Patent ID: 8605762

Claim:
Laser apparatus comprising a reference source, a reference fibre, and at least one laser diode, wherein the reference fibre comprises a core having a refractive index n 1 and a first cladding having a refractive index n 2 , the first cladding is surrounded by a second cladding having a refractive index n 3 , the refractive index n 1 is greater than the refractive index n 2 , the refractive index n 2 is greater than the refractive index n 3 , the laser diode emits laser radiation that is guided through the first cladding of the reference fibre, the reference source emits reference radiation that has a predetermined wavelength, the reference radiation is guided through the core of the reference fibre to the laser diode, and the reference radiation that is guided through the core of the reference fibre to the laser diode has a power at the predetermined wavelength, which power is greater than an injection locking threshold of the laser diode thereby to injection lock the laser diode.