Near-field dynamics of broad area diode laser at very high pump levels

Near-field properties of the emission of broad area semiconductor diode lasers under extremely high pumping of up to ∼50 times the threshold are investigated. A transition from a gain to thermally-induced index guiding is shown under operation with single pulses of 300 ns duration. At highest output powers, catastrophic optical damage is observed which is studied in conjunction with the evolution of time-averaged filamentary near-field properties. Dynamics of the process is resolved on a picosecond time scale

Thermal properties of high power laser bars investigated by spatially resolved thermoreflectance spectroscopy

In this work we present results of the analysis of thermal properties of high-power laser bars obtained by spatially resolved thermoreflectance (TR) spectroscopy. Thermoreflectance is a modulation technique relying on periodic facet temperature modulation induced by pulsed current supply of the laser. The periodic temperature change of the laser induces variation of the refractive index and consequently modulates probe beam reflectivity. The technique has a spatial resolution of about 1 m and can be used for temperature mapping over 300 m 300 m area. Information obtained in these experiments provide an insight into thermal processes occurring at devices' facets and consequently lead to increased reliability and substantially longer lifetimes of such structures

Формирование предпринимательских умений студентов инженерного вуза

Представлена методика формирования предпринимательских умений студентов инженерного вуза на основе практико-ориентированной подготовки, способствующей внедренческой деятельности инженера в современных условиях. Проведен анализ состояния проблемы формирования предпринимательских умений в России. Определены педагогические условия, способствующие формированию готовности студентов технического университета к комплексной инженерной деятельности. Сформулировано понятие предпринимательской компетенции инженера. Обосновано эффективное применение метода проектов для формирования предпринимательских умений студентов инженерного вуза. Представлена модель формирования предпринимательских умений студентов инженерного вуза с учетом проектной деятельности инженера.The developing methods of entrepreneurial competences of engineering students, based on the practice-oriented training to encourage an implemental activity of an engineer in the modern context has been presented in the report. The analysis of the problem of entrepreneurial competencies development in Russia has been carried out. The pedagogical conditions encouraging the commitment of the technical university students for an integrated engineering activity has been defined. The concept of entrepreneurial competencies of an engineer has been stated. An effective appliance of project methods to develop entrepreneurial competences of the engineering university students has been proved. There has been presented the development model of entrepreneurial competences of engineering students

Photoluminescence lineshape of ZnO

The merger of the absorption coefficient dispersion, retrieved from transmission by the modified Urbach rule introduced by Ullrich and Bouchenaki [Jpn. J. Appl. Phys. 30, L1285, 1991], with the extended Roosbroeck-Shockley relation reveals that the optical absorption in ZnO distinctively determines the photoluminescence lineshape. Additionally, the ab initio principles employed enable the accurate determination of the carrier lifetime without further specific probing techniques

Comparison of catastrophic optical damage events in GaAs- and GaN-based diode lasers

Damage patterns caused by Catastrophic Optical Damage (COD) are analyzed in GaN-based high-power diode lasers. We find the process to result in material loss including the formation of an empty channel. This is consistent with the observation of ejections of hot material out of the front facet of the device during COD. In the immediate vicinity of the empty channel, the laser structure seems to be absolutely undisturbed. These results are compared with earlier results from comparable experiments obtained with GaAs-based devices. While the COD process in both material systems follows similar scenarios and root causes, the damage pattern differs substantially. The completely empty channel at the position of the optical mode is in striking contrast to the results of earlier studies in GaAs-based devices, degraded under almost identical conditions. There molten, phase segregated, and both recrystallized and amorphous materials with well-pronounced melting fronts are observed. In the GaN-based devices we observe average defect front propagation velocities along the laser axis of 110 m/s. This is faster by a factor of 4-5 than what has been observed in GaAs-based devices under comparable experimental conditions

Accelerated Degradation of High Power Diode Lasers Caused by External Optical Feedback Operation

We present results of investigations on high power broad area lasers in the spectral range between 780nm and 1060nm with different antireflection coatings on the outcoupling facet. Comparative life tests on high power semiconductor laser bars and single emitters with and without external optical feedback delivered significantly different results. Depending on the emission wavelength, we found different degradation rates and failure modes such as accelerated gradual degradation and catastrophic optical mirror damage caused by different energy reabsorption scenarios with respect to the energy gap of the substrate material