Prism-based Cr:forsterite laser frequency comb stabilization and carrier-envelope offset frequency linewidth narrowing

Rajesh Thapa, Karl Tillman, Kevin Knabe, Andrew Jones, Brian Washburn, Kristan Corwin
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA

Infrared frequency combs in the near IR, based on lasers such as Cr:forsterite, are important for frequency measurements in the telecommunications band. We have actively stabilized a self-referenced prism-based Cr:forsterite frequency comb using both prism and power control inside the cavity. We also report dramatic reduction in the linewidth of the carrier envelope offset frequency f₀ by at least two orders of magnitude simply by inserting a knife edge into the laser cavity after the prisms. We have stabilized the laser when the f₀ beat width was both wide (~1.5 MHz) and narrow (~10 kHz) although the locking was less robust with the narrower beat note. We measured the fractional stability of the comb by counting the repetition frequency f_r and f₀. The fractional stability of the comb at 10 s was limited by the frequency counter resolution to < 10^-12. An optical characterization of the stability is in progress. Furthermore, we will use this comb to characterize optical frequency references based on acetylene-filled hollow photonic band gap optical fibers.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy, and by the National Science Foundation.

Presented at DAMOP, May 2008, in State College, PA.

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