Gold-plated off-axis paraboloid reflector is a first surface reflector made of aluminum-based gold film, and its reflecting surface is a part of the parent paraboloid. They can focus a collimating beam or a collimating scatter source without chromatic aberration, and their off-axis design can separate the focus from the light path in space.

The picture shows the processing of the off-axis parabolic mirror base by a single point lathe:

The reflective design eliminates the phase delay and absorption loss introduced by transmission optical elements, so it is very suitable for femtosecond pulse lasers.