A device (700; 800), comprising: a first sensor portion including a first photodetector (762a, 762b; 822a, 862b); a second sensor portion including a second photodetector (714a, 714b; 814a, 814b); and a combined metal-interconnect layer (718, 719; 818, 819) between the first photodetector (762a, 762b; 822a, 862b) and the second photodetector (714a, 714b; 814a, 814b), the combined metal-interconnect layer (718, 719; 818, 819) forming a light pipe (706a, 716a; 706b, 716b; 806a, 816a; 806b, 816b) including a channel formed by a plurality of layers, the plurality of layers including: a first layer (402a; 502a; 602a); and a second layer spaced apart from the first layer along an axis of the channel, and characterised in that the first layer (402a; 502a; 602a) includes a first plurality of metal portions including a first metal portion (404a; 504a; 604a) of an optical metal trace and a second metal portion (404b; 504b; 604b) of a metal interconnect trace, wherein the optical metal trace includes a plurality of edges including a first edge (406a; 506a; 606a) at one end of the optical metal trace and a second edge (406b; 506b; 606b) at the opposite end of the optical metal trace and the metal interconnect trace includes a plurality of edges including a third edge (408a; 508a; 608a) at one end of the metal interconnect trace and a fourth edge (408b; 508b; 608b) at the opposite end of the metal interconnect trace, the first and second metal portions (404a, 404b; 504a, 504b; 604a, 604b) being disposed on the same plane and defining a perimeter that extends about the axis of the channel. a first sensor portion including a first photodetector (762a, 762b; 822a, 862b); a second sensor portion including a second photodetector (714a, 714b; 814a, 814b); and a combined metal-interconnect layer (718, 719; 818, 819) between the first photodetector (762a, 762b; 822a, 862b) and the second photodetector (714a, 714b; 814a, 814b), the combined metal-interconnect layer (718, 719; 818, 819) forming a light pipe (706a, 716a; 706b, 716b; 806a, 816a; 806b, 816b) including a channel formed by a plurality of layers, the plurality of layers including: a first layer (402a; 502a; 602a); and a second layer spaced apart from the first layer along an axis of the channel, a first layer (402a; 502a; 602a); and a second layer spaced apart from the first layer along an axis of the channel, and characterised in that the first layer (402a; 502a; 602a) includes a first plurality of metal portions including a first metal portion (404a; 504a; 604a) of an optical metal trace and a second metal portion (404b; 504b; 604b) of a metal interconnect trace, wherein the optical metal trace includes a plurality of edges including a first edge (406a; 506a; 606a) at one end of the optical metal trace and a second edge (406b; 506b; 606b) at the opposite end of the optical metal trace and the metal interconnect trace includes a plurality of edges including a third edge (408a; 508a; 608a) at one end of the metal interconnect trace and a fourth edge (408b; 508b; 608b) at the opposite end of the metal interconnect trace, the first and second metal portions (404a, 404b; 504a, 504b; 604a, 604b) being disposed on the same plane and defining a perimeter that extends about the axis of the channel.