Optical coupler having multiple thin-film layers with spatially varying optical …
WO2019136114A1
Abstract
A beam-steering device, such as a steerable electro-evanescent optical refractor, has a planar waveguide region between an incoupler and an outcoupler. Each region has a substrate and a plurality of thin-film layers, such as a subcladding layer over the substrate and a core layer over the subcladding. For at least one coupler, at least two of the thin-film layers have spatially varying optical thicknesses due to, for example, the subcladding and the core being tapered with decreasing thicknesses from the waveguide region to the corresponding facet of the 8 S device. Alternatively, spatially varying optical thickness can be achieved by spatially varying a layer's refractive index. The coupler has a FWHM bandwidth and a FWHM coupling angle tolerance that greatly exceed those achievable using corsventional Ulrich couplers.
Description (excerpt)
OPTICAL COUPLER HAVING MULTIPLE THIN-FILM LAYERS WITH SPATIALLY VARYING OPTICAL THICKNESSES Cross-Reference to Related Applications [0001] This application claims the benefit of the filing dates of U.S. provisional application no. 62/613,190, filed on 01/03/19; U.S. provisional application no. 62/613,185, filed on 01/03/18; and U.S. provisional application 62/635,952, filed CHI 02/27/18, the teachings of all of which are incorporated herein by reference in their entirety. Statement of Government In terest [0002] Under paragraph 1(a) of Executive Order 10096, the conditions under which this invention was made entitle the Government of the United States, as represented by the Secretary of the Navy, to an undivided interest therein on any patent granted thereon by the United States. This and related patents are available for licensing to qualified licensees. BACKGROUND Field of toe invention [0003] The present invention relates to non-mechanical beam-steering devices and optical systems using such devices and, more particularly but not exclusively, to steerable electro- evanescent optical refractors (SEEORs) and optical systems using SEEQRs for nonmechanical beam steering (NMBS) and other applications. Description of the Related Art [0004] This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art. [0005] Thin-film slab waveguides are utilized for a variety of applications, including refractive non-mechanical beam steering (NMBS). Typically, these systems are coupled using either external prisms or faceted substrates having a tapered subdadding layer, referred to herein as Ulrich couplers. See R. Ulrich, Optimum excitation of optical surface waves," Journal of the Optical Society of America 61(11), 1467-1477 ( 1971 ) , the teachings of which are incorporated herein by reference. In both cases, the fundamental method of operation is sirni!ar a tapered region creates a spatially varying interaction between the waveguide core and tiie prism/substrate. In prism-type optical couplers, a tapered air gap is created using either spacers or pressure to bend the prism substrate, while Ulrich couplers have a tapered subdadding. At a specific point along the tapered region, a phase-matching condition is reached between a guided mode in the coupler's waveguide and the incident light and coupling into the waveguide is achieved. In such devices, the phase-matching condition is achieved around extremely narrow poles in a calculated resonant term that is dependent on several features of the coupler structure and the interaction of the incident beam with the coupler. [0006] FIG. 1A is a cross-sectional side view of a conventional non-mechanical beamsteering (BS) device 100 of the prior art, and FIG. 1B is a perspective view of the top of the conventional BS device 100 of FIG. 1 A, and. The conventional BS device 100 has a planar waveguide region 104 separating a tapered (i.e., faceted), Ulrich incoupler 102 and a tapered, Ulrich outcoup!er 106. FIG. 1C is a magnified cross-sectional side view of the Ulrich incoupler 102 and pat of the waveguide region 104 of the conventional BS device 100 of FIGs. 1A and 1B. [0007] As represented in FIGs. 1 A and 1C, each of the waveguide region 104 and the couplers 102 and 106 has a substrate 120, a subcladding layer 122 over the substrate 120, a core layer 124 over the subciadding 122, a liquid crystal (LC) layer 126 functioning as a top cladding layer over the core 124, and a cover glass layer 128 over the LC layer 126 that retains and protects the LC layer 126. As shown in FIGs. 1A and 1B, formed within the glass layer 128 on top of the LC layer 126 are horizontal-steering electrodes 130 over the waveguide region 104 and a vertical-steering electrode 132 over the outcoupler 106. [0008] As shown in FIGs. 1A and 1C, all of the layers within the waveguide region 104 have uniform thicknesses. For the couplers 102 and 106, the substrate 120 and the subcladding 122 are both tapered with thicknesses that decrease from the side abutting the waveguide region 104 to the input and output tips 108 and 110, respectively, of the conventional BS device 100, while the core 124 has the same uniform t
Filing details
- Inventors
- Robel Y. Bekele
- Assignee
- … America, As Represented By The Secretary Of The Navy Naval Research Laboratory
- Filed
- Jan 3, 2019
- Granted
- Application pending
Bibliographic data and excerpted text sourced from Google Patents (public record) as part of IP TechMatch's current-filings monitor. This filing is not part of the 2019 historical archive. For the authoritative full text, drawings, and legal status, see the source links above or consult USPTO records directly.