title: Low loss mid-infrared ZBLAN waveguides for future astronomical applications.
abstract: Photonic technologies will be at the heart of future terrestrial planet hunting interferometers. In particular the mid-infrared spectral region between 3.5 - 4.2 μm is the ideal window for hunting for young extra-solar planets, since the planet is still hot from its formation and thus offers a favorable contrast with respect to the parent star compared to other spectral regions. This paper demonstrates two basic photonic building blocks of such an instrument, namely single-mode waveguides with propagation losses as low as 0.29±0.03 dB/cm at a wavelength of 4 μm as well as directional couplers with a constant splitting ratio across a broad wavelength band of 500 nm. The devices are based on depressed cladding waveguides inscribed into ZBLAN glass using the femtosecond laser direct-write technique. This demonstration is the first stepping stone towards the realization of a high transmission mid-infrared nulling interferometer.
authors.forename: Simon
authors.initials: S
authors.lastname: Gross
authors.forename: Nemanja
authors.initials: N
authors.lastname: Jovanovic
authors.forename: Adam
authors.initials: A
authors.lastname: Sharp
authors.forename: Michael
authors.initials: M
authors.lastname: Ireland
authors.forename: Jon
authors.initials: J
authors.lastname: Lawrence
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Withford