Ultrafast laser-inscribed mid-infrared evanescent field directional couplers in GeAsSe chalcogenide glass

Abstract

Mid-infrared evanescent field directional couplers operating at ~8 µm are demonstrated by ultrafast laser inscription of waveguides in Ge33As12Se55 (IG2) chalcogenide glass. Through-port coupling ratios from > 99:1 to < 1:99 were observed, and comparison of the measured devices to analytic and numeric models verifies device performance against theory. Insertion loss of the couplers is estimated to be 0.9 dB, in addition to approximately 1 dB/cm propagation loss. These couplers are developed to enable more complex mid-infrared, and particularly the long wave infrared, ultrafast laser-inscribed photonics components, such as integrated Mach-Zehnder interferometers and photonic lanterns, to be realized in future.