Watt-level and spectrally flat mid-infrared supercontinuum in fluoroindate fibers

Abstract

We report on infrared supercontinuum (SC) generation in step-index fluoroindate-based fiber by using an all-fiber laser source. In comparison to widely used ZBLAN fibers for high-power mid-infrared (MIR) SC generation, fluoroindate fibers have multiphoton absorption edges at significantly longer wavelengths and can sustain similar intensities. Recent developments highlighted in the present study allowed the production of fluoroindate fibers with MIR background loss of 2 dB/km, which is similar to or even better than ZBLAN fibers. By using an all-fiber picosecond laser source based on an erbium amplifier followed by a thulium power amplifier, we demonstrate the generation of 1.0 W infrared SC spanning over 2.25 octaves from 1 μm to 5 μm. The generated MIR SC also exhibits high spectral flatness with a 6 dB spectral bandwidth from 1.91 μm to 4.77 μm and an average power two orders of magnitude greater than in previous demonstrations with a similar spectral distribution.

Recent development of flat supercontinuum generation in specialty optical fibers

“…In the frequency domain, MI broadens the spectrum. As the pulses propagate through the nonlinear fiber, each sub-pulse undergoes further spectral broadening through MI, stimulated Raman scattering as well as Raman soliton self-frequency shift 1 . In the normal dispersion region of the fiber, when the fiber is pumped by femtosecond, the SC generation is mainly controlled by self-phase modulation.…”

“…Supercontinuum (SC) laser sources exhibiting excellent wide bandwidth and good beam quality have attracted much attention because of their potential applications including spectroscopy, optical coherence tomography, chemical detection, biomedicine, as well as homeland security, etc [1][2][3][4] . The common method for SC generation is achieved by a piece of highly nonlinear medium pumped by ultra-short pulses 5 .…”

Infrared supercontinuum generated in concatenated InF3 and As2Se3 fibers

“…Supercontinuum (SC) sources using fluorozirconate based fibers have reached watt level powers [4][5][6][7][8][9], but are restricted to wavelengths below ~4.2 µm when using long fibers. A wavelength extension of the SC above 5 µm is also possible when considering fluoroindate (InF 3 ) glass fibers [10][11][12][13]. The intrinsic fiber loss due to the multiphonon absorption edge in these fluoride-fibers is the main limitation on the longwavelength side for SC generation.…”

“…A lot of effort has gone into producing high purity fibers in order to decrease the detrimental effects of contaminant absorption on SC broadening. Such improvements of the fluoride and ChG transmission allowed the generation of ultrabroadband SC in these fibers [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][23][24][25][26][27][28][29].…”

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.…”