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Vol. 1 ， Issue 1 ， 2012
- Abstract：We present epi-diffraction phase microscopy (epi-DPM) as a non-destructive optical method for monitoring semiconductor fabrication processes in real time and with nanometer level sensitivity. The method uses a compact Mach–Zehnder interferometer to recover quantitative amplitude and phase maps of the field reflected by the sample. The low temporal noise of 0.6 nm per pixel at 8.93 frames per second enabled us to collect a three-dimensional movie showing the dynamics of wet etching and thereby accurately quantify non-uniformities in the etch rate both across the sample and over time. By displaying a gray-scale digital image on the sample with a computer projector, we performed photochemical etching to define arrays of microlenses while simultaneously monitoring their etch profiles with epi-DPM.Keywords：microscopy;nanoscale metrology;photochemical etching;quantitative phase imaging;semiconductor process monitoring
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Published：2024-09-30 - Abstract：Optical filters are essential in a wide range of applications, including optical communications, electronics, lighting, optical sensors and photography. This article presents recent work which indicates that optical filters can be created from specialized nanoparticle suspensions. Specifically, this article describes a theoretical optimization process for designing nanofluid-based filters for hybrid solar photovoltaic/thermal (PV/T) applications. This particular application is suitable because nanofluids can be utilized as both volumetric solar absorbers and flowing heat transfer mediums. The nanofluid filters described in this work compare favorably with conventional optical filters for five photovoltaic (PV) cell alternatives: InGaP, CdTe, InGaAs, Si, and Ge. This study demonstrates that nanofluids make efficient, compact and potentially low-cost, spectrally selective optical filters.Keywords：hybrid;nanofluid;optical filter;photovoltaic;solar energy;solar thermal
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Published：2024-09-30 - Abstract：Silicon photonic devices consisting of nanowire waveguides are a promising technology for on-chip integration in future optical telecommunication and interconnection systems based on silicon-large scale integration fabrication. However, the accommodation of variable optical components on a chip remains challenging due to the small size of microchips. In this study, we investigated the characteristics of a microelectromechanical silicon nanowire waveguide switch with a gap-variable coupler. Due to its capacitive operation, the proposed waveguide switch consumed negligible power relative to switches that use a thermo-optical effect and carrier injection. The proposed switch was characterized using analyses based on coupled-mode theory for rectangular waveguides, as well as a simulation using the finite difference time domain method. A 2×2 single switch with an improved configuration and a 2×6 multiple switch composed of the 2×2 switches was designed and fabricated by a combination of electron beam lithography, fast-atom beam etching and hydrofluoric acid vapor sacrificial etching. The properties of the switches were measured and evaluated at a wavelength of 1.55 µm.Keywords：microelectromechanical systems;optical switch;silicon photonics
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Published：2024-09-30 - Abstract：Layer-by-layer gold nanoparticles are used to generate photocurrent in an environmentally-friendly plasmon-sensitized solar cell towing to surface plasmon resonance. The efficiency of the photoelectric conversion of gold nanoparticle layers is increased as the intensity of surface plasmon resonance increases. We also explain the experimental results by modeling the phenomenon of charge separation and photocurrent formation, and the relationship between surface plasmon resonance and photocurrent formation, which has potential application in plasmon-sensitized solar cells and plasmonic solar cells in the future.Keywords：charge separation;layer-by-layer gold nanoparticles;plasmon-sensitized solar cells;plasmonic solar cells;surface plasmon resonance
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Published：2024-09-30 - Abstract：Scatterometry is a well-established, fast and precise optical metrology method used for the characterization of sub-lambda periodic features. The Fourier scatterometry method, by analyzing the Fourier plane, makes it possible to collect the angle-resolved diffraction spectrum without any mechanical scanning. To improve the depth sensitivity of this method, we combine it with white light interferometry. We show the exemplary application of the method on a silicon line grating. To characterize the sub-lambda features of the grating structures, we apply a model-based reconstruction approach by comparing simulated and measured spectra. All simulations are based on the rigorous coupled-wave analysis method.Keywords：Fourier scatterometry;inverse problem;optical sub-lambda metrology;RCWA;white light interference
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Published：2024-09-30 - Abstract：Integrated photonics is expected to play an increasingly important role in optical communications, imaging, computing and sensing with the promise for significant reduction in the cost and weight of these systems. Future advancement of this technology is critically dependent on an ability to develop compact and reliable optical components and facilitate their integration on a common substrate. Here we reveal, with the utility of the emerging transformation optics technique, that functional components composed of planar gradient index materials can be designed and readily integrated into photonic circuits. The unprecedented design flexibility of transformation optics allows for the creation of a number of novel devices, such as a light source collimator, waveguide adapters and a waveguide crossing, which have broad applications in integrated photonic chips and are compatible with current fabrication technology. Using the finite-difference time-domain method, we perform full-wave numerical simulations to demonstrate their superior optical performance and efficient integration with other components in an on-chip photonic system. These components only require spatially-varying dielectric materials with no magnetic properties, facilitating low-loss, broadband operation in an integrated photonic environment.Keywords：gradient index material;integrated photonic system;quasi-conformal mapping;transformation optics
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Published：2024-09-30 - Abstract：Large nonlinearity at the single-photon level can pave the way for the implementation of universal quantum gates. However, realizing large and noiseless nonlinearity at such low light levels has been a great challenge for scientists in the past decade. Here, we propose a scheme that enables substantial nonlinear interaction between two light fields that are both stored in an atomic memory. Semiclassical and quantum simulations demonstrate the feasibility of achieving large cross-phase modulation (XPM) down to the single-photon level. The proposed scheme can be used to implement parity gates from which CNOT gates can be constructed. Furthermore, we present a proof of principle experimental demonstration of XPM between two optical pulses: one stored and one freely propagating through the memory medium.Keywords：CNOT gate;cross-phase modulation;electromagnetically induced transparency;parity gate;quantum memory
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Published：2024-09-30 - Abstract：In this work, we present the first experimental evidence of negative dielectric susceptibility in a two-dimensional silicon photonic crystal (PhC) with negative refractive index behavior. In the frequency range in which the effective refractive index neff is equal to −1, the incident light couples efficiently to the guided modes in the top surface layer of the PhC metamaterial. These modes resemble surface plasmon polariton resonances. This finding was confirmed by ellipsometric measurements, demonstrating the isotropy of the PhC resonances. Such negative index PhC materials may be of use in biosensing applications.Keywords：diffraction gratings;metamaterials;photonic crystals
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Published：2024-09-30 - Abstract：According to the fundamental Huygens superposition principle, light beams traveling in a linear medium will pass though one another without mutual disturbance. Indeed, the field of photonics is based on the premise that controlling light signals with light requires intense laser fields to facilitate beam interactions in nonlinear media, where the superposition principle can be broken. Here we challenge this wisdom and demonstrate that two coherent beams of light of arbitrarily low intensity can interact on a metamaterial layer of nanoscale thickness in such a way that one beam modulates the intensity of the other. We show that the interference of beams can eliminate the plasmonic Joule losses of light energy in the metamaterial or, in contrast, can lead to almost total absorption of light. Applications of this phenomenon may lie in ultrafast all-optical pulse-recovery devices, coherence filters and terahertz-bandwidth light-by-light modulators.Keywords：all-optical;metamaterial;plasmonic
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Published：2024-09-30 - Abstract：Light absorption and energy transfer were studied in a bionic system with donors and an acceptor. In the optimal case of uniform couplings, this seemingly complicated system was reduced to a three-level Λ-type system. With this observation, we showed that the efficiency of energy transfer through a dark-state channel, which is free of the spontaneous decay of the donors, was dramatically improved. After the overall average transfer time was evaluated, it was revealed that the time required for transfer through this channel was not optimal. To find the optimal parameters for the present system, we defined a new quantity, output power, which characterizes the average mean output of the whole transfer process. We estimated the optimal parameters of the system to achieve the maximum output power. The splitting behaviour of the maximum power may be used to explain the phenomenon of photosynthetic systems primarily absorbing two colours of light.Keywords：dark state;excitation transfer;light harvesting;quantum coherence
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Published：2024-09-30 - Abstract：Modern three-dimensional nanofabrication requires both additive and subtractive processes. However, both processes are largely isolated and generally regarded as incompatible with each other. In this study, we developed simultaneous additive and subtractive fabrication processes using two-photon polymerization followed by femtosecond (fs) laser multiphoton ablation. To demonstrate the new capability, submicrometer polymer fibers containing periodic holes of 500-nm diameter and microfluidic channels of 1-µm diameter were successfully fabricated. This method combining both two-photon polymerization and fs laser ablation improves the nanofabrication efficiency and enables the fabrication of complex three-dimensional micro-/nanostructures, promising for a wide range of applications in integrated optics, microfluidics and microelectromechanical systems.Keywords：femtosecond laser direct writing;femtosecond laser multiphoton ablation;micro-/nanofabrication;two-photon polymerization
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Published：2024-09-30 - Abstract：Rare earth-doped fibres are a diode-pumped, solid-state laser architecture that is highly scalable in average power. The performance of pulsed fibre laser systems is restricted due to nonlinear effects. Hence, fibre designs that allow for very large mode areas at high average powers with diffraction-limited beam quality are of enormous interest. Ytterbium-doped, rod-type, large-pitch fibres (LPF) enable extreme fibre dimensions, i.e., effective single-mode fibres with mode sizes exceeding 100 times the wavelength of the guided radiation, by exploiting the novel concept of delocalisation of higher-order transverse modes. The non-resonant nature of the operating principle makes LPF suitable for high power extraction. This design allows for an unparalleled level of performance in pulsed fibre lasers.Keywords：higher-order mode delocalisation;high-power fibre lasers and amplifiers;photonic-crystal fibre;very large mode area
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Published：2024-09-30 - Abstract：Light-emitting diodes are becoming the alternative for future general lighting applications, with huge energy savings compared to conventional light sources owing to their high efficiency and reliability. Polarized light sources would largely enhance the efficiency in a number of applications, such as in liquid-crystal displays, and also greatly improve contrast in general illumination due to the reduction in indirect glare. Here, we demonstrate light-emitting diodes presenting high-brightness polarized light emission by combining the polarization-preserving and directional extraction properties of embedded photonic-crystals applied to non-polar gallium nitride. A directional enhancement of up to 1.8-fold was observed in the total polarized light emission together with a high polarization degree of 88.7% at 465 nm. We discuss the mechanisms of polarized light emission in non-polar gallium nitride and the photonic-crystal design rules to further increase the light-emitting diode brightness. This work could open the way to polarized white-light emitters through their association with polarization-preserving down-converting phosphors.Keywords：GaN;LEDs;m-plane;polarized light
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Published：2024-09-30 - Abstract：Light passing through a subwavelength hole in an opaque plate is a fundamental concern in both optical science and applications. Using both simulations and experiments, we show that, when a subwavelength hole in a silver thin film is surrounded by well-designed patterns of grooves, the wavefront of the infrared light through it can be shaped into a preset complicated pattern such as a Latin letter 'L' or 'O' at a given position instead of being diffracted in all directions. The design is created via the surface-wave-holography method, which allows direct determination of the surface plasmonic structure for a given wavefront-engineering functionality without the need to solve complex inverse problems. The results will deepen current understanding of this enduring issue and will find applications in many fields such as wave manipulation and sensing.Keywords：plasmonics;surface wave holography;subwavelength hole;wavefront shaping
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Published：2024-09-30 - Abstract：The surface plasmon resonance tracking over metal surfaces is a well-established, commercially available, biochemical quantification tool primarily applied in research. The utilization of such a tool is, however, constrained to highly specialized industries, capable of justifying the human and instrumental resource investments required by the characterization method. We have proposed to expand the field of application of this biosensing approach by redesigning this method through the integration and miniaturization within a semiconductor platform. Uncollimated and broadband emission from a light-emitting semiconductor is employed to couple a continuum of surface plasmon modes over a metal–dielectric architecture interfaced with a GaAs–AlGaAs substrate. A tensor version of rigorous coupled wave theory is employed to optimize the various fabrication specifications and to predict the light scatterings over a wide range of variables. We then present a hyperspectral characterization microscope capable of directly mapping the dispersion relation of scattered light, including diffracted surface plasmons, as an intensity distribution versus photon energy and surface wavevectors. Measurements carried out in a buffered solution demonstrate the accurate description of the uncollimated and broadband surface plasmon states. Finally, we introduce a simplified method of dispersion mapping, in which quasi-conic cross-sections of the light's scattering can be acquired directly, thus monitoring surficial responses in as fast as 1.2 s. This is over 300 times faster than required by implementing full dispersion mapping. While compromising on the volume of collected information, this method, combined with the solid-state integration of the platform, shows great promise for the fast detection of biochemical agents.Keywords：biosensors;light scattering;optical devices;semiconductors;surface plasmon resonance
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Published：2024-09-30
Original Article
- Abstract：The existing knowledge on the electrodynamics of invisibility cloaking based on transformation optics is reviewed from an integrated science and engineering perspective. Several significant electromagnetic problems that have resulted in intense discussions in the past few years are summarized in terms of propagation, scattering, radiation and fabrication. Finally, the road ahead toward invisibility cloaking and transformation optics is discussed from the viewpoint of the author.Keywords：invisibility cloaking;metamaterials;transformation optics
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Published：2024-09-30 - Abstract：It has recently been demonstrated that Bi-doped glass optical fibers are a promising active laser medium. Various types of Bi-doped optical fibers have been developed and used to construct Bi-doped fiber lasers and optical amplifiers. This paper reviews the recent results regarding the luminescence properties of various Bi-doped optical fibers and the development of Bi-doped fiber lasers and optical amplifiers for the 1150 to 1550 nm spectral region.Keywords：amplifier;bismuth;fiber;laser;luminescence
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Published：2024-09-30 - Abstract：Silicon-based large-scale photonic integrated circuits are becoming important, due to the need for higher complexity and lower cost for optical transmitters, receivers and optical buffers. In this paper, passive technologies for large-scale photonic integrated circuits are described, including polarization handling, light non-reciprocity and loss reduction. The design rule for polarization beam splitters based on asymmetrical directional couplers is summarized and several novel designs for ultra-short polarization beam splitters are reviewed. A novel concept for realizing a polarization splitter–rotator is presented with a very simple fabrication process. Realization of silicon-based light non-reciprocity devices (e.g., optical isolator), which is very important for transmitters to avoid sensitivity to reflections, is also demonstrated with the help of magneto-optical material by the bonding technology. Low-loss waveguides are another important technology for large-scale photonic integrated circuits. Ultra-low loss optical waveguides are achieved by designing a Si3N4 core with a very high aspect ratio. The loss is reduced further to < 0.1 dB m−1 with an improved fabrication process incorporating a high-quality thermal oxide upper cladding by means of wafer bonding. With the developed ultra-low loss Si3N4 optical waveguides, some devices are also demonstrated, including ultra-high-Q ring resonators, low-loss arrayed-waveguide grating (de)multiplexers, and high-extinction-ratio polarizers.Keywords：integration;low loss;non-reciprocal;polarization;silicon
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Published：2024-09-30 - Abstract：The ability to manufacture coatings is critical to engineering design. Many components require the application of additional layers to enhance mechanical properties and protect against hostile environments. Supersonic laser deposition (SLD) is a novel coating method based on cold spray (CS) principles. In this technique, the deposition velocities can be significantly lower than those required for effective bonding in CS applications. The addition of laser heat energy permits a change in the thermodynamic experience of impacting particles, thereby offering a greater opportunity for efficient bonding at lower velocities as compared with the CS process. The work reported in this paper demonstrates the ability of the SLD process to deliver hardfacing materials to engineering surfaces. Stellite-6 has been deposited on low-carbon steel tubes over a range of process parameters to establish the appropriate target power and traverse speeds for the coating formation. The coating properties and parameters were examined to determine the primary characteristics and grain structure size. Their morphology and performance were studied through optical microscopy, scanning electron microscope (SEM), X-ray diffraction, hardness measurements and wear testing. The results have shown that SLD is capable of depositing layers of Stellite-6, with properties that are superior to those of their conventionally manufactured counterparts.Keywords：cold spray;laser;supersonic laser deposition (SLD);Stellite;wear
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Published：2024-09-30 - Abstract：Miniaturization has been an everlasting theme in the development of semiconductor lasers. One important breakthrough in this process in recent years is the use of metal-dielectric composite structures that made truly subwavelength lasers possible. Many different designs of metallic cavity semiconductor nanolasers have been proposed and demonstrated. In this article, we will review some of the most exciting progresses in this newly emerging field. In particular, we will focus on metallic-cavity nanolasers with volume smaller than wavelength cubed under electrical injection with emphasis on high-temperature operation. Such devices will serve as an important component in the future integrated nanophotonic systems due to its ultra-small size.Keywords：semiconductor lasers;nanolasers;Plasmons;Plasmon Polaritons;Metal Cavity
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Published：2024-09-30 - Abstract：A review is made of the physics and technology of spectrally selective thermal detectors, especially those operating at non-cryogenic temperatures. The background radiation noise fluctuations are rederived for arbitrary spectral characteristics. Infrared absorption due to phonons and free carriers is discussed followed by a review of published works on artificial infrared absorption materials such as patterned grids, nanoparticles, plasmonic structures, metamaterials and others. Subsequently, the literature of the spectral characteristics of broadband thermal detectors and spectrally selective thermal detectors is reviewed. Finally, the authors speculate on the directions that future research and development in the area will take regarding architectures, sensitivity and spectral characteristics.Keywords：infrared detectors;infrared materials;radiation noise;thermal detectors
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Published：2024-09-30
Review
Editorial
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