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The aim of the work was to study the dynamics of lactate dehydrogenase (LDH; EC 1.1.1.27), aconitase (AH; EC 4.2.1.3), NAD-dependent malate dehydrogenase (MDH; EC 1.1.1.37), succinate dehydrogenase (SDH; EC 1.3.99.1) activity in homogenates and sub-fractions of brain structures of rat prenatally endured hypoxia at the organogenesis stage (on 11–15 days of development) and their role in the formation of compensatory — adaptive mechanisms in brain in postnatal ontogenesis. It was revealed that increasing of lactate dehydrogenase and malate dehydrogenase activity (P < 0.001; P < 0.01, correspondently) in the brain structures of the rats prevented metabolic disturbances in the regulation mechanisms of biosynthetic and bioenergetics processes in the brain. It was shown that prenatal hypoxia upregulates aconitase activity in postnatal development and this process, probably, had a reversible character (P < 0.01), the highest indices of succinate dehydrogenase activity were noticed in the hypothalamus and cerebellum of 30-day-old rat as compared to the other structures (P

This paper analyzes 2D photonic crystal surface-emitting laser diodes with void-containing and all-semiconductor structures by comparing their simulated mode distribution, band structure, and coupling coefficients. A photonic crystal design with a square lattice and circle atoms is considered.

Opportunities for the monolithic integration of a novel common quantum dot (QD)-active electroabsorption modulated laser are explored. An electric-field and temperature-dependent spectroscopic study of optical absorption and gain are presented in the state-of-the-art 1.3- $\mu \text{m}$ In(Ga)As/GaAs QD active material. The unique gain/absorption spectral shape, attributed to the QD’s density of states, allows for a number of possible modulation schemes dependent upon the selected laser wavelength detuning from the gain peak. Intensity modulation and change in absorption, leading to negative chirp operation, are demonstrated via absorption spectroscopy and gain measurement of eight-layer-stack QD-active material. Such a device would be able to provide positive or negative chirp dependent upon modulation scheme and gain/Bragg wavelength detuning.

We present an InP-based epitaxially regrown photonic crystal surface emitting laser diode, lasing in quasi- CW conditions at 1523nm., Comment: 4 pages, 5 figures, journal submission for review

Photonic crystal surface emitting lasers (PCSELs) are a new class of laser diode, offering control over emission (wavelength, polarisation, beam shape) through photonic crystal design, as well as power scalability and low beam divergence. We present developments in 2D arrays of large scale (~150x150um) PCSELs, coherently coupled by 1mm long, 100 μm wide waveguides that can be electrically driven into loss or gain. By studying the spectral and current-power characteristics, we show coherent power scaling between multiple devices. We discuss injection locking between devices achieved through controllable 2D in-plane feedback and its effect on the near and far field emissions.

We present our recent results on quantum dot-based VCSELs for O-band telecoms applications. The incorporation of Sirich SiN $_{x} /$SiO 2 distributed Bragg mirrors, which have been studied by spectroscopic ellipsometry, as well as using high-contrast SiN $_{x}1\mathrm {D}$ gratings will lead to a significant size reduction desirable for the fabrication.

In this paper, we show the effect of lateral external\ud optical feedback on an all semiconductor photonic crystal surface\ud emitting laser (PCSEL). Initially, a PCSEL is grown and fabricated\ud with a square lattice of triangles, the device is shown to\ud operate electrically driven at room temperature under continuous\ud wave condition. We investigate, theoretically and experimentally,\ud the effect of lateral feedback on the performance of photonic crystal\ud lasers. Demonstrating a reduction in mode competition and\ud a modification to spatial mode distribution, opening routes to all\ud electronic beam shaping and divergence control.

The main purpose of this study is to experimentally investigate the transient heat transfer from a fluid stored inside a closed reservoir. Different cooling methods, i.e. the use of metal foam embedded tube, helical tube, and a straight tube, are used and compared for heat transfer from the fluid reservoir. CuO/water nanofluid in various volume fractions in the range of 0–0.2 (w/v) are also employed as cooling fluid. The experimental data shows a heat transfer enhancement of 42% and 45% for helical tube and metal foam tube respectively, as compare with the straight tube by using 0.2% (w/v) Cuo/water nanofluid. The experiments indicate that combination of the two presenting methods (metal foam/helical shape and nanofluids) has a significant capability to enhance the heat transfer rate. Finally, two correlations between Rayleigh number and non-dimensional heat flux are presented for the straight and porous tubes.

The article presents the results of the analysis of the hydrocarbon potential (KH) of the Lower Pliocene sediments (Productive series (PS) in the Azerbaijan sector and Red colored series in the Turkmenistan (RS)) and the temperature conditions for its realization within the Absheron-Pribalkhan uplift zone. The analysis is based both on the study of the regularities of changes of temperature in the space, and on the directly evaluation of maturity of organic matter (HC) in the rock. As a result of the studies carried out, the low hydrocarbon potential of the Lower Pliocene sediments (PS-RS) and the epigenetic nature of the main hydrocarbon resources of the South Caspian Basin are confirmed. Two temperature zones are distinguished within the Absheron-Pribalkhan zone, the boundary between which passes along the supposed deep break fault between the structures of Neft-Dashlary and Gunashly. In accordance with the revealed zonality in the NW of the part of the zone, the upper threshold for the beginning of oil generation is timed to a depth of approximately 2.8 km and in SE it is submerged to a depth of approximately 4.5 km. On the whole, the organic matter of the Lower-Pliocene rocks within the Absheron-Pribalkhan zone, in the considered depth interval, is characterized by low maturity and is below the "oil window".

The realization of a 1 × 2 coherently coupled photonic crystal surface emitting laser array is reported. New routes to power scaling are discussed and the electronic control of coherence is demonstrated.

We simulate the shape of the density of states (DoS) of the quantum dot (QD) ensemble based upon size information provided by high angle annular dark field scanning transmission electron microscopy (HAADF STEM). We discuss how the capability to determined the QD DoS from micro-structural data allows a MonteCarlo model to be developed to accurately describe the QD gain and spontaneous emission spectra. The QD DoS shape is then studied, with recommendations made via the effect of removing, and enhancing this size inhomogeneity on various QD based devices is explored.

Incorporation of a GaAs0.8P0.2 layer allows strain balancing to be achieved in self-assembled InAs/GaAs quantum dots (QDs) grown by metal organic vapor phase epitaxy. Tuneable wavelength and high density are obtained through growth parameter optimization, with emission at 1.27 μm and QD layer density 3 × 10 10 cm–2. Strain balancing allows close vertical stacking (30 nm) of the QD layers, giving the potential for increased optical gain. Modeling and device characterization indicates minimal degradation in the optical and electrical characteristics unless the phosphorus percentage is increased above 20%. Laser structures are fabricated with a layer separation of 30 nm, demonstrating low temperature lasing with a threshold current density of 100 A/cm2 at 130 K without any facet coating.

All-semiconductor photonic crystal surface-emitting lasers (PCSELs) operating in CW mode at room temperature and coherently coupled arrays of these lasers are reviewed. These PCSELs are grown via MOVPE on GaAs substrates and include QW active elements and GaAs/InGaP photonic crystal (PC) layer situated above this active zone. Atoms of triangular shapes have been shown to increase optical power from the PCSEL but are also shown to result in a competition between lasing modes. Simulation shows that the energy splitting of lasing modes is smaller for triangular atoms, than for circles making high power single-mode devices difficult to achieve. In this work we experimentally investigate the effect of lateral optical feedback introduced by a facet cleave along one or two perpendicular PCSEL edges. This cleavage plane is misaligned to the PC resulting in a periodic variation of facet phase along the side of the device. Results confirm that a single cleave selects the lowest threshold 2D lasing mode, resulting in a ~20% reduction in threshold current and favours single-mode emission. The addition of a second cleave at right-angles to the first has no significant effect upon threshold current. The virgin device is shown to have a symmetric far-field (1 degree) whilst a single cleave produces a 1 degree divergence perpendicular to cleave and 5 degree parallel to cleave. The second orthogonal cleave results in the far field becoming symmetric again but with a divergence angle of 1 degree indicating that single-mode lasing is supported over a wider area.

Electronic control of coherence in 2D arrays of photonic crystal surface emitting lasers is discussed.

We demonstrate GaAs-based superluminescent diodes (SLDs) incorporating a window-like back facet in a self-aligned stripe. SLDs are realised with low spectral modulation depth (SMD) at high power spectral density, without application of anti-reflection coatings. Such application of a window-like facet reduces effective facet reflectivity in a broadband manner. We demonstrate 30mW output power in a narrow bandwidth with only 5% SMD, outline the design criteria for high power and low SMD, and describe the deviation from a linear dependence of SMD on output power as a result of Joule heating in SLDs under continuous wave current injection. Furthermore, SLDs processed normal to the facet demonstrate output powers as high as 20mW, offering improvements in beam quality, ease of packaging and use of real estate. © (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We describe a study of electro-absorption effects in high quality 1300nm InAs/GaAs quantum dot (QD) material grown by molecular beam epitaxy. The photocurrent spectra as a function of electric field is investigated and the quantum confined Stark shift of the QD states is compared to reports for various quantum well (QW) systems (GaAs/AlGaAs, InGaAs/GaAs, InGaAsP/InP). We show that the rate of shift of the QD absorption peak is smaller than that of the reported QW systems (~0.1 meV/kVcm-1 c.f. 0.15-0.2 meV/kVcm- 1) and that the QD ground-state absorption is comparatively insensitive to the applied electric field. We observe a strong QD absorption peak at all biases up to avalanche breakdown, which is not observed in previous reports for these QW systems.

Circular mesa GaAs p+–i–n+ diodes for photon counting soft X-ray spectroscopy have been fabricated and characterised over a temperature range of +80 to –30 °C. The spectroscopic performance of the diodes, as measured by the FWHM of the Mn Kα X-ray line from an 55Fe radioisotope, is reported. In addition, we compare the GaAs diodes with previously fabricated and characterised Al0.8Ga0.2As p+–i–n+ diodes of similar geometry.

We describe a high angle annular dark field scanning transmission electron microscopy study of a self-assembled InAs-GaAs quantum dot (QD) laser sample providing insight into the micro-structure of the QD ensemble. A size distribution anisotropy of the QDs is observed in the two orthogonal (110) planes, and this structural information is used to develop a density of states model for the QD ensemble which is shown to be in strong agreement with a range of optical spectroscopic measurements. This link between the micro-structure and optical properties allows routes to QD device simulation. We go on to discuss how changes to the micro-structure would affect the density of states and hence laser performance.We describe a high angle annular dark field scanning transmission electron microscopy study of a self-assembled InAs-GaAs quantum dot (QD) laser sample providing insight into the micro-structure of the QD ensemble. A size distribution anisotropy of the QDs is observed in the two orthogonal (110) planes, and this structural information is used to develop a density of states model for the QD ensemble which is shown to be in strong agreement with a range of optical spectroscopic measurements. This link between the micro-structure and optical properties allows routes to QD device simulation. We go on to discuss how changes to the micro-structure would affect the density of states and hence laser performance.

Effects of 137Cs gamma irradiation on the DC electrical characteristics of InAs/GaAs quantum dots (QDs) mesa diodes are reported. The devices were irradiated with gamma-rays for different doses ranging from 100 rad to about 1 Mrad (GaAs). The QDs mesa diodes are found to be tolerant to γ radiation. No enhanced leakage current and shift in the turn-on voltage were observed in the InAs/GaAs QD devices after exposure to γ-radiation. When irradiated by γ-rays continuously, there seemed to be a small degradation trend in the forward-bias current after irradiating the mesa diode for about six hours.

To conclude, the InAs/GaAs QD devices display radiation-tolerant DC characteristics despite high total dose of gamma radiation. No permanent ionising damage to the III–V compound semiconductor devices has been observed. The off-state leakage current is not worsened even when the device is continuously irradiated by gamma radiation. The results show great promise of InAs/GaAs QD structure for realization of IR photodetectors with low noise floor and high reliability in radiation environments.

We demonstrate a semiconductor PCSEL array that uniquely combines an in-plane waveguide structure with nano-scale patterned PCSEL elements. This novel geometry allows two-dimensional electronically controllable coherent coupling of remote vertically emitting lasers. Mutual coherence of the PCSEL elements is verified through the demonstration of a two-dimensional Young’s Slits experiment. In addition to allowing the all-electronic control of the interference pattern, this type of device offers new routes to power and brightness scaling in semiconductor lasers and opportunities for all-electronic beam steering.

In this work we report on the simulation of electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). We simulate an etched mesa structure (substrate emission) with the substrate acting as the current spreading layer. The effect of contact misalignment on the carrier distribution within the active element is explored and confirms the validity of the model in describing the carrier distribution. We go on to discuss the effects of the substrate thickness and trench depth on the intensity profile. Simulation results show that a thicker substrate and a trench partially etched into the substrate may improve the intensity profile in future devices.

We describe the development of hybrid quantum well (QW)/quantum dot (QD) active elements to achieve broad spectral bandwidth spontaneous emission and gain. We have previously reported that the placement of the QW within the active element is a critical factor in obtaining broad spectral bandwidth emission. We now present new designs to further broaden the spontaneous emission from hybrid structures by increasing the number of QD layers and dot density, and by using QDs with wider state-separation. Introducing chirped QD layers reduced the modulation in the spontaneous emission spectra, and by utilising self-heating effects and state-filling, a spontaneous emission with 3dB line-width of 350nm is obtained.

We previously demonstrated a hybrid quantum well/quantum dot structure to enhance the gain and spontaneous emission bandwidth of a quantum dot active region. We now present new designs to further broaden the spontaneous emission from hybrid QW/QD structure. Utilizing a high junction temperature, and chirped quantum dot layers with higher areal densities, increased layer number, and increased state separation a spontaneous emission FWHM of ~350nm is achieved.

A study of leakage currents and X-ray photon counting using GaAs p-i-n diodes is presented. Different fabrication techniques have been investigated, namely He implantation, partial wet etching and full wet etching. It was found that the partially etched diodes showed well-defined spectral peaks when exposed to a 55Fe radioisotope source and uniformly low leakage currents ideal for X-ray detector arrays.

We report on the performance of avalanche photodiodes (APDs) based on the wide band gap material AlGaAs which have been developed for soft X-ray spectroscopy applications. A number of diode types with different layer thicknesses have been characterised. The temperature dependence of the avalanche multiplication process at soft X-ray energies in Al 0.8 Ga 0.2 As APDs was investigated at temperatures from +80 °C to −20 °C. X-ray spectra from a 55Fe radioactive source show these diodes can be used for spectroscopy with promising energy resolution (0.9–2.5keV) over a wide temperature range. The temperature dependence of the pure electron initiated multiplication factor (M e ) and the mixed carrier initiated avalanche multiplication factor (M mix ) were experimentally measured. The experimental results are compared with a spectroscopic Monte Carlo model for Al 0.8 Ga 0.2 As diodes from which the temperature dependence of the pure hole initiated multiplication factor (M h ) is determined.

We demonstrate control by applied electric field of the charge states in single self-assembled InP quantum dots placed in GaInP Schottky structures grown by metalorganic vapor phase epitaxy. This has been enabled by growth optimization leading to suppression of formation of large dots uncontrollably accumulating charge. Using bias- and polarization-dependent micro-photoluminescence, we identify the exciton multi-particle states and carry out a systematic study of the neutral exciton state dipole moment and polarizability. This analysis allows for the characterization of the exciton wavefunction properties at the single dot level for this type of quantum dots. Photocurrent measurements allow further characterization of exciton properties by electrical means, opening new possibilities for resonant excitation studies for such system., Comment: 7 pages, 4 figures

New types of detectors based on the wide band gap material AlGaAs have been developed for soft X-ray spectroscopy applications. We report on the spectroscopic performance of simple p-i-n diodes and avalanche photodiodes (APDs). A number of diode types with different layer thicknesses have also been characterised. X-ray spectra from 55Fe and 109Cd radioactive sources show these diodes can be used for spectroscopy with promising energy resolution (1.0–1.25 keV) over a -30 to +90 °C temperature range. The temperature dependence of the avalanche multiplication process at soft X-ray energies in Al0.8Ga0.2As APDs was also investigated at temperatures from -20 to +80 °C. The temperature dependence of the pure electron initiated multiplication factor (Me) and the mixed carrier initiated avalanche multiplication factor (Mmix) were extracted from the X-ray spectra. The experimental results are compared with a spectroscopic Monte Carlo model for Al0.8Ga0.2As diodes from which the temperature dependence of the pure hole initiated multiplication factor (Mh) is determined. Monte Carlo simulations for the avalanche gain of absorbed X-ray photons have also been developed to study the relationship between avalanche gain and energy resolution for semiconductor X-ray avalanche photodiodes. The model showed that the distribution of gains, which directly affects the energy resolution, depends on the number of injected electron-hole pairs (and hence the photon energy), the relationship between the two ionization coefficients, and the overall mean gain. Our model showed that the conventional notion of APD gains degrading energy resolution significantly is incomplete. We compare the Monte Carlo simulations with experimental data from a number of different Al0.8Ga0.2As diodes.