Volume 99, Issue 3, 01 February 2006
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS
99(2006); http://dx.doi.org/10.1063/1.2165411View Description Hide Description
Irregularities in the edge of the bit marks is one of the most critical sources of the noise that lead to timing jitter in optical phase change recording. The maximum linear bit density achievable at a given wavelength and lens numerical aperture is often limited by jitter. Jitter is largely determined by the combined optical, thermal, and crystallization properties of the medium and by the optical quality and recording strategy of the laser beam. Media with a patterned phase-change layer are proposed for controlling the mark edge jitter by making distinct mark edges. The preliminary simulation results from writing on the transverse and longitudinal patterns look promising in producing rectangular bit marks with distinct boundaries. The bit marks written on patterned media also have a smaller size compared to those written on continuous media. An interesting and unexpected result is the disappearance of the crescent-shaped trailing edge in all the bit marks on the patterned media, the shape and existence of which can have a great effect on the trailing edge jitter. Writing on grooved media has also been simulated for further comparison. In the present investigation a simulation code is developed using commercial finite element analysis software for the heat transfer simulation, with a custom-integrated crystallizationmodel.
99(2006); http://dx.doi.org/10.1063/1.2168236View Description Hide Description
Three-dimensional photonic quantum ring lasers with a square microcavity were fabricated and their spectra were explained by combining two conditions: the off-normal Fabry-Pérot resonance and quadruple-bounced whispering-gallery mode. The angular distribution of the emission modes and their discrete wavelengths were in excellent agreement with a three-dimensional Rayleigh-Fabry-Pérot model. The three-dimensional model also showed that the slope of the spectral mode spacing and the value of the angular mode spacing as a function of the length of a square side are inversely proportional to and , respectively.
99(2006); http://dx.doi.org/10.1063/1.2169349View Description Hide Description
Design results aimed at achieving tunable high-temperature operation in the atmospheric transmission window are presented for the intersubband Raman lasers based on coupled quantum wells. The ultrafast longitudinal-optical-phonon (LO-phonon) scattering in quantum wells(QWs) can be used for the rapid depopulation of the lower laser state, while the large LO-phonon energies allow for a design to minimize the thermal population of the lower laser state, and are therefore beneficial for obtaining high-temperature operation. The Raman gain is proportional to the difference between the virtual lifetime of the upper laser state and the effective lifetime of the lower laser state instead of the real lifetimes. The advantage is that these lifetimes can be tuned with the detuning of the pump photon energy from the subband energy separation. At a fixed pumping wavelength of , the tuning range of is predicted with a moderate Raman gain of at least as the electric field is varied. Furthermore, the output power of this laser is unlikely to saturate because of the intrinsically short intersubband lifetimes in the GaN-based QWs.
Measuring the electron temperature by optical emission spectroscopy in two temperature plasmas at atmospheric pressure: A critical approach99(2006); http://dx.doi.org/10.1063/1.2170416View Description Hide Description
The measurement of the electron mean kinetic energy by identifying the electron temperature and the excitation temperature obtained by optical emission spectroscopy is theoretically studied for two temperature argon plasmas at atmospheric pressure. Using a 32-level collisional radiative model in which both electron impact and argon-impact inelastic collisions are taken into account, it has been found that under certain conditions the argon inelastic collisions may cause a decrease of the argon excitation temperature so that the relation is satisfied. This inequality also appears when electron losses due to diffusion are important and the electron density is lower than its equilibrium value.