Search

A novel nonlinear optical switch based on a single mode fiber – graded index multimode fiber (GIMF) – single mode fiber (SMS) twined into polarization controller (PC) was proposed as a saturable absorber (SA), to generate ultrashort pulse in fiber laser. The SA device geometry, where a sandwiched GIMF section spliced to two standard SMF at both ends of GIMF, was coiled into a PC. By properly tuning the paddles of PC, mode-locking can be easily realized and the nonlinear saturable absorption characteristics of SMS-SA was changed. In the experiment, the modulation depth of the SMS-SA containing 0.6 m GIMF can be observed 9%, 10.5%, 21.7%, respectively. Based on SMS-SA mode-locking, the stable ultrafast pulse duration of 559 fs, with the FWHM bandwidth of 6.84 nm were generated. The fundamental repetition rate of 25 MHz and wavelength-tuning range of 14 nm can be obtained by adjusting the paddles. The SMS-SA excellent tunable nonlinear optical properties and all-fiber structure have strong potential application in the field of ultrafast photonics.

Providing a low-cost, reliable and end-to-end quality of service (QoS) guaranteed connectivity is going to be a major challenge in optical transport due to the immense growth in number of connected devices and traffic volume triggered by fifth-generation mobile networks (5G) and cloud networks. First, we discuss the architectures of the 5G transport network and the data center network, to capture the full value of connectivity. The paper offers an overview of the network requirements and how the integrated photonic platforms, along with the advanced modulation formats, play a key role to support the unprecedented requirements of 5G and massive cloud deployment. Second, we provide an overview of the recent work on the development of high-speed silicon photonic (SiPh) modulators to generate and transport PAM-4 signals. Third, recent advancements of the photodetectors, optical hybrids, and integrated coherent receivers on the silicon-on-insulator (SOI) platform are also described. The results suggest that, in the first access and aggregation segments of the network, integrated silicon-based modulators aided by PAM-4 modulation formats can support the stringent requirements of new generation transport networks in terms of speed, footprint and power consumption.

We propose a new strip–slot hybrid waveguide with extreme large and flat dispersion over broad wavelength range. The strong resonance coupling between the strip and slot modes has been employed to obtain a high dispersion at desired wavelength. The properties of dispersion are analyzed using the finite-difference time-domain method. All numerical simulation results reveal that for the optimized waveguide structure, a maximum dispersion of − 1 . 54 × 1 0 6 ps nm − 1 km − 1 and dispersion full width at half-maximum of 2.5 nm at 1 . 55 μ m are obtained. By cascading the strip–slot hybrid waveguides with varied width and height, a large and flattened dispersion of − 9 . 8 × 1 0 5 ps nm − 1 km − 1 covering 350 nm is achieved. Moreover, dispersion compensation of 100 Gbit/s return-to-zero on-off-keying optical-time-division-multiplexing signals after 50-km single mode fiber transmission, and after 7-km hollow-core photonic band-gap fiber transmission are demonstrated, separately. Such a waveguide will find widespread applications in on-chip all-optical signal processing.

A novel scheme based on a dual-parallel Mach–Zehnder modulator (DPMZM) is proposed for angle-of-arrival (AOA) measurement without direction ambiguity. The signals received by two antennas are modulated on the two sub-MZMs of a DPMZM. When the main bias of the DPMZM is properly set, the positive and negative side bands will produce two different phase differences. We can obtain two different power curves and achieve AOA measurement without ambiguity by measuring the power. The phase measurement range of the system is about 330 degrees (the AOA measurement range is 165 degrees) and the measurement error is less than 2.24 degrees (0.68% of the full phase measurement range).

The photonic devices play a key role in optical communication networks and quantum networks. Here we analyze an optomechanical coupling between levitated nano-mechanical resonator and a nitrogen-vacancy(NV) center that exhibits a giant enhanced nonlinearity. Then we propose an experimentally accessible optical switch scheme at the single-photon level due to the optomechanically induced Kerr effect and show the pump power for the switch is reduced to 1 0 − 19 W. This is a promising device for future optomechanics-based photonic quantum computing and quantum networks.

A simple method based on an integrated polarization-division multiplexing Mach–Zehnder modulator (PDM-MZM) to produce a carrier-frequency-doubled vector signal is presented and experimentally demonstrated. In this structure, the upper sub-MZM is driven by I/Q signals and biased at the quadrature point to modulate a baseband vector signal on the optical carrier. The lower sub-MZM is driven by a LO signal and is biased at the maximum transmission point (MATP) to generate the optical carrier and second-order sidebands. By filtering the negative second-order sideband via an optical bandpass filter (OBPF) and suppressing the optical carrier via polarization controller (PC), a carrier-frequency-doubled vector signal is generated at the photodetector. Due to the adoption of LO frequency-doubled technique, the system’s requirement of a high-frequency LO is relaxed. In a proof-of-concept experiment, 300 MSym/s QPSK signal with a carrier frequency of 16 GHz is obtained by 8 GHz LO signal. Besides, 25-km fiber transmission of the generated QPSK signal is demonstrated. When the optical power obtained after fiber transmission is higher than -4 dBm, the BER after demodulation is less than 8 × 10−10. Moreover, generation of vector signal with other formats is verified.

We numerically investigate metasurfaces based on the well-known V-shaped antennas operating in high-order modes and short-period modes for shaping the wavefront of light. By careful arrangement of the V-shaped antennas, we design two novel super cells with large phase gradients. As a proof of concept, we design two novel metasurfaces by simulation to operate in high-order modes and short-period modes. In particular, the short-period combination can be equivalent to a metasurface operating in the second-order mode. Based on the new concept, we further arrange two azimuthal phase gradient metasurfaces to generate optical vortex beams with topological charges n = 3 and n = 2. Our results will further extend photonic research and new applications of metasurfaces.

We propose a structure of graphene embedded in dielectric resonant waveguide gratings to enhance the nonlinear interactions in graphene. Third harmonic generation (THG) from graphene is significantly enhanced in the waveguide mode under transverse electric polarization. Compared with the graphene on a flat dielectric film, the enhancement factor is up to 109. We in detail studied the THG intensity influenced by the Fermi level of graphene, the position of graphene, and multimode of waveguide. Our investigation has great significance for design and experimental fabrication of graphene-based nonlinear photonic devices.

A novel approach for photonic quantization using dual-output Mach–Zehnder modulators (DOMZMs) and balanced photodetectors (BPDs) is proposed and experimentally demonstrated. Based on the phase-shifting technique, all DOMZMs used in the scheme have identical half-wave voltages but are biased at different voltages. Due to the use of BPDs and DOMZMs with complementary outputs, the threshold voltages of comparators can be kept at zero, which eliminates the influence of power fluctuation of the input sampling pulses and improves the effective number of bits (ENOB) of the analog-to-digital conversion (ADC) system. After the comparators, a digital Gray code that represents the analog signal to be digitized is obtained. Proof-of-concept experiments with 8 and 16 quantization levels are implemented to verify the feasibility of the proposed approach. Bit resolution, ENOB degradation induced by bias voltage errors and potential for photonic integration are also discussed.

Dense integration of silicon photonic devices is the key enabling technology for next-generation high-performance computers. In this paper, we propose a double-layer grating coupler for the future multi-layer photonic integrated system. With a pair of one-dimensional (1-D) gratings orthogonally vertical-stacked, the device can couple light between single-mode fiber and two separate waveguide layers, realizing polarization splitting and rotation in different layers simultaneously. Benefiting from the perfectly vertical coupling scheme and optimal fiber position (OFP) overlapping design, the coupling efficiency peak of the upper and lower grating are calculated to be 28% and 25% respectively. Assisted with a DBR bottom mirror, the coupling efficiency of the two gratings can be further enhanced to 33.2% and 28.9% respectively. For real application, the misalignment tolerance on grating overlapping and the incidence angle are carefully investigated. To achieve power balance between the two grating layers, the impact of top cladding thickness is analyzed and an optimized thickness of 0. 6 μ m is chosen. From the simulation result of a back-to-back DLGC circuit, the coupling performance shows considerable robustness to the input polarization state and the PDL is under 0.5 dB within the wavelength range from 1536 nm to 1558 nm. Such a device can be a very promising solution to achieve polarization-independent coupling in the future three-dimensional (3-D) high density photonic integrated circuits.

Using numerical and experimental techniques we study plasmonic and photonic coupling of plasmonic supercells formed in one dimensional arrays (chains) of flat metallic nanoantennas. These supercells support their own collective resonances and are associated with two different types of near field couplings of the nanoantennas. When the incident light is polarized along the long axes the nanoantennas, these cells are formed via plasmonic bonding (bonding supercells). For light polarization along the short axes of the nanoantennas, the supercells are generated via corner edge-mode coupling, generating a collective mode across the one-dimensional arrays of the nanoantennas (cavity supercells). We study plasmonic lattices wherein these supercells act as the units that are periodically repeated along one dimension. By changing the distances between these units (lattice constant), we study the optical responses of such lattices as the nature of interaction between supercells are changed from pure plasmonic (near field) to diffractive (far field) coupling. For lattices with bonding supercells, the former leads to strong suppression of the side modes. In the case of diffractive coupling, our results suggest formation surface lattice resonance via hybridization of resonances of the cavity supercells with Rayleigh anomaly.

We report a new type of nano-optical tip, the quantum dot decorated nano-pyramid fiber tip, for scanning near-field optical microscopy. The nano-pyramid tip has a large apex angle (70.5 degree), and consequently exhibits a significant improvement (17-fold) of the signal collection efficiency compared to conventional tapered fiber tips. Moreover, thanks to the template-based fabrication method and the surface treatment technique, the quantum-dot decorated nano-pyramid tip enjoys a clean and smooth surface, and can be produced with high accuracy and high reproducibility. Experimental results show that, with the nano-pyramid tip, the optical field distribution of a photonic nanostructure can be mapped with a 20 nm resolution ( λ /20). It provides a powerful and reliable tool for near-field optical measurements.

We present a simple yet effective approach to realize all-optical diode (AOD) based on an asymmetric nanocavity–waveguide (WG) structure. We show that by adjusting the distance between the nonlinear nanocavity and its surrounding rods, the transmission characteristics of the input and output WGs (which are equivalent to two F–P cavities with different lengths) can be precisely tuned, and as a result, the coupling strengths between the nanocavity and its connected WGs become quite different. This makes the excitation of the bistable state inside cavity is sensitive to the launching direction of the signal light, and makes the nonreciprocal transmission of the signal light possible. In this way, the maximum transmission contrast over 20dB can be achieved for either forward or backward conducted AOD, with a broad operation bandwidth over 5 nm. The approach proposed here is promising in the fields of advanced photonic circuits, all-optical information processing, and optical communications.

We demonstrate transparent in-contact electrical interconnects over SiN micro-ring resonators using metallic carbon nano-tubes (CNTs). Self-assembled stripes of metallic CNTs are directly in contact with the waveguide operating around 1550 nm wavelength. The absorption by the CNTs around 1550 nm is negligible for a coverage of about 2 % of the micro-ring. The optical performance of the resonator is unaffected till a current density of 35 μ A ∕ μ m . Semi-conducting CNTs with a similar coverage also have negligible absorption around 1550 nm . These metallic and semi-conducting CNTs hold promise for the implementation of transparent electronic circuits over SiN-photonic platform.

A photonic approach to generate millimeter-wave (MMW) ultra-wideband (UWB) monocycle and doublet signals using stimulated Brillouin scattering (SBS) selective sideband amplification technique and delay-line filter is proposed and theoretically analyzed. In the proposed approach, a dual-drive Mach–Zehnder modulator (DDMZM) is used as a first-order differentiator to produce a monocycle UWB signal. Then the generated monocycle signal is single-sideband (SSB) modulated by SBS effect for up-conversion. A balanced photodetector (BPD) is further employed for both photodetection and first-order differentiation. Consequently, an MMW-UWB monocycle signal or an MMW-UWB doublet signal can be attained in electrical field with controlling an optical switch. The frequency spectra of the generated MMW-UWB monocycle and doublet signals meet well with the Federal Communication Committee (FCC) mask with power efficiency of 50.63% and 40.53%. Besides, the produced MMW-UWB signals can be employed to realize multiple modulation formats, such as on–off keying modulation (OOK), pulse position modulation (PPM) and pulse amplitude modulation (PAM).

Achieving multiple diversified functionalities in a single flat device is crucial and practical for integration. Here we demonstrate a planar polarization beam splitter (PBS) capable of efficiently reflecting the x-linearly polarized (XLP) light while transmitting the orthogonal one. Other than separating the two orthogonal linearly polarized lights, a general design scheme is proposed, with which one can achieve disparate wavefront steering in transmission and reflection modes. For y-linearly polarized (YLP) incident lights, wavefront steering such as beam deflecting, beam focusing and vortex beam generating are exhibited in transmission mode. Switching the incident lights to XLP one, the metasurfaces exhibit disparate functionality, operating in reflection mode with the incident lights back reflected. With the merit of high efficient and polarization-dependent disparate functionality, the designed PBS can motivate the realizations of high-performance bifunctional metadevices and hold potential applications in optoelectronic and photonic circuits.

An approach for photonic generation of binary modulation microwave signals with high frequency multiplication factors is proposed and investigated. The key components are a polarization division multiplexing (PDM) dual parallel Mach–Zehnder modulator (DPMZM) and a polarization modulator (PolM). The PDM-DPMZM is employed to produce two orthogonally polarized lightwaves with their polarization directions aligned with the two principle axes of the following PolM. Then the two lightwaves are sent into the PolM for complementary phase coding. A theoretical analysis and a simulation work are performed to demonstrate the generation of microwave amplitude shift keying (ASK) signal with frequency multiplication factor of eight, frequency shift keying (FSK) signal with frequency multiplication factors of four/eight and phase shift keying (PSK) signal with frequency multiplication factor of four. The modulation format can be switched simply by adjusting the system parameters without revising the structure. In addition, the bit rate and the carrier frequency can be tuned flexibly and independently, and good frequency tunability is realized.

Er 3 + -doped silica glass microspheres ( μ S) with diameters of ∼ 25– 40 μ m were fabricated by using an electrical discharge method. The single-mode optical tapered fibers were used to guide the pumped laser into the μ S surface and collect the resulting lasing emission. The observation of whispering-gallery-mode (WGM) at telecom regime is quantified. With the presented scheme, the selective single- or multi-emitted modes of the μ S laser can be obtained by adjusting the coupling gap between the collection tapered fiber and the μ S surface. To overcome the collection tapered fiber’s vibration at close range of the coupling gap, the guiding and coupling losses, while being compact enough to fit with complementary metal oxide semiconductor (CMOS) device, the integration of a μ S with silicon-on-insulator (SOI) slotted photonic crystal waveguides is proposed and modeled with the help of finite-difference time-domain (FDTD) simulations. The designed structures may find application for the promising photonic devices such as the ultrahigh sensitivity sensors, the lasing sources, and towards advanced quantum communications.

An approach is presented that allows an electrically variable liquid crystal lens to operate as a spherical lens, then be switched into a variable prism, axicon, etc. This is achieved by a simple phase optimization algorithm enabled by the presence of a weakly conductive layer in the so called “modal control” lens approach with a segmented peripheral electrode. The proposed design and control method enable important additional control tools via the choice of the driving frequency and voltage values. Because the component has no electrodes in the clear aperture area, this allows the generation of a rich variety of interchangeable wavefronts and beams (such as Gaussian, Bessel, Airy, etc.) transforming it into a powerful adaptive optical device that can be used in many photonic applications.

A scheme of relay-assisted transmission system with few-mode all-optical relay is proposed in this paper to resist turbulence for atmospheric channels. The all-optical relay is composed of few-mode EDFA and photonic lantern which could amplify the distorted light field after atmospheric channels and covert the distorted light field to fundamental Gaussian fields. At the relay, using few-mode all-optical relay leads to the improvement of the turbulence induced fading which brings improved system performance. A dual-hop model for all-optical relaying system with few-mode EDFA and photonic lantern is derived. The communication performance is calculated with the help of turbulence phase screens to model atmospheric turbulence channel. Numerical results show that power budgets are increased by more than 4 d B for fixed gain amplification systems compared with all-optical relaying systems with single-mode all-optical relay and compared with few-mode all-optical relaying systems including few-mode EDFA only. Moreover, the BER performance is the best when mode-dependent gain (MDG) of few-mode EDFA is zero and becomes worse with the increase of MDG.

We study the steady-state photon distributions in two coupled systems consisting of three or four single-mode cavities. We find that it is viable to realize a single or double dark mode with vanishing photons in one cavity while arbitrary photons in other cavities under specific conditions. Such dark modes arise from perfect destructive interference between different coupling pathways and are in analogy to atomic dark states in the Λ or tripod systems. It is of more interest that a sharp dark-mode dip may be attained in the three-cavity system and two dark modes may interplay to yield a sharp bright-mode peak in the four-cavity system. The flexible tunability of such dips and peaks is beneficial to design sensitive photonic devices of switching or measuring, in a way different from coupled-resonator-induced transparency and absorption.

A novel photonic approach to generate frequency and bandwidth multiplying dual-chirp microwave for application in dual-band radar system is proposed using an integrated dual-polarization quadrature phase shift keying (DP-QPSK) modulator. The proposed approach is based on optical frequency multiplying and polarization selection. In the approach, the baseband signal and RF signal are injected into the DP-QPSK modulator to generate optical broad spectra and sidebands respectively. By adjusting the bias points of the DP-QPSK modulator, after polarization selection and optical to electrical conversion, frequency-quadrupling bandwidth-octupling and frequency-double bandwidth-quadrupling or frequency-tripling bandwidth-sextupling and frequency-fundamental bandwidth-doubling dual-chirp signals can be generated in the single structure respectively. The proposed approach is verified by simulations. Dual-chirp microwaves with central frequency–bandwidth of 32 GHz-8 GHz, 16 GHz-4 GHz or 24 GHz-6 GHz, 8 GHz-2 GHz are generated in the two ports respectively. Their autocorrelation results manifest good pulse compression capabilities. The central frequency, bandwidth, chirp rate and time duration can be tuned independently. The generated dual-chirp signals show good performance on the range-Doppler coupling and can significantly improve the range-Doppler resolution in dual-band radar system.

A process of geometric phase generation in a composite matter-field system is considered. Two atomic modes correspond to different localizations of a single Bose–Einstein condensate (BEC). One of the trapping localizations is formed by a photonic mode of a ring cavity. The photonic mode is governed by an external harmonic field source, by dissipation and by the number of localized atoms due to their non-resonant interaction with photons. This interaction gives rise to entanglement between the BEC and the photonic mode. By varying the intensity and frequency of the external source, it is possible to create a geometric phase for the optical mode. Because of the entanglement between the state of atomic and photonic modes, geometric phase acquired by the latter causes modification of the BEC state. This modification can be revealed by studying the tunneling between the atomic localizations.

A ternary molybdenum tungsten selenide (MoWSe2) alloy is proposed and demonstrated as a saturable absorber (SA) to induce Q-switching in the 1. 0 μ m , 1. 5 μ m and 2. 0 μ m regions. The MoWSe2 based SA is fabricated by mechanical exfoliation and sandwiched between two fiber ferrules to complete the fiberized SA assembly. The MoWSe2-SA is integrated into ytterbium, erbium and thulium-doped fiber laser cavities, and stable self-starting Q-switched pulses are observed at 1038 nm, 1554 nm and 1964 nm respectively. Maximum repetition rates at 120.2 kHz, 48 kHz and 61.5 kHz are observed at these wavelengths, along with corresponding pulse widths as narrow as 0.96 μ s, 1.9 μ s and 2.4 μ s respectively. These results validate the performance of MoWSe2 as a broadband SA for Q-switching operation, offering new opportunities of ternary transition metal dichalcogenide alloys in future photonics devices.

In this paper, the optical bistability response of a nonlinear photonic crystal slab-reflector-based Fabry–Perot cavity (PhCS-FPC) based on cavity resonances was numerically simulated. Three-dimensional finite-difference time domain method (3D-FDTD) was applied to investigate the effect of the cavity length, wavelength, and maximum intensity of the incident light on the optical bistability behavior of PhCS-FPC around cavity resonances. Results showed that, by carefully adjusting the cavity length, operating wavelength, and maximum input intensity, an efficient optical bistable system at telecommunication wavelength (1550 nm) with a low threshold intensity of about 30 kW/cm2 is achieved. For the first time, numerical calculations showed that the bistable switching intensity and the width of the bistable region are dependent on the maximum intensity of the input field. Low bistable switching intensity, insensitivity to the polarization of the incident light, and the potential for on-chip photonic and electronic integration make PhCS-FPC a promising candidate for all-optical bistable devices.

At present three main mechanisms of optical propagation with periodically focused modes in the chains of dielectric spherical particles with a refractive index near n = 1.59 are considered in the literature: evanescent whispering gallery mode coupling, photonic nanojet-induced modes, and the propagation of transverse magnetic modes under conditions close to Brewster angle geometry. In this paper we show that quasi-periodical focusing modes exist in a range of near unity refractive indices for chains of dielectric particles in both spherical and cubic forms. We also show that such a medium can be considered a gradient index waveguide with a parabolic law of refractive index variation.

A pure optical microwave oscillator with single mode oscillation is proposed and demonstrated. This system has no any electrical microwave devices as well as electro-optic (E/O) and opto-electronic (O/E) conversion. The oscillation frequency is chosen by Brillouin-selective sideband amplification, and the optical envelope detection and feedback modulation are implemented by a semiconductor optical amplifier (SOA). As a high-Q tunable optical comb filter, an active ring resonance cavity (ARRC) is employed to select one oscillation mode within the Brillouin gain region, and consequently a single mode oscillation signal can be generated. In the experiment, a single mode photonic microwave signal with frequency of 10.83 GHz and side-mode suppression ratio of 48 dB is obtained. The measured phase noise is −88 dBc/Hz@10 kHz. In addition, the tunability is also demonstrated by adjusting the wavelength of the light source.

The flexible photonic generation of millimeter-wave (mm-wave) vector signal adopting frequency multiplication enabled by two paralleled phase modulators and pre-coded radio frequency (RF) signals based on dynamic pre-coding algorithm is proposed and demonstrated. One driving signal has the original phase information and a phase deviation for dispersion compensation while the other signal has an opposite phase information and the same compensation phase. The amplitude depends on that of the regular vector symbol and the ratio of driving voltage to half-wave voltage of the phase modulator (PM). Two RF signals modulate the identical light waves from one laser via phase modulators respectively. The light waves are then transmitted over a fiber link after the selection of proper orders of harmonics by the wavelength selective switch (WSS). At the receiver, the optical signal is applied directly to a photodetector (PD) to generate the mm-wave vector signal at the desired frequency. The simulation of proposed scheme with radio over fiber (RoF) link transmission has been build. The result shows that the error vector magnitude (EVM) of generated 60 GHz, 100 GHz, and 140 GHz 16 quadrature-amplitude-modulation (QAM) signals of 1 Gb/s is no more than 20% after 80 km fiber transmission when the power into PD is no less than −10 dBm under ideal condition.

We propose and theoretically study a silica double-toroid microcavity to confine the whispering-gallery mode (WGM) in an ultra-small space, which consists of two toroid-to-toroid coupled cavities separated by a nanoscale gap region with low refractive index, such as the air gap. Benefitting from the strong field localization of the “slot” effect, power enhancement of symmetric WGMs in the gap results in the ultra-small mode volume of 4. 8 μ m which is quite smaller than the conventional toroidal microcavity with mode volume of about hundreds of cubic micrometers. The confined modes hold the potential advantages over conventional photonic devices, especially in the applications of the sensing and optical trapping. In the application of refractometer, a high refractive index sensitivity of up to 468 nm per refractive index unit (nm/RIU) can be obtained in the 1000 nm wavelength band. In the optical trapping application, the double-toroid microcavity enables a significant field enhancement in the confined WGM, and the gradient force could reach as high as 22 pN/W for a single nanoparticle with the radius of 5 nm. As the potential advantages, this study of silica double-toroid microcavity provides a good reference for realizing the high-efficient photonic applications such as optical sensing and trapping.

In this paper, a single-opening microring resonator (SOMRR) is proposed for simultaneous measurement of refractive index (RI) and pressure. The notch angle lifts the degeneracy of clockwise and counter-clockwise WGMs to excite the mode splitting, forming the symmetric and the asymmetric standing wave modes (SWMs) in the SOMRR. Due to the different electromagnetic field energy distribution of the two SWMs, the symmetric SWM and the asymmetric SWM show different sensitivities toward the change of ambient RI and the pressure exerted on the resonator. Through the three-dimensional FDTD simulations of the two SWMs under different external environments and loads, we obtain a RI sensitivity of 77.07 nm/RIU, a high pressure sensitivity of 5.01 pm/kPa for the symmetric SWM and a RI sensitivity of 69.54 nm/RIU, a high pressure sensitivity of 5.72 pm/kPa for the asymmetric SWM. Moreover, by solving the inverse matrix of the sensitivity matrix, the resonance wavelength shifts respectively caused by the change of RI and pressure can be distinguished. For the biosensing application based on the flexible photonic device, the effect of strain-optical coupling can be eliminated by using this method. It advances the accuracy of detection results and provides a novel route to achieve its application for biosensing in the real world.

In this paper, we present a theoretical analysis of four-wave mixing (FWM) between short optical pulses in a photonic crystal semiconductor optical amplifier (PC-SOA). The proposed model is based on a nonlinear propagation equation by taking into account self-phase modulation (SPM), carrier density pulsations (CDP), carrier heating (CH), and spectral-hole burning (SHB). To analyse the FWM in a PC-SOA, pulse evolution in a temporal and spectral domain are investigated. Also, the optical fluid method is used in the photonic structure for design and engineering an appropriate bandwidth with constant group index to analyse the FWM mechanism. The bandwidth is designed in the L-Band region of telecommunication optical networks. Based on calculated results, it is depicted that for low energy short pulses, the conversion efficiency (CE) of PC-SOA is higher than conventional SOA. Furthermore, it is shown that, by increasing the injection current the CE is increased.

The investigation of propagating electromagnetic waves along the random dielectric multilayers following a white-noise-like pattern is presented. The system constituents are chosen to be SiO2 and TiO 2 in such a way that absence of absorption losses is guaranteed in the electromagnetic region of interest. The results of the calculation show that the reflectance of the noise-like structures depends on both the noise amplitude and the seed of the configurations; the latter being associated to the degree of randomness presented in the heterostructures, which is analyzed via specific statistical tools. Under an adequate design of the random structures it is possible to obtain broad range omnidirectionality, which is noticeably higher than the typical from periodic Bragg mirrors. In addition, selective spatial localization in the central part of the heterostructures is determined for certain propagating modes, with relative confined electric field amplitudes shown to reach up to 1 0 4 in some cases. According to the results of the simulations, this kind of heterostructures could have potential applications in photonics and optoelectronics such as solar concentrators and random lasers.

In this paper, a novel silicon-based integrated structure is proposed for plasmon-induced transparency (PIT) and plasmon-induced absorption (PIA) in the mid-infrared (MIR) band. The device consists of a semiconductor–insulator–semiconductor (SIS) plasmonic bus waveguide coupled to three rectangular nano-cavities. The transmission properties of the structure are numerically simulated by finite-difference time-domain (FDTD) method. The wavelengths of the PIA and PIT peaks can be simply tuned by adjusting the geometrical parameters of the device. It is shown that the proposed structure can be used either as a temperature sensor with the sensitivity of 1.48 nm/ ∘ C or as a plasmonic switch operating in the MIR range with the transmission of 83% and modulation depth (MD) of 20.74 dB. The proposed multifunctional device has potential applications for photonic switching and lab-on-a-chip applications in the MIR band.

By virtue of multiple-beam interference, periodic structures such as photonic or phononic crystals can be used to separate an incident polychromatic light or acoustic beams, respectively, into their constituent frequency components. In addition, it is widely acknowledged that a light beam that is carrying orbital angular momentum (OAM) also has a spatial angular frequency in the azimuthal zone. Here we demonstrate that multiple-beam interference in the azimuthal zone can be used to modulate the transmission of the OAM state and; can thus serve as an OAM filter. The 2 D transmission spectrum is analyzed and the mode resolution is discussed in detail. We anticipate that this OAM filter will be promising for use in applications such as optical switches, mode de-multiplexing in mode-division multiplexing communications and single-photon discrimination when using linear optical elements.

We report a 1 × N hybrid radio frequency (RF) photonic splitter with arbitrary phase shift and amplitude ratio using a dual-polarization dual-parallel Mach Zehnder modulator (DP-DPMZM). The DP-DPMZM is properly set to generate an orthogonally polarized single-sideband (SSB) modulated optical signal. By controlling a polarization controller (PC) and a polarizer (Pol.) that cascaded behind the modulator, an RF photonic splitter with arbitrary phase and amplitude ratio can be realized. Compared with previous reported works, the proposed RF splitter can be operated in a wide bandwidth since no optical or electrical filters are involved. The proposed scheme is theoretically analyzed and experimentally verified.

Design of a pressure sensor workable from megapascal (MPa) to gigapascal (GPa) pressure range is proposed on a two dimensional triangular/hexagonal lattice silicon (Si) photonic crystal (PhC) arrangement. In order to ensure high resolution sensing over this wide pressure range, a hexagonal shaped ring of hexagonal unit cells and two micromachined silicon cantilever tips are considered on the photonic crystal arrangement. The concept of using micromachined cantilever tip in a PhC arrangement for optical sensing of pressure is novel. Moreover, use of hexagonal ring with hexagonal unit cells make the structure more sensitivity than other types of ring arrangement. It is shown that the two silicon cantilever tips can be used to detect applied pressure from 1 MPa to 10 MPa with resolution of 1 MPa and 10 MPa to 100 MPa with a resolution of 10 MPa, respectively. Detection of applied pressure from 20 MPa to 10 GPa with the resolution of 20 MPa can be done using the hexagonal ring of hexagonal unit cells. The entire design is done using the MPB (MIT Photonic Bands) and MEEP (MIT Electromagnetic Equation Propagation) simulators freely available from MIT, USA.

Since next-generation (5G) wireless communication systems require high-speed processing of large amounts of data and wider bandwidth, the millimeter wave (mmWave) band becomes increasingly important and transmission technologies require a large number of antennas. Therefore, it is necessary to study technologies that can implement a very small antenna considering the characteristics of the mmWave band. In this study, we propose a high-performance miniature analog beamformer implementation technique that can operate in the mmWave band. The proposed method uses silicon (Si) photonics technology, which not only can process large amounts of data at the speed of light, but is also compatible with CMOS processes and can be miniaturized due to high refractive index. The SiN-based optical beamforming network (OBFN) chip used in satellite communications has been redesigned into a Si-based OBFN. In particular, we propose four types of Mach–Zehnder modulator (MZM) structures, including the design used in the existing satellite communication OBFN system. The feasibility and performance were tested with commercial optical simulation software to carry out virtual prototyping and create foundry-ready designs. Simulation results confirm that the proposed schemes are efficient at implementing miniature array antennas in the mmWave band and are suitable for high-performance ultra-small analog beamformers and massive multiple-input multiple-output (MIMO) implementations for 5G wireless communication systems.

Graphene as a promising material for terahertz-infrared region plays an important role in nanoplasmonic devices owing to its tunability. We propose a hybrid graphene nanoplasmonic waveguide and analyze its propagation properties by finite element method. The results show that the light in terahertz-infrared region can be confined at low-index material and the fundamental mode can be tuned flexibly by changing Fermi energy level of graphene. Then an application of the designed waveguide, an electrically controllable directional coupler is designed and its performance is numerically verified. This approach can be extended to novel designs of nanoscale integrated photonic devices.

Resonant optical tunneling effect (ROTE) is a special phenomenon that light can fully go through the seemingly impenetrable optical structure. It is a prominent example to study the analogy of wave optics and quantum physics. Previous theoretical work mostly focused on the optical modeling of transmission spectrum using the transfer matrix method (TMM), but put little effort in the quantum model. This paper advances the optical modeling by using the finite-difference time-domain method (FDTD) to simulate the electric field distribution and by using the plane wave expansion (PWE) to predict the optical bandgap. Moreover, we present the first analytical quantum model of the ROTE and further derive a direct expression of the transmission peak positions. This expression cannot be derived by the optical models, but its predicted peak positions match the optical modeling results using the FDTD, the PWE and the TMM. This well demonstrates the merit of the quantum analogy for analyzing the optical systems. This work may inspire the transplantation of the established ideas and designs in the quantum field into the optical field to create new optical and photonic devices.

A method for photonic generation of arbitrary microwave binary digital modulation signal based on polarization switch is proposed and investigated. A polarization modulator is utilized to switch the direction of a linearly-polarized optical signal between two orthogonal axes. Then, a polarization-dependent modulation structure is employed to modulate an external RF signal to the two optical carriers with different polarization directions respectively. The modulation structure consists of a polarization beam splitter, two parallel placed dual-drive Mach–Zehnder modulators and an optical combiner. By adjusting the parameters of the two modulators, different optical sidebands can be obtained in two polarization directions. After optical-to-electrical conversion, a microwave amplitude shift keying (ASK), frequency shift keying (FSK) or phase shift keying (PSK) signal can be achieved. The modulation format, bit-rate and carrier frequency of the generated signal can be tuned independently and flexibly. A simulation is demonstrated to verify the proposed scheme, a 2-Gbit/s 40-GHz ASK signal, a 2-Gbit/s FSK signal with carrier frequencies of 20 and 40 GHz, and a 2-Gbit/s 20-GHz PSK signal are obtained. The scheme has good tunability.

In the process of mode coupling measurement in FMF, the reflection from the front facet of the fiber generates a dead zone, which seriously affects the accuracy of the measurement. This paper analyzed mode coupling over FMF based on Rayleigh backscattering and built an experimental system using two photonic lanterns as the mode converter and demultiplexer respectively. And then we successfully measured the mode coupling distribution along a 4-km six-mode fiber. The values of the mode coupling coefficients obtained with the experimental system agreed well with those obtained with the conventional transmission method, and the deviations were less than 0.66 dB/km while the deviations were more than 1.31 dB/km using other experimental system which cannot eliminate the Fresnel reflection when a 300 ns optical pulse was coupled into the LP01 mode. The experimental system based on two photonic lanterns can eliminate the Fresnel reflection and the associated dead zone from the front facet of the fiber.

In this paper, a chalcogenide-based ridge waveguide with a suspended structure on the substrate of Si 3 N 4 , is designed, which is demonstrated to have low and flat dispersion profiles. Simulation results show that when the higher-order nonlinear effects and linear loss are considered, a broadband supercontinuum with high coherence ranging from 1.0 to 5. 6 μ m is obtained after a 3.1-mm long propagation when pumping wavelength 2. 65 μ m and peak power 450 W. Our proposed scheme provides a promising solution to realize broadband and highly coherent SC in mid-infrared region for nonlinear photonics and spectroscopy.

The generation of tightly focused light beams carrying orbital angular momentum (OAM) offers new opportunities for applications in photonics, optoelectronics and optical communications. These spatially inhomogeneous light fields render possible the coupling of the photon field to the angular momentum characteristics of the sample. In this study we exploit this fact and consider nanostructured quantum rings (QRs) irradiated by OAM beams with the aim of inducing swiftly local magnetic moments as well as harmonic generation. Based on a time-dependent quantum simulation we investigate different laser setups for efficient magnetic moment generation during and after the pulse application. In particular, we study the role of the winding number of the optical vortex in enhancing the magnetic moment at a fixed laser intensity. Further, we analyze the emitted radiation associated with the photoinduced charge oscillations and the non-equilibrium current circulation. Irreversible relaxation processes due to the interaction of charged carriers with acoustic phonons are included using a density matrix formalism.

The discussion of ultrathin crystalline silicon solar cell (UCSC) thickness and light enhancement patterns has long been a practical topic in its field with the objective of achieving optimum efficiency. In this work, we distinguish between the effects of the top and bottom structural designs on the light absorption of ultrathin crystalline-silicon solar cell. Nanopyramid (NP) front surface and distributed Bragg Reflector (DBR) bottom layer as enhancement agent was combined and its relation with thickness of solar cell was studied thoroughly. The relationship of photonic interaction between the top and bottom surfaces is also examined. Based on our simulation results, the optimized cell architecture consists of a 4 μ m-thick film combined with nanopyramid of 800 nm period and bottom reflector of 4 pair DBRs. The maximum achievable photo-current density of 36.72 mA/cm2 was obtained, which is among the best results of prior research for UCSC.

A novel photonic scheme of microwave waveforms generator based on a dual-loop optoelectronic oscillator (OEO) is experimentally verified. A 10-GHz microwave signal generated by OEO is modulated onto the directly modulated laser (DML) and the phase modulator (PM) simultaneously. By adjusting the driven power of the DML and the PM and the phase difference between the pulse signal inputted into the PM and the PM’s driven signal, the desired optical spectrum is obtained. By passing appropriate dispersion, the optical spectrum can be converted into desired waveform. In this experiment, a series of waveforms with the shapes of sawtooth/reversed-sawtooth, triangle, and pulse are generated.

Photonic spin Hall effect (SHE) manifests itself as spin-dependent shift or splitting of a light beam, which is derived from spin–orbit interactions, and can be realized by breaking the rotation symmetry of light–matter interaction systems. Here, we demonstrate the observation of a photonic SHE by breaking the rotation symmetry of the optical field, while keeping the rotation symmetry of the inhomogeneous waveplate. The inhomogeneous waveplate constructed by dielectric nanostructures, introduces a spin-dependent Pancharatnam–Berry phase to the two spin components of the input beam, i.e., the left- and right-circular polarization components acquire exactly opposite vortex phases. During beam propagation, they experience opposite azimuthal rotations, and induce a four-lobe spin-dependent splitting in the azimuthal direction. In addition, the spin-dependent splitting becomes more evident upon beam propagation, and can be enhanced by increasing the topological orders of the nanostructures. For comparison, we also examine that no spin-dependent splitting can be observed when keeping the rotation symmetry of the incident optical field.