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Cavity Enhanced Raman Microscopy
Raman spectroscopy has long been an indispensable tool for chemical analysis . However on the molecular level signals remain intrinsically 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 showing ( 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 Communications 7 , 12155 , 12 July 2016
* Pictures are under Creative Commons Attribution 4.0 international license
attoMOTION
Piezo-based Nano Drives