled to receive control signals from the periphery of the digital semiconductor structure and electrically coupled to the multicolor laser diode semiconductor structures by vertical interconnects embedded within the vertical sidewalls to separately control the on/off states of each of the multicolor laser diode semiconductor structures.

2. The device of claim 1 wherein each laser diode semiconductor structure has a metal layer on the top and bottom thereof, the metal layers on adjacent laser diode semiconductor structures being separated by an insulation layer between the respective metal layers.

3. The device of claim 2 wherein the metal layers provide positive and negative contacts with each of the stacked laser diode semiconductor structures.

4. The device of claim 3 further comprising a patterned interconnect layer of metal isolated from the metal layers with a patterned insulation layer and connected to the vertical interconnects to provide contact pads for interconnecting the digital semiconductor structure with each of the laser diode semiconductor structures in the two dimensional array of multicolor laser emitting pixels.

5. The device of claim 4 wherein each laser diode semiconductor structure is separately addressable through the contact pads.

6. The device of claim 1 wherein the vertical sidewalls with vertical interconnects therein comprise alternate layers of insulation and metal surrounding each pixel, whereby the optical separation provided by the metal layers around each pixel is uninterrupted.

7. The device of claim 1 wherein each laser diode semiconductor structure comprises an active region and an optical confinement region, the active region of each laser diode semiconductor structure being comprised of multiple semiconductor layers of Al_xIn_1-xP, Ga_xIn_1-xP or In_xGa_1-xN, and forming multiple quantum wells, multiple quantum wires or multiple quantum dots.

8. The device of claim 7 wherein the composition of the semiconductor layers enable each of the laser diode semiconductor structures to generate laser light with a wavelength within the range of visible light including 430-nm to 650-nm.

9. The device of claim 7 wherein the composition of the semiconductor layers enable each multicolor laser emitting pixel to emit multiple color primaries of a native color gamut, including red, yellow, green, cyan and blue wavelengths.

10. The device of claim 7 wherein the vertical waveguides are optically coupled to each of the optical confinement regions of the laser diode semiconductor structures.

11. The device of claim 1 wherein the vertical waveguides are comprised of a core and a multilayer cladding, the core being either filled with dielectric material or is air-filled.

12. The device of claim 11 wherein each laser diode semiconductor structure comprises an active region and an optical confinement region, the multilayer cladding being comprised of an outer cladding layer of dielectric material and an inner thin cladding layer of reflective metallic material, the thickness of the inner thin cladding material being selected to allow a portion of the light generated by the active regions of the laser diode semiconductor structures and confined within the confinement regions to be evanescence field coupled into the cores of the vertical waveguides and emitted vertically from the surface of the two dimensional array.

13. The device of claim 11 wherein each laser diode semiconductor structure comprises an active region and an optical confinement region, the multilayer cladding being comprised of multiple thin layers of dielectric material, the refractive indices of the core and the multiple thin cladding layers and the thickness of the multiple cladding layers being selected to allow a portion the light generated by the active regions and confined within the confinement regions to be coupled into the cores of the vertical waveguides and be index guided and emitted vertically from the surface of the two dimensional array.

14. The device of claim 11 wherein each laser diode semiconductor structure comprises an active region and an optical confinement region, the multilayer cladding comprising a thin layer of nonlinear optical material having its thickness and linear and nonlinear refractive indices selected to cause the coupling of the light generated by the active regions and confined within the confinement regions to be either inhibited or enabled as the refractive index of the thin nonlinear cladding layer changes in response to the changes in the intensity of the light being confined within the confinement regions, thereby causing the light being coupled into and index guided by the vertical waveguides and emitted vertically from the surface of the two dimensional array to occur in short pluses separated by short intervals.

15. The device of claim 1 wherein each laser diode semiconductor structure comprises an active region and an optical confinement region, each vertical waveguide having a circular cross section with an index guiding diameter at the center of the coupling region within each of the confinement regions of the laser diode semiconductor structures equal to the wavelength of the laser light generated by the respective active region.

16. The device of claim 1 wherein each laser diode semiconductor structure comprises an active region and an optical confinement region, and wherein for each laser diode semiconductor structure, at least one vertical waveguide extends from the first surface of the stack of laser diode semiconductor structures and terminates at the end of the optical confinement region of that laser diode semiconductor structure.

17. The device of claim 1 wherein the vertical waveguides are arranged in a pattern selected to reduce the maximum divergence angle of the light emitted from surface of the two dimensional array.

18. The device of claim 1 wherein the vertical waveguides are spaced within the pixel surface area to provide uniform brightness across each pixel area and provided in number to maximize pixel brightness.

19. The device of claim 1 wherein the laser diode semiconductor structures comprise:

multiple semiconductor layers of one or more of the following semiconductors alloy materials;

Al_xIn_1-xP, (Al_xGa_1-x)_yIn_1-yP, Ga_xIn_1-xP, Al_xGa_1-xN, Al_xGa_1-xN/GaN, In_xGa_1-xN, GaN;

each formed on a separate wafer over a thick substrate layer of either GaAs, GaN or InGaN;

each including an n-type etch-stop layer and a p-type contact layer of the same respective semiconductor substrate layer material type;

each comprising n-type and p-type waveguide layers and cladding layers that define their respective optical confinement regions;

each having at least one quantum well surrounded by two barrier layers that define their respective active regions; and

each comprising an electron blocker layer embedded either within their respective p-type waveguide layers or between their respective p-type waveguide and cladding layers.

20. The device of claim 1 wherein the digital semiconductor structure is responsive to serial bit streams that are serial representations of multiple bit words that each define a color component and brightness of respective pixels to convert a source digital image data input into an optical image whereby each of the multicolor pixels emits light having color and brightness that reflects the color and brightness values represented by source digital image input data of the respective pixel.

21. The device of claim 1 further comprising a companion device to receive image source data and convert the image source data into the on-off duty cycle values of laser diodes comprising each of the pixels of the emissive multicolor image forming device, the companion device including:

a color-space conversion block;

a uniformity correction block, including a weighting factor look-up table;

a pulse-width modulation conversion block; and

a synchronization and control block;

the weighting factor look-up table storing brightness uniformity weighting factors for each color of each pixel determined by a device-level test in which brightness of the pixel array comprising the emissive aperture is measured and a brightness uniformity weighting factor is calculated for each laser color for each pixel.

22. The device of claim 21 wherein the device is configured to receive serial data streams for each color laser diode and control signals for on-off duty cycle control of each laser diode in the array of stacked laser diode semiconductor structures, the companion device being configured to provide serial data streams for each color laser diode and control signals for on-off duty cycle control of each laser diode in the array of stacked laser diode semiconductor structures.

23. The device of claim 1 wherein each two dimensional array of multicolor laser emitting pixels is cut from a wafer of multiple two dimensional arrays of multicolor laser emitting pixels, and each digital semiconductor structure is cut from a wafer of multiple digital semiconductor structures, each two dimensional array of multicolor laser emitting pixels being die-level bonded to a respective digital semiconductor structure.