Modular 76-channel instrument for Broadband Raman Spectroscopy

Raman microscopy is a label-free and non-invasive technique to reveal the chemical compounds of a sample. However, standard Raman microscopes acquire a single frequency at a time, preventing fast imaging as many biological applications require. Here, we present the preliminary development of a multichannel CMOS-based readout for the simultaneous acquisition of 76 frequencies of the Raman spectrum using the broadband stimulated Raman scattering technique. The acquisition system employs the lock-in technique and a custom multichannel CMOS chip to enable a low-noise operation and a parallel architecture for fast imaging. An FPGA-based DSP chain reduces the low-frequency noise by exploiting a 2-step frequency down-conversion technique. The hardware design of the system based on a motherboard and several module PCBs to realize a highly space-optimized architecture is also presented. Particular emphasis is placed on the experimental results obtained with the 2-step frequency down-conversion technique by means of bench tests.