A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pul...A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method. Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage. Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer. The experimental result shows that the proposed PWM dimmer has good performances.展开更多
Laser was coupled into an optical fiber,on which covered a layer of well-aligned carbon nanotubes(CNTs)serving as cathode,to tune the field emission of the cathode.CNT arrays as field emission cathode were synthesized...Laser was coupled into an optical fiber,on which covered a layer of well-aligned carbon nanotubes(CNTs)serving as cathode,to tune the field emission of the cathode.CNT arrays as field emission cathode were synthesized by chemical vapor deposition(CVD)on a naked fiber core.When the laser was coupled into the fiber,the turn-on voltage(Vto at a current density of 1 mA cm?2)decreased from 1.0 to 0.9 kV and the emission current density increased from 0.83 mA cm?2(at a 1 kV bias voltage)to3.04 mA cm?2 on 40μm diameter fiber.A photon absorption mechanism is attributed to the field emission improvement.The estimated effective work function of CNT arrays on the optical fiber decrease from 4.89 to 4.29 eV.The results show the possibility of constructing a waveguide type laser modulated field emission cathode.展开更多
An equivalent corrugation pitch-modulated （ECPM） distributed feedback （DFB） semiconductor laser with two equivalently assisted phase shifts （EAPS） was theoretically studied and experimentally demonstrated. The s...An equivalent corrugation pitch-modulated （ECPM） distributed feedback （DFB） semiconductor laser with two equivalently assisted phase shifts （EAPS） was theoretically studied and experimentally demonstrated. The simulated results showed that the longitudinal photon density distribution of the ECPM ＋ EAPS DFB lasers was much more uniform than that of a sole ECPM DFB laser without EAPS, and the longitudinal spatial hole burning was therefore suppressed more effectively. The results of experiment showed that good single longitudinal mode operation was achieved, with side mode suppression ratio （SMSR） being over 35 dB, and the wavelength range was from 1,559.64 to 1,563.02 nm when the operation current was from 50 to 160 mA at the temperature of 25 ℃, and the SMSR increased to 46.29 dB when the injection current was 130 mA.展开更多
Two measuring methods of the wide absorption spectrum by distributed feedback laser diodes （DFB-LDs） are presented in detecting the water vapor absorption line. One is the subsection scanning method, and it takes ad...Two measuring methods of the wide absorption spectrum by distributed feedback laser diodes （DFB-LDs） are presented in detecting the water vapor absorption line. One is the subsection scanning method, and it takes advantage of the wide spectrum tuning range by the temperature modulation and fast spectrum tuning speed by current modulation. Specifically, this method is realized by dividing a target spectral region into several sections which correspond to the specific temperature of DFB-LD, scanning every section by current modulation for hundreds times, and averaging the data to raise the signal to noise ratio （SNR）, then combining all sections to get the whole spectrum. An accuracy of 10ppmv had been obtained in the measurement of water vapor with a 10-cm path length by this method. Another is data fitting method, based on the absorption line-shape function; the absorption line can be described by fitting with partial measured data. The fitting absorption line was fitted well with the measured data, and the square of correlation coefficient （R-square） was no less than 0.99.展开更多
文摘A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method. Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage. Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer. The experimental result shows that the proposed PWM dimmer has good performances.
基金supported by the National Natural Science Foundation of China(Grant Nos.91123018,61172041,61172040,50975226,and 60801022)the National Hi-Tech Research and Development Program of China("863"Project)(Grant No.2008AA03A314)the Fundamental Research Funds for the Central Universities
文摘Laser was coupled into an optical fiber,on which covered a layer of well-aligned carbon nanotubes(CNTs)serving as cathode,to tune the field emission of the cathode.CNT arrays as field emission cathode were synthesized by chemical vapor deposition(CVD)on a naked fiber core.When the laser was coupled into the fiber,the turn-on voltage(Vto at a current density of 1 mA cm?2)decreased from 1.0 to 0.9 kV and the emission current density increased from 0.83 mA cm?2(at a 1 kV bias voltage)to3.04 mA cm?2 on 40μm diameter fiber.A photon absorption mechanism is attributed to the field emission improvement.The estimated effective work function of CNT arrays on the optical fiber decrease from 4.89 to 4.29 eV.The results show the possibility of constructing a waveguide type laser modulated field emission cathode.
基金supported by the National Natural Science Foundation of China(61306068 and 61435014)the Natural Science Foundation of Jiangsu Province of China(BK20130585 and BK20140414)+1 种基金the National High Technology Research and Development Program(SS2015AA012302)the Applied Basic Research Project of Suzhou City(SYG201309)
文摘An equivalent corrugation pitch-modulated （ECPM） distributed feedback （DFB） semiconductor laser with two equivalently assisted phase shifts （EAPS） was theoretically studied and experimentally demonstrated. The simulated results showed that the longitudinal photon density distribution of the ECPM ＋ EAPS DFB lasers was much more uniform than that of a sole ECPM DFB laser without EAPS, and the longitudinal spatial hole burning was therefore suppressed more effectively. The results of experiment showed that good single longitudinal mode operation was achieved, with side mode suppression ratio （SMSR） being over 35 dB, and the wavelength range was from 1,559.64 to 1,563.02 nm when the operation current was from 50 to 160 mA at the temperature of 25 ℃, and the SMSR increased to 46.29 dB when the injection current was 130 mA.
基金This work was supported by Natural Science Foundation of China （60977058 ＆ 61205083）, Independent Innovation Foundation of Shandong University （IIFSDU2010JC002 ＆ 2012JC015）, the key technology projects of Shandong Province （2010GGX10137）, and promotive research fund for excellent young and middle-aged scientists of Shandong Province （BS2010DX028）. Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author（s） and source are credited.
文摘Two measuring methods of the wide absorption spectrum by distributed feedback laser diodes （DFB-LDs） are presented in detecting the water vapor absorption line. One is the subsection scanning method, and it takes advantage of the wide spectrum tuning range by the temperature modulation and fast spectrum tuning speed by current modulation. Specifically, this method is realized by dividing a target spectral region into several sections which correspond to the specific temperature of DFB-LD, scanning every section by current modulation for hundreds times, and averaging the data to raise the signal to noise ratio （SNR）, then combining all sections to get the whole spectrum. An accuracy of 10ppmv had been obtained in the measurement of water vapor with a 10-cm path length by this method. Another is data fitting method, based on the absorption line-shape function; the absorption line can be described by fitting with partial measured data. The fitting absorption line was fitted well with the measured data, and the square of correlation coefficient （R-square） was no less than 0.99.
