Selected Applications
Industrial Line
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Cavity Enhanced Raman Microscopy
Raman spectroscopy has long been an indispensable tool for chem-
ical analysis. However on the molecular level signals remain in-
trinsically small. Recently Th. Hümmer et al from the group of Prof.
Hänsch achieved a more than sixfold amplification by putting the
sample inside a tiny cavity. The cavity formed by the sample and a
micro mirror on the tip of an optical fiber (1) can be scanned by a
set of attocube’s ECSx3030 positioners to obtain images with close
to optical resolution. The micro cavity is adjusted with some tens
of pm resolution using another ECS positioner and an additional
piezo. The signal is enhanced due to the Purcell effect stemming
from the enhanced photon lifetime in a small cavity volume (2).
The group around Dr. Hunger at the LMU Munich applied the new
method to some carbon nanotubes leading to clear pictures show-
ing (3) the extinction cross-section and (4) the Raman signal of the
G’ mode. “The cavity amplifies both the Raman scattering process
as well as absorption from the sample. This allows one to combine
ultrasensitive absorption microscopy with Raman imaging within a
single measurement.”, explains Dr. Hunger. The group is confident
to improve the method further boosting the signal enhancement by
several orders of magnitude in the future.
Th. Hümmer, J. Noe, M. Hofmann, T. W. Hänsch, A. Högele, and D. Hunger; Nature Communica-
tions 7, 12155, 12 July 2016
*Pictures are under Creative Commons Attribution 4.0 international license
attoMOTION
Piezo-based Nano Drives
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