Coherent octave spanning near-infrared and visible supercontinuum generation in all-normal dispersion photonic crystal fibers

Abstract

We present the first detailed demonstrations of octave-spanning SC generation in all-normal dispersion photonic crystal fibers (ANDi PCF) in the visible and near-infrared spectral regions. The resulting spectral profiles are extremely flat without significant fine structure and with excellent stability and coherence properties. The key benefit of SC generation in ANDi PCF is the conservation of a single ultrashort pulse in the time domain with smooth and recompressible phase distribution. For the first time we confirm the exceptional temporal properties of the generated SC pulses experimentally and demonstrate their applicability in ultrafast transient absorption spectroscopy. The experimental results are in excellent agreement with numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking. To our knowledge, we present the broadest spectra generated in the normal dispersion regime of an optical fiber.

All-Normal Dispersion Chalcogenide PCF for Ultraflat Mid-Infrared Supercontinuum Generation

“…The value of n 2 makes half at 3.1 µm from its earlier value mentioned at 1.55 µm. We evaluate A eff = 7.07 µm 2 at a pump wavelength to calculate γ = 1.05 /W/m as Heidt et al [8] suggested constant γ achieves a better fit than A eff dependent n 2 . The GVD parameter D = -3.92 ps/nm/km measured at this wavelength (dotted red curve in Fig.…”

“…The noise and amplitude fluctuation induced in spectral components can be reduced significantly by suppressing the soliton fission during SC evolution by using short waveguide design [7]. The suppression of soliton fission during pulse propagation can be achieved by obtaining the entire dispersion regime below the ZDW (GVD = 0 line) through GVD engineering of the PCF [8]. During all-normal dispersion pumping SC generation, the spectral broadening in a short waveguide is mainly dominated by selfphase modulation (SPM) and optical wave breaking (OWB) [9].…”

“…A number of theoretical and experimental investigations on coherent SC generation was reported with pumping the silica photonic crystal fibers (PCFs) in all-normal dispersion (ANDi) region by femtosecond lasers [6], [8], [10]- [12]. However, the transmission loss of silica glass beyond 2.2 µm limits the SC broadening in the MIR region.…”

All-Normal-Dispersion Chalcogenide Waveguides for Ultraflat Supercontinuum Generation in the Mid-Infrared Region

“…It was reduced by a factor of two at 3.1 µm. We use A eff at a pump wavelength to calculate γ as the constant γ obtains a better fit between simulation and measurement than A eff dependent n 2 which is described in [5]. In numerical simulations, in the case of 1.55 µm pump, we consider sech-shape input pulses of 50-fs duration with peak powers between 25 W and 100 W. However, in the case of 3.1 µm pump, pulses have 85-fs and much larger peak powers between 0.1 kW and 3 kW.…”

“…Since pulses do not propagate as solitons, it becomes possible to produce SC spectra with high coherence and high spectral flatness [5]. Although optical pulse evolution in a normally dispersive waveguide leads to a relatively narrower spectra than anomalous dispersion regime, comparatively smooth and flat spectra can be observed through the suppression of soliton fission under the same operating condition [6].…”