We have developed a hybrid lithography process necessary to fabricate a vertical optical coupler and an array of waveguide structures using the same buffer coat material on a single substrate. A virtual vernier scale built into the process enables precise alignment of both structures.
A polymer-based flat, flexible and parallel optical interconnect has become an attractive approach for short-range data
transfer. For such a device, a low cost fabrication technique is required for light couplers to redirect light from source to
waveguides. Recently, we demonstrated a mask-less gray scale lithography process, which used a CMOS compatible
polymer for a 45-degree mirror coupler. Polymer materials such as epoclad and AP2210B can be used to fabricate
flexible substrates and waveguides, respectively. We propose an all-photopolymer lithography process to fabricate the
flexible and parallel optical interconnect in conjunction with the mirror couplers. In the process, a buried polymer
structure is used to precisely align the mirror coupler to waveguides, which make it possible to avoid an additional
metallization process. However, the contrast of such buried fiducial mark is low since such the structure is a phase
structure. As a result, it is not feasible to use the buried polymer structure as an alignment mark with conventional
amplitude based imaging modalities. To increase the contrast of these buried alignment marks, we propose a feature
specific alignment system for which the shape and depth of the buried alignment marks are optimized for phase-based
imaging such as phase contrast and Schlieren imaging. Our results show that an optimized alignment mark provides a
significant contrast enhancement while using a phase contrast imaging system compared to that of a conventional
imaging system. In addition, we have fabricated an optimized alignment mark specifically for use with a Schlieren
imaging system.
We report a CMOS compatible fabrication and optical characterization of the micrometer scale optical coupler, a 45°
mirror-based optical coupler for inter-layer optical coupling. A newly proposed mask-based and mask-less hybrid
lithography process enables accurate surface profile of the micrometer sized 45° mirror by using a CMOS compatible
buffer coat material. Surface profile inspected by an optical interferometry agrees well with SEM based inspection
results. Experimental and theoretical results for routing and coupling of laser beam in 90° will be discussed.
We show the design for a laser scanning microscopy defect detection system based upon the idea that the light can reflect off a photoresist-laden fused-silica sample containing defects, allowing height and depth information to be obtained through changes in light intensity. Image registration using predefined points is employed. Image processing techniques involving median and deconvolution filtering are used. Results show that the 2.1-μm resolution of these defects is obtainable, and receiver operating characteristic curves are used for quantifying results. Discriminabilities of 0.73 are achieved. Preliminary results for larger-array patterns through stitching processes are also shown.
We utilized a hybrid lithography technique in the fabrication of a 45 degree micro mirror coupler to be used for a 3D
optical circuit. The hybrid process combines traditional mask-based lithography techniques with mask-less methods.
The result is a CMOS compatible process that can be used for fabrication of integrated micro-optics.
We demonstrated a 45 degree micro mirror by a direct laser writing method. A flat, smooth and clearly defined mirror surface has been fabricated despite of the finite size and long tail of the point spread function of the exposure tool.
We have characterized a photoresist used for the fabrication of gray-scale diffractive optic elements in terms of Dill's and Mack's model parameters. The resist model parameters were employed for the simulations of developed resist profiles for sawtooth patterns executed by solving the Eikonal equation with the fast-marching method. The simulated results were shown to be in good agreement with empirical data.
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