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The rapid development of additive manufacturing has fueled a revolution in various research fields and industrial applications. Among the myriad of advanced 3D printing techniques, two‐photon polymerization lithography (TPL) uniquely offers a significant advantage in nanoscale print resolution, and has been widely employed in diverse fields, for example, life sciences, materials sciences, mechanics, and microfluidics. More recently, by virtue of the optical transparency of most of the resins used, TPL is finding new applications in optics and photonics, with nanometer to millimeter feature dimensions. It enables the minimization of optical elements and systems, and exploration of light‐matter interactions with new degrees of freedom, never possible before. To review the recent progress in the TPL related optical research, it starts with the fundamentals of TPL and material formulation, then discusses novel fabrication methods, and a wide range of optical applications. These applications notably include diffractive, topological, quantum, and color optics. With a panoramic view of the development, it is concluded with insights and perspectives of the future development of TPL and related potential optical applications. [ABSTRACT FROM AUTHOR]

The article titled "Light Engineering and Silicon Diffractive Optics Assisted Nonparaxial Terahertz Imaging" explores the use of structured terahertz light in nonparaxial lensless imaging systems. The study focuses on the application of silicon diffractive optics to create Airy beams, which resemble a "THz sun," and illuminate Fresnel, Fibonacci, and Bessel shaped THz beams. The article, authored by Sergej Orlov, Rusnė Ivaškevičiūtė‐Povilauskienė, and their colleagues, provides a comprehensive analysis of the modulation transfer map dependencies on the distance between the imaged object and the optical element. [Extracted from the article]

Geometric phase is a unifying and central concept in physics, including optics. As a matter of fact, optics played a pivotal role from the inception of this new paradigm, as some of the first experimental demonstrations have been carried out in optics. A specific type of geometric phase was first introduced by Pancharatnam while investigating interference effects between different polarizations. This specific type of geometric phase, nowadays called the Pancharatnam–Berry phase, is related to the variation of light polarization, encompassing exotic properties when compared with the dynamic phase associated with the optical path. The most widespread manifestation of the Pancharatnam–Berry phase occurs in the presence of a twisted anisotropic material, yielding a point‐wise phase modulation proportional to the local rotation angle of the material. Here the basic mechanism behind the Pancharatnam–Berry phase is discussed. The various applications of this relatively original concept in photonics are then reviewed, presenting both the most important results and manufactured devices reported in literature. The interplay between geometric phase and diffraction occurring in bulk structures is discussed in detail. In the latter case it is shown how geometric phase can be harnessed to generate a new kind of optical waveguide without the necessity of any index gradient. [ABSTRACT FROM AUTHOR]

Organic photonic materials have high refractive index, fast transfer speed, low heat generation, and so on; and therefore, have great potential in optoelectronics and optical micro/nanocircuits. Herein, a new strategy using fluorescence–phosphorescence dual emission and disparity of optical loss in a smooth needle‐like organic crystal is reported to realize color tuning of the optical waveguide (OWG). Especially, a warm white‐light OWG emission is achieved by appropriately adjusting the excitation position, presenting the first report of single‐component organic waveguide with white light emission. Based on this, the as‐prepared 1D organic crystal has been demonstrated as a microscale optical correspondence device with multiple input and output responses, which offers potential applications in modern optics and photonics fields. [ABSTRACT FROM AUTHOR]

Optics, playing an ever‐important role in life, is developing toward miniaturization and integration. Particularly, the field programming of integrated optics will benefit its functionality and durability, thus is highly pursued. Here, through precisely controlling the space‐variant orientations of anisotropic liquid crystals (LCs), various graded‐index waveguides are demonstrated in a homogeneous medium. Straight/bending waveguides and ring resonators are fabricated via LC photopatterning. They exhibit pronounced polychromatic light‐guiding performance. Thanks to their intrinsic external‐stimuli responsivity, the thermal switchability and polarization tunability are verified. By selectively polymerizing, robust functional components and active connecting waveguides can be realized on the same chip. It provides a practical and universal solution to programmable integrated optics, and extends the applications of microstructured soft matter even in wearable photonics. [ABSTRACT FROM AUTHOR]

In the recent past, 2D black phosphorus (BP) has been intensively studied and examined due to its unique electronic, photonic, and mechanical properties. The tunable and moderate direct bandgap and the high carrier mobility of BP provide enormous potential in electronic and optoelectronic applications. In addition, the unique intrinsic anisotropic characteristics resulting from the puckered structure yield remarkable optical, electronic, transport, mechanical, and thermal characteristics that can be utilized for designing new devices. Significant efforts have been directed toward the synthesis, basic understanding, and applications of BP in the fields of nanoelectronics, ultrafast optics, nanophotonics, and optoelectronics. Here, the current development of electronic, photonic, optoelectronic, and optical devices based on BP is summarized, along with the recent advances in investigating its electronic, optical, and mechanical properties, which form the foundation for next‐generation chip‐scale integrated devices. In addition, a comprehensive discussion on the requirements for forthcoming studies to upgrade well‐systemized fabrication techniques toward large‐area, high‐yield, and perfectly shielded BP‐film production for the development of reliable devices in optoelectronic applications and other areas is provided. Finally, some existing challenges in implementing BP‐based optoelectronic and photonic devices are addressed and the prospects for future BP‐related research are discussed. [ABSTRACT FROM AUTHOR]

Significant scientific and technological advances in photonics have facilitated the development of plasmonic and metallo-dielectric devices that rely on metal thin-films. Metal based devices, however, are limited by the inability to actively tune the optical properties of metals. Recent work has demonstrated the ability to highly strain metal thin-films on elastomeric substrates without losing electrical continuity in the film. Herein, we examine the optical properties of metal thin-films deposited on elastomeric substrates under strain. We demonstrate that reversible modulation of the mechanical structure of the pliable metallo-dielectric film results in a combination of scattering and surface plasmon excitations, that alter the film transmittance and reflectance. Further, it is shown that control over the wavelength of plasmonic resonances of the film can be achieved through variation in metal film thickness and modification of the local refractive index. The ability to actuate the plasmonic resonances of the metal thin-films using strain represent a novel method of actively tuning the properties of metal thin-films and will help facilitate the development of strain-tunable plasmonic and metallo-dielectric devices. [ABSTRACT FROM AUTHOR]

Guiding light in the low index region of a high refractive index contrast waveguide can be beneficial for many applications including sensing, nonlinear optics and electro-optics. Existing methods to achieve this goal suffer from fabrication complexity, large loss, or poor optical confinement. We propose a simple structure to achieve a significant enhancement of light confinement in the low index medium. We explain the guiding principle of this structure using geometrical optics, and suggest a number of applications where this guiding structure can provide significant performance benefits. The combination of simplicity, ease of fabrication, and good confinement makes this waveguide an attractive choice for a wide range of applications. To illustrate this, we consider the integration of a nonlinear polymer with a silicon photonic waveguide, and show that significantly better performance with an easier fabrication process can be achieved using this new scheme. [ABSTRACT FROM AUTHOR]

Photonic glass is a material class that can be used as photonic broadband reflectors, for example in the infrared regime as thermal barrier coating films. Photonic properties such as the reflectivity depend on the ordering and material packing fraction over the complete film thickness of up to 100 µm. Nanotomography allows acquiring these key parameters throughout the sample volume at the required resolution in a non-destructive way. By performing a nanotomography measurement at the PETRA III beamline P05 on a photonic glass film, the packing fraction throughout the complete sample thickness was analyzed. The results showed a packing fraction significantly smaller than the expected random close packing giving important information for improving the fabrication and processing methods of photonic glass material in the future. [ABSTRACT FROM AUTHOR]

Research on hybrid inorganic-organic materials has experienced an explosive growth since the 1980s, with the expansion of soft inorganic chemistry based processes. Indeed, mild synthetic conditions, low processing temperatures provided by 'chimie douce' and the versatility of the colloidal state allow for the mixing of the organic and inorganic components at the nanometer scale in virtually any ratio to produce the so called hybrid materials. Today a high degree of control over both composition and nanostructure of these hybrids can be achieved allowing tunable structure-property relationships. This, in turn, makes it possible to tailor and fine-tune many properties (mechanical, optical, electronic, thermal, chemical...) in very broad ranges, and to design specific multifunctional systems for applications. In particular, the field of 'Hybrid-Optics' has been very productive not only scientifically but also in terms of applications. Indeed, numerous optical devices based on hybrids are already in, or very close, to the market. This review describes most of the recent advances performed in this field. Emphasis will be given to luminescent, photochromic, NLO and plasmonic properties. As an outlook we show that the controlled coupling between plasmonics and luminescence is opening a land of opportunities in the field of 'Hybrid-Optics'. [ABSTRACT FROM AUTHOR]

A major aim of researchers working in the field of optics and photonics is to mold the flow of light in optical structures and devices. In the regime of ballistic light propagation, transformation optics has given a certain boost, for which optical invisibility cloaking devices are striking examples. Our capability to mold the flow of light in the regime of diffuse light propagation in light-scattering media has fallen behind-while diffuse light from clouds, white wallpaper, computer monitors, and light-emitting diodes is literally all around us every day. In this review, we summarize progress in steering the flow of diffuse light in turbid media which was triggered by the mathematical analogy between electrostatics, magnetostatics, stationary heat conduction, and stationary light diffusion. We give an extensive tutorial introduction to the mathematics of the diffusion equation for light and its solutions, present an overview on the current experimental state-of-the-art of simple core-shell invisibility cloaking, and compare these experiments with diffusion theory as well as with more advanced modelling based on Monte Carlo simulations. The latter approach enables spanning the bridge from diffusive to ballistic light propagation. [ABSTRACT FROM AUTHOR]

One of the challenges of the modern photonics is to develop all-optical devices enabling increased speed and energy efficiency for transmitting and processing information on an optical chip. It is believed that the recently suggested Parity-Time (PT) symmetric photonic systems with alternating regions of gain and loss can bring novel functionalities. In such systems, losses are as important as gain and, depending on the structural parameters, gain compensates losses. Generally, PT systems demonstrate nontrivial non-conservative wave interactions and phase transitions, which can be employed for signal filtering and switching, opening new prospects for active control of light. In this review, we discuss a broad range of problems involving nonlinear PT-symmetric photonic systems with an intensity-dependent refractive index. Nonlinearity in such PT symmetric systems provides a basis for many effects such as the formation of localized modes, nonlinearly-induced PT-symmetry breaking, and all-optical switching. Nonlinear PT-symmetric systems can serve as powerful building blocks for the development of novel photonic devices targeting an active light control. [ABSTRACT FROM AUTHOR]

A table of contents for the 2016 issue of the journal "Laser & Photonics Reviews," is presented.

The article presents news briefs related to the optics and photonics industry. The German micro- and nanotechnology industry has shown a significant improvement in the year 2013. The German machine vision industry is moving on a stable growth path. Toptica Photonics AG has developed a new generation of sodium guide star lasers for deployment at ESO's Very Large Telescope VLT in Paranal, Chile.

The table of contents for the January 2014 issue of "Laser & Photonics Reviews" is presented.

The stack-and-draw technique has been used to fabricate photonic crystal fibers (PCFs) from four different types of soft glass, namely, borosilicate, alkaline, lead, and tungsten–tellurite. The thermophysical properties of the components must be matched in order to produce PCFs from a combination of glass types. Lead/alkaline PCFs could be fabricated without crystallization or fragility problems. Using borosilicate glass alone, PCFs with up to five hollow periodic structures could be formed. With tungsten–tellurite glass, a PCF with one hollow periodic structure and a core doped with Er3+ ions have been produced. The properties of this fiber confirm its potential application in optical amplification or in other active devices. [ABSTRACT FROM AUTHOR]

We have developed an algorithm for evaluating the accuracy and reliability of photonic crystal (PhC) simulations, and used it to analyze the influence of excitation and detector placement in finite-difference time-domain algorithm (FDTD) simulations of two canonical PhC systems. In order to perform this computationally expensive analysis, we evaluated the use of filter diagonalization as an alternative to the Fourier Transform for mode detection, and developed a parallelization algorithm to take advantage of the inherent concurrency in simulating periodic systems. A map of locations where mode detection fails was generated, and we show that this is equivalent to a map of the node densities of the system. In addition to the expected high nodal densities at the symmetry areas of each system, we find more difficult to characterize patterns of high nodal density for the higher-order modes. Based on the observed behavior we are able to provide concrete rules to optimize the detection and excitation of modes in FDTD simulations of PhC systems. Although PhCs were studied, the presented strategies and results apply to the much broader class of all computational time-domain problems where Bloch–Floquet boundary conditions are used. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We describe an experimental method to recover a single, deterministically fabricated nanostructure in various experimental instruments without the use of artificially fabricated markers, with the aim to study photonic structures. Therefore, a detailed map of the spatial surroundings of the nanostructure is made during the fabrication of the structure. These maps are made using a series of micrographs with successively decreasing magnifications. The graphs reveal intrinsic and characteristic geometric features that can subsequently be used in different setups to act as markers. As an illustration, we probe surface cavities with radii of 65 nm on a silica opal photonic crystal with various setups: a focused ion beam workstation; a scanning electron microscope (SEM); a wide field optical microscope and a confocal microscope. We use cross-correlation techniques to recover a small area imaged with the SEM in a large area photographed with the optical microscope, which provides a possible avenue to automatic searching. We show how both structural and optical reflectivity data can be obtained from one and the same nanostructure. Since our approach does not use artificial grids or markers, it is of particular interest for samples whose structure is not known a priori, like samples created solely by self-assembly. In addition, our method is not restricted to conducting samples. [ABSTRACT FROM AUTHOR]

We have proposed a novel scheme to generate optical mm-wave DWDM signals with four time frequency of the local oscillator by using only one external modulator. By incorporating the proper direct current (DC) bias on the external modulator to suppress the first order sideband in central office (CO), and using optical filtering technique to separate the optical mm-wave and optical carrier in the base station, the dense wavelength division multiplexing (DWDM) optical millimeter-wave (mm-wave) signals are generated with four times frequency of the LO signal. We have experimentally demonstrated four-channel DWDM optical mm-wave signal generation with a repetitive frequency up to 40 GHz by 10 GHz LO, and down-stream signal delivery over 20-km fiber with 0.7-dB power penalty. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1152–1155, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23328 [ABSTRACT FROM AUTHOR]

This article presents a miniaturized patch antenna for wireless applications at 2.4 GHz. A conventional microstrip-fed patch antenna is firstly designed to operate close to 10 GHz. Then, the antenna is modified to operate at lower frequency without changing the antenna dimensions. First, the ground plane is replaced with a uniplanar-compact-photonic-band-gap (UC-PBG) structure. Then, a backed conductor is placed close to the UC-PBG and connected to it through four vias. These two modifications are utilized to decrease the lower operating frequency of the antenna from 9.7 to 2.42 GHz. Thus, a 75% size reduction factor is obtained. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1360–1363, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23381 [ABSTRACT FROM AUTHOR]

A continuously tunable incoherent microwave photonic filter employing a tunable Mach-Zehnder interferometer (MZI) as the slicing filter is studied. By incorporating the optical variable delay line (OVDL), the frequency spacing of the MZI can be tuned continuously, which in turn makes the whole microwave photonic filter continuously tunable in a wide frequency range. The frequency response characteristics are studied and some simulation results are also given to optimize the present microwave photonic filter. Experimental results show the present filter has good frequency response characteristics and tuning linearity. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2382–2386, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22732 [ABSTRACT FROM AUTHOR]

Optical filters with ultranarrow wavelength spacing of 0.068, 0.052, and 0.032 nm, are designed and fabricated on uniform fiber Bragg grating (FBG). Moreover, triple-, and quadruple-transmission bands with wavelength spacing of 0.050, 0.046 nm, respectively, are achieved through introducing three and four phase shifts along the fiber Bragg grating. These filters can be applied in the ultranarrow wavelength spacing filtering, photonic generation of microwave signal, multiwavelength distributed feedback Bragg lasing, etc. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1122–1125, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22392 [ABSTRACT FROM AUTHOR]

Development of fast, flexible, and accurate methods for the analysis (and design) of photonic crystals devices is a relevant topic in order to optimize existing devices and/or developing new design solutions. Within this framework, in this article, we present an improved version of the scattering matrix method [1] for the evaluation of the electromagnetic behavior of two-dimensional finite-extent photonic crystals made of a finite set of parallel dielectric rods. In particular, by relying on features of the fields to be computed within the device and a suitable aggregation into “macrocells”, a considerable reduction of the number of unknowns of the linear system to be solved is achieved. A numerical analysis confirms the accuracy of the proposed method and the remarkable computational benefit. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2564–2570, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21998 [ABSTRACT FROM AUTHOR]

An assessment of four linear-system iterative solvers is carried out through the simulation of a key 2D photonic crystal structure. Among these solvers, the biconjugate gradient stabilized (BCGS) in conjunction with the incomplete LU (ILU) decomposition, shows the best performance and can be regarded as a promising candidate for large-scale computation. In addition, the iterative solver with the best performance is applied to analysis of the directional optical coupler and transverse anisotropic waveguide. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1182–1186, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21571 [ABSTRACT FROM AUTHOR]

In this paper, two different uniform photonic band-gap (PBG) structures used as stopband filters for microstrip lines at 5.4 GHz are proposed and compared in terms of the pattern shapes' effect on the S-parameters. This suggests the use of a 1D pattern to reduce the transversal size of the filters. The devices consist of 50Ω microstrip transmission line and periodical patterns including circles and squares etched on the ground plane of microstrip line. No drilling through the substrate is needed. The filters exhibit well-defined stopband and are simulated by 3D full-wave electromagnetic analysis using HFSS™. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1007–1011, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21585 [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel tunable transversal photonic RF notch filter based on opto-VLSI technology. By using an array of fiber Bragg gratings (FBGs) in conjunction with an opto-VLSI processor, the broadband light source can be spectrally sliced and attenuated, hence realizing a two-tap RF notch filter with stepwise true-time delays and variable weights. In addition, the free spectral frequency and notch depth of the RF notch filter can be tuned by driving the opto-VLSI processor with optimized phase-only holograms. We experimentally demonstrate the proposed tunable RF notch filter structure and the results show that a notch depth greater than 40 dB can be attained. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1011–1015, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21586 [ABSTRACT FROM AUTHOR]

We propose an optimized structure of a tunable and reconfigurable microwave-photonics filter. The structure exploits the capability of a high-precision dynamic-gain equalizer (DGE) to modify the optical spectrum of the broadband light source of a slicing filter. Independent tunability and reconfigurability is obtained due to the optimization of the dispersion properties of the optical fiber line. An experimental demonstration is given that illustrates the versatility and efficiency of the setup. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 562–567 2006; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.21408 [ABSTRACT FROM AUTHOR]

In the future photonic network, network applications such as grid computing and wide-area distributed SANs (storage area networks) will be realized on a new network platform called the “optical grid.” In this paper, an optical grid is studied, which would provide a network platform to networked applications such as grid computings in the future photonic network. The optical code (OC) label, an identifier for data flow, is an enabler due to its ultrafast processing capability. First, the variable-capacity OC-labeled path and optical code division multiplexed (OCDM) path are studied, which allow one to simultaneously set up a number of connections on a single wavelength path. Next, optical path setup using OC-labeled control packet, which bears the signaling message, is presented and experimentally demonstrated. This enables one to ultimately reduce the overhead time of the optical path setup. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(12): 1–10, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20241 [ABSTRACT FROM AUTHOR]