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The latest applications in ultrafast quantum metrology require bright, broadband bi-photon sources with one of the photons in the mid-infrared and the other in the visible to near infrared. However, existing sources based on bulk crystals are limited in brightness due to the short interaction length and only allow for limited dispersion engineering. Here, we present an integrated PDC source based on a Ti:LiNbO 3 waveguide that generates broadband bi-photons with central wavelengths at 860 nm and 2800 nm . Their spectral bandwidth exceeds 25 THz and is achieved by simultaneous matching of the group velocities (GVs) and cancellation of GV dispersion for the signal and idler field. We provide an intuitive understanding of the process by studying our source’s behavior at different temperatures and pump wavelengths, which agrees well with simulations.

Catenary functions are exciting and fundamental building blocks in constructing various kinds of waves in subwavelength structures. Here, a simple yet powerful approach inspired by catenary optics is proposed to realize efficient manipulation of electromagnetic waves in terms of both amplitude and phase. By properly engineering the catenary electromagnetic fields and frequency dispersion, lightweight metafilm‐based broadband absorbers with polarization‐independent bandwidth covering 0.65–6.2 GHz are experimentally achieved, and the bandwidth is further broadened to 0.9–40 GHz. With the same approach, a large‐scale flat antenna based on generalized reflection is demonstrated in the satellite communication system. To enable the batch manufacturing, a flexible substrate–based microfabrication process is developed with a minimum feature size of down to sub‐micrometer and total size up to almost 1 m. These results may provide important guidance for the design of metasurface‐based devices. A systematic, general way to achieve efficient design of flat electromagnetic devices based on the catenary model is demonstrated. By employing the proposed method, broadband absorbers and flat antennas are experimentally achieved with lightweight properties and higher efficiencies compared with their traditional counterparts. Besides, a film‐based microfabrication process is developed to enable batch manufacturing for these devices.

Chromatic dispersion engineering of photonic waveguide is of great importance for Photonic Integrated Circuit in broad applications, including on-chip CD compensation, supercontinuum generation, Kerr-comb generation, micro resonator and mode-locked laser. Linear propagation behavior and nonlinear effects of the light wave can be manipulated by engineering CD, in order to manipulate the temporal shape and frequency spectrum. Therefore, agile shapes of dispersion profiles, including typically wideband flat dispersion, are highly desired among various applications. In this study, we demonstrate a novel method for agile dispersion engineering of integrated photonic waveguide. Based on a horizontal double-slot structure, we obtained agile dispersion shapes, including broadband low dispersion, constant dispersion and slope-maintained linear dispersion. The proposed inverse design method is objectively-motivated and automation-supported. Dispersion in the range of 0–1.5 ps/(nm·km) for 861-nm bandwidth has been achieved, which shows superior performance for broadband low dispersion. Numerical simulation of the Kerr frequency comb was carried out utilizing the obtained dispersion shapes and a comb spectrum for 1068-nm bandwidth with a 20-dB power variation was generated. Significant potential for integrated photonic design automation can be expected.

Designing and engineering microresonator dispersion are essential for generating microresonator frequency comb. Microresonator frequency combs (microcombs, Kerr frequency combs) offer the potential for various attractive applications as a new type of coherent light source that is power efficient and compact and has a high repetition rate and a broad bandwidth. They are easily driven with a continuous-wave pump laser with adequate frequency tuning; however, the resonators must have a high quality ( ) factor and suitable dispersion. The emergence of cavity enhanced four-wave mixing, which is based on third-order susceptibility in the host material, results in the generation of broadband and coherent optical frequency combs in the frequency domain equivalent to an optical pulse in the time domain. The platforms on which Kerr frequency combs can be observed have been developed, thanks to intensive efforts by many researchers over a few decades. Ultrahigh- whispering gallery mode (WGM) microresonators are one of the major platforms since they can be made of a wide range of material including silica glass, fluoride crystals and semiconductors. In this review, we focus on the dispersion engineering of WGM microresonators by designing the geometry of the resonators based on numerical simulation. In addition, we discuss experimental methods for measuring resonator dispersion. Finally, we describe experimental results for Kerr frequency combs where second- and higher-order dispersions influence their optical spectra.

We report the experimental observation of a trapped rainbow in adiabatically graded metallic gratings, designed to validate theoretical predictions for this unique plasmonic structure. One-dimensional graded nanogratings were fabricated and their surface dispersion properties tailored by varying the grating groove depth, whose dimensions were confirmed by atomic force microscopy. Tunable plasmonic bandgaps were observed experimentally, and direct optical measurements on graded grating structures show that light of different wavelengths in the 500-700-nm region is \"trapped\" at different positions along the grating, consistent with computer simulations, thus verifying the \"rainbow\" trapping effect.

Flexible dispersion manipulation is critical for holography to achieve broadband imaging or frequency division multiplexing. Within this context, metasurface-based holography offers advanced dispersion control, Yet dynamic reconfigurability remains largely unexplored. This work develops a dispersion-engineered inverse design framework that enables 3D multi-plane frequency-reconfigurable holography through a twisted metasurface system. The physical implementation is based on a compact bilayer configuration that cascades the broadband radiation-type metasurface (RA-M) and phase-only metasurface (P-M). The RA-M provides a phase-adjustable input to excite P-M, while the rotation of P-M creates a reconfigurable response of holograms. By employing the proposed scheme, dynamic switching of space-frequency multiplexing and achromatic holograms is designed and experimentally demonstrated in the microwave region. This method advances flexible dispersion engineering for metasurface-based holography, and the compact system holds significant potential for applications in near-field computational imaging/detection, high-speed high-data-capacity near-field wireless communication, and switchable meta-devices.

High-efficiency photon-pair production is a long-sought-after goal for many optical quantum technologies, and coherent photon conversion (CPC) processes are promising candidates for achieving this. We show theoretically how to control coherent conversion between a narrow-band pump photon and broadband photon pairs in nonlinear optical waveguides by tailoring frequency dispersion for broadband quantum frequency mixing. We reveal that complete deterministic conversion as well as pump-photon revival can be achieved at a finite propagation distance. We also find that high conversion efficiencies can be realised robustly over long propagation distances. These results demonstrate that dispersion engineering is a promising way to tune and optimise the CPC process.

Broadband achromatic meta-devices have emerged as a transformative platform for dispersion-engineered wavefront manipulation, offering significant potential for full-color imaging, multi-band spectral sensing, and integrated photonic systems. However, realizing spin-unlocked achromatic functionality remains fundamentally challenging due to the intrinsic dispersion correlations between orthogonal spin channels in conventional metasurface architectures. Here, we propose a hybrid-phase strategy that synergistically combines the distinct dispersion characteristics of Aharonov-Anandan and Pancharatnam-Berry geometric phases. This mechanism is implemented through a single-layer double-arc meta-structure that enables broadband achromatic wavefront control with complete spin-channel independence. As experimental validation, we demonstrate spin-unlocked achromatic meta-devices including dual-functionality beam deflectors and high-efficiency meta-lenses, both exhibiting broadband chromatic-aberration-free performances. This approach establishes a new paradigm for spin-unlocked achromatic metasurfaces and paves the way for multi-channel optical imaging, on-chip spectral detection, and other emerging spin-photonic applications.

Optical systems with wide field-of-views (FOV) are crucial for many applications such as high performance imaging, optical projection, augmented/virtual reality, and miniaturized medical imaging tools. Typically, aberration-free imaging with a wide FOV is achieved by stacking multiple refractive lenses (as in a “fisheye” lens), adding to the size and weight of the optical system. Single metalenses designed to have a wide FOV have the potential to replace these bulky imaging systems and, moreover, they may be dispersion engineered for spectrally broadband operation. In this paper, we derive a fundamental bound on the spectral bandwidth of dispersion-engineered wide-FOV achromatic metalenses. We show that for metalenses with a relatively large numerical aperture (NA), there is a tradeoff between the maximum achievable bandwidth and the FOV; interestingly, however, the bandwidth reduction saturates beyond a certain FOV that depends on the NA of the metalens. These findings may provide important information and insights for the design of future wide-FOV achromatic flat lenses.

Topological photonics offers a robust platform for controlling light, with applications such as backscattering‐immune edge‐transport and slow‐light propagation. A comprehensive and automated framework is presented for the design and characterization of symmetry‐protected interface modes in 2D photonic crystals. The main tool in this approach is an iterative band‐connection algorithm that ensures symmetry consistency across the Brillouin zone, enabling reliable reconstruction of bands even near degeneracies. Complementing this, a data‐driven symmetry classification method is introduced that constructs comparator functions directly from eigenmode data, removing the need for predefined symmetry operations or irreducible representations. These tools are particularly suited for generative or parametrized geometries where symmetries may vary. Using this framework, example structures exhibiting obstructed atomic limits, characterized by Wannier center displacements and mode inversions, are identified. The tradeoffs between interface mode dispersion and bulk bandgap size are analyzed, and how the number of photonic crystal periods at the interface governs the emergence and robustness of topological modes is shown. Finally, the scalability of this approach across material platforms and operating wavelengths, including the telecommunication range, is demonstrated. These contributions enable physically grounded and fully automated design of topological photonic interfaces, paving the way for large‐scale exploration and optimization of complex photonic structures. This article introduces an automated framework for topological photonic crystal design. It features an iterative band connection method for identifying band crossings, a data‐driven approach for band symmetry recognition, and analysis of how topological mode dispersion trades off with photonic band‐gap size. The role of unit cell count in determining mode localization, stability, and unidirectionality is also examined.