Spectral transformation of megawatt femtosecond optical pulses in large-mode-area high-index-step photonic-crystal fibers

Abstract

An assortment of photonic-crystal fibers with a core area varying from 20 to 50 µm 2 is used to demonstrate efficient frequency conversion of megawatt femtosecond Cr:forsterite laser pulses with a central wavelength of 1.24 µm into the visible and infrared spectral ranges. Supercontinuum radiation with a spectrum spanning from 500 to 1800 nm and total output energy of hundreds of nanojoules is observed at the fiber output. Novel compact broadband light sources based on supercontinuum generation in photonic-crystal fibers (PCFs) [1,2] are emerging as powerful tools for optical science and ultrafast laser technologies [3]. In optical metrology, supercontinuum generation in PCFs [4] is used as a mechanism whereby frequency combs generated by modelocked femtosecond lasers are broadened to more than an octave, allowing calibration of frequency combs for high-precision measurements of frequency and time intervals, thus leading to a tremendous simplification of optical metrological measurements [5][6][7][8].In ultrafast science, supercontinua generated in PCFs give an access to the carrier-envelope phase (CEP) slip [9], thus offering an unprecedented control over few-cycle field waveform synthesis [10], allowing the generation of single attosecond pulses [11], and suggesting new approaches in time-resolved spectroscopy on the attosecond time scale [12][13][14]. Other important applications of supercontinuum generation and, more generally, nonlinearoptical transformations of laser pulses in PCFs [15] include the development of novel compact fiber-format light sources for nonlinear spectroscopy [16][17][18], microscopy [19][20][21] and optical coherence tomography [22].Small-core PCFs, typically operating in the regime of anomalous dispersion, show an excellent performance as supercontinuum sources ideally suited for nano-and subnanojoule input laser pulses. To accommodate higher input energies without the risk of laser-induced damage of the fiber material, PCFs with a larger core size are needed. Such large-mode-area (LMA) PCF components [23,24]

Ultra‐large mode area mid‐infrared fiber based on chalcogenide glasses extrusion

“…Moreover, LMA fibers can effectively restrain the amplified spontaneous emission in laser transmission 7 . Therefore, many laser delivery systems 8‐10 need LAM fibers with high NA to increase the fiber power threshold. Currently, many glasses including silica, 11 fluoride, 12 and chalcogenide 13 are introduced to develop LAM fibers for mid‐infrared high‐power laser transmission.…”

High peak power continuum generation by high-order solitons at the mid-infrared wavelength in a photonic crystal fiber

“…Over the last few years, some important attempts have been made to extend the visible and near-infrared sides of the continuum in silica-core PCFs to obtain compact ultrashort pulse sources for the basic physical science [14][15][16][17][18][19][20][21][22][23][24]. It has been demonstrated that the visible components have been mainly based on the DWs when the resonance condition between the solitons and the DWs are satisfied, and the near-infrared components result from the soliton effect.…”

Efficient red-shifted dispersive wave in a photonic crystal fiber for widely tunable mid-infrared wavelength generation

“…However, some interesting nonlinear applications have involved the generation of narrowband frequency components. The unique flexibility of the dispersion and nonlinearity management provided by PCFs is a key enabling mechanism for the generation of narrowband light source within a wide wavelength range [5,6]. The PCF-based nonlinear frequency conversion techniques have been developed to efficiently convert the pump power into the targeted spectral band.…”