Publication Date

2015-07-02

Availability

Open access

Embargo Period

2015-07-02

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Electrical and Computer Engineering (Engineering)

Date of Defense

2015-06-03

First Committee Member

Michael R. Wang

Second Committee Member

Sung Jin Kim

Third Committee Member

Onur Tigli

Fourth Committee Member

Ali Ghahremaninezhad

Fifth Committee Member

Olga Korotkova

Abstract

Optical interconnects is a promising technique to boost the speed of electronic systems through replacing high speed electrical data buses using optical ones. Optical coherence tomography is an attractive imaging technique that has been widely used in medical imaging applications with capability of high resolution subsurface cross sectional imaging in living tissues. Both the optical interconnects and the optical coherence tomography imaging may benefit from the use of integrated optics technology in particular polymer waveguides that can be designed and fabricated to improve the device capability, system compactness, and performance reliability. In this dissertation, we first present our innovative design and realization on the polymer waveguides with 45° integrated mirrors for optical interconnects using the vacuum assisted microfluidic (VAM) soft lithography. VAM is a new microfluidic based replication technique which can be utilized to improve the performance of imprinted devices by eliminating the residue planar layer and accomplish complex devices incorporating different materials in the same layer. A prism-assisted inclined UV lithography technique is introduced to increase the slanted angles of the side walls of the microstructures and to fabricate multidirectional slanted microstructures. It is also used to fabricate 45° integrated mirrors in polymer waveguides to support surface normal optical coupling for optical interconnects. A dynamic card-to-backplane optical interconnects system has also been demonstrated based on polymer waveguides with tunable optofluidic couplers. The operation of the tunable optofluidic coupler is accomplished by controlling the position of air bubbles and index matching liquid in the perpendicular microfluidic channel for refractive index modulation. The dynamic activation and deactivation of the backplane optofluidic couplers can save the optical signal power. 10 Gbps eye diagrams of the dynamic optical interconnect link have been demonstrated showing the needed high performance optical interconnection. The design and fabrication of planar concave grating (PCG) wavelength demultiplexer on SU-8 polymer waveguides is presented for wavelength division multiplexing system to further support optical interconnection applications. The PCG wavelength demultiplexers with a flattened spectral response are accomplished by innovative design of a multi-mode interference coupler as input to the PCG. The mode field distribution at the PCG planar input is controlled by adjusting the width of an input waveguide taper connected to multi-mode interference coupler. By extending the channel number and density, the PCG wavelength demultiplexer can become a compact optical spectrometer which could be used to realize a portable optical coherence tomography system. The design of a 200-channel and a 1024-channel PCG spectrometers with low crosstalk, small channel loss, good uniformity, and chip size of 3 cm × 3 cm and 8 cm × 8 cm, respectively, has been performed. An alternative quicker solution using cylindrical optics with a vertical beam size of about 3 mm in the diffraction plane is also demonstrated to achieve a compact optical spectrometer, which is capable of supporting optical coherence tomography subsurface imaging applications.

Keywords

Integrated Optics; Polymer Waveguide; Optical Interconnection; Soft Lithography; Planar Concave Grating; Integrated spectrometer

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