Electrically Parallel Three-Element 980 nm VCSEL Arrays with Ternary and Binary Bottom DBR Mirror Layers.

To meet the performance goals of fifth generation (5G) and future sixth generation (6G) optical wireless communication (OWC) and sensing systems, we seek to develop low-cost, reliable, compact lasers capable of sourcing 5-20 Gb/s (ideally up to 100 Gb/s by the 2030s) infrared beams across free-space line-of-sight distances of meters to kilometers. Toward this end, we develop small arrays of electrically parallel vertical cavity surface emitting lasers (VCSELs) for possible future use in short-distance (tens of meters) free-space optical communication and sensing applications in, for example, homes, data centers, manufacturing spaces, and backhaul (pole-to-pole or pole-to-building) optical links. As a starting point, we design, grow by metal-organic vapor phase epitaxy, fabricate, test, and analyze 980 nm top-emitting triple VCSEL arrays. Via on-wafer high-frequency probe testing, our arrays exhibit record bandwidths of 20-25 GHz, optical output powers of 20-50 mW, and error-free data transmission at up to 40 Gb/s-all extremely well suited for the intended 5G short-reach OWC and sensing applications. We employ novel p-metal and top mesa inter-VCSEL connectors to form electrically parallel but optically uncoupled (to reduce speckle) arrays with performance exceeding that of single VCSELs with equal total emitting areas.

Immobilization of glucose oxidase onto a novel platform based on modified TiO2 and graphene oxide, direct electrochemistry, catalytic and photocatalytic activity.

In this work a new organic-inorganic nanocomposite has been introduced for enzyme immobilization. The composite consisting of graphene oxide (GO) and titanium oxide nanoparticles (TiO2) modified with 2, 2'-dithioxo-3, 3'-bis (3-(triethoxysilyl) propyl)-2H, 2'H-[5, 5'-bithiazolylidene]-4, 4'(3H, 3'H)-dione as Organic-Inorganic Supporting Ligand (OISL). The OISL was covalently attached to TiO2 nanoparticles and employed for obtaining a suitable solid surface to enzyme attachment. The glucose oxidase (GOD) was irreversibly loaded on the GC/GO/TiO2-OISL using consecutive cyclic voltammetry. The enzyme immobilization and the enzymatic activity were determined by electrochemical methods. The cyclic voltammogram displayed a pair of well-defined and nearly symmetric redox peaks with a formal potential of -0.465V and an apparent electron transfer rate constant of 1.74s-1. The GO/TiO2-OISL can catalyze the electroreduction and electrooxidation of hydrogen peroxide. The GC/GO/TiO2-OISL/GOD electrode was used in the hydrogen peroxide determination. The fabricated nanobiocomposite shows dramatic photoelectrocatalytic activity which evaluated by studying the electrocatalytic activity of the fabricated electrode toward hydrogen peroxide in darkness and in the presences of light.