Patent ID: 8509577

Claim:
A fiberoptic device comprising: an optical fiber having a fiber core and an end through which a light beam emits from the fiber core; a beam expander having a first end coupled to the end of the optical fiber and having a second end, the beam expander permitting the light beam emitting from the fiber core to pass from the first end to the second end and to expand from the first end to a larger size at the second end; and a gradient-index fiber lens coupled to the second end of the beam expander to receive the light beam from the beam expander and focus the light beam; wherein the gradient-index fiber lens has a core with a diameter D grin ; wherein the beam expander has a length between the first end and the second end, L BE , which is determined by D 1 =D core +2 L BE tan(θ BE ) where D 1 is a beam diameter of the light beam at the second end of the beam expander and is approximately equal to the diameter D grin of the gradient-index fiber lens, the optical fiber has a cladding and the fiber core has a core diameter of D core , and θ BE is a divergent angle of the light beam exiting the optical fiber; wherein θ BE =a sin(NA/ n BE ) where n BE is a refractive index of the beam expander, and NA is a numerical aperture of the optical fiber, NA=√{square root over (n 1 2 −n 2 2 )}, n 1 is a refractive index of the fiber core of the optical fiber, and n 2 is a refractive index of the cladding of the optical fiber; and wherein the second end of the beam expander has a larger size than the core diameter of the fiber core of the optical fiber to allow the light beam from the fiber core to expand within the beam expander from the first end to the second end.