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We investigate the operation of a quantum dot, optically gated, field-effect transistor as a photon detector. The detector exhibits time-gated, single-shot, single-photon sensitivity, a linear response, and an internal quantum efficiency of up to (68±18)% at 4K. Given the noise of the detector system, they find that a particular discriminator level can be chosen so the device operates with an internal quantum efficiency of (53±11)% and dark counts of 0.003 counts per shot.

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Single-photon detection using a quantum dot optically gated field-effect transistor with high internal quantum efficiency Appl. Phys. Lett. 89, 253505 (2006); 10.1063/1.2403907 Detection of single photons using a field-effect transistor gated by a layer of quantum dotsWe describe the design of the epitaxial layers for an efficient, photon-number-determining detector that utilizes a layer of self-assembled quantum dots as an optically addressable gate in a field-effect transistor. Our design features a dedicated absorption layer where photoexcited holes are produced and directed with tailored electric fields to the quantum dot layer. A barrier layer ensures that the quantum dot layer is located at a two-dimensional potential minimum of the structure for the efficient collection of holes. Using quantum dots as charge traps allows us to contain the photoexcited holes in a well-defined plane. We derive an equation for a uniform size of the photon signal based on this precise geometry. Finally, we show corroborating data with well-resolved signals corresponding to different numbers of photons.

We observed the spectrum of neutral krypton (Kr I) in its naturally occurring isotopic mixture as emitted by a microwave-excited electrodeless discharge lamp with the National Institute of Standards and Technology (NIST) 2 m Fourier transform spectrometer (FTS). The spectra cover the region from 6699 to 12 200 Å with a resolution of 0.01 cm −1 and the region from 9000 to 47 782 Å with a resolution of 0.007 cm −1 . We present a line list that includes more than 630 classified lines, about 290 newly observed, and provides an accurate and comprehensive description of the infrared spectrum. The response of the FTS was characterized by using a radiometrically calibrated tungsten strip lamp to obtain relative intensities accurate to 10% or better over the entire spectral range for lines with good signal-to-noise ratio (SNR). All eight levels of the 4s 2 4 p 5 ( 2 P 3/2 )6g configuration have been located as well as one previously unknown level of the 4s 2 4 p 5 ( 2 P 3/2 )6 f configuration. Our new data have been combined with previous precise measurements to determine improved values for 64 even and 77 odd parity levels of Kr I.