Femtosecond transients and nonlinear optical effects in cdsexs1-x glasses

Glasses doped with CdSexS1-x microcrystallites have attracted much attention recently. Semiconductor doped glasses are interesting both because of device applications as well as fundamental physics. Room-temperature capability, relatively large optical nonlinearity (n2 ≍ 10-8 - 10-9 cm2/kW), wavelength tunability (which is obtained by changing the composition x which changes the semiconductor bandedge and thus provides wavelength tunability), rapid response time (≍10 ps), ease and inexpensiveness of the fabrication make these materials suitable for guided-wave device application. The physics of quantum confinement effects in all three dimensions makes these materials particulary attractive from the fundamental understanding point of view. In order to observe quantum confinement effects, the crystallite sizes have to be small, with (f uniform size distribution. Commercially available glases have an average diameter of ≍120 Å with a FWHM size distribution of ≍50 Å. Therefore, quantum confinement effects are usually absent in commercial glasses. However, a more uniform size distribution and small crystal diameters can be obtained with careful heat treatment of the glass. Researchers at Corning have been able to fabricate glasses with average crystallite diameter ranging from 30 Å to 80 Å with 24 Å to 44 Å FWHM size distribution, respectively. Optical absorption, photoluminescence, x-ray diffraction and transmission electron microscopy have been conducted in order to examine microcrystallites as a function of composition and development.