Dariusz Pysz

Coherent supercontinuum generation up to 2.3 µm in all-solid soft-glass photonic crystal fibers with flat all-normal dispersion

Supercontinuum spanning over an octave from 900 - 2300 nm is reported in an all-normal dispersion, soft glass photonic crystal fiber. The all-solid microstructured fiber was engineered to achieve a normal dispersion profile flattened to within -50 to -30 ps/nm/km in the wavelength range of 1100 - 2700 nm. Under pumping with 75 fs pulses centered at 1550 nm, the recorded spectral flatness is 7 dB in the 930 - 2170 nm range, and significantly less if cladding modes present in the uncoated photonic crystal fiber are removed. To the best of our knowledge, this is the first report of an octave-spanning, all-normal dispersion supercontinuum generation in a non-silica microstructured fiber, where the spectrum long-wavelength edge is red-shifted to as far as 2300 nm. This is also an important step in moving the concept of ultrafast coherent supercontinuum generation in all-normal dispersion fibers further towards the mid-infrared spectral region.

Low-loss propagation and continuously tunable birefringence in high-index photonic crystal fibers filled with nematic liquid crystals

Experimental investigations of microstructured fibers filled with liquid crystals (LCs) have so far been performed only by using host fibers made of the silica glass. In this paper, the host photonic crystal fiber (PCF) was made of the PBG08 high-refractive index glass (approximately 1.95) that is much higher than silica glass index (approximately 1.46) and also higher then both ordinary and extraordinary refractive indices of the majority of LCs. As a result, low-loss and index-guiding propagation is observed regardless of the LC molecules orientation. Attenuation of the host PCF was measured to be approximately 0.15 dB/cm and for the PCF infiltrated with 5CB LC was slightly higher (approximately 0.19 dB/cm), resulting in a significant reduction to approximately 0.04 dB/cm of the scattering losses caused by the LC. Moreover, an external transverse electric field applied to the effective photonic liquid crystal fiber (PLCF) allowed for continuous phase birefringence tuning from 0 to 2.10(-4).

Index Guiding Photonic Liquid Crystal Fibers for Practical Applications

Photonic liquid crystal fibers (PLCFs) can be categorized in two principal groups: index guiding PLCFs and photonic bandgap PLCFs. In this paper we focus on index guiding PLCFs in which effective refractive index of the micro structured cladding filled with liquid crystal is lower than refractive index of the fiber core. In these fibers broadband propagation of light is observed and also effective tuning of guiding properties is possible. In this paper PLCFs with tunable attenuation, retardation and polarization dependent losses are reported. We also enumerate some potential applications of index-guiding PLCFs, together with discussion of few technical issues important in the context of future development (i.e., effective electrical steering and connecting with standard fibers).

Broadband supercontinuum generation in normal dispersion all-solid photonic crystal fiber pumped near 1300 nm

We report on octave-spanning supercontinuum generation under pumping with 1360 nm, 120 fs pulses, in an all-solid, all-normal dispersion photonic crystal fiber. The fiber was drawn from thermally matched oxide soft glasses with a hexagonal lattice 35 µm in diameter, 2.5 µm solid core and pitch of Λ/d = 0.9. The fiber was designed for normal dispersion broadly flattened in the 1200–2800 nm range. Experimentally recorded supercontinuum spectrum covered a 900–1900 nm bandwidth and was reconstructed with good agreement using numerical modeling. To the best of our knowledge, this is the first report of an experimentally demonstrated octave-spanning supercontinuum bandwidth, reaching as far as 1900 nm in the all-normal dispersion regime.

Broadband infrared supercontinuum generation in hexagonal-lattice tellurite photonic crystal fiber with dispersion optimized for pumping near 1560 nm

We report on supercontinuum generation (SG) in a hexagonal lattice tellurite photonic crystal fiber (PCF). The fiber has a regular lattice with a lattice constant Λ = 2 μm, linear filling factor d/Λ = 0.75, and a solid core 2.7 μm in diameter. Dispersion, calculated from scanning electron microscope (SEM) image of drawn fiber, has zero dispersion wavelength (ZDW) at 1410 and 4236 nm with a maximum of 193 ps/nm/km at 2800 nm. Under pumping with 150 fs/36 nJ/1580 nm pulses, supercontinuum spectrum in a bandwidth from 800 nm to over 2500 nm was observed in a 2 cm long PCF sample, which is comparable to results reported for suspended core tellurite PCFs pumped at wavelengths over 1800 nm. Measured spectrum is analyzed numerically with good agreement, and observed spectral broadening is interpreted. To our best knowledge, tellurite glass, regular lattice PCFs for successful SG in this bandwidth have not been reported before.

Infrared supercontinuum generation in soft-glass photonic crystal fibers pumped at 1560 nm

In this work we present results on supercontinuum (SC) generation in a photonic crystal fiber (PCF) fabricated from lead-bismuth-gallium-oxide glass (PBG-08). Due to high refractive index, high nonlinearity and high transmittance, the PBG-08 glass-based fibers seem to be excellent media for broad supercontinuum generation in the infrared spectral region. In our experiment, a short-length piece of PCF (5-6 cm) is pumped by a femtosecond chirped pulse amplification (CPA) setup, which may be seeded by two different fiber-based oscillators. This compact and cost-effective system allows to generate SC spanning from 900 to 2400 nm. The paper describes in detail the fabrication process of the fiber, as well as the SC generation results.

Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: A promising fiber light source for nonlinear Raman microspectroscopy.

A highly birefringent silicate glass photonic-crystal fiber (PCF) is employed for polarization-controlled nonlinear-optical frequency conversion of femtosecond Cr: forsterite laser pulses with a central wavelength of 1.24 mum to the 530--720-nm wavelength range through soliton dispersion-wave emission. The fiber exhibits a modal birefringence of 1.2.10(-3) at the wavelength of 1.24 mum due to a strong form anisotropy of its core, allowing polarization switching of the central wavelength of its blue-shifted output by 75 nm. Polarization properties and the beam quality of the blue-shifted PCF output are shown to be ideally suited for polarization-sensitive nonlinear Raman microspectroscopy.

Dispersion management in soft glass all-solid photonic crystal fibres

The development of all-solid photonic crystal fibres for nonlinear optics is an alternative approach to air-glass solid core photonic crystal fibres. The use of soft glasses ensures a high refractive index contrast (> 0.1) and a high nonlinear coefficient of the fibres. We report on the dispersion management capabilities in all-solid photonic crystal fibres taking into account four thermally matched glasses which can be jointly processed using the stack-and-draw fibre technique. We present structures with over 450 nm broadband flat normal dispersion and ultra-flat near zero anomalous dispersion below 5 ps/nm/km over 300 nm dedicated to supercontinuum generation with 1540 nm laser sources. The development of an all-solid photonic crystal fibre made of F2 and NC21 glasses is presented. The fibre is used to demonstrate supercontinuum generation in the range of 730–870 nm (150 nm) with flatness below 5 dB.

Soft glasses for photonic crystal fibers and microstructured optical components

Abstract. Thermally stable tellurite, lead-bismuth-gallium oxides based boron-silicate and lead-silicate glasses dedicated for multiple thermal processing are presented. The glasses are successfully used for the development of photonic crystal fibers, nanostructured gradient index lenses, all-solid microstructured fibers as well as refractive or diffractive micro-optical elements with ultra-broadband transmission.

Linear and nonlinear properties of multicomponent glass photonic crystal fibers

Processes resulting in supercontinuum generation in multicomponent glass photonic crystal fibers are reviewed in this paper. Multicomponent glass photonic crystal fibers are shown to have a broad transmission range, extending up to 4.5 μm in selected cases. Pumping with a 1240-nm femtosecond pulse at very low sub-nJ energies resulted in soliton formation and dispersive wave generation in a multicomponent PCF sample having a double-core square-lattice structure. These processes were described using a phase-matching model derived from the simulated dispersive properties of the fiber. Third-harmonic generation was observed in the radiation modes of a different cobweb sample with the simultaneous formation of a soliton in the NIR.