Dissipative nonlinear structures in optical fiber systems I:dissipative dispersion managed solitons in mode-locked lasers

In this first talk on dissipative structures in fiber applications, we extend theory of dispersion-managed solitons to dissipative systems with a focus on mode-locked fibre lasers. Dissipative structures exist at high map strengths leading to the generation of stable, short pulses with high energy. Two types of intra-map pulse evolutions are observed depending on the net cavity dispersion. These are characterized by a reduced model and semi-analytical solutions are obtained.

Dissipative dispersion managed solitons in mode-locked fibre lasers

We extend theory of dispersion-managed solitons to dissipative systems with a focus on mode-locked fibre lasers. Dissipative structures exist at high map strengths, and different pulse evolutions are observed depending on the net cavity dispersion.

Mode-locked semiconductor lasers with optical injection

We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.

Optical communications applications of ultra-long Raman fiber lasers

Recent work on ultra-long Raman fiber lasers has shown that it is possible to create quasi-lossless transmission conditions in fiber spans long enough to be considered for high speed optical communications. This paper reviews how quasi-lossless transmission conditions are reached and presents experimental results of 40Gb/s transmission in a quasi lossless system. The performance is compared with a conventional EDFA based system.

Synchronized mode-locked erbium fibre lasers with intracavity dispersion control using chirped in-fibre Bragg gratings

We demonstrate a dual-wavelength fibre laser system using chirped fibre Bragg gratings as reflectors and dispersive elements. The system produces two synchronized trains of soliton pulses with rms jitter of 620 fs.

Quantum-dot mode-locked lasers with dual-mode optical injection

Quantum-dot mode-locked lasers are injection-locked by coherent two-tone master sources. Spectral tuning, significantly improved time-bandwidth product, and low jitter are demonstrated without deterioration of the pulse properties.

Dispersion-managed solitons in fibre systems and lasers

Nonlinear systems with periodic variations of nonlinearity and/or dispersion occur in a variety of physical problems and engineering applications. The mathematical concept of dispersion managed solitons already has made an impact on the development of fibre communications, optical signal processing and laser science. We overview here the field of the dispersion managed solitons starting from mathematical theories of Hamiltonian and dissipative systems and then discuss recent advances in practical implementation of this concept in fibre-optics and lasers.

Experimental demonstration of mode structure in ultralong Raman fiber lasers

We present the first experimental demonstration of a resolvable mode structure with spacing c/2nL in the RF spectra of ultralong Raman fiber lasers. The longest ever demonstrated laser cavity (L=84km), RF peaks of ∼100 Hz width and spacing ∼1 kHz have been observed at low intracavity powers. The width of the peaks increases linearly with growing intracavity power and is almost independent of fiber length. © 2007 Optical Society of America.

Noise and gain optimisation in bi-directionally pumped dispersion compensating amplifier modules

We perform optimisation of bi-directionally pumped dispersion compensating Raman amplifier modules. Optimal forward and backward pump powers for basic configurations using different commercially available fibers are presented for both single- and multi-channel systems. Optical signal-to-noise ratio improvement of up to 8 dB is achieved as a result of optimisation. © 2003 Published by Elsevier B.V.

Spectral modification of type IA fibre Bragg gratings by high-power near-infrared lasers

We report the first experimental measurements on the spectral modification of type IA fibre Bragg gratings, incorporated in an optical network, which result from the use of high-power, near-infrared lasers. The fibre grating properties are modified in a controlled manner by exploiting the characteristics of the inherent 1400 nm absorption band of the optical fibre, which grows in strength during the type IA grating inscription. If the fibre network is illuminated with a high-power laser, having an emission wavelength coincident with the absorption band, the type IA centre wavelength and chirp can be modified. Furthermore, partial grating erasure is demonstrated. This has serious implications when using type IA gratings in an optical network, as their spectrum can be modified using purely optical methods (no external heating source acts on the fibre), and to their long-term stability as the grating is shown to decay. Conversely, suitably stabilized gratings can be spectrally tailored, for tuning fibre lasers or edge filter modification in sensing applications, by purely optical means. © 2006 IOP Publishing Ltd.

Silica-clad neodymium-doped lanthanum phosphate fibers and fiber lasers

We have fabricated a neodymium-doped phosphate glass fiber with a silica cladding and used it to form a fiber laser. Phosphate and silicate glasses have considerably different glass transition temperatures and softening points making it hard to draw a fiber from these two glasses. A bulk phosphate glass of composition (Nd2O3)(0.011)(La2O3)(0.259)(P2O5)(0.725)(Al2O3)(0.005) was prepared and the resultant material was transparent, free from bubbles and visibly homogeneous. The bulk phosphate glass was drawn to a fiber while being jacketed with silica and the resultant structure was of good optical quality, free from air bubbles and major defects. The attenuation at a wavelength of 1.06 mu m was 0.05 dB/cm and the refractive index of the core and cladding at the pump wavelength of 488 nm was 1.56 and 1.46, respectively. The fibers were mechanically strong enough to allow for ease of handling and could be spliced to conventional silica fiber. The fibers were used to demonstrate lasing at the F-4(3/2) - I-4(11/2) (1.06 mu m) transition. Our work demonstrates the potential to form silica clad optical fibers with phosphate cores doped with very high levels of rare-earth ions (27-mol % rare-earth oxide).

Asymmetric reactions of organosilicon compounds and properties of novel optically active organosilanes

Partial reduction of racemic methoxysilanes by 1:1 complexes of lithium aluminium hydride with optically active cinchona and ephedra alkaloids give optically active silanes and methoxysilanes. Optical yields depend on the groups attached to silicon and the alkaloid used but in some cases approach 50%, The method has been used to prepare novel optically active organosilanes, possessing an asymmetric silicon centre, which are either inaccessible by any of the other available routes or would require a time consuming preparation. Such compounds are of use in the study of the mechanism of substitutions at silicon. Attempts have been made to rationalize the results of the asymmetric reductions in terms of differences in sterio and electronic interactions in diastereoisomeric transition states. Circular dichroism and optical rotatory dispersion spectra have been obtained for the optically active products in an attempt to elucidate the absolute configurations of the novel asymmetric organosilanes. The results from these studies provide a useful addition to the data so far accumulated for asymmetrically perturbed aromatic chromophores. Nuclear magnetic resonanoe studies of diastereoisomaric (-)-menthoxysilanes show that these compounds possess resonances extremely useful in the determination of optical purities for asymmetric organosilanes which possess an aromatic group. The effect of variable temperature on the spectra has revealed evidence for the conformational preferences in these compounds. Other diastereoisomeric alkoxysilanes have been prepared and their n.m.r.spectra studied in the hope of establishing trends. Exploratory studies for other asymmetric reactions proceeding at silicon have proved unfruitful.

Nonlinear pulse shaping and polarization dynamics in mode-locked fiber lasers

We review our recent progress on the study of new nonlinear mechanisms of pulse shaping in passively mode-locked fiber lasers. These include a mode-locking regime featuring pulses with a triangular distribution of the intensity, and spectral compression arising from nonlinear pulse propagation. We also report on our recent experimental studies unveiling new types of vector solitons with processing states of polarization for multi-pulse and tightly bound-state soliton (soliton molecule) operations in a carbon nanotube (CNT) mode-locked fiber laser with anomalous dispersion cavity. © 2014 World Scientific Publishing Company.

SHG in a low-loss orientation patterned GaAs waveguide

We demonstrate second harmonic generation at 1621 nm in a low-loss orientation-patterned GaAs waveguide pumped by an optical parametric oscillator system. The losses were estimated to be 2.12 dB/cm.