normally open or normally closed OptoMos
The SFH 618A is turned on by LED current - the symbol of the device is a phototransistor and this can only be turned on by light. A good clue is that this device talks about CTR i.e. current transfer ratio i.e. more LED current means more collector current through the phototransistor.

The OptoMos device appears to be a solid state relay but designed so that light turns the device off.