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Objectives: To investigate the natural courses of mild, moderate and severe idiopathic oligozoospermia, and which factors or semen variables were of utmost importance in predicting the courses. Methods: A total of 208 men (age 29–47 years) who were diagnosed with mild, moderate and severe idiopathic oligozoospermia in a 9-year-period between January 2000 and December 2008 were followed up for more than 6 months. Results: Overall, 16 (24.6%) of 65 patients with severe oligozoospermia developed azoospermia, whereas two (3.1%) patients with moderate oligozoospermia developed azoospermia and none of the patients with mild oligozoospermia developed azoospermia. Initial follicle stimulating hormone level and testicular volume between the subgroups were significantly different (P = 0.0071 and 0.0039, respectively). The subgroup of patients who became azoospermic (n = 18) showed statistically significant differences in terms of body mass index and the level of prolactin (PRL) from the subgroup that maintained the initial lingering sperm count (n = 190; P = 0.0086 and 0.0154, respectively). As the vitality of semen variables increased 1%, the risk of progression to azoospermia diminished by 0.892-fold, according to Cox's proportional hazards model analysis. A receiver operating characteristic curve analysis showed that the area under the curve was 0.755 and the sperm concentration value with the highest sensitivity and specificity was the reference value of 3–5 million/mL, with a sensitivity of 0.746 and specificity of 0.711 (P = 0.01). Conclusions: Patients with severe oligozoospermia should be warned of the possibility of becoming azoospermic and hence sperm freezing should be encouraged as early as possible.

We present an experimental and theoretical investigation of the temperature dependence of the threshold current for double quantum well GaInNAs-GaAs lasers in the temperature range 10 degC-110 degC. Pulsed measurements of the threshold current have been performed on broad and narrow ridge wave guide (RWG) lasers. The narrow RWG lasers exhibit high characteristic temperatures (T0) of 200 K up to a critical temperature (Tc), above which T0 is reduced by approximately a factor of 2. The T0-values for broad RWG lasers are significantly lower than those for the narrow RWG lasers, with characteristic temperatures on the order of 100 (60) K below (above) Tc. Numerical simulations, using a model that accounts for lateral diffusion effects, show good agreement with experimental data and reveal that a weakly temperature dependent lateral diffusion current dominates the threshold current for narrow RWG lasers.

A state-of-the-art laser diode simulation tool has been used to investigate how phonon reflection at epitaxial interfaces impacts upon the performance of high-power 980 nm ridge waveguide lasers. Due to the inclusion of phonon reflection, a 0.5 K increase in quantum well temperature and a reduction in front facet output power of up to 0.6 mW is observed. The results demonstrate that whilst this effect is relatively small, a first order correction should be made to obtain accurate simulation results.

A systematic study of the dependence of the optical gain on the injection current and temperature in InGaAsN/GaAs lasers has been performed. The amplified spontaneous emission has been measured from a series of both facet-coated and uncoated 1.3 μm edge-emitting double quantum well lasers. The net gain, modal gain, cavity loss, quasi-Fermi level separation and width of the gain spectra have been extracted using Cassidy's method. The peak gain was found to shift 0.41 nm/K between 300 K and 340 K and 0.60 nm/K between 340 K and 380 K. The value of the peak gain was found to decrease with temperature at a rate of 0.26 cm−1/K. The increase in the full at width half maxima of the gain spectra was determined to be 0.35 nm/K. These values are all comparable to those found for the more traditional 1.3 μm InP-based devices, suggesting that InGaAsN/GaAs lasers are a viable alternative to replace such InP-based devices, in particular for uncooled access network applications. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A theoretical investigation into the impact of the thermal boundary resistance on the performance of uncooled edge-emitting 1.3μm InGaAsN/GaAs quantum well lasers has been performed. A state-of-the-art 2D laser diode simulation tool has been extended to accurately model the thermal resistance due to the acoustic material mismatch and defect scattering at epitaxial interfaces. A small, but noticeable, increase in quantum well temperature is observed. The results clearly highlight the need for the inclusion of thermal boundary resistance in device simulation tools. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The net modal gain, effective group index and linewidth enhancement factor (LWEF) in edge-emitting InGaAsN/GaAs lasers have been determined as a function of both temperature and injection current from experimentally amplified spontaneous emission spectra. The shift of the peak gain with temperature was found to be 0.49 nm/K. Values of effective group index between 3.52 and 3.59 were measured, suggesting a relatively high refractive index of 3.75 for a dilute nitride quantum well. LWEF values between 1.87 and 2.84 were measured.

The simulation of double quantum well (QW) GalnNAs ridge-waveguide (RW) lasers is performed over a wide range of cavity lengths and operating temperatures using a comprehensive in-house 2D laser simulator that takes into account all of the major device physics, including current spreading, capture escape processes, drift diffusion in the QW, 2D optical modes and fully resolved lasing spectra. The gain data used by the simulator were fitted to experimental gain spectra measured by the segmented contact method. The gain model includes the band-anticrossing model for the conduction band and a 4 x 4 kldrp model for the valence band. Using a carrier density-dependent and temperature-dependent linewidth broadening parameter, a good fit with experiment over a temperature range of 300-350 K was obtained. A Shockley-Read-Hall (SRH) lifetime of 0.5 ns and an Auger recombination coefficient of 1 x 10-28 cm6/ s, were extracted from the calibration of the laser simulator to experimental device characteristics of broad-area (BA) devices. Using the same set of parameters for BA devices, except for a reduced SRH lifetime of 0.45 ns underneath the etch, 2D simulation results were found to agree well with the measured RW laser operating characteristics. The impact of the various recombination processes in the RW laser at threshold has also been identified using the calibrated laser simulator.

This paper presents a model for simulating the impact of external optical feedback on large-optical cavity high-brightness diode lasers. The simulations are performed with our 2.5D simulation tool for high-brightness laser diodes. The external cavity is modelled using commercial coherent ray tracing software. We consider the impact of the optical feedback on the excitation of amplified spontaneous emission in the parasitic vertical modes.

Using a quantitatively calibrated imaging system and specially fabricated tapered lasers with windowed n-contacts, the authors image the spontaneous emission distribution inside two different laser cavities as a function of injection current. In the first device, an array of narrow-angle index-guided tapered lasers, significant thermal and electrical coupling between the emitters was observed. In the second device, a wide-angle gain-guided tapered laser, significant spatial hole burning was observed above threshold. The spontaneous emission distributions of this wide-angle device have been compared with simulation results from a 2.5D laser simulator and show good quantitative agreement in the quantum well carrier density.

In this work, an ultracompact electro-optic modulator based on refractive index modulation by plasma dispersion effect in PhC all-optical gate (AOG) is proposed. The index modulation is achieved by applying a time-varying bias voltage across the electrical contacts of the AOG. The proposed modulator has potential for high-speed operation, with bandwidths in excess of 30GHz achievable.

We present results from measurements of the subthreshold lateral spontaneous emission profile in 1.3-mu m wavelength ridge waveguide InGaNAs quantum-well lasers using a scanning near-field optical microscopy technique. The measurements reveal the presence of significant lateral carrier diffusion which has a profound effect on the temperature dependence of the threshold current. This effect is frequently omitted when the characteristic temperature of the threshold current is considered.

We report on the design and simulation of high-power, high-brightness laser diodes and bars. Bar level simulations are demonstrated revealing important consequences of current competition and thermal crosstalk. We also demonstrate bidirectional coupling with external cavity optics, with the aim of evaluating the performance of full laser systems.

In 2D and quasi-3D simulations, Fermi-level pinning of the surfaces has been found to result in the decoupling of the electron and hole populations, preventing numerical convergence to the correct solution. In this work, we report on the elimination of numerical underflow in the self-consistent solution of the Poisson and continuity equations in a 2D optoelectronic device simulator. The use of extended precision to represent the state variables eliminates the numerical underflow and consequently the decoupling of the electron and hole populations.

We describe passive phase-locking architectures based on external-cavity setups to improve the brightness of diode laser bars. Volume Bragg gratings are used to stabilize the lase line. Numerical modelling and experimental results will be presented., Comment: High Power Diode Lasers and Systems, Coventry : United Kingdom (2009)

In conclusion, we have shown that it is possible to provide selective feedback to a particular lateral mode from the external cavity using an asymmetric feedback technique. The simulation and experiment show a good agreement with respect to spatial hole burning and the far-field distribution.

In this work, we have presented a description of our spectral laser model and performed spectroscopic simulations of a 975 nm tapered laser diode. To verify the ASE model, we checked the extracted gain using the variable stripe length method. A good agreement between the simulated and measured emission linewidth could be obtained using a spontaneous emission coupling factor of 1×10−16. The simulated red-shift in the peak emission wavelength with increasing bias is consistent with experiment and is attributed to self-heating effects.

A one dimensional spectral model of a self-organizing external cavity laser diode with a PR crystal in the external cavity was developed. The model combines the photon-carrier density coupled rate equations model and a plane wave PR crystal model. The model confirms that the self-organizing external cavity laser diode operates in a single longitudinal mode with an output power up to 0.55 W

We have demonstrated the simulation tool for both single and multiple emitters. Investigations of a model bar with a non-uniform temperature distribution showed that the hotter emitters at the centre of the bar drew more current and emitted higher powers, but also degraded faster than the cooler edge emitters. Similar behaviour has been observed experimentally. However, the simulation results for a real bar showed poor agreement with the observed power distribution. This was attributed to thermal crosstalk between the emitters and is being addressed by the introduction of a global thermal model to Barlase.

Dilute-nitride lasers with record performances have been used to build uncooled transceivers and failure free 10 Gb/s optical transmission was achieved over 815 m of multimode Corning InfiniCor fiber under the LRM standard.

In this work we have measured the lateral spontaneous emission profile for the lasers, using scanning near-field optical microscopy (SNOM). Since the near-field of the spontaneous emission maps the lateral carrier distribution in the active region, this measurement provides a way to directly measure the lateral diffusion. The obtained profile therefore represents the optical mode which is well confined beneath the ridge. Carriers that diffuse outside the ridge can hence not contribute to optical gain and are therefore associated with a leakage current.

A self-consistent model of a self-organizing external cavity high power laser is presented. The model consists of a photorefractive crystal model, which relies on the plane wave approximation, and of a spectral model of the tapered laser amplifier. The results show that the laser can operate in a single longitudinal mode.

Objective We aimed to investigate the prevalence of erectile dysfunction (ED) and the usage of phosphodiesterase type 5 (PDE5) inhibitors for ED treatment in infertile couples. Methods A total of 260 male partners in couples reporting infertility lasting at least 1 year were included in this study. In addition to an evaluation of infertility, all participants completed the International Index of Erectile Function (IIEF)-5 questionnaire to evaluate their sexual function. The participants were asked about their use of PDE5 inhibitors while trying to conceive during their partner's ovulatory period and about their concerns regarding the risks of PDE5 inhibitor use to any eventual pregnancy and/or the fetus. Results Based on the IIEF-5 questionnaire, 41.5% of the participants (108/260) were classified as having mild ED (an IIEF-5 score of 17-21), while 10.4% of the participants (27/260) had greater than mild ED (an IIEF-5 score of 16 or less). The majority (74.2%, 193/260) of male partners of infertile couples had a negative perception of the safety of using a PDE5 inhibitor while trying to conceive. Only 11.1% of men (15/135) with ED in infertile couples had used a PDE5 inhibitor when attempting conception. Conclusion ED was found to be common in the male partners of infertile couples, but the use of PDE5 inhibitors among these men was found to be very low. The majority of male partners were concerned about the risks of using PDE5 inhibitors when attempting to conceive. Appropriate counseling about this topic and treatment when necessary would likely be beneficial to infertile couples in which the male partner has ED.

In this work, we optimize the thermal performance of a double quantum well GalnNAs ridge waveguide laser using an accurate in-house 2D electro-opto-thermal laser simulator. The simulator has shown good agreement with experiments after a detailed calibration procedure. Using calibrated material parameters, we investigate the influence of the p-cladding doping concentration on the heat generation within the laser. It is found that due to the competition between Joule and free carrier absorption heating, an optimum p-cladding doping concentration/profile exists.

This paper describes new design schemes for a telecommunication management network (TMN) agent for man machine language (MML)-managed network elements (NE), especially for ATM networks. Most of the currently developed ATM switches have simple MML interfaces for local operator crafts. This means that most operations, administration, maintenance, and provisioning (OAM&P) functions reside within the NE itself, and designing a TMN agent as a proxy is considered to be most appropriate in that more intelligent event correlation and filtering can be done in the NE itself. In TMN environment, proxy-based management expects an agent to have a functionality of a Q adaptation function (QAF), rather than a network element function (NEF) itself. In contrast with NEF, QAF can be simplified by focusing on the message conversion, namely adaptation and mediation, between standard CMIP messages and proprietary MML messages or any kind of management messages. Based on this observed fact, this paper proposes several design schemes for a Q3 agent and its companion gateway function, so that a Q3 agent, as a proxy, can rather be lightweight and mediation-insensitive. The design schemes proposed in this paper are listed in the following: designing management protocol-insensitive schema for an NE-embedded database (DB), mapping of a management information base (MIB)/management instances tree (MIT) accesses to DB queries and making direct use of DB queries, minimizing the retained information on MIT/MIB, and using GDMO/ASN.1-based MML mediation capabilities with various message adaptation capabilities.

We report on the simulation of high-power laser bars and the emulation of their ageing behaviour, using simulation tools originally developed for single emitter laser diodes. Simulations of a simplified bar indicated that the hotter emitters located at the centre of the bar emit more power than their cooler neighbours, while degradation emulations showed that the centre emitters degrade faster. Although the degraded emitters produced less light, they drew an increasingly large fraction of the total current. These insights into the operation and degradation of the bar motivated new experimental investigations, which confirmed the predicted behaviour.

A robust opto-electronic device simulation tool is extended to model the phonon bottleneck in edge-emitting 1.3µm InGaAsN double quantum well (QW) laser diodes. Both the steady state operation and the transient response of the phonon bottleneck are examined as a function of injection current and heatsink temperature. It is found that the hot phonon population can raise the electron and hole temperatures in the QW active region by up to 7K above the equilibrium lattice temperature at moderate injection currents. At high injection currents, it is found that the phonon bottleneck can significantly decrease the optical power.

Lawrence Livermore Laboratory is developing an assessment procedure to evaluate the effectiveness of a potential nuclear facility licensee’s material control (MC) system. The purpose of an MC system is to prevent the theft of special nuclear material such as plutonium and highly enriched uranium. The key in the assessment procedure is the generation and analysis of the adversary event sets by a directed graph and fault-tree methodology. The methodology is described step-by-step and its application illustrated by an example.

In this work, we present a scheme to accelerate the convergence of a quasi-3D spectral laser diode simulator. It is demonstrated that the acceleration scheme allows the number of Fox-Li roundtrips to be substantially reduced. The accelerated spectral laser model is then used to simulate a narrow index guided 980nm tapered laser. The width of the simulated emission spectra is found to agree well with the measured spectra using an appropriate value of the spontaneous emission coupling factor.

The process of refractive index grating formation in a photorefractive crystal, used as the self-adapting spectral filter in an external cavity laser, is studied with a self-consistent model. The model is based on the Finite Difference solution of the Kukhtarev equations. The results obtained are compared with approximate analytical models.

The 3D Printing (3DP) industry has been receiving increased public attention. Many companies are seeking ways to develop new means of creating and disseminating 3DP content, in order to capture new business opportunities. To date, however, the true business opportunities of 3DP have not been completely uncovered. This research explores the challenges posed in the development and deployment of 3DP, and focuses on China which is still the main manufacturing hub in the world. By means of empirical semi-structured interviews with 3DP companies in China, the current application of 3DP technology in the industry and the associated challenges are investigated. Although many companies can see the benefits of 3DP, its potential has not been delivered as promised. Several areas have been identified that could be improved further. The interviews with 3DP companies are used to learn about the gap between the 3DP technology in depth, and 3DP industrial applications which can further improve the growth of the 3DP industry.