The optical properties of glasses containing a small amount of thermally developed CdSexS1−x microcrystalline phase are studied with emphasis on quantum confinement effects exhibited at small crystallite size. Optical absorption, photoluminescence, x-ray diffraction, and transmission electron microscopy are used to examine microcrystallites as a function of composition and development. Results are presented for a series of commercially available CorningR filter glasses with a selenium mole fraction in the range 0.28≤x≤0.74, as well as for several experimental glasses in which the average microcrystallite diameters range from 30 to 80 Å. Optical effects observed in the experimental glasses that are due to electron and hole confinement are not present in the filter glasses considered; variations in optical properties of the filters are due to changes in stoichiometry of the CdSexS1−x mixed anion system. A brief discussion of other microcrystalline phases in glass is also presented. These microcrystallites show room-temperature optical absorption structure analogous to bulk crystal excitons; the temperature dependence of this structure is contrasted with that resulting from quantum confinement in CdSexS1−x glasses.
We investigate the use of infrared femtosecond laser pulses to induce highly localized refractive-index changes in fused-silica glasses. We characterize the magnitude of the change as a function of exposure and measure index changes as large as 3x10(-3) and 5x10(-3) in pure fused silica and boron-doped silica, respectively. The potential of this technique for writing three-dimensional photonic structures in bulk glasses is demonstrated by the fabrication of a Y coupler within a sample of pure fused silica.
Quantum confined nanocrystals of PbS in glass were used as intracavity saturable absorbers to obtain passive continuous-wave mode locking in a Cr:forsterite laser. We obtained near transformed-limited 4.6 ps laser pulses at 110 MHz repetition rate, and a wide tunability range of 1207–1307 nm. The absorption saturation intensity of the quantum-dot PbS doped glasses was measured to be 0.2 MW/cm2.
The spectroscopic properties of Ni(2+)- doped nanocrystalline glass-ceramic fibers are reported. The cerammed fibers show strong fluorescence with peak wavelength at 1250 nm, 3-dB bandwidth at ~250nm, measured lifetimes at >1ms, and low-fluorescence saturation powers (~35mW) for 980-nm diode pumping. Current diode-pumped output powers are ~100microW .
Metal nanoparticles have been used for coloring glass since antiquity. Colors are produced by light scattering and absorption associated with plasmon resonances of the particles. Recently, dewetting at high temperature has been demonstrated as a straightforward high-yield/low-cost technique for nanopatterning thin metal films into planar arrays of spherical nanocaps. Here, we show that by simply tuning the contact angle of the metal dewetted nanocaps one can achieve narrow resonances and large tunability compared with traditional approaches such as changing particle size. A vast range of colors is obtained, covering the whole visible spectrum and readily controlled by the choice of film thickness and materials. The small size of the particles results in a mild dependence on incidence illumination angle, whereas their high anisotropy gives rise to strong dichroism. We also show color tuning through 65 simple, low-cost lithography-free surface nanostructuring, 66 which is ideal for industrially scalable applications.
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