Laser source with reduced linewidth
In the field of narrow linewidth laser sources and a laser device that comprises a laser source and a waveguide of determined refractive index with which it is coupled, a waveguide is single-mode and includes at least four reflectors in the form of trenches etched into the waveguide and irregularly distributed along the waveguide, the distance separating two neighbouring reflectors being above 1 μm, and the waveguide and the laser source have respective lengths such that the length of waveguide over which the reflectors are located is greater than the length of the laser source itself.
1. A laser device comprising:
a laser source;
a waveguide of determined refractive index; and
a coupling device,
wherein the waveguide is coupled to the laser source by the coupling device,
wherein the waveguide is single-mode and includes at least four reflectors in the form of trenches etched into the waveguide and irregularly distributed along the waveguide, a distance d separating each pair of neighbouring reflectors defined by the at least four reflectors being 1 μm<d<L−3 μm, L being a length of the waveguide, and
wherein the at least four reflectors are positioned over a length of the waveguide that is greater than a length of the laser source, and
wherein a degree of power reflection of each reflector is between 0.001% and 1%.
2. The laser device according to claim 1 , wherein the laser source and the waveguide form a monolithic assembly.
3. The laser device according to claim 2 , wherein the laser source is semiconductor-based.
4. The laser device according to claim 1 , wherein the reflectors are etched or obtained by insolation of the waveguide.
5. The laser device according to claim 4 , wherein the coupling device is a connector, the laser source and the waveguide being respectively placed in two mutually separate housings.
6. The laser device according to claim 4 , wherein the coupling device is a lens, the laser source and the waveguide being placed in one and the same housing.
7. The laser device according to claim 1 , wherein the length of the waveguide is below 100 m.
8. The laser device according to claim 1 , wherein the laser source is single-wavelength or multi-wavelength or tunable in wavelength.
9. The laser device according to claim 1 , wherein the laser source includes several single-wavelength lasers.
10. The laser device according to claim 1 , wherein the laser source is solid-state.
11. The laser device according to claim 1 , wherein the at least four reflectors consist of four reflectors, and wherein a total power reflectivity of the waveguide is at least 0.1%.