Multicore optical fiber with integral diffractive elements machined by ultrafast laser direct writing

A multicore optical fiber with an integral diffractive element, comprising:

• a first optical fiber core formed of a non-photosensitive material having an initial index of refraction, the first optical fiber core including;
• a first longitudinal core axis;
• a plurality of index-altered portions along the first optical fiber core in a longitudinal direction and having an altered index of refraction different from the initial index of refraction;
• and
• a second optical fiber core including a second longitudinal core axis substantially parallel to the first longitudinal axis;
• wherein:
• the plurality of index-altered portions are arranged within the non-photosensitive material of the first optical fiber core to form a diffractive structure;
• and
• the first transmission surfaces and the second transmission surfaces of the plurality of index-altered portions are one of conic surfaces, spherical curved surfaces, or aspherical curved surfaces.

A wavelength stabilized, high power, uncooled laser source, comprising:

• at least one high power laser;
• and
• a multicore optical fiber optically coupled to the at least one high power laser, the multicore optical fiber including;
• a first optical fiber core formed of a non-photosensitive material having a first index of refraction, the first optical fiber core including;
• a first longitudinal core axis;
• a circular cylindrical shape;
• a first core radius;
• a Bragg grating section that includes a first plurality of index-altered portions having an altered index of refraction different from the first index of refraction;
• a laser coupling surface normal to the first longitudinal core axis optically coupled to the at least one high power laser;
• and
• a coupling section adjacent to the laser coupling surface with a second plurality of index-altered portions, the second plurality of index-altered portions being arranged within the coupling section to form an integral diffractive coupling optics structure;
• and
• a second optical fiber core having a second index of refraction which is less than the first index of refraction of the first optical fiber core, the second optical fiber core including;
• a second longitudinal core axis substantially collinear with the first longitudinal axis;
• an annular cylindrical shape;
• an inner second core radius equal to the first core radius of the first optical fiber core;
• and
• an outer second core radius;
• wherein the first plurality of index-altered portions are arranged within the non-photosensitive material of the first optical fiber core to form a Bragg grating structure for reflecting a predetermined fraction of light in a predetermined wavelength band propagating in the first optical fiber core back into the at least one high power laser to lock an output wavelength band of the wavelength stabilized, high power, uncooled laser source to the predetermined wavelength band.