Showing papers by "Applied Science Private University published in 1968"

Optical Properties and Reflectance of Uniaxial Absorbing Crystals

Abstract: The optical properties of strongly absorbing uniaxial crystals are examined. Equations for the reflectances for the basal plane are derived. The angle of refraction is discussed and the absorption coefficient for the ordinary wave is derived. The reflectance equation is solved in a form suitable for computer calculation of optical properties from experimental reflectance data.

An experimental study of saturable absorbers for ruby lasers

Abstract: This paper presents the results of a study of the behavior of some saturable dye filters used with ruby lasers. We review some apparently contradictory results obtained earlier and present modified forms of energy level models, which are consistent with the known photophysical properties of the molecules. We then present experimental evidence to elucidate the nature of the overall relaxation time, the source of the residual absorption, and the nature of the transient spectral hole burning, which gives rise to frequency-locking between different lasers. On the basis of the frequency-locking experiments, and our model, it is possible to calculate the rate at which the broad molecular absorption band couples into the narrow spectral width of the radiation field during pumping. This time is of the order of 5 \times 10^{-12} second for chloro-aluminum phthalocyanine in pyridine. Taking into account considerations such as excited-state absorption, mode of bleaching, etc., we conclude that the phthalocyanine dyes are best suited as saturable absorbers at low power levels (<5 MW/cm2but are unsuited for mode-locking applications. Cryptocyanine has lower residual losses above 10 MW/cm2and can be used for mode locking. Both types of dye exhibit very narrow spectral hole burning, which can be used to frequency-lock separate lasers.

Optical Properties of Zn

Abstract: The basal-plane reflectance of single crystals of high-purity (99.999%) Zn, cleaved and maintained in a vacuum chamber at pressures less than ${10}^{\ensuremath{-}9}$ Torr, has been measured in the wavelength region $1150\ensuremath{\le}\ensuremath{\lambda}\ensuremath{\le}5600$ \AA{}. All measurements were made at 96\ifmmode^\circ\else\textdegree\fi{}K. The shape of the reflectance curve for the ultraviolet region is quite accurately calculated on the basis of a free-electron model using the relaxation time, ${\ensuremath{\tau}}_{c}=3.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$ sec, calculated from the dc electrical conductivity at 96\ifmmode^\circ\else\textdegree\fi{}K, and an optical mass ${m}_{a}=2.04$. The magnitude of the reflectance, about 85% just below the plasma frequency, is less than that calculated for the free-electron model. The difference is presumably the effect of interband transitions. The plasma resonance occurs at 10.1 eV. The experiments clearly demonstrate the necessity of an atomically clean surface for meaningful reflectance measurements in the vacuum ultraviolet.