|
November, 2004 EEEL Demonstrates Accordion-Like Frequency Comb Using a Fiber Laser With a Variable Repetition Rate |
|
Infrared frequency combs based on fiber laser technology can provide stable frequency markers across the infrared from 1100 nm to 2200 nm. Previously, researchers at NIST in collaboration with researchers at OFS laboratories demonstrated the first fully phase-locked fiber laser frequency comb. Recently, Nathan Newbury and Brian Washburn of EEEL's Optoelectronics Division, in collaboration with OFS laboratories, have demonstrated a new configuration for a fiber-laser based frequency comb using a variable repetition-rate fiber laser. In this configuration, the spacing between the optical comb lines can be varied, which causes the frequency of an individual comb tooth in the 1550 nm region to change by up to 3 THz (25 nm) in an accordion-like fashion. This comb should be useful for wavelength and length metrology, synchronization of different fiber laser-based frequency combs, and the generation of precise swept wavelength sources. For example, an optical frequency comb can be used to accurately measure the output frequency of a laser. However, this measurement typically requires an initial determination of the laser frequency by an expensive wavelength meter; with the accordion frequency comb there is no need for this wavelength meter. As another example, one could envision phase-locking a tunable continuous wave (cw) laser to one tooth of the comb. If the comb spacing is then expanded, the cw laser frequency will sweep by up to 3 THz in a precisely controlled manner. The cw laser would therefore provide a highly calibrated swept infrared source that could be used for precision spectroscopy.
|