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CMOS-compatible nonlinear optics platforms with negligible nonlinear losses and high nonlinearity are of great merit. Silicon, silicon nitride and Hydex glass have made significant headway in nonlinear optical signal processing, though none of these platforms possesses the highly sought after combination of high nonlinearity and negligible nonlinear losses. In this manuscript, we present a nonlinear optics platform based on silicon-rich nitride, deposited at a low temperature of 250°C compatible with back-end CMOS processing. The silicon-rich nitride is designed and engineered in composition to have a bandgap of 2.05 eV, such that the two-photon absorption edge is well below 1.55 μm. The designed and developed waveguides have a nonlinear parameter of 550 W−1/m, 500 times larger than that in silicon nitride waveguides, while at the same time not possessing two-photon and free-carrier losses. Using 500-fs pulses, we generate supercontinuum exceeding 0.6 of an octave.

Wavefront manipulation in metasurfaces typically relies on phase mapping with a finite number of elements. In particular, a discretized linear phase profile may be used to obtain a beam bending functionality. However, discretization limits the applicability of this approach for high angle bending due to the drastic efficiency drop when the phase is mapped by a small number of elements. In this work, we discuss a novel concept for energy redistribution in diffraction gratings and its application in the visible spectrum range, which helps overcome the constraints of ultrahigh angle (above 80°) beam bending. Arranging asymmetric dielectric nanoantennas into diffractive gratings, we show that one can efficiently redistribute the power between the grating orders at will. This is achieved by precise engineering of the scattering pattern of the nanoantennas. The concept is numerically and experimentally demonstrated at visible frequencies using several designs of TiO2 (titanium dioxide) nanoantennas for medium (...

Silicon-rich nitride films are developed and explored using an inductively coupled plasma chemical vapor deposition system at low temperature of 250 °C with an ammonia-free gas chemistry. The refractive index of the developed silicon-rich nitride films can increase from 2.2 to 3.08 at 1550 nm wavelength while retaining a near-zero extinction coefficient when the amount of silane increases. Energy dispersive spectrum analysis gives the silicon to nitrogen ratio in the films. Atomic force microscopy shows a very smooth surface, with a surface roughness root-mean-square of 0.27 nm over a 3 μm × 3 μm area of the 300 nm thick film with a refractive index of 3.08. As an application example, the 300 nm thick silicon-rich nitride film is then patterned by electron beam lithography and etched using inductively coupled plasma system to form thin-film micro/nano waveguides, and the waveguide loss is characterized.

Optically-pumped microsquare cavity laser on InP-based multiple-quantum-wells (MQW) material platform is demonstrated. Continuous wave operation is achieved for microsquare cavity with footprint as small as 4×4μm 2 . Numerical mode analysis and experimental characterization of the microsquare laser are conducted, and the results are compared with the commonly used microdisk cavity laser fabricated on the same platform. The microsquare laser shows a lower lasing threshold and infers a higher differential efficiency than the microdisk counterpart. The microsquare cavity laser has sufficiently high quality factor, and higher pumping injection efficiency due to the more evenly distributed field profile as compared to that of the microdisk. Experimental result also shows that the microsquare laser has better temperature stability than the microdisk. These results promise a potential alternative laser structure for onchip light source applications.

Supercontinuum generation over 0.6 of an octave is demonstrated at 1.55µm on silicon-rich nitride waveguides. The SRN films are engineered to have a band gap of 1.85eV, and do not suffer from two-photon absorption at 1.55µm. The SRN waveguides have a large nonlinear parameter of 550W-1/m, 500 times larger than that in silicon nitride waveguides.