News Column

Patent Issued for Photonic Integrated Circuit Having a Waveguide-Grating Coupler

June 25, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- Alcatel Lucent (Paris, FR) has been issued patent number 8750654, according to news reporting originating out of Alexandria, Virginia, by VerticalNews editors.

The patent's inventors are Dupuis, Nicolas (New York, NY); Doerr, Christopher R. (Middletown, NJ).

This patent was filed on June 17, 2013 and was published online on June 10, 2014.

From the background information supplied by the inventors, news correspondents obtained the following quote: "The present invention generally relates to optical communication equipment and, more specifically but not exclusively, to optical devices for coupling light into and out of photonic integrated circuits.

"This section introduces aspects that may help facilitate a better understanding of the invention(s). Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

"Photonic integrated circuits (PICs) are used for various applications in telecommunications, instrumentation, and signal-processing fields. A PIC typically uses optical waveguides to implement and/or interconnect various on-chip components, such as optical switches, couplers, routers, splitters, multiplexers/demultiplexers, modulators, amplifiers, wavelength converters, optical-to-electrical (O/E) and electrical-to-optical (E/O) signal converters, etc. A waveguide in a PIC is usually an on-chip solid light conductor that guides light due to an index-of-refraction contrast between the waveguide's core and cladding.

"For proper operation, a PIC typically needs to efficiently couple light between an external optical fiber and one or more of on-chip waveguides. An exemplary grating coupler that can be used for this purpose is disclosed, e.g., in U.S. Pat. No. 7,065,272, which is incorporated herein by reference in its entirety. However, one problem with some grating couplers is that they work well only when implemented using materials that provide a relatively high index-of-refraction contrast between the core and both the upper and lower cladding layers, whereas certain active optical elements of the PIC require the use of materials that can provide only a relatively low index-of-refraction contrast."

Supplementing the background information on this patent, VerticalNews reporters also obtained the inventors' summary information for this patent: "Advantageously, some embodiments of the waveguide-grating couplers disclosed herein do not have low light-coupling efficiencies of prior-art waveguide-grating couplers and are convenient for integration into photonic integrated circuits (PICs) having III-V semiconductor-based active optical elements. In particular, problems of the prior art are addressed by providing a waveguide-grating coupler having two evanescently coupled waveguides. The first waveguide is fabricated using materials suitable for manufacturing active optical elements, and the second waveguide is fabricated using materials capable of providing a relatively high index-of-refraction contrast for the constituent waveguide grating.

"According to one embodiment, provided is an apparatus having (i) a first optical waveguide being supported on a surface of a substrate; (ii) a second optical waveguide being supported over the surface; (iii) an optical coupler being supported over the surface and optically coupling the first and second waveguides; and (iv) a waveguide grating being supported over the surface and being adapted to transfer optical power between one or more waveguide modes of the second waveguide and an optical beam formed by or applied to the waveguide grating. The second waveguide has an offset-transition region for which a core of the second waveguide has an offset distance that gradually changes from a first distance corresponding to the coupler to a different second distance.

"According to another embodiment, provided is a photonic integrated circuit (PIC) having (i) a substrate; (ii) an optical signal-processing (OSP) circuit being supported on the substrate and having at least one active optical element; (iii) a first optical waveguide being optically coupled to the active optical element; (iv) a second optical waveguide having a waveguide grating adapted to transfer optical power between one or more waveguide modes of the second optical waveguide and an optical beam formed by or applied to the waveguide grating; and (v) an optical coupler that couples the first and second waveguides only via evanescent fields. The second optical waveguide has an offset-transition region, within which a core of the second optical waveguide has an offset distance with respect to the substrate that gradually changes from a first distance to a different second distance.

"According to yet another embodiment, provided is a method of fabricating an optical device having the steps of: (A) providing a substrate having a first optical waveguide thereon, the first optical waveguide having a cladding layer with a wedge-like portion; (B) forming a core of a second optical waveguide on the wedge-like portion and an exposed portion of the cladding of the first waveguide; and (C) forming an array of cavities in the core of the second optical waveguide to define therein a waveguide grating."

For the URL and additional information on this patent, see: Dupuis, Nicolas; Doerr, Christopher R.. Photonic Integrated Circuit Having a Waveguide-Grating Coupler. U.S. Patent Number 8750654, filed June 17, 2013, and published online on June 10, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8750654.PN.&OS=PN/8750654RS=PN/8750654

Keywords for this news article include: Electronics, Alcatel Lucent, Signal Processing.

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Source: Electronics Newsweekly


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