Events Calendar

EE-Electrophysics Seminar

Speaker: Alberto Tosi and Federica Villa, Politecnico di Milano - Dipartimento di Elettronica, Informazione e Bioingegneria

Talk Title: Single-Photon Avalanche Diodes

Abstract: Photon counting is the technique of choice for attaining the ultimate sensitivity in measurements of optical signals. Thanks to the Time-Correlated Single-Photon Counting (TCSPC) technique, it is possible to measure optical waveforms with high sensitivity on very fast (picosecond) time scale. Photon counting and timing was introduced and developed with PMTs, but it received new impulse from solid-state detectors, the Single-Photon Avalanche Diodes (SPAD).
SPADs exploit the avalanche phenomenon in a junction with an approach drastically different from the linear amplification of ordinary Avalanche PhotoDiodes (APD). In response to a single photon, a SPAD produces a standard current pulse with macroscopic size and fast rise, which marks the arrival time of the photon with precision of a few tens of picoseconds.
Nowadays, silicon SPADs (both single point and arrays) and InGaAs/InP SPADs are well developed and are commercially available, while new solutions are under development for attaining even better performance.
Silicon SPADs are employed in a wide range of emerging applications in chemistry, biology, medicine, material science, and physics. Commercially-available modules are regularly employed in many experimental setups and proved to be a reliable and high-performance solution for single-photon counting. Recently, gated mode operation of silicon SPADs with very fast rising edge (hundreds of ps) has been successfully exploited in order to widen the dynamic range and speed-up acquisition time in time-resolved measurements.
CMOS SPAD arrays based on smart pixels (that include counting and timing circuitry) are the basis for a single-photon counting cameras with very high frame rate and single-photon sensitivity. Such cameras can be used also for 3D acquisitions thanks to the capability to measure the distance from the objects in the scene.
Recently, remarkable effort has been devoted to the extension of single photon techniques to the near infrared (NIR) spectral range, developing SPADs in InGaAs/InP semiconductors for longer wavelengths, up to 1.6 um. The driving force comes from various application fields, such as: quantum key distribution (QKD) for cryptography in optical fiber communication systems, non-invasive measurement of signals in VLSI chips, eye-safe laser ranging (LIDAR), Raman spectroscopy, Optical Time-Domain Reflectometry (OTDR), PhotoDynamic Therapy (PDT), time-resolved spectroscopy and other fluorescence decay analysis.

Biography: Alberto Tosi was born in Borgomanero, Italy, in 1975. He received the Master's degree in electronics engineering and the Ph.D. degree in information technology engineering from Politecnico di Milano, Italy, in 2001 and 2005, respectively. He has been Associate Professor of Electronics at Politecnico di Milano since 2014. In 2004, he was a student with the IBM T.J. Watson Research Center, Yorktown Heights, NY, working on optical testing of CMOS circuits. Currently, he works on silicon, InGaAs/InP and Ge-on-Si single-photon avalanche diodes (SPADs). He develops single-point detectors, arrays of SPADs for 2D/3D applications, and related microelectronics and instrumentation.

Federica Villa received the B.Sc. degree in biomedical engineering and the M.Sc. and Ph.D. degrees in electronic engineering from the Politecnico di Milano, in 2008, 2010, and 2014, respectively. In 2010, she interned in the Biochemistry Department, University of California, Los Angeles. She is research associate at Politecnico di Milano and her current research interests include designing CMOS SPAD imagers for 2-D imaging of fluorescence decays and 3-D ranging through on-chip direct time-of-flight method, by means of in-pixel time-to-digital converters.

Host: EE-Electrophysics

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 132

Audiences: Everyone Is Invited

Contact: Marilyn Poplawski