Emergence Of Directional Rotation In Optothermally Activated Colloidal System

We experimentally demonstrate the emergence of directional rotation in thermally active-passive colloidal structures under optical confinement. The observed handedness of rotation of the structure can be controlled by changing the relative position of the constituent colloids. We show that the angular velocity of rotation is sensitive to the intensity of the incident optical fields and the size of the constituent colloidal entities. The emergence of rotational dynamics can be understood in the context of asymmetric temperature distribution in the system and the relative location of the active colloid, which creates a local imbalance of optothermal torques to the confined system. Our work demonstrates how localized optothermal fields lead to directional rotational dynamics without explicitly utilizing spin or orbital angular momentum of light. We envisage that our results will have implications in realizing Brownian engines, and can directly relate to rotational dynamics in biological and ecological systems

Directional emission from WS2 monolayer coupled to plasmonic Nanowire-on-Mirror Cavity

Influencing spectral and directional features of exciton emission characteristics from 2D transition metal dichalcogenides by coupling it to plasmonic nano-cavities has emerged as an important prospect in nanophotonics of 2D materials. In this paper we experimentally study the directional photoluminescence emission from Tungsten disulfide (WS2) monolayer sandwiched between a single-crystalline plasmonic silver nanowire (AgNW) waveguide and a gold (Au) mirror, thus forming an AgNW-WS2-Au cavity. By employing polarization-resolved Fourier plane optical microscopy, we quantify the directional emission characteristics from the distal end of the AgNW-WS2-Au cavity. Given that our geometry simultaneously facilitates local field enhancement and waveguiding capability, we envisage its utility in 2D material-based, on-chip nanophotonic signal processing, including nonlinear and quantum optical regimes.Comment: To appear in Advanced Photonics Research (2021

Mirror-Coupled Microsphere can narrow the Angular distribution of Photoluminescence from WS2 Monolayers

Engineering optical emission from two dimensional, transition metal dichalcogenides (TMDs) materials such as Tungsten disulphide (WS2) has implications in creating and understanding nanophotonic sources. One of the challenges in controlling the optical emission from 2D materials is to achieve narrow angular spread using a simple photonic geometry. In this paper, we study how the photoluminescence of a monolayer WS2 can be controlled when coupled to film coupled microsphere dielectric antenna. Specifically, by employing Fourier plane microscopy and spectroscopic techniques, we quantify the wavevector distribution in the momentum space. As a result, we show beaming of the WS2 photoluminescence with angular divergence of {\theta}1/2 = 4.6{\deg}. Furthermore, the experimental measurements have been supported by three-dimensional numerical simulations. We envisage that the discussed results can be generalized to a variety of nanophotonic 2D materials, and can be harnessed in nonlinear and quantum technology

Optothermal Evolution of Active Colloidal Matter in a Defocused Laser Trap

Optothermal interaction of active colloidal matter can facilitate environmental cues, which can influence the dynamics of active soft matter systems. The optically induced thermal effect can be harnessed to study non-equilibrium thermodynamics as well as applied to self-propel colloids and form assemblies. In this work, we employ a defocused laser trap to form self-evolving colloidal active matter. The optothermal interaction of the active colloids in both focused and defocused optical traps has been investigated to ascertain their thermophoretic behavior, which shows a long-range attraction and a short-range repulsion between the colloids. The optical gradient field-enabled attraction and the short-range repulsion between the active colloids have been harnessed to form a re-configurable dynamic assembly. Additionally, the assembly undergoes self-evolution as a new colloid joins the structure. Further, we show that the incident polarization state of the optical field can be employed as a parameter to modulate the structural orientation of the active colloids. The simple defocused optical field-enabled assembly can serve as a model to understand the collective dynamics of active matter systems and can be harnessed as a re-configurable microscopic engine

Optothermal Evolution of Active Colloidal Matter in a Defocused Laser Trap

Optothermal interaction of active colloidal matter can facilitate environmental cues, which can influence the dynamics of active soft matter systems. The optically induced thermal effect can be harnessed to study non-equilibrium thermodynamics as well as applied to self-propel colloids and form assemblies. In this work, we employ a defocused laser trap to form self-evolving colloidal active matter. The optothermal interaction of the active colloids in both focused and defocused optical traps has been investigated to ascertain their thermophoretic behavior, which shows a long-range attraction and a short-range repulsion between the colloids. The optical gradient field-enabled attraction and the short-range repulsion between the active colloids have been harnessed to form a re-configurable dynamic assembly. Additionally, the assembly undergoes self-evolution as a new colloid joins the structure. Further, we show that the incident polarization state of the optical field can be employed as a parameter to modulate the structural orientation of the active colloids. The simple defocused optical field-enabled assembly can serve as a model to understand the collective dynamics of active matter systems and can be harnessed as a re-configurable microscopic engine

Optothermal Evolution of Active Colloidal Matter in a Defocused Laser Trap

Optothermal interaction of active colloidal matter can facilitate environmental cues, which can influence the dynamics of active soft matter systems. The optically induced thermal effect can be harnessed to study non-equilibrium thermodynamics as well as applied to self-propel colloids and form assemblies. In this work, we employ a defocused laser trap to form self-evolving colloidal active matter. The optothermal interaction of the active colloids in both focused and defocused optical traps has been investigated to ascertain their thermophoretic behavior, which shows a long-range attraction and a short-range repulsion between the colloids. The optical gradient field-enabled attraction and the short-range repulsion between the active colloids have been harnessed to form a re-configurable dynamic assembly. Additionally, the assembly undergoes self-evolution as a new colloid joins the structure. Further, we show that the incident polarization state of the optical field can be employed as a parameter to modulate the structural orientation of the active colloids. The simple defocused optical field-enabled assembly can serve as a model to understand the collective dynamics of active matter systems and can be harnessed as a re-configurable microscopic engine

Optothermal Evolution of Active Colloidal Matter in a Defocused Laser Trap

Optothermal interaction of active colloidal matter can facilitate environmental cues, which can influence the dynamics of active soft matter systems. The optically induced thermal effect can be harnessed to study non-equilibrium thermodynamics as well as applied to self-propel colloids and form assemblies. In this work, we employ a defocused laser trap to form self-evolving colloidal active matter. The optothermal interaction of the active colloids in both focused and defocused optical traps has been investigated to ascertain their thermophoretic behavior, which shows a long-range attraction and a short-range repulsion between the colloids. The optical gradient field-enabled attraction and the short-range repulsion between the active colloids have been harnessed to form a re-configurable dynamic assembly. Additionally, the assembly undergoes self-evolution as a new colloid joins the structure. Further, we show that the incident polarization state of the optical field can be employed as a parameter to modulate the structural orientation of the active colloids. The simple defocused optical field-enabled assembly can serve as a model to understand the collective dynamics of active matter systems and can be harnessed as a re-configurable microscopic engine