Photomask / Direct Write Lithography Documents

High power single mode, tunable, narrow linewidth semiconductor lasers in the 2.05-μm wavelength region are needed for coherent detection optical remote sensing applications. 2.05-μm Fabry Perot (FP) and distributed feedback (DFB) ridge waveguide lasers fabricated from epitaxially grown InGaAsSb/AlGaAsSb/GaSb and InGaAs/InP hetero-structures are reported. This work is part of a NASA Earth Science Enterprise Advanced Technology Initiatives Program research effort to develop semiconductor laser reference oscillators for optical remote sensing from Earth orbit. In particular, local oscillators provide the frequency reference required for active spaceborne optical remote sensing concepts that use heterodyne (coherent) detection. The two most prominent Earth observation applications for this technology are Doppler LIDAR wind sensing and tropospheric carbon dioxide measurement by laser absorption spectrometry, the currently favored operational wavelength for both of which is 2.05 μm.

Annual Report 2002

Topology optimization is used to design a planar photonic crystal waveguide component resulting in significantly enhanced functionality. Exceptional transmission through a photonic crystal waveguide Z-bend is obtained using this inverse design strategy. The design has been realized in a silicon-on-insulator based photonic crystal waveguide. A large low loss bandwidth of more than 200 nm for the TE polarization is experimentally confirmed.

An 8-wavelength DBR array for narrow channel wavelength division multiplexing (WDM) has been fabricated with a new technique for printing first-order Bragg gratings using a phase mask and a conventional incoherent source.

We describe the nanofabrication of subwavelength, binary lenses in GaAs for operation in the infrared. Subwavelength surface relief structures create an artificial material with an effective index of refraction determined by the fill factor of the binary pattern and can be designed to yield high-efficiency diffractive optical elements.

We describe the microfabrication of an extremely compact optical system as a key element in an integrated capillary channel electrochromatograph with fluorescence detection.

Complex computer generated phase holograms (CGPHs) have been fabricated in polymethyl methacrylate (PMMA) by partial exposure and subsequent partial development. The CGPH was encoded as a sequence of phase delay pixels and written by e-beam (JEOL JBX-5DII), a different dose being assigned to each value of phase delay.

A new three-dimensional photonic crystal structure is designed to simplify fabrication. A calculation of the band structure predicts that this photonic crystal has a complete photonic band gap in all directions. The entire three-dimensional periodic structure, except for the vertically drilled holes, is formed by automatic shaping during bias sputtering deposition.

It is important to fabricate high density and high uniformity nano-structures for the realization of quantum wire lasers. In this work, 1.5µm-wavelength GaInAsP/InP quantum wire lasers were fabricated by electron beam (EB) lithography, and wet chemical etching followed by embedding organic metal vapor phase epitaxy (OMVPE) growth.

We report progress on several practical issues of near field holographic (NFH) printing for optoelectronic applications. In particular, we report on the following: adaptation of the mask making process to large area holographically generated grating masks; evaluation of a commercially available UV contact aligner modified to allow routine NFH printing; use of mask copies to avoid excessive wear on original masks; options for reducing the writing time for e-beam generated grating masks; and the application of e-beam generated grating masks to a DFB six-laser array with 200-GHz frequency channel separation.