Passive all-optical signal processors that overcome the electronic bottleneck can potentially be the enabling components for the next-generation high-speed and lower power consumption systems. Here, we propose and experimentally demonstrate a CMOS-compatible waveguide and its application to the all-optical analog-to-digital converter (ADC) under the nonlinear spectral splitting and filtering scheme. As the key component of the proposed ADC, a 50 cm long high-index doped silica glass spiral waveguide is composed of a thin silicon-nanocrystal (Si-nc) layer embedded in the core center for enhanced nonlinearity. The device simultaneously possesses low loss (0.16 dB/cm at 1550 nm), large nonlinearity ($305{\mathrm{W}}^{-1}/\mathrm{km}$ at 1550 nm), and negligible nonlinear absorption. A 2-bit ADC basic unit is achieved when pumped by the proposed waveguide structure at the telecom band and without any additional amplification. Simulation results that are consistent with the experimental ones are also demonstrated, which further confirm the feasibility of the proposed scheme for larger quantization resolution. This demonstrated approach enables a fully monolithic solution for all-optical ADC in the future, which can digitize broadband optical signals directly at low power consumption. This has great potential on the applications of high-speed optical communications, networks, and signal processing systems.

We present the first demonstration of visible emission from highly doped silica glass micro-ring resonators (MRRs) through a third-harmonic generation (THG) nonlinear process. We obtain green light conversion efficiency of 2.7×10⁻⁵ W⁻² in a MRR with loaded Q-factor of 1.4×10⁶ pumped in the telecom band. A thermal nonlinear model is developed to account for the in-cavity power dependence of the resonance detuning. Using the extracted thermal nonlinear coefficients, the measured TH resonance shift is calibrated by subtracting the thermal nonlinear-induced phase mismatch to obtain the theoretical threefold wavelength relationship along with the measured cubic power relationship.

Based on the gradient force of evanescent waves in silica waveguides and add-drop micro-ring resonators, the optical trapping and manipulation of micro size particles is demonstrated in a self-locked scheme that maintains the on-resonance system even if there is a change in the ambient temperature or environment. The proposed configuration allows the trapping of particles in the high Q resonator without the need for a precise wavelength adjustment of the input signal. On the one hand, a silicon dioxide waveguide having a lower refractive index and relatively larger dimensions facilitates the coupling of the laser with a single-mode fiber. Furthermore, the experimental design of the self-locked scheme reduces the sensitivity of the ring to the environment. This combination can trap the micro size particles with a high stability while manipulating them with high accuracy.

This study presents the use of micro-ring resonator (MRR) devices to extract and enhance nonlinear signals. MRRs “trap” incoming light and, therefore, have been shown to achieve extremely high local intensities of light. Thus, they can be used to facilitate highly nonlinear optical signals that are usually weak in intensity and require high excitation power. By embedding materials that host nonlinear optical processes inside the MRR, we expect to observe an enhancement in the strength of the nonlinear optical signals. This concept is demonstrated here by extracting the Raman signature of graphene that is placed inside a MRR device. A highly doped silica MRR featuring an optical bus waveguide coupled to a ring tuned to near-infrared wavelengths is used. Raman signal with an excitation wavelength of 522 nm via third-harmonic generation inside the MRR is observed. The higher-order Raman signal of the embedded graphene is also observed at the 1597.6 nm excitation wavelength. This work demonstrates the feasibility of the MRR as a nonlinear signal enhancer using high-Q MRR device setups.

Optical trapping of micro size particles on an integrated optical ring resonator with self-locked scheme is demonstrated. The purposed scheme allows the ring resonator to stay on resonance regardless the frequency shift it encountered during the experiment. Trapping of polystyrene particles of sizes between 2 to 4 microns by the optical intensity on the ring resonator is reported.