Ultra-flat dispersion in an integrated waveguide with five and six zero-dispersion wavelengths for mid-infrared photonics

TLDR

The authors propose a dispersion‑flattening technology that produces an ultra‑flat group‑velocity dispersion profile featuring five to six zero‑dispersion wavelengths. They explain how to generate six zero‑dispersion wavelengths, provide guidelines for tuning dispersion magnitude, sign, and slope through structural parameters, and assess fabrication tolerance. The waveguide achieves a dispersion range of –0.15 to 0.35 ps/(nm·km) between 4 and 8 µm—reported as the flattest to date, exceeding flatness by more than an order of magnitude—and maintains stable mode distribution across the bandwidth.

Abstract

We propose a new type of dispersion flattening technology, which can generate an ultra-flat group velocity dispersion profile with five and six zero-dispersion wavelengths (ZDWs). The dispersion value varies from −0.15 to 0.35 ps/(nm·km) from 4 to 8 μm, which to the best of our knowledge is the flattest one reported so far, and the dispersion flatness is improved by more than an order of magnitude. We explain the principle of producing six ZDWs. Mode distribution in this waveguide is made stable over a wide bandwidth. General guidelines to systematically control the dispersion value, sign, and slope are provided, and one can achieve the desired dispersion by properly adjusting the structural parameters. Fabrication tolerance of this waveguide is also examined.