Generation Of Transform-limited Pulses Research Articles

Ultrafast all-fibre laser mode-locked by polymer-free carbon nanotube film.

This work for the first time reports the results on study of a polymer-free carbon nanotube (CNT) films used as a saturable absorber in an all-fibre laser. It is demonstrated that free-standing single-walled CNT films fabricated by an aerosol method are able to ensure generation of transform-limited pulses in an Er all-fibre ring laser with duration of several picoseconds and high quality of mode locking. The optimal average output power levels are identified, amounting to 0.4-0.5 mW depending on the linear transmission of the studied samples (60% or 80%). Application of polymer-free CNT films solves problems related to degradation of conventional polymer matrices of CNT-based saturable absorbers and paves the way to longer-lasting and more reliable saturable absorbers compatible with all-fibre laser configurations.

Spectral and temporal breathing self-similar evolution in a fiber amplifier for low-noise transform-limited pulse generation

We demonstrate a simple scheme for high-power low-noise high-contrast ultrashort pulse generation. It is enabled by the spectral and temporal breathing self-similar pulse evolution with an optimized negative pre-chirp. Experiments and simulations indicate the enhanced tolerances of this scheme to the gain-shaping distortions and pump fluctuations. It can lead to ∼16% increase in the compressed pulse quality with more than a two times wider spectrum and ∼31% reduction in the root-mean-square (rms) relative intensity noise (RIN). Transform-limited pulses as short as 36 fs are generated with the rms RIN of 0.029% (1 kHz-5 MHz) from a 2 m Yb-fiber amplifier.

Transform-limited pulse generation in normal cavity dispersion erbium doped single-walled carbon nanotubes mode-locked fiber ring laser

We demonstrate an erbium doped fiber ring laser mode-locked with a carboxymetylcellulose high-optical quality film with dispersed single-walled carbon nanotubes (SWCNT). The laser with large normal net cavity dispersion generates near bandwidth-limited picosecond inverse modified soliton pulses at 1.56 µm.

Energy efficient method for two-photon population transfer with near-resonant chirped pulses

We investigate a method for complete population inversion in three level systems through pi-pulse bichromatic two-photon coherent excitation and study the dependence on the chirp of the laser pulses. We observe that the population inversion does not monotonously decrease with increasing the time-bandwidth product, and that the excitation depends on the sign of the chirp of the individual pulses. Our results evidence a strategy for coherent population transfer which is energetically superior to adiabatic methods and opens the door for real-world applications, since it alleviates the need for challenging generation of transform-limited pulses at arbitrary wavelengths.

Generation of Transform-Limited Pulses Employing An Actively Mode-Locked Semiconductor Laser With A Linearly Chirped External Cavity

In this letter, the authors propose a simple source based on mode-locked semiconductor lasers using linearly chirped fiber Bragg gratings external cavities. Using this technique, transform-limited pulses, compatible with 10-Gb/s applications, are generated. Effects of Bragg grating's parameters on the source performances are also experimentally investigated

Picojoule threshold, picosecond optical parametric generation in reverse proton-exchanged lithium niobate waveguides

We have demonstrated picosecond optical parametric generation in reverse proton-exchanged waveguides in periodically poled lithium niobate with thresholds as low as 200 pJ. Near-transform-limited near-infrared pulses were obtained from cascaded optical parametric generation. For a 1.8-ps (FWHM) pump pulse at 769.6 nm, a saturated internal photon-conversion efficiency of 33% was obtained with 1 nJ of pump energy. The signal-wavelength tuning range was from 1.15 μm to 2.3 μm with a pump wavelength between 770 nm and 789.5 nm. Numerical simulations well predicted the mechanism for the transform-limited pulse generation. These results enable optical parametric generation devices with low threshold and good temporal properties with a simple single-pass setup.

Femto-Second Transform Limited Pulse Generation with Higher Order Dispersion Effects for Dispersion-Shifted Optical Communication System

The paper deals with the influence of higher-order effects of dispersion on the femto-second transform limited pulse generation by compensating for linear chirp of self-phase modulation spectra in the dispersion-shifted fibers. It has been shown that the minimum propagation length with first-order dispersion term is 23 m, as reported earlier. If the higher-order dispersion effects are taken into consideration, this length is reduced to 11.5 m. With compensation of the first-order dispersion term, this length can be enhanced to 6.8161 × 103 km. This length can further be improved to 6.0343 × 109 km by compensation of first- and second-order dispersion terms together. The minimum pulse width and linewidth product without dispersion, with dispersion including higher-order dispersion effects, and with dispersion compensation, is found to be 0.44, 0.4418, and 0.4411, respectively.

Effect of optical filtering on pulses generated with a gain-switched DFB laser

Gain-switched laser diodes are widely used to generate short optical pulses, which find several applications in optical fiber measurements and high-speed optical communication systems. Temporal and spectral properties of the gain-switched pulses can be tailored by filtering their optical spectrum. Optical filtering leads to suppression of frequency chirp and generation of transform-limited pulses. We show that tuning of the center frequency of an optical bandpass filter can result in not only pulse compression, but also in the generation of a series of secondary oscillations after the primary pulse. The origin of these secondary oscillations is investigated both experimentally and analytically.

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.

Wavelength-tunable nearly transform-limited pulsegeneration by external injection-seeding of again-switched Fabry-Perot laser

The authors report the generation of wavelength-tunable, nearly transform-limited pulses by external CW injection seeding and fibre compression of a gain-switched Fabry-Perot semiconductor laser. Nearly transform-limited, ~ 6 ps pulses with a time-bandwidth product of ~ 0.6 have been obtained over a tuning range of ~ 10 nm.

Application of the coherent photon seeding technique to synchronously pumped and hybridly mode-locked dye lasers

The mode-locking performances of synchronously pumped and hybridly mode-locked dye lasers self-stabilized by coherent photon seeding (CPS) are investigated experimentally. The variation of the optimum values of the feedback parameters and the pulse quality of the stabilized laser with the cavity detuning is studied over a wide range of this parameter. The results presented for the case of pure synchronous pumping complement those previously reported for the generation of transform-limited pulses of variable length. The first experiment on the application of CPS to a conventional dual-jet hybridly mode-locked laser confirms the predictions of the numerical modelling.

Low repetition rate master source for opticalprocessing in ultrahigh-speed OTDM networks

A simple technique for the generation of transform-limited pulses with durations of a few picoseconds at low repetition rates is reported. This is demonstrated experimentally and 6 ps pulses are generated at 1 and 2 GHz. These pulse trains have very low duty cycles and background levels.

Tunable transform-limited pulse generation using self-injection locking of an FP laser

Wavelength-tunable, near transform-limited pulses have been generated using a Fabry-Perot laser diode coupled to a fiber loop containing a fiber Fabry-Perot resonator (FFPR) and a polarization controller. The ratio of transmitted to reflected light from the loop can be adjusted using the polarization controller. Single-mode operation of the gain-switched laser is achieved by self-injection locking, which is induced by light reflected from the fiber loop. The resulting output pulse has a time-bandwidth product of 0.4 and is tunable over about 15 nm by varying the tuning voltage of the FFPR.< <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>

Actively mode-locked Ti:sapphire laser producing transform-limited pulses of 150-fs duration

We report on the generation of transform-limited pulses of 150-fs duration from an actively mode-locked Ti:sapphire laser. The laser produced subpicosecond pulses over the range 780-860 nm, with a maximum average output power of 600 mW. The output spot was in the form of a near-TEM(00) spot and demonstrated longterm pulse stability.

Transform-limited pulse generation in the gigahertz region from a gain-switched distributed-feedback laser diode using spectral windowing

For the first time, to our knowledge, transform-limited and high-power picosecond pulses in the gigahertz region are successfully generated from a distributed-feedback laser diode using spectral manipulation with a narrow-band Fabry-Perot resonator and erbium fiber amplifiers. The pulses, which before the optical filtering have a width of 27 psec and a spectral width of 1.24 nm, are transformed to transform-limited pulses with a width of 17 psec and a spectral width of 0.21 nm. The peak power of the pulse at a 6-GHz repetition rate is amplified to greater than 90 mW with an erbium fiber amplifier.

Repetitively pulsed mode-locked Nd:phosphate glass laser oscillator-amplifier system

Performance of a repetitively pulsed mode-locked Nd:glass laser system employing athermal phosphate glass in the oscillator and amplifier stages is described. Improved passive mode-locking characteristics of the oscillator are achieved through use of a l00-microm thick intracavity etalon, enabling reliable generation of transform-limited pulses typically of 5-psec duration. The system produces 1054-nm pulses of high beam quality and ~25-mJ energy at a pulse repetition rate of ~0.2 Hz. Subsequent frequency-doubling steps give conversion efficiencies of ~50% and 25%, respectively.

Picosecond pulse generation by passive mode locking of diode lasers

We report the generation of pulses as short as 5 psec in duration by passive mode locking of a modified strip buried heterostructure GaAlAs diode in an extended resonator. We also describe the effects of intercavity bandwidth control for the generation of transform-limited pulses. E/T;8042.80.−f, 42.55.Px