Departmental Colloquium

Laser Nano-Fabrication For 3-D Optical And Biophotonic Systems (by Prof. P. Herman)

Prof. Peter Herman
University of Toronto

Time
Wed. November 15, 2006     3:30 PM     Strirling A

Abstract

Reliable short pulse laser systems are now emerging, opening new directions in manufacturing that can finally harness the unique ultrafast properties of strong nonlinear interaction, small heat affected zone, and three-dimensional (3-D) structuring at - or even below - optical diffraction limits. Alternatively, diffractive optical elements promise an extension of laser holography to enable high-speed and large-volume manufacturing of 3-D nanostructures with conventional cw laser systems. The presentation begins with a review contrasting the attributes of high (~MHz) and low (1 kHz) repetition rate ultrafast laser systems in driving/avoiding heat accumulation effects in transparent materials for 3-D direct write applications. Time-gated camera images of laser-excited emissions confirm heat-accumulation effects and extended modification zones for rates above ~300 kHz in various glasses. Here, reduced resolution trades in favour of thermal annealing effects that inhibit microcracking. We further report on multiple processing windows across kHz and MHz rates and at various femtosecond and picosecond domains for writing good quality 3-D devices such as low loss (0.2 dB/cm) optical waveguides, couplers, Bragg grating waveguides, photonic crystal templates, and opto-fluidic systems. Lastly, we present recent progress on developing diffractive optical elements for highly stable laser holographic writing of 3-D photonic crystal templates and close by comparing attributes this large-volume parallel processing method with the slower but more facile serial approach in direct-write ultrafast-laser processing.

Refreshments will be available 15 mins before the talk

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