Fiber Bragg gratings in hole-assisted multicore fiber for space division multiplexing.

In this Letter we present, for the first time to our knowledge, the results of fiber Bragg grating (FBG) inscription in a novel microstructured multicore fiber characterized by seven single-mode isolated cores. A clear Bragg reflection peak can be observed in all of the 7 cores after one inscription process with a KrF nanosecond laser in a Talbot interferometer set up. We furthermore perform a numerical analysis of the effective refractive indices of the particular modes and compare it with the FBG inscription results. An experimental analysis of the strain and temperature sensitivities of all of the Bragg peaks is also included.

100 kW peak power picosecond thulium-doped fiber amplifier system seeded by a gain-switched diode laser at 2 µm.

We report on the generation of picosecond pulses at 2 µm directly from a gain-switched discrete-mode diode laser and their amplification in a multistage thulium-doped fiber amplifier chain. The system is capable of operating at repetition rates in the range of 2 MHz-1.5 GHz without change of configuration, delivering high-quality 33 ps pulses with up to 3.5 µJ energy and 100 kW peak power, as well as up to 18 W of average power. These results represent a major technological advance and a 1 order of magnitude increase in peak power and pulse energy compared to existing picosecond sources at 2 µm.

A miniature temperature high germanium doped PCF interferometer sensor.

We report in this paper a high thermal sensitivity (78 pm/°C) modal interferometer using a very short Photonic Crystal Fiber stub with a shaped Germanium doped core. The Photonic Crystal Fiber is spliced between two standard fibers. The splice regions allow the excitation of the core and cladding modes in the PCF and perform an interferometric interaction of such modes. The device is proposed for sensitive temperature measurements in transmission, as well as in reflection operation mode with the same high temperature sensitivity.

Nanofiber Fabry-Perot microresonator for nonlinear optics and cavity quantum electrodynamics.

We experimentally realize a Fabry-Perot-type optical microresonator near the cesium D2 line wavelength based on a tapered optical fiber, equipped with two fiber Bragg gratings that enclose a subwavelength diameter waist. Owing to the very low taper losses, the finesse of the resonator reaches F=86 while the on-resonance transmission is T=11%. The characteristics of our resonator fulfill the requirements of nonlinear optics and cavity quantum electrodynamics in the strong coupling regime. These characteristics, combined with the demonstrated ease of use and advantageous mode geometry, open a realm of applications.

Generation of flattop pump pulses for OPCPA by coherent pulse stacking with fiber Bragg gratings.

We present a simple and robust pulse shaping device based on coherent pulse stacking. The device is embedded in a polarisation maintaining step index fiber. An input pulse is sent through a fiber optical circulator. Up to four pulse replicas are reflected by fiber Bragg gratings and interfere at the output. Temperature control allows tuning of the relative pulse phases of the sub-pulses. Additionally fine tuning of the sub-pulse amplitudes is demonstrated. We experimentally generated 235 ps and 416 ps long flattop pulses with rising and falling edges shorter than 100 ps. In contrast to other pulse shaping techniques the presented setup is robust, alignment free, provides excellent beam quality and is also suitable for pulse durations up to several nanoseconds.