Inverted Grating Relief Atomic Clock VCSELs

Vertical-cavity surface-emitting lasers (VCSELs) with single-mode and single-polarization emission at a wavelength of 894.6 nm have become attractive light sources for miniaturized Cs-based atomic clocks. So far, VCSELs used for these applications are single-mode because of small active diameters which has the drawbacks of increased ohmic resistance and reduced lifetime. Employing surface grating reliefs, enhanced fundamental-mode emission as well as polarization-stable laser oscillation are achieved. VCSELs with 5μm active diameter show side-mode suppression ratios of 20 dB even at currents close to thermal roll-over with orthogonal polarization suppression ratios better than 20 dB at elevated ambient temperatures up to 100 C.