On-chip visible-to-infrared supercontinuum generation with more than 495 THz spectral bandwidth

We report ultra-broadband supercontinuum generation in high-confinement Si3N4 integrated optical waveguides. The spectrum extends through the visible (from 470 nm) to the infrared spectral range (2130 nm) comprising a spectral bandwidth wider than 495 THz, which is the widest supercontinuum spectrum generated on a chi

Dispersion engineering silicon nitride waveguides for broadband nonlinear frequency conversion

In this thesis, we investigated nonlinear frequency conversion of optical wavelengths using integrated silicon nitride (Si3N4) waveguides. Two nonlinear conversion schemes were considered: seeded four-wave mixing and supercontinuum generation. The first—seeded four-wave mixing—is investigated by a numerical study and proposed as light source for coherent anti-Stokes Raman scattering (CARS). The compatibility of the silicon nitride-based integrated waveguide with microfluidic channels enables potential applications for on-chip CARS spectroscopy.\ud \ud Both four-wave mixing and supercontinuum generation require waveguides with a large core area to obtain the dispersion required for phase-matched nonlinear frequency conversion. A novel fabrication technique for manufacturing large-core Si3N4 waveguides was investigated. The main advantage of this novel technique is the ability to manufacture crack-free Si3N4 waveguides with sufficient thickness to phase match nonlinear optical processes, while simultaneously realizing a high device yield. To demonstrate that such waveguides can be dispersion engineered and, i.e., allow for phase matching for nonlinear frequency conversion, we experimentally investigated supercontinuum generation in these waveguides using two different pump wavelengths.\ud \ud For a pump wavelength of 1560 nm, the waveguide was dispersion engineered to have a zero-dispersion wavelength just above 1600 nm, such that the pump wavelength experiences anomalous dispersion. The generated supercontinuum spanned more than 700 nm (at -30 dB), limited by the available pump energy. Theoretical modeling showed an exceptionally good agreement with the measured spectrum, and that an octave-spanning supercontinuum is possible if the pump energy is increased. The pulse-to-pulse coherence was calculated for this case and we found that the supercontinuum was fully coherent over its bandwidth (-30 dB), showing that Si3N4 waveguides could be used to generate an optical frequency comb. For a pump wavelength of 1064 nm, the waveguide was designed to have a zero-dispersion wavelength just below 1000 nm to have, again, anomalous dispersion for the pump wavelength. At this pump wavelength, the generated supercontinuum spanned an ultrabroad-bandwidth of nearly 500 THz covering nearly the whole transparency window of Si3N4/SiO2 waveguides

Spontaneous four-wave mixing in silicon nitride waveguides for broadband coherent anti-Stokes Raman scattering spectroscopy

We present a light source for coherent anti-Stokes Raman scattering (CARS) based on broadband spontaneous fourwave mixing, with the potential to be further integrated. By using 7 mm long silicon nitride waveguides, which offer tight mode confinement and a high nonlinear refractive index coefficient, broadband signal and idler pulses were generated with 4 nJ of input pulse energy. In comparison to fiber-based experiments, the input energy and the waveguide length were reduced by two orders of magnitude, respectively. The idler and residual pump pulses were used for CARS measurements, enabling chemically selective and label-free spectroscopy over the entire fingerprint region, with an ultrafast fiber-based pump source at 1033 nm wavelength. The presented simple light source paves the path towards cost-effective, integrated lab-on-a-chip CARS applications