The design of a four-quadrant detector for the semi-active laser seeker on the guided gun-launched projectile was studied. Several key parameters of the four-quadrant detector, including the photosensitive area, spectral responsivity, respond speed and noise equivalent power were discussed in the application. A bigger photosensitive area will be benefited to get a larger detection range, however, it will decrease the response speed and increase the positioning time. The spectral responsivity of the detector was chosen to be highly sensitive with the 1064nm wavelength laser, and its responsivities for the other wavelengths were relatively low. As the operation time is short, the response speed of the detector need to be increased as higher as possible, and many influencing factors were compromised in the design. A lower number of NEP was optimized for the better detecting capability. The orientation detection circuit and related positioning algorithm was developed to determine the yaw angle and pitch angle between the projectile and the target. Then the relative position errors, including the lateral and vertical deviation, were obtained from the four-quadrant detector. The influence of the size of facula with respect to the detecting sensitivity and effective measure ranges of the four-quadrant detector were analyzed. Finally, the sizes both of the facula and the four-quadrant detector were designed to ensure the most efficient use of the detecting sensitivity and effective measure ranges of the detector.
In this paper, we report our recent progress in silicon-nitride-based optofluidic label-free biosensors using a surfacefunctionalized coupled-resonator optical waveguide (CROW) in the visible wavelengths. The working principle is based on far-field imaging of the CROW mode-field intensity distributions at a fixed probe wavelength. The imaged pattern variation reflects real-time analyte-binding information on the CROW surfaces. Our surface-functionalized 16- microring CROW reveals six eigenstates with distinctive mode-field intensity distributions. Our proof-of-concept sensing experiment at an arbitrarily chosen probe wavelength within the CROW transmission band shows a detection of streptavidin concentration down to 40 ng/ml.
Silicon photonics using waveguide- and microresonator-based devices are finding technologically important applications
in the field of optofluidics. By integrating microfluidic channels on top of silicon-based planar devices, silicon photonic
devices can function as on-chip optical tweezers to manipulate micro/nanoparticles. In this paper, we will highlight our
recent progress in the field of optofluidics using silicon nitride devices for on-chip optical manipulation including the
experimental demonstrations of: (i) planar optical tweezers using waveguide junctions with and without tapers, (ii)
microparticle buffering and dropping on microring resonator devices upon linearly polarized light and (iii) microparticle
trapping and assembling on circular microdisk resonators. Such devices can function as basic building blocks for
“optical tweezers circuits” in lab-on-chip applications.