The Experts below are selected from a list of 54 Experts worldwide ranked by ideXlab platform
Shuji Nakamura - One of the best experts on this subject based on the ideXlab platform.
-
Longitudinal mode spectra and ultrashort pulse geneRation of InGaN multiquantum well structure laser diodes
Applied Physics Letters, 1997Co-Authors: Shuji Nakamura, Masayuki Senoh, Shin-ichi Nagahama, Naruhito Iwasa, Takao Yamada, Toshio Matsushita, Yasunobu Sugimoto, Hiroyuki KiyokuAbstract:Longitudinal modes with a mode sepaRation of 0.04 nm were observed on InGaN multiquantum well structure laser diodes (LDs). Other peaks different from the longitudinal modes, appeared with increasing Current above the threshold Current. Lasing was observed up to a pulsed Current Duty Ratio of 40%. The operating voltage of the LDs at the threshold was around 11 V. Ultrashort pulsed light from the LDs with a pulse width of 50 ps, an output power of 300 mW, and a peak wavelength of 404.2 nm was obtained. The damping constant and the frequency of the relaxation oscillation were 0.8 ns and 3 GHz, respectively.
-
InGaN quantum-well structure blue LEDs and LDs
Journal of Luminescence, 1997Co-Authors: Shuji NakamuraAbstract:Abstract High-power InGaN single-quantum-well structure (SQW) blue/green light-emitting diodes (LEDs) and violet multiquantum-well (MQW) structure laser diodes (LDs) were fabricated. The LDs emitted coherent light at 390–440 nm from an InGaN-based MQW structure at room temperature. Lasing was observed up to a pulsed Current Duty Ratio of 40%. The operating voltage of the LDs at the threshold was around 11 V. The emission of the SQW LEDs is due to a recombination of excitons localized at certain potential minima in InGaN quantum well.
M. Rahman - One of the best experts on this subject based on the ideXlab platform.
-
A study on the grinding of glass using electrolytic in-process dressing
Journal of Electronic Materials, 2002Co-Authors: A. Senthil Kumar, H. S. Lim, M. Rahman, K. FathimaAbstract:Grinding of brittle materials such as glass is gaining importance due to the rapid developments in the areas of machining of storage devices, microlenses, and optical communication devices. Grinding of such glasses is difficult because grinding wheels wear out easily due to the hard and brittle nature of the materials being machined. Grinding wheels with fine abrasive size are required in order to achieve ductile mode grinding. Problems such as wheel loading and glazing can be encountered while grinding with fine abrasive wheels. Electrolytic in-process dressing (ELID) is an efficient method to dress the grinding wheel while performing grinding. In this paper, a fundamental study on the mechanism of the ELID grinding technique is discussed in detail. Several sets of experiments have been performed to determine the optimal grinding conditions. From the experiments, it has been established that surface roughness could be further improved if the Current Duty Ratio to dress the grinding wheel were increased. The force patterns and the changes in the profile of the grinding wheel during machining are also presented and discussed in detail.
-
a fundamental study on the mechanism of electrolytic in process dressing elid grinding
International Journal of Machine Tools & Manufacture, 2002Co-Authors: H. S. Lim, K. Fathima, Senthil A Kumar, M. RahmanAbstract:Demands for high quality surface finish, dimensional and form accuracy are required for optical surfaces and it is very difficult to achieve these using conventional grinding methods. Electrolytic in-process dressing (ELID) grinding is one new and efficient method that uses a metal-bonded diamond grinding wheel in order to achieve a mirror surface finish especially on hard and brittle materials. However, studies reported so for have not explained the fundamental mechanism of ELID grinding and so it has been studied here by conducting experiments to establish optimal grinding parameters to obtain better surface finish under various in-process dressing conditions. In this research the results show that the cutting forces are unstable throughout the grinding process due to the breakage of an insulating layer formed on the surface of the grinding wheel; however, a smoother surface can be obtained using a high dressing Current Duty Ratio at the cost of high tool wear. ELID grinding is efficient for feed rates of less than 400 mm/min, and surface cracks are observed when it exceeds this limit.
Hiroyuki Kiyoku - One of the best experts on this subject based on the ideXlab platform.
-
Longitudinal mode spectra and ultrashort pulse geneRation of InGaN multiquantum well structure laser diodes
Applied Physics Letters, 1997Co-Authors: Shuji Nakamura, Masayuki Senoh, Shin-ichi Nagahama, Naruhito Iwasa, Takao Yamada, Toshio Matsushita, Yasunobu Sugimoto, Hiroyuki KiyokuAbstract:Longitudinal modes with a mode sepaRation of 0.04 nm were observed on InGaN multiquantum well structure laser diodes (LDs). Other peaks different from the longitudinal modes, appeared with increasing Current above the threshold Current. Lasing was observed up to a pulsed Current Duty Ratio of 40%. The operating voltage of the LDs at the threshold was around 11 V. Ultrashort pulsed light from the LDs with a pulse width of 50 ps, an output power of 300 mW, and a peak wavelength of 404.2 nm was obtained. The damping constant and the frequency of the relaxation oscillation were 0.8 ns and 3 GHz, respectively.
H. S. Lim - One of the best experts on this subject based on the ideXlab platform.
-
A study on the grinding of glass using electrolytic in-process dressing
Journal of Electronic Materials, 2002Co-Authors: A. Senthil Kumar, H. S. Lim, M. Rahman, K. FathimaAbstract:Grinding of brittle materials such as glass is gaining importance due to the rapid developments in the areas of machining of storage devices, microlenses, and optical communication devices. Grinding of such glasses is difficult because grinding wheels wear out easily due to the hard and brittle nature of the materials being machined. Grinding wheels with fine abrasive size are required in order to achieve ductile mode grinding. Problems such as wheel loading and glazing can be encountered while grinding with fine abrasive wheels. Electrolytic in-process dressing (ELID) is an efficient method to dress the grinding wheel while performing grinding. In this paper, a fundamental study on the mechanism of the ELID grinding technique is discussed in detail. Several sets of experiments have been performed to determine the optimal grinding conditions. From the experiments, it has been established that surface roughness could be further improved if the Current Duty Ratio to dress the grinding wheel were increased. The force patterns and the changes in the profile of the grinding wheel during machining are also presented and discussed in detail.
-
a fundamental study on the mechanism of electrolytic in process dressing elid grinding
International Journal of Machine Tools & Manufacture, 2002Co-Authors: H. S. Lim, K. Fathima, Senthil A Kumar, M. RahmanAbstract:Demands for high quality surface finish, dimensional and form accuracy are required for optical surfaces and it is very difficult to achieve these using conventional grinding methods. Electrolytic in-process dressing (ELID) grinding is one new and efficient method that uses a metal-bonded diamond grinding wheel in order to achieve a mirror surface finish especially on hard and brittle materials. However, studies reported so for have not explained the fundamental mechanism of ELID grinding and so it has been studied here by conducting experiments to establish optimal grinding parameters to obtain better surface finish under various in-process dressing conditions. In this research the results show that the cutting forces are unstable throughout the grinding process due to the breakage of an insulating layer formed on the surface of the grinding wheel; however, a smoother surface can be obtained using a high dressing Current Duty Ratio at the cost of high tool wear. ELID grinding is efficient for feed rates of less than 400 mm/min, and surface cracks are observed when it exceeds this limit.
K. Fathima - One of the best experts on this subject based on the ideXlab platform.
-
A study on the grinding of glass using electrolytic in-process dressing
Journal of Electronic Materials, 2002Co-Authors: A. Senthil Kumar, H. S. Lim, M. Rahman, K. FathimaAbstract:Grinding of brittle materials such as glass is gaining importance due to the rapid developments in the areas of machining of storage devices, microlenses, and optical communication devices. Grinding of such glasses is difficult because grinding wheels wear out easily due to the hard and brittle nature of the materials being machined. Grinding wheels with fine abrasive size are required in order to achieve ductile mode grinding. Problems such as wheel loading and glazing can be encountered while grinding with fine abrasive wheels. Electrolytic in-process dressing (ELID) is an efficient method to dress the grinding wheel while performing grinding. In this paper, a fundamental study on the mechanism of the ELID grinding technique is discussed in detail. Several sets of experiments have been performed to determine the optimal grinding conditions. From the experiments, it has been established that surface roughness could be further improved if the Current Duty Ratio to dress the grinding wheel were increased. The force patterns and the changes in the profile of the grinding wheel during machining are also presented and discussed in detail.
-
a fundamental study on the mechanism of electrolytic in process dressing elid grinding
International Journal of Machine Tools & Manufacture, 2002Co-Authors: H. S. Lim, K. Fathima, Senthil A Kumar, M. RahmanAbstract:Demands for high quality surface finish, dimensional and form accuracy are required for optical surfaces and it is very difficult to achieve these using conventional grinding methods. Electrolytic in-process dressing (ELID) grinding is one new and efficient method that uses a metal-bonded diamond grinding wheel in order to achieve a mirror surface finish especially on hard and brittle materials. However, studies reported so for have not explained the fundamental mechanism of ELID grinding and so it has been studied here by conducting experiments to establish optimal grinding parameters to obtain better surface finish under various in-process dressing conditions. In this research the results show that the cutting forces are unstable throughout the grinding process due to the breakage of an insulating layer formed on the surface of the grinding wheel; however, a smoother surface can be obtained using a high dressing Current Duty Ratio at the cost of high tool wear. ELID grinding is efficient for feed rates of less than 400 mm/min, and surface cracks are observed when it exceeds this limit.
