Isolation of passive devices and integration with active devices in optical waveguiding circuits

• US 3,948,583 A
• Filed: 12/09/1974
• Issued: 04/06/1976
• Est. Priority Date: 12/09/1974
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Inventors: Tien, Ping King
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Levy, Stewart
• Application Number:
  US05/531,207
• Time in Patent Office: 484 Days
• Field of Search: 350/96 WG, 350/96 C
• US Class Current: 385/14
• CPC Class Codes: G02B 6/12004 Combinations of two or more optical elements
• CPC Class Codes: H01L 33/00 Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof H10K50/00 takes precedence; devices consisting of a plurality of semiconductor components formed in or on a common substrate and including semiconductor components having potential barriers, specially adapted for light emission H01L27/15; semiconductor lasers H01S5/00
• CPC Class Codes: H01S 3/0835 Gas ring lasers
• CPC Class Codes: H01S 5/026 Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers stabilisation of output H01S5/06
• CPC Class Codes: H01S 5/10 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 H01S5/20 takes precedence
• CPC Class Codes: H01S 5/1028 Coupling to elements in the cavity, e.g. coupling to waveguides adjacent the active region, e.g. forward coupled [DFC] structures
• CPC Class Codes: H01S 5/164 with window regions comprising semiconductor material with a wider bandgap than the active layer
• CPC Class Codes: H01S 5/2068 obtained by radiation treatment or annealing
• CPC Class Codes: Y10S 148/02 Contacts, special
• CPC Class Codes: Y10S 148/026 Deposition thru hole in mask
• CPC Class Codes: Y10S 148/072 Heterojunctions
• CPC Class Codes: Y10S 148/122 Polycrystalline

Abstract

The comprehensive large scale integration of thin-film optical circuits is made possible by a series of related developments. The key concept is the isolation of the high index substrate, necessary to active devices, wherever it is desired to have a passive device, by the interposition of an oxide layer such as SiO₂. It is preferred that the passive devices and the SiO₂ by amorphous. This new arrangement allows the use of discrete thin-film corner reflectors, instead of distributed feedback, in resonant active devices and wherever a reflector or beam-splitter is needed. Further, the active devices may be located photolithographically by etching windows in the SiO₂ layer. All of the active devices share a common active layer, which forms the passive devices wherever it extends between windows and simultaneously is the light guiding layer throughout.

Claims

1. An optical circuit comprising a substrate having a first index of refraction, an isolating layer disposed on said substrate and composed of material of much lower index of refraction than said first index, at least one passive optical device formed over said isolating layer, and at least one active optical device coupled with said passive optical device and formed at least in part in an aperture through said isolating layer, said active device including in a position under the aperture a substrate portion, the active and passive devices having the same potentially active waveguiding layer for a first frequency in common, said active optical device including means separate from said passive device for lower-frequency signal coupling with both the substrate portion and common layer portion of said active device.

2. An optical circuit according to claim 1 including output coupling means comprising a second isolating layer disposed over the waveguiding layer and a second waveguiding layer disposed over the second isolating layer, the first waveguiding layer being tapered in the region of a non-tapered portion of the second waveguiding layer and vice-versa with respect to orthogonal separation through said second isolating layer to provide a coupling between said waveguiding layers.

3. An optical circuit according to claim 1 in which the passive optical device comprises at least one corner reflector and the lower-frequency signal coupling means of the active device includes within coupling relationship to the substrate portion and the waveguiding layer at least two metallic signal coupling electrodes.

4. An optical circuit according to claim 3 in which the passive optical device includes a ring resonator having a light path from said corner reflector to a point of reentry to said active optical device.

5. An optical circuit according to claim 1 in which the active optical device and the passive optical device are separated by a transition region, said common waveguiding layer and said isolating layer in particular forming said transition region, said isolating layer being a layer of silver (Ag) tapered from substantially zero thickness to a full thickness between 2000 A and 3000 A.

6. An optical circuit according to claim 5 in which the silver layer is deposited to serve as a dielectric with an index of refraction of about unity.

7. An optical circuit according to claim 1 including at least one grating element formed in the isolating layer to facilitate coupling between active elements.

8. An optical circuit according to claim 7 in which a first active device comprises a ring laser, a second active device is included in the circuit and comprises a modulator, and the grating element is disposed in the isolating layer to provide coupling between said ring laser and said modulator.

9. An optical circuit according to claim 8 including a plurality of windows formed through the isolating layer, said active device being formed in part through said windows.