Multichannel Hybrid Lock-In Amplifier for High-Resolution Broadband Raman Spectroscopy

Raman microscopy is a non-invasive and label-free spectroscopic technique with growing applications in the analysis of molecules and biological samples. Fast imaging requires the simultaneous acquisition of multiple wavelengths of the vibrational spectrum with high resolution (approx 10-100ppm). However, the design of a readout capable of combining high resolution and fast acquisition on many channels is still an open challenge. Here, we report a dual-mode, hybrid, multichannel instrument capable of acquiring a Raman spectrum in only 16μ s using analog differential lock-in amplifiers implemented in a custom CMOS chip. For slower measurements, a mixed analog-digital approach can be activated to enhance the signal-to-noise ratio by more than 20dB compared to a fully analog mode. The system can operate in parallel on 76 channels with signals modulated up to 10MHz and an optical power down to 4uW per channel.