Liquid crystal variable optical attenuators integrated on planar lightwave circuits

Variable optical attenuators using polymer-network liquid crystal have been integrated with the pitch of 250 μm on planar lightwave circuits. Trenches are cut in the direction perpendicular to the parallel light waveguides into planar lightwave circuits, a transparent electrode is deposited inside the trenches, and the trenches are filled with polymer-network liquid crystal. The typical attenuation range is 18 dB when the driving voltage is <20 Vrms at 1.55-μm wavelength. The power consumption is estimated to be very low (200 nW/ch).