Mid-infrared, super-flat, supercontinuum generation covering the 2–5 μm spectral band using a fluoroindate fibre pumped with picosecond pulses

Abstract

Broadband, mid-infrared supercontinuum generation in a step-index fluoroindate fibre is reported. By using ~70-picosecond laser pulses at 2.02 μm, provided by an optical parametric generator, a wide spectrum with a cut-off wavelength at 5.25 μm and a 5-dB bandwidth covering the entire 2–5 μm spectral interval has been demonstrated for the first time. The behaviour of the supercontinuum was investigated by changing the peak power and the wavelength of the pump pulses. This allowed the optimal pumping conditions to be determined for the nonlinear medium that was used. The optical damage threshold for the fluoroindate fibre was experimentally found to be ~200 GW/cm2.

Recent development of flat supercontinuum generation in specialty optical fibers

“…For long pulse pumping fibers, stimulated Raman scattering and four-wave mixing dominate the spectral broadening 10 . The pumping in the anomalous dispersion region and the operation wavelength close to the zero-dispersion wavelength of the nonlinear fiber can realize the effective broadening of the supercontinuum spectrum toward longer wavelength 15 , but the flatness of the spectrum is poor. While pumping in the normal dispersion region of the fiber, the flatness and coherence of the Nonlinear effects spectrum will be better 6 .…”

Spectrally Flat Supercontinuum Generation in a ZBLAN Fiber Pumped by Erbium-Doped Mode-Locked Fiber Laser

“…Since Stolen and Lin observed SC generation in an optical fiber for the first time [6], various types of SC sources have been extensively investigated. Silica fibers have been the predominant nonlinear media of SC generation in the past decades due to their stability and low transmission loss in the visible and near-infrared regions [7]. However, using silica fibers as the nonlinear medium of SC generation is affected by the strong intrinsic material losses in the long wavelength, which limits the spectral broadening towards mid-infrared (mid-IR) [2].…”

“…In practical applications, the SC source produces a flat spectrum over a wide range of wavelength, which not only satisfies the system's spectral bandwidth requirements, but also improves the measurement accuracy and reduces the technical difficulty of power balance [16]. However, SC flatness, which is important for many applications, is still a challenge [7]. At present, the fluctuation of the spectrum is almost larger than 3 dB, especially in the wavelength range of 1600 nm − 1800 nm.…”

Dispersion-Engineered Step-Index Tellurite Fibers for Mid-Infrared Coherent Supercontinuum Generation from 1.5 to 4.5 μm with Sub-Nanojoule Femtosecond Pump Pulses

“…There are two regions in such absorption spectra, namely the functional group region (2-6 µm) that contains the characteristic bands of specific individual bonds and functional groups (i.e., mainly stretching vibrations) and the fingerprint region (6-20 µm) that usually contains a large complex set of absorption bands (i.e., bending vibrations), unique to each molecule and making it difficult to interpret. The common route toward practical mid-IR SC generation in the important functional group region is the implementation of ps-pumped SC generation in commercially-available fluoride fibers [14][15][16], in particular fluoroindate fibers wherein Watt-level SC spanning from 1 to 5 µm can be reached at the expense of the SC coherence properties.…”