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The temporally switchable optical mode conversion is crucial for optical communication and computing applications. This research demonstrates such optically switchable mode converter driven by thermo-optic refraction. The MoS2 nanofluid is used as a medium where the thermal microlens is created by a focused laser beam (pump). The convective thermal plume generated above the focal point of the pump beam within the nanofluid acts as an astigmatic thermal lens. It is discovered that mode conversion of the Laguerre-Gaussian (LG) to the Hermite-Gaussian (HG) beam (vice versa) takes place upon passing through the thermal lens. The topological charge of the LG beam can be easily determined using the proposed mode converter. The mode transformation is explained theoretically as the Fourier components of the LG beam undergoing different optical paths while propagating through the convective plume.

In heat transportation applications, water is most commonly used fluid. The efficiency of equipment used in these applications depends on thermal characteristics of water used. The thermal characteristics of water could be upgraded by suspending high thermal conducting solid nanoparticles. In this paper an attempt has been made to know how the use of surfactants and functionalization of carbon nanotube walls can affect the thermal characteristics and stability of nanofluid. A thorough analysis of collected literature revealed that carbon nanotubes have much higher thermal conductivity than any other nanoparticles and hence improve the thermal properties of water when suspended in them. Further it is concluded that suspension of carbon nanotubes in water requires use of surfactant or functionalization of carbon nanotube walls with proper group. By setting optimum pH and better dispersion, better thermal conductivity is possible. Experimental studies in the literature survey reveal that chemical stabilization techniques and physical stabilization techniques together decide the stability of the nanofluid.

Common path interferometers (CPI) are significant due to their compactness and vibration resistance. The usual challenge in CPI would arise due to a very small separation between reference and sample beams, where sending a reference beam through a sample is considered as a limitation. But this limitation also makes it difficult to probe the interaction of beams with material as a function of their phase structure. This study can pave the way for a new kind of interferometry that can provide unique phase signatures to study the sample. The paper proposes and demonstrates a novel approach based on thermo-optic refraction, to send both beams through the sample and probe the phase deterioration due to the relative interaction of beams in the material medium. Here, thermo-optic refraction interferometry (TORI) allows the superposition of a higher order vortex beam with a non-vortex beam through the phenomenon of thermal lensing. The non-vortex beam is made to expand in a controlled fashion by another laser. The relative interaction of the expanding non-vortex beam and the vortex beam within the sample, results in the output interferogram. The phase deterioration analysis of the output interferogram elucidate medium driven phase changes. This technique is demonstrated using the milk samples by recording the RMS azimuthal phase deterioration of the OAM beam.