Master oscillator—power amplifier systems

An integrated master oscillator and power amplifier (MOPA) system comprising:

• a fiber laser oscillator for emitting laser light when pumped by pump light, comprising:
• a first double clad optical fiber (DCF) comprising:
• a core doped with active ions along at least a portion thereof,
• an inner cladding surrounding the core and defining a waveguide for the laser light generated in the core, and
• an outer cladding surrounding the inner cladding and defining a waveguide for the pump light;
• and,
• first and second fiber Bragg grating (FBG) reflectors integrally disposed at opposite ends of the first DCF so as to define an optical cavity of the fiber laser oscillator;
• a pump source optically coupled to the first DCF for emitting the pump light into the inner cladding of the first DCF;
• and,
• a first fiber optic power amplifier comprising a second DCF having a core doped with active ions for amplifying the laser light received from the fiber laser oscillator through the second FBG reflector, an inner cladding for guiding the laser radiation, and an outer cladding for guiding the pump radiation received from the fiber laser oscillator through the second FBG reflector;
• wherein:
• the first DCF of the fiber laser oscillator is optically coupled to the second DCF of the first fiber optic amplifier using one or more optical splices so as to form a monolithic fiber-optic structure,
• the inner cladding of the first DCF has a circular cross-section in order to enable the formation of low loss optical splices in the integrated MOPA structure;
• and,
• the inner cladding of the second double clad optical fiber has a shaped non-circular cross-section in order to enhance the absorption of the pump light in the doped core of the second DCF.