Ridge-waveguide sidewall-grating distributed feedback structures fabricated by x-ray lithography

Abstract

A novel distributed feedback structure has been developed in which the grating is patterned onto the sidewalls of a ridge waveguide. Such a laser structure results in simplified processing in that the grating fabrication is independent of both the materials growth and the guide formation. The ridge waveguide is first formed by wet-chemical etching. Then, a poly(methylmethacrylate) grating (Λ=230 nm) is patterned onto this ridge waveguide using x-ray lithography. A Ti/Al etch mask is lifted-off to serve as a mask for subsequent reactive-ion etching. Gratings with long-range spatial-phase coherence and negligible distortion, characteristics which are necessary for accurate control of the wavelength and bandwidth, are obtained using a holographically generated x-ray mask.

Sidewall gratings in ultra-low-loss Si_3N_4 planar waveguides

“…There have been prior results reported on sidewall grating technologies that include patterning through reactive-ion etching [6] and direct-write spatial-phase-locked electronbeam lithography [7]. Previous results in low loss, highly selective gratings include surface relief gratings integrated with aluminum oxide ridge waveguides [8] and sidewall gratings fabricated within a curved waveguide structure on a low loss silica platform [9].…”

“…Prominent results in these approaches have bandwidths on the order of 0.12 nm with coupling constant values of roughly 4.5 cm −1 [10]. The limitations to these approaches include their reliance on strict etch tolerances [8], as well as their requirements for multiple lithographic patterning and etch steps [6,10]. The limitations of prior approaches are primarily due to a combination of both design constraints and fabrication technology.…”

Two-dimensional simulation of high-order laterally-coupled GaAs-AlGaAs DFB laser diodes

“…LC-DFB ridge laser diodes have been realized in InGaAs/GaAs/AlGaAs [1][2][3][4], GaInNAs/AlGaAs [5], InGaAsSb-AlGaAsSb [6], InGaAsP/InP [7][8][9][10] and InGaN/ GaN [11] material systems. In most of the fabricated laser diodes, first-order gratings were defined by e-beam [1-6, 9, 10], focused ion beam [7] or x-ray [8] lithography. Secondorder gratings defined by high-resolution e-beam lithography were utilized in the InGaN/GaN LC-DFB LDs demonstrated by Schweizer et al [11].…”

Functional Imaging with Chemically Amplified Resists and Organic Molecules

“…The patternability of microresists also continues to attract attention for several applications other than microelectronics manufacturing. In microoptics, polymer resists have been used to create interconnected channel waveguides and grade coupler elements . The production of optical storage media and liquid-crystal displays (LCD) also involves resist technology.…”