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Vol. 3 ， Issue 1 ， 2014
- Abstract：In this work, we report a novel soft diffractive micro-optics, called 'microscale kinoform phase-type lens (micro-KPL)', which is fabricated by femtosecond laser direct writing (FsLDW) using bovine serum albumin (BSA) as building blocks and flexible polydimethylsiloxane (PDMS) slices as substrates. By carefully optimizing various process parameters of FsLDW (e.g., average laser power density, scanning step, exposure time on a single point and protein concentration), the as-formed protein micro-KPLs exhibit excellent surface quality, well-defined three-dimensional (3D) geometry and distinctive optical properties, even in relatively harsh operation environments (for instance, in strong acid or base). Laser shaping, imaging and other optical performances can be easily achieved. More importantly, micro-KPLs also have unique flexible and stretchable properties as well as good biocompatibility and biodegradability. Therefore, such protein hydrogel-based micro-optics may have great potential applications, such as in flexible and stretchable photonics and optics, soft integrated optical microsystems and bioimplantable devices.Keywords：femtosecond laser direct writing;micro-optics;protein;soft
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Published：2024-09-30 - Abstract：Mode-locked lasers emitting a train of femtosecond pulses called dissipative solitons are an enabling technology for metrology, high-resolution spectroscopy, fibre optic communications, nano-optics and many other fields of science and applications. Recently, the vector nature of dissipative solitons has been exploited to demonstrate mode locked lasing with both locked and rapidly evolving states of polarisation. Here, for an erbium-doped fibre laser mode locked with carbon nanotubes, we demonstrate the first experimental and theoretical evidence of a new class of slowly evolving vector solitons characterized by a double-scroll chaotic polarisation attractor substantially different from Lorenz, Rössler and Ikeda strange attractors. The underlying physics comprises a long time scale coherent coupling of two polarisation modes. The observed phenomena, apart from the fundamental interest, provide a base for advances in secure communications, trapping and manipulation of atoms and nanoparticles, control of magnetisation in data storage devices and many other areas.Keywords：chaos;mode-locked laser;polarisation phenomena;vector soliton
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Published：2024-09-30 - Abstract：We demonstrate a bottom-up approach to fabricating a visible light-driven titania photocatalyst device bearing an embedded two-dimensional (2D) array of gold nanoparticles (AuNPs) as a near-field light-generating layer. The device is a layered structure prepared by depositing a 2D array of AuNPs on a transparent conductive substrate (10 nm indium tin oxide (ITO) layer on quartz), coating the 2D array of AuNPs with a monolayer of trimethoxyoctylsilane (TMOS), and depositing titania nanocrystals on the anchoring molecule (TMOS) layer. The visible light activity of the device was tested using photocatalytic degradation of methylene blue (MB) by illuminating the device with visible light (700 nm light) and ultraviolet (UV) light (250–380 nm). The localized surface plasmon resonance peak of the 36 nm AuNP 2D array is around 700 nm with a full-width at half-maximum of 350 nm. In comparison with other control samples, the device showed the highest photocatalytic activity with visible irradiation, which was 1.7 times higher than that of titania with UV irradiation. The origin of the visible light activity was confirmed by both quadratic incident light power dependency and action spectrum to be plasmon-induced (near-field enhancement by AuNPs) two-photon absorption.Keywords：gold nanoparticles;near-field light;plasmonics;two-photon absorption;visible photocatalysis
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Published：2024-09-30 - Abstract：Semiconductor exciton–polaritons in planar microcavities form coherent two-dimensional condensates in non-equilibrium. However, the coupling of multiple lower-dimensional polariton quantum systems, which are critical for polaritonic quantum device applications and novel cavity-lattice physics, has been limited in conventional cavity structures. Here, we demonstrate full non-destructive confinement of polaritons using a hybrid cavity composed of a single-layer subwavelength grating mirror and a distributed Bragg reflector. Single-mode polariton lasing was observed at a chosen polarization. The incorporation of a designable slab mirror in a conventional vertical cavity, when operating in the strong-coupling regime, enables the confinement, control and coupling of polariton gasses in a scalable fashion. This approach may open the door to experimental implementations of polariton-based quantum photonic devices and coupled cavity quantum electrodynamic systems.Keywords：Bose–Einstein condensation;microcavity;photonic crystal;polariton
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Published：2024-09-30 - Abstract：Optoacoustics provides a unique set of capabilities for bioimaging, associated with the intrinsic combination of ultrasound- and light-related advantages, such as high spatial and temporal resolution as well as powerful spectrally enriched imaging contrast in biological tissues. We demonstrate here, for the first time, the acquisition, processing and visualization of five-dimensional optoacoustic data, thus offering unparallel imaging capacities among the current bioimaging modalities. The newly discovered performance is enabled by simultaneous volumetric detection and processing of multispectral data and is further showcased here by attaining time-resolved volumetric blood oxygenation maps in deep human vessels and real-time tracking of contrast agent distribution in a murine model in vivo.Keywords：biophotonics;multispectral;optoacoustic imaging;photoacoustic tomography
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Published：2024-09-30 - Abstract：Semiconductor quantum dots (QDs) have been demonstrated viable for efficient light emission applications, in particular for the emission of single photons on demand. However, the preparation of QDs emitting photons with predefined and deterministic polarization vectors has proven arduous. Access to linearly polarized photons is essential for various applications. In this report, a novel concept to directly generate linearly-polarized photons is presented. This concept is based on InGaN QDs grown on top of elongated GaN hexagonal pyramids, by which the predefined elongation determines the polarization vectors of the emitted photons from the QDs. This growth scheme should allow fabrication of ultracompact arrays of photon emitters, with a controlled polarization direction for each individual emitter.Keywords：GaN;InGaN;photoluminescence;polarized emission;quantum dot
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Published：2024-09-30 - Abstract：To date, most current reports on the development and optimization of artificial lighting sources have focused on the energy performance levels and limited color qualities of white light-emitting diodes (LEDs). However, these properties are insufficient in terms of representing all performance levels required when adjusting white LEDs for healthy and smart lighting. Here, we introduce essential and advanced figures of merit pertaining to circadian performance as well as vision performance and color quality. We compare all possible properties of commercialized artificial lighting, daylight and four-package white LEDs which consist of long-wavelength pass dichroic filter (LPDF)-capped, phosphor-converted red, amber and green LEDs (pc-LEDs) and a blue LED. We show that these tunable four-package white LEDs produce a tunable circadian effect for melatonin suppression/secretion, a high color quality for color perception/reproduction, high efficiency for energy savings and tunable figures of merit for the smart LED lighting market.Keywords：circadian effect;color quality;solid-state lighting;vision performance;white LED
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Published：2024-09-30 - Abstract：Investigations of ultrafast processes occurring on the nanoscale require a combination of femtosecond pulses and nanometer spatial resolution. However, controlling femtosecond pulses with nanometer accuracy is very challenging, as the limitations imposed both by dispersive optics on the time duration of a pulse and by the spatial diffraction limit on the focusing of light must be overcome simultaneously. In this paper, we provide a universal method that allows full femtosecond pulse control in subdiffraction-limited areas. We achieve this aim by exploiting the intrinsic coherence of the second harmonic emission from a single nonlinear nanoparticle of deep subwavelength dimensions. The method is proven to be highly sensitive, easy to use, quick, robust and versatile. This approach allows measurements of minimal phase distortions and the delivery of tunable higher harmonic light in a nanometric volume. Moreover, the method is shown to be compatible with a wide range of particle sizes, shapes and materials, allowing easy optimization for any given sample. This method will facilitate the investigation of light–matter interactions on the femtosecond–nanometer level in various areas of scientific study.Keywords：diffraction limit;Fourier limit;multiphoton intrapulse interference phase scan;nanoparticle;nanophotonics;phase control;second harmonic generation;ultrafast
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Published：2024-09-30 - Abstract：We have developed a self-contained, liquid tunable microlens based on polyacrylate membranes integrated with compact on-chip thermo-pneumatic actuation fabricated using full-wafer processing. Silicone oil is used as the optical liquid, which is pushed or pulled into the lens cavity via an extended microfluidic channel structure without any pumps, valves or other mechanical means. The heat load generated by the thermal actuator is physically isolated from the lens chamber. The back focal length may be tuned from infinity to 4 mm with a maximum power consumption of 300 mW. The principal application is fine tuning of the back focal length, for which tuning time constants as small as 100 ms are suitable.Keywords：optofluidics;thermo-pneumatic actuation;tunable microlens;wafer-scale fabrication
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Published：2024-09-30 - Abstract：The modern information society is enabled by photonic fiber networks characterized by huge coverage and great complexity and ranging in size from transcontinental submarine telecommunication cables to fiber to the home and local segments. This world-wide network has yet to match the complexity of the human brain, which contains a hundred billion neurons, each with thousands of synaptic connections on average. However, it already exceeds the complexity of brains from primitive organisms, i.e., the honey bee, which has a brain containing approximately one million neurons. In this study, we present a discussion of the computing potential of optical networks as information carriers. Using a simple fiber network, we provide a proof-of-principle demonstration that this network can be treated as an optical oracle for the Hamiltonian path problem, the famous mathematical complexity problem of finding whether a set of towns can be travelled via a path in which each town is visited only once. Pronouncement of a Hamiltonian path is achieved by monitoring the delay of an optical pulse that interrogates the network, and this delay will be equal to the sum of the travel times needed to visit all of the nodes (towns). We argue that the optical oracle could solve this NP-complete problem hundreds of times faster than brute-force computing. Additionally, we discuss secure communication applications for the optical oracle and propose possible implementation in silicon photonics and plasmonic networks.Keywords：Hamiltonian path problem;NP complete;optical oracle
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Published：2024-09-30 - Abstract：We demonstrate a handheld on-chip biosensing technology that employs plasmonic microarrays coupled with a lens-free computational imaging system towards multiplexed and high-throughput screening of biomolecular interactions for point-of-care applications and resource-limited settings. This lightweight and field-portable biosensing device, weighing 60 g and 7.5 cm tall, utilizes a compact optoelectronic sensor array to record the diffraction patterns of plasmonic nanostructures under uniform illumination by a single-light emitting diode tuned to the plasmonic mode of the nanoapertures. Employing a sensitive plasmonic array design that is combined with lens-free computational imaging, we demonstrate label-free and quantitative detection of biomolecules with a protein layer thickness down to 3 nm. Integrating large-scale plasmonic microarrays, our on-chip imaging platform enables simultaneous detection of protein mono- and bilayers on the same platform over a wide range of biomolecule concentrations. In this handheld device, we also employ an iterative phase retrieval-based image reconstruction method, which offers the ability to digitally image a highly multiplexed array of sensors on the same plasmonic chip, making this approach especially suitable for high-throughput diagnostic applications in field settings.Keywords：computational imaging;high-throughput biodetection;lens-free imaging;on-chip sensing;plasmonics;point of care diagnostics;telemedicine
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Published：2024-09-30 - Abstract：At the end of the 1970s, it was confirmed that dielectric multilayers can sustain Bloch surface waves (BSWs). However, BSWs were not widely studied until more recently. Taking advantage of their high-quality factor, sensing applications have focused on BSWs. Thus far, no work has been performed to manipulate and control the natural surface propagations in terms of defined functions with two-dimensional (2D) components, targeting the realization of a 2D system. In this study, we demonstrate that 2D photonic components can be implemented by coating an in-plane shaped ultrathin (~λ/15) polymer layer on the dielectric multilayer. The presence of the polymer modifies the local effective refractive index, enabling direct manipulation of the BSW. By locally shaping the geometries of the 2D components, the BSW can be deflected, diffracted, focused and coupled with 2D freedom. Enabling BSW manipulation in 2D, the dielectric multilayer can play a new role as a robust platform for 2D optics, which can pave the way for integration in photonic chips. Multiheterodyne near-field measurements are used to study light propagation through micro- and nano-optical components. We demonstrate that a lens-shaped polymer layer can be considered as a 2D component based on the agreement between near-field measurements and theoretical calculations. Both the focal shift and the resolution of a 2D BSW lens are measured for the first time. The proposed platform enables the design of 2D all-optical integrated systems, which have numerous potential applications, including molecular sensing and photonic circuits.Keywords：Bloch surface wave;2D optics;manipulation;micro- and nano-optics;nanophotonics;platform
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Published：2024-09-30 - Abstract：The precise control and manipulation of micro- and nanoparticles using an optical endoscope are potentially important in biomedical studies, bedside diagnosis and treatment in an aquatic internal organ environment, but they have not yet been achieved. Here, for the first time, we demonstrate optical nonlinear endoscopic tweezers (ONETs) for directly controlling and manipulating aquatic micro- and nanobeads as well as gold nanorods. It is found that two-photon absorption can enhance the trapping force on fluorescent nanobeads by up to four orders of magnitude compared with dielectric nanobeads of the same size. More importantly, two-photon excitation leads to a plasmon-mediated optothermal attracting force on nanorods, which can extend far beyond the focal spot. This new phenomenon facilitates a snowball effect that allows the fast uploading of nanorods to a targeted cell followed by thermal treatment within 1 min. As two-photon absorption allows an operation wavelength at the center of the transmission window of human tissue, our work demonstrates that ONET is potentially an unprecedented tool for precisely specifying the location and dosage of drug particles and for rapidly uploading metallic nanoparticles to individual cancer cells for treatment.Keywords：endoscopy;gold nanorods;micro/nanotweezing;two-photon absorption
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Published：2024-09-30 - Abstract：The behavior of a negative refraction photonic crystal slab irradiated with out-of-plane incident beam is an unexplored subject. In such an experimental configuration, guided mode resonance appears in the reflection spectrum. We show that, in this case, the light coupled inside the photonic crystal is backpropagating. A relationship with the negative index properties is established using a new approach in which the guided resonance is recovered by modeling the photonic crystal layer with a simple Lorentz resonator using the Fresnel reflection formula.Keywords：diffraction gratings;guided mode resonance;negative index;photonic crystals
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Published：2024-09-30 - Abstract：Coherent radiation with frequencies ranging from 0.3 to 30 THz has recently become accessible using femtosecond laser technology. These terahertz (THz) waves have already been applied in spectroscopy and imaging and can be manipulated using static optical elements such as lenses, polarizers and filters. However, ultrafast modulation of THz radiation is required as well, for instance, in short-range wireless communication or for preparing shaped THz transients for the coherent control of numerous material excitations. Here, we demonstrate an all-optically created transient metamaterial that allows us to manipulate the polarization of THz waveforms with subcycle switch-on times. The polarization-modulated pulses are potentially interesting for controlling elementary motions such as the vibration of crystal lattices, the rotation of molecules and the precession of spins.Keywords：terahertz metamaterial;terahertz optics;terahertz polarization control
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Published：2024-09-30
Original Articles
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