Quantum Optoelectronics

Abstract:

A piezoelectric energy generating device that produces electricity using plasmon-enhanced solar radiation pressure (SRP) is developed. The SRP is greatly enhanced on the operational region of the device with a unique crater-like structure, and direct current is generated successfully on the device. By optimizing the material and thickness of top electrode, a maximum power density of 396 µW cm−2 is obtained. In addition, by using Raman measurements, finite-difference time-domain simulation, and COMSOL Multiphysics analysis, it is confirmed that the SRP is greatly amplified on the operational region with the nanoscale surface roughness due to resonance between the incident light and surface plasmons. By increasing the rotational speed of an optical chopper used to measure the change in the output characteristics of the device, and comparing this with the simulated result, it is found that the constant charge produced by the piezoelectric effect arose due to the superposition of charge phases in the device.

Abstract:

2D-layered transition metal chalcogenides are useful semiconductors for a wide range of opto-electronic applications. Their similarity as layered structures offers exciting possibility to modify their electronic properties by creating new heterojunction assemblies from layer-by-layer restacking of individual monolayer sheets, however, the lack of specific interaction between these layers could induce phase segregation. Here, we employed a chemical method using n-BuLi to exfoliate MoS₂ and In₂Se₃ into their monolayer-containing colloids in solution. The bulky Se atoms can be selectively leached from In₂Se₃ during Li treatment which gives positively charged surface monolayers in neutral pH whereas the strong polarization of Mo–S with moderate S leaching gives a negatively charged surface. Specific interlayer electrostatic attraction during their selective assembly gives a controllable atomic AB-type of layer stacking as supported by EXAFS, STEM with super-EDX mapping, TAS/TRPL and DFT calculations. Using this simple but inexpensive bottom-up solution method, a new photocatalyst assembled from layers for photo water splitting can be tailor-made with high activity.

Abstract:

Experimental research data collected in laboratories at the Clarendon Laboratory, 2020-2022.

Abstract:

We demonstrate that a two-level system, in form of an InGaN quantum dot, can only be efficiency excited using an odd number of photons (1 or 3) while resonant two-photon excitation is strongly suppressed.

Abstract:

We demonstrate that a two-level system, in form of an InGaN quantum dot, can only be efficiency excited using an odd number of photons (1 or 3) while resonant two-photon excitation is strongly suppressed.