Foued Amrani

Generation of surface-wave microwave microplasmas in hollow-core photonic crystal fiber based on a split-ring resonator.

We report on a new and highly compact scheme for the generation and sustainment of microwave-driven plasmas inside the core of an inhibited coupling Kagome hollow-core photonic crystal fiber. The microwave plasma generator consists of a split-ring resonator that efficiently couples the microwave field into the gas-filled fiber. This coupling induces the concomitant generation of a microwave surface wave at the fiber core surround and a stable plasma column confined in the fiber core. The scheme allowed the generation of several centimeters long argon microplasma columns with a very low excitation power threshold. This result represents an important step toward highly compact plasma lasers or plasma-based photonic components.

Multiple-Pulse Operation and Bound States of Solitons in Passive Mode-Locked Fiber Lasers

We present results of our research on a multiple-pulse operation of passive mode-locked fiber lasers. The research has been performed on basis of numerical simulation. Multihysteresis dependence of both an intracavity energy and peak intensities of intracavity ultrashort pulses on pump power is found. It is shown that the change of a number of ultrashort pulses in a laser cavity can be realized by hard as well as soft regimes of an excitation and an annihilation of new solitons. Bound steady states of interacting solitons are studied for various mechanisms of nonlinear losses shaping ultrashort pulses. Possibility of coding of information on basis of soliton trains with various bonds between neighboring pulses is discussed. The role of dispersive wave emitted by solitons because of lumped intracavity elements in a formation of powerful soliton wings is analyzed. It is found that such powerful wings result in large bounding energies of interacting solitons in steady states. Various problems of a soliton interaction in passive mode-locked fiber lasers are discussed.

Soliton complexes in a high power fiber laser

Ordered and disordered pattern formation of solitons is experimentally investigated in the passively mode-locked doubleclad erbium-doped fiber laser. Soliton complexes of about 500 pulses are obtained which organize in different patterns analogous the states of the matter. We have identified a soliton gas, a supersonic soliton gas flow, a soliton liquid, a soliton polycrystal and a crystal of solitons.

2-µm wavelength-range low-loss inhibited-coupling hollow core-PCF

We report on the design and fabrication of inhibited-coupling guiding hollow-core photonic crystal fiber with a transmission band optimized for low loss guidance around 2 μm. Two fibers design based on a Kagome-lattice cladding have been studied to demonstrate a minimum loss figure of 25 dB/km at 2 μm associated to an ultra-broad transmission band spanning from the visible to our detection limit of 3.4 μm. Such fibers could be an excellent tool to deliver and compress ultra-short pulse laser systems, especially for the emerging 2-3 μm spectral region.

Deep-UV plasma emission in hollow-core photonic crystal fiber

In this paper, after reviewing results in the emerging plasma photonics field, we report on a strong plasma emission in the Deep-UV (DUV) range using gas mixture for development of a tunable and miniaturized UV radiation source using microwave-driven plasma-core photonic crystal fiber. Several spectral lines in DUV were produced by Ar-N2-O2 plasmas and tailored by simply varying the gas ratio of this gas mixture. In addition, a planar technology was used to develop a special ring excitator for compact solution to sustain efficiently such plasmas with microwave power as low as the Watt-level.

Deep-UV plasma emission in hollow-core photonic crystal fiber using gas mixture

Atomic or molecular plasmas are an excellent media to produce a fluorescence light source emitting in the UV spectral range, which is of interest for many applications in biological, physical, chemical and other fields such as water decontamination, spectrophotometry, and photolithography. In parallel, the emergent hollow-core photonic crystal fiber (HC-PCF) technology has demonstrated its ability in micro-confining light and gases together [1]. Recently, this confinement has been extended to ionized gas with an Argon plasma that has been successfully generated inside the core of an inhibited-coupling (IC) HC-PCF with no damage to the fiber structural integrity [2]. This result opened an original platform ideal to realize very compact photonic components for DUV/UV laser systems. In this context, we report here on a broad DUV/UV emission using microwave-driven plasma-core PCF for development of such a tunable and miniaturized UV radiation source. By using a ternary gas mixture of argon, oxygen and nitrogen (Ar/O2/N2) with an adjustable gas ratio, we generated a stable micro-plasma column in IC Kagome HC-PCF over few cm length and demonstrated the emission of several fluorescence and guided lines in the 200–450 nm wavelength range. The optimum ratio of ternary gas mixture components for strongest emission in the DUV domain has been identified through systematic spectroscopic measurement campaign in HC-PCF. Figure 1 shows the transmitted spectra obtained at the output of a 19-cell core defect Kagomé HC-PCF (corresponding to 117 μm-core diameter) for various gas mixture ratios at a fixed microwave power of 35 W and a gas pressure of few mbar. Gradually, as we introduce the N2 and the O2 components (Fig. 1 (b) to (e)) to the Ar, several new lines appear due to the interaction of each molecule in the plasma ignition gas medium. From 275 nm up to 400 nm, one can observe the classical band emission of Nitrogen molecule from the Second Positive System. Then, the emission from 200 to 275 nm is assigned to the band emission of the ΝΟγ system. From these results, the ternary gas mixture ratio of 90%–5%–5% is found the optimum to demonstrate the broadest emission in the DUV/UV. A simulation study was also performed in such a gas mixture, using a 0D-global model, to determine the influence of the electron density on the radiation emission [3]. In Fig. 2 the theoretical evolution of the different spectral lines intensity of the Ar-O2-N2 plasma for both gas mixtures are plotted. The result shows a good agreement with experimental ones.

Control of soliton pattern through continuous external injection

The effect of an external continuous wave (cw) on the operating regime of a passively mode-locked double-clad fiber laser, operating in the anomalous dispersion regime, is experimentally investigated. Starting from different soliton distributions, we demonstrate that, under specific conditions, the cw signal forces the principal laser to operate in harmonic mode-locking regime.

Manipulation of large soliton ensembles in Er-doped double-clad fiber laser

We have studied the influence of an external continuous wave on a passively mode-locked fiber laser operating in the soliton regime. Starting from an irregular soliton distribution it is shown that harmonic mode-locking is obtained.

High power continuous wave and pulsed single mode Er:Yb doped double-clad fiber laser

We report two studies, the first allows the generation of a high power laser operating in continuous wave, and the second generates pulses with high average power. Unlike methods using large mode area fibers, we propose a 10 W double-clad Er:Yb doped fiber amplifier pumped at 980 nm with several laser diodes and spliced to pieces of standard single-mode fibers. In continuous wave laser the output power of about 8 W for 40 W pumping power is obtained. The experimental configuration giving a soliton crystal is based on the nonlinear polarization rotation. The soliton crystal is a particular regime; it is characterized by hundreds of pulses homogeneously distributed in unique condensate structure.

Soliton pattern formation in figure-of-eight laser

We investigate the soliton pattern formation in an erbium-doped figure-of-eight double-clad fiber laser. The mode-locking is realized with a nonlinear amplifying loop mirror. Different soliton complexes have been obtained similar to those obtained when the mode-locking is achieved through the nonlinear polarization rotation technique.