Patent ID: 7339721

Claim:
An optical-fiber-based light source that generates light via third-harmonic (TH) generation, comprising: a pump light source that provides pump light having a fundamental mode of wavelength λ P ; an optical fiber having an input end, an output end, a length L, and a core formed about a centerline and having a refractive index profile (Δ(%)), wherein the optical fiber is optically coupled to the pump light source at its input end; wherein the core refractive index profile has (i) a central region centered on the center line and having a refractive index value Δ 1 and an outer radius r 1 , (ii) a first annular region immediately surrounding the central region and having a refractive index value Δ 2 and an inner and outer radii of r 1 and r 2 , respectively, and (iii) a second annular region immediately surrounding the first annular region and having a refractive index value Δ 3 and an inner and outer radii of r 2 and r 3 , respectively; wherein Δ 2 <Δ 1 and Δ 2 <Δ 3 , and wherein max{Δ 1 ,Δ 3 }−Δ 2 >1.2%; and wherein the pump light produces the TH-generated light having a higher-order mode of wavelength λ TH =(1/3)λ P and is outputted at the optical fiber output end, and wherein the pump light fundamental mode overlaps the TH-generated-light higher order mode over the length L so as to provide a conversion efficiency of pump light to TH-generated light of 1% or greater.