Off-axis paraboloid mirror is a first surface mirror made of aluminum, 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 reflective design eliminates the phase delay and absorption loss introduced by transmission optical elements, so it is very suitable for femtosecond pulse lasers.