Electrooptical Modulator at Telecommunication Wavelengths Based on GaN–AlN Coupled Quantum Wells

We report on the demonstration of an intersubband (ISB) coupled quantum-well modulator operating at room temperature and telecommunication wavelength using a GaN-AIN quantum-well structure. The optical modulation is shown to result from electron tunneling between the wells. Stark shifting of the ISB absorption is observed. The maximum modulation depth is 0.79% at lambda= 2.3 mum and 0.18% at lambda= 1.37 mum for a mesa device with only 151-nm interaction length. We show that by reducing the mesa size down to 15 times 15 mum
²
, optical modulation bandwidth as large as 3 GHz can be obtained.