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We synthesize multicomponent oxide glasses for mid-infrared spectral range and we develop our own technology of nanostructured microoptical elements and nonlinear photonic crystal fibers. We investigate conditions of supercontinuum generation in our own fiber structures.

Oral presentations at Photonics West 2014, San Francisco

10-10-2013

Dr Mariusz Klimczak will deliver two talks on results of our work in supercontinuum generation in nonlinar photonic crystal fibers at Photonics West 2014 in San Francisco in February:

1: Broadband IR supercontinuum generation in hexagonal lattice tellurite photonic crystal fiber with dispersion optimized for pumping over 1500 nm

2: Influence of fiber laser pump conditions at 1550 nm on broadband infrared supercontinuum generation in all-solid all-normal dispersion photonic crystal fibers

Abstracts:

"Influence of fiber laser pump conditions at 1550 nm on broadband infrared supercontinuum generation in all-solid all-normal dispersion photonic crystal fibers"

Supercontinuum generation (SG) in photonic crystal fibers (PCFs) usually takes advantage of soliton dynamics, when pump wavelength is located in the anomalous dispersion region near the zero-dispersion wavelength of the fiber [1]. This results in broader bandwidth than pumping in the normal dispersion region (NDR). SG in NDR is of interest, because of its potential for high degree of coherence and low intensity fluctuations. It was experimentally demonstrated in silica fibers and PCFs pumped around 1000 nm, covering the visible and near-infrared [2,3].

We developed an all-solid PCF with hexagonal lattice made from N-F2 capillaries, with lattice constant Lambda=2.275µm, filling factor d/Lambda=0.9, and a solid N-F2 core with 2.5µm diameter. The capillaries were filled with thermally matched borosilicate glass rods with lower refractive index. The PCF has all-normal dispersion, flattened within 1400-2750 nm (-35 to -29 ps/nm/km) and a local maximum of -29 ps/nm/km at 1550 nm. Measured attenuation in 1500-1600 nm is around 3.2 dB/m. Nonlinear coefficient calculated at 1550 nm is 17/W/m. We numerically investigate the evolution of supercontinuum formation with a maximum bandwidth of 900-2400 nm. Considered pump pulse lengths were between 1 ps and 50 fs, with corresponding peak powers from 20kW to 200kW. Measured coupling efficiency using 20x microscope objective was 50%. One-photon-per-mode noise was used to simulate pump noise and multi-shot SG spectra were calculated. Preliminary experimental results are in good agreement with developed model.

 

"Broadband IR supercontinuum generation in hexagonal lattice tellurite photonic crystal fiber with dispersion optimized for pumping over 1500 nm"

Tellurite glass photonic crystal fibers (PCF) offer a large potential for broadband supercontinuum generation with bandwidths of 4000 nm demonstrated in suspended-core tellurite PCFs under pumping at 1500-1600 nm [1]. We fabricated a hexagonal-lattice, tellurite PCF with lattice constant Lambda = 2 µm, linear filling factor d/Lambda=0.75 µm, and a solid core with 2.7 µm diameter. Dispersion, calculated from SEM image of drawn fiber, has ZDW at 1500 nm and 4350 nm with a maximum of 193 ps/nm/km at 2900 nm. Under pumping with 150 fs / 36 nJ / 1580 nm pulses, supercontinuum in a bandwidth from 800 nm to over 2500 nm was measured in a 2 cm long PCF sample. Measured coupling efficiency was 8%. Dispersive and nonlinear length scales are 52 cm and 0.2 mm respectively, yielding nonlinearity-dominant propagation regime in the fiber. Numerical analysis of measured supercontinuum spectrum using NLSE, enabled identification of soliton fission and their subsequent red-shifting, dispersive wave generation across first ZDW, as well as FWM among the red-shifted spectral components. FWM phase-matching condition in the fiber is satisfied in a broad range from 1500 nm to 4000 nm with roughly 900 nm bandwidth around the signal wavelength. Developed model is in good agreement with experimental results. Model is used to estimate supercontinuum bandwidth for other experimental conditions with pump pulse lengths up to 1 ps and PCF lengths up to 10 cm.

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