Surveillance and tracking of targets such as sensor fused warheads (SFWs) and unmanned aerial vehicles (UAVs) has
been a challenging task, especially in the presence of multiple targets moving at a relatively fast speed. Due to the
insufficient wavelength resolution, conventional radar technology may fail to resolve closely located targets or lack
spatial resolution for specific target identification. There is a need for the development of an innovative sensor that is
able to recognize and track closely related targets. To address this need, we have developed a target sensor that combines
vision and laser ranging technologies for the detection and tracking of multiple targets with wide viewing angle and high
spatial resolution. Using this sensor, regions-of-interest (ROIs) in the global scene are first selected, and then each ROI
is subsequently zoomed with vision technique to provide high spatial resolution for target recognition or identification.
Moreover, vision technique provides the azimuth and elevation angles of targets to a laser range finder for target distance
determination. As a result, continuous three-dimensional target tracking can be potentially achieved with the proposed
sensor. The developed sensor can be suitable for a wide variety of military and defense related applications. The design
and construction of a proof-of-concept target tracking sensor is described. Basic performance of the constructed target
tracking sensor including field-of-view, resolution, and target distance are presented. The potential military and defense
related applications of this technology are highlighted.
Microring resonators (MRs) are important photonic devices for large-port-count photonic circuits owing to their micrometer-scale device sizes. We describe the implementation of a 4×4 wavelength-reconfigurable photonic switch consisting of eight tunable MRs fabricated on a less expensive material platform: silicon on insulator. Wavelength reconfiguration is achieved through independent thermo-optic tuning of MRs with localized Nichrome microheaters fabricated on the same silicon-on-insulator substrate. A free spectral range of 18 nm and a 3-dB linewidth of 0.1 nm were observed for the fabricated MRs with a diameter of approximately 10 µm. The switch device shows negligible channel crosstalk (<0.01 nm) and moderate switching response time (<1 ms). The switch can potentially be scaled up to benefit the development of large-scale integrated photonics.
Micro-ring resonators have been traditionally fabricated using expensive III-V materials such as InP or GaAs. Device
tuning is typically to utilize the electro-optic effect of the III-V materials that usually leads to complex device layer
structures. As another tuning approach, thermo-optic tuning of micro-ring resonators is commonly achieved by heating
up the whole chip. In general, it is more challenging to achieve highly localized heating on a common chip for
independent tuning of multiple micro-ring resonators residing on the same substrate. To address these issues, we
describe the development of wavelength reconfigurable photonic switching using thermally tuned micro-ring resonators
fabricated on a low-cost silicon-on-insulator substrate. Independent tuning of multiple micro-ring resonators, spaced at
250 µm, is realized with highly localized micro heaters (50×50 μm<sup>2</sup> per heater area) fabricated on the same silicon
substrate. Owing to the large thermo-optic effect of silicon (Δn/ΔT=1.8×10<sup>-4</sup> K<sup>-1</sup>), 8 mA heating current is sufficient to
tune a micro-ring resonator with a 3-dB spectral line width of 0.1 nm by 2.5 nm while creating a minor peak shift of less
than 0.04 nm for an adjacent resonator. The switching response time is about 1 ms. A 1×4 wavelength reconfigurable
photonic switch device has been demonstrated. With a resonator diameter of approximately 10 μm (greater than 18 nm
in free spectral range of each micro-ring resonator), larger port-count switch matrix with wavelength reconfiguration on
a small device foot print is feasible for the development of large-scale integrated photonics.
An all-optical controllable 4×4 photonic switch matrix is described. The switching mechanism is based on the selection of the light absorption or amplification characteristic of erbium-doped optical fibers controlled with 980-nm pumping light. Using this approach, 4×4 photonic switching without overall insertion loss has been demonstrated with millisecond switching time and minimum extinction ratio of 24.2 dB. The all-fiber-based device is packaged by fiber fusion splicing with no moving parts, to ensure long-term device reliability. The fabricated 4×4 photonic switch matrix can be potentially scaled up to enhance the network capacity in optical communication systems where nonblocking large-scale optical cross-connect switching is required.
Many military and defense related applications require the use of large-scale photonic switch matrixes in order to increase the capacity for processing a large amount of information within a minimum period of time. Existing photonic switches relying on electro-optic effect or MEMS technology are limited in terms of switch scale size or switch reconfiguration rate. Moreover, these conventional photonic switches utilize analog electric signals for switch operation, making them extremely sensitive to electromagnetic interference that limits their military applications. To address these issues, we have developed a new photonic switch matrix using commercial erbium doped optical fiber and other commodity fiber optic components. Using this technology, all-optical controlled photonic switching operation can be realized. The optical amplification provided by erbium doped optical fibers further ensures the implementation of large-scale switch formation with low or no overall insertion loss. In addition, this new photonic switch is highly reliable and durable since it contains no moving parts without any related bearing or wearing issues, making it extremely suitable for military and defense related applications. In this presentation, the design and fabrication of a 4 × 4 erbium doped fiber based photonic switch matrix are described. Full performance characteristics of the fabricated switch matrix including switching speed and cross talk are given, and the potential military and defense related applications of this technology are highlighted.