Measuring the refractive index around intersubband transition resonance in GaN/AlN multi quantum wells

We present the direct measurement of the refractive index distribution (spectral dispersion) arising from an intersubband transition in GaN/AlN multi quantum wells structure. The measurement is carried out through a novel interferometric technique. The measured interferogram yields a change in the refractive index varying from -5 × 10^-3 to 6 × 10 ^-3 as a function of the wavelength, introduced by the intersubband resonance at 1.5 μm. These results compare well with those derived using Kramers-Kronig transform of the measured absorption spectrum.