Submillimeter spectroscopy of tilted Nd1.85Ce0.15CuO4−δ films: Observation of a mixed ac-plane excitation

The anisotropic conductivity of a series of tilted Nd1.85Ce0.15CuO4−δ thin films was measured by quasioptical spectroscopy in the frequency range 6 cm−1<ν<40 cm−1. Two characteristic features have been observed in the low-temperature transmission spectra. The first one at ν=12 cm−1 was shown to reflect the c-axis plasma frequency of Nd1.85Ce0.15CuO4−δ. The second feature represents a mixed ab-plane/c-axis excitation. The frequency of this resonance may be changed in a controllable way by rotating the polarization of the incident radiation.