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WP 3 - Fabrication and Testing

Fig. 1. Optical image of ring ICLs.

Within this workpackage we are dedicated to the design, development and fabrication of 2nd order ring-DFB cavities for ICLs. For this purpose we are working on developing suitable device fabrication schemes. Testing and characterization of the fabricated devices is then carried out in order to accomplish device optimization with regard to threshold-current density, optical output power, electrical dissipation and emission wavelength.

To achieve surface emission in ICL structures, ring-cavity waveguides including 2nd order DFB gratings are designed, using the commercially available software “Comsol Multiphysics”. The laser cavities are optimized for several figures of merit including emission wavelength, optical output power, threshold current-density, electrical dissipation and optical farfield emission. This is achieved by modifying various parameters like grating periodicity (effective refractive index neff is extracted from test structures and compared to simulations), ring-diameter and -width and type of DFB grating (fully gold-covered, i.e. complex-coupled grating or 50% gold-covered, i.e. index-coupled grating). The process development and device fabrication takes place in the state-of-the-art cleanroom ZMNS at TU Wien, using the needed equipment like: PECVD, (ICP-)RIE, Lithography, metal & dielectrics sputter tool, thermal & e-beam evaporator, RTA & O2 plasma oven as well as the characterization tools like SEM, AFM, wafer probe station etc. Fabricated devices are tested in the in-house lab of the IOG which includes light-current-voltage and FTIR measurements (spectral emission) as well as investigations of the farfield pattern. This will give additional information and feedback, for optimizing the ICL active region design.