10 June 2004 Variable optical attenuator realized on silicon V-groove for optical beamforming networks
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We report in this paper the principal function of the electrically controlled variable optical attenuator (VOA) using polymer dispersed liquid crystal (PDLC) and describe the fabrication procedure on silicon v-groove. We have fabricated three VOA with a pitch of 2 mm on a single silicion v-groove chip with total dimensions of 12 mm x 10 mm. We have achieved a cell-dependent contrast ratio from 8 dB to 14 dB by applying a control voltage URMS (squared wave voltage, f = 10 kHz) from 0 to 30 V. We measured also a cell-dependent polarization dependent loss (PDL): < 3.6 dB for two cells and < 1.6 dB for one cell depending on the control voltage. The strong variation of the PDL and contrast ratio is due to the non-optimized PDLC processing parameters. Due to the large pitch size there is no crosstalk. The estimated power consumption is very low (< 1 μW), so the described fabrication procedure meets the requirements low cost, small power consumption and compact size. We have used this three VOA and proper chosen delay lines to build up a liquid crystal phase shifter (LCPS) for optically generated RF-signals at fRF = 2 GHz. Using the vector sum of two signals a continuously 360° phase shift of the RF-signal is demonstrated. We will present the theory and measurement results of 360° phase shifting. This LCPS can be used to control individually the phase and amplitude of each antenna element.
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Hayattin Yilmaz, Hayattin Yilmaz, Andreas Breuel, Andreas Breuel, Wolfgang Vogel, Wolfgang Vogel, Manfred Berroth, Manfred Berroth, } "Variable optical attenuator realized on silicon V-groove for optical beamforming networks", Proc. SPIE 5358, Photonics Packaging and Integration IV, (10 June 2004); doi: 10.1117/12.526488; https://doi.org/10.1117/12.526488

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