Integrated optical wavelength discrimination devices and methods for fabricating same

• US 5,784,507 A
• Filed: 04/26/1994
• Issued: 07/21/1998
• Est. Priority Date: 04/05/1991
• Status: Expired due to Fees

• Current Assignee: Datong Yang, James W. Holm-Kennedy, Tsang, Koon Wing
• Original Assignee: Datong Yang, James W. Holm-Kennedy, Tsang, Koon Wing
• Inventors: Holm-Kennedy, James W., Tsang, Koon Wing, Yang, Datong
• Primary Examiner(s): Lee, John D.
• Application Number:
  US08/312,286
• Time in Patent Office: 1,547 Days
• Field of Search: 385/14, 385/15, 385/24, 385/27, 385/31, 385/36, 359/885, 359/887, 359/890, 356/352, 356/416, 356/419, 250/227.18, 250/227.23, 250/227.24, 250/226
• US Class Current: 385/31
• CPC Class Codes: G01J 3/0256 Compact construction
• CPC Class Codes: G01J 3/0259 Monolithic
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G02B 2006/12109 Filter
• CPC Class Codes: G02B 2006/12173 Masking
• CPC Class Codes: G02B 2006/12195 Tapering
• CPC Class Codes: G02B 6/12007 forming wavelength selective elements, e.g. multiplexer, demultiplexer
• CPC Class Codes: G02B 6/1228 Tapered waveguides, e.g. integrated spot-size transformers for coupling with fibres G02B6/305

Abstract

A top incident spectrometer includes a first distributed wavelength wedge filter region of order n₁ that discriminates incoming radiation as a function of wedge location, at least one second wedge region order n₂ (which region may be a graded dielectric film), and an underlying detector array. In another embodiment, a second dielectric wedge element includes a Fabrey-Perot etalon, a wedge dielectric film, or a graded index film matching the second dielectric wedge region to an underlying substrate. One or more slopes associated with wedge elements may also be varied to alter filter characteristics. Spatial characteristics may further be modified by including a dielectric material whose dielectric constant varies as a function of location. Wedge filter crosstalk is minimized by partitioning a wedge dielectric region in the lateral dimension. Another embodiment provides an edge incident spectrometer including an optical waveguide or thin film structure whose spatial optical impedance varies as a function of position. Outcoupling of optical radiation occurs as a function of wavelength along the spectrometer propagation direction. Outcoupling of optical radiation may also be made to overlying structures, or to regions within a common, preferably solid state, structure. Wedge structures may further be combined to intentionally create gaps in the spectral transmission for a filter structure. A shadow masking fabricates thin film elements having spatially varying features. A material is deposited onto a substrate using an edge to provide a shadow mask affecting the deposition stream.

Claims

1. A substantially linear optical device (i.e., an optical device with locally linear regions, such as might be fabricated on a curved or flat substrate) with a filter plane defined by an x-axis and a y-axis, a normal defined by a z-axis and a lateral defined by said y-axis, comprising:

(a) an optical waveguide means for guiding propagating optical energy or light along an energy average propagation or vector direction parallel to said y-axis, said propagating light being character by an energy distribution and a bandwidth, and

(b) a wavelength selective filter comprising an outcoupling device for selecting wavelengths from said energy distribution of said propagating light and delivering spatially distributed outcoupled radiation charactertized by said selected wavelengths at separate outcoupling positions longitudinally along said wavelength means.

2. The optical device of claim 1 wherein said wavelength selective filter outcouples said outcoupled radiation away from said optical waveguide means, thereby generating said outcoupled radiation, in such a way that some of said selected wavelengths are spatially distributed with outcoupling positions that are a function of y-axis location along said waveguide means.

3. The optical device of claim 2 wherein said wavelength selective filter comprises an influencing thin film structure located proximally to said waveguide means, said influencing thin film structure presenting a spatially dependent optical impedance to said propagating optical energy or light.

4. The optical device of claim 3 wherein said influencing thin film structure comprises at least one film type selected from the group consisting of a graded dielectric constant thin film, a spatially graded dielectric film, an electro-optic film, a liquid crystal layer, a wedge shaped filter comprising an etalon thin film with at least one reflector film, a lossy film, a reflecting film, a conducting film, an optically active dielectric film and a spatially patterned film.

5. The optical device of claim 4 wherein said wedge shaped etalon thin film comprises a plurality of wedge shaped dielectrics to provide at least one transmission feature improvement of transmission features of said optical device, said at least one transmission feature improvement being selected from the group consisting of improving transmission coefficient, increasing spectral range, decreasing bandwidth and polarization.

6. The optical device of claim 5 wherein said plurality of wedge shaped dielectrics comprise different wedge dielectric films with spatially dependent thicknesses described by different orders.

7. The optical device of claim 6, wherein said orders and thickness are chosen to provide improved spectrometer performance, wherein said performance is at least one of (a) output coupling efficiency, (b) spatial bandwidth, (c) frequency bandwidth, (d) spectral range and (e) system transmission coefficient.

8. The optical device of claim 5 wherein said at least one transmission feature is selected from a group consisting of a plurality of wedge shaped dielectrics to provide at least one transmission feature improvement of transmission features of said optical device, said at least one transmission feature improvement being selected from the group consisting of improving transmission coefficient, increasing spectral range, decreasing bandwidth and polarization.

9. The optical device of claim 4 wherein a component of said outcoupled radiation has an outcoupling direction that is along the z-axis and away from said influencing thin film structure.

10. The optical device of claim 9 wherein said outcoupled light has an outcoupling direction that is to the side and out of said influencing thin film structure.

11. The optical device of claim 4 wherein a portion of said outcoupled light characterized by particular wavelengths of said selected wavelengths is reinserted as reinserted light into a second optical guide to combine with a second propagating optical wave.

12. The device of claim 11 wherein said second propagating optical wave is selected from the group consisting of at least a part of said propagating light in said optical waveguide means, a different optical wave at a second wavelength identical to one of said particular wavelengths, and a different optical wave at a third wavelength different from said particular wavelengths, said device thereby providing at least one function arising from said combining of said reinserted light with said second propagating optical wave selected from the group consisting of a phase shift, an amplitude change, an interference, a beat, a hologram and diffraction.

13. The optical device of claim 4 wherein said wedge shaped filter has a spatial gradient causing a thickness variation that takes said wedge filter through several different orders such that the wavelength range of said radiation is replicated along said y-axis of said wedge shaped filter and each successive replication has a different bandwidth parameter.

14. The optical device of claim 3 wherein said influencing thin film structure further comprises a plurality of wedge shaped etalon thin films providing at least one useful function selected from the group consisting of beam splitting, phase control, switching of outcoupling radiation, amplitude control of outcoupling radiation, delivery of selected wavelengths of optical radiation to a separate regions for additional optical processing, holographic function, interference function, propagation direction alteration, delivery to a different optical waveguide, radiation intensity increase, radiation intensity decrease, combining outcoupling radiation with a second optical beam, subtracting outcoupling radiation from a second optical beam, adding outcoupling radiation to a second optical beam, amplifying, mixing and influencing or controlling optical functions of other optical devices.

15. The optical device of claim 3 wherein a component of said outcoupled radiation has an outcoupling direction that is along the z-axis and away from said influencing thin film structure.

16. The optical device of claim 3 wherein a component of said outcoupled radiation has an outcoupling direction that is selected from the group along said z-axis, and edge.

17. The optical device of claim 3 wherein said outcoupled radiation is coupled to at least one item selected from the group consisting of a second optical waveguide, a detector, a hologram device, a diffraction device, a filter device, an optical wavelength selecting device, a microlens, a prism, a reflector, a second thin film structure with or without parameter spatial variation and an optical readout device.

18. The optical device of claim 3 wherein said outcoupled light has an outcoupling direction that is to the edge of said influencing thin film structure.

19. The optical device of claim 1 wherein said wavelength selective filter has a spatially varying property that varies as a function of location along said energy average propagation direction.

20. The optical device of claim 19 wherein said spatially varying property influences outcoupling of said outcoupled radiation as a function of said selected wavelengths such that at least two of said wavelengths couple out at different locations along said optical waveguide means thereby providing a spectrometer function.

21. The optical device of claim 20 wherein said optical waveguide means comprises at least one waveguide member selected from a group consisting of a dielectric film whose thickness varies as a function of location in at least one dimension, a dielectric film whose dielectric constant varies in at least one dimension, an optical slab waveguide, a single mode thin film optical waveguide, a multimode film optical waveguide, a dielectric optical waveguide, a fiber optic cable, a waveguiding substrate and a waveguiding substrate film.

22. The optical device of claim 21 wherein said optical waveguide is imbedded in a dielectric material.

23. The optical device of claim 21 wherein the amount of said light outcoupled at each location along an exit interface for said outcoupling device is controlled by an impedance function designed into said outcoupling device and provided by a thin film wedge filter provided on said outcoupling device.

24. The optical device of claim 23 wherein said waveguide is a slab waveguide, a dielectric waveguide or a planar system.

25. The optical device of claim 21 further comprising an optical switching device in a configuration selected between said outcoupling device or along said optical waveguide, wherein said optical switching device provides at least one feature selected from the group consisting of AC modulation of said optical energy or light, preselected and controlled removal of particular bands of said bandwidth, introduction of desired phase, introduction of desire attenuation of said outcoupled radiation, introduction of control of desired amplitude of said outcoupled radiation, introduction of desired phase of said outcoupled radiation and introduction of desired polarization.

26. The optical device of claim 1 wherein said wavelength selective filter comprises a plurality of filter members, each of said filter members spatially distributing incoming optical radiation;

such that said filter members split said incoming optical radiation into a plurality of transmitted beams.

27. The optical device of claim 26, wherein said filter members have spectral characteristics that are identical, thereby providing said transmitted beams with identical optical characteristics.

28. The optical device of claim 1 wherein said wavelength selective filter comprises a dielectric wedge element with a step discontinuity in said dielectric'"'"'s thickness, said step discontinuity producing a discontinuity in optical impedance of said wedge, thereby causing a discontinuity in wavelengths of radiation outcoupled by said wavelength selective filter.

29. The optical device of claim 1 wherein said wavelength selective filter comprises a wedge shaped impedance element disposed above said y-axis of said optical waveguide means and an intermediate layer selected from the group consisting of an optical reflector, voltage controlled absorber or voltage controlled optical switch interposed between said wedge shaped impedance element and said optical waveguide means;

said intermediate layer thereby controlling the outcoupling from said impedance element and said waveguide means and providing at least one optical processing function selected from the group consisting of attenuation, phase shifting, amplitude and frequency modulation of said outcoupled light.

30. The optical device of claim 1 further comprising a graded dielectric region between said waveguide means and said wavelength selective filter to create more normal incidence on said wavelength selective filter and altered wavelength discrimination characteristics.

31. The optical device of claim 1 wherein said wavelength selective filter is a stretch filter comprising a first filter region with a first slope and a second filter region with a second slope, said second slope being less than said first slope;

such that wavelengths of optical radiation exiting said filter are spread out along said y-axis of an associated detector.

32. The optical device of claim 1 wherein said wavelength selective filter outcouples said outcoupled radiation away from said optical waveguide means, thereby generating outcoupled light or radiation.

33. The optical device of claim 32 wherein said wavelength selective filter'"'"'s orientation with respect to said waveguide means is selected from a group consisting of an extension of said waveguide means or adjacent to said waveguide means.

34. The optical device of claim 32 wherein said outcoupled light is coupled by said wavelength selective filter to at least one structure selected from a group consisting of a thin film, a detector, an optical waveguide, a diffracting structure, a holographic structure, a fiber optic cable device, a wavelength sating device, a wavelength multiplexing device, a distributed wavelength outcoupling device, a distributed wavelength incoupling device, a dielectric medium, air, and free space.

35. The optical device of claim 1 wherein said wavelength selective filter incorporates at least one distributed wavelength filter.

36. The optical device of claim 35 wherein said distributed wavelength filter comprises at least one wedge filter component.

37. The optical device of claim 1, wherein said optical waveguide means is a non-rectilinear structure of substantially planar local waveguide regions, said y axis therefore being a local y axis defining said energy average propagation direction in each of said local waveguide regions.

38. The optical device of claim 1, wherein said wavelength selective filter comprises a combination of wedge structures and provides at least one optical system characteristic selected from the group consisting of a large spectral range, a non-continuous range of output wavelengths, more than one region of outcoupling radiation, improved outcoupling efficiency, a distribution of outcoupling coefficients, a distribution of outcoupling frequency bandwidths, a distribution of spectral ranges, a distribution of intensity amplitudes, repetition of outcoupled optical radiation, a distribution of bandwidths and a distribution of spatial bandwidths.

39. The optical device of claim 38 further comprising a graded dielectric film situated between one of said wedge structures and said optical waveguide means, said one wedge structure being a wavelength discriminating wedge structure, said graded dielectric film influencing said propagating light to generate a third light signal with a third propagation direction more normal to said wavelength discriminating wedge structure than light otherwise exiting said waveguide means and coupling said third light signal to said wavelength discriminating wedge structure, thereby altering wavelength discrimination characteristics of said one wedge structure.

40. The optical device of claim 39, further comprising a first thin film structure adjacent said optical waveguide means where said first thin film structure assists in outcoupling of said propagating light and assists in coupling said propagating light to an optical detection device.

41. The optical device of claim 40 wherein a plurality of wavelength discriminating and spatially separating second thin film structures are mounted on said optical waveguide means to provide optical radiation outcoupling from said waveguide means through each of said second thin film structures.

42. The optical device of claim 41 wherein at least two of said second thin film structures are adjacent to said optical waveguide means in at least one configuration selected from the group consisting of two identical said second thin film structures, two said second thin film structures providing different bands of output optical radiation with at least one different characteristic selected from the group consisting of different outcoupling efficiencies and bandwidths.

43. The optical device of claim 42 wherein said wavelength selective filter is a wedge dielectric structure that has thickness related properties of multiple orders along its surface leading to coupling of at least some of the same wavelengths at more than one location along the optical propagation direction.

44. The optical device of claim 43 wherein said outcoupled optical radiation at two different wavelengths exiting said optical waveguide means at two different locations maintains constant at least one parameter selected from a group consisting of amplitude relative to the propagating amplitude, spatial wavelength, frequency bandwidth where the amplitude of the emitted radiation is the same for the same percentage of the incident radiation at for at least two different wavelengths at least two said locations.

45. The optical device of claim 43 wherein said wedge dielectric structure includes higher orders and allows the same wavelength centered radiation band to exit said optical wavelength means at different spatial regions.

46. The optical device of claim 42 wherein said second thin film structure includes at least two dielectric, wavelength discriminating films which when superimposed constrain the exiting radiation to be of a substantially non continuous range of wavelengths with at least two wavelengths of exiting radiation being significantly different and spatially separated.

47. The optical device of claim 42 wherein said two second thin film structures provide different bands of output optical radiation with at least one different characteristic selected from the group consisting of different outcoupling efficiencies and bandwidths.

48. The optical device of claim 1 further comprising at least one incoupling device selected from a group consisting of a diffraction grating, a holographic structure, direct incidence onto the optical waveguide means, a dielectric waveguide a prism, a groove, an optical device incorporating at least one lens, a dielectric waveguide, a thin film coating, a textured surface, and a graded index lens, such that said incoupling device introduces/incouples said optical energy or light into said waveguide means.

49. An optical energy transfer system comprising:

(a) an optical waveguiding structure to carry propagating optical energy or light, said propagating light including at least one optical carrier, each of said optical carriers having different carrier wavelengths;

(b) at least one wedge filter structure, each of said wedge filter structures having a first and second surface, said first surface located adjacent said optical waveguiding structure and performing an optical function selected from the group consisting of outcoupling said propagating energy from said optical waveguiding structure or incoupling incident light illuminating said second surface into said optical waveguiding structure, said wedge filter structures performing said outcoupling being called outcoupling structures, said wedge filter structures performing said incoupling being called incoupling structures.

50. The optical energy transfer system of claim 49 further comprising an optical receiving structure located adjacent to said second surface of at least one of said outcoupling structures, said at least one of said outcoupling structures thereby outcoupling at least one of said optical carriers from said optical waveguiding structure into said optical receiving structure.

51. The optical energy transfer system of claim 49 wherein said optical waveguiding structure includes at least one optical processing structure selected from the group consisting of at least one integrated circuit, a multichip circuit or discrete electronic components, said optical processing structure generating a second light signal from said propagating light, said second light signal propagating in said optical waveguiding structure.

52. The optical energy transfer system of claim 51 wherein said outcoupling structures and said incoupling structures are located in at least one processing configuration selected from the group consisting of said outcoupling and incoupling structures located (1) on one said integrated circuit, (2) on different ones of said integrated circuits, (3) on different ones of said electronic components and (4) on different chips of said multichip circuit.

53. The optical energy transfer system of claim 52 wherein at least one of said outcoupling and incoupling structures located on one said integrated circuit is for receiving/transmitting off said integrated circuit at least one of said optical carriers, said outcoupling and incoupling integrated structures located at different spatial locations of said optical waveguiding structure.

54. The optical energy transfer system of claim 49 wherein said incident light includes one or more optical carriers, each of said optical carriers having at least one wavelength, said wedge filter structure incoupling at least one of said optical carriers into said optical waveguiding structure.

55. The optical energy transfer system of claim 54 wherein said wedge filter structure also performs an optical processing function on said at least one optical carrier incoupled by said wedge filter structure.

56. The optical transfer system of claim 54 including an optical receiving structure selected from the group consisting of a second wedge filter, a second optical waveguide, at least one detector, a holographic structure, a thin film structure, an attenuating structure, a wavelength shifting structure, an amplifying structure or a mixing structure.

57. The optical energy transfer system of claim 49 wherein said optical transfer system provides at least one optical processing function selected from the group consisting of demultiplexing or multiplexing said incoupled and outcoupled light.