Quantum detectors sensitivity

Improvements in technology will shape developments in PL in the near future. PL will be essential for demonstrating the achievement of new low-dimensional quantum microstructures. Data collection will become easier and ter with the continuing development of advanced focusing holographic gratir, array and imaging detectors, sensitive near infiared detectors, and tunable laser sources. 

The fluorescence quantum yield of a compound may be determined by comparing the area under its fluorescence spectrum with the area under the fluorescence spectrum of a reference compound whose fluorescence quantum yield is known. The spectra of both compounds must be determined under the same conditions in very dilute solution using a spectrometer incorporating a corrected spectrum capability, in order to overcome any variation in detector sensitivity with wavelength. 

The ideal quantum detector response curve is a square wave, i.e., equally sensitive over the entire wavelength range of measurement. These types of detectors should be used for all measurements of incident intensity, UV and VIS, if a spec-troradiometer is not available. While spectrally blind they will at least give a truer reading of the total amount of radiation actually being received by the samples. Figure 7 shows the response curves of two of these detectors. 

According to theoretical and experimental results obtained recently a dc voltage can be induced by a switching of superconductor ring between states with different connectivity of wave function. This effect can be used for development of a quantum detector of noise with the ultimate sensitivity. Our experimental investigations confirm such possiUlity. 

In quantum detectors, IR radiation causes electrons to be excited to a higher energy level. In an n-type semiconductor, electrons in the valence band are unable to increase the conductivity. If IR radiation excites the electrons to the conduction band, they can act as current carriers. For good sensitivity, it is necessary to cool the detector. For certain detectors, such as PbS and PbSe, it may be sufficient to use a thermoelectric cooler to maintain their temperature just below ambient. Mercury cadmium telluride detectors must usually be maintained at liquid-nitrogen temperature (77 K), whereas others may require cooling to the temperature of liquid helium (4.2 K). 

Quantum efficiency (QE) - The sensitivity of a detector can be nearly perfect, with up to 99% of the photons detected at the wavelength for which the detector is optimized. 

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