research-Nanophotonics

Research

Inorganic-Organic hybrids multiple qunatum wells
Photonics Structures for templated self assembly
Nanofunctional photonic composites and Self organised nano/mesa structures:
Silicon Photonics
Photonics of liquid crystals
Light-Matter interactions in Photonic architectures
Photonic glass waveguides and phosphors

Inorganic-Organic hybrids multiple qunatum wells:
Inorganic semiconductor and organic semiconductor nanolayers ( ~0.7-1.5nm width) are alternately stacked -up to form natural Inorganic-organic Multiple Quantum Wells (IO-MQWs). IO hybrids Here the semiconductor acts as a quantum well and organic as quantum barrier. One of the excellent property is they show strong room temperature exciton optical features with large exciton binding energy and oscillator strength due to the low dimensionality of the inorganic structure. In the recent years IO MQWs emerged as highly-promising systems for applications in optoelectronic devices, opening up also new dimensions to nanotechnology, as unique replacement to their inorganic and organic counterparts. Here we establish the fabrication strategies and study the photonic applications of these fascinating materials.

Photonics Structures for templated self assembly:
Micro and nano porous meta-materials can be fabricated from templated self-assembly followed by electrochemical deposition. Using this low-cost bottom-up fabrication technique, we can fabricate a range of sizes, from 50 nm to 50 μm, in both ordered and disordered fashions. With this method now it is possible for us to fabricate the strctures from wide range of metals ( Au,Ag, Pt, magnetic metals etc.,) and many semiconductors ( CdSe, CdTe, ZnO, PbO, PbI2, IOMQWs). These micro/nanostructures have potential applications such as tunable photonic, plasmonic and magnonic band gaps, novel types of liquid crystal displays, as well as for nanolaser cavities. This simple and effective method of fabrication paves a further way to engineer many structures of nano and micro dimensions and, most importantly, to integrate devices onto chips for further optoelectronic applications.

Nanofunctional photonic composites and Self organised nano/mesa structures:
nano In recent years, semiconductors nanomaterials have been explored worldwide for potential application as nanofunctional elements for number of photonic applications. Nanoporous composites produced from nanotemplates are one of the few classes of materials that are truly nanostructured in three dimensions. These materials show very promising as optoelectronic devices, such as solar cells, gas sensors, light emitting diodes and fast detectors. The current research under this area in our laboratory is focused on fabricating nanofunctional photonic composites from different routes.

Silicon Photonics:
Silicon Photonics concerns that field of photonics which aims at the confinement and control of photons using devices (both passive and active) made of Silicon based materials, which can be integrated onto Silicon wafers together with electronic integrated circuits. Such circuits would be called Opto-Electronic Integrated Circuits (OEICs). Development of such circuits would lead to an immense increase in the communication bandwidth and speed. We aim to achieve control on the growth of silicon nanoclusters in silicon nitride (Si3N4) matrix. Currently, we are employing both structural and optical approaches to characterise the presence/growth of these Silicon nanostructures in Silicon Nitride of different stoichiometries. Further, we are also studying the tunability of room-temperature photoluminescence (PL) from as-deposited Si-rich hydrogenated amorphous silicon nitride (a-SiNx:H) thin films to establish a Si-based full-color emitter and correlate PL to influential factors such as the presence of different phases (SiOxNy, SiO2, SiNx and Si) and the inadvertent presence of hydrogen in a-SiNx:H films.

Photonics of liquid crystals:
Liquid crystals (LCs) are very fascinating opto-electronic materials due to their electrically/thermally tunable photonic features (refractive index, transmission, reflection, and etc.) promising for versatile LCs-based tunable devices such as filters, phase/amplitude modulators, lenses, mirror-less lasers, and so on. Currently, we are working on different types of LCs (nematic, biaxial nematic, and ferroelectric) to harness their tunable photonic features at greater scale. The doping of nanomaterials and isotropic fluids into various LCs are also taken up, to study the enhanced photonic effects and to explore futuristic LCs-nanocomposites-based photonic devices.

Light-Matter interactions in Photonic architectures:
In general, there are two regimes into which interactions between an electromagnetic field and the optical transitions of a material (exciton) could be classified, namely, weak and strong-coupling. Weak coupling comes into picture when the spectral and spatial distribution of emission from the exciton is modified but the dynamics are almost unaltered. Whereas, in strong coupling both the exciton and photon states are mixed-up and, as a consequence strongly modified dynamics occurs. Controlling of light-matter interactions could be responsible for enhancement and tuned photonic behavior of hybrid materials. Light matter interaction of laser dyes (emitter) inside porous silicon architectures has shown by our group successfully along with tuning effect of properties. Modification in properties is due to weak interaction which can be described by Fermi golden rules.

Strong-coupling manifests itself in anti-crossing of the coupled modes, ideally, in the appearance on strong coupling resonance of two equal intensity and equal line width transitions separated by the vacuum Rabi splitting energy. These new cavity polariton modes can be considered an admixture of material optical transitions and the cavity photon modes. Strong-coupling effects for inorganic semiconductor quantum well microcavities are the subject of intense scientific interest and offer new possibilities for the modification and control of exciton-photon interactions. The coupled cavity-polariton states are, for instance, of huge interest for polariton lasing.

Photonic glass waveguides and phosphors:
Our current research is intended to realize a compact, highly performing and low cost waveguide from phand glass specific low-melting glass systems doped with Er and co-doped with other energy transfer rareearths,. Using those methods, that are compatible with industrial implementation, our research, will endeavor to optimize the conditions, to explore the systems and to identify the most viable approach to achieve the best material for the waveguides. Ultimately, we aim at the development of a glass waveguide an incoherent broad band source for telecommunication purposes.
We are also working on different types of inorganic nano phosphors for photonic applications. Here we focus on efficient red, green and white-light emission studies from rareearth doped inorganic phosphors.