Increased mid-infrared supercontinuum bandwidth and average power by tapering large-mode-area chalcogenide photonic crystal fibers

Abstract

The trade-off between the spectral bandwidth and average output power from chalcogenide fiber-based mid-infrared supercontinuum sources is one of the major challenges towards practical application of the technology. In this paper we address this challenge through tapering of large-mode-area chalcogenide photonic crystal fibers. Compared to previously reported step-index fiber tapers the photonic crystal fiber structure ensures single-mode propagation, which improves the beam quality and reduces losses in the taper due to higher-order mode stripping. By pumping the tapered fibers at 4 μm using a MHz optical parametric generation source, and choosing an appropriate length of the untapered fiber segments, the output could be tailored for either the broadest bandwidth from 1 to 11.5 μm with 35.4 mW average output power, or the highest output power of 57.3 mW covering a spectrum from 1 to 8 μm.

Mid-infrared fiber-coupled supercontinuum spectroscopic imaging using a tapered chalcogenide photonic crystal fiber

“…The SC spectrum display clear signs of water absorption from 5.5-7.5 μm due to the atmosphere, and the sharp dip at 6.3 μm coincide with the water impurity absorption in the ChG glass. Unlike previous experiments with similar tapered ChG PCFs reported in [6] the spectrum did not extend beyond 7.5 μm due to a series of design compromises, such as a long uniform fiber length and a fiber geometry suitable for endcapping and connectorization. …”

“…Broadband SC generation spanning 2-7.5 μm was achieved by pumping the ChG PCF with around 250 fs pulses at 4.35 μm (85 nm bandwidth) from a single-pass MHz optical parametric amplifier [6]. The pump wavelength was chosen to fit between the CO 2 and Se-H absorption features to reduce losses and avoid damage at the input.…”

“…However, only preliminary work has been performed with using supercontinuum (SC) sources for spectroscopic imaging in the mid-IR region [3][4][5]. The use of mid-IR supercontinuum sources for spectroscopic imaging has the potential for covering both the functional group region (2.5-6.7 μm) and part of the fingerprint region (6.7-15 μm) from a single compact source [6][7][8][9], that can be several orders of magnitude brighter than a synchrotron IR beamline [5] whilst being compatible with existing broadband technologies such as Fouriertransform infrared (FTIR) spectrometry and array detectors. This demonstration represents one of the first steps toward developing SC-based spectroscopic imaging in the mid-IR and is among several results of the European research project MINERVA: MId-to NEaR infrared spectroscopy for improVed medical diAgnostics, that was a collaboration between thirteen organizations from industry and academia across seven European nations with the goal of developing mid-IR technologies for high-volume pathology screening and in-vivo skin surface examination for the early diagnosis of cancer.…”

A novel chalcohalide fiber with high nonlinearity and low material zero‐dispersion via extrusion

“…On the other hand, these ChH glasses have larger nonlinear refractive index ( n 2 ) but lower linear refractive index ( n 0 ) than the conventional As 2 S 3 glass, as shown in Table . Comparing the ZDW of 3.5 μm in microstructured GeAsSe/AsSe fibers, this step‐index ChH fiber shows a material ZDW of 3.5 μm. This would be convenient for dispersion tailoring to approach for the Ho + ‐doped fiber laser pumping …”

Chalcogenide-glass polarization-maintaining photonic crystal fiber for mid-infrared supercontinuum generation

“…Supercontinuum (SC) generation towards the mid-infrared (MIR) range is a very active field of research motivated by a wide range of applications including optical coherence tomography (OCT), material processing, optical sensing and absorption spectroscopy [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Although much progress in this field has been reported recently, state-of-the-art mid-IR SC systems are still in their infancy and considerable effort is required before mature broadband IR SC light sources beyond 5 μm are made available for industrial applications.…”