An interview with Prof. Michal Lipson by Prof. Guoqing Chang traces Lipson’s professional pathway in the field of silicon photonics.

Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer. In the case of 3D trapping with a single beam, this is termed optical tweezers. Optical tweezers are a powerful and noninvasive tool for manipulating small objects, and have become indispensable in many fields, including physics, biology, soft condensed matter, among others. In the early days, optical trapping was typically accomplished with a single Gaussian beam. In recent years, we have witnessed rapid progress in the use of structured light beams with customized phase, amplitude, and polarization in optical trapping. Unusual beam properties, such as phase singularities on-axis and propagation invariant nature, have opened up novel capabilities to the study of micromanipulation in liquid, air, and vacuum. We summarize the recent advances in the field of optical trapping using structured light beams.

In the past decade, lead halide perovskites have emerged as potential optoelectronic materials in the fields of light-emitting diode, solar cell, photodetector, and laser, due to their low-cost synthesis method, tunable bandgap, high quantum yield, large absorption, gain coefficient, and low trap-state densities. In this review, we present a comprehensive discussion of lead halide perovskite applications, with an emphasis on recent advances in synthetic strategies, morphology control, and lasing performance. In particular, the synthetic strategies of solution and vapor progress and the morphology control of perovskite nanocrystals are reviewed. Furthermore, we systematically discuss the latest development of perovskite laser with various fundamental performances, which are highly dependent on the dimension and size of nanocrystals. Finally, considering current challenges and perspectives on the development of lead halide perovskite nanocrystals, we provide an outlook on achieving high-quality lead perovskite lasers and expanding their practical applications.

Tunneling ionization of atoms and molecules induced by intense laser pulses contains the contributions of numerous quantum orbits. Identifying the contributions of these orbits is crucial for exploring the application of tunneling and for understanding various tunneling-triggered strong-field phenomena. We perform a combined experimental and theoretical study to identify the relative contributions of the quantum orbits corresponding to the electrons tunneling ionized during the adjacent rising and falling quarter cycles of the electric field of the laser pulse. In our scheme, a perturbative second-harmonic field is added to the fundamental driving field. By analyzing the relative phase dependence of the signal in the photoelectron momentum distribution, the relative contributions of these two orbits are unambiguously determined. Our results show that their relative contributions sensitively depend on the longitudinal momentum and modulate with the transverse momentum of the photoelectron, which is attributed to the interference of the electron wave packets of the long orbit. The relative contributions of these orbits resolved here are important for the application of strong-field tunneling ionization as a photoelectron spectroscopy for attosecond time-resolved measurements.

The unidirectional excitation of near-field optical modes is a fundamental prerequisite for many photonic applications, such as wireless power transfer and information communications. We experimentally construct all-electric Huygens and spin metasources and demonstrate anomalous unidirectional excitation of high-k hyperbolic modes in two types of hyperbolic metasurfaces. We use a Huygens metasource to study the unidirectional excitation of hyperbolic bulk modes in a planar hyperbolic metamaterial (HMM). Specifically, unidirectional excitation is the same as that in free space in the vertical direction, but opposite to that in free space in the horizontal direction. This anomalous unidirectional excitation is determined by the anisotropic HMM dispersion. In addition, we use a spin metasource to observe the anomalous photonic spin Hall effect in a planar hyperbolic waveguide. For a near-field source with a specific spin, the guide mode with a fixed directional wave vector is excited due to spin-momentum locking. Because the directions of momentum and energy flows in the HMM waveguide are opposite, the unidirectional excitation of hyperbolic guided modes is reversed. Our results not only uncover the sophisticated electromagnetic functionalities of metasources in the near-field but may also provide novel opportunities for the development of integrated optical devices.

Infrared imaging is a crucial technique in a multitude of applications, including night vision, autonomous vehicle navigation, optical tomography, and food quality control. Conventional infrared imaging technologies, however, require the use of materials such as narrow bandgap semiconductors, which are sensitive to thermal noise and often require cryogenic cooling. We demonstrate a compact all-optical alternative to perform infrared imaging in a metasurface composed of GaAs semiconductor nanoantennas, using a nonlinear wave-mixing process. We experimentally show the upconversion of short-wave infrared wavelengths via the coherent parametric process of sum-frequency generation. In this process, an infrared image of a target is mixed inside the metasurface with a strong pump beam, translating the image from the infrared to the visible in a nanoscale ultrathin imaging device. Our results open up new opportunities for the development of compact infrared imaging devices with applications in infrared vision and life sciences.

Dynamically controlling terahertz (THz) wavefronts in a designable fashion is highly desired in practice. However, available methods working at microwave frequencies do not work well in the THz regime due to lacking suitable tunable elements with submicrometer sizes. Here, instead of locally controlling individual meta-atoms in a THz metasurface, we show that rotating different layers (each exhibiting a particular phase profile) in a cascaded metadevice at different speeds can dynamically change the effective Jones-matrix property of the whole device, thus enabling extraordinary manipulations on the wavefront and polarization characteristics of a THz beam impinging on the device. After illustrating our strategy based on model calculations, we experimentally demonstrate two proof-of-concept metadevices, each consisting of two carefully designed all-silicon transmissive metasurfaces exhibiting different phase profiles. Rotating two metasurfaces inside the fabricated devices at different speeds, we experimentally demonstrate that the first metadevice can efficiently redirect a normally incident THz beam to scan over a wide solid-angle range, while the second one can dynamically manipulate both the wavefront and polarization of a THz beam. Our results pave the way to achieving dynamic control of THz beams, which is useful in many applications, such as THz radar, and bio- and chemical sensing and imaging.