Supercontinuum generation by higher-order mode excitation in a photonic crystal fiber

Abstract

We describe an experiment in which a train of femtosecond pulses is coupled into a photonic crystal fiber (PCF) by means of an offset pumping technique that can selectively excite either the mode LP(01) or LP(11) or LP(21). The PCF presents a wide range of wavelengths in which the fundamental mode experiences normal dispersion, whereas LP(11) and LP(21) propagate in the anomalous dispersion regime, generating a supercontinuum based on the soliton fission mechanism. We find that the existence of a cut-off wavelength for the higher-order modes makes the spectral broadening asymmetrical. This latter effect is particularly dramatic in the case of the LP(21) mode, in which, by using a pump wavelength slightly below cut-off, the spectral broadening occurs only on the blue side of the pump wavelength. Our experimental results are successfully compared to numerical solutions of the nonlinear Schrödinger equation.

High-Power Supercontinuum generation with picosecond pulses

“…We finally investigate the effects of a mode cutoff at long wavelengths, as realized in SCG in higher order fiber modes. Such a system has recently been proposed as a means to enhance short wavelength conversion in the fs pumping regime [5]. Our simulations suggest fundamentally different behavior in the ps regime.…”

“…3. This significant difference in behavior compared to the fs regime [5] is explained by the nature of the SCG process for ps pulses. Modulation instability is based on a degenerate four-wave mixing process where two pump photons are converted into one photon each in a short-wavelength and in a long-wavelength sideband.…”

“…Recent work has suggested that supercontinuum generation with fs pulses exhibits improved short wavelength conversion efficiencies when a multimode fiber is pumped in a higher order mode, where the mode cutoff prevents the transfer of power to long wavelengths [5]. Here we consider the same idea for ps pumping.…”

Demonstration of Intermodal Four-Wave Mixing by Femtosecond Pulses Centered at 1550 nm in an Air-Silica Photonic Crystal Fiber

“…The coupling efficiency can be up to 63%. In the beginning, the pump beam is launched close to the central axis of the PCF core by adjusting the distance between the microscope objective and the input tip of the fiber (the offset pumping technique [28], [29]). At this time, the 1st guided-mode can be selectively excited.…”

Infrared supercontinuum from a large mode area PCF under extreme picosecond excitation

“…white-light or supercontinuum (SC) generation, was demonstrated in a number of condensed media (Alfano and Shapiro 1970a,b;Alfano 1989), liquids (Weinberg 1969, Penzkofer et al 1973Penzkofer 1974;Lee Smith et al 1977), gases (Alfano and Shapiro 1970b;Corkun et al 1986;François et al 1993;Ilkov et al 1993), and fibers, including multi-mode (Baldeck et al 1987), dispersion-shifted (Mori et al 1995), and photonic crystal fibers (PCFs; Dudley et al 2006;Genty et al 2007;Birks et al 1997;Ranka et al 2000;Rulkov et al 2005;Provino et al 2001;Cherif et al 2008).…”