title: Fill-factor improvement of Si CMOS single-photon avalanche diode detector arrays by integration of diffractive microlens arrays.
abstract: Single-photon avalanche diode (SPAD) detector arrays generally suffer from having a low fill-factor, in which the photo-sensitive area of each pixel is small compared to the overall area of the pixel. This paper describes the integration of different configurations of high efficiency diffractive optical microlens arrays onto a 32 × 32 SPAD array, fabricated using a 0.35 µm CMOS technology process. The characterization of SPAD arrays with integrated microlens arrays is reported over the spectral range of 500-900 nm, and a range of f-numbers from f/2 to f/22. We report an average concentration factor of 15 measured for the entire SPAD array with integrated microlens array. The integrated SPAD and microlens array demonstrated a very high uniformity in overall efficiency.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Intermite
authors.forename: Aongus
authors.initials: A
authors.lastname: McCarthy
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Warburton
authors.forename: Ximing
authors.initials: X
authors.lastname: Ren
authors.forename: Federica
authors.initials: F
authors.lastname: Villa
authors.forename: Rudi
authors.initials: R
authors.lastname: Lussana
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Waddie
authors.forename: Mohammad R
authors.initials: MR
authors.lastname: Taghizadeh
authors.forename: Alberto
authors.initials: A
authors.lastname: Tosi
authors.forename: Franco
authors.initials: F
authors.lastname: Zappa
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Buller