Four-Channel Differential Lock-in Amplifiers With Autobalancing Network for Stimulated Raman Spectroscopy

Giuseppe Sciortino, Andrea Ragni, Alejandro De Cadena la, Marco Sampietro, Giulio Cerullo, Dario Polli, Giorgio Ferrari

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


We introduce a multi-channel integrated circuit for fast stimulated Raman scattering (SRS) microscopy on multiple simultaneous frequencies at a frame rate higher than 1 frame/s. The chip is a four-channel differential readout system, based on the lock-in technique. It is able to measure down to 10 ppm SRS signal, over a wide range of input optical powers (50-600 μW per channel), with a pixel dwell time of only 30 μs. Each acquisition channel includes two low-noise preamplifiers, two variable-gain amplifiers, a fully differential voltage subtractor, and a lock-in demodulator. The differential readout electronics rejects the power fluctuations of the laser, and it is automatically balanced by an analog feedback loop over ±30% input power mismatches. Due to the autobalancing network, the pixel dwell time is reduced by a factor up to 225 with a settling time of only 10 μs. The chip is fabricated in AMS 0.35 μm CMOS technology, and it is included in a combined electronics and optical system. Both single-pixel spectral measurements and multi-spectral imaging measurements are presented to validate the full SRS microscope.
Original languageEnglish (US)
Pages (from-to)1-1
Number of pages1
JournalIEEE Journal of Solid-State Circuits
StatePublished - 2021
Externally publishedYes


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