Light‐switching‐light optical transistor based on metallic nanoparticle cross‐chains geometry incorporating Kerr nonlinearity

In this research work, we propose all‐optical transistor based on metallic nanoparticle cross‐chains geometry. The geometry of the proposed device consists of two silver nanoparticle chains arranged along the x‐ and z‐axis. The x‐chain contains a Kerr nonlinearity, the source beam is set at the left side of the later, while the control beam is located at the top side of the z‐chain. The control beam can turn ON and OFF the light transmission of an incoming light. We report a theoretical model of a very small all‐optical transistor proof‐of‐conceptmade of optical ‘light switching light'concept. We show that the transmission efficiency strongly depends on the control beam and polarization of the incoming light. We investigate the influence of a perfect reflector and reflecting substrate on the transmission of the optical signal when the control beam is turned ON and OFF. These new findings make our unique design a potential candidate for future highly‐integrated optical information processing chips.     

Nonlinear photonic waveguides for on‐chip optical pulse compression

All‐optical signal processing on nonlinear photonic chips is a burgeoning field. These processes include light generation, optical regeneration and pulse metrology. Nonlinear photonic chips offer the benefits of small footprints, significantly larger nonlinear parameters and flexibility in generating dispersion. The nonlinear compression of optical pulses relies on a delicate balance of a material's nonlinearity and optical dispersion. Recent developments in dispersion engineering on a chip are proving to be key enablers of high‐efficiency integrated optical pulse compression. We review the recent advances made in optical pulse compression based on nonlinear photonic chips, as well as the future outlook and challenges that remain to be solved.

     

Nanoscale C‐Rich SixC1−x Bus/Ring Waveguide Based Cross‐Wavelength Data Converter

The carbon‐rich silicon carbide (C‐rich Si_xC_1?x) micro‐ring channel waveguide with asymmetric core aspect is demonstrated for all‐optical cross‐wavelength pulsed return‐to‐zero on‐off keying (PRZ‐OOK) data conversion. Enhanced nonlinear optical Kerr switching enables 12‐Gbit per second data processing with optimized modulation depth. The inverse tapered waveguide at end‐face further enlarges the edge‐coupling efficiency, and the asymmetric channel waveguide distinguishes the polarization modes. To prevent data shape distortion, the bus/ring gap spacing is adjusted to control the quality factor (Q‐factor) of the micro‐ring. Designing the waveguide cross section at 500 × 350 nm² provides the C‐rich Si_xC_1?x channel waveguide to induce strong transverse electric mode (TE‐mode) confinement with a large Kerr nonlinearity of 2.44 × 10^?12 cm² W^?1. Owing to the trade‐off between the Q‐factor and the on/off extinction ratio, the optimized bus/ring gap spacing of 1400 nm is selected to provide a coupling ratio at 5–6% for compromising the modulation depth and the switching throughput. Such a C‐rich Si_xC_1?x micro‐ring with asymmetric channel waveguide greatly enhances the cross‐wavelength data conversion efficiency to favor its on‐chip all‐optical data processing applications for future optoelectronic interconnect circuits.     

Quantum photonic network on chip

We provide an overview of quantum photonic network on chip. We begin from the discussion of the pros and cons of several material platforms for engineering quantum photonic chips. Then we introduce and analyze the basic building blocks and functional units of quantum photonic integrated circuits. In the main part of this review, we focus on the generation and manipulation of quantum states of light on chip and are particularly interested in some applications of advanced integrated circuits with different functionalities for quantum information processing, including quantum communication, quantum computing, and quantum simulation. We emphasize that developing fully integrated quantum photonic chip which contains sources of quantum light, integrate circuits, modulators, quantum storage, and detectors are promising approaches for future quantum photonic technologies. Recent achievements in the large scale photonic chips for linear optical computing are also included. Finally, we illustrate the challenges toward high performance quantum information processing devices and conclude with promising perspectives in this field.     

Photonic‐on‐a‐chip: a thermal actuated Mach‐Zehnder interferometer and a molecular thermometer based on a single di‐ureasil organic‐inorganic hybrid

An integrated photonic‐on‐a‐chip device based on a single organic‐inorganic di‐ureasil hybrid was fabricated for optical waveguide and temperature sensing. The device is composed by a thermal actuated Mach‐Zehnder (MZ) interferometer operating with a switching power of 0.011 W and a maximum temperature difference between branches of 0.89 ºC. The MZ interferometer is covered by a Eu³⁺/Tb³⁺ co‐doped di‐ureasil luminescent molecular thermometer with a temperature uncertainty of 0.1ºC and a spatial resolution of 13 µm. This is an uncommon example in which the same material (an organic‐inorganic hybrid) that is used to fabricate a particular device (a thermal‐actuated MZ interferometer) is also used to measure one of the device intrinsic properties (the operating temperature). The photonic‐on‐a‐chip example discussed here can be applied to sense temperature gradients with high resolution (10⁻³ ºC·µm⁻¹) in chip‐scale heat engines or refrigerators, magnetic nanocontacts and energy‐harvesting machines.     

Nonlinear switching and solitons in PT‐symmetric photonic systems

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.

     

Ultrafast optical switching in Kerr nonlinear photonic crystals

Nonlinear photonic crystals made from polystyrene materials that have Kerr nonlinearity can exhibit ultrafast optical switching when the samples are pumped by ultrashort optical pulses with high intensity due to the change of the refractive index of polystyrene and subsequent shift of the band gap edge or defect state resonant frequency. Polystyrene has a large Kerr nonlinear susceptibility and almost instantaneous response to pump light, making it suitable for the realization of ultrafast optical switching with a response time as short as a few femtoseconds. In this paper, we review our experimental progress on the continual improvement of all-optical switching speed in two-dimensional and three-dimensional polystyrene nonlinear photonic crystals in the past years. Several relevant issues are discussed and analyzed, including different mechanisms for all-optical switching, preparation of nonlinear photonic crystal samples by means of microfabrication and self-assembly techniques, characterization of optical switching performance by means of femtosecond pump-probe technique, and different ways to lower the pump power of optical switching to facilitate practical applications in optical information processing. Finally, a brief summary and a perspective of future work are provided.     

Ultrafast optical switching in Kerr nonlinear photonic crystals

Nonlinear photonic crystals made from polystyrene materials that have Kerr nonlinearity can exhibit ultrafast optical switching when the samples are pumped by ultrashort optical pulses with high intensity due to the change of the refractive index of polystyrene and subsequent shift of the band gap edge or defect state resonant frequency. Polystyrene has a large Kerr nonlinear susceptibility and almost instantaneous response to pump light, making it suitable for the realization of ultrafast optical switching with a response time as short as a few femtoseconds. In this paper, we review our experimental progress on the continual improvement of all-optical switching speed in two-dimensional and three-dimensional polystyrene nonlinear photonic crystals in the past years. Several relevant issues are discussed and analyzed, including different mechanisms for all-optical switching, preparation of nonlinear photonic crystal samples by means of microfabrication and self-assembly techniques, characterization of optical switching performance by means of femtosecond pump-probe technique, and different ways to lower the pump power of optical switching to facilitate practical applications in optical information processing. Finally, a brief summary and a perspective of future work are provided.     

On‐chip stimulated Brillouin Scattering for microwave signal processing and generation

Demonstration of continuously tunable delay, low‐noise lasers, dynamically controlled gratings, and optical phase shifting using the stimulated Brillouin scattering (SBS) process has lead to the emergence of SBS as a promising technology for microwave photonics. On‐chip realization of SBS enables photonic integration of microwave photonic signal processing and offers significantly enhanced performance and improved efficiency. On‐chip stimulated Brillouin scattering is reviewed in the context of slow‐light based tunable delay, low‐noise narrow linewidth lasers and filtering for integrated microwave photonics. A discussion on key material and device properties, necessary to enable on‐chip Brillouin scattering using both the single‐pass and resonator geometry, is presented along with an outlook for photonic integration of microwave signal processing and generation in other platforms.     

Frequency‐sensitive switching control effect induced by two‐photon resonance in an EIT‐based layered medium

The optical response of an atomic vapor can be coherently manipulated by tunable quantum interference occurring in atomic transition processes. A periodic layered medium whose unit cells consist of a dielectric and an EIT (electromagnetically induced transparency) atomic vapor is designed for light propagation manipulation. Such an EIT‐based periodic layered medium exhibits a flexible frequency‐sensitive optical response, where a very small change in probe frequency can lead to a drastic variation of reflectance and transmittance. As the destructive quantum interference relevant to two‐photon resonance arises in EIT atoms interacting with both control and probe fields, the controllable optical processes that depend sensitively on the external control field will take place in this EIT‐based periodic layered medium. Such a frequency‐sensitive and field‐controlled optical behavior of reflection and transmission in the EIT photonic crystal can be applicable to designs of new devices such as photonic switches, photonic logic gates and photonic transistors, where one laser field can be controlled by the other one, and would have potential applications in the areas of integrated optical circuits and other related techniques (e.g., all‐optical instrumentations).     

On‐chip single photon sources using planar photonic crystals and single quantum dots

We review the basic light‐matter interactions and optical properties of chip‐based single photon sources, that are enabled by integrating single quantum dots with planar photonic crystals. A theoretical framework is presented that allows one to connect to a wide range of quantum light propagation effects in a physically intuitive and straightforward way. We focus on the important mechanisms of enhanced spontaneous emission, and efficient photon extraction, using all‐integrated photonic crystal components including waveguides, cavities, quantum dots and output couplers. The limitations, challenges, and exciting prospects of developing on‐chip quantum light sources using integrated photonic crystal structures are discussed.     

Ultra‐fast nano‐optics

Ultra‐fast nano‐optics is a comparatively young and rapidly growing field of research aiming at probing, manipulating and controlling ultrafast optical excitations on nanometer length scales. This ability to control light on nanometric length and femtosecond time scales opens up exciting possibilities for probing dynamic processes in nanostructures in real time and space. This article gives a brief introduction into the emerging research field of ultrafast nano‐optics and discusses recent progress made in it. A particular emphasis is laid on the recent experimental work performed in the authors' laboratories. We specifically discuss how ultrafast nano‐optical techniques can be used to probe and manipulate coherent optical excitations in individual and dipole‐coupled pairs of quantum dots, probe the dynamics of surface plasmon polariton excitations in metallic nanostructures, generate novel nanometer‐sized ultrafast light and electron sources and reveal the dipole interaction between excitons and surface plasmon polaritons in hybrid metal‐semiconductor nanostructures. Our results indicate that such hybrid nanostructures carry significant potential for realizing novel nano‐optical devices such as ultrafast nano‐optical switches as well as surface plasmon polariton amplifiers and lasers.     

A three‐level dark state and double‐control single‐photon logic gates via quantum coherent control

Multilevel quantum coherence and its quantum‐vacuum counterpart, where a three‐level dark state is involved, are suggested in order to achieve new photonic and quantum optical applications. It is shown that such a three‐level dark state in a four‐level tripod‐configuration atomic system consists of three lower levels, where constructive and destructive quantum interference between two control transitions (driven by two control fields) arises. We point out that the controllable optical response due to the double‐control tunable quantum interference can be utilized to design some fascinating new photonic devices such as logic gates, photonic transistors and switches at quantum level. A single‐photon two‐input XOR logic gate (in which the incident “gate” photons are the individual light quanta of the two control fields) based on such an effect of optical switching control with an EIT (electromagnetically induced transparency) microcavity is suggested as an illustrative example of the application of the dark‐state manipulation via the double‐control quantum interference. The present work would open up possibility of new applications in both fundamental physics (e.g., field quantization and relevant quantum optical effects in artificial systems that can mimic atomic energy levels) and applied physics (e.g., photonic devices such as integrated optical circuits at quantum level).     

Tuning of near‐ and far‐field properties of all‐dielectric dimer nanoantennas via ultrafast electron‐hole plasma photoexcitation

All‐optical ultrafast signal modulation and routing by low‐loss nanodevices is a crucial step towards an ultracompact optical chip with high performance. Here, we propose a specifically designed silicon dimer nanoantenna, which is tunable via photoexcitation of dense electron‐hole plasma with ultrafast relaxation rate. On the basis of this concept, we demonstrate the effect of beam steering by up to 20 degrees through simple variation of the intensity of incident light. The effect, which is suitable for ultrafast light routing in an optical chip, is demonstrated both in the visible and near‐IR spectral regions for silicon‐ and germanium‐based nanoantennas. We also reveal the effect of electron‐hole plasma photoexcitation on the local density of states (LDOS) in the dimer gap and find that the orientation averaged LDOS can be altered by 50%, whereas modification of the projected LDOS can be even more dramatic, almost five‐fold for transverse dipole orientation. Moreover, our analytical model sheds light on the transient dynamics of the studied nonlinear nanoantennas, yielding all temporal characteristics of the suggested ultrafast nanodevice. The proposed concept paves the way to the creation of low‐loss, ultrafast, and compact devices for optical signal modulation and routing.

     

Nonreciprocal transmission in a nonlinear photonic‐crystal Fano structure with broken symmetry

Nanostructures that feature nonreciprocal light transmission are highly desirable building blocks for realizing photonic integrated circuits. Here, a simple and ultracompact photonic‐crystal structure, where a waveguide is coupled to a single nanocavity, is proposed and experimentally demonstrated, showing very efficient optical diode functionality. The key novelty of the structure is the use of cavity‐enhanced material nonlinearities in combination with spatial symmetry breaking and a Fano resonance to realize nonreciprocal propagation effects at ultralow power and with good wavelength tunability. The nonlinearity of the device relies on ultrafast carrier dynamics, rather than the thermal effects usually considered, allowing the demonstration of nonreciprocal operation at a bit‐rate of 10 Gbit s⁻¹ with a low energy consumption of 4.5 fJ bit⁻¹.

     

Stability of Optically Injected Two‐State Quantum‐Dot Lasers

Simultaneous two‐state lasing is a unique property of semiconductor quantum‐dot (QD) lasers. This not only changes steady‐state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single‐state laser devices, we find a strong suppression of dynamical instabilities in two‐state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all‐optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required.     

Self‐Collimation in Photonic Crystals: Applications and Opportunities

A comprehensive review considering recent advances in self‐collimation and its applications in optical integration is covered in the current article. Self‐collimation is compared to the conventional technique of photonic bandgap engineering to control the light propagation in photonic crystal‐based structures. It is fully discussed how the self‐collimation phenomenon can be tailored to be independent of the incident angle and polarization. This adds substantial flexibility to the structure to overcome light coupling challenges and simultaneously aids in the omission of bulk and challenging elements, including polarizers and lenses from optical integrated circuits. Additionally, designed structures have the potential to be rescaled to operate in any desired frequency range thanks to the scalability rule in the field of electromagnetics. Moreover, it is shown that one can boost the coupling efficiency by applying an anti‐reflection property to the structure, which provides not only efficient index matching but also the matching between external waves with uniform amplitude and Bloch waves with periodic amplitude.     

Large Kerr effect in bulk Se-based chalcogenide glasses

High-speed optical communication requires ultrafast all-optical processing and switching capabilities. The Kerr nonlinearity, an ultrafast optical nonlinearity, is often used as the basic switching mechanism. A practical, small device that can be switched with ~1-pJ energies requires a large Kerr effect with minimal losses (both linear and nonlinear). We have investigated theoretically and experimentally a number of Se-based chalcogenide glasses. We have found a number of compounds with a Kerr nonlinearity hundreds of times larger than silica, making them excellent candidates for ultrafast all-optical devices.     

Design of high-Q silicon-polymer hybrid photonic crystal nanobeam microcavities for low-power and ultrafast all-optical switching

Owing to the unique optical properties high-Q photonic crystal nanobeam microcavities have been demonstrated in a variety of materials. In this paper the design of high-Q silicon-polymer hybrid photonic crystal nanobeam microcavities is investigated using the three-dimensional plane-wave expansion method and finite-difference time-domain method. We first discuss the design of high-Q nanobeam microcavities in silicon-on-insulator, after which the polymer is introduced into the air void to form the hybrid structures. Quality factor as high as 1 × 10⁴ has been obtained for our silicon-polymer hybrid nanobeam microcavities without exhaustive parameter examination. In addition the field distribution of resonant mode can be tuned to largely overlap with polymer materials. Because of the overwhelmingly large Kerr nonlinearity of polymer over silicon, the application in all-optical switching is presented by studying the shift of the resonant frequency on the change of refractive index of polymer. The minimum switching intensity of only 0.37 GW/cm² is extracted for our high-Q hybrid microcavities and the corresponding single pulse energy is also discussed according to the pumping methods. The total switching time is expected to be restricted by the photon lifetime in cavity due to the ultrafast response speed of polymer. Our silicon-polymer hybrid nanobeam microcavities show great promise in constructing small-sized all-optical devices or circuits with advantages of possessing low-power and ultrafast speed simultaneously.     

Strong light‐matter coupling between a molecular vibrational mode in a PMMA film and a low‐loss mid‐IR microcavity

Microcavity devices exhibiting strong light‐matter coupling in the mid‐infrared spectral range offer the potential to explore exciting open physical questions pertaining to energy transfer between heat and light and can lead to a new generation of efficient wavelength tunable mid‐infrared sources of coherent light based on polariton Bose‐Einstein Condensation. Vibrational transitions of organic molecules, which often have strong absorption peaks in the infrared and considerably narrower linewidths than organic excitonic resonances, can generate polaritonic states in the mid‐infrared spectral range using microcavity devices. Here, narrow linewidth polaritonic resonances are exhibited in the mid‐infrared by coupling the carbonyl stretch vibrational transition of a polymethyl methacrylate film to the photonic resonance of a low optical‐loss mid‐infrared microcavity, which consisted of two Ge/ZnS dielectric Bragg reflectors. Rabi‐splitting of 14.3 meV is observed, with a 4.4 meV polariton linewidth at anti‐crossing. The large Rabi‐splitting relative to linewidth indicates efficient impedance‐matching between the bare vibrational and photonic states, and suggests molecular‐vibration polaritons incorporated in dielectric microcavities can be an enabling step towards realizing polariton optical switching and polariton condensation in the mid‐infrared spectral range.