Electron multiplying CCDs have revolutionized the world of low light imaging by bringing improved detection limits along with high readout rates; however, it remains to be seen whether they offer any benefits to the world of spectroscopy. Here we review the performance of current CCD and EMCCD detectors and compare their performance for low light level spectroscopy applications. In particular, we look at the detection limits of both technologies for real applications and examine all the parameters that affect these limits in a practical situation. We compare sensitivities, dark signal, noise factors and readout noise with the latter two as the ultimate limitations for detection. We also look at emerging new technology for low light spectroscopy applications which optimizes the parameters discussed without the disadvantages of the current technologies.
Theoretical signal to noise data comparing conventional CCD and EMCCD technologies is presented and discussed. Experimental signal to noise comparisons are made for Raman spectra obtained using both conventional and electron multiplying CCDs in conjunction with a confocal Raman microscope. It is concluded that traditional CCDs have a superior detection limit and equal sensitivity to that of EMCCDs and are far superior for high quality quantitative data measurements.