The enhancement mechanism of the third-order nonlinear optical response of cavity polaritons is theoretically investigated through the size dependence of the exciton system. Cavity quantum electrodynamics ͑cavity QED͒ effect strongly affects the balance between absorption saturation and induced absorption, depending on the system size, through the modification of the level structure of exciton-and biexciton-cavity coupled states. This triggers a drastic change in the optical nonlinearity, which is another essential effect of the cavity QED to enhance the optical nonlinearity.
Formation of diamond film by DC plasma chemical vapor deposition (CVD), wherein the waveform of the power supply is half-wave-rectified (HWR), has been investigated. When HWR voltage is applied to the electrodes, the waveforms of the discharge voltage (V
d) and current (I
d) are intermittent and show a large peak at the beginning of the discharge. The films deposited by intermittent discharge (ID) are superior in crystalline quality compared with that by conventional continuous discharge (CD). The average value of electron temperature (T
e) in ID, measured by a Langmuir probe (LP) in the plasma of hydrogen gas, is higher than that of CD. The LP current shows a very high peak at the beginning of the ID process, and the value of T
e and density of electrons (N
e) at this peak are very large. These rises in T
e by ID are effective in enhancing the dissociation of the source gas by electron collision. It has been concluded from the present study that ID is an effectual method to obtain high-quality diamond film.
Folding of longitudinal acoustic (LA) mode phonons in ZnSe–ZnTe strained layer superlattices, grown on the (001) GaAs without buffer layers by molecular beam epitaxy (MBE), was measured as a function of period and thickness of the layers by Raman scattenng. The dispersion relation between observed LA frequencies and wave number of the superlattices was analyzed by fitting the sound velocity as a parameter in the Rytov model. Two analytical solutions were obtained from the model. It is supported by consideration of calculation and experimental results that the sound velocity of the ZnSe and ZnTe layers in the superlattices is smaller and larger than their bulk values respectively, and this implies elongation of the ZnSe layers and compression of the ZnTe layers.
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