Physics Seminar: "Octave-wide frequency combs in the
mid-infrared and their applications for sensing molecules" Konstantin
Vodopyanov
Friday, August 29, 2014 4:30 PM to 6:00 PM
Physical Sciences Room 161
Physical Sciences Room 161
Optical frequency combs produced by ultrafast mode-locked
lasers have revolutionized precision spectroscopy and time metrology,
culminating in the 2005 Nobel Prize in Physics. I will present a new technique
for extending frequency combs to the highly desirable yet difficult-to-achieve
mid-infrared range - the region of fundamental molecular fingerprints. The
technique is based on subharmonic optical parametric oscillation (OPO) that can
be considered as a reverse of second harmonic generation. Using ultrafast
erbium or thulium fiber lasers as a pump, we produce frequency combs that can
be more than octave wide, e.g. span from 2.5 to 6 µm without gaps. I will talk
about coherent properties of the generated mid-IR combs, as well as their
applications including trace molecular detection via absorption spectroscopy.
Working in the Fourier domain allows taking advantage of massive parallelism of
spectral measurements (thanks to the broad spectrum), as well as very high
speed of data acquisition (thanks to the coherent nature of the frequency
combs), up to 1M spectral points in a fraction of a second.
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