The generation of high-purity localized trions, dynamic exciton-trion interconversion, and their spatial modulation in two-dimensional (2D) semiconductors are building blocks for the realization of trion-based optoelectronic devices. Here, we present a method for the all-optical control of the exciton-to-trion conversion process and its spatial distributions in a MoS monolayer. We induce a nanoscale strain gradient in a 2D crystal transferred on a lateral metal-insulator-metal (MIM) waveguide and exploit propagating surface plasmon polaritons (SPPs) to localize hot electrons. These significantly increase the electrons and efficiently funnel excitons in the lateral MIM waveguide, facilitating complete exciton-to-trion conversion even at ambient conditions. Additionally, we modulate the SPP mode using adaptive wavefront shaping, enabling all-optical control of the exciton-to-trion conversion rate and trion distribution in a reversible manner. Our work provides a platform for harnessing excitonic quasiparticles efficiently in the form of trions at ambient conditions, enabling high-efficiency photoconversion.
Effectively controlling exciton-polaritons is crucial for advancing them in optical computation. In this work, we propose utilizing the valley-selective optical Stark effect (OSE) as an all-optical way to achieve the spatiotemporal control of polariton flow. We demonstrate the polarization-selective concentration of polaritons at pre-determined locations by wavefront shaping of the polaritons through an in-plane bar-code potential induced by the OSE, which helps overcome the intra-cavity disorder in potential distribution.
Ultrafast all-optical control has been a subject of wide-spread attention as a method of manipulating optical fields using light excitation on extremely short time scales. As a fundamental form of ultrafast all-optical control, all-optical switching has achieved sub-picosecond switch speeds in the visible, infrared, and terahertz spectral regions. However, due to the lack of suitable materials, ultrafast all-optical control in the ultraviolet range remains in its early stages.
Manipulating the thermal emission in the infrared (IR) range significantly impacts both fundamental scientific research and various technological applications, including IR thermal camouflage, information encryption, and radiative cooling. While prior research has put forth numerous materials and structures for these objectives, the significant challenge lies in attaining spatially resolved and dynamically multilevel control over their thermal emissions. In this study, a one-step ultrafast laser writing technique is experimentally demonstrated to achieve position-selective control over thermal emission based on the phase-change material GeSbTe (GST).
We demonstrate a mechanical crystal with an optically programmable defect mode. By applying an optical spring to a single unit cell of a phononic crystal membrane, we smoothly transfer a single mechanical mode into the band gap, thereby localizing its spatial profile from one spanning the entire crystal to one confined within a few unit cells. This localization is evidenced by an enhanced mechanical frequency shift commensurate with a 37-fold reduction in the mode's participating mass.
Quantum walks (QW) offer a speed-up advantage over random walks in quantum search applications. We present an experimental study of the transition from quantum-to-classical random walk using an emulation of the decoherence process for polarization qubits that exploits maximally non-separable spin-orbit modes of an intense laser beam for the first, to the best of our knowledge, time. We are able to continuously control the input polarization mode in an all-optical quantum walk circuit to observe transitions associated with quantum, quantum stochastic, and classical random walk distributions.
