arXiv subjects

Anupamaa Rampur

Publications and source records attributed to Anupamaa Rampur.

6 recordsLinked to original sources

arXiv2026

Measured group birefringence and group velocity dispersion of elliptical-core ZBLAN fibres for mid-infrared supercontinuum generation

Polarisation-maintaining ZBLAN optical fibres with small elliptical cores are attractive for nonlinear frequency conversion, for example in supercontinuum generation (SCG), and for dispersion management in ultrafast fibre laser systems operating in the mid-infrared (MIR) spectral region. Accurate characterisation of group birefringence and group velocity dispersion (GVD) is essential for modelling ultrafast pulse propagation in such fibres, yet experimental data remain scarce. Here, we present broadband measurements of group birefringence and GVD in four elliptical-core ZBLAN fibres, selected for their potential for low-noise MIR SCG, over the wavelength range 1.4 to 4.3 μm. Using polarisation-resolved white-light spectral interferometry, we quantify the dispersion characteristics of both fundamental modes in each fibre. Measurement uncertainties are evaluated using a combined uncertainty analysis that includes the spread between repeated measurements and the uncertainty in the measured fibre length. This work aims to support the development of MIR supercontinuum sources and to facilitate the understanding of nonlinear optical phenomena in ZBLAN fibres.

physics.optics↗

arXiv2026

Ultra-low-noise supercontinuum in normal-dispersion ZBLAN fibres pumped at 1.85 $μ$m

We demonstrate, for the first time to our knowledge, ultra-low-noise supercontinuum (SC) generation in normal-dispersion fluoride fibres pumped by femtosecond (fs) pulses. We have investigated two elliptical-core polarisation-maintaining (PM) ZBLAN fibres with core dimensions 6.7$\times$2.7 $μ$m and 8.9$\times$4.1 $μ$m, experimentally measured to have normal dispersion up to 3.77 $μ$m and 3.25 $μ$m, respectively; the smaller-core fibre yields ultra-low-noise SC spanning 1.537-2.196 $μ$m with a minimum relative-intensity noise (RIN) of 0.22% at 1.7 $μ$m, and the larger-core fibre yields 1.507-2.250 $μ$m with 0.36% at 2.0 $μ$m. To aid the generation of low-noise SC, we developed an all-PM thulium chirped-pulse amplifier delivering 58 fs pulses at 1.85 $μ$m, 210 mW average power at 40 MHz, with 0.41% RIN, seeded by a part of an ultra-low-noise SC using a 1.55 $μ$m fs laser and an all-normal-dispersion (ANDi) silica fibre for precise seed control. These results establish a robust, alignment-free pathway to extend ultra-low-noise ANDi-fibre SC towards the mid-infrared using PM fluoride fibres.

physics.optics↗

arXiv2019

Low noise all-fiber amplification of a coherent supercontinuum at 2 μm and its limits imposed by polarization noise

We report the amplification of an all-normal dispersion supercontinuum pulse in a Thulium / Holmium co-doped all-fiber chirped pulse amplification system. With a -20 dB bandwidth of more than 300 nm in the range 1800-2100 nm the system delivers high quality 66 fs pulses with more than 70 kW peak power directly from the output fiber. The coherent seeding of the entire emission bandwidth of the doped fiber and the stability of the supercontinuum generation dynamics in the silicate glass all-normal dispersion photonic crystal fiber result in excellent noise characteristics of the amplified ultrashort pulses.

physics.optics↗

arXiv2019

Development of highly nonlinear polarization maintaining fibers with normal dispersion across entire transmission window

Determined polarization state of light is required in nonlinear optics applications related to ultrashort and single-cycle light pulse generation. Such short time scales require up to full octave of spectral width of light. Fiber-based, pulse-preserving and linearly polarized supercontinuum can meet these requirements. We report on the development - from linear simulations of the fiber structure, through fabrication of physical fibers to their versatile characterization - of polarization maintaining, highly nonlinear photonic crystal fibers, intended for femtosecond pumping at a wavelength of 1560 nm. Full octave of linearly polarized light around this wavelength would enable to cover amplification bandwidths of the three major fiber amplifiers from ytterbium doped systems up to thulium and holmium doped fiber amplifiers, with a coherent, linearly polarized seed signal. At the same time, an all-normal chromatic dispersion profile over an entire transmission window, and small dispersion of nonlinearity in the developed fibers, would facilitate use of commercially available femtosecond fiber lasers as pump sources for the developed fibers.

physics.app-ph↗

arXiv2018

Development of suspended core soft glass fibers for far-detuned parametric conversion

Light sources utilizing \c{hi}(2) parametric conversion combine high brightness with attractive operation wavelengths in the near and mid-infrared. In optical fibers it is possible to use \c{hi}(3) degenerate four-wave mixing in order the obtain signal-to-idler frequency detuning of over 100 THz. We report on a test series of nonlinear soft glass suspended core fibers intended for parametric conversion of 1000-1100 nm signal wavelengths available from an array of mature lasers into the near-to-mid-infrared range of 2700-3500 nm under pumping with an erbium sub-picosecond laser system. Presented discussion includes modelling of the fiber properties, details of their physical development and characterization, as well as experimental tests of parametric conversion.

physics.optics↗

arXiv2018

Dispersion Measurement of Ultra-High Numerical Aperture Fibers covering Thulium, Holmium, and Erbium Emission Wavelengths

We present broadband group velocity dispersion (GVD) measurements of commercially available ultra-high numerical aperture fibers (UHNA1, UHNA3, UHNA4, UHNA7 and PM2000D from Coherent-Nufern). Although these fibers are attractive for dispersion management in ultrafast fiber laser systems in the 2 μm wavelength region, experimental dispersion data in literature is scarce and inconsistent. Here we demonstrate the measurements using the spectral interferometry technique covering the typically used erbium, thulium and holmium emission bands. The results are characterized in terms of the standard-deviation uncertainty and compared with previous literature reports. Fitting parameters are provided for each fiber allowing for the straightforward replication of the measured dispersion profiles. This work is intended to facilitate the design of ultrafast fiber laser sources and the investigations of nonlinear optical phenomena.

physics.ins-det↗