The steady advances in light-emitting diode (LED) technology have motivated the use of LEDs in optical wireless
communication (OWC) applications such as indoor local area networks (LANs) and communication between
mobile platforms (e.g., robots, vehicles). In contrast to traditional radio frequency (RF) wireless communication,
OWC utilizes electromagnetic spectrum that is largely unregulated and unrestricted. OWC communication may
be especially useful in RF-denied environments, in which RF communication may be prohibited or undesirable.
However, OWC does present some challenges, including the need to maintain alignment between potentially
moving nodes. We describe a novel system for link alignment that is composed of a hyperboloidal mirror,
camera, and gimbal. The experimental system is able to use the mirror and camera to detect an LED beacon of
a neighboring node and estimate its bearing (azimuth and elevation), point the gimbal towards the beacon, and
establish an optical link.
Free space optical communication may provide a viable adjunct to radio frequency (RF) technology for mobile communications, especially in “RF-denied” settings in which RF-based communication may be prohibited or impractical. These settings may include military tactical environments or settings which suffer from RF jamming or interference. Unlike many RF communication systems, point-to-point optical communications between mobile nodes typically require establishing and maintaining alignment, which requires each node to have awareness of the locations of neighboring nodes. We propose a method to create this situational awareness between nodes using purely optical means. This method uses a camera that is focused on a hyperboloidal mirror, thus providing a 360-degree view of the surrounding environment. The camera and mirror are used to detect light emitted from the beacon transmitters from neighboring nodes, with the location of the beacon image in the sensor plane of the camera yielding elevation and azimuth information of the beacon. The beacon transmitter itself is modulated, allowing it to be distinguished from the environment. In discussing our experimental realization of this system, we assess its performance.
Low power optical nonlinearities are a crucial requirement for data routing and next generation all-optical processing.
The majority of nonlinear optical devices to date exploit weak nonlinearities from a large ensemble of atomic systems,
resulting in both high power dissipation and a large device footprint. Quantum dots (QDs) coupled to photonic crystals
can provide significant reduction in both device size and power dissipation. The interaction between these two systems
creates extremely strong light-matter interaction owing to the tight optical confinement of photonic crystals and large oscillator strengths of QDs. Such interactions enable optical nonlinearities near the single photon level. In this work we investigate the nonlinear properties of QDs coupled to photonic crystals. We demonstrate large optical Stark shift with only 10 photons. We then propose and demonstrate a novel photonic circuit that can route light on a chip with extremely low optical powers.
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