Wavelength sliced self-seeded pulsed laser

A laser to produce pulses of light having predetermined spectral shapes, said laser comprising:

• an optical waveguide formed from optical fiber, wherein radiation can propagate along a first direction and a second direction opposed to the first direction;
• a laser diode optical pump source, coupled to the optical waveguide to inject pumping radiation to propagate therein;
• a first length of erbium-doped fiber in said optical waveguide wherein the pumping radiation induces a population inversion, the first length of erbium-doped fiber continuously generating seed radiation by amplified spontaneous emission, the seed radiation propagating along the first direction in the optical waveguide and being composed of a multitude of photons each having a wavelength comprised in a bandwidth of wavelengths, said first length of erbium-doped fiber acting as an amplification medium for radiation propagating therein along the second direction;
• reflecting means in said optical waveguide comprising at least one photoinduced Bragg grating, for selectively reflecting the seed radiation to generate a reflected beam, said reflected beam comprising photons of different wavelengths propagating at different times in the optical waveguide along the second direction;
• adjustable modulation means situated between the first length of erbium-doped fiber and the reflecting means in said optical waveguide, the modulation means allowing radiation to pass therethrough only at predetermined times, the adjustable modulation means thereby pulsing the seed radiation and selecting photons from the reflected beam according to their wavelength to produce the pulses of light having the predetermined spectral shapes;
• and
• a second length of erbium-doped fiber in said optical waveguide situated between the adjustable modulation means and the reflecting means, a pump by-pass allowing the pumping radiation to bypass the adjustable modulation means and propagate in said second length of erbium doped fiber to induce a population inversion therein, the second length of erbium-doped fiber acting as an amplification medium for radiation propagating therein along the first and second directions.

A method to produce pulses of laser light having predetermined spectral shapes, said method comprising steps of:

• a) injecting pumping radiation to propagate into an optical waveguide;
• b) inducing a population inversion in a gain medium in said optical waveguide, said population inversion stimulating a continuous generation of seed radiation by amplified spontaneous emission, the seed radiation propagating along a first direction in the optical waveguide and being composed of a multitude of photons each having a wavelength comprised in a bandwidth of wavelengths;
• c) modulating the seed radiation by allowing said seed radiation to pass through modulation means in the optical waveguide only at predetermined times, thereby generating pulses of seed radiation;
• d) selectively reflecting the pulses of seed radiation on reflecting means in the optical waveguide to generate reflected pulses, each of said reflected pulses comprising photons of different wavelengths propagating at different times in the optical waveguide along a second direction opposed to the first direction;
• e) selecting photons from the photons of different wavelengths comprised in each reflected pulse by opening the modulation means only at predetermined times, and therefore allowing only parts of said reflected pulse to pass therethrough, thereby generating pulses having the predetermined spectral shapes;
• and
• f) amplifying said pulses having the predetermined spectral shapes by propagation along the second direction through the gain medium.