As part of a research project to help establish standards for photon-counting detectors, NIST physicist Thomas Gerrits adjusts the laser beam hitting a detector. The squiggly overhead light helps researchers see the lab setup without disturbing the detectors, which are insensitive to blue light. Credit: J. Burrus/NIST

Counting photons needs standardization

The NIST team has just published methods for measuring the efficiency of five SPDs, including one made at NIST, as a prelude to offering an official calibration service.