49 research outputs found
Poor-man's model of hollow-core anti-resonant fibers
We investigate various methods for extending the simple analytical capillary
model to describe the dispersion and loss of anti-resonant hollow-core fibers
without the need of detailed finite-element simulations across the desired
wavelength range. This poor-man's model can with a single fitting parameter
quite accurately mimic dispersion and loss resonances and anti-resonances from
full finite-element simulations. Due to the analytical basis of the model it is
easy to explore variations in core size and cladding wall thickness, and should
therefore provide a valuable tool for numerical simulations of the ultrafast
nonlinear dynamics of gas-filled hollow-core fibers.Comment: In preparatio
Multi-stage generation of extreme ultraviolet dispersive waves by tapering gas-filled hollow-core anti-resonant fibers
In this work, we numerically investigate an experimentally feasible design of
a tapered Ne-filled hollow-core anti-resonant fiber and we report the
generation of multiple dispersive waves (DWs) in the range 90-120 nm, well into
the extreme ultraviolet (UV) region. The simulations assume an 800 nm pump
pulse with 30 fs 10 J pulse energy, launched into a 9 bar Ne-filled fiber
with m initial core diameter that is then tapered to a m core
diameter. The simulations were performed using a new model that provides a
realistic description of both loss and dispersion of the resonant and
anti-resonant spectral bands of the fiber, and also importantly includes the
material loss of silica in the UV. We show that by first generating solitons
that emit DWs in the far-UV region in the pre-taper section, optimization of
the following taper structure can allow re-collision with the solitons and
further up-conversion of the far-UV DWs to the extreme-UV with energies up to
190 nJ in the 90-120 nm range. This process provides a new way to generate
light in the extreme-UV spectral range using relatively low gas pressure
Multi-wavelength high energy gas-filled fiber Raman laser spanning from 1.53 um to 2.4 um
In this work, we present a high pulse energy multi-wavelength Raman laser
spanning from 1.53 um up to 2.4 um by employing the cascaded rotational
stimulated Raman scattering (SRS) effect in a 5-m hydrogen (H2) -filled nested
anti-resonant fiber (NARF), pumped by a linearly polarized Er/Yb fiber laser
with a peak power of ~13 kW and pulse duration of ~7 ns in the C-band. The
developed Raman laser has distinct lines at 1683 nm, 1868 nm, 2100 nm, and 2400
nm, with pulse energies as high as 18.25 uJ, 14.4 uJ, 14.1 uJ, and 8.2 uJ,
respectively. We demonstrate how the energy in the Raman lines can be
controlled by tuning the H2 pressure from 1 bar to 20 ba
Noise performance and long-term stability of near- and mid-IR gas-filled fiber Raman lasers
In this letter, the characteristics of noise and long-term stability of near-
and mid-infrared (near-IR and mid-IR) gas-filled fiber Raman lasers have been
investigated for the first time. The results reveal that an increase in Raman
pulse energy is associated with a decrease in noise, and that the relative
pulse peak intensity noise (RIN) is always lower than the relative pulse energy
noise (REN). We also demonstrate that long-term drift of the pulse energy and
peak power are directly linked with the high amount of heat release during the
Raman Stokes generation. The demonstrated noise and long-term stability
performance provide necessary references for potential spectroscopic
applications as well as further improvements of the emerging mid-IR gas-filled
hollow-core fiber (HCF) Raman laser technology
Noise and spectral stability of deep-UV gas-filled fiber-based supercontinuum sources driven by ultrafast mid-IR pulses
Deep-UV (DUV) supercontinuum (SC) sources based on gas-filled hollow-core
fibers constitute perhaps the most viable solution towards ultrafast, compact,
and tunable lasers in the UV spectral region. Noise and spectral stability of
such broadband sources are key parameters that define their true potential and
suitability towards real-world applications. In order to investigate the
spectral stability and noise levels in these fiber-based DUV sources, we
generate an SC spectrum that extends from 180 nm (through phase-matched
dispersive waves - DWs) to 4 {\mu}m by pumping an argon-filled hollow-core
anti-resonant fiber at a wavelength of 2.45 {\mu}m. We characterize the
long-term stability of the source over several days and the pulse-to-pulse
relative intensity (RIN) noise of the strongest DW at 275 nm. The results
indicate no sign of spectral degradation over 110 hours, but the RIN of the DW
pulses at 275 nm is found to be as high as 33.3%. Numerical simulations were
carried out to investigate the spectral distribution of the RIN and the results
confirm the experimental measurements and that the poor noise performance is
due to the RIN of the pump laser, which was hitherto not considered in
numerical modelling of these sources. The results presented herein provide an
important step towards an understanding of the noise mechanism underlying such
complex light-gas nonlinear interactions and demonstrate the need for pump
laser stabilization