Abstract
This work reports on the fabrication and subsequent supercontinuum generation in a Ge-As-Se-Te/Ge-As-Se core/clad chalcogenide step-index fiber with an elliptical-core and an ultra-high numerical aperture of 1.88 ± 0.02 from 2.5 - 15 µm wavelength. The fiber has very low transmission loss of < 2 dB/m from 5-11 µm and a minimum loss of 0.72 ± 0.04 dB/m at 8.56 µm. Supercontinuum spanning from 2.1 µm to 11.5 µm with an average power of ∼6.5 mW was achieved by pumping a ∼16 cm fiber with a minor/major axis core diameter of 4.2/5.2 µm with 250 fs pulses at 4.65 µm wavelength and a repetition rate of 20.88 MHz. The effect of the elliptical-core was investigated by means of mechanical rotation of the fiber relative to the linear pump polarization, and it was found to cause a shift in the supercontinuum spectral edges by several hundred nanometers.
Highlights
In recent years there has been an increasing interest in powerful and versatile broadband light sources for bio-imaging, spectroscopy, microscopy, and sensing applications [1,2,3,4,5,6]
This work reports on the fabrication and subsequent supercontinuum generation in a Ge-As-Se-Te/Ge-As-Se core/clad chalcogenide step-index fiber with an elliptical-core and an ultra-high numerical aperture of 1.88 ± 0.02 from 2.5 - 15 μm wavelength
The effect of the elliptical-core was investigated by means of mechanical rotation of the fiber relative to the linear pump polarization, and it was found to cause a shift in the supercontinuum spectral edges by several hundred nanometers
Summary
In recent years there has been an increasing interest in powerful and versatile broadband light sources for bio-imaging, spectroscopy, microscopy, and sensing applications [1,2,3,4,5,6]. By melting the covalently bonded solids, comprising chalcogenide elements (S, Se, Te) with Group XV elements (Sb, As) and Group XIV (Ge, Si), glasses with unique optical and semiconducting properties may be obtained [17] These glasses are suitable for many passive MIR applications such as radiometric thermometry and CO2 laser power delivery due to their low phonon energy and environmental stability [17,18,19]. They have been demonstrated as suitable for broadband MIR SCG due to their high optical nonlinearity [14,20,21]. Fibers of several core diameters were fabricated and tested for SCG by pumping with a kW peak power DFG source delivering 250 fs pulses at 4.65 μm wavelength and with a pulse repetition rate of 20.88 MHz
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