Superconducting Nanowire Single-Photon Detectors

Joint Meeting with Boston Chapter, LEOS

 I will discuss our ongoing work at MIT on single-photon detectors based on superconducting NbN nanowires. These nanometer-scale devices exploit the ultrafast nonequilibrium electronic photoresponse in ultrathin films of the highly disordered superconductor NbN to produce a photon counter of unprecedented speed and sensitivity. With better than 30 ps timing resolution, ~few ns reset time after a detection, and high detection efficiency (>85% demonstrated at 1550 nm), these devices show promise as an enabling technology in a number of areas, such as high data rate interplanetary optical communications, spectroscopy of ultrafast quantum phenomena in biological and solid-state physics, quantum key distribution and quantum computation, astrophysics, laser radar, and high-speed noninvasive digital circuit testing.

Rudiments and intricacies of cost-based tolerancing

Tolerancing is a lynchpin for the success of all optical hardware projects. In its broadest sense, tolerancing includes assessing robustness, guiding decision-making throughout the product development life-cycle, and assigning error bounds to construction parameters. Overall, the primary goal of tolerancing is twofold: ensure the system(s) will function properly (or have sufficient yield) and minimize cost. Traditional methods of tolerancing have quantitatively dealt with the former, with treatment of cost being qualitative or implicitly incorporated. Consequently, quantitative cost analysis is the de facto “holy grail” of optical tolerancing.

In this presentation requisite parts of “cost-based tolerancing” will be discussed, running the gamut from fundamental pieces through advanced methodologies. Different facets and phases will be highlighted from design for manufacturing to drive robust design through methods of tolerance assignment and analysis. The context will be with respect to traditional lens design, although the methodology has broad application for general electro-optical systems in addition to diverse non-optical fields. Attendees should garner the state of this subfield in optical design, as well as gain an appreciation for the rudiments and intricacies that aid in taking cost more explicitly into account. They may even find that tolerancing can be fun, but the presenter does not want to overstate any promises!

Note: New Meeting Location
Rebeccas Cafe in Newton with access to MBTA Green Line

Correcting Higher Order Aberrations In The Human Eye

The human cornea accounts for approximately two-thirds of the total refractive power of the human eye.  Disorders that distort its shape and smoothness induce irregular astigmatism and higher order aberrations that are uncorrectable with spectacles. Because the refractive index of tear and cornea are similar, a rigid contact lens masks most (9/10) of the refractive power of the corneal surface, including irregular astigmatism. Yet, significant residual HOAs that degrade visual performance remain a significant issue in eyes with certain common corneal disease. The 501(3) nonprofit Boston Foundation for Sight fits these eyes with a unique hard contact lens that is rotationally stable and immobile on blinking. These features make it an excellent vehicle for correcting eye-specific residual higher order aberrations.  The Foundation in collaboration with Geunyoung Yoon, Associate Professor at the Institute of Optics and Center for Visual Science at the Center for Visual Science, University of Rochester, is working to customize the optics of the BOS-P to correct eye-specific residual higher order aberrations based on mapping Zernike polynomials and generating correcting front surface optics perturbations.