Correlated Photon Pairs Are Used To Measure Spectra of Remote Objects
Correlated bi-photon spectroscopy is a technique to measure the spectral characteristics of an object by monitoring the coincidence counts from correlated signal and idler photon pairs. The coincidence count rate from the two detectors is used to reproduce the spectral (transmission or reflection) function of the remote object. In this work, we report a novel technique for bi-photon spectroscopy by using a tunable up-conversion detector for local spectral analysis of the idler beam.
A number of interesting applications become possible with this type of spectral measurement technique. In the case of remote spectroscopy of objects that are inconveniently located for direct spectral measurements, only an intensity bucket type detector, rather than a resolving spectrometer, is needed to capture photons interacting with the object and the spectral measurements can be achieved by spectrally resolving the correlated photon beam located more accessibly. This technique may also provide a solution in a situation where security or privacy is required but difficult to ensure at the object site since neither the counts from the spectrally non-resolved signal, having interacted with the object, nor the spectrally resolved idler, having no interaction with the object, can individually provide any spectral information about the object being characterized – both are required to complete the spectral profile. For more information, please see the article "Frequency Correlated Bi-Photon Spectroscopy using a Tunable Up-Conversion Detector", Laser Phys. Lett. 10 (2013) 075201 at: http://iopscience.iop.org/1612-202X/10/7/075201
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