Detector quantum efficiency

The noise in the experimental data can be estimated using the measured detector quantum efficiency (DQE) of the detector... 

The setup shown in Fig. 5.100 is also used for experiments based on parametric downconversion. A nonlinear crystal produces photon pairs the energy of which is equal to the energy of the pump photons. The measurement then delivers a correlation peak on a baseline of randomly detected background photons. The effect can be used for tests of quantum mechanics and a number of metrological applications [70]. The measurement of absolute detector quantum efficiencies by parametric downconversion [301, 356, 357, 358, 423, 536] is shown in Fig. 6.28, page 242. 

Fig. 6.28 Absolute measurement of the detector quantum efficiency by parametric down-...

A. Migdall, S. Castelletto, I.P. Degiovanni, M.L. Rastello, Intercomparison of a correlated-photon-based method to measure detector quantum efficiency, Appl. Opt. 41, 2914-2922 (2002)... 

A.L. Migdall, R.U. Datla, A. Sergienko, J.S. Orszak, Y.H. Shih, Absolute detector quantum-efficiency measurements using correlated photons, Metro-logia32, 479-483 (1995)... 

J.G. Rarity, K.D. Ridley, P.R. Tapster, Absolute measurement of detector quantum efficiency using parametric downconversion, Appl. Opt. 26, 4616-4619 (1987)... 

Here is the detector quantum efficiency. P, is the total received signal radiation power, and kT is the thermal excitation energy (k is Boltzmann s constant and T is the detector temperature). For photovoltaic and photo-conductive detectors, the input SNR is generally one-half that given in (7.186) [7.5, 14]. 

The detector quantum efficiency is typically 55-70% at 77K and increases with temperature. Figure 4 shows a quantum efficiency histogram for 99.95% of the detectors. The mean value is 67.5%. This is the effective quantum efficiency where the optically active area is about 90% of the unit cell. Efforts are underway to increase this quantum efficiency at 77K. Quantum efficiencies of >80% have been measured at 150K for SWIR detectors. 

The detector quantum efficiency has been measured at several astronomical wavelength bands. At L (roughly 3.45 to 4.30 micron), the mean detector quantum efficiency is 0.9. At M(4.15 to 5.40 microns) it is approximately 0.8. The detector fill factor is greater than expected, being about 80 percent. The dark current at 30K is shown in Figure 2. For a detailed report of dark current as a function of temperature, the reader is referred to Reference 1 which gives this data in detail for these detector arrays. 

Fig. 2. ETC has demonstrated continaoiis improvement in IBC detector quantum efficiency over time due to extensive design and process optimisation.

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