Veronika Glaw

Optically bistable thin film devices using wide-gap II–VI compounds

Abstract Optically bistable interference filters and single bistable absorption layers were prepared by thermal evaporation of II–VI semiconductors on glass and sapphire substrates. The bistable interference filters consist of a low absorption spacer, e.g. ZnS or CdS, with multilayer mirrors on both sides and an absorption layer, e.g. CdSe, on the beam exit side. Absorption leads to heating and thermooptic tuning of the spacer resulting in optical bistability and other types of nonlinear optic effects. Stable bistable switching is achieved for millions of cycles. Optical bistability due to increasing absorption is observed also in single ZnSe layers with an incident photon energy just below the band gap. The influence of different thin film preparation methods is studied. The switching elements were operated between 400 and 800 nm wavelength and needed switching powers of several mW. Switching times in the microsecond range were measured. The performance of the devices is optimized using theoretical models.

Bistable Switching Elements Prepared By Thermal Evaporation

Optically bistable interference filters and single bistable absorption layers were prepared by thermal and electron beam evaporation of CdSe, CdS, ZnSe, ZnS, MgF2, Ta205 and Si02 on glass substrates. The bistable interference filters consist of a low absorption spacer, e.g. CdS, with multilaver mirrors on both sides and an absorption layer, e.g. CdSe, on the beam exit side. Absorption leads to heating and thermooptic tuning of the spacer resulting in optical bistability. Using low absorption spacers and an external absorber the temperature rise necessary for switching can be reduced. Therefore bistable elements allowing more than 10 mill. switching cycles have been achieved. Optical bistability is observed also in single ZnSe layers due to increasing absorption with an incident photon energy just below the band gap. The switching elements were operated between 500 and 600 nm wavelength and needed switching powers of several mW. Switching times in the microsecond range were measured.

Optimization Parameters for Laser-induced Forward Transfer of Al and Cu on Si-wafer Substrate

The research goal is to perform a laser-writing study to deposition of micro/nano particles on the substrate as interconnection usage. The threshold of laser energy, pulses per laser shot, as well as pulse overlapping is crucial to achieve the best deposition results possible. The present study aims to the novel technique by laser deposition of Aluminium and Copper nano particles on silicon wafer substrate. Thin μm films have been deposited from one-side coated glass to Silicon wafers by sputtering nano particles using laser radiation. Distance between donor film and substrate (ε) was up to several 100 μm and it has been optimized as 300 μm. A step-by-step optimization guide for deposition parameters were first developed and presented. The identification of laser energy threshold, pulses per laser shot, in addition to pulse overlapping is essential if the best deposition results are going to be drawn by laser direct writing method. This technique is regarded as the most important direct-write alternative for lithographic processes in order to generate patterns with

Nano particle production by laser ablation and metal sputtering on Si-Wafer substrate

This research relates to methods of deposition and patterning a surface with nano sputtered particles by Laser. The method is mask-less and without vacuum requirement which can be used in wire bonding and microelectronics devices.

Laser Melting of Metal Powders Using Nd:yag and Compact Diode Laser for Micro Particle Deposition

Laser melting of different metal powders is investigated using a Nd:YAG laser system and a compact diode laser. The influence of various process parameters on the physical properties of the molten particles is studied.