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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 22 — Oct. 22, 2012
  • pp: 24987–25013

Optimization of filtering schemes for broadband astro-combs

Guoqing Chang, Chih-Hao Li, David F. Phillips, Andrew Szentgyorgyi, Ronald L. Walsworth, and Franz X. Kärtner  »View Author Affiliations

Optics Express, Vol. 20, Issue 22, pp. 24987-25013 (2012)

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To realize a broadband, large-line-spacing astro-comb, suitable for wavelength calibration of astrophysical spectrographs, from a narrowband, femtosecond laser frequency comb (“source-comb”), one must integrate the source-comb with three additional components: (1) one or more filter cavities to multiply the source-comb’s repetition rate and thus line spacing; (2) power amplifiers to boost the power of pulses from the filtered comb; and (3) highly nonlinear optical fiber to spectrally broaden the filtered and amplified narrowband frequency comb. In this paper we analyze the interplay of Fabry-Perot (FP) filter cavities with power amplifiers and nonlinear broadening fiber in the design of astro-combs optimized for radial-velocity (RV) calibration accuracy. We present analytic and numeric models and use them to evaluate a variety of FP filtering schemes (labeled as identical, co-prime, fraction-prime, and conjugate cavities), coupled to chirped-pulse amplification (CPA). We find that even a small nonlinear phase can reduce suppression of filtered comb lines, and increase RV error for spectrograph calibration. In general, filtering with two cavities prior to the CPA fiber amplifier outperforms an amplifier placed between the two cavities. In particular, filtering with conjugate cavities is able to provide <1 cm/s RV calibration error with >300 nm wavelength coverage. Such superior performance will facilitate the search for and characterization of Earth-like exoplanets, which requires <10 cm/s RV calibration error.

© 2012 OSA

OCIS Codes
(060.4370) Fiber optics and optical communications : Nonlinear optics, fibers
(060.7140) Fiber optics and optical communications : Ultrafast processes in fibers
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(190.7110) Nonlinear optics : Ultrafast nonlinear optics

ToC Category:
Instrumentation, Measurement, and Metrology

Original Manuscript: August 1, 2012
Revised Manuscript: October 3, 2012
Manuscript Accepted: October 5, 2012
Published: October 17, 2012

Guoqing Chang, Chih-Hao Li, David F. Phillips, Andrew Szentgyorgyi, Ronald L. Walsworth, and Franz X. Kärtner, "Optimization of filtering schemes for broadband astro-combs," Opt. Express 20, 24987-25013 (2012)

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