Dual-mode DFB laser diodes with apodized surface gratings.

Dual longitudinal mode distributed feedback lasers have been fabricated using surface gratings with and without apodization. Analytic formulas and simulations that have been used to derive design guidelines are presented. The fabricated device characteristics are in good agreement with the simulations. The grating apodization enables a lower threshold current density, a higher output power and a broader range of difference frequency tunability by bias, which can be extended beyond the measured 15-55 GHz by changing the device structure. The apodization and the complex coupling of the surface gratings reduce the effects of the uncontrollable phase of facet reflections, enabling the use of higher facet reflectivities, which leads to narrower intrinsic short time-scale linewidths.

Distributed feedback lasers with alternating laterally coupled ridge-waveguide surface gratings.

Distributed feedback lasers with laterally coupled ridge-waveguide surface gratings having the protrusions placed alternately on the lateral sides of the ridge are demonstrated. This configuration enables easier-to-fabricate wider trenches than in the gratings with protrusions placed symmetrically on both sides of the ridge. The design strategy and coupling coefficient calculations are discussed. The output characteristics of fabricated lasers show lower threshold currents and higher slope efficiencies for devices with first-order alternating gratings than for those with third-order symmetric gratings having comparable grating trench widths and similar coupling coefficients.

The influence of temperature on the photoluminescence properties of single InAs quantum dots grown on patterned GaAs.

We report the temperature-dependent photoluminescence of single site-controlled and self-assembled InAs quantum dots. We have used nanoimprint lithography for patterning GaAs(100) templates and molecular beam epitaxy for quantum dot deposition. We show that the influence of the temperature on the photoluminescence properties is similar for quantum dots on etched nanopatterns and randomly positioned quantum dots on planar surfaces. The photoluminescence properties indicate that the prepatterning does not degrade the radiative recombination rate for the site-controlled quantum dots.