We build spectrometers and microscopes that record individual photons from the visible into the shortwave infrared.

Interferometry. By sending emitted light through a Mach–Zehnder interferometer and timing each photon, we can record time-resolved spectra from the visible to the SWIR (decay-associated Fourier spectroscopy), and separate emitters by color without filters (spectrally-selective time-resolved emission through Fourier filtering, STEF). We also use photon-correlation Fourier spectroscopy to measure the spectral linewidths of single emitters.

Counting photons. With superconducting nanowire detectors, we have measured single nanocrystals that emit in the SWIR. Fluorescent optical cycling lets us measure the total photon budget of a molecule: how many photons it emits before it is lost. We have also shown where standard Stern–Volmer and FRET models fail to describe quenching in solution.