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Room temperature, single mode, pulsed emission from two-section coupled cavity InGaAs/AlGaAs/GaAs quantum cascade laser fabricated by focused ion beam processing is demonstrated and analyzed. The single mode emission is centered at 1059.4 cm–1 (9.44 µm). A side mode suppression ratio of 43 dB was achieved. The laser exhibits a peak output power of 15 mW per facet at room temperature. The stable, single mode emission is observed within temperature tuning range, exhibiting shift at rate of 0.59 nm/K. [ABSTRACT FROM AUTHOR]

X-ray diffraction investigations of type II InAs/GaSb superlattice on a GaSb(001) substrate are presented. The wide range of diffraction angles (2θ/ω scans) covering 002 and 004 reflections was examined at Petra III synchrotron. The angular region between 002 and 004 reflections was the most interesting part of the measured diffraction profile. In this region, a non-coincidence of superlattice satellite peaks belonging to these two reflections is observed. The multiple-beam dynamical diffraction approach was used for correct simulation of the observed diffraction profile. [ABSTRACT FROM AUTHOR]

We have investigated the influence of As-soak parameters at InAs-on-GaSb interfaces on the structural and optical parameters of InAs/GaSb superlattices (SLs). The lattice-matched SLs were obtained for two sets of technological parameters. For a long As-soak time of 12.0 s and high V/III ratio of 10, the photoluminescence (PL) analysis indicates the presence of a non-radiative recombination channel. For a shorter time of 2.8 s and a reduced V/III ratio of 5.6, the PL excitation power dependence is close to that relevant for a clear excitonic recombination. The spectral blueshift of the bandgap energy of 23 meV was observed for SLs with GaAs-like interface thicknesses of 0.4 ML and 1.0 ML and other fixed parameters. [ABSTRACT FROM AUTHOR]

The accurate determination of the chemical composition of multicomponent antimonide layers still remains difficult. The problem becomes even more complicated when group III antimonides are grown in a MBE chamber that is also used for the growth of group III arsenides. In this paper, the composition of MBE grown AlGaAsSb layers is investigated in the context of unintentional arsenic incorporation. Control of the As concentration and a determination of the AlGaSb composition are crucial for an accurate calculation of the AlGaAsSb stoichiometry. It has been found that when using diffraction measurements with an As detection limit of 0.087%, the Al content in Al0.5Ga0.5Sb is determined with an accuracy of ±1%. Taking into account the GaSb reference from secondary ion mass spectrometry, the accuracy can be increased to ±0.52% of Al. The Al/Ga ratio determined for AlGaSb layers is further used for the calculation of the As content in AlGaAsSb alloys grown under the same technological conditions as the ternary layer. As a result, the procedure for the accurate determination of stoichiometry coefficients in this material is recommended. [ABSTRACT FROM AUTHOR]

Abstract: The lifetimes of the excited states belonging to the chiral partner bands built on the configuration in 126Cs have been measured using the DSA technique. For the first time the large set of the experimental transition probabilities is in qualitative agreement with all selection rules predicted for the strong chiral symmetry breaking limit. The selection rules originate from two general features of a chiral nucleus, namely, from the existence of well separated left- and right-handed systems built of three angular momentum vectors and extra symmetries appearing in addition to the chiral symmetry breaking. The staggering resulting from these additional symmetries is sensitive to triaxiality of odd–odd nuclei as well as configuration of valence particles. [Copyright &y& Elsevier]

Lifetimes of the yrast levels with spins I π = 23/2− to 39/2− in 129La produced via the 120Sn(14N, 5 n) reaction at a beam energy of 77MeV have been measured by the Doppler shift attenuation method. The properties of the studied levels belonging to the πh11/2 band were compared with the theoretical predictions obtained in the framework of the core quasi-particle coupling model. It is suggested that the rigid-rotor model used to describe the cores is too simplified as the even-even nuclei from the A ∼ 130 region are susceptible to shape deformation. Reasonable agreement was obtained with the phenomenological cores based on the experimental data of 128Ba. [ABSTRACT FROM AUTHOR]

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.