Abstract-A biosensor application of vertically coupled glass microring resonators with Q ∼ 12 000 is introduced. Using balanced photodetection, very high signal to noise ratios, and thus high sensitivity to refractive index changes (limit of detection of 1.8 × 10

Optically pumped lasing of (111) oriented bulk ZnSe grown by seeded physical vapor phase transport (SPVT) technique has been achieved at room temperature under near resonant pumping with the excitation photon energy very close to the fundamental band gap. Laser emission can be seen at a pumping intensity as low as 7 kW/cm2. The lasing mode spacings resulting from the dispersion of the index of refraction for ZnSe in a Fabry–Perot resonator-like cavity have been observed as well. Our experimental results demonstrate that SPVT ZnSe single crystals have the quality sufficient to develop low-threshold, high-power output blue lasers.

Photoluminescence (PL) and thermally stimulated conductivity (TSC) data on high-resistivity, p-type CdTe single crystals are presented. The PL emission in these samples consists of two closely overlapping components peaking at approximately 1.47 and 1.49 eV. Thermal quenching of these signals reveals activation energies of ∼0.02 and ∼0.13 eV for the former component, and ∼0.11 eV for the latter. TSC signals at temperatures corresponding to those over which thermal quenching occurs are observed. The TSC peaks are due to hole release with activation energies which agree with those obtained from the thermal quenching studies. Etching of the samples removes surface damage caused by mechanical polishing. The surface damage produces nonradiative pathways by which electron-hole recombination can take place without luminescence. A model based on free-electron to trapped-hole recombination is presented to account for the data. It is shown, from numerical solutions of the rate equations describing the model, that by explicitly incorporating into the model more than one hole state at which radiative recombination can occur, shifts in the emission energy during time-resolved and intensity-dependence studies can be expected.

Laser-induced transient gratings produced by two-photon absorption of picosecond pulses at 1.064 Jim were used to examine the room-temperature nonlinear optical responses of CdTe crystals with different types of conductivity. Pulse-probe degenerate four-wave mixing measurements of grating dynamics on subnanosecond time scales were used to measure the ambipolar diffusion coefficient (Da) of charge carriers in the crystals. The value of Da = 3.0 cm 2 s -1 which was obtained is in very good agreement with theoretical estimates. A long-lived contribution to the signal consistent with a trapped charge photorefractive effect was observed at la:-ge .grati.ng spacings for n-type conductivity, and is tentatively attributed to a l.arger trap denSIty In thIS sample. Measurements of the relative scattering efficiencies of successive diffracted orders in the Raman-Nath regime allowed for calculation of the laser-induced change in the index of refraction, due to the creation of free carriers. The value of ~n = 4 X 10 -4 which was obtained is in good agreement with theoretical estimates. -Polished, 1 Xl XO.l em 3 , n-andp-typesamplesofCdTe were used in this study. The polished surfaces were [111 J faces. Room-temperature absorption spectra were obtained using a Perkin-Elmer Model 330 Spectrophotometer. In the PP and SS experiments, the samples were excited and probed with rp = 30 ps fun width at half maximum (FWHM) Gaussian pulses of the It = 1.064 J-i,m emission of aNd: Y AG 1359

We report pressure-dependent photoluminescence (PL) measurements on ZnSe single crystals grown by the seeded physical vapor phase transport technique. Two kinds of ZnSe samples, the as-grown and Zn-extracted single crystals were used in this study. The Id1 line is the predominant spectral feature for the as-grown samples and shifts with pressure at a rate of 7.3 meV/kbar. The I3 emission dominates the PL spectra of the Zn-extracted samples and has a pressure coefficient of 6.6 meV/kbar, which is inconsistent with the assumption of the I3 line originating from the recombination of the excitons bound to ionized donors.