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We demonstrate a suspended germanium waveguide platform with a propagation loss of 5.3 dB/cm at a wavelength of 7.7 µm, with potential applications in free-space optical communications and absorption sensing. Furthermore, our simulations show low-loss propagation up to ~15-µm wavelength., 2021 IEEE 17th International Conference on Group IV Photonics (GFP), December 7-10, 2021, Malaga, Spain

We demonstrate devices and architectures enabling applications such as light detection and ranging (LiDAR) and optical switches, including dispersive optical phased array (OPA) architectures, a hybrid silicon nitride - lithium niobate on insulator (SiN - LNOI) optical phase modulator, and scalable architectures for optical switches., 2021 IEEE 17th International Conference on Group IV Photonics (GFP), December 7-10, 2021, Malaga, Spain

We propose a 90° hybrid-based monolithically integrated coherent receiver suitable for colorless operation in the complete C- and L-band (1530-1625 nm). In-phase and quadrature (IQ) signal components are obtained from a calibrated analog IQ recovery circuit, which adequately combines all the four photocurrents at the output of the 90° hybrid nearly cancelling the baseband interference from the self-beating of adjacent wavelength division multiplexing channels. We numerically demonstrate that the proposed downconverter supports colorless reception of 128 channels with 16-quadrature amplitude modulation at 112 Gbps in the C+L band. Aside from this, this receiver exhibits a noticeable dynamic range, thereby not requiring a variable optical attenuator on the signal path, and it is pretty robust under realistic fabrication errors of the optoelectronic chip.

The silicon photonic wire evanescent field (PWEF) sensor platform offers the advantages of small sensor size, high levels of function integration, and low cost manufacturing that comes with the use of established semiconductor fabrication processes. The technology should be fully compatible with existing infrastructure in molecular analysis and research and the manufactured sensor array chip cost should be low enough that the chips can be considered disposable. Furthermore, since many applications require simultaneous monitoring of many different simultaneous binding reactions, the possibility of integrating tens or even hundreds of independent molecular sensors on a single disposable sensor chip is very compelling. We present an overview of our multiplexed photonic wire sensor chip and a reader instrument that allows up to 128 independent binding reactions to be monitored simultaneously. A complete photonic wire molecular biosensor microarray chip architecture and supporting instrumentation is discussed. This microarray system is used to demonstrate a multiplexed assay for serotyping E. coli bacteria based on polyclonal antibody probe molecules. A coherent detection scheme that enables direct read-out of the optical phase and an order of magnitude enhancement of sensitivity compared to conventional detection is also discussed. Finally, we present advances in Fourier-transform interferometer arrays for spectroscopic sensing. A planar waveguide Fourier-transform spectrometer with densely arrayed Mach-Zehnder interferometers is presented. Subwavelength gratings are used to produce an optical path difference without waveguide bends. The fabricated device comprises of an array of 32 Mach-Zehnder interferometers, which produce a spatial interferogram without any moving parts, yielding a spectral resolution of 50 pm and a free-spectral range of 0.78 nm. As a result of similar propagation losses in subwavelength grating waveguides and conventional strip waveguides, loss imbalance is minimized and high interferometric extinction ratio of -25 to -30 dB is obtained. Furthermore, phase and amplitude errors arising from normal fabrication variation are compensated by the spectral retrieval process using calibration measurements., 2014 16th International Conference on Transparent Optical Networks (ICTON), 6-10 July 2014, Graz, Austria

A new technique based on the two-dimensional Fourier transform is presented and applied to the study of nonlinear wave propagation phenomena in one-dimensional, finite, nonlinear transmission lines. The technique permits determining the effects of nonlinearities and boundary conditions on the Fourier transform and identifying incident and reflected waves and solitons which may propagate through the transmission line at constant speed. The effects of windows on the Fourier transform are also assessed in both linear and nonlinear transmission line models. >

In designing microwave circuits the use of computer aided design (CAD) techniques is invaluable. Continuation methods using different types of predictors are implemented and their performance is evaluated in two nonlinear circuits (a lumped element one and a microstrip one) analysed by the harmonic balance technique. The comparison is carried out taking into account the error in the predictors and the number of iteration the solver needs to reach the next solution point. In doing so, the possibility of making the predictor adaptive is discussed.

A harmonic balance technique is used to study the formation and interaction of solitons in discrete, lossless, nonlinear transmission lines as a function of the number of harmonics, number of LC-cells, and pulse height and width at the generator. It is shown that the number of harmonics required to accurately determine the soliton formation and propagation increases as the generator's fundamental frequency is decreased, and that about 500 LC-cells are needed to observe the propagation and interaction of solitons. It is also shown that, for the calculations presented, the transmission line is almost perfectly adapted. A Taylor series expansion was used to determine the continuous analog of the discrete transmission line presented. >

We report our advances in development of subwavelength engineered metamaterial structures in silicon waveguides, specifically high-efficiency fiber-chip couplers, ultra-broadband surface grating couplers and nanophotonic beam splitters, evanescent field waveguide sensors and on-chip Fourier-transform spectrometers.

A harmonic balance technique is applied to the analysis of nonlinear transmission lines with periodic excitation. Using this technique, the formation of Shockwaves and solitons in such structures is simulated.

We propose a novel silicon photonics add-drop filter exploiting Bragg gratings to implement a mirror-cavity structure with an aperiodic response. Narrow-band single-channel- extraction over a wavelength range well beyond the C-band is demonstrated