Perovskite-enabled optical devices have drawn intensive interest and have been considered promising candidates for integrated optoelectronic systems. As one of the important photonic functions, optical phase modulation previously was demonstrated with perovskite substrate and complex refractive index engineering with laser scribing. Here we report on the new scheme of achieving efficient phase modulation by combining detour phase design with 40 nm ultrathin perovskite films composed of nanosized crystalline particles. Phase modulation was realized by binary amplitude patterning, which significantly simplifies the fabrication process. Perovskite nanocrystal films exhibit significantly weak ion migration effects under femtosecond laser writing, resulting in smooth edges along the laser ablated area and high diffractive optical quality. Fabrication of a detour-phased perovskite ultrathin planar lens with a diameter of 150 μm using femtosecond laser scribing was experimentally demonstrated. A high-performance 3D focus was observed, and the fabrication showed a high tolerance with different laser writing powers. Furthermore, the high-quality imaging capability of perovskite ultrathin planar lenses with a suppressed background was also demonstrated.

Light beams carrying orbital angular momentum (OAM) have inspired various advanced applications, and such abundant practical applications in turn demand complex generation and manipulation of optical vortices. Here, we propose a multifocal graphene vortex generator, which can produce broadband angular momentum cascade containing continuous integer non-diffracting vortex modes. Our device naturally embodies a continuous spiral slit vortex generator and a zone plate, which enables the generation of high-quality continuous vortex modes with deep depths of foci. Meanwhile, the generated vortex modes can be simultaneously tuned through incident wavelength and position of the focal plane. The elegant structure of the device largely improves the design efficiency and can be fabricated by laser nanofabrication in a single step. Moreover, the outstanding property of graphene may enable new possibilities in enormous practical applications, even in some harsh environments, such as aerospace.

Flat lenses thinner than a wavelength promise to replace conventional refractive lenses in miniaturized optical systems. However, Fresnel zone plate flat lens designs require dense annuli, which significantly challenges nanofabrication resolution. Herein, we propose a new implementation of detour phase graphene flat lens with flexible annular number and width. Several graphene metalenses demonstrated that with a flexible selection of the line density and width, the metalenses can achieve the same focal length without significant distortions. This will significantly weaken the requirement of the nanofabrication system which is important for the development of large-scale flat lenses in industry applications.

Ultrathin flat metalenses have emerged as promising alternatives to conventional diffractive lenses, offering new possibilities for myriads of miniaturization and interfacial applications. Graphene-based materials can achieve both phase and amplitude modulations simultaneously at a single position due to the modification of the complex refractive index and thickness by laser conversion from graphene oxide into graphene like materials. In this work, we develop graphene oxide metalenses to precisely control phase and amplitude modulations and to achieve a holistic and systematic lens design based on a graphene-based material system. We experimentally validate our strategies via demonstrations of two graphene oxide metalenses: one with an ultra-long (~16λ) optical needle, and the other with axial multifocal spots, at the wavelength of 632.8 nm with a 200 nm thin film. Our proposed graphene oxide metalenses unfold unprecedented opportunities for accurately designing graphene-based ultrathin integratable devices for broad applications.

Microbubbles acting as lenses are interesting for optical and photonic applications such as volumetric displays, optical resonators, integration of photonic components onto chips, high-resolution spectroscopy, lithography, and imaging. However, stable, rationally designed, and uniform microbubbles on substrates such as silicon chips are challenging because of the random nature of microbubble formation. We describe the fabrication of elastic microbubbles with a precise control of volume and curvature based on femtosecond laser irradiated graphene oxide. We demonstrate that the graphene microbubbles possess a near-perfect curvature that allows them to function as reflective microlenses for focusing broadband white light into an ultrahigh aspect ratio diffraction-limited photonic jet without chromatic aberration. Our results provide a pathway for integration of graphene microbubbles as lenses for nanophotonic components for miniaturized lab-on-a-chip devices along with applications in high-resolution spectroscopy and imaging.

Particle nanotracking (PNT) is highly desirable in lab-on-a-chip systems for flexible and convenient multiparameter measurement. An ultrathin flat lens is the preferred imaging device in such a system, with the advantage of high focusing performance and compactness. However, PNT using ultrathin flat lenses has not been demonstrated so far because PNT requires the clear knowledge of the relationship between the object and image in the imaging system. Such a relationship still remains elusive in ultrathin flat lens-based imaging systems because they operate based on diffraction rather than refraction. In this paper, we experimentally reveal the imaging relationship of a graphene metalens using nanohole arrays with micrometer spacing. The distance relationship between the object and image as well as the magnification ratio is acquired with nanometer accuracy. The measured imaging relationship agrees well with the theoretical prediction and is expected to be applicable to other ultrathin flat lenses based on the diffraction principle. By analyzing the high-resolution images from the graphene metalens using the imaging relationship, 3D trajectories of particles with high position accuracy in PNT have been achieved. The revealed imaging relationship for metalenses is essential in designing different types of integrated optical systems, including digital cameras, microfluidic devices, virtual reality devices, telescopes, and eyeglasses, and thus will find broad applications.

Recently, fundamental properties and practical applications of two-dimensional (2D) materials have attracted tremendous interest. Micro/nanostructures and functional devices in 2D materials have been fabricated by various methods. Ultrafast direct laser writing (DLW) with the advantages of rich light-matter interactions; unique three-dimensional processing capability; arbitrary-shape design flexibility; and minimized thermal effect, which enables high fabrication accuracy resolution, has been widely applied in the fabrication of 2D materials for multifunctional devices. This timely review summarizes the laser interactions with 2D materials and the advances in diverse functional photonics devices by DLW. The perspectives and challenges in designing and improving laser-fabricated 2D material photonic devices are also discussed.