Charge and temporal characterisation of silicon sensors using a two-photon absorption laser

TL;DR

This paper introduces a new two-photon absorption laser setup at Nikhef for detailed charge and time characterization of silicon sensors, demonstrating uniform charge collection and high temporal resolution capabilities.

Contribution

The study presents the first measurements using a TPA setup for silicon sensors, providing detailed charge and time resolution data and imaging sensor features directly.

Findings

TPA spot radius of 0.975 μm and length of 23.8 μm in silicon

Trigger time resolution up to 30.4 ps

Single pixel time resolution of 600 ps (electron) and 560 ps (hole)

Abstract

First measurements are presented from a newly commissioned two-photon absorption (TPA) setup at Nikhef. The characterisation of the various components of the system is discussed. Two planar silicon sensors, one being electron collecting and one hole collecting, are characterised with detailed measurements of the charge collection and time resolution. The TPA spot is determined to have a radius of 0.975(11) $\mu\text{m}$ and length of 23.8 $\mu\text{m}$ in silicon. The trigger time resolution of the system is shown to be maximally 30.4 ps. For both sensors, uniform charge collection is observed over the pixels, and the pixel side metallisation is imaged directly using the TPA technique. The best time resolution for a single pixel is found to be 600 ps and 560 ps for the electron and hole collecting sensors respectively, and is dominated by ASIC contributions. Further scans at different depths in the sensor and positions within the pixels have been performed and show a uniform response. It is concluded that the TPA setup is a powerful tool to investigate the charge collection and temporal properties of silicon sensors.