External cavity laser with high spectral purity output

A laser apparatus, comprising:

• (a) a gain medium having first and second facets, said gain medium emitting a light beam from said first facet along an optical path;
• (b) a wavelength selection element positioned in said optical path and configured to feed back light to said gain medium;
• (c) a reflector positioned in said optical path after said wavelength selection element, said reflector and said second facet of said gain medium defining an external laser cavity;
• and
• (d) a non-reciprocal pickoff positioned in said optical path before said wavelength selection element, said non-reciprocal pickoff being configured to pick off a portion of spectrally clean light in said external laser cavity returning from said reflector and output said portion of spectrally clean light along a path different from said optical path as spectrally clean laser output.

A method of laser operation, comprising:

• (a) emitting a light beam from a gain medium along an optical path;
• (b) positioning a wavelength selection element in said optical path;
• (c) positioning a non-reciprocal pickoff in said optical path between said gain medium and said wavelength selection element;
• (d) feeding light back to said gain medium by said wavelength selection element;
• and
• (e) picking off, by said non-reciprocal pickoff, a portion of light traveling said optical path from said wavelength selection element towards said gain medium, and outputting the portion having been picked off along a path different from the optical path as spectrally clean laser output.

A method for generating spectrally clean laser output, comprising:

• (a) emitting a light beam from a gain medium outward along an optical path;
• (b) allowing said outward light beam to interact with a tunable element;
• (c) returning a spectrally cleaned light beam along said optical path to said gain medium from said tunable element;
• and
• (d) non-reciprocally picking off a portion of said returning, spectrally cleaned light beam, at a location between said gain medium and said tunable element, from said optical path and directing said portion along an output path as spectrally clean laser output.

A laser apparatus, comprising

• (a) gain means for emitting a light beam along an optical path;
• (b) means for tuning said light beam positioned in said optical path;
• and
• (c) means for non-reciprocally picking off a portion of light returning from said tuning means to said gain means and directing the portion of light having been picked off along an output path different from said optical path as spectrally clean laser output, said non-reciprocally picking off means positioned in said optical path between said gain means and said tuning means.