1. Fraunhofer Institute for Photonic Microsystems (IPMS), Dresden, Germany. E-mail: roscher@ipms.fraunhofer.de
2. Fraunhofer Institute for Photonic Microsystems (IPMS), Dresden, Germany
3. Institute of Acoustics and Speech Communication, TU Dresden, Dresden, Germany
4. Institute of Semiconductors and Microsystems, TU Dresden, Dresden, Germany