1. National Institute of Standards and Technology, Boulder, Colorado 80305, USA
2. Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
3. Novosibirsk State University, ul. Pirogova 1, Novosibirsk 630090, Russia
4. Institute of Laser Physics SB RAS, pr. Akademika Lavrent'eva 3, Novosibirsk 630090, Russia
5. Novosibirsk State Technical University, pr. Karla Marksa 20, Novosibirsk 630073, Russia