This can make it simple to collimate the output beam with an easy lens, which doesn't have to have a incredibly high numerical aperture.VCSELs for wavelengths from 650 nm to 1300 nm are usually based upon gallium arsenide (GaAs) wafers with DBRs fashioned from GaAs and aluminium gallium arsenide (AlxGa(1?x)As). The GaAs–AlGaAs program is favore