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The beam pulse structure of the HIL cyclotron and thick target γ - γ co-incidence measurements in the in-beam and off-beam modes have been used to search for isomers in the A &asymph; 120 mass region using heavy-ion reactions. The half-life of the 2721 keV, (25/2+) level in 121Sb was determined in the off-beam mode to be 167 ± 19 µs. Two deexcitation sequences of this isomer are proposed. The isomeric state is considered to be of 3-quasiparticle nature π(d5/2)ν(h²11/2)10+. [ABSTRACT FROM AUTHOR]

We investigate experimentally the polarization dynamics of a vertical external-cavity surface-emitting laser with a saturable absorber mirror in the cavity. We demonstrate that the normalized Stokes parameters and degree of polarization are functions of time reaching extreme values around the pulse peaks. Our experiments show that light is elliptically polarized, being able to have a circular right-handed or left-handed component, depending on the orientation of the saturable absorber mirror.

In this paper, the results of the electrical, noise, and optical characterization of p-i-n and p-B-i-n diodes with AlSb and 4 ML AlSb/8 ML GaSb superlattice barriers in High-Operating Temperature conditions, are presented. Experimental and theoretical noise parameters were compared. Both dark current and noise analysis showed that the p-B p_bulk -i-n bariode had the best performance. P-i-n photodiodes had the highest experimental value of specific detectivity (D*) of 6.16 × 10 9 Jones at 210 K and zero bias. At about -1 V reverse bias, the bariode with AlSb/GaSb electron barrier caught up to it and both devices achieved D* = (1-1.1) × 10 8 Jones. Further optimization of the superlattice-based electron barrier should result in the improvement of bariode performance at a smaller bias, at which better noise performance is more pronounced. It was shown that neglecting the low-frequency noise component can lead to a significant overestimation of detectivity. The simple method of incorporation of low-frequency noise contribution in the detectivity calculation, without time-consuming measurements, has been proposed.

In this paper, the study of defects in InAs/GaSb type-II superlattices using high-resolution an x-ray diffraction method as well as scanning (SEM) and transmission (TEM) electron microscopy is presented. The investigated superlattices had 200 (#SL200), 300 (#SL300), and 400 (#SL400) periods and were grown using molecular beam epitaxy. The growth conditions differed only in growth temperature, which was 370 °C for #SL400 and #SL200, and 390 °C for #SL300. A wings-like diffuse scattering was observed in reciprocal space maps of symmetrical (004) GaSb reflection. The micrometer-sized defect conglomerates comprised of stacking faults, and linear dislocations were revealed by the analysis of diffuse scattering intensity in combination with SEM and TEM imaging. The following defect-related parameters were obtained: (1) integrated diffuse scattering intensity of 0.1480 for #SL400, 0.1208 for #SL300, and 0.0882 for #SL200; (2) defect size: (2.5-3) μm × (2.5-3) μm -#SL400 and #SL200, (3.2-3.4) μm × (3.7-3.9) μm -#SL300; (3) defect diameter: ~1.84 μm -#SL400, ~2.45 μm -#SL300 and ~2.01 μm -#SL200; (4) defect density: 1.42 × 10 6 cm -2 -#SL400, 1.01 × 10 6 cm -2 -#SL300, 0.51 × 10 6 cm -2 -#SL200; (5) diameter of stacking faults: 0.14 μm and 0.13 μm for #SL400 and #SL200, 0.30 μm for #SL300.

We investigate molecular beam epitaxy (MBE) growth conditions of micrometers-thick In 0.52 Al 0.48 As designed for waveguide of InGaAs/InAlAs/InP quantum cascade lasers. The effects of growth temperature and V/III ratio on the surface morphology and defect structure were studied. The growth conditions which were developed for the growth of cascaded In 0.53 Ga 0.47 As/In 0.52 Al 0.48 As active region, e.g., growth temperature of T g = 520 °C and V/III ratio of 12, turned out to be not optimum for the growth of thick In 0.52 Al 0.48 As waveguide layers. It has been observed that, after exceeding ~1 µm thickness, the quality of In 0.52 Al 0.48 As layers deteriorates. The in-situ optical reflectometry showed increasing surface roughness caused by defect forming, which was further confirmed by high resolution X-ray reciprocal space mapping, optical microscopy and atomic force microscopy. The presented optimization of growth conditions of In 0.52 Al 0.48 As waveguide layer led to the growth of defect free material, with good optical quality. This has been achieved by decreasing the growth temperature to T g = 480 °C with appropriate increasing V/III ratio. At the same time, the growth conditions of the cascade active region of the laser were left unchanged. The lasers grown using new recipes have shown lower threshold currents and improved slope efficiency. We relate this performance improvement to reduction of the electron scattering on the interface roughness and decreased waveguide absorption losses.

Switchable, double wavelength generation is demonstrated from a single vertical external cavity surface-emitting laser chip. Power of ~0.5 W for two wavelengths λ≈967 nm and 1,018 nm i.e. within the spectral distance of 51 nm were registered. In the semiconductor heterostructure a single set of nominally identical quantum wells was enclosed in a single, two-mode resonant microcavity. The wavelength switching was induced by the change of the pump power. The increase or decrease of the pump power changes the active region temperature and thus tunes spectrally the gain spectrum to the one of two modes.