Historical development trend of high-power laser diodes for recordable optical disc as CD-R and DVD-R is explained in a view point of not only how to realize highly reliable high-power operation but also how to adopt laser diodes into optical disc drives.
Long lifetime AlInP/GaInP 7W laser diode arrays with a uniform intensity distribution have been developed for a display system. With using this device and high pressure mercury lamp as a hybrid light source, we propose a new type of laser projection display.
We describe the use of continuous-wave semiconductor diode laser beam as a heating source in thin film deposition system. One of the examples is heating of organic materials for sublimation to replace conventional Knudsen cell. The other is heating of the substrate to very high temperature (>1000°C) which can hardly be achieved by conventional resistive or lamp heaters. Many of the advantages come from the pin-point heating on demand that is enabled by the excellent directionality of high power laser beam.
High power direct diode laser systems have an excellent advantage of high conversion efficiency. They have another advantage of an elliptical beam shape. This characteristic makes good welding feature for thin foil welding. In this paper, advantage of elliptical shape beam of high power direct diode laser and its application to thin foil welding in the microelectronics or micromechanical parts manufacturing.
200 kW laser diode pumping module aimed for IFE driver was developed. The pumping optics for the uniform irradiation was applied to this module. As a result, 80% filling factor for the pumping distribution was achieved. The maximum peak power of 226 kW was obtained at the 150 μs pump duration. The E-O conversion efficiency over 50% was achieved.
We have demonstrated high performance broad area single emitter lasers with window structure fabricated by newly developed impurity free vacancy disordering (IFVD) technique. Vacancies induce quantum well intermixing, leading to bandgap shift. We have succeeded in obtaining the large bandgap shift in window region and maintaining the original bandgap in gain region simultaneously. We can control the bandgap difference. A very high output power of 25.6W at 30A under pulsed operation was obtained without facet degradation. This is the one of the highest power for 100μm wide single emitter lasers. Moreover, no degradation and no sudden failure were observed for 5800 hours life test at 8W-20°C. We have, thus, realized the highest output power and high reliable lasers with window structure fabricated by IFVD.
Laser diodes for plastic optical fiber (POF) data links are required stable operation >100,000h at 60°C, 5mW and the transmission speed beyond 1Gbps. By optimizing crystal growth conditions and device structures, we have successfully fabricated highly reliable laser diodes with 1.25 Gbps transmission speed. The median lifetime for 5mW operation at 60°C was estimated to be more than 800,000h. These results indicate that 660 nm band laser diodes are very promising light sources for POF data links.
Monolithic dual-wavelength high-power laser diode is strongly required by DVD-R/CD-R dual optical disc drives for the purpose of not only cost reduction but also drive size minimization. In this paper, we will report on a newly developed monolithic dual-wavelength laser diode with output power exceeding 350mW from DVD and CD elements.
InGaAsSbN quantum well (QW) laser diodes on InP in 2μm wavelength region were grown by molecular beam epitaxy (MBE). It was found that increase in Sb composition improved properties of InGaAsSbN QW laser diodes. We observed electroluminescence at 4.51μm at room temperature for InAsSbN QW laser diodes, and laser operation at 2.31 2μm at 190K. Annealing effects were also studied.
Electrostatic discharge induced degradation is one of the serious reliability problems of GaInAsP/InP laser diode. The authors have conducted an analysis on electrostatic discharge induced degradation, and clarified the principal degradation mechanism. Main cause of degradation is heating by light absorption at the active layer facet. This phenomenon is similar to the catastrophic optical damage that occurs in a GaAs-based high power laser diode. This problem is more serious in recent tendency to high power demand. Therefore degradation suppression technology is extremely important. We focused on facet coating that is one of key process to suppress facet degradation. And we demonstrated that the facet degradation is successfully suppressed by inserting an aluminum ultra-thin layer between the semiconductor and dielectric coating films. This effect is caused by reduction in surface recombination. This degradation suppression technology has potential to be applied to not only GaInAsP/InP laser diode but arbitrary InP-based laser diode.
Proton beams with energies of 10MeV and 200MeV were irradiated onto red (GaInP) and infrared (AlGaAs) high power (broad stripe) semiconductor lasers. Threshold current increases with increasing proton fluence. The change of threshold current in infrared lasers is much larger than that in red lasers. The proton energy dependence of threshold current damage factor is consistent with that of Non-Ionizing Energy Loss to some extent. Forward bias annealing effects were observed.
We succeeded fabricating high-output-power blue (445nm) laser diodes (LDs) with an output power of 500mW. The operating current, voltage, wall-plug efficiency of these LDs were 480mA, 4.8V, and 21.7%. Estimated lifetime of these LDs was over 30,000 hours under continuous wave operation at 25°C.
We demonstrated AlGaN multi-quantum well (MQW) deep ultraviolet (UV) light-emitting diodes (LEDs) with wavelength in the range of 227.5-273 nm fabricated on high-quality AlN buffers on sapphire substrates grown by metal-organic chemical vapor deposition (MOCVD). We realized crack-free, thick AlN buffer on sapphire with low threading dislocation density (TDD) and atomically flat surface by using ammonia (NH3) pulse-flow multi-layer (ML) growth technique. We obtained single-peaked operation of the AlGaN-MQW LED with wavelength of 227.5 nm, which is the shortest wavelength of AlGaN-based LED on sapphire. The maximum output power and external quantum efficiency (EQE) of the 261 and 227.5 nm LEDs were 1.65 mW and 0.23% under room-temperature (RT) continuous-wave (CW) operation, and 0.15mW and 0.2% under RT pulsed operation, respectively.
Unique properties of a photonic-crystal surface-emitting laser are reported. Single-mode operation over a large area can be achieved due to the effect of zero-group velocity at a band-edge mode. This leads to high-power operation and on-demand beam control. Various beam patterns including doughnut, multiple doughnuts, and circular, are generated by the design of the lattice structure, show potential for application in various fields. Furthermore, the output power almost reaches 1W under pulsed condition.
We numerically observe chaos synchronization of two semiconductor lasers commonly driven by a chaotic semiconductor laser subject to optical feedback. We observe strongly correlated chaos synchronization between the two response lasers even when the correlation between the drive and response lasers is low. We show that the cross correlation between the two responses is larger than that between drive and responses over a wide parameter region.
The La0.5Sr0.5CoO3 was used as a cathode for the first time when the plasma display panel was used on the handheld personal computer. It has favorable sputtering resistance characteristic and stable discharge characteristic in gases. A cathode made from the La0.5Sr0.5CoO3 has unique electrical characteristic in early phase discharge voltage characteristics. The discharge voltage continues to decrease from the starting value. In this report, the discharge voltage shift of the La0.5Sr0.5CoO3 was investigated through an analysis of the DC plasma panel which was made as prototype. It is presumed that the discharge voltage shift is caused by the current density shift of the cathode surface, and that the current density shift is caused by the surface profile of the cathode particles. In order to find out this mechanism, the spherical form model was applied to the discharge voltage shift, and the calculated values and the measured values were compared. The calculated values correspond approximately to measured values. This spherical form model is considered of available for the discharge voltage shift.
In this paper, we propose a system identification method for hybrid systems switched by the absolute value of velocity or displacement. First, it is shown that the regression vector space of a mechanical system switched by the absolute value of velocity or displacement cannot be separated by a hyperplane. Then a method based on support vector machines with a polynomial kernel is proposed. The effectiveness is shown by simulations using a spring-mass-damper system.
In this paper, we consider the identification problem for a dual-rate system in which the input sampling period may differ from that of the output. Based on the lifting operators, a lifted system which is equivalent to the original dual-rate system can be derived so that a lifted state-space model can be obtained which maps the relations between the dual-rate input-output data. Then the Numerical Subspace State-Space IDentification (N4SID) algorithm is modified and used to identify the lifted state-space model for the first time in the literature, taking the causality constraints of the lifted system into account. Finally, numerical studies are included to show the excellent numerical performance of the proposed algorithm.
A method of class association rule mining from incomplete databases is proposed using Genetic Network Programming (GNP). GNP is one of the evolutionary optimization techniques, which uses the directed graph structure. An incomplete database includes missing data in some tuples, however, the proposed method can extract important rules using these tuples, and users can define the conditions of important rules flexibly. Generally, it is not easy for Aprior-like methods to extract important rules from incomplete database, so we have estimated the performances of the rule extraction and classification of the proposed method using incomplete data set. The results showed that the accuracy of classification of the proposed method is favorable even if some tuples include missing data.
Control of CO2 emissions which is the main factor of global warming is one of the most important problems in the 21st century about preservation of earth environment. Therefore, efficient supply and use of energy are indispensable. We have proposed distributed energy management systems (DEMSs), where we are to obtain optimal plans that minimize both of costs and of CO2 emissions through electrical and thermal energy trading. In this paper, we evaluate trading methods for the DEMSs by computational experiments.
Active contour model (SNAKES) is very used as one of the powerful technique in a contour extraction that utilizes principle of energy-minimizing. Performing extraction of lip contour with the lip image that has strong edges or noises on the lips and oral cavity is an important problem. This paper proposes a new energy model of SNAKES based on hue characteristics of lip images.