Controlling the density of exciton and trion quasiparticles in monolayer two-dimensional (2D) materials at room temperature by nondestructive techniques is highly desired for the development of future optoelectronic devices. Here, the effects of different orbital angular momentum (OAM) lights on monolayer tungsten disulfide at both room temperature and low temperatures are investigated, which reveal simultaneously enhanced exciton intensity and suppressed trion intensity in the photoluminescence spectra with increasing topological charge of the OAM light. In addition, the trion-to-exciton conversion efficiency is found to increase rapidly with the OAM light at low laser power and decrease with increasing power. Moreover, the trion binding energy and the concentration of unbound electrons are estimated, which shed light on how these quantities depend on OAM. A phenomenological model is proposed to account for the experimental data. These findings pave a way toward manipulating the exciton emission in 2D materials with OAM light for optoelectronic applications.

It is theoretically demonstrated that the planar geometric mode with a π/2 mode converter, so called the circularly geometric mode, can be solved from the inhomogeneous Helmholtz equation by considering the pump distribution on the lasing mode. Theoretical analysis clearly reveal that the vortex structures of circularly geometric modes are determined by the minimum order of transverse lasing modes, the total number of transverse lasing modes and the degenerate condition in the cavity. Moreover, we experimentally manifest that the circularly geometric mode can be generated from the selective pumped solid-state laser with an external π/2 mode converter. To explore the vortex structures of the generated geometric modes, the interference patterns are performed by an experimental apparatus consisting of a Mach-Zehnder interferometer. The good agreement between experimental observations and numerical calculations confirms the analysis of vortex structures is reliable.

We experimentally demonstrate that the near-field patterns of conical second harmonic generation of a laser in random domain structures can be used to explore the spatial structure of two-dimensional disordered wave functions with weak localization. The statistics of the experimental near-field patterns agree very well with the theoretical distributions. In addition to the short-range correlation, the localization effects are found to contribute a nearly constant value to the long-range correlation. The result of this Letter also confirms the possibility of using conical second harmonic generation as a diagnostic tool for topographical characterization of crystals.

We investigate the quantum signatures of classical nonlinear resonances by making the analytic connection between the quantum wave functions and the classical periodic orbits for the uncoupled systems. It is found that the highly efficient extension of the localized coherent states within the classical caustics is an intriguing phenomenon in mesoscopic systems with nonlinear resonances. With the theoretical analysis, we experimentally demonstrate that the laser resonator with an intracavity saturable absorber can be employed to visualize the wave patterns analogous to the quantum wave functions associated with Fermi resonance.

The propagation-dependent polarization vector fields are experimentally created from an isotropic microchip laser with a longitudinal-transverse coupling and entanglement of the polarization states. The experimental three-dimensional coherent vector fields are analytically reconstructed with a coherent superposition of orthogonal circularly polarized vortex modes. Each polarized component is found to comprise two Laguerre-Gaussian modes with different topological charges. With the analytical representation, the polarization singularities, on which the electric polarization ellipse is purely circular (C lines) or purely linear (L surfaces), are explored. The C line singularities are found to form an intriguing hyperboloidal structure.

We theoretically demonstrate that the three-dimensional (3D) coherent laser waves formed by the degenerate Laguerre-Gaussian modes with different longitudinal indices are well localized on rotating trochoidal parametric surfaces. We further use a large-Fresnel-number laser system to realize the existence of the laser modes related to trochoidal coherent states. Experimental results reveal that the exotic laser modes generally originate from a superposition of two degenerate standing-wave trochoidal coherent states.

We present experimental observations of polarization vector fields from a highly isotropic microchip laser with a large Fresnel number. The experimental polarization vector field leads to complex entanglement of spatial structures and polarization states. We theoretically derive the representation of generalized coherent states to reconstruct the experimental polarization-resolved patterns. The analytical and precise reconstruction enables the vector singularities to be clearly visualized.

We demonstrate experimental generation of two-dimensional (2D) chaotic vector fields from a surface-emitting microcavity laser with precisely control of the operating temperature and the operating current. The 2D optical vector field is found to be formed by frequency locking of two linearly polarized laser modes with different chaotic spatial structures. The eigenfunction expansion method is used to reconstruct the experimental wave function for analyzing the properties of the vector singularities. It is shown that the distribution of vector singularities obeys the sign rule of nearest-neighbor singularities in the phase space of the vector field.