Trouble in store.

As boomers age, food retailers are faced with weighty questions on what customers want, and whether it's healthy or not.

Older and wealthier.

The number of elder Americans with six-figure incomes will rise dramatically over the next five years--a boon to providers of health-care services, the travel industry and makers of luxury products.

Single-photon detection beyond 1 µm: performance of commercially available germanium photodiodes.

Germanium avalanche photodiodes (APD's) working biased above the breakdown voltage detect single optical photons in the near-infrared wavelength range. We give guidelines for the selection of devices suitable for photon-counting applications among the commercial samples, and we discuss in detail how the devices should be operated to achieve the best performance, both in terms of noise-equivalent power (NEP) and the timing-equivalent bandwidth. We introduce the driving electronics and we show that, in the measurements of fast optical signals, the adoption of single-photon techniques is very favorable, notwithstanding that presently available photodiodes are not designed for this purpose.

Subnanosecond single-photon timing with commercially available germanium photodiodes.

We demonstrate that commercially available germanium avalanche photodiodes can achieve single-photon sensitivity and subnanosecond time resolution at 77 K. Experiments show that carrier trapping phenomena give the main contribution to the detector noise. Therefore technological efforts will be welcome to overcome the present limitations that are due to the material quality.