Generation Of Short Optical Pulses Research Articles

ABSORPTION OF OPTICAL PULSES UNDER PROPAGATION THROUGH ONE-DIMENSIONAL RESONANT FRACTAL CLUSTERS

Peculiarities of propagation of short optical pulses through resonantly absorbing fractal media are investigated in the work using methods of numerical simulation. The fractal object was modeled by a one-dimensional structure with its parameters being similar to generalized Cantor dust. The dependence of transmission of such a medium on its Hausdorff dimension in some cases was shown to have a nonmonotonous character. Interpretation of the results obtained is also given.

500 GHz optical short pulse generation from a monolithic passively mode-locked distributed Bragg reflector laser diode

A 500 GHz optical short pulse train was generated from a passively mode-locked distributed Bragg reflector laser diode (DBR-LD). The repetition frequency was thirteen times the fundamental round trip frequency in the LD, and harmonic mode-locking occurred. The pulse duration was 700 fs and the time-bandwidth product was 0.51, very close to the transform-limited value of a Gaussian waveform, 0.44. To our knowledge, this is the first report on the harmonic mode locking of a monolithic passively mode-locked laser diode.

Transform-limited optical short-pulse generation at high repetition rate over 40 GHz from a monolithic passive mode-locked DBR laser diode

The fabrication of monolithic InP-based passively mode-locked distributed-Bragg-reflector (DBR) laser is reported. An optical short-pulse train with a duration of 3.5 ps was generated at a repetition rate of over 40 GHz. The time-bandwidth product was 0.43, and it was very close to the transform-limited value of a Gaussian waveform. Peak power of 60 mW has been achieved. This laser is promising as an optical source for a high-bit-rate soliton transmission system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical short pulse generation by a DFB laser/EA modulator integrated light source

A simulation of optical short pulse generation using a DFB (distributed feedback) laser/EA (electroabsorption) modulator integrated light source was carried out. The dependence of the pulse shape and the spectrum on the isolation resistance between the laser and the modulator part is clarified. Theoretical results show that the spectrum is affected more seriously than the pulse shape by the isolation resistance. An isolation resistance of larger than 500 k Omega is required for transform-limited pulse generation. Utilizing an integrated light source with an isolation resistance of 10 M Omega , optical short pulse generation at a 5-GHz repetition rate was experimentally obtained with a pulsewidth of 33 ps and with a spectral bandwidth of 9.4 GHz.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optical short pulse generation and data modulation by a single-chip InGaAsP tandem-integrated electroabsorption modulator (TEAM)

A new integrated device consisting of two tandem-integrated InGaAsP electroabsorption modulators (TEAMs) was proposed and evaluated. It has been confirmed that the two important functions, pulse generation and data modulation, in soliton transmitters, can be realised simultaneously in this single-chip device.

Optical short pulse generation at high repetition rate over 80 GHz from a monolithic passively modelocked DBR laser diode

Optical short pulses at high repetition rate over 80 GHz were successfully generated using a monolithically fabricated passively modelocked distributed Bragg reflector laser diode for the first time. By using linear fibre compression, a transform-limited optical pulse train with a duration of 2.7 ps was obtained. The pulse envelope closley matched a sech2 waveform.

Generation of short pulses by stimulated Brillouin scattering in optical fibers

A new method for the generation of short optical pulses is demonstrated experimentally. The pulses are created from a phase-modulated cw signal that is propagated through an optical fiber under the influence of stimulated Brillouin scattering. It is possible to achieve repetition rates that are much larger than the Brillouin linewidth.

Wave group decomposition of ultrashort light pulses

We present a new method for analyzing the propagation of short optical pulses through a dispersive medium. The idea is to decompose the pulse Fourier spectrum into an infinite set of elementary wave groups, each propagating with its own group velocity. Such a method may be generalized to the case of nonlinear self-phase-modulation and points out the asymmetry observed in the white-light continua generated in the femtosecond regime.

Short optical pulse generated by integrated MQW DBR laser/EA-modulator fabricated by selective-area MOVPE

Summary form only given. The authors report on the generation of short optical pulses by utilizing the nonlinear absorption characteristics of a multiple quantum well (MQW) electroabsorption (EA) modulator, which is monolithically integrated with an MQW wavelength-tunable distributed Bragg reflector (DBR) laser on a single chip. Preliminary measurements show that optical pulses as short as 39 ps have been generated at a repetition rate of 3 GHz with a broad tuning range of 5.4 nm near 1554-nm lasing wavelength. The bandgap energies of both the narrow-gap active MQW region and the wide-gap passive MQW region are controlled by the oxide width and grown at the same time using selective-area epitaxy by metal-organic vapor-phase epitaxy (MOVPE). >

Optical short pulse generation by double gate operation of tandem connected electroabsorption modulators driven by sinusoidal voltages

A new method for generating optical short pulses using tandem connected electroabsorption modulators driven by sinusoidal voltages was proposed. Theoretical estimation shows that pulse trains with 2% duty cycle can be obtained. Pulse trains with 8% duty cycle at 5 GHz repetition rate were experimentally generated.

Erratum: Optical short pulse generation by double gate operation of tandem connected electroabsorption modulators driven by sinusoidal voltages

Erratum: Optical short pulse generation by double gate operation of tandem connected electroabsorption modulators driven by sinusoidal voltages

Ultra-short pulse generation for soliton transmission using electroabsorption modulators

Abstract A simple and stable technique of optical short pulse generation for soliton transmission based on external modulation is reviewe.By using nonlinearity of absorption characteristics of an electroabsorption modulator, ultra-short optical pulse trains having a shape close to sech2 shape can be generated just with sinusoidal modulation, without ultra-short driving pulses and ultra-broad bandwidth of the modulator. The pulse width and the repetition rate can be varied by changing the electrical driving conditions. Quasi-transform-limited optical pulseswith time-bandwidth product of 0.32 were successfully generated by the sinusoidally driven InGaAsP electroabsorption modulator with up to 20 GHz repetition rate. An application of a λ/4-shifted DFB laser-electroabsorption modulator integrated light source to a single-chip soliton source is also described. The high quality of the modulator-generator pulses has been proven by long-distance soliton transmission over 6400 km at 2.5 Gb/s using a recirculating...

Picosecond and sub-picosecond pulse generation in semiconductor lasers

Generation of short optical pulses in semiconductor lasers is of practical interest for an increasing number of applications. It is also of fundamental interest because of its tight relation with the field of semiconductor laser dynamics. After an introductory review, we compare the performances of gain-switching, Q-switching and mode-locking techniques. The comparison is illustrated by experimental results as well as by laser modelling, some of which are new. A special emphasis is given on the aspects of phase modulation in the semiconductor laser medium. Finally, we discuss some perspectives for further developments.

On the propagation of short optical pulses in a linear dispersive medium with absorption

A very accurate numerical algorithm based on the Laplace transform is used to describe the field evolution of ultrashort Gaussian-modulated pulses in a single resonance Lorentz medium. The results are compared with previously published numerical results by I. Christov (see ibid., vol.24, p.1548-53, 1988) in which a simple Taylor series expansion of the input pulse spectrum about the carrier frequency is used to explain the observed pulse dynamics. It is shown, by numerical Laplace transform analysis, that these previously published numerical results are inaccurate and that the first few terms of the Taylor series expansion technique about the carrier frequency do not properly explain the physically correct dispersive pulse evolution properties for rapid rise time pulses. In response to the comments the original author recalculated the dispersive propagation of femtosecond optical pulses by using different numerical methods. >

Monolithic colliding-pulse mode-locked quantum-well lasers

Integration of the whole mode-locked laser onto a single piece of semiconductor offers a number of advantages, including total elimination of optical alignment processes, improved mechanical stability, and the generation of short optical pulses at much higher repetition frequencies. Semiconductor laser processing technologies were used to implement the colliding-pulse mode-locking (CPM) scheme, which is known to effectively shorten the pulses and increase stability, on a miniature monolithic semiconductor cavity. The principles of and recent progress in monolithic CPM quantum-well lasers are reviewed. >

Ultra-Short Pulses for Optical Soliton Transmission. New Approach from External Modulation.

Mode-locking and gain-switching of semiconductor lasers have been reviewed from a view point of an optical short pulse generator for soliton transmission. A new approach from an external modulation using an electroabsorption modulator to generation of transform- limited optical short pulses is demon-strated. Transform-limited optical pulses up to 20 GHz repetition rates were generated just using a sinusoidal modulation of an InGaAsP electroabsorption modulator without any optical resonators and optical filters. The shape of the modulator-generated pulse is very closed to sech2 shape, and both the pulse width and the repetition rate can be easily varied by electrical signals. The promising future of the simple and stable optical pulse generation using the electroabsorption modulator was confirmed by 2.5 Gb/s-6400 km soliton data transmission using circulating loop experiments.

Ultralow chirping short optical pulse (16 ps) generation in gain-coupled distributed feedback semiconductor lasers

We describe optical short pulse generation in novel gain-coupled distributed feedback (GC-DFB) semiconductor lasers by using a simple electrically pumped gain switching method. An optical pulse as short as 16 ps has been obtained from a 130 ps current pulse. The most exciting result is that the lasers keep single longitudinal mode oscillation with very low wavelength chirping (∼0.12 nm) during the gain switching operation. From the optical pulse width and the amount of the wavelength chirping, we have estimated the α parameter of the GC-DFB laser to be less than 1.6.

Mode locking of laser diodes by picosecond optical pulse synchronous pumping

Short optical pulse generation from an external-cavity laser diode (LD) by optical pulse pumping has been investigated for the first time. An optical pulse train (pulse duration ∼40 ps) generated by a gain-switched LD was injected into a LD with an external cavity (slave LD) which was biased just below the laser threshold. The wavelength of the injected optical pulse was chosen to be slightly shorter than that of the slave LD. When the repetition rate of the optical injection pulse was nearly equal to the round trip time of the external cavity, the slave LD showed stable mode locking with the shorter pulse duration (∼22 ps) than that of the pumping pulse. At both the upper and lower repetition rates, the pulse duration of the slave LD also became shorter than that of the pumping pulse.

Interaction of short optical pulses with an inverted thin film consisting of two-level atoms

Numerical and analytic investigations are made of the reflection and propagation of short optical pulses through an inverted thin film consisting of two-level atoms. An analysis is made of cases where pulses having rectangular, hyperbolic-secant, and Gaussian profiles are incident normally on a thin film. It is shown that, as a result of the initial inversion of the atoms, induced superradiance occurs. The dependences of the parameters of the reflected and transmitted pulses on the characteristics of the incident pulse are determined.

Transform-limited 1.4 ps optical pulses from a monolithic colliding-pulse mode-locked quantum well laser

We report the generation of short optical pulses from novel monolithic colliding-pulse mode-locked quantum well lasers. Transform-limited pulses with durations of 1.4 ps at a repetition rate of 32.6 GHz have been achieved, with nearly 100% intensity modulation depth and a peak optical power of 10 mW. This is the shortest transform-limited pulse directly generated from monolithic mode-locked lasers (time-bandwidth product =0.3).