The dispersion of excitons, polaritons and biexcitons in direct-gap semiconductors

The transition from a low density gas of excitons to an electron-hole plasma is connected with strong variations of the optical properties. In this contribution we investigate both the optical nonlinearities produced in CdS by an intense laser beam in the spectral region close to the absorption edge and at the position of the laser itself. In a second part it is shown that the nonlinearities at the photon energy of the incident laser may lead to absorptive and dispersive optical bistability.

Plasma induced optical nonlinearities and optical bistability in CdS

Size effects on polaritons in thin crystals with perfect interference spectra

The effect of crystal thickness on the exciton-polariton dispersion of anthracene is studied by using melt-grown crystals with thicknesses ranging from 3 to 0.1 μm. The refractive indices in the vicinity of the first-exciton resonance are determined for the polarization E ‖ b and E ‖ a by analyzing interference fringes observed in the reflection spectra at 10 K. In contrast to the results reported previously, it is found that the dispersion property is independent of the crystal thickness at least down to 0.1 μm. A comparison of the present result with the thickness-dependent dispersion formula is presented.



Der Einflus der Kristalldicke auf die Polaritondispersion von Anthracen wird an Kristallen aus der Schmelze mit einer Dicke von 3 bis 0,1 μm untersucht. Die Brechungsindizes in der Nahe der ersten Exzitonenresonanz werden durch die Analyse der Interferenzstreifen fur die Polarisation E ‖ b und E ‖ a aus dem Reflexions-Spektrum bei 10 K bestimmt. Im Gegensatz zu fruher gegebenen Ergebnissen wird gefunden, das die Dispersionseigenschaften unabhangig von der Kristalldicke bis herunter zu 0,1 μm sind. Ein Vergleich der vorhandenen Ergebnisse mit der von dickeabhangigen Dispersionsformeln wird vorgestellt.

Exciton–Polariton Dispersion of Thin Anthracene Crystals in the Thickness Range of 3 to 0.1 μm

Interference effect and dispersion in thin RbI crystals

Dispersion property of thin CdS crystals as function of thickness

Size Effect in the Refractive Index Dispersion of Thin CdS Crystals

The data are summarized, obtained by interference measurements at 4.2 K, on the dispersion of the refractive index n(λ) of submicron-thin CdS single crystals. The series of the dispersion curves, n(λ), measured for crystals of different thickness, is approximated by theoretical dependences allowing for spatial dispersion. These data present clear evidence that the refractive index depends on the thickness of crystals provided their dimensions are comparable with the wavelength of light or smaller than the latter.



[Russian Text Ignored].

Dispersion properties of submicron-thin CdS crystals

Dispersion curves of the refractive index and absorption spectra measured on thin wedge-shaped and plane-parallel CdS crystals are compared with corresponding dependences calculated on the framework of Pekar's theory. Frequency and temperature dependences of exciton polariton relaxation parameter are determined from the best fit.



[Russian Text Ignored].

V. V. Cherny

Papers

Dispersion property of thin CdS crystals as function of thickness

Size Effect in the Refractive Index Dispersion of Thin CdS Crystals

Dispersion properties of submicron-thin CdS crystals

Frequency and Temperature Dependences of Exciton Damping in CdS Crystals