| 摘要 |
An optical-fiber-based light source that generates light via third-harmonic (TH) generation is disclosed. The light source includes a pump light source that provides pump light having a fundamental mode of wavelength lambda<SUB>P</SUB>. The light source also includes an optical fiber optically coupled to the pump light source. The optical fiber's core refractive index profile has (i) a central region with a refractive index value Delta<SUB>1</SUB>, (ii) a first annular region immediately surrounding the central region and having a refractive index value Delta<SUB>2</SUB>, and (iii) a second annular region immediately surrounding the first annular region and having a refractive index value Delta<SUB>3</SUB>. The optical fiber satisfies the conditions Delta<SUB>2</SUB><Delta<SUB>1 </SUB>and Delta<SUB>2</SUB><Delta<SUB>3</SUB>, and max{Delta<SUB>1</SUB>,Delta<SUB>3</SUB>}-Delta<SUB>2</SUB>>1.2%. The pump light produces TH-generated light having a higher-order mode of wavelength lambda<SUB>TH</SUB>=(1/3)lambda<SUB>P </SUB>and that is outputted at the optical fiber output end. The pump light fundamental mode overlaps the TH-generated-light higher order mode over the length of the optical fiber to provide a conversion efficiency of 1% or greater.
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