Optical Waveguides Formed by Proton Irradiation of Fused Silica*†

TLDR

Various techniques for fabricating optical waveguides for laser‑oriented applications are being studied. The study presents a proton‑irradiation technique that creates a slightly higher‑index channel in fused silica for use as an optical waveguide core. Proton irradiation induces a high‑index channel in fused silica, with core size and index contrast adjustable by proton energy and dosage, and formulas are provided to calculate channel dimensions and index change. The technique produces waveguides with core widths of 1–50 µm and index differences of 0.0001–0.01, enabling complex arrays, and light propagation has been observed using 1.5‑MeV protons at doses of 10^14–10^17 protons/cm².

Abstract

Various techniques for fabricating optical waveguides for laser-oriented applications are being studied. A technique utilizing radiation-induced changes of refractive index in optical materials is presented; the particular waveguide considered is a fused-silica slab that has been irradiated with protons to produce a channel with a refractive index slightly higher than the unirradiated silica. This high-index channel serves as the waveguide core and the surrounding unirradiated region as the cladding.Formulas for determining the size and shape of the high-index channel and the amount of index change have been developed. The primary waveguide parameters, core size, and refractive-index difference, may be adjusted by controlling proton energy and dosage, respectively. The technique is useful for formation of waveguides with core widths of 1 to 50 μ and index differences of 0.01 to 0.0001; it is particularly suitable for forming complex arrays of waveguides and waveguide components.Preliminary experimental work has used 1.5-MeV protons and dosages of 1014 to 1017 protons/cm2. Light propagation has been observed in waveguides formed by this technique.