Specialty Photonic Crystal Fibers and Their Applications

This year not only commemorates the 60th anniversary of nonlinear optics with the seminal experiment of second harmonic generation [...

Low-noise supercontinuum generation in chiral all-normal dispersion photonic crystal fibers

We present the advantages of supercontinuum generation in chiral, therefore circularly birefringent, all-normal dispersion fibers. Due to the absence of nonlinear power transfer between the polarization eigenstates of the fiber, chiral all-normal dispersion fibers do not exhibit any polarization instabilities and thus are an ideal platform for low-noise supercontinuum generation. By pumping a chiral all-normal dispersion fiber at 802 nm, we obtained an octave-spanning, robustly circularly polarized supercontinuum with low-noise.Comment: 4 pages, 5 figure

Tunable fiber source of entangled UV-C and infrared photons

Pairs of entangled photons -- biphotons -- are indispensable in quantum applications. However, some important spectral ranges, like ultraviolet, have been inaccessible to them so far. Here, we use four-wave mixing in a xenon-filled single-ring photonic crystal fiber to generate biphotons with one of the photons in the ultraviolet and its entangled partner in the infrared spectral range. We tune the biphotons in frequency by varying the gas pressure inside the fiber and thus tailoring the fiber dispersion landscape. The ultraviolet photons are tunable from 271 nm to 235 nm and their entangled partners, from 764 nm to 1342 nm, respectively. The tunability up to 170 THz is achieved by adjusting the gas pressure by only 0.57 bar. At 1.32 bar, the photons of a pair are separated by more than 2 octaves. The access to ultraviolet wavelengths opens the possibility for spectroscopy and sensing with undetected photons in this spectral range.Comment: 6 pages, 6 figure

Spatially resolved spectroscopy of alkali metal vapour diffusing inside hollow-core photonic crystal fibres

We present a new type of compact and all-glass based vapour cell integrating hollow-core photonic crystal fibres. The absence of metals, as in a traditional vacuum chamber and the much more compact geometry allows for fast and homogeneous heating. As a consequence we can fill the fibres on much faster timescales, ranging from minutes to hours. Additionally the all-glass design ensures optical access along the fibre. This allows live monitoring of the diffusion of rubidium atoms inside the hollow-core by measuring the frequency-dependent fluorescence from the atoms. The atomic density is numerically retrieved using a 5-level system of Bloch-equations.Comment: 9 pages, 5 figure

Raman-free, noble-gas-filled PCF source for ultrafast, very bright twin-beam squeezed vacuum

We report a novel source of twin beams based on modulational instability in high-pressure argon-filled hollow-core kagom\'e-style photonic-crystal fibre. The source is Raman-free and manifests strong photon-number correlations for femtosecond pulses of squeezed vacuum with a record brightness of ~2500 photons per mode. The ultra-broadband (~50 THz) twin beams are frequency tunable and contain one spatial and less than 5 frequency modes

Theory of photoionization-induced blueshift of ultrashort solitons in gas-filled hollow-core photonic crystal fibers

We show theoretically that the photoionization process in a hollow-core photonic crystal fiber filled with a Raman-inactive noble gas leads to a constant acceleration of solitons in the time domain with a continuous shift to higher frequencies, limited only by ionization loss. This phenomenon is opposite to the well-known Raman self-frequency redshift of solitons in solid-core glass fibers. We also predict the existence of unconventional long-range nonlocal soliton interactions leading to spectral and temporal soliton clustering. Furthermore, if the core is filled with a Raman-active molecular gas, spectral transformations between redshifted, blueshifted, and stabilized solitons can take place in the same fiber