Junliang Jia

Tailoring the angular distribution of thermal emission is crucial for applications in space thermal management, infrared stealth, and energy systems. The inverse design of nonlocal metasurfaces remains challenging due to the high-dimensional parameter space and computationally expensive full wave simulations. This work presents and experimentally validates an efficient, deep learning driven inverse design platform for nonlocal thermal photonic metasurfaces with customized directional emissivity. First, by applying particle swarm optimization (PSO) to introduce perturbations to a bound state in the continuum (BIC) metasurface, we demonstrate precise control over the angular emissivity profile within a ±60° range. Fourier-transform infrared spectroscopy and long wave infrared thermal imaging confirm the intended asymmetric emission, showing excellent agreement between experiments and simulations. To overcome the limited design freedom of perturbation-based strategies, we further develop a global optimization framework. It employs Non-Uniform Rational B-Splines (NURBS) for high-degree-of-freedom meta-atom parameterization, accelerated by an end-to-end deep learning surrogate model linked to spatiotemporal coupled-mode theory (STCMT). This differentiable surrogate bypasses repetitive full-wave simulations and enables efficient gradient based optimization without adjoint methods. Metasurfaces fabricated using this workflow exhibit thermal emissivity profiles at 150°C in excellent agreement with predictions, achieving a normalized root mean square error below 0.1. This work demonstrates a robust and scalable platform for the inverse design of high performance nonlocal thermal metasurfaces with complex spectral-angular responses.

The rotational Doppler effect (RDE) attracts much attention in various research areas, from acoustics to optics. The observation of RDE mostly depends on the orbital angular momentum of the probe beam, while the impression of radial mode is ambiguous. To clarify the role of radial modes in RDE detection, we reveal the mechanism of interaction between probe beams and rotating objects based on complete Laguerre-Gaussian (LG) modes. It is theoretically and experimentally proved that radial LG modes play a crucial role in RDE observation because of topological spectroscopic orthogonality between probe beams and objects. We enhance the probe beam by employing multiple radial LG modes, which makes the RDE detection sensitive to objects containing complicated radial structures. In addition, a specific method to estimate the efficiency of various probe beams is proposed. This work has the potential to modify RDE detection method and take the related applications to a new platform.

An arbitrary lossless transformation in high-dimensional (HD) quantum space can be decomposed into elementary operations which are easy to implement, and an effective decomposition algorithm is important for constructing HD systems. Here, we present two optimized architectures to effectively realize an arbitrary unitary transformation by using the photonic path and polarization based on the existing decomposition algorithm. In the first architecture, the number of required interferometers is reduced by half compared with previous works. In the second architecture, by using the HD X gate, all the elementary operations are transferred to the operations which act locally on the photonic polarization in the same path. Such an architecture could be of significance in polarization-based applications. Both architectures maintain the symmetric layout. Our work facilitates the optical implementation of HD transformations and could have potential applications in HD quantum computation and quantum communication.

The recently proposed mutually partially unbiased bases (MPUB)–based protocol, which encodes with Laguerre–Gaussian modes and Hermite–Gaussian modes of the same mode order, can close the security loophole caused by state-dependent diffraction. However, its pessimistic security proof limits the performance, and some practical issues, such as finite-key size and imperfect sources, have not been considered. Here, we improve the key rates of the MPUB-based protocol by accurately estimating the phase error rate. Moreover, the effect of finite-key size and its performance when combined with the decoy state method are demonstrated. Our work broadens the application scope of the MPUB-based protocol, and thereby advances the development of high-dimensional quantum key distribution using spatial modes.

Perfect optical vortex (POV) beams have attracted extensive attention because they have the advantage of a radial profile that is independent of orbital angular momentum. To date, it is usually obtained by means of the Fourier transform performed by a lens on Bessel beams. We theoretically and experimentally demonstrate that POV can be generated by performing the Fourier transform on Laguerre–Gauss beams with a high-order radial index. Furthermore, we derive an analytical expression for the increase in vortex radius, which is beneficial to compensate for the influence of the radius change in actual experiments. Our results may shed new light for a variety of research utilizing POV.

Cylindrical vector beams (CVBs) detection is of vital significance in various kinds of studies such as particle observation and mode‐division multiplexing (MDM). Herein, a comprehensive detection of CVBs based on the rotational Doppler effect (RDE) including analysis of topological charge (TC), relative amplitude module, and phase for superimposed mode bases is realized. A mode demultiplexing scheme is constructed through the complex amplitude of the harmonic terms in the beating signal. The method resolves both absolute values and signs of the TC of CVB simultaneously, which cannot be simply realized by existing polarization examination techniques. It may be of big potential in related research since an efficient, quantitative, and complete scheme to detect CVBs is verified starting from this work.

The rotational Doppler effect has attracted extensive attention, caused by the angular momentum and energy exchange between rotating objects and waves. However, most previous works used a simple rotation frame, which made use of only a single-round angular momentum and energy exchange. We propose and demonstrate a frame containing a spiral phase plate cascaded with rotating targets to make an amplification of the traditional Doppler shift, and reduce the diffusion of orbital angular momentum modes by half, which means the distance of practical application is doubled theoretically. To this end, an experiment is carried out to verify the frame. It shows a more practical, convenient, and non-destructive method to measure the rotational speed of a remote target.

Cylindrical vector beams (CVBs), which possess polarization distribution of rotational symmetry on the transverse plane, can be developed in many optical technologies. Conventional methods to generate CVBs contain redundant interferometers or need to switch among diverse elements, thus being inconvenient in applications containing multiple CVBs. Here we provide a passive polarization-selective device to substitute interferometers and simplify generation setup. It is accomplished by reversing topological charges of orbital angular momentum based on a polarization-selective Gouy phase. In the process, tunable input light is the only condition to generate a CVB with arbitrary topological charges. To cover both azimuthal and radial parameters of CVBs, we express the mapping between scalar Laguerre–Gaussian light on a basic Poincaré sphere and CVB on a high-order Poincaré sphere. The proposed device simplifies the generation of CVBs enormously and thus has potential in integrated devices for both quantum and classic optical experiments.