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We use frequency combs based on ultrafast mode-locked lasers to perform precision spectroscopy in the near- and mid-infrared domains, for rapid, high-sensitivity, broadband gas detection.
Erbium mode-locked fiber lasers are a mature technology that provide a means to build robust optical frequency combs centered near 1550 nm. One research focus of our group is to extend the optical bandwidth of Er fiber-based combs into the near- to mid-infrared wavelength region of 1000 to 5000 nm in order to access fundamental absorption bands of molecular gases. Recent work includes the building of a frequency comb which has a supercontinuum spectrum spanning 1000 nm to 2200 nm. This comb was produced by passing ultrafast pulses generated in Er fiber through highly nonlinear optical fiber. The 2000 nm portion of the spectrum has been used to perform spectroscopic measurements of carbon dioxide. Additionally, a frequency comb spanning 2800 nm to 3500 nm has been demonstrated using difference frequency generation of 1550 nm and 1060 nm light in a 3 mm PPLN crystal. Both the 1550 nm signal and 1060 nm pump are initiated with the same Er-based frequency comb. Our group employs a variety of spectroscopic techniques to analyze the frequency combs after the light interacts with a sample. One technique that is used is virtually-imaged phased array- (VIPA-) based spectroscopy, where the comb modes are spatially separated in two dimensions and imaged on a detector array. Dual-comb spectroscopy (DCS) is another technique exploited for precision measurements. DCS is an analog of traditional Fourier-transform spectroscopy were two frequency combs with slightly different repetition rates are heterodyned against each other on a photodiode. The optical spectrum, including sample absorption, is obtained by Fourier-transforming the time-domain spectrum of the photodiode.
Apply for an NRC postdoc in optical atomic clock or fs-laser frequency comb research. Application deadlines are February 1 and August 1 annually (but inquire well in advance).
Summer program at NIST-Boulder for undergraduates in science, engineering, and mathematics. The application deadline is February 15 annually.
Postdoctoral, Visiting Scientist, and Graduate Positions
Our Group has periodic openings for Postdoctoral Fellows, Visiting Scientists, and Graduate Students. Please contact us for more information.