Varying ambient conditions – temperature, air pressure and humidity levels – affect the performance of external-cavity diode lasers, resulting in mode hops and occasional incoherent, “multi-mode” emission intervals.

TOPTICA’s unique CHARM technology (Coherence-advanced regulation method) provides an active stabilization of the laser’s coherence. An integral feature of the TopMode laser family, this scheme ensures excellent long-term stability of the lasing wavelength and output power, as well as an extremely low intensity noise.

The feedback loop is implemented in the microprocessor-based TopMode CHARM Control . For applications requiring multiple wavelengths, one controller unit can serve two TopMode lasers.

In laser-based inspection and metrology tasks, CHARM enables accurate measurements by preventing sudden step changes of the laser’s power or frequency. CHARM means nothing less than relentless single-frequency operation for round-the-clock operation.