Structured light provides an additional degree of freedom for modern optics and practical applications. The effective generation of orbital angular momentum (OAM) lasing, especially at a micro- and nanoscale, could address the growing demand for information capacity. By exploiting the emerging non-Hermitian photonics design at an exceptional point, we demonstrate a microring laser producing a single-mode OAM vortex lasing with the ability to precisely define the topological charge of the OAM mode. The polarization associated with OAM lasing can be further manipulated on demand, creating a radially polarized vortex emission. Our OAM microlaser could find applications in the next generation of integrated optoelectronic devices for optical communications in both quantum and classical regimes.

The orbital angular momentum (OAM) intrinsically carried by vortex light beams holds a promise for multidimensional high-capacity data multiplexing, meeting the ever-increasing demands for information. Development of a dynamically tunable OAM light source is a critical step in the realization of OAM modulation and multiplexing. By harnessing the properties of total momentum conservation, spin-orbit interaction, and optical non-Hermitian symmetry breaking, we demonstrate an OAM-tunable vortex microlaser, providing chiral light states of variable topological charges at a single telecommunication wavelength. The scheme of the non–Hermitian-controlled chiral light emission at room temperature can be further scaled up for simultaneous multivortex emissions in a flexible manner. Our work provides a route for the development of the next generation of multidimensional OAM-spin-wavelength division multiplexing technology.

to sluggish actuation speed (response time typically on the order of minutes). Conventional one-way SMPs do not remember the temporary shapes and the recovery speed is relatively slow (response time from tens of seconds to minutes) since it is heat-activated. LCEs, in contrast, owning to their inherent anisotropy, offer promises for fast (e.g., 10 ms [11]) and reversible actuation, large actuation strain, and high energy conversion efficiency. [12] LCEs are lightly crosslinked polymer networks containing main-chain or sidechain mesogenic units. [13] The deformation

Applications that use the orbital angular momentum (OAM) of light show promise for increasing the bandwidth of optical communication networks. However, direct photocurrent detection of different OAM modes has not yet been demonstrated. Most studies of current responses to electromagnetic fields have focused on optical intensity–related effects, but phase information has been lost. In this study, we designed a photodetector based on tungsten ditelluride (WTe2) with carefully fabricated electrode geometries to facilitate direct characterization of the topological charge of OAM of light. This orbital photogalvanic effect, driven by the helical phase gradient, is distinguished by a current winding around the optical beam axis with a magnitude proportional to its quantized OAM mode number. Our study provides a route to develop on-chip detection of optical OAM modes, which can enable the development of next-generation photonic circuits.

Light-light switching typically requires strong nonlinearity where intense laser fields route and direct data flows of weak power, leading to a high power consumption that limits its practical use. Here we report an experimental demonstration of a metawaveguide that operates exactly in the opposite way in a linear regime, where an intense laser field is interferometrically manipulated on demand by a weak control beam with a modulation extinction ratio up to approximately 60 dB. This asymmetric control results from operating near an exceptional point of the scattering matrix, which gives rise to intrinsic asymmetric reflections of the metawaveguide through delicate interplay between index and absorption. The designed metawaveguide promises low-power interferometric light-light switching for the next generation of optical devices and networks. DOI: 10.1103/PhysRevLett.117.193901 Effective light-light switching promises optical information processing, which has been a long-standing driving force for high-speed and energy-efficient optical networks. Strong optical modulations are initiated in nonlinear optical media by intense laser fields to enable switching of a weak signal, for example, intensity modulation of light by light has been demonstrated based on the all-optical Kerr effect [1][2][3][4][5][6]. Nevertheless, the high power requirement for the intense control or pump light becomes a significant barrier for practical applications. While cavity quantum electrodynamics displays nonlinear optical effects on a few-photon level [7,8], its application as a robust optical element operating in the classical regime remains still unclear. On the other hand, a recent pioneering investigation of exploiting photonics absorption offered a unique linear scheme to efficiently control light by light utilizing mutually coherent interaction of light beams and absorbing matters [9,10], by which coherent perfect absorption (CPA) was demonstrated [11][12][13][14]. While this linear strategy reduces the power requirement, the control beam still has a similar amount of power as the actual source signal in these previous works, due to the rather symmetric optical scatterings in the optical implementations.The recent emergence of non-Hermitian photonic metamaterials offers a new paradigm to explore nanophotonics and metamaterials research in the entire complex dielectric permittivity plane, based on parity-time (PT) symmetry [15][16][17][18][19][20]. Attractive physical phenomena including phase transitions and exceptional points are emulated with photonics, consequently, leading to novel effective manipulation of cavity lasing modes [21][22][23][24][25][26] and unidirectional light transport [27][28][29][30][31][32]. Here, we will show a unique metawaveguide of potential for on-demand control of interferometric light-light switching can be realized through non-Hermitian metamaterial explorations.An intriguing characteristic of non-Hermitian photonic metamaterials is their intrinsic asymmetry near an exceptional point. For PT sym...