Hasil untuk "Optics. Light"

J. Xiong, En‐Lin Hsiang, Ziqian He et al.

With rapid advances in high-speed communication and computation, augmented reality (AR) and virtual reality (VR) are emerging as next-generation display platforms for deeper human-digital interactions. Nonetheless, to simultaneously match the exceptional performance of human vision and keep the near-eye display module compact and lightweight imposes unprecedented challenges on optical engineering. Fortunately, recent progress in holographic optical elements (HOEs) and lithography-enabled devices provide innovative ways to tackle these obstacles in AR and VR that are otherwise difficult with traditional optics. In this review, we begin with introducing the basic structures of AR and VR headsets, and then describing the operation principles of various HOEs and lithography-enabled devices. Their properties are analyzed in detail, including strong selectivity on wavelength and incident angle, and multiplexing ability of volume HOEs, polarization dependency and active switching of liquid crystal HOEs, device fabrication, and properties of micro-LEDs (light-emitting diodes), and large design freedoms of metasurfaces. Afterwards, we discuss how these devices help enhance the AR and VR performance, with detailed description and analysis of some state-of-the-art architectures. Finally, we cast a perspective on potential developments and research directions of these photonic devices for future AR and VR displays. Emerging holographic optical elements and lithography-based devices are enhancing the performances of augmented reality and virtual reality displays with glasses-like form factor.

Yijie Shen, Xuejiao Wang, Zhenwei Xie et al.

Thirty years ago, Coullet et al. proposed that a special optical field exists in laser cavities bearing some analogy with the superfluid vortex. Since then, optical vortices have been widely studied, inspired by the hydrodynamics sharing similar mathematics. Akin to a fluid vortex with a central flow singularity, an optical vortex beam has a phase singularity with a certain topological charge, giving rise to a hollow intensity distribution. Such a beam with helical phase fronts and orbital angular momentum reveals a subtle connection between macroscopic physical optics and microscopic quantum optics. These amazing properties provide a new understanding of a wide range of optical and physical phenomena, including twisting photons, spin–orbital interactions, Bose–Einstein condensates, etc., while the associated technologies for manipulating optical vortices have become increasingly tunable and flexible. Hitherto, owing to these salient properties and optical manipulation technologies, tunable vortex beams have engendered tremendous advanced applications such as optical tweezers, high-order quantum entanglement, and nonlinear optics. This article reviews the recent progress in tunable vortex technologies along with their advanced applications. Commemorating the 30th anniversary of the prediction of optical vortices by theoretical physicist Pierre Coullet and colleagues, researchers in China review the development of understanding and applications of these intriguing phenomena. Xing Fu at Tsinghua University, Xiaocong Yuan at Shenzhen University and co-authors, explain how the concept of optical vortices emerged from observed similarities between the behaviour of fluid vortices and some forms of laser light. The light waves of optical vortices are twisted around their direction of travel, with a point of zero intensity at their centre. The authors survey the steady refinement of techniques used to create optical vortices, and explore their applications. Prominent applications include sophisticated optical computing processes, novel microscopy and imaging techniques, the creation of ‘optical tweezers’ to trap particles of matter, and optical machining using light to pattern structures on the nanoscale.

W. T. Chen, A. Zhu, V. Sanjeev et al.

A. Kuznetsov, A. Miroshnichenko, M. Brongersma et al.

A clear approach to nanophotonics The resonant modes of plasmonic nanoparticle structures made of gold or silver endow them with an ability to manipulate light at the nanoscale. However, owing to the high light losses caused by metals at optical wavelengths, only a small fraction of plasmonics applications have been realized. Kuznetsov et al. review how high-index dielectric nanoparticles can offer a substitute for these metals, providing a highly flexible and low-loss route to the manipulation of light at the nanoscale. Science, this issue p. 10.1126/science.aag2472 BACKGROUND Nanoscale optics is usually associated with plasmonic structures made of metals such as gold or silver. However, plasmonics suffers from high losses of metals, heating, and incompatibility with complementary metal oxide semiconductor fabrication processes. Recent developments in nanoscale optical physics have led to a new branch of nanophotonics aiming at the manipulation of optically induced Mie resonances in dielectric and semiconductor nanoparticles with high refractive indices. Such particles offer unique opportunities for reduced dissipative losses and large resonant enhancement of both electric and magnetic near-fields. Semiconductor nanostructures also offer longer excited-carrier lifetimes and can be electrically doped and gated to realize subwavelength active devices. These recent developments revolve closely around the nature of the optical resonances of the structures and how they can be manipulated in individual entities and in complex particle arrangements such as metasurfaces. Resonant high-index dielectric nanostructures form new building blocks to realize unique functionalities and novel photonic devices. ADVANCES We discuss the key advantages of resonant high-index nanostructures, associated new physical effects, and applications for nanoantennas, optical sensors, nonlinear devices, and flat optics. For a subwavelength high-index dielectric particle illuminated by a plane wave, electric and magnetic dipole resonances have comparable strengths. The resonant magnetic response results from a coupling of incoming light to the circular displacement currents of the electric field, when the wavelength inside the particle becomes comparable to its diameter d = 2R ≈ λ/n, where R is the nanoparticle radius, n is its refractive index, and λ is the wavelength of light. At the wavelength of a magnetic resonance, the excited magnetic dipole mode of a high-index dielectric sphere may provide a dominant contribution to the scattering efficiency exceeding the contribution of other multipoles by orders of magnitude. Nanophotonic structures composed of dielectric resonators can exhibit many of the same features as plasmonic nanostructures, including enhanced scattering, high-frequency magnetism, and negative refractive index. The specific design and parameter engineering of all-dielectric nanoantennas and metasurfaces give rise to superior performance in comparison to their lossy plasmonic counterparts. Spectral signatures of the Mie-type resonances of these structures are revealed by using far-field spectroscopy while tuning geometrically their resonance properties. A special case is realized when the electric and magnetic resonances spectrally overlap; the impedance matching eliminates the backward scattering, leading to unidirectional scattering and Huygens metasurfaces. A variety of nanoparticle structures have been studied, including dielectric oligomers as well as metasurfaces and metadevices. The magnetic resonances lead to enhanced nonlinear response, Raman scattering, a novel Brewster effect, sharp Fano resonances, and highly efficient sensing and photodetection. OUTLOOK The study of resonant dielectric nanostructures has been established as a new research direction in modern nanophotonics. Because of their unique optically induced electric and magnetic resonances, high-index nanophotonic structures are expected to complement or even replace different plasmonic components in a range of potential applications. The unique low-loss resonant behavior allows reproduction of many subwavelength resonant effects demonstrated in nanophotonics without much energy dissipation into heat. In addition, the coexistence of strong electric and magnetic resonances, their interference, and resonant enhancement of the magnetic field in dielectric nanoparticles bring entirely novel functionalities to simple geometries largely unexplored in plasmonic structures, especially in the nonlinear regime or in optoelectronic device applications. Manifestations of all-dielectric resonant nanophotonics. (A) Structure of the fields near the magnetic dipole resonance. (B) Experimental demonstration of optical magnetic response shown through optical dark-field and scanning electron microscope images (top and bottom, respectively). (C) Unidirectional light scattering by a single dielectric nanoparticle for overlapping electric and magnetic dipole resonances, where k is the wave vector of the incident white light. (D) Light manipulation with highly transparent Huygens metasurfaces. Rapid progress in nanophotonics is driven by the ability of optically resonant nanostructures to enhance near-field effects controlling far-field scattering through intermodal interference. A majority of such effects are usually associated with plasmonic nanostructures. Recently, a new branch of nanophotonics has emerged that seeks to manipulate the strong, optically induced electric and magnetic Mie resonances in dielectric nanoparticles with high refractive index. In the design of optical nanoantennas and metasurfaces, dielectric nanoparticles offer the opportunity for reducing dissipative losses and achieving large resonant enhancement of both electric and magnetic fields. We review this rapidly developing field and demonstrate that the magnetic response of dielectric nanostructures can lead to novel physical effects and applications.

J. Fitzgerald, P. Narang, R. Craster et al.

Dianmin Lin, Pengyu Fan, E. Hasman et al.

A. Piazza, C. Müller, K. Hatsagortsyan et al.

The field of laser-matter interaction traditionally deals with the response of atoms, molecules, and plasmas to an external light wave. However, the recent sustained technological progress is opening up the possibility of employing intense laser radiation to trigger or substantially influence physical processes beyond atomic-physics energy scales. Available optical laser intensities exceeding ${10}^{22}\text{ }\text{ }\mathrm{W}/{\mathrm{cm}}^{2}$ can push the fundamental light-electron interaction to the extreme limit where radiation-reaction effects dominate the electron dynamics, can shed light on the structure of the quantum vacuum, and can trigger the creation of particles such as electrons, muons, and pions and their corresponding antiparticles. Also, novel sources of intense coherent high-energy photons and laser-based particle colliders can pave the way to nuclear quantum optics and may even allow for the potential discovery of new particles beyond the standard model. These are the main topics of this article, which is devoted to a review of recent investigations on high-energy processes within the realm of relativistic quantum dynamics, quantum electrodynamics, and nuclear and particle physics, occurring in extremely intense laser fields.

M. Kelzenberg, S. Boettcher, J. Petykiewicz et al.

P. West, S. Ishii, G. Naik et al.

Plasmonics is a research area merging the fields of optics and nanoelectronics by confining light with relatively large free‐space wavelength to the nanometer scale ‐ thereby enabling a family of novel devices. Current plasmonic devices at telecommunication and optical frequencies face significant challenges due to losses encountered in the constituent plasmonic materials. These large losses seriously limit the practicality of these metals for many novel applications. This paper provides an overview of alternative plasmonic materials along with motivation for each material choice and important aspects of fabrication. A comparative study of various materials including metals, metal alloys and heavily doped semiconductors is presented. The performance of each material is evaluated based on quality factors defined for each class of plasmonic devices. Most importantly, this paper outlines an approach for realizing optimal plasmonic material properties for specific frequencies and applications, thereby providing a reference for those searching for better plasmonic materials.

Raju Tomer, Li Ye, Brian Hsueh et al.

T. Kippenberg, D. Armani, S. Spillane et al.

E. Hutter, J. Fendler

T. Yoshie, A. Scherer, J. Hendrickson et al.

A. Otto

W. Gibbons, P. J. Shannon, Shao-Tang Sun et al.

Olaf Stenzel

M. Lipson

J Villatoro, M Alonso-Murias, D Maldonado-Hurtado et al.

Due to their multiple advantages, single-mode fiber Bragg gratings (FBGs) are widely used in a myriad of practical sensing applications. However, their concurrent sensitivity to strain and temperature makes a reference sensor necessary in several situations. Here, we demonstrate that a single supermode FBG can be used to measure bending and temperature. A specially designed two coupled-core optical fiber (TCCF) that supports two supermodes was fabricated in which gratings were inscribed with femtosecond or ultraviolet lasers. The interrogation of the gratings was carried out with a conventional FBG sensor interrogator. It was found that the reflection spectrum of the supermode grating depended on its inscription in the TCCF. So, it was possible to fabricate samples in which the reflection spectra exhibited two narrow peaks very close to each other with well-defined Bragg wavelengths and reflectivities. Cross sensitivities and polarization effects on the devices were studied. It was found that two Bragg wavelengths and two reflectivities provided abundant data to measure bending of the TCCF, temperature, and to discriminate in which direction the TCCF was bent. Thus, we believe that the results reported here can pave the way for next-generation grating-based specialty optical fiber devices that are capable of multi-parameter sensing. The results and approaches proposed here can also expand the use of Bragg grating technology.

Yangzhi Tan, Yitong Huang, Dan Wu et al.

Abstract Colloidal quantum dots (CQDs) are attractive gain media due to their wavelength-tunability and low optical gain threshold. Consequently, CQD lasers, especially the surface-emitting ones, are promising candidates for display, sensing and communication. However, it remains challenging to achieve a low-threshold surface-emitting CQD laser array with high stability and integration density. For this purpose, it is necessary to combine the improvement of CQD material and laser cavity. Here, we have developed high-quality CQD material with core/interlayer/graded shell structure to achieve a low gain threshold and high stability. Subsequently, surface-emitting lasers based on CQD-integrated circular Bragg resonator (CBR) have been achieved, wherein the near-unity mode confinement factor (Γ of 89%) and high Purcell factor of 22.7 attributed to the strong field confinement of CBR enable a low lasing threshold of 17 μJ cm− 2, which is 70% lower than that (56 μJ cm− 2) of CQD vertical-cavity surface-emitting laser. Benefiting from the high quality of CQD material and laser cavity, the CQD CBR laser is capable of continuous stable operation for 1000 hours (corresponding to 3.63 × 108 pulses) at room temperature. This performance is the best among solution-processed lasers composed of nanocrystals. Moreover, the miniaturized mode volume in CBR allows the integration of CQD lasers with an unprecedentedly high density above 2100 pixels per inch. Overall, the proposed low-threshold, stable and compactly integrated CQD CBR laser array would advance the development of CQD laser for practical applications.

Momen Diab, Ross Cheriton, Jacob Taylor et al.

In ground-based astronomy, the ability to couple light into single-mode fibers (SMFs) is limited by atmospheric turbulence, which prohibits the use of many astrophotonic instruments. We propose a silicon-on-insulator photonic chip capable of coherently coupling the out-of-phase beamlets from the subapertures of a telescope pupil into an SMF. The photonic integrated circuit (PIC) consists of an array of grating couplers that are used to inject light from free space into single-mode waveguides on the chip. Metallic heaters modulate the refractive index of a coiled section of the waveguides, facilitating the co-phasing of the propagating modes. The phased beamlets can then be coherently combined to efficiently deliver the light to an output SMF. In an adaptive optics (AO) system, the phase corrector acts as a deformable mirror (DM) commanded by a controller that takes phase measurements from a wavefront sensor (WFS). We present experimental results for the PIC tested on an AO testbed and compare the performance to simulations.