Scattering efficiency, spectral

TABLE 2. Refractive Index Modulations Required to Achieve 100% Scattering Efficiencies in Phase Holograms of Various Thicknesses, and the Corresponding Approximate Angular and Spectral Bandwidths of the Holograms. The Angular Bandwidths are Measured in the Air Outside the Hologram. 

Each reciprocal lattice point is stimulated by some wavelength within the experimental bandwidth. A variety of wavelength-dependent factors affect the measured structure amplitude. These factors include the SR spectral profile, the effect of optical elements, sample scattering efficiencies, absorption of components in the beam and detector response. 

FIGURE 9.13 (a) Variation of the spectral scattering efficiency with respect to wavelength for a glass spherical particle of diameter 0.2 mm. When appropriate, the Rayleigh, Mie, and geometrical treatments are shown. Also shown is the Penndorf extension (b) same as (a), except for the variation of the spectral absorption efficiency. 

In addition to the photoluminescence red shifts, broadening of photoluminescence spectra and decrease in the photoluminescence quantum efficiency are reported with increasing temperature. The spectral broadening is due to scattering by coupling of excitons with acoustic and LO phonons [22]. The decrease in the photoluminescence quantum efficiency is due to non-radiative relaxation from the thermally activated state. The Stark effect also produces photoluminescence spectral shifts in CdSe quantum dots [23]. Large red shifts up to 75 meV are reported in the photoluminescence spectra of CdSe quantum dots under an applied electric field of 350 kVcm . Here, the applied electric field decreases or cancels a component in the excited state dipole that is parallel to the applied field the excited state dipole is contributed by the charge carriers present on the surface of the quantum dots. 

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