Steady-state non-equilibrium distribution of free carriers and photon energy up-conversion using same

• US 20040253759A1
• Filed: 06/10/2004
• Published: 12/16/2004
• Est. Priority Date: 06/12/2003
• Status: Active Grant

• Current Assignee: Sirica Corp.
• Original Assignee: Sirica Corp.
• Inventors: Baskin, Emanuel, Epstein, Alexander, Garber, Valery, Spektor, Boris, Fayer, Alexander
• Granted Patent: US 6,995,371 B2
• Time in Patent Office: Days
• US Class Current: 438/46
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: G02B 2006/12038 Glass (SiO2 based materials)
• CPC Class Codes: G02F 1/353 Frequency conversion, i.e. wherein a light beam is generated with frequency components different from those of the incident light beams
• CPC Class Codes: G02F 1/3556 Semiconductor materials, e.g. quantum wells
• CPC Class Codes: G02F 2/02 Frequency-changing of light, e.g. by quantum counters
• CPC Class Codes: G02F 2202/10 semiconductor
• CPC Class Codes: G02F 2202/36 Micro- or nanomaterials
• CPC Class Codes: G02F 2203/11 involving infrared radiation
• CPC Class Codes: H01L 27/1462 Coatings
• CPC Class Codes: H01L 27/14649 Infrared imagers
• CPC Class Codes: H01L 31/02162 for filtering or shielding light, e.g. multicolour filters for photodetectors

Abstract

Methods and specialized media adapted to the formation of a steady-state, non-equilibrium distribution of free carriers using mesoscopic classical confinement. Specialized media is silicon-based (e.g., crystalline silicon, amorphous silicon, silicon dioxide) and formed from mesoscopic sized particles embedded with a matrix of wide-bandgap material, such as silicon dioxide. An IR to visible light imaging system is implemented around the foregoing.

Claims

1. A method of forming a steady-state, non-equilibrium distribution of free carriers, comprising:

providing a composite structure formed from mesoscopic sized regions embedded within a wide-bandgap material; and

,

introducing free carriers into the composite structure.

3. The method of claim 1, wherein the introduction of free carriers is accomplished by illuminating the composite structure with optical pumping energy.

5. The method of claim 3, wherein illuminating the composite structure further comprises:

providing a source for the optical pumping energy, such that the optical pumping energy is applied directly to a surface of the composite structure.

6. The method of claim 3, wherein illuminating the composite structure further comprises:

providing a source for the optical pumping energy, such that the optical pumping energy is applied to a surface of the composite structure through a transparent support layer.

7. The method of claim 3, wherein illuminating the composite structure further comprises:

forming a waveguide structure adapted to reflect the optical pumping energy through the composite structure; and

,

optically coupling a source for the optical pumping energy to the waveguide structure.

8. The method of claim 7, wherein the waveguide structure passes optical wavelengths in the electromagnetic spectrum corresponding to a visible light spectrum, an IR spectrum, and a near-IR spectrum.

9. The method of claim 7, wherein forming the waveguide structure further comprises:

forming a first reflective layer under the composite structure; and

,

forming a second reflective layer over the composite structure.

2. The method of 1, wherein the mesoscopic sized regions are crystalline silicon particles and the wide band-gap material is silicon dioxide.

4. The method of claim 4, wherein the optical pumping energy is tunable across range of wavelengths.

10. A method of forming a composite structure, comprising:

forming a first layer of wide-bandgap material;

forming a second layer of particle material on the first layer;

forming mesoscopic particles from the second layer;

forming a third layer of wide-bandgap material, such that the mesoscopic particles are embedded within wide-bandgap material.

11. The method of claim 10, wherein the wide-bandgap material is silicon dioxide and the particle material is amorphous silicon, and wherein the step of forming mesoscopic particles further comprises:

forming crystalline silicon particles from the amorphous silicon.

12. A method of forming a composite structure, comprising:

forming, at least in part, a matrix of wide band-gap material; and

,

forming mesoscopic particles within the matrix of wide band-gap material.

13. The method of claim 12, wherein forming the mesoscopic particles further comprises a photolithographic process.

14. The method of claim 12, wherein forming the mesoscopic particles further comprises a laser re-crystallization process.

15. The method of claim 12, wherein forming the mesoscopic particles further comprises a magnetron sputtering process.

16. The method of claim 12, wherein forming the mesoscopic particles further comprises an enhanced chemical vapor deposition process.

17. The method of claim 12, wherein the wide band-gap material is silicon dioxide and the forming the mesoscopic particles further comprises:

forming a silicon based layer on the wide-bandgap material;

etching the silicon based layer to form mesoscopic sized regions; and

,

annealing the resulting structure to from the mesoscopic silicon particles.

18. The method of claim 17, wherein etching the silicon based particle layer further comprises:

before etching the silicon based layer, coating the silicon based layer with a photoresist impregnated with metal particles.

19. The method of claim 18, wherein at least one the silicon based layer and the wide band-gap material is one selected from a group consisting of;

amorphous silicon, crystalline silicon, a silicon oxide, a silicon nitride, and a silicon ceramic

20. A method of forming a composite structure, comprising:

forming a silicon based layer;

forming a sacrificial layer over the silicon based layer;

coating the sacrificial layer with a liquid photoresist impregnated with metal particles;

etching the sacrificial layer to form protective islands of the sacrificial layer under the metal particles; and

developing the silicon based layer to form mesoscopic particles.

21. A method of upconverting infrared radiation to visible light, comprising:

focusing a selected band of infrared radiation on a first surface of a composite structure formed from mesoscopic particles embedded within a matrix of wide-bandgap material; and

,

illuminating the composite structure with optical pumping energy.

22. The method of claim 21, further comprising:

filtering ambient infrared radiation to form the selected ban of infrared radiation.

23. The method of claim 21, further comprising:

passing visible light from a second surface of the composite structure, opposite the first surface, to a visible light imaging circuit.

24. The method of claim 23, further comprising:

optically isolating the visible light imaging circuit from the optical pump energy.

25. The method of claim 23, wherein illuminating the composite structure with optical pump energy further comprises:

directly applying optical pumping energy to the surface of the composite structure.

26. The method of claim 23, wherein illuminating the composite structure with optical pump energy further comprises:

applying optical pumping energy to the second surface of the composite structure through a transparent layer.

27. The method of claim 23, wherein illuminating the composite structure further comprises:

forming a waveguide structure adapted to reflect the optical pumping energy through the composite structure; and

,

optically coupling a source for the optical pumping energy to the waveguide structure.

28. The method of claim 27, wherein the waveguide structure passes at least some portion of the visible light spectrum.

29. The method of claim 27, wherein the waveguide structure passes at least some portion of the infrared light spectrum.

30. The method of claim 21, wherein illuminating the composite structure with optical pumping energy further comprises:

providing an optical energy source adapted to tune-ably illuminate the composite structure with wavelength variable optical pumping energy; and

,

tuning the optical energy source between two or more optical pumping energy wavelengths.

31. A method of upconverting infrared radiation to visible light, comprising:

receiving infrared radiation on a first surface of a composite structure formed from mesoscopic particles embedded within a matrix of wide-bandgap material; and

,

selectively tuning an output wavelength for the visible light by varying the wavelength of optical pumping energy applied to the composite structure.

32. The method of claim 31, further comprising:

selectively filtering at least one of the infrared radiation and the visible light spectrum before receiving infrared radiation at a first surface of the composite structure.

33. The method of claim 31, where selectively tuning the output wavelength for the visible light comprises varying a tunable laser.

34. The method of claim 31, where selectively tuning the output wavelength for the visible light comprises selectively filtering the output of a broadband pumping laser before applying the optical pumping energy to the composite structure.

35. A composite structure comprising:

a layer of wide-bandgap material having mesoscopic sized particles embedded therein.

36. The composite structure of claim 35, wherein the mesoscopic sized particles are crystalline silicon particles and the wide-bandgap material is a silicon dioxide layer.

37. The composite structure of claim 35, further comprising:

a first reflective layer formed under the composite structure; and

,

a second reflective layer formed over the composite structure;

wherein the first and second reflective layers cooperate to form a waveguide structure around the composite structure.

38. The composite structure of claim 37, wherein the waveguide structure passes at least some portion of the visible light spectrum.

39. The composite structure of claim 37, wherein the waveguide structure passes at least some portion of the infrared light spectrum.

40. The composite structure of claim 37, wherein the waveguide structure is adapted to couple optical energy into the composite structure.

41. The composite structure of claim 35, wherein the interface states between the mesoscopic sized particles and the wide-bandgap material are cleanly formed and substantially without the presence of any intervening, unoccupied interface states.

42. The composite structure of claim 36, wherein the interface states between the crystalline silicon mesoscopic sized particles and the silicon dioxide layer are cleanly formed and substantially without intervening transitional silicon oxide materials.

43. The composite structure of claim 35, wherein the mesoscopic particles are formed from a silicon based material layer.

44. The composite structure of claim 43, wherein the silicon based material layer is doped with an isovalent element.

45. The composite structure of claim 43, wherein the silicon based material layer is doped with a rare-earth element.

46. A method of forming a steady-state, non-equilibrium distribution of free carriers, comprising:

providing a composite structure formed from silicon-based mesoscopic particles embedded within a matrix of wide-bandgap material; and

,

illuminating the composite structure with optical pumping energy;

wherein the silicon-based mesoscopic particles are doped with at least one isovalent element and a rare-earth element.

47. An infrared (IR) imaging system, comprising:

an optics subsystem focusing IR radiation on a first surface of a composite structure formed from a layer of wide band-gap material with mesoscopic sized particles embedded therein;

an optical pumping source applying optical pumping energy to the composite structure; and

,

a visible light imaging circuit receiving visible light from a second surface of the composite structure.

48. The infrared (IR) imaging system of claim 47, wherein the mesoscopic sized particles are crystalline silicon particles and the wide band-gap material is one selected from a group consisting of SiO₂, Si₃N₄, or amorphous silicon.

49. The infrared (IR) imaging system of claim 47, further comprising:

a first optical filter selectively passing a portion of the infrared radiation spectrum to the first surface of the composite structure.

50. The infrared (IR) imaging system of claim 49, further comprising a second optical filter isolating the visible light imaging circuit from the optical pump energy.

51. The infrared (IR) imaging system of claim 50, wherein the optical pumping source directly illuminates the first surface of the composite structure with optical pump energy.

52. The infrared (IR) imaging system of claim 50, wherein the optical pumping source illuminates the second surface of the composite structure.

53. The infrared (IR) imaging system of claim 50, further comprising:

a waveguide structure formed around the composite structure; and

wherein the optical pumping source is optically coupled to the composite structure through the waveguide structure.

54. The infrared (IR) imaging system of claim 53, wherein the waveguide structure passes at least some portion of the visible light spectrum.

55. The infrared (IR) imaging system of claim 53, wherein the waveguide structure passes at least some portion of the infrared light spectrum.

56. The infrared (IR) imaging system of claim 47, wherein the optical pumping source is a tunable optical energy source adapted to illuminate the composite structure with wavelength variable optical pumping energy.