Polylactic Acid Nanonetworks as High Reflectance Distributed Bragg Reflectors

Natural systems found ways to exploit light at the nanoscale, devising complex 3D structures that behave as photonic crystals, able to produce structural coloration. Distributed Bragg reflectors are a particular...

Highly reflective and conductive AlInN/GaN distributed Bragg reflectors realized by Ge-doping

We report on the realization of highly conductive and highly reflective n-type AlInN/GaN distributed Bragg reflectors (DBR) for use in vertical cavity surface emitters in a metalorganic vapor phase epitaxy process. While Ge-doping enables low-resistive n-type GaN/AlInN/GaN heterostructures, very high Ge doping levels compromise maximum optical reflectivities of DBRs. Simulations of the Bragg mirror's reflectivities together with structural analysis by X-ray diffraction reveal an increased absorption within the doped AlInN layers and interface roughening as major causes for the observed reduction of the optical reflectivity. By adjusting the Ge doping level in the AlInN layers, this structural degradation was minimized and highly conductive, 45-fold AlInN/GaN DBR structures with a maximum reflectivity of 99 % and vertical specific resistance of 5x10-4 Ωcm2 were realized.

Planar narrowband Tamm plasmon-based hot-electron photodetectors with double distributed Bragg reflectors

Hot-electron photodetectors (HE PDs) are attracting a great deal of attention from plasmonic community. Many efficient HE PDs with various plasmonic nanostructures have been demonstrated, but their preparations usually rely on complicated and costly fabrication techniques. Planar HE PDs are viewed as potential candidates of cost-effective and large-area applications, but they likely fail in the simultaneous achievement of outstanding optical absorption and hot-electron collection. To reconcile the contradiction between optical and electrical requirements, herein, we propose a planar HE PD based on optical Tamm plasmons (TPs) consisted of an ultrathin gold film (10 nm) sandwiched between two distributed Bragg reflectors (DBRs). Simulated results show that strong optical absorption (>0.95) in the ultrathin Au film is realized. Electrical calculations show that the predicted peak photo-responsivity of proposed HE PD with double DBRs is over two times larger than that of conventional single-DBR HE PD. Moreover, the planar dual-DBR HE PDs exhibit a narrowband photodetection functionality and sustained performance under oblique incidences. The optical nature associated with TP resonance is elaborated.

A Comparative Study of Electrical Characterization of P-Doped Distributed Bragg Reflectors Mirrors for 1300 nm Vertical Cavity Semiconductor Optical Amplifiers

This paper presents an electrical analysis of various diameters of two p-types of GaAs/Al0.9Ga0.1As and two p-types of GaAs/Al0.3Ga0.7As/Al0.9Ga0.1As distributed Bragg reflectors (DBRs) mirrors structure grown on undoped and on p-doped GaAs, which affects the characteristics of 1300 nm vertical cavity surface emitting lasers (VCSELs) and vertical cavity semiconductor optical amplifiers (VCSOAs). Electrical characterizations and Hall measurements of current−voltage (IV) for GaAs/Al0.9Ga0.1As linear DBRs and GaAs/Al0.3Ga0.7As/Al0.9Ga0.1 As graded DBRs were also performed at temperatures between 13 and 300 K. Consequently, p-type DBRs are designed with graded composition interfaces technique. The smaller mesa diameters are used to reduce vertical and longitudinal resistances and to limit the heating effect and improve the characteristics of VCSEL/VCSOA devices.