The authors suggest black foamboard with cloth and a laser safety curtain is sufficient. Better safe than sorry though.

  To prevent light from reaching the detector from sources other than light 
  transmitted through the head, the experiment was performed in a light-tight 
  enclosure that surrounded the head. The enclosure was built using black 
  foamboard and covered with two layers of black cloth and a laser safety 
  curtain. 

https://doi.org/10.1117/1.NPh.12.2.025014