Lock-In Based Differential Front-End For Raman Spectroscopy Applications

The intrinsic sensitivity limit of Stimulated Raman Spectroscopy (SRS) is given by the shot noise of the optical stimulation. However, it is seldom reached due to the electronic noise of the front-end amplifier and the intensity fluctuations of the laser source. Here, we present and test a low-noise pseudo- differential amplifier, for Raman spectroscopy applications, able to compensate the common-mode fluctuations given by the laser and to reach a sensitivity better than 10 ppm thanks to the lock-in technique.