1. Department of Physics, University of Gothenburg, SE-412 96 Göteborg, Sweden
2. Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel and Physics Department, Ben Gurion University, Beer Sheva 84105, Israel
3. Department of Physics, University of Gothenburg, SE-412 96 Göteborg, Sweden and SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS Scotland, United Kingdom