Improved active fiber-based retroreflector with intensity stabilization and a polarization monitor for the near UV

Optics Express, vol. 29, pp. 7024

Abstract

We present an improved active fiber-based retroreflector (AFR) providing high-quality wavefront-retracing anti-parallel laser beams in the near UV. We use our improved AFR for first-order Doppler-shift suppression in precision spectroscopy of atomic hydrogen, but our setup can be adapted to other applications where wavefront-retracing beams with defined laser polarization are important. We demonstrate how weak aberrations produced by the fiber collimator may remain unobserved in the intensity of the collimated beam but limit the performance of the AFR. Our general results on characterizing these aberrations with a caustic measurement can be applied to any system where a collimated high-quality laser beam is required. Extending the collimator design process by wave optics propagation tools, we achieved a four-lens collimator for the wavelength range 380–486 nm with the beam quality factor of M2 ≃ 1.02, limited only by the not exactly Gaussian beam profile from the single-mode fiber. Furthermore, we implemented precise fiber-collimator alignment and improved the collimation control by combining a precision motor with a piezo actuator. Moreover, we stabilized the intensity of the wavefront-retracing beams and added in-situ monitoring of polarization from polarimetry of the retroreflected light.

Authors 9

1. Vitaly Wirthl

   Max Planck Institute of Quantum Optics

   Affiliation as printed

   Max Planck Institute of Quantum Optics (MPQ)

2. Lothar Maisenbacher

   Max Planck Institute of Quantum Optics

   Affiliation as printed

   Max Planck Institute of Quantum Optics (MPQ)

3. Johannes Weitenberg Aachen

   Max Planck Institute of Quantum Optics · RWTH Aachen University

   Affiliation as printed

   Max Planck Institute of Quantum Optics (MPQ)

   RWTH Aachen University

4. Alexander Hertlein

   Max Planck Institute of Quantum Optics

   Affiliation as printed

   Max Planck Institute of Quantum Optics (MPQ)

5. Alexey Grinin

   Max Planck Institute of Quantum Optics

   Affiliation as printed

   Max Planck Institute of Quantum Optics (MPQ)

6. Arthur Matveev

   Max Planck Institute of Quantum Optics · Ludwig-Maximilians-Universität München

   Affiliation as printed

   Ludwig Maximilian University (LMU)

   Max Planck Institute of Quantum Optics (MPQ)

7. Randolf Pohl

   Johannes Gutenberg University Mainz

   Affiliation as printed

   Johannes Gutenberg University

8. Theodor W. Hänsch

   Max Planck Institute of Quantum Optics · Ludwig-Maximilians-Universität München

   Affiliation as printed

   Ludwig Maximilian University (LMU)

   Max Planck Institute of Quantum Optics (MPQ)

9. Thomas Udem

   Max Planck Institute of Quantum Optics · Ludwig-Maximilians-Universität München

   Affiliation as printed

   Ludwig Maximilian University (LMU)

   Max Planck Institute of Quantum Optics (MPQ)