Abstract
Supercontinuum (SC) generation based on ultrashort pulse compression constitutes one of the most promising technologies towards ultra-wide bandwidth, high-brightness, and spatially coherent light sources for applications such as spectroscopy and microscopy. Here, multi-octave SC generation in a gas-filled hollow-core antiresonant fiber (HC-ARF) is reported spanning from 200 nm in the deep ultraviolet (DUV) to 4000 nm in the mid-infrared (mid-IR) having an output energy of 5 μJ. This was obtained by pumping at the center wavelength of the first anti-resonant transmission window (2460 nm) with ~100 fs pulses and an injected pulse energy of ~8 μJ. The mechanism behind the extreme spectral broadening relies upon intense soliton-plasma nonlinear dynamics which leads to efficient soliton self-compression and phase-matched dispersive wave (DW) emission in the DUV region. The strongest DW is observed at 275 nm which corresponds to the calculated phase-matching wavelength of the pump. Furthermore, the effect of changing the pump pulse energy and gas pressure on the nonlinear dynamics and their direct impact on SC generation was investigated. This work represents another step towards gas-filled fiber-based coherent sources, which is set to have a major impact on applications spanning from DUV to mid-IR.
Highlights
Most reports on SC generation in the literature are based on solid-core silica photonic crystal fibers (PCF) where the microstructured cladding of the fiber allows tailoring of the group velocity dispersion (GVD), which is an important property that greatly influences the nonlinear effects[11]
By coupling 100 fs, 20 μJ pulses into a specially designed argon (Ar) filled hollow-core antiresonant fiber (HC-ARF) under 30 bar pressure, soliton self-compression dynamics enabled broadening from 200 nm to 4000 nm. It was experimentally demonstrated how the pulse energy and the pressure have a crucial role in the mid-IR spectral broadening and emission of dispersive wave (DW) in the deep ultraviolet (DUV)
The fiber consists of a hollow core surrounded by seven non-touching silica capillaries with wall thickness of ~640 nm forming a core with diameter of ~44 μm, as shown in the scanning electron microscopy (SEM) image of Fig. 1(a)
Summary
Simulations predict a very bright and spectrally coherent continuum. The coherence of light sources is very crucial for many applications such as spectroscopy and other quantitative techniques where fluctuations in intensity will result in increased noise, thereby reducing the signal to noise ratio. The main limitation of the spectral extension towards the mid-IR is the increasing propagation losses, reaching 100 dB/m at 3500 nm from which silica multiphonon absorption is the dominant loss mechanism The pressure begins to have a more pronounced effect on the mid-IR and UV-visible regime These dynamics are shown for 5 mW output power in Fig. 4(c) using a base 2 logarithmic wavelength axis for better visibility of the UV region. A total measured average output power of 5 mW (at 1 kHz repetition rate) was obtained with a strong resonant DW emission at 275 nm It was experimentally demonstrated how the pump energy and pressure increases the nonlinearity resulting in increased mid-IR spectral broadening and efficient DW emission in the DUV range. The current work constitutes an efficient route towards ultrafast source for spectroscopy both in the mid-IR molecular fingerprinting and in the DUV spectral region
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