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Proceedings Paper

Polarization-stable single-mode VCSELs for Cs-based MEMS atomic clock applications
Author(s): Ahmed Al-Samaneh; Simeon Renz; Andreas Strodl; Wolfgang Schwarz; Dietmar Wahl; Rainer Michalzik
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Paper Abstract

Vertical-cavity surface-emitting lasers (VCSELs) emitting at 894.6 nm wavelength have been fabricated for Cs-based atomic clock applications. For polarization control, a previously developed technique relying on the integration of a semiconducting surface grating in the top Bragg mirror of the VCSEL structure is employed. More specifically, we use a so-called inverted grating. The VCSELs are polarized orthogonal to the grating lines with no far-field diffraction side-lobes for sub-wavelength grating periods. Orthogonal polarization suppression ratios exceed 20 dB. The polarization stability has been investigated at different elevated substrate temperatures up to 80 °C, where the VCSEL remains polarization-stable even well above thermal roll-over. For the purpose of integration with the atomic clock microsystem, flip-chip-bondable VCSEL chips have been realized. Sub-mA threshold currents and sufficient output powers in the milliwatt range are achieved. The required modulation bandwidth of more than 5 GHz is reached at only 0.5mA bias. Maximum bandwidths above 10 GHz have been measured even at elevated temperatures up to 80 °C. Modulation current efficiency factors larger than 12 GHz/√mA are achieved at room temperature. Moreover, the intrinsic modulation characteristics of the VCSELs are investigated by precise curve fitting of measured small-signal modulation response curves and relative intensity noise spectra. A K-factor of less than 0.4 ns and a maximum 3 dB bandwidth exceeding 22 GHz are obtained.

Paper Details

Date Published: 27 April 2010
PDF: 14 pages
Proc. SPIE 7720, Semiconductor Lasers and Laser Dynamics IV, 772006 (27 April 2010); doi: 10.1117/12.853181
Show Author Affiliations
Ahmed Al-Samaneh, Univ. Ulm (Germany)
Simeon Renz, Univ. Ulm (Germany)
Andreas Strodl, Univ. Ulm (Germany)
Wolfgang Schwarz, Univ. Ulm (Germany)
Dietmar Wahl, Univ. Ulm (Germany)
Rainer Michalzik, Univ. Ulm (Germany)

Published in SPIE Proceedings Vol. 7720:
Semiconductor Lasers and Laser Dynamics IV
Krassimir Panajotov; Marc Sciamanna; Angel A. Valle; Rainer Michalzik, Editor(s)

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