MolECL is a new concept for a colinear distance measurement with an accurancy in the sub-micron range. It unfies the accurancy of interferometry with the easy handling on the time of flight method.

The basic idea of MolECL originates from a optoelectronic modelocking which was developed by R. Nietze, J. Sacher et al. at Marburg University. With this method, the longitudinal beat modes of an external cavity laser are transferred into electrical pulses via an avalanche photo diode. The photo diode signal is amplified and coupled back into the diode laser as modulation signal c/f R. Nietze, J. Sacher et al., Electron. Lett. 26, 1016, 1990.

J. Czarske et al. investigated the dependence of the system on the feedback phase of the electro-optical feedback loop. With zero phase detuning between the optical cavity and the electro-optical feedback loop, the signal amplitude shows a maximum and the phase shift passes zero as expected for a resonant system. When adjusting the system to zero frequency detuning, the electrical feedback frequency can be transferred into the length information of the external optical cavity. Typical adjustment times to length changes are on a ns time scale.

When using the reflection of a technical surface as external cavity mirror, this system is a extremely fast sensor with an accurancy in the sub-micron range. The sensor is called Modelocking External Cavity Laser Sensor (MolECL). Due to the mode-locking effect of the external cavity, the MolECL Sensor is superior to conventional time for flight methods  (in German 568kB).

The current research is performed within a common project together with LZH e.V. and TEM GmbH with financial support by BMBF within contract 13N1818. For further information, pease contact us.