Search

We investigate with a numerical model the confinement loss of the higher-order modes of hollow-core inhibited coupling tube lattice fibers as influenced by the power spectral distribution of transverse surface roughness in the glass tubes forming the fiber cladding.

We demonstrate strong and stable phase-locking between the pump and the quantum generated Stokes/anti-Stokes spectral-pair in a comb generated in the regime of a single spatio-temporal coherent mode transient stimulated Raman scattering in H2-filled HCPCF.

We report on hollow-core fibers displaying rms core roughness under the surface capillary waves thermodynamic limit and record loss in the short-wavelength range (50.0 dB/km at 290 nm, 9.7 dB/km at 369 nm, 5.0 dB/km at 480 nm, 0.9 dB/km at 558 nm, 1.8 dB/km at 719 nm)., 5 pages, 3 figures

International audience; Generation of sub-Doppler spectral lines in compact devices is very useful in bringing functionalities such as laser-frequency stabilization, slow light application or quantum sensing to a wider and friendlier use. An all-fiber Photonic MicroCell (PMC), which consists of a gas-filled hollow core photonic crystal fiber (HCPCF) hermetically spliced to a solid optical fiber [1], is one of the most promising of such devices because of its ultra-long interaction length. Thus far, the PMC assembly processes are either limited to a short range of HCPCF core diameter [2], or entails the use of glue [3], or exhibit high injection losses (~10dB) [4]. Here, we report on a 7-meter contaminant free and single-mode C2H2-PMC. The process consists of end-capping a 80µbar acetylene-filled HCPCF via heat-collapsing a fused borosilicate sleeve on the two HCPCF tips. The process requires no helium gas [2] nor glue [3], which are potential pollution sources, and keeps the physical integrity of the HCPCF intact. The used HCPCF exhibits a novel cladding lattice and operates in a robust single-mode fashion [5]. The fiber has a 30 µm core diameter, a 10dB/km transmission loss at 1540 nm. The resulted PMC has polished and mounted ends to FC/APC connectors for integration (Fig. 1(a)), exhibits a total insertion loss of ~2dB and a motion-resistant single-mode guidance (see reconstructed near field in Fig. 1 (b)). The PMC was then used to generate saturable absorption spectroscopy (SAS) measurement (Fig. 1 (b-c))). The observed saturable absorption peak reaches 25% contrast and 20MHz linewidth (FWHM) for ~190mW of pump power that is the highest observed contrast in a fully sealed PMC [6]. The evolution of the SA peak characteristics over pump power are represented in Fig. 1 (e), and shows for pump power of less than 100 mW a transit-time limited linewidth (19MHz), thus indicating no additional collisional dephasing that could be induced by contaminant during the assembly process. The linewidth was monitored over 3 months for 23 mW pump power with no significant variation (Fig.1(f)), demonstrating thus its hermeticity, and its suitability for long time and mobile applications. Fig. 1. (a) FC/APC patch-cord like final PMC. (b) Near field intensity profile at the output of polished PMC. (c) Normalized SAS measurement on P9 absorption line of acetylene (1530.371nm) in purple line, simulation of SAS signal for 31 µbar pressure in dashed line. (d) SA contrast zoomed in SA peak with numerical calculation in dashed line. (e) Experimental (dots) and calculated (line) SA transparency peak contrast and linewidth evolution with pump power. The dashed line correspond to the transit time limit. (f) Evolution of SA FWHM during 95 days for a pump power of 23mW.

The advent of photonic bandgap (PBG) guiding hollow- core photonic crystal fiber (HC-PCF) sparked the hope of guiding light with attenuation below the fundamental silica Rayleigh scattering limit (SRSL) of conventional step-index fibers. Unfortunately, the combination of the strong core-cladding optical-overlap, the surface roughness at the silica cladding struts and the presence of interface-modes limited the lowest reported transmission-loss to 1.2 dB/km at 1550 nm. This hope is recently revived by the introduction of hypocycloid core- contour (i.e. negative curvature) in inhibited-coupling (IC) guiding HC-PCF, and the reduction of their confinement loss to a level that makes them serious contenders for light transmission below the SRSL in UV- VIS-NIR spectral range. Here, we report on several IC guiding HC-PCFs with a hypocycloid core-contour and a cladding structure made of a single ring from a tubular lattice. The fibers guide in the UV-VIS and NIR, and among which we list one with a record transmission loss of 7.7 dB/km at ~750 nm (only a factor ~2 above the SRSL), and a second with an ultra-broad fundamental-band with loss in the range of 10-20 dB/km spanning from 600 to 1200 nm. Both fibers present near-single mode guidance and very low bend loss sensitivity. The results show that the limit in the transmission is set by confinement loss for wavelengths longer than ~1 {\mu}m and by surface- roughness for shorter wavelengths, thus indicating that transmission loss well below the SRSL in the visible is possible with a surface roughness reduction and would open the possibility of the first UV low-loss light- guidance.

Recently we demonstrated a system for light-trapping molecules and stimulated Raman scattering based on a lattice of ultra-deep traps created by spatially modulated Raman saturation, where Raman-active molecules are strongly localized in a one-dimensional array of nanometre-wide sections, resulting in a central line with a sub-recoil linewidth as low as 14 kHz. Here the theoretical modelling of such a process is presented in detail. The numerical formalism is presented on both microscopic and macroscopic scale. The field distribution in the fiber is discussed, and the predictions regarding the line narrowing, sidebands, and lattice motion are provided

Optica 3(8), 816 - 822(2016). doi:10.1364/OPTICA.3.000816, Over the last decade, the development of ultrafast laser pulses in the mid-infrared (MIR) region has led to important breakthroughs in attosecond science and strong-field physics. However, as most such broadband MIR laser sources are near-IR pumped, the generation of high-intensity, long-wavelength MIR pulses is still a challenge, especially starting from picosecond pulses. Here we report, both experimentally and numerically, nonlinear pulse compression of sub-millijoule picosecond pulses down to sub-300 fs at 2050 nm wavelength in gas-filled Kagome-type hollow-core photonic crystal fibers for driving MIR optical parametric amplifiers. The pump laser is comprised of a compact fiber laser-seeded 2 μm chirped pulse amplification system based on a Ho:YLF crystal at 1 kHz repetition rate. Spectral broadening is studied for different experimental conditions with variations of gas pressure and incident pulse energies. The spectrally broadened 1.8 ps pulses with a Fourier-limited duration of 250 fs are compressed using an external prism-based compressor down to 285 fs and output energy of 125 μJ., Published by OSA, Washington, DC

International audience; We show a practical implementation of a pulse characterization method for sub-cycle pulse measurements in the infrared spectral range based on spectral shearing interferometry. We employ spatially-encoded arrangement filter-based spectral phase interferometry for direct electric field reconstruction with external ancila pulses (X-SEA-F-SPIDER). We show merits and limitations of the setup and an in-depth comparison to another widely used temporal characterization technique-Second-Harmonic Generation Frequency Resolved Optical Gating (SHG-FROG). The X-SEA-F-SPIDER implementation presented in this paper allows measurement of sub-cycle pulses with over one octave wide spectrum spanning the 900-2400 nm range without adding any extra dispersion due to the pulse characterization apparatus.

International audience

International audience

International audience; We report a comparative study on dephasing mechanisms between inner core coated and uncoated sections of the same Kagome hypocycloid-shaped core hollow core photonic crystal fibers (HC-PCF) filled with rubidium vapor. The comparison is performed by measuring the atomic polarization relaxation and electromagnetically induced transparency (EIT) linewidth in Rb loaded polydimethylsiloxane (PDMS) inner wall coated and bare silica core Kagome HC-PCF. The measurements show a polarization relaxation time of 32 mu s in a PDMS coated Kagome HC-PCF and 24 mu s in uncoated Kagome HC-PCF. A minimum EIT linewidth of 6.2 +/- 0.8MHz is achieved in PDMS coated Kagome HC-PCF, and 8.3 +/- 0.9 MHz for the uncoated Kagome HC-PCF.

International audience

International audience

National audience