Alaa Al-Kadry

Two octaves mid-infrared supercontinuum generation in As 2 Se 3 microwires

We report the first demonstration of mid-infrared supercontinuum generation in As₂Se₃ chalcogenide microwires with the added advantage of using low energy pulses. The generated SC covers two octaves of bandwidth from 1.1 μm to 4.4 μm at -30 dB. This exceeds the broadest reported SC bandwidth in As₂Se₃ microwires by a factor of 3.5. The microwire geometry and pumping conditions are the key parameters in generating the 3.3 μm bandwidth while using a low pump pulse energy of 500 pJ.

Broadband supercontinuum generation in As2Se3 chalcogenide wires by avoiding the two-photon absorption effects

We report the generation of a broadband supercontinuum (SC) spanning from 1260 to 2200 nm using a 10 cm long As2Se3 chalcogenide (ChG) wire pumped at a wavelength of 1550 nm. Such a wide SC in As2Se3 is obtained by avoiding the effects of two-photon absorption normally observed at a wavelength of 1550 nm. For this purpose, the pump soliton is initially self-frequency shifted toward longer wavelength by means of the Raman effect in standard silica fiber before being launched into the ChG wire for spectral broadening.

Design, fabrication and characterization of PC, COP and PMMA-cladded As 2 Se 3 microwires

We introduce the PC- and COP-cladded As2Se3 microwires, two highly nonlinear microwires optimized to operate in the wavelength range of 1.85 µm to 2.20 µm. Like the previously reported PMMA-cladded As2Se3 microwire, the PC- and COP-cladded microwires benefit of a large waveguide nonlinear parameter and engineerable chromatic dispersion level, but without the absorption features of PMMA in the 1.85 μm to 2.20 μm range. The design rules and fabrication technique of each polymer-cladded microwire is provided. COP- and PMMA-cladded microwires with identical length and waveguide nonlinearity parameter are also operated in the nonlinear regime, highlighting features of self-phase modulation, four-wave mixing and Raman scattering in the 1.85 μm to 2.20 μm range.

Maximized Soliton Self-Frequency Shift in Non-Uniform Microwires by the Control of Third-Order Dispersion Perturbation

We present a simple method based on the soliton perturbative theory to design microwires of non-uniform diameter profiles. In contrast to previous methods, the one presented here relies on minimizing the soliton perturbation by third order dispersion (TOD) while taking into account the change of the soliton local duration along the microwire. The method leads to a design that maximizes the soliton self-frequency shift in non-uniform microwires. The microwire design comprises a unique dispersion profile such that a wavelength-shifting soliton experiences only weak perturbations from the TOD and avoids shedding its energy into the dispersive waves. The TOD perturbation is quantified with an analytic expression ε that is kept below a threshold value, thus keeping a soliton weakly perturbed by TOD in every position within the microwire. Numerical simulations are conducted to check the validity of the method. We consider a fundamental soliton centered at a wavelength of 2000 nm propagating in As2Se3 microwires of length as short as 10 cm. The results show that optimized non-uniform diameter profile allows the tuning of the self-frequency shifted soliton over a spectral range of 860 nm.

Mode-locked fiber laser based on chalcogenide microwires

We report the first mode-locked fiber laser using a chalcogenide microwire as the nonlinear medium. The laser is passively mode-locked with nonlinear polarization rotation and can be adjusted for the emission of solitons or noise-like pulses. The use of the microwire leads to a mode-locking threshold at the microwatt level and shortens the cavity length by 4 orders of magnitude with respect to other lasers of its kind. The controlled birefringence of the microwire, combined with a linear polarizer in the cavity, enables multiwavelength laser operation with tunable central wavelength, switchable wavelength separation, and a variable number of laser wavelengths.

Analysis of Self-Pulsating Sources Based on Cascaded Regeneration and Soliton Self-Frequency Shifting

We characterize the operation of self-pulsating sources made of two optical regenerators in cascade, namely a first regenerator of the type self-phase modulation spectral broadening and offset filtering, followed by a second regenerator of the type supercontinuum generation and offset filtering. The range of operation of this laser is explored as the wavelength and bandwidths of the band-pass filters are adjusted. We also provide experimental evidence that soliton self-frequency shift emanating from modulation instability triggers bursts of pulses at the repetition rate of the cavity. The stochastic nature of sources based on this concept leads to shot-to-shot pulse fluctuations in the cavity, which on average result in a flat supercontinuum extending beyond 1900 nm. Finally, a seed pulse can be sustained efficiently via this laser architecture, and the cavity consequently generates subpicosecond pulses at one of its output.

Low-energy-threshold mid-infrared supercontinuum generation in As2Se3 microwires

We report the first demonstration of mid-infrared supercontinuum generation in As2Se3 chalcogenide microwires with the added advantage of using low energy pulses. The generated supercontinuum covers two octaves bandwidth from 1.1um to 4.4um.

Broadband supercontinuum generation in all-normal dispersion chalcogenide microwires

We report the first chalcogenide microwire that is designed with all-normal dispersion to generate supercontinuum by optical-wave-breaking, a low-noise nonlinear process. The generated supercontinuum spectrum spans over an octave from 960 nm to 2500 nm using a microwire length of only 3 mm.

Comparison of 2.7 micron fluorescent spectra of Er-ZBLAN with 980 nm and 790 nm pumping

We investigate the fluorescence spectra of a ZBLAN fiber as a function of the laser pumping source wavelength, 790 nm and 980 nm, with an aim to optimize the fluorescence at 2.7 μm. A theoretical model based on the energy band diagrams of erbium has been built to support the results.

Operation of regenerative sources based on alternating SPM and SSFS

We report on the operation of regenerative sources based on self-phase modulation (SPM) and soliton self-frequency shift (SSFS). Such stochastic sources generate a wide continuum spreading over 450 nm.