An irradiation device comprising: a fluid treatment chamber having first and second opposing sides (106, 108) configured to receive a biological fluid container therebetween; and at least one light source (110, 112) disposed adjacent at least one of the first and second sides (106, 108) of the fluid treatment chamber, characterized in that: the at least one light source (110, 112) comprising: a light guide (114, 116) having a front planar surface (122, 124) that defines in part the at least one of the first and second sides (106, 108) of the fluid treatment chamber, and at least one light emitting diode (118, 120) disposed at an edge (126, 128) of the light guide (114, 116) outside the fluid treatment chamber and configured to direct light into the light guide (114, 116), the light guide (114, 116) having a back surface (130, 132) opposite the front planar surface (122, 124), the back surface (130, 132) with a plurality of reflectors (134, 136) that depend into the light guide (114, 116) in the direction of the front surface (122, 124), the plurality of reflectors (134, 136) configured to direct at least part of the light traveling along the light guide (114, 116) out of the light guide (114, 116) through the front surface (122, 124). a fluid treatment chamber having first and second opposing sides (106, 108) configured to receive a biological fluid container therebetween; and at least one light source (110, 112) disposed adjacent at least one of the first and second sides (106, 108) of the fluid treatment chamber, characterized in that: the at least one light source (110, 112) comprising: a light guide (114, 116) having a front planar surface (122, 124) that defines in part the at least one of the first and second sides (106, 108) of the fluid treatment chamber, and at least one light emitting diode (118, 120) disposed at an edge (126, 128) of the light guide (114, 116) outside the fluid treatment chamber and configured to direct light into the light guide (114, 116), the light guide (114, 116) having a back surface (130, 132) opposite the front planar surface (122, 124), the back surface (130, 132) with a plurality of reflectors (134, 136) that depend into the light guide (114, 116) in the direction of the front surface (122, 124), the plurality of reflectors (134, 136) configured to direct at least part of the light traveling along the light guide (114, 116) out of the light guide (114, 116) through the front surface (122, 124). a light guide (114, 116) having a front planar surface (122, 124) that defines in part the at least one of the first and second sides (106, 108) of the fluid treatment chamber, and at least one light emitting diode (118, 120) disposed at an edge (126, 128) of the light guide (114, 116) outside the fluid treatment chamber and configured to direct light into the light guide (114, 116), the light guide (114, 116) having a back surface (130, 132) opposite the front planar surface (122, 124), the back surface (130, 132) with a plurality of reflectors (134, 136) that depend into the light guide (114, 116) in the direction of the front surface (122, 124), the plurality of reflectors (134, 136) configured to direct at least part of the light traveling along the light guide (114, 116) out of the light guide (114, 116) through the front surface (122, 124).