Vertical Cavity Lasers for Atomic Time Standards

Hans P. Zappe

Abstract: The availability of Vertical Cavity Lasers (VCSELs) has allowed the development of new generations of optical systems, which can benefit from the small size, low power consumption, and high reliability of these light sources. Among diode laser families, VCSELs are particularly attractive for a number of reasons: (I) relatively simple and robust fabrication; (2) very low threshold current and, thus, low power consumption; (3) surface emission, thus simplified packaging and two-dimensional array capabilities; (4) circular emission apertures and, thus, good beam shape in the near and far-field; and (5) single-mode emission with a high wavelength tuning rate and range. Rubidium- or cesium-based atomic time standards could benefit greatly from the use of customized VCSELs as a pump for Rb or Cs. Required is a high spectral purity coupled with emission at precisely the pump wavelengths of interest: 780 or 852 nm. The Swiss Center for Electronics and Microtechnology (CSEM) has developed VCSELs for atomic time standard applications, which fulfill these requirements, and is preparing their industrialization. Optimized laser parameters include single-mode emission with a high side-mode suppression ratio, polarization stability, narrow linewidth, high tunability, and low noise. In this paper, we will discuss the principles underlying VCSEL operation, the required fabrication technology, and, finally, the electro-optical characteristics as these relate to the use of VCSELs in atomic clocks. We will present device results on 780 nm VCSELs customized for operation at elevated temperatures for use in Rb time standards. An emphasis will be placed on spectral properties, tunability, and stability. Based on these developments, it is expected that VCSELs may soon play a significant role in a new generation of compact atomic time standards.
Published in: Proceedings of the 31th Annual Precise Time and Time Interval Systems and Applications Meeting
December 7 - 9, 1999
Marriott's Laguna Cliffs Resort
Dana Point, California
Pages: 589 - 596
Cite this article: Zappe, Hans P., "Vertical Cavity Lasers for Atomic Time Standards," Proceedings of the 31th Annual Precise Time and Time Interval Systems and Applications Meeting, Dana Point, California, December 1999, pp. 589-596.
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