We present an optical spectroscopic study of InGaAs/AlInAs active region of quantum cascade lasers grown by low pressure metal organic vapor phase epitaxy combined with subwavelength gratings fabricated by reactive ion etching. Fourier-transformed photoluminescence measurements were used to compare the emission properties of structures before and after processing the gratings. Our results demonstrate a significant increase of the photoluminescence intensity related to intersubband transitions in the mid-infrared, which is attributed to coupling with the grating modes via so called photonic Fano resonances. Our findings demonstrate a promising method for enhancing the emission in optoelectronic devices operating in a broad range of application-relevant infrared.
In our paper, the design of a high contrast grating is optimized to obtain a wider reflectivity bandwidth. HCGs present an incidence angle dependence that can affect the reflectivity bandwidth. This dependence was mitigated by reducing the duty cycle of the HCG. A further optimized model was done by matching the reflectivity phase with the phase of the incident Gaussian wavefront. The broader bandwidth of the new designs was calculated using simulations. Subsequently the MEMS VCSELs with the new designs of HCG were fabricated. The highest tuning range obtained for the focusing design was 45nm and for the low duty cycle design 38nm. These ranges are lower than the standard design due to differences from the design. Further improvements in the fabrication process are required to demonstrate the new designs proposed.
The design of transparent conductive electrodes (TCEs) for optoelectronic devices requires a trade-off between high conductivity or transmittivity, limiting their efficiency. This paper demonstrates a novel approach to fabricating TCEs: a monolithic GaAs high contrast grating integrated with metal (metalMHCG). The technology and influence of fabricated different configurations of metalMHCG on the optical parameters will be shown. We will demonstrate above 90% absolute transmittiance of unpolarized light, resulting in 130% transmittance relative to plain GaAs substrate. Despite record high transmittance, the sheet resistance of the metalMHCG is several times lower than any other TCE, ranging from 0.5 to 1 OhmSq−1.
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