Optical apparatus, modules and devices

An apparatus comprising:

• a light guide, comprising at least a first layer and a second layer and an interface between the first layer and the second layer wherein;
• the first layer of the light guide comprises a first incoupler configured to in-couple one or more input beams of light of a first wavelength range into the first layer and a first outcoupler configured to out-couple the one or more input beams of light of the first wavelength range from the light guide;
• the second layer of the light guide comprises a second incoupler configured to in-couple one or more input beams of light of a second wavelength range into the second layer and a second outcoupler configured to out-couple the one or more input beams of light of the second wavelength range from the light guide;
• and
• the interface between the first layer and the second layer is arranged to retain light of the first wavelength range in the first layer and to retain light of the second wavelength range in the second layer and to allow light of a third wavelength range to pass through the interface and travel through both the first layer and the second layer.