Volume 99, Issue 2, 15 January 2006
Index of content:
- LASERS, OPTICS, AND OPTOELECTRONICS
99(2006); http://dx.doi.org/10.1063/1.2159551View Description Hide Description
Polarized visible, near-infrared, and up-conversion emission characteristics in near-stoichiometric -cut -codoped crystals, prepared by vapor-transport-equilibration (VTE) technique, were investigated and discussed in comparison with corresponding as-grown crystal, thermally calcined powder, as well as -cut only -doped crystal that was subjected to the same VTE procedure as one of the -codoped crystals. The VTE-induced crystalline phase transformation is discussed in combination with optical absorption results reported previously. The percentage of ions present in the crystals as the phase is evaluated based upon the optical absorption and the emission data at . An empirical expression for evaluating the Li composition in a near-stoichiometric Er(/Yb)-doped crystal from the narrowing percentage of the - or -polarized emission peak is established based upon the emission spectra of singly Er-doped VTE crystals. From the measured absorption band areas and the Judd-Ofelt theory, the influence of the VTE treatment on the spectroscopic property was studied. The experimentally observed VTE effect on the emission intensity is conducted with the theoretical results of the transition probability. Both the theoretical and experimental results reveal that the VTE treatment results in the lengthening of the lifetime as much as 15%. A mechanism that the VTE treatment induces the crystalline phase transformation and the reduction of both and intrinsic defect contents is proposed to explain the VTE effect on the lifetime.
99(2006); http://dx.doi.org/10.1063/1.2163011View Description Hide Description
We demonstrate real-time tunability of a chip-based liquid light source enabled by microfluidicmixing. The mixer and light source are fabricated in SU-8 which is suitable for integration in SU-8-based laboratory-on-a-chip microsystems. The tunability of the light source is achieved by changing the concentration of rhodamine 6G dye inside two integrated vertical resonators, since both the refractive index and the gain profile are influenced by the dye concentration. The effect on the refractive index and the gain profile of rhodamine 6G in ethanol is investigated and the continuous tuning of the laser output wavelength is demonstrated using an ethanolic rhodamine 6G solution of mixed with pure ethanol. This yields rhodamine 6G concentrations from to inside the laser resonators and a wavelength change of 10 nm with a response time of 110 s.
99(2006); http://dx.doi.org/10.1063/1.2163007View Description Hide Description
We report the study of two-dimensional photonic crystals fabricated on silicon-on-insulator substrates. self-assembled islands are embedded as an active internal optical source inside the photonic crystals. We present a detailed analysis of photonic crystalmicrocavities and waveguides using the room-temperature island photoluminescence. The tunability of the microcavity resonant emission is demonstrated between 1.2 and . We show that the microcavityphotoluminescence is weakly dependent on the temperature. The polarized transmission properties of W1 single-line defect waveguides are investigated using the photoluminescence as an internal source. The transmission spectra are correlated to those given by two-dimensional finite-difference time-domain calculations.
Transient radiation responses of silica-based optical fibers: Influence of modified chemical-vapor deposition process parameters99(2006); http://dx.doi.org/10.1063/1.2161826View Description Hide Description
We characterized the behaviors of eight prototype single-mode optical fibers, made by the modified chemical-vapor deposition process, under pulsed x-ray irradiation. For this purpose, we measured the time-dependent changes in the radiation-induced attenuation at 1.55 and after exposure to an x-ray pulse. By using a dedicated set of prototype germanosilicate fibers with carefully designed process parameters, we show the predominant impact on their vulnerability of the two codopants (germanium and phosphorus) incorporated in their claddings. Compared to these influences on the radiation-induced loss levels and recovery kinetics, the impacts of the preform deposition temperature and of the fiber drawing tension on the fiber radiation sensitivity are less important. However, our results show that lowering the standard preform deposition temperature from 2000 to 1600 °C and the drawing tension from 140 to 20 g slightly decreases the induced losses at both wavelengths. We propose some hypotheses on the radiation-induced defects and physical mechanisms at the origin of these influences.
Sum and difference frequency generation as diagnostics for leaky eigenmodes in two-dimensional photonic crystal waveguides99(2006); http://dx.doi.org/10.1063/1.2161415View Description Hide Description
We experimentally demonstrate how sum frequency generation (SFG) and difference frequency generation (DFG) of pulses can be enhanced and serve as diagnostics for leaky eigenmodes in a two-dimensional GaAsphotonic crystal waveguide. SFG at is obtained in reflection from -polarized and -polarized pulses, with both input beams coupled to leaky eigenmodes; the SFG is enhanced by compared to that from an untextured GaAs surface. We are able to detect Drude induced subnanometer blueshifts of the SFG, corresponding to refractive index changes of . DFG of light obtained in reflection from -polarized and -polarized pulses displays an enhancement of via three different leaky eigenmodes. As the beampolarization is varied from polarized to right and left circularly polarized, the DFG remains essentially linearly polarized but with a reduced, albeit different, intensity for right and left circularly polarized pulses. Futhermore, the plane of polarization also rotates by different amounts for the left and right circularly polarized light, demonstrating interference of the components generated by - and -polarized pulses. Overall, our results demonstrate how enhanced DFG and SFG from leaky eigenmodes can be used to characterize their properties more precisely than linear optical techniques.