A laser beam ignition system for an internal combustion engine is provided. The laser beam ignition system comprises a laser configured to generate a laser beam, and a beam steering unit comprising a lens and a prism both configured to cooperatively transmit the laser beam to focus on an oxygenated fuel mixture supplied into a combustion chamber of the internal combustion engine. A beam steering unit and a method for igniting a fuel mixture in an internal combustion engine are also presented.