Optical nonlinearities in ultra-silicon-rich nitride characterized using z-scan measurements

Abstract

The dispersive nonlinear refractive index of ultra-silicon-rich nitride, and its two-photon and three-photon absorption coefficients are measured in the wavelength range between 0.8 µm–1.6 µm, covering the O- to L – telecommunications bands. In the two-photon absorption range, the measured nonlinear coefficients are compared to theoretically calculated values with a simple parabolic band structure. Two-photon absorption is observed to exist only at wavelengths lower than 1.2 μm. The criterion for all-optical switching through the material is investigated and it is shown that ultra-silicon-rich nitride is a good material in the three-photon absorption region, which spans the entire O- to L- telecommunications bands.

High spectro-temporal compression on a nonlinear CMOS-chip

“…In the temporal compression process, the peak power of the pulse is modified primarily by the pulse profile, including the presence and extent of pedestals, as well as linear losses of the device. Nonlinear losses from TPA and free-carrier effects have been shown to be absent in USRN 39 , 43 , and therefore have negligible impact on the evolution of the pulse shape, or in restricting the pulse compression dynamics. Three-photon absorption effects were also not observed at the power levels used in the experiments.…”

“…For example, 2.3× soliton-effect compression was demonstrated in silicon photonic crystal waveguides using P peak(in) = 2.4 W 12 , whereas 5× compression was demonstrated in Si 3 N 4 waveguides using considerably higher peak powers ~3.2 kW 16 . Since USRN has a large Kerr nonlinearity and governed by three-photon (rather than two-photon) loss mechanisms at 1550 nm 39 , relatively small powers are required to initiate compression 40 , 41 , while importantly preserving the pulse energy. The temporal compression performance of the USRN system is further plotted in Fig.…”

“…The temporal coordinate, T exists in a moving frame due to the removal of the temporal walk-off induced by the group velocity 42 . The linear and nonlinear refractive indices of USRN are 3.1 and 2.8 × 10 −13 cm 2 W −1 , respectively 39 , 43 The effective mode area of the USRN waveguide is calculated to be 0.26 µm 2 resulting in a nonlinear parameter ( γ ) of 440 W −1 m −1 . The calculated second order dispersion, β 2 for the waveguide = −0.17 ps 2 m −1 at wavelength of 1550 nm.…”

Thermo-optic properties of silicon-rich silicon nitride for on-chip applications

“…A change in effective beat length of the two interfering modes can be actively induced by either changing the refractive index of the MMI waveguide material, or by changing the wavelength to achieve effective switching at the output ports. The former approach, in the case of SRN, can be induced by either utilizing its enhanced nonlinearity (𝜒 (3) , using the well-known DC Kerr effect) [24] or exploit the enhanced thermooptic effects as discussed below.…”

Enhanced photonics devices based on low temperature plasma-deposited dichlorosilane-based ultra-silicon-rich nitride (Si8N)

“…Compared to silicon (Si), USRN has proven absence of 2-photon absorption and free carrier losses 9 , which are common in Si 22 , 23 . Compared to stoichiometric silicon nitride (Si 3 N 4 ) 24 , 25 , the nonlinear refractive index of USRN is reported 9 , 11 to be 100× larger in magnitude. Notably, USRN films have demonstrated high Kerr nonlinearities 11 of 2.8 × 10 –17 m 2 /W 7 , enabling nonlinear photonic devices for high optical parametric gain of 42.5 dB 7 , high spectro-temporal compression 8 , wideband spectral broadening 15 , optical parametric Bragg amplification 16 and observations of Bragg soliton pheonomena 14 , 26 , 27 .…”