UV-LED controlled GaN-based SAW phase shifter

The UV-LED controlled phase shifter of an RF signal based on a GaN-sapphire surface-acoustic-wave (SAW) filter has been implemented. At the optical wavelength 298 nm and SAW frequency 307 MHz, the UV-induced relative change in SAW velocity per unit optical power density is 2×10−6 (µW/mm2)−1 corresponding to 3.7° phase shift. The phase modulation of an RF signal by rectangular UV pulses has been demonstrated. The efficiency of the phase shifter can be considerably improved by proper selection of sheet-resistivity of the GaN layer.