Glass micro-fibers for efficient third harmonic generation.

We introduce a rigorous theory of third-harmonic generation in optical waveguides and apply it to design a micro-fiber waveguide for efficient generation of third-harmonic radiation from infrared lasers. Phase-matching with efficient mode overlap is achieved in micro-fibers having a diameter roughly equal to half of the fundamental wavelength. Using a typical solid-state or fiber laser for pumping, high conversion efficiency is possible in only a few centimeters of a micro-fiber.