We report on wet etching of photomodified regions in crystalline sapphire using KOH solution. Tightly focused femtosecond laser pulses (150 fs at 800 nm wavelength) were used to create void structures enclosed in an amorphised sapphire shell inside the bulk of a crystalline host. The diameter of the amorphous regions can be controlled by pulse energy and was typically 0.5–1.5 µm. The etching rate depends on the distance between adjacent irradiation spots, pulse energy, concentration of etchant and ultrasonic agitation.magnified imageAmorphised sapphire is etched out in KOH solution.(© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract:The optical linear and nonlinear properties of ∼ 340-nmthick Si membranes were investigated. The investigation included both experiments in which the reflection and transmission from the membranes were measured, and finite differences time domain simulations. The linear optical transmission of the Si membranes can be controlled by changing the thickness of a thermally grown oxide on the membrane. Illumination of the membranes with high levels of irradiation leads to optical modifications that are consistent with the formation of amorphous silicon and dielectric breakdown. When irradiated under conditions where dielectric breakdown occurs, the membranes can be ablated in a well-controlled manner. Laser micro-structuring of the membranes by ablation was carried out to make micrometer-sized holes by focused fs-pulses. Ns-pulses were also used to fabricate arrays of holes by proximity-ablation of a closely-packed pattern of colloidal particles.