A theoretical investigation of silicon-on-insulator nanometer slot waveguides for highly sensitive and compact chemical and biochemical integrated optical sensing is proposed. Slot guiding structures enabling high optical confinement in a low-index very small region are demonstrated to be very sensitive to either cover medium refractive index change or deposited receptor layer thickness increase. Modal and confinement properties of slot waveguides have been investigated, considering also the influence of fabrication tolerances. Waveguide sensitivity has been calculated and compared with that exhibited by other silicon nanometer guiding structures, such as rib or wire waveguides, or with experimental values in literature.

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An InP ring resonator with an experimentally demonstrated quality factor (Q) of the order of 10⁶ is reported for the first time. This Q value, typical for low loss technologies such as silica-on-silicon, is a record for the InP technology and improves the state-of-the-art of about one order of magnitude. The cavity has been designed aiming at the Q-factor maximization while keeping the resonance depth of about 8 dB. The device was fabricated using metal-organic vapour-phase-epitaxy, photolithography and reactive ion etching. It has been optically characterized and all its performance parameters have been estimated. InP waveguide loss low as 0.45 dB/cm has been measured, leading to a potential shot noise limited resolution of 10 °/h for a new angular velocity sensor.

Low-cost chip-scale optoelectronic gyroscopes having a resolution ≤ 10°/h and a good reliability also in harsh environments could have a strong impact on the medium/high performance gyro market, which is currently dominated by well-established bulk optical angular velocity sensors. The R&D activity aiming at the demonstration of those miniaturized sensors is crucial for aerospace/defense industry, and thus it is attracting an increasing research effort and notably funds. In this paper the recent technological advances on the compact optoelectronic gyroscopes with low weight and high energy saving are reviewed. Attention is paid to both the so-called gyroscope-on-a-chip, which is a novel sensor, at the infantile stage, whose optical components are monolithically integrated on a single indium phosphide chip, and to a new ultra-high Q ring resonator for gyro applications with a configuration including a 1D photonic crystal in the resonant path. The emerging field of the gyros based on passive ring cavities, which have already shown performance comparable with that of optical fiber gyros, is also discussed.