Time-resolved optical spectrometer based on a monolithic array of high-precision TDCs and SPADs

Abstract

We present a compact time-resolved spectrometer suitable for optical spectroscopy from 400 nm to 1 µm wavelengths. The detector consists of a monolithic array of 16 high-precision Time-to-Digital Converters (TDC) and Single-Photon Avalanche Diodes (SPAD). The instrument has 10 ps resolution and reaches 70 ps (FWHM) timing precision over a 160 ns full-scale range with a Differential N on-Linearity (DNL) better than 1.5 % LSB. The core of the spectrometer is the application-specific integrated chip composed of 16 pixels with 250 µm pitch, containi ng a 20 µm diameter SPAD and an independent TDC each, fabricated in a 0.35 µm CMOS technology. In front of this array a monochromator is used to focus different wavelengths into different pixels. The spectro meter has been used for fluo rescence lifetime spectroscopy: 5 nm spectral resolution over an 80 nm bandwidth is achieved. Lifetime spectroscopy of Nile blue is demonstrated. Keywords: time-to-digital conversion (TDC), single-photon avalanche diode (SPAD) array, fluorescence lifetime spectroscopy, photon timing, time-correlated single-photon counting (TCSPC).