Radiative Heat Transfer Modeling

I am trying to create a transient model for an IF sensor and Iam not sure how to define the transmissivity and absorptivity ofeach material. For example, the spectral radiation will travelthrough a lens and into a thermal-pile. The lens should absorb someof the radiation but transmit about 80% of it down to thethermo-pile and surrounding enclosure.

Is there a way to define these properties in COSMOS?  Thanksfor the help!