CdTe-based Light-Controllable Frequency-Selective Photonic Crystal Switch for Millimeter Waves
Final rept. 25 Aug 2010-25 Aug 2011
NATIONAL UNIV OF IRELAND MAYNOOTH (IRELAND)
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Frequency-selective mm-wave photonic-crystal PC beam switches of increased sensitivity for rapid turning off and on quasi-optical beams in response to light pulses as control signals have been designed, manufactured and experimentally tested. Light-controllable PC-enhanced devices using semiconductor wafers semi-insulating GaAs and Si layers or CdTe-coated quartz plates with special surface patterning will provide additional functionality for mm-wave beam processing, with sensitivity improved, according to simulations, by 2 to 4 orders of magnitude as compared to a single-wafer device. Experimental testing of light sensitivity of different kinds of PC structures when using a flash lamp as a light source proved a possibility of making mmwave PC devices capable of switching quasi-optical beams with available inexpensive light sources. Quartz-air PCs with a Si wafer insertion have shown extreme sensitivity due to slow electron-hole recombination tR50 s and thick photoconductive layer in silicon L0.3mm that allows one to completely turn off the transmission peak at f 92.5 GHz by the light pulse of intensity I 0.4 Wcm2 the PC transmission peak is reduced by 30 dB in response to the light whereas a single Si wafer transmission drops only by 4 dB. Similar kinds of PCs using CdTe-coated quartz wafer insertions, likewise GaAs wafers, are less sensitive to the light due to small recombination length L 3 micro meters in CdTe and GaAs. Yet, a flash lamp illumination proved to be sufficient for observing a reduction of transmission peak of PC.
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