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Laser Micro-Fabrication of Waveguide Devices

IP.com Disclosure Number: IPCOM000034732D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 3 page(s) / 38K

Publishing Venue

IBM

Related People

Fan, B: AUTHOR [+4]

Abstract

A technique is described whereby high quality waveguide structures are fabricated with laser micro-fabrication techniques. The concept concentrates on the fabrication of Ti:LiNbO3 waveguides including straight lines, Y-branches, curves and similar active optical devices, utilizing direct patterning of "spin-on" organometallic inks. The process steps used to fabricate titanium lithium niobate waveguide devices is similar to those used in the fabrication of semiconductor devices, namely, the deposition of a blanket film of Ti, coating with resist, exposure through a mask, development of a resist, etching of the Ti, and diffusion in a controlled atmosphere. However, the steps required to delineate the waveguide features is time consuming and is usually gated by the mask.

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Laser Micro-Fabrication of Waveguide Devices

A technique is described whereby high quality waveguide structures are fabricated with laser micro-fabrication techniques.

The concept concentrates on the fabrication of Ti:LiNbO3 waveguides including straight lines, Y-branches, curves and similar active optical devices, utilizing direct patterning of "spin-on" organometallic inks. The process steps used to fabricate titanium lithium niobate waveguide devices is similar to those used in the fabrication of semiconductor devices, namely, the deposition of a blanket film of Ti, coating with resist, exposure through a mask, development of a resist, etching of the Ti, and diffusion in a controlled atmosphere. However, the steps required to delineate the waveguide features is time consuming and is usually gated by the mask. This is particularly true when the active area of research is induced with the geometry of the waveguides, such as the branching angles, radius of curvature, and the distance between guides. The concept described herein addresses the fabrication steps needed to produce waveguides rapidly through the use of laser micro-fabrication techniques. In prior art, laser photo-deposition of Ti from TiCl4 has been used and only to fabricate straight line guides [1]. However, the technique required the use of hard-won deep ultraviolet photons (frequency doubled argon), corrosive gases (TiCl4) and a gas cell. The concept described herein improves on this prior-art process by using a laser micro-fabrication technique based on the pyrolytic decomposition of organometallic inks, using visible light for the rapid fabrication of LiNbO3 waveguide structures. The waveguide fabrication technique consists of spinning a Ti-bearing ink onto a pre-cleaned LiNbO3 crystal. The coated crystal is then baked. Typical Ti film thicknesses obtained at various spin speeds are shown in the following table:

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After spinning, the baked sample is placed on a precision computer-controlled x-y stage. An apertured beam of light from a continuous wave (CW) argon ion laser is imaged on the substrate with a standard 32x microscope objective of NA 0.60. The laser energy is used to locally heat (within the micron-size area illuminated by the aperture) the Ti-bearing ink to above its decomposition temperature (400 to 500oC). The decomposition products consist of volatile gases (organics, sulfides, etc.) and a non-volatile residue which forms a titanium oxide film. By moving the table (from 40 to 280 mm/s) and adjusting the size of the aperture (from 5 to 50 mm), the entire pattern of titanium oxide is delineated by the use of this thermally activated chemical reaction. The titanium oxide is believed to be f...