Measurement of the refractive index dispersion around an absorbing line

Marco Montecchi, E. Nichelatti, Rosamaria M. Montereali +2 more

Marco Montecchi, E. Nichelatti, Rosamaria M. Montereali +2 more

. Besides the extinction coe_cient, the refractive index of a dielectricmedium is modi_ed by the presence of resonant absorbing centres, too. Fully an-alytical expressions of the complex refractive index dispersions are derived for thecases of homogeneous and inhomogeneous absorption-line broadening. In both cases,we demonstrate that the modi_cation is such that the refractive index results asincreased at photon energies lower than the resonance absorption energy. If theabsorbing centres also emit Stokes-shifted radiation, the increase of refractive indexcan be exploited for passive and active waveguiding applications. An example isreported regarding active waveguides based on colour centres in a lithium uoridecrystal.Keywords: Absorbing centres, active waveguiding, colour centres, Gaussian line-shape, inhomogeneous line broadening, refractive index.

Mingneng Feng, Yikun Liu, Yongyao Li +2 more

Light propagation behavior in a resonantly absorbing waveguide array is analyzed. Both a Lorentzian line shape and an inhomogeneous broadened absorbing line shape are considered, with their imaginary and real part of the refractive index determined by a Kramers-Kronig relationship. The diffracted wave is shown to have the frequency spectra determined by the material absorption, dispersion as well as the waveguide structure. An interesting phenomenon is that a spectral hole is produced and becomes deeper in the diffraction spectrum as the thickness of the resonantly absorbing waveguide array increases. The experimental measurements conducted in a waveguide array are found to be in good agreement with the numerical results.

G. T. Purves, Gregor Jundt, Charles S. Adams +1 more

Tao Shui, Zhao Zhang, Chenchen Yin +2 more

Jerald R. Izatt, Brent L. Bean, Harold A. Daw

The real and imaginary parts of the complex index of refraction in the R-line region of ruby have been measured near liquid-nitrogen temperature with sufficient resolution that the R-line doublet structure was well resolved. A modification of the usual Babinet compensator technique was used for the refractive-index measurements, which were found to correlate with the absorption measurements as predicted by the Kramers-Kronig relations. An attempt at direct quantitative verification of the dispersion relations for an optically pumped sample is also described.