Optical Concentrator


CEA-LETI is involved in the fabrication of optical concentrators that will be placed between the scintillator crystal and the CMOS sensor, to recover the SPAD fill factor loss. The concentrators under development were fabricated using nano imprint lithography technique on 8’’ silicon/quartz wafers.



Several optical concentrator geometries have been studied, using focusing refractive lenses, or reflecting light guides.


  1. The first studied structure was hemispherical polymeric microlenses to focus the emitted light on the SPADs active area.
  2. The second studied structure is pyramidal light guiding optical concentrator. The basis of the pyramid will be on the scintillator side and the tip, or alternatively flattened tip will be on the SPAD active area.


Scintillator - sensor assembly


A dedicated bonding workflow is under development at CEA-LETI to assemble the LYSO slab to the chip tile, without bubbles. This process is first developed using dummy tiles provide by partner STmicroelectronics and a quartz slab.



Single-photon sensor

Under construction



 Will be updated after Nuclear Science Symposium 2012


Simulator chain from photon to communication

 Will be updated after Nuclear Science Symposium 2012