Strategy to Achieve Phase Matching Condition for Third Harmonic Generation in All-Solid Photonic Crystal Fibers

All-fiber based devices for third harmonic generation in the ultraviolet range are highly desirable. Using a fundamental wavelength of 1.06 μm as an example, we show numerically how the phase-matching condition for third harmonic generation can be achieved between an index-guided fundamental HE₁₁ mode for the infrared source and a bandgap-guided higher-order HE₁₂ mode for the ultraviolet radiation in all-solid photonic crystal fibers. The fiber parameters are first determined by an analytical effective index model and then improved by numerical calculations.