Professor Animesh Jha is a full-time professor of materials science at the University of Leeds. His main research interests is in the areas of Photonic Materials and Devices and Light-Matter Interaction and applications of such processes in device engineering. The above topic manifests AJ’s interest which he has taken forward for exploring a range of application in collaboration with two established laboratories in India.

AJ obtained his BE (Metallurgy) in 1979 (University of Roorkee, India), ME (Metallurgical Engineering) in 1981 from the Indian Institute of Science Bangalore (India) , and PhD and DIC from Imperial College London in 1984.

Professor Animesh Jha

S P. Tekale, R P. Panmand, K D. Daware, S W. Gosavi , B B. Kale, N Petrou, M El-Murish, J G Addis, C Maddi, Animesh Jhac,*

Semiconductor quantum dots (QDs), with Bohr excitonic radii exhibit discrete energy levels. Such QDs are well below 10nm in size for demonstrating size dependent resonance band in the visible and near-IR spectrum. The QDs size range in a glass host offer opportunity for tuning the oscillator strength and confinement effects, which may promote efficient optical transitions and the control of spin states, especially if the QDs are engineered with 4fn-electron and partially occupied d-states; e.g. in transition metal ions.

On the basis of the knowledge of the 4f- and d-state electronic and spin transitions, there may be possibilities for exploring novel optical and spin for applications in solar energy harvesting, fluorescent light and laser device engineering, and in electromagnetic Faraday sensor engineering for current and electric and magnetic field measurements. It is in such an application-rich context our International Research Collaboration with India has been set up with support from the Royal Society, London. In this research, we have been investigating the spectroscopic properties of rare-earth and transition-metal ion doping of CdS quantum dots, dispersed in a silicate glass matrix. We have studied the incorporation of Mn2+ and Tb3+ in CdS-QD containing silicate glasses, and have compared the spectroscopic properties with the corresponding standard rare-earth doped glass systems without CdS -QDs, for comparing and analysing the energy states, and also for the exchange mechanism when the ground states are excited with a coherent pump source in ultra-violet and visible range. The influence of controlling the QD-structures in (Tb3+:CdS) and (Mn2+:CdS) via glass melting, quenching and annealing after casting is discussed for controlling the absorption and fluorescence emission properties. The effects of heat treatment on the absorption and emission properties of CdS and Mn2+-doped CdS, for example, are compared in Figures 1 and 2, respectively. The corresponding colour changes due to the shift in the resonance bands are apparent in Figure 3 as a result of heat treatment.

The effect of the QD size on the luminescence properties of CdS and Mn2+/Tb3+-doped CdS have been studied in detail. The absorption and emission spectroscopic studies were analysed in the time resolved regime for both the Mn2+ and Tb3+-containing QD CdS. The enhancement in the spectroscopic properties, underpinned by energy exchange mechanism amongst the states present in Q-dots of CdS, Mn2+ and Tb3+ ions, is explained. The effect of QD CdS with Mn2+, Mn2+/Tb3+-doped on the magneto-optical Faraday rotation has also been investigated using the Faraday rotation measurements, which showed marked enhancement in the values of Verdet constant in Mn2+/Tb3+ doped CdS containing QD glasses. These results demonstrate the engineered materials might be suitable as a magneto-optical device for polarisation control.

Figure 1: a) and b) compare the room-temperature absorption spectra of CdS and Mn2+-doped CdS glasses.

Figure 2: a) and b) are the room temperature photoluminescence spectra of CdS and Mn2+-doped CdS glasses.
Figure 3: a) and b) compare the colour changes in the as-cast and annealed glass samples at different temperatures.