Abstract
We experimentally demonstrate quasi-phase-matched (QPM) four-wave-mixing (FWM) in silicon (Si) nanowire waveguides with sinusoidally modulated width. We perform discrete wavelength conversion over 250 nm, and observe 12 dB conversion efficiency (CE) enhancement for targeted wavelengths more than 100 nm away from the edge of the 3-dB conversion bandwidth. The QPM process in Si nanowires is rigorously modeled, with results explaining experimental observations. The model is further used to investigate the dependence of the CE on key device parameters, and to introduce devices that facilitate wavelength conversion between the C-band and mid-IR. Devices based on a superposition of sinusoidal gratings are investigated theoretically, and are shown to provide CE enhancement over the entire C-band. Width-modulation is further shown to be compatible with zero-dispersion-wavelength pumping for broadband wavelength conversion. The results indicate that QPM via width-modulation is an effective technique for extending the spectral domain of efficient FWM in Si waveguides.
Highlights
Four-wave-mixing (FWM) in silicon (Si) nanowire waveguides (SiNWGs) has been investigated as a potential means to alleviate the ever-increasing demand on electronics in future information networks, by facilitating all-optical signal processing near the C-band (1530 nm – 1565 nm) [1,2,3]
Significant work has been reported in this area, including wavelength conversion [1,2,3,4], format conversion [5], signal regeneration [6], signal multicasting [7], time-division-demultiplexing [8, 9], modulation instability [10], and tunable delays [11]; FWM in SiNWGs is starting to emerge as a promising building block for a diverse set of applications well outside the C-band
We use the model to theoretically explore devices designed to facilitate wavelength conversion between the C-band and mid-IR, including devices based on the superposition of sinusoidal gratings, and devices used in conjunction with zero-dispersion-wavelength (ZDWL) pumping, and conclude that QPM via wmodulation is an effective technique for increasing the spectral reach for FWM
Summary
Four-wave-mixing (FWM) in silicon (Si) nanowire waveguides (SiNWGs) has been investigated as a potential means to alleviate the ever-increasing demand on electronics in future information networks, by facilitating all-optical signal processing near the C-band (1530 nm – 1565 nm) [1,2,3]. These results show that SiNWGs can be employed for applications in mid-IR systems, including those for chemical sensing and free-space communications [12] These and other systems applications can be enhanced via an effective means to interconvert between the telecommunications bands and mid-IR wavelengths, opening the possibility of leveraging the large device and materials infrastructure at C-band wavelengths [15, 19, 20, 24]. SiNWGs exhibit tight modal confinement as a result of the high-index contrast inherent to the Si-on-insulator (SOI) platform This contrast both enhances the effective nonlinearity and induces substantial waveguide dispersion [26,27,28,29], which has a detrimental effect on the FWM conversion bandwidth and effectively limits the spectral reach of FWM. We use the model to theoretically explore devices designed to facilitate wavelength conversion between the C-band and mid-IR, including devices based on the superposition of sinusoidal gratings, and devices used in conjunction with zero-dispersion-wavelength (ZDWL) pumping, and conclude that QPM via wmodulation is an effective technique for increasing the spectral reach for FWM
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