Random number generator comprising a vertical cavity surface emitting laser

A method for generating random numbers using a random number generator comprising:

• providing a vertical cavity surface emitting laser (VCSEL), a mode separator and a photodetector, a power source that drives the VCSEL in direct modulation mode;
• driving the VCSEL via the power source such that the VCSEL emits, from an emitting section into space outside of a VCSEL cavity, laser light with two distinct laser modes of random relative strength that propagates in a propagation direction away from the emitting section;
• separating the laser light via the mode separator such that the mode separator transmits one of the two distinct laser modes to the photodetector;
• and
• obtaining, from the photodetector, a signal depending on an intensity of the laser light received at the photodetector via the mode separator from the VCSEL.