Browse Prior Art Database

Offset Laser to Groove Waveguide Coupler

IP.com Disclosure Number: IPCOM000089175D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 3 page(s) / 119K

Publishing Venue

IBM

Related People

Comerford, LD: AUTHOR [+2]

Abstract

A GaAs laser array is coupled to channel groove optical waveguides in silicon by mounting the laser source directly onto the silicon substrate adjacent to the waveguides and deflecting the laser output downward with a first reflecting surface and then laterally with a second reflecting surface into the waveguides.

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Offset Laser to Groove Waveguide Coupler

A GaAs laser array is coupled to channel groove optical waveguides in silicon by mounting the laser source directly onto the silicon substrate adjacent to the waveguides and deflecting the laser output downward with a first reflecting surface and then laterally with a second reflecting surface into the waveguides.

Fig. 1 illustrates the concept. A small, right angle prism with its hypotenuse coated with a metallic reflective film is positioned in front of the laser to deflect the light downward. The waveguides are fabricated along the (110) direction in (100) oriented silicon. Etching grooves along this direction produces smooth, low-loss waveguides which terminate with a smooth surface tilted at phi = 35.3 degrees. If the prism angle theta = phi and the waveguide end terminations are also coated with a metallic reflective coating, then the light deflected down into the waveguides is redirected along the axes of the waveguides. The waveguide numerical aperture must exceed the laser divergence in the prism for the guide to capture the light. For example, with an SiO(2) cladding in the guide, n(2) = 1.45, a laser with a divergence angle (fwhm) of 40 degrees, and a prism of index n(p) =
1.5, the lightguide index n(1) must be greater than 1.49, which allows a good match to the prism. The prism dimensions are the same as the dimensions of the triangle formed by the end termination of the waveguide and may be fabricated to the d...