Faraday Rotation in Amorphous Chalcogenide Films. A. Zoubir, R. A. Jarvis, M. Krolikowska, R. P. Wang, S. Madden, Y. Ruan, A. V. Rode, B. Luther-Davies Laser Physics Centre, Research School of Physical Sciences and Engineering, Australian National University, ACT 0200, Australia email:ruth.jarvis@anu.edu.au, Phone: +61 2 6125 0031, Fax: +61 2 6125 0029 Abstract: We measured the wavelength dispersion of magneto-optic rotation in amorphous chalcogenide thin-films deposited by pulsed laser deposition. The largest rotation is achieved in films with high Germanium concentration being more than 25-times greater than silica. ©2006 Optical Society of America OCIS codes: (160.3820) Magneto-optical materials; (310.6860) Thin films, optical properties. The possibility of integrated magneto-optic photonic waveguiding devices opens a world of opportunities for new devices and functionalities such as optical isolators, previously only available in bulk optics. Other investigations into integrated magneto-optics have recently been focused on crystalline magnetic materials [1], however to avoid the problems associated with compatibility of substrates and stress and birefringence, we are exploring amorphous materials which display magneto-optic activity. The chalcogenide glasses offer one such possibility. These low phonon materials which have high linear and nonlinear refractive indices and are transparent in the infrared region, are very attractive for both nonlinear devices and magneto-optic applications. Using ultra-fast pulsed laser deposition, it is possible to produce optical quality thin films for waveguide fabrication on silica/silicon substrates. Furthermore because it is possible to produce films with accurate stochiometries of the starting target materials, or through combinatorial synthesis of several targets, a wide range of chalcogenide films can be fabricated to produce the optimal optical properties. Faraday rotation (FR) is a nonreciprocal rotation of the plane of polarization of a linearly polarized electromagnetic wave in a longitudinal magnetic field. This field induces different dispersions in the right and left circularly polarized components. The phase difference between the two components results, after a distance L, in a rotation of the plane of polarization through the angle θ, and depends on the magnetic field, H and a material property, V d , the Verdet constant. Thus the Faraday rotation is given by LH V d = θ . The measurement system is depicted in Figure 1. Thin film samples were mounted on microscope slides and placed inside the field of a purpose built magnet which has an aperture in its centre. A linearly polarized collimated laser beam from a fibre-coupled laser was focused onto the sample through the aperture in the magnet. The beam is reflected from the back of the sample and passes through the Soleil-Babinet compensator (SBC) which acts as a half-wave plate oriented at 45º. A biconvex lens (L) focuses the beam onto the balanced detector (BD). The beam is analysed by a Wollaston prism (WP) oriented to separate the light into two diverging orthogonal components having perpendicular polarizations at +/- 45º to the input polarization direction. The setup is carefully aligned such that each split beam hits the centre of the detector’s photodiodes with the same intensity, in the absence of the magnetic field. Fig. 1: Experimental setup for the Verdet constant measurement. BD – balanced detector; WP – Wollaston prism; L – lens; SBC – Soleil-Babinet compensator; P – polarizer; C – collimator; F – Fibre. An alternating current is applied at 17Hz to the magnetic coil, giving an rms field of 0.375T. In the presence of the magnetic field, the Faraday rotation causes a change in the balanced beams, which translates into a voltage δV measured by the lock-in amplifier. It may be noted that the Magneto-Optical Kerr effect is responsible for a small but measurable rotation of the polarization when the polarized beam reflects on the Aluminum-coated surface [2]. However, this effect was found to be negligible compared to the Faraday rotation arising from the propagation in the thin film. F P Laser C Magnet SBC WP BD Sample L Lock-in amplifier B