The Experts below are selected from a list of 16536 Experts worldwide ranked by ideXlab platform
Y. Ogawa - One of the best experts on this subject based on the ideXlab platform.
-
480-GHz subharmonic Synchronous Mode locking in a short-cavity colliding-pulse Mode-locked laser diode
IEEE Photonics Technology Letters, 2002Co-Authors: S. Arahira, Y. OgawaAbstract:Stabilization of a short cavity (174 /spl mu/m) colliding-pulse Mode-locked laser diode was successfully demonstrated by subharmonic Synchronous Mode locking with a subharmonic frequency optical pulse injection. A stable 480-GHz optical pulse train synchronized to an external clock signal with a low timing jitter of 0.14 ps was generated.
-
Subharmonic Synchronous Mode-locking of a monolithic semiconductor laser operating at millimeter-wave frequencies
IEEE Journal of Selected Topics in Quantum Electronics, 1997Co-Authors: Ampalavanapillai Nirmalathas, H.f. Liu, Z. Ahmed, Dalma Novak, Y. OgawaAbstract:Optical pulse trains at millimeter-wave frequencies are generated by subharmonic Synchronous Mode-locking of a monolithic distributed Bragg reflector semiconductor laser, by which an initially passively Mode-locked semiconductor laser is stabilized by injecting optical pulses at subharmonic frequencies of its resonant frequency. The stabilized pulse trains are characterized in terms of phase noise, timing jitter, locking range and modulation depth under various injection conditions including injected signal power levels, pulsewidths, and subharmonic numbers. It is also shown that subharmonic Synchronous Mode-locking can provide pulse trains with a very low level of phase noise (/spl les/-86 dBc/Hz @ 10 kHz offset), reasonably wide locking ranges (4-20 MHz) and low levels of amplitude modulation (96%-99%). Such pulse characteristics are compared with those achieved by the subharmonic hybrid Mode-locking scheme, where stabilization is realized by injecting electrical signals at subharmonic frequencies of the laser's resonant frequency. It is shown that subharmonic hybrid Mode-locking is only effective at low subharmonic numbers (2-6), while subharmonic Synchronous Mode-locking can be realized with much larger subharmonic numbers. It is also revealed from the comparison that while subharmonic hybrid Mode-locking scheme is simple and cost-effective approach for the generation of high-frequency signals from semiconductor lasers, subharmonic Synchronous Mode-locking scheme can offer pulse trains using very low-frequency driving electronics with superior performance such as larger locking ranges, and lower levels of phase noise and amplitude modulation.
-
Synchronous Mode-locking in passively Mode-locked semiconductor laser diodes using optical short pulses repeated at subharmonics of the cavity round-trip frequency
IEEE Photonics Technology Letters, 1996Co-Authors: S. Arahira, Y. OgawaAbstract:Synchronous Mode-locking was achieved in passively Mode-locked semiconductor lasers using optical pulses with repetition rates at subharmonics of the cavity round-trip frequency. Stable and continuous Mode-locked pulses at 8.5 GHz were generated when the repetition rate of the control optical pulses was 4.25 GHz (2nd subharmonic). The timing jitter of the Mode-locked pulses was reduced to 1 ps. The relationship between repetition rates of the control pulses and the realization of stable and continuous Mode-locking was examined.
-
Extreme reduction of timing jitter in a subharmonic Synchronous Mode-locked laser diode
Conference Digest. ISLC 1998 NARA. 1998 IEEE 16th International Semiconductor Laser Conference (Cat. No. 98CH361130), 1Co-Authors: S. Arahira, S. Kutsuzawa, Y. OgawaAbstract:Extreme timing jitter reduction less than the master laser pulse's jitter was achieved in a subharmonic Synchronous Mode-locked laser diode. This was found to be originated from short term stability between neighboring pulses in passive Mode-locking operation.
-
Comparison of subharmonic Synchronous Mode-locking with subharmonic hybrid Mode-locking of a monolithic DBR laser operating at millimeter wave frequencies
International Topical Meeting on Microwave Photonics. MWP '96 Technical Digest. Satellite Workshop (Cat. No.96TH8153), 1Co-Authors: Ampalavanapillai Nirmalathas, Z. Ahmed, Dalma Novak, H.f. Liu, Y. OgawaAbstract:A detailed comparison of subharmonic Synchronous Mode-locking and subharmonic hybrid Mode-locking of a monolithic DBR laser is presented. While subharmonic electrical injection offers ease of implementation, subharmonic optical injection offers advantages of reduced amplitude modulation and larger locking ranges.
Eric Watelain - One of the best experts on this subject based on the ideXlab platform.
-
Effects of Synchronous versus aSynchronous Mode of propulsion on wheelchair basketball sprinting.
Disability and Rehabilitation: Assistive Technology, 2013Co-Authors: Arnaud Faupin, Benoit Borel, Christophe Meyer, Philippe Gorce, Eric WatelainAbstract:This study aimed to first investigate Synchronous (SYN) versus aSynchronous (ASY) Mode of propulsion and, second, investigate the wheel camber effects on sprinting performance as well as temporal parameters. Seven wheelchair basketball players performed four maximal eight-second sprints on a wheelchair ergometer. They repeated the test according to two Modes of propulsion (SYN and ASY) and two wheel cambers (9° and 15°). The mean maximal velocity and push power output was greater in the Synchronous Mode compared to the aSynchronous Mode for both camber angles. However, the fluctuation in the velocity profile is inferior for ASY versus SYN Mode for both camber angles. Greater push time/cycle time (Pt/Ct) and arm frequency (AF) for Synchronous Mode versus aSynchronous Mode and inversely, lesser Ct and rest time (Rt) values for the Synchronous Mode, for which greater velocity were observed. SYN Mode leads to better performance than ASY Mode in terms of maximal propulsion velocity. However, ASY propulsion allows greater continuity of the hand-rim force application, reducing fluctuations in the velocity profile. The camber angle had no effect on ASY and SYN mean maximal velocity and push power output. The study of wheelchair propulsion strategies is important for better understanding physiological and biomechanical impacts of wheelchair propulsion for individuals with disabilities. From a kinematical point of view, this study highlights Synchronous Mode of propulsion to be more efficient, with regards to mean maximal velocity reaching during maximal sprinting exercises. Even if this study focuses on well-trained wheelchair athletes, results from this study could complement the knowledge on the physiological and biomechanical adaptations to wheelchair propulsion and therefore, might be interesting for wheelchair modifications for purposes of rehabilitation.
-
Effects of Synchronous versus aSynchronous Mode of propulsion on wheelchair basketball sprinting
Disability and Rehabilitation: Assistive Technology, 2013Co-Authors: Arnaud Faupin, Benoit Borel, Christophe Meyer, Philippe Gorce, Eric WatelainAbstract:AbstractPurpose: This study aimed to first investigate Synchronous (SYN) versus aSynchronous (ASY) Mode of propulsion and, second, investigate the wheel camber effects on sprinting performance as well as temporal parameters. Method: Seven wheelchair basketball players performed four maximal eight-second sprints on a wheelchair ergometer. They repeated the test according to two Modes of propulsion (SYN and ASY) and two wheel cambers (9° and 15°).Results: The mean maximal velocity and push power output was greater in the Synchronous Mode compared to the aSynchronous Mode for both camber angles. However, the fluctuation in the velocity profile is inferior for ASY versus SYN Mode for both camber angles. Greater push time/cycle time (Pt/Ct) and arm frequency (AF) for Synchronous Mode versus aSynchronous Mode and inversely, lesser Ct and rest time (Rt) values for the Synchronous Mode, for which greater velocity were observed. Conclusions: SYN Mode leads to better performance than ASY Mode in terms of maximal pr...
Ampalavanapillai Nirmalathas - One of the best experts on this subject based on the ideXlab platform.
-
Novel technique for reduction of amplitude modulation of pulse trains generated by subharmonic Synchronous Mode-locked laser
IEEE Photonics Technology Letters, 2002Co-Authors: Manik Attygalle, Ampalavanapillai Nirmalathas, H.f. LiuAbstract:Subharmonically Synchronous Mode-locked and hybrid Mode-locked lasers suffer from strong amplitude modulation at frequencies corresponding to injection signal frequency. In this paper, we demonstrate for the first time, significant reduction of amplitude modulation of pulse trains generated by a subharmonic Synchronous Mode-locked laser at 38 GHz using a nonlinear optical loop mirror. Experimental results as well as a theoretical analysis for the scheme are presented.
-
Subharmonic Mode-Locking of Semiconductor Lasers Operating at Millimetre-Wave Frequencies
Springer Series in Photonics, 1999Co-Authors: H.f. Liu, Ampalavanapillai Nirmalathas, Dalma Novak, Yoh OgawaAbstract:Optical pulse trains at millimetre-wave frequencies are generated by subharmonic hybrid and subharmonic Synchronous Mode-locking of monolithic semiconductor lasers. Pulse trains are characterised in terms of timing jitter/phase noise, amplitude modulation, and locking ranges. It is shown that subharmonic hybrid Mode-locking is a simple and cost-effective approach while subharmonic Synchronous Mode-locking can provide pulses with superior performance.
-
Injection signal wavelength dependence of a subharmonically Synchronous Mode-locked monolithic semiconductor laser
1998 Conference on Optoelectronic and Microelectronic Materials and Devices. Proceedings (Cat. No.98EX140), 1998Co-Authors: Manik Attygalle, Ampalavanapillai Nirmalathas, D. NovakAbstract:Subharmonic Synchronous Mode-locking (SSML) has been shown to be a very attractive scheme for achieving high repetition rate optical pulses at mm-wave frequencies, and beyond. In this paper, we report the dependence of the injected signal wavelength on the performance of SSML lasers around its lasing wavelengths. In particular, the effect of coherent interaction will be addressed.
-
Subharmonic Synchronous Mode-locking of a monolithic semiconductor laser operating at millimeter-wave frequencies
IEEE Journal of Selected Topics in Quantum Electronics, 1997Co-Authors: Ampalavanapillai Nirmalathas, H.f. Liu, Z. Ahmed, Dalma Novak, Y. OgawaAbstract:Optical pulse trains at millimeter-wave frequencies are generated by subharmonic Synchronous Mode-locking of a monolithic distributed Bragg reflector semiconductor laser, by which an initially passively Mode-locked semiconductor laser is stabilized by injecting optical pulses at subharmonic frequencies of its resonant frequency. The stabilized pulse trains are characterized in terms of phase noise, timing jitter, locking range and modulation depth under various injection conditions including injected signal power levels, pulsewidths, and subharmonic numbers. It is also shown that subharmonic Synchronous Mode-locking can provide pulse trains with a very low level of phase noise (/spl les/-86 dBc/Hz @ 10 kHz offset), reasonably wide locking ranges (4-20 MHz) and low levels of amplitude modulation (96%-99%). Such pulse characteristics are compared with those achieved by the subharmonic hybrid Mode-locking scheme, where stabilization is realized by injecting electrical signals at subharmonic frequencies of the laser's resonant frequency. It is shown that subharmonic hybrid Mode-locking is only effective at low subharmonic numbers (2-6), while subharmonic Synchronous Mode-locking can be realized with much larger subharmonic numbers. It is also revealed from the comparison that while subharmonic hybrid Mode-locking scheme is simple and cost-effective approach for the generation of high-frequency signals from semiconductor lasers, subharmonic Synchronous Mode-locking scheme can offer pulse trains using very low-frequency driving electronics with superior performance such as larger locking ranges, and lower levels of phase noise and amplitude modulation.
-
Subharmonic Synchronous Mode-locking of a monolithic DBR semiconductor laser
Conference Digest. 15th IEEE International Semiconductor Laser Conference, 1Co-Authors: Ampalavanapillai Nirmalathas, H.f. Liu, Z. Ahmed, M.d. Pelusi, Dalma NovakAbstract:We report on Synchronous Mode-locking of a 33 GHz monolithic DBR semiconductor laser using an input optical pulse train with a repetition rate equal to the 20th subharmonic frequency, namely 1.65 GHz. The resulting 33 GHz optical pulse train exhibits very low timing jitter (< 0.21 ps).
Arnaud Faupin - One of the best experts on this subject based on the ideXlab platform.
-
Effects of Synchronous versus aSynchronous Mode of propulsion on wheelchair basketball sprinting.
Disability and Rehabilitation: Assistive Technology, 2013Co-Authors: Arnaud Faupin, Benoit Borel, Christophe Meyer, Philippe Gorce, Eric WatelainAbstract:This study aimed to first investigate Synchronous (SYN) versus aSynchronous (ASY) Mode of propulsion and, second, investigate the wheel camber effects on sprinting performance as well as temporal parameters. Seven wheelchair basketball players performed four maximal eight-second sprints on a wheelchair ergometer. They repeated the test according to two Modes of propulsion (SYN and ASY) and two wheel cambers (9° and 15°). The mean maximal velocity and push power output was greater in the Synchronous Mode compared to the aSynchronous Mode for both camber angles. However, the fluctuation in the velocity profile is inferior for ASY versus SYN Mode for both camber angles. Greater push time/cycle time (Pt/Ct) and arm frequency (AF) for Synchronous Mode versus aSynchronous Mode and inversely, lesser Ct and rest time (Rt) values for the Synchronous Mode, for which greater velocity were observed. SYN Mode leads to better performance than ASY Mode in terms of maximal propulsion velocity. However, ASY propulsion allows greater continuity of the hand-rim force application, reducing fluctuations in the velocity profile. The camber angle had no effect on ASY and SYN mean maximal velocity and push power output. The study of wheelchair propulsion strategies is important for better understanding physiological and biomechanical impacts of wheelchair propulsion for individuals with disabilities. From a kinematical point of view, this study highlights Synchronous Mode of propulsion to be more efficient, with regards to mean maximal velocity reaching during maximal sprinting exercises. Even if this study focuses on well-trained wheelchair athletes, results from this study could complement the knowledge on the physiological and biomechanical adaptations to wheelchair propulsion and therefore, might be interesting for wheelchair modifications for purposes of rehabilitation.
-
Effects of Synchronous versus aSynchronous Mode of propulsion on wheelchair basketball sprinting
Disability and Rehabilitation: Assistive Technology, 2013Co-Authors: Arnaud Faupin, Benoit Borel, Christophe Meyer, Philippe Gorce, Eric WatelainAbstract:AbstractPurpose: This study aimed to first investigate Synchronous (SYN) versus aSynchronous (ASY) Mode of propulsion and, second, investigate the wheel camber effects on sprinting performance as well as temporal parameters. Method: Seven wheelchair basketball players performed four maximal eight-second sprints on a wheelchair ergometer. They repeated the test according to two Modes of propulsion (SYN and ASY) and two wheel cambers (9° and 15°).Results: The mean maximal velocity and push power output was greater in the Synchronous Mode compared to the aSynchronous Mode for both camber angles. However, the fluctuation in the velocity profile is inferior for ASY versus SYN Mode for both camber angles. Greater push time/cycle time (Pt/Ct) and arm frequency (AF) for Synchronous Mode versus aSynchronous Mode and inversely, lesser Ct and rest time (Rt) values for the Synchronous Mode, for which greater velocity were observed. Conclusions: SYN Mode leads to better performance than ASY Mode in terms of maximal pr...
Essam M. Rashad - One of the best experts on this subject based on the ideXlab platform.
-
Theory and steady-state analysis of series-connected wound-rotor induction motor in sub-Synchronous Mode
2016 IEEE International Conference on Power and Energy (PECon), 2016Co-Authors: Essam M. RashadAbstract:The wound-rotor induction machine is capable of electromechanical energy conversion, if the stator and rotor windings are connected in series with a proper phase sequence. As a motor, the operation can be in one of two Modes. In the first Mode, the motor runs at exactly twice the Synchronous speed for stable loading conditions. In the second Mode, the motor runs at a speed below the Synchronous speed (sub-Synchronous) with self-starting capability in a manner similar to that of the normal operation Mode as an induction motor. In this paper, the operation of the motor in the sub-Synchronous Mode is analyzed using the physical relationships between the stator and rotor mmfs. The analysis includes the calculation of losses and efficiency. The obtained laboratory experimental results proved the validity of the proposed analysis.
-
Effect of parameters on sub-Synchronous operation of series-connected wound-rotor induction motor
2016 IEEE International Conference on Power and Energy (PECon), 2016Co-Authors: Essam M. RashadAbstract:In the sub-Synchronous Mode, series-connected wound-rotor induction motor can run at a speed below the Synchronous speed with self-starting capability in a manner similar to that of the normal Mode of operation of an induction motor. Under proper conditions, operation in the series-connected Mode can achieve better characteristics compared with normal induction motor by short-circuiting rotor circuit. Based on a developed mathematical, this paper investigates the effect of machine parameters on steady-state characteristics of series-connected wound-rotor induction motor sub-Synchronous Mode. A special attention is given to stator and rotor winding resistances along with stator-to-rotor effective turns ratio. The obtained results represent a helpful guide for designing wound rotor induction motor for operation in series-connected sub-Synchronous Mode.
-
Stability of variable speed series-connected wound rotor induction motor in super-Synchronous Mode
2010 IEEE International Conference on Power and Energy, 2010Co-Authors: Essam M. RashadAbstract:This paper investigates the stability issues associated with operating series-connected induction motor in super-Synchronous Mode. In such a Mode, the motor runs exactly at double the Synchronous speed in stable range irrespective of load conditions. In addition to special arrangements required to attain such a high speed, instability problems have been practically noted. The given analysis in this paper is based on the validity of a previously presented dynamic Model of an inverter fed motor drive system. Effects of supply frequency and motor parameters are studied to investigate instability reasons and suggest solutions, either in operation or in the design.
