Minimizing the mass and power burden of a laser transceiver on a spacecraft for interplanetary optical communications
links drives requires operation in a “photon starved” regime. The relevant performance metric in the photon starved
regime is Photon Information Efficiency (PIE) with units of bits per photon. Measuring this performance at the detector
plane of an optical communications receiver, prior art has achieved performance levels around one bit per incident
photon using pulse position modulation (PPM). By combining a PPM modulator with greater than 75 dB extinction ratio
with a tungsten silicide (WSi) superconducting nanowire detector with greater than 83% detection efficiency we have
demonstrated an optical communications link at 13 bits per incident photon.
Studies have shown that stereo images improve surgeons' visuomotor tasks and therefore constructively affect the outcome of a minimally invasive surgery. Stereo images are captured by a stereo endoscope, which consists commonly of duplicate lens systems. However, stereo images can also be captured by a single lens system following a dual aperture scheme (DAS). DAS creates two spatially separated optical channels by placing a dual aperture plate in the limiting aperture of a single lens system. This paper describes efforts to miniaturize the DAS-based imaging system for use in minimally invasive surgery. To demonstrate feasibility, a prototype was fabricated using lens elements 3 mm in diameter and was tested for its stereo depth effect (SDE). The SDE of the prototype was then compared to a duplicate lens system that was constructed theoretically in the same diameter as the 3-mm prototype. The results show that the prototype yields 4/7 of the SDE of the theoretical model. However, the SDE of the prototype provides sufficient SDE, in a viewing range of 1 to 2.5 cm from the lens, for minimally invasive surgery.
Starting from an intuitive picture of photons bouncing back and forth within a slab of a uniform medium surrounded by photonic crystal (PC) layers, we develop a coupled mode formalism for the analysis of a PC waveguide. The modal solution in the core is given by counter-propagating waves while the cladding field is derived from a modified
coupled mode formalism. This coupled mode approach is used to analyze the dispersion and loss of the PC waveguide. Although coupled mode theory is usually applied to structures with a small index contrast perturbation, we find that our coupled mode formalism with an empirical coupling constant can be used to model a large index contrast PC waveguide. A single constant is used to analyze the dispersion and the loss of a two dimensional PC waveguide, a GaAs substrate with air holes. Our results are corroborated with a two dimensional finite-difference time-domain (FDTD) simulation and we find good quantitative agreement between the coupled mode theory
and the FDTD analysis.