LASERS _ AMPLIFIERS_1_

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					THIN FILM PHOTONIC CRYSTALS
Notes from meeting on 5th December 2003
Attendees: Wei Ding, Cristiano Cordeiro, Alexey Yulin, Steve Andrews, Philip Russell


1.    Choice of substrate
Three different types discussed: Si on silica on Si, silica and silica glass webs in PCF.
Decided to work with Si on silica first, and design devices for 1550 nm operation. (Pitch
needed for waveguide studies will be smaller than pitch required for vertical cavity studies.)
2.    Photoresist processing
Ideas for spin-coating glass web: fill short length of fibre with thinned photoresist and spin to
remove PR. Should leave a thin coating of PR on the interior surfaces. This could then be
exposed.
3.    Etching
Reactive ion etching of Si well understood (SRA). Etch rate is very high compared to
photoresist. We also discussed the option of using a focused ion beam (FIB) to form defect
structures after the holographic exposure, development & etching are complete. Also
discussed the need to consider how to make adiabatic mode transitions between smooth &
periodic waveguide regions; could be done by using an amplitude mask with blurred edges.
4.    Interferometer
Making good progress under direction of Mark Johnson. Plate and pillars will be ready next
week. Other smaller items (e.g., piezo mounts) will be ready in January. MJ to visit in January
– in the meantime piezos are being sent up to him for evaluation.
5.    Experimental
Focusing into thin waveguides (~ 1 micron thick) will not be easy. Possibly use a cylindrical
lens. Use of LC light modulator to shape the laser beam discussed – would be nice way of
optimising coupling. Wei to look into the coupling problem & possibly design a
reconfigurable input coupler.
Will need an infrared viewer & camera.
6.    Theory
Alex modelling the guided modes and designing the appropriate pitch. Will also calculate the
band structure for thin film corrugated waveguide structures (weak modulation of index –
maybe 30 nm deep in layer 500 nm thick of Si). Linear and nonlinear effects will be described
in the framework of coupled mode approach. Also of interest is the design of vertical cavity
surface-emitting Si membranes, made by etching out the substrate oxide.




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