Laser interference lithography with highly accurate interferometric alignment

Three dimensional photonic crystals, e.g. for obtaining the so-called woodpile structure, can, among others, be fabricated by vertical stacking of multiple gratings. One of the requirements for obtaining a full photonic bandgap in such a photonic crystal is an accurate angular and lateral alignment of the successive gratings. Using laser interference lithography at 266 nm wavelength, we fabricated gratings in silicon with periods down to 300 nm. We present a method for aligning further grating exposures with respect to this grating with a 0.001 degree angular and a few nanometers lateral resolution

Laser interference lithography with highly accurate interferometric alignment

It is shown experimentally that in laser interference lithography, by using a reference grating, respective grating layers can be positioned with high relative accuracy. A 0.001 degree angular and a few nanometers lateral resolution have been demonstrated

Optimized Deep UV hardbake process for metal-free dry-etching of integrated optical devices

Photostabilization is a widely used post lithographic resist treatment process, which allows hardening the resist profile in order to maintain critical dimensions and to increase selectivity in subsequent process steps such as reactive ion etching. In this paper we present the optimization of Deep UV-curing of 0,3-3.5 μm thick positive resist profiles followed by heat treatment up to 280 0C. The effectiveness of this resist treatment allows for metal mask free reactive ion etching with selectivity up to 6 for silicon structures, thermal silicon oxide and silicon oxynitride. A number of experimental results on integrated optics structures are presented that demonstrate the improved etch profiles obtained with this approach

Integrated mechano-optical hydrogen gas sensor using cantilever bending readout with a Si3N4 grated waveguide

We demonstrate a proof of concept of a novel and compact integrated mechano-optical sensor for H2 detection based on a microcantilever suspended above a Si3N4 grated waveguide. The fabricated devices are mechanically and optically modeled and characterized. Sensing operation of the sensor is demonstrated with 1% H2 in N2. The error in detection of the cantilever bending induced by absorption of H2 is estimated to be approximately 10 nm. Significantly improved sensitivity (down to ∼33 pm) is expected for reduced initial bending of the microcantilever. The simulation and experimental results are in good agreement and provide a good guideline for further optimization of the sensor

Large area photonic crystal slabs for visible light with waveguiding defect structures: Fabrication with focused ion beam assisted laser interference lithography

Extended photonic crystal slabs with light-guiding defects have been created by a combination of laser interference lithography (LIL) and local focused ion beam (FIB) assisted deposition. Large area, highly uniform photonic crystal slabs for visible light are thus made possible. The Figure shows a freestanding Si3N4-air photonic crystal with a light- guiding defect line running along the center of the slab (total length = 1 mm)