Abstract
Hydrogenated amorphous silicon (a:Si-H) has recently been recognized as a highly nonlinear CMOS compatible photonic platform. We experimentally demonstrate the generation of a supercontinuum (SC) spanning over 500 nm in a-Si:H photonic wire waveguide at telecommunication wavelengths using femtosecond input pulse with energy lower than 5 pJ. Numerical modeling of pulse propagation in the waveguide, based on the experimentally characterized dispersion profile, shows that the supercontinuum is the result of soliton fission and dispersive wave generation. It is demonstrated that the SC is highly coherent and that the waveguides do not suffer from material degradation under femtosecond pulse illumination. Finally, a direct comparison of SC generation in c-Si and a-Si:H waveguides confirms the higher performances of a-Si:H over c-Si for broadband low power SC generation at telecommunication wavelengths.
Highlights
Since its first discovery in the early seventies by Alfano and Shapiro [1], the phenomenon of supercontinuum generation (SCG) has been thoroughly studied, since the advent of photonic crystal fibers (PCFs)
The soliton number at the input is N = 6.0, a value close to the number of ejected pulses. This is in contrast with the results reported in crystalline silicon (c-Si) at telecommunication wavelengths where the pulse splitting results in the generation of a small number, largely lower than the initial soliton number, of equal fundamental solitons, because of the large TPA experienced in this latter structure [28]
We have experimentally studied the generation of supercontinuum in hydrogenated amorphous silicon photonic wires in the femtosecond regime at telecommunication wavelengths
Summary
Since its first discovery in the early seventies by Alfano and Shapiro [1], the phenomenon of supercontinuum generation (SCG) has been thoroughly studied, since the advent of photonic crystal fibers (PCFs). As crystalline silicon (c-Si) waveguides, a-Si:H photonic wires can be fabricated with CMOS compatible processes on silicon-on-insulator It has the advantage over c-Si of being characterized by a higher nonlinear refractive index and a lower nonlinear absorption coefficient resulting from a larger bandgap energy. Thanks to these favorable properties, the generation of a broad supercontinuum, seeded by picosecond pulses, in a-Si:H waveguides with low anomalous dispersion at 1550 nm has been demonstrated [5]. The initial spectral broadening is expected to be dominated by self-phase modulation [2] and a highly coherent SC should be generated
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