Dispersion of the extraordinary and ordinary refractive indices of Al- and N-polar AlN waveguides is measured by multiple angle-of-incidence and spectroscopic ellipsometry techniques. The polarity-controlled AlN layers are grown by metal–organic chemical vapor deposition on (0001)- sapphire substrates. Taking into consideration the different surface morphologies of the Al- and N-polar AlN waveguides, we propose two optical models to describe the measured ellipsometry data. The results indicate that there is no difference between the refractive indices of the AlN grown in opposite directions, which confirms the potential of the AlN lateral polar structures for use in nonlinear optical applications based on quasi phase matching.
COBISS.SI-ID: 2798436
We report on measurements of the refractive indices and the absorption in bulk single crystals of aluminum nitride, in the region from 1 to 8 THz. The birefringence is approximately 0.2 and is larger than in the optical frequency range. Both indices exhibit normal dispersion with no pronounced absorption resonances. Optical power loss coefficients are approximately 2 cm-1 and 4 cm-1 and the estimated static dielectric constants are 7.84 and 9.22, for the ordinary and extraordinary polarization, respectively. Availability of good quality bulk single crystals allowed us to determine experimentally the dielectric properties in the THz frequency range for both eigen-polarizations for the first time.
COBISS.SI-ID: 28838439