M. Alsous - Academia.edu (original) (raw)
Papers by M. Alsous
Chaos, Solitons & Fractals, 2005
ABSTRACT We investigate the dynamics of a quasiperiodically rocked underdamped Josephson junction... more ABSTRACT We investigate the dynamics of a quasiperiodically rocked underdamped Josephson junction in an asymmetric “ratchet” potential, which is irradiated by a weak quasiperiodic field of two frequencies ω1 and ω2. The parameter dependence of the onset of chaos which manifests as irregular substructure in the form of “spiky” tails on the voltage-current characteristics of the junction is investigated. For damping parameter β = 20 and considerable amplitudes α1 = α2 = 0.051 with field frequencies ω1 = 1 and ω2 = 0.005, the calculations demonstrate that this complex substructure is observed at temperature T = 0 K, and dramatically retained in the presence of solely thermal “white” noise, contrary to what would otherwise round the irregular structure and smooth out the features.
Instruments and Experimental Techniques, 2015
ABSTRACT A heat pipe based thermal oven for crystals is presented. The crystal is placed in the a... more ABSTRACT A heat pipe based thermal oven for crystals is presented. The crystal is placed in the adiabatic region of the heat pipe in order to have a homogenized temperature around and inside the crystal. The system ensures a steady and homogeneous temperature environment within 0.1°C precision in a wide temperature range [20°C, 100°C].This oven is used to control the temperature of the second harmonic generated from a KD*P crystal. The experimental results and modeling predictions of the temperature effect are presented and compared.
Applied Physics B, 2015
ABSTRACT We propose and study the use of a single-shot, collinear, tilted-front cross-correlator ... more ABSTRACT We propose and study the use of a single-shot, collinear, tilted-front cross-correlator scheme for relative pulse timing measurements. In a very simple geometry, sub-0.5-fs resolution and larger than 3-ps instantaneous time window in relative pulse timing measurement are demonstrated. In addition, the scheme is shown to be practically immune to the changes of the energy of the monitored pulses exceeding 10 %. On the basis of the obtained results, the scheme can be expected to find applications in diagnostics and stabilization of timing jitter and drifts of pulses originating from different sources.
Micro-optical Technologies for Measurement, Sensors, and Microsystems II and Optical Fiber Sensor Technologies and Applications, 1997
Optics Communications, 2003
Here, we report a novel technique for selective generation of either of the two orthogonally pola... more Here, we report a novel technique for selective generation of either of the two orthogonally polarized beams from the same resonator cavity of an electrooptically Q-switched solid-state laser without introducing any additional optics. A theoretical analysis of the resonator set up along with realization of the technique has been demonstrated with similar output energy, pulse width, beam parameter product and
Optics Communications, 2003
We report intracavity second harmonic (at 532 nm) generation in a passively Q-switched mode-locke... more We report intracavity second harmonic (at 532 nm) generation in a passively Q-switched mode-locked Nd:YVO 4 laser. The width of a typical Q-switched envelope of the mode-locked pulses for the green laser was around 65 AE 5 ns and the repetition rate for the mode-locked pulses was 400 MHz. The intracavity frequency doubling significantly improves the depth of modulation of the mode-locked pulses. The peak power of a single mode-locked green pulse near the center of the Q-switched envelope was estimated to be more than 2 kW and the average green power was 6 times higher than the CW green power at an incident diode pump power of 6 W.
Optics & Laser Technology, 2005
Simultaneous Q-switching and mode-locking in a laser-diode end-pumped intracavity frequency doubl... more Simultaneous Q-switching and mode-locking in a laser-diode end-pumped intracavity frequency doubled Nd:YVO4=KTP green laser using Cr 4+ :YAG saturable absorber is experimentally demonstrated. The in uence of the initial transmission (T0) of the Cr 4+ :YAG crystal on the Q-switched mode-locked green pulses as well as on the average green power is characterized by using Cr 4+ :YAG crystal with various T0. The e ect of T0 on the pulse build-up time in intracavity second harmonic conÿguration is theoretically investigated. It was found that the depth of modulation for the mode-locked pulses is greatly improved at the second harmonic wavelength as compared to that for the fundamental wavelength. The average pulse duration of the individual mode-locked pulse for the second harmonic beam measured to be less than 500 ps with a repetition rate of 400 MHz. ?
Optics & Laser Technology, 2011
The optical limiting action of poly(dimethylacetylendicarboxylate) polymer doped with fullerene C... more The optical limiting action of poly(dimethylacetylendicarboxylate) polymer doped with fullerene C 60 has been investigated under irradiation with 10 ns laser pulses at 532 nm. The optical limiting measurements were performed at four different dopant concentrations. The threshold limiting fluence at 0.3 J/cm 2 was observed at high doping concentrations, with transmission of about 55%. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its nonlinear optical absorption behavior.
Pure and Applied Optics: Journal of the European Optical Society Part A, 1996
All-fibre 0963-9659/5/6/004/img2-doped lasers pumped longitudinally by a pigtailed laser diode ar... more All-fibre 0963-9659/5/6/004/img2-doped lasers pumped longitudinally by a pigtailed laser diode are constructed by depositing multidielectric mirrors directly at the ends of fibres and by gluing other fibres onto these mirrors. We use an ordinary and very practical splice gluing technique where the alignment is done with reference to the optical claddings. The steps concerning the design and manufacture of the filters, their incorporation into the fibres and the making of lasers are described in detail. The operation of the lasers is then noted. The ensuing observations allow the evaluation of the performance limits of the lasers made by this technique. We establish that the limiting factors do not result from the design or from the deposition of the filters, but from a systematic transverse shift of the fibres' cores during the filter gluing process. We establish which are the optimal characteristics of the fibres involved in the all-fibre laser construction to improve their performance despite the core shift.
Applied Physics B, 2004
Simultaneous Q-switching and mode locking in a laser-diode end-pumped intracavity frequency-doubl... more Simultaneous Q-switching and mode locking in a laser-diode end-pumped intracavity frequency-doubled Nd:YVO 4 /KTP green laser using a Cr 4+ :YAG saturable absorber with 81% initial transmission is experimentally demonstrated. At an incident pump power of 6 W, 300 mW of average green power was obtained, which is around four times higher than the cw green power obtained without the Cr 4+ :YAG crystal. The repetition rate of the mode-locked green pulses was 400 MHz and the individual mode-locked pulse width was measured to be 500 ps. The repetition rate of the Q-switched envelope of the mode-locked pulses was 15 kHz at 6 W of incident pump power. The energy of the mode-locked pulse at the peak of the Q-switched envelope was estimated to be 1 µJ and the peak power was estimated to be 2.4 kW. The measured width and the total energy of the Q-switched envelope of the mode-locked pulses was 47 ns and 21 µJ, respectively, at the maximum incident pump power. An analysis of the system by incorporating a nonlinear loss term due to the intracavity second-harmonic generation to the general recurrence relation for the mode-locked pulses under the Q-switched envelope at the fundamental wavelength has been presented. Using a hyperbolic secant square function to model the mode-locked pulse, the temporal shape of a single Q-switched pulse at the secondharmonic wavelength has been reconstructed. The theoretical calculations of the pulse parameters like pulse energy, peak power, pulse width and pulse-symmetry factor have shown fairly good agreement with the experimental results. PACS 42.55.Rz; 42.55.Xi; 42.60.By
We report on an examination of pulse timing stability of a home built Erbium Doped Fiber Laser (E... more We report on an examination of pulse timing stability of a home built Erbium Doped Fiber Laser (EDFL) passively mode locked via nonlinear polarization rotation by inserting semiconductor saturable absorber mirror (SESAM) in laser cavity. A very low root mean square (RMS) timing jitter (less than 27 fsec) and faster self-starting mode locking have been established. In order to get clear, low noise signal for time resolving measurements, synchronization of EDFL laser with an external high precision electronic oscil-lator have been established. Subsequently, it is synchronized and optically cross-correlated with a Ti: Sapphire laser source (Micra). The measured relative timing jitter was found to be less than 65 fsec. In this way, the two, well synchronized Ti:Sapphire and EDFL laser pulses prove to be a powerful tool for time resolving measurements.
Chaos, Solitons & Fractals, 2005
ABSTRACT We investigate the dynamics of a quasiperiodically rocked underdamped Josephson junction... more ABSTRACT We investigate the dynamics of a quasiperiodically rocked underdamped Josephson junction in an asymmetric “ratchet” potential, which is irradiated by a weak quasiperiodic field of two frequencies ω1 and ω2. The parameter dependence of the onset of chaos which manifests as irregular substructure in the form of “spiky” tails on the voltage-current characteristics of the junction is investigated. For damping parameter β = 20 and considerable amplitudes α1 = α2 = 0.051 with field frequencies ω1 = 1 and ω2 = 0.005, the calculations demonstrate that this complex substructure is observed at temperature T = 0 K, and dramatically retained in the presence of solely thermal “white” noise, contrary to what would otherwise round the irregular structure and smooth out the features.
Instruments and Experimental Techniques, 2015
ABSTRACT A heat pipe based thermal oven for crystals is presented. The crystal is placed in the a... more ABSTRACT A heat pipe based thermal oven for crystals is presented. The crystal is placed in the adiabatic region of the heat pipe in order to have a homogenized temperature around and inside the crystal. The system ensures a steady and homogeneous temperature environment within 0.1°C precision in a wide temperature range [20°C, 100°C].This oven is used to control the temperature of the second harmonic generated from a KD*P crystal. The experimental results and modeling predictions of the temperature effect are presented and compared.
Applied Physics B, 2015
ABSTRACT We propose and study the use of a single-shot, collinear, tilted-front cross-correlator ... more ABSTRACT We propose and study the use of a single-shot, collinear, tilted-front cross-correlator scheme for relative pulse timing measurements. In a very simple geometry, sub-0.5-fs resolution and larger than 3-ps instantaneous time window in relative pulse timing measurement are demonstrated. In addition, the scheme is shown to be practically immune to the changes of the energy of the monitored pulses exceeding 10 %. On the basis of the obtained results, the scheme can be expected to find applications in diagnostics and stabilization of timing jitter and drifts of pulses originating from different sources.
Micro-optical Technologies for Measurement, Sensors, and Microsystems II and Optical Fiber Sensor Technologies and Applications, 1997
Optics Communications, 2003
Here, we report a novel technique for selective generation of either of the two orthogonally pola... more Here, we report a novel technique for selective generation of either of the two orthogonally polarized beams from the same resonator cavity of an electrooptically Q-switched solid-state laser without introducing any additional optics. A theoretical analysis of the resonator set up along with realization of the technique has been demonstrated with similar output energy, pulse width, beam parameter product and
Optics Communications, 2003
We report intracavity second harmonic (at 532 nm) generation in a passively Q-switched mode-locke... more We report intracavity second harmonic (at 532 nm) generation in a passively Q-switched mode-locked Nd:YVO 4 laser. The width of a typical Q-switched envelope of the mode-locked pulses for the green laser was around 65 AE 5 ns and the repetition rate for the mode-locked pulses was 400 MHz. The intracavity frequency doubling significantly improves the depth of modulation of the mode-locked pulses. The peak power of a single mode-locked green pulse near the center of the Q-switched envelope was estimated to be more than 2 kW and the average green power was 6 times higher than the CW green power at an incident diode pump power of 6 W.
Optics & Laser Technology, 2005
Simultaneous Q-switching and mode-locking in a laser-diode end-pumped intracavity frequency doubl... more Simultaneous Q-switching and mode-locking in a laser-diode end-pumped intracavity frequency doubled Nd:YVO4=KTP green laser using Cr 4+ :YAG saturable absorber is experimentally demonstrated. The in uence of the initial transmission (T0) of the Cr 4+ :YAG crystal on the Q-switched mode-locked green pulses as well as on the average green power is characterized by using Cr 4+ :YAG crystal with various T0. The e ect of T0 on the pulse build-up time in intracavity second harmonic conÿguration is theoretically investigated. It was found that the depth of modulation for the mode-locked pulses is greatly improved at the second harmonic wavelength as compared to that for the fundamental wavelength. The average pulse duration of the individual mode-locked pulse for the second harmonic beam measured to be less than 500 ps with a repetition rate of 400 MHz. ?
Optics & Laser Technology, 2011
The optical limiting action of poly(dimethylacetylendicarboxylate) polymer doped with fullerene C... more The optical limiting action of poly(dimethylacetylendicarboxylate) polymer doped with fullerene C 60 has been investigated under irradiation with 10 ns laser pulses at 532 nm. The optical limiting measurements were performed at four different dopant concentrations. The threshold limiting fluence at 0.3 J/cm 2 was observed at high doping concentrations, with transmission of about 55%. An explanation based on the combination of two-photon absorption and reverse saturable absorption was proposed for its nonlinear optical absorption behavior.
Pure and Applied Optics: Journal of the European Optical Society Part A, 1996
All-fibre 0963-9659/5/6/004/img2-doped lasers pumped longitudinally by a pigtailed laser diode ar... more All-fibre 0963-9659/5/6/004/img2-doped lasers pumped longitudinally by a pigtailed laser diode are constructed by depositing multidielectric mirrors directly at the ends of fibres and by gluing other fibres onto these mirrors. We use an ordinary and very practical splice gluing technique where the alignment is done with reference to the optical claddings. The steps concerning the design and manufacture of the filters, their incorporation into the fibres and the making of lasers are described in detail. The operation of the lasers is then noted. The ensuing observations allow the evaluation of the performance limits of the lasers made by this technique. We establish that the limiting factors do not result from the design or from the deposition of the filters, but from a systematic transverse shift of the fibres' cores during the filter gluing process. We establish which are the optimal characteristics of the fibres involved in the all-fibre laser construction to improve their performance despite the core shift.
Applied Physics B, 2004
Simultaneous Q-switching and mode locking in a laser-diode end-pumped intracavity frequency-doubl... more Simultaneous Q-switching and mode locking in a laser-diode end-pumped intracavity frequency-doubled Nd:YVO 4 /KTP green laser using a Cr 4+ :YAG saturable absorber with 81% initial transmission is experimentally demonstrated. At an incident pump power of 6 W, 300 mW of average green power was obtained, which is around four times higher than the cw green power obtained without the Cr 4+ :YAG crystal. The repetition rate of the mode-locked green pulses was 400 MHz and the individual mode-locked pulse width was measured to be 500 ps. The repetition rate of the Q-switched envelope of the mode-locked pulses was 15 kHz at 6 W of incident pump power. The energy of the mode-locked pulse at the peak of the Q-switched envelope was estimated to be 1 µJ and the peak power was estimated to be 2.4 kW. The measured width and the total energy of the Q-switched envelope of the mode-locked pulses was 47 ns and 21 µJ, respectively, at the maximum incident pump power. An analysis of the system by incorporating a nonlinear loss term due to the intracavity second-harmonic generation to the general recurrence relation for the mode-locked pulses under the Q-switched envelope at the fundamental wavelength has been presented. Using a hyperbolic secant square function to model the mode-locked pulse, the temporal shape of a single Q-switched pulse at the secondharmonic wavelength has been reconstructed. The theoretical calculations of the pulse parameters like pulse energy, peak power, pulse width and pulse-symmetry factor have shown fairly good agreement with the experimental results. PACS 42.55.Rz; 42.55.Xi; 42.60.By
We report on an examination of pulse timing stability of a home built Erbium Doped Fiber Laser (E... more We report on an examination of pulse timing stability of a home built Erbium Doped Fiber Laser (EDFL) passively mode locked via nonlinear polarization rotation by inserting semiconductor saturable absorber mirror (SESAM) in laser cavity. A very low root mean square (RMS) timing jitter (less than 27 fsec) and faster self-starting mode locking have been established. In order to get clear, low noise signal for time resolving measurements, synchronization of EDFL laser with an external high precision electronic oscil-lator have been established. Subsequently, it is synchronized and optically cross-correlated with a Ti: Sapphire laser source (Micra). The measured relative timing jitter was found to be less than 65 fsec. In this way, the two, well synchronized Ti:Sapphire and EDFL laser pulses prove to be a powerful tool for time resolving measurements.