20-channel Analog Boxcar Averager with 0.4ppm Resolution for Pump-Probe Optical Spectroscopy

This paper presents a multichannel CMOS boxcar averager specifically designed for broadband Pump-Probe spectroscopy, an advanced optical technique largely used in material science and biology to study ultrafast phenomena on the fs-ps timescale. The ASIC features low-noise switched capacitor integrators able to average up to 1023 pump-probe pulses with a repetition rate of 1MHz, enabling the achievement of an overall equivalent noise below 1 ppm relative to the mean optical power, as required by the most demanding pump-probe experiments. The chip operates with 20 channels in parallel for processing multiple wavelengths simultaneously, accelerating the acquisition of optical spectra. The combination of sub-ppm resolution and microsecond operation are well beyond the current state-of-the-art solutions for pump-probe spectroscopy, which typically operate at only a few kHz for similar resolution.