Modulation Devices Research Articles

Robust polarization state generation for long-range quantum key distribution.

We present a new compact and robust polarization state transmitter designed to execute the BB84 quantum key distribution protocol. Our transmitter prepares polarization states using a single commercial-off-the-shelf phase modulator. Our scheme does not require global biasing to compensate thermal and mechanical drifts, as both of the system's two time-demultiplexed polarization modes share a single optical path. Furthermore, the transmitter's optical path entails a double-pass through the phase modulation device for each polarization mode, allowing multiple phase rotations to be impinged on each light pulse. We present a proof-of-concept prototype of this transmitter topology and demonstrate a mean intrinsic quantum bit error rate below 0.2% over a 5 hour measurement.

Graphitic carbon nitride modulated short pulse generation in an Erbium-doped fiber laser

In the present study, a few layered graphitic carbon nitrides (g-C3N4) nano-sheets were successfully manufactured by the calcination method. It demonstrates nonlinear optical (NLO) property with modulation depths of ∼4.26% at 1.5 μ m. The index-matching gel adhesion effect was used to place the g-C3N4 nano-sheets on the fiber ferrule surface to produce short-pulsed lasers. The g-C3N4 saturable absorber (SA) based Q-switched erbium-doped fiber laser (EDFL) emits at 1560.5 nm wavelength with 1.2 nm of spectral bandwidth at 3 dB. The radio frequency's signal-to-noise ratio (SNR) is 42 dB at first harmonic, demonstrating excellent pulse stability. As the pump power increases, the frequency increases from 27.2 to 108 kHz, and the pulse shortens from 14.6 to 4.2 μ s, correspondingly. The highest pulse energy, peak power, and average output power are measured to be 48.7 nJ, 11 mW, and 5.18 mW at the highest pump power of 479.1 mW. Besides, the morphology and structure of g-C3N4 were characterized by scanning electron microscopy (SEM) and X-rays powder diffraction (XRD), photoluminescence (PL) spectra, Raman spectroscopy, Fourier transform infrared spectra (FT-IR), and UV- diffuse reflectance spectroscopy (DRS) have been also presented. Additionally, the stability of g–C3N4–SA was also measured. These findings suggest that few layered g-C3N4 nano-sheets have a substantial role as a SA in optical modulation devices and nonlinear optical properties at the near and mid-infrared band.

P‐12.12: Development and Application of High Birefringence Liquid Crystal Materials

The development of new liquid crystal optoelectronic devices, including laser phase modulation, microwave and terahertz devices, requires liquid crystal materials with high birefringence. In this paper, three new molecular design strategies are proposed, including the introduction of olefin chain, lateral fluorine substitution and new ring core. Four new series of isothiocyanate liquid crystal compounds with high birefringence, low melting point and wide nematic temperature range were synthesized. Based on these new liquid crystal compounds, a liquid crystal mixture with nematic temperature range of ‐40~146 ºC and birefringence of 0.42 was developed. At 19 GHz, the new liquid crystal mixture shows excellent dielectric properties, with dielectric anisotropy of 1.28 and dielectric loss of 0.0087. The new liquid crystal mixture also has very low viscoelastic coefficient. The results at 1550nm and 60 ºC show that the response speed can reach 3.6 milliseconds with 2π phase modulation in the reflection mode.

Case report of optimizer implantation to modulate cardiac contractility in patients with chronic heart failure and atrial fibrillation

A cardiac contractility modulation device is a new treatment used in patients with heart failure. CCM therapy is associated with an increase in physical activity tolerance, improved quality of life, reduced hospitalizations due to heart failure, and reverse remodeling of the left ventricle in patients with systolic heart failure. In this case, the clinical benefit of cardiac contractility modulation in a patient with chronic heart failure, atrial fibrillation and postinfarction left ventricle aneurysm was reported. Development of postinfarction left ventricle aneurysm in patients with reduced ejection fraction is associated with a high risk of surgical complications. However, an adequate assessment of the functional reserve of the left ventricle myocardium and the choice of surgical correction method allows for receiving favorable outcomes of surgery. We present a case of a successful combination of interventional and surgical treatment of a patient with heart failure and post-infarction left ventricular aneurysm.

Low sampling high quality image reconstruction and segmentation based on array network ghost imaging.

High-quality imaging under low sampling time is an important step in the practical application of computational ghost imaging (CGI). At present, the combination of CGI and deep learning has achieved ideal results. However, as far as we know, most researchers focus on one single pixel CGI based on deep learning, and the combination of array detection CGI and deep learning with higher imaging performance has not been mentioned. In this work, we propose a novel multi-task CGI detection method based on deep learning and array detector, which can directly extract target features from one-dimensional bucket detection signals at low sampling times, especially output high-quality reconstruction and image-free segmentation results at the same time. And this method can realize fast light field modulation of modulation devices such as digital micromirror device to improve the imaging efficiency by binarizing the trained floating-point spatial light field and fine-tuning the network. Meanwhile, the problem of partial information loss in the reconstructed image due to the detection unit gap in the array detector has also been solved. Simulation and experimental results show that our method can simultaneously obtain high-quality reconstructed and segmented images at sampling rate of 0.78 %. Even when the signal-to-noise ratio of the bucket signal is 15 dB, the details of the output image are still clear. This method helps to improve the applicability of CGI and can be applied to resource-constrained multi-task detection scenarios such as real-time detection, semantic segmentation, and object recognition.

Energy storage modular multilevel converter topology and its fault ride through control strategy

Energy storage modular multilevel converter (ES-MMC) can suppress the offshore wind power fluctuation and provide frequency support for the power grid. Voltage drop of power grid will lead to limited power transmission, and dissipation device should be installed to meet the requirements for fault ride through. The half bridge submodule, energy storage module and dissipation device are designed in an integrated way in this paper to reduce the system investment cost effectively. The corresponding fault control strategy is proposed to match the asymmetric topology. In addition, the cooperative control strategy of wind farm and the ES-MMC is adopted to further reduce the energy consumption of the power transmission during the fault ride through period. In order to prove and analyze the proposed topology and its fault ride through control strategy, a simulation model of 600MW offshore wind power transmission system is built. The results show that the proposed topology has good economic advantages, and its control strategy are effective and correct.

High responsivity evanescently coupled waveguide photodiode using spot-size converter and distributed Bragg reflector at 1.55 μm wavelength

InGaAs/InP waveguide photodiode, one of the most crucial devices in optical modules, has proven to be beneficial for exponential data communication. However, improving responsivity with a high 3 dB bandwidth remains a challenge for various photodetector designs. In this letter, a multi-layers SiO2/SiNx distributed Bragg reflector and a spot-size converter are both employed and improve responsivity by 61%. An optimized optical matching layer and a spot-size converter combined with the reflector lead to a 0.66 A/W responsivity at 1550 nm wavelength. 3 dB bandwidth of the device can achieve 85 GHz with a 3μm × 10 μm active area. The responsivity improvement indicates a higher quantum efficiency and signal-to-noise ratio. It could be beneficial for high speed optical communication and other applications.

Scalability of Large-Scale Photonic Integrated Circuits

To keep up with the growing bandwidth demands, photonic integrated circuits (PICs) have been widely employed in various application scenarios where high capacity and high-bandwidth-density interconnects are required. However, it is challenging to scale the PICs toward future petabit per second capacity requirements. We study the scalability bottlenecks of PICs in terms of guiding materials, dense integration approaches, wide-band optical sources, and high-efficiency tunable and modulation devices. We also look for possible solutions to address these challenges. In the end, we provide a perspective on future PIC development. Moore’s law for integrated photonics may last for a much shorter time than that in the microelectronics industry, requiring significant innovations and technological breakthroughs in PIC research.

All-polymer solid state electrochromic device for low voltage and fast modulation between primary colors

The fabrication of promising devices requires involvement from multiple dimensions. With the ability to display three primary colors from a single device, electrochromic devices become more valuable for smart displays. One such attempt has been reported here by demonstrating Red-Green-Blue color modulation from a solid state device fabricated by combining two different conducting polymers, polyaniline (PANI) and polythiophene (P3HT), where they mutually support each other. Electrochromic properties are demonstrated on both electrodes, which can be achieved by selecting an appropriate bias for displaying the three primary colors in a single system. In addition, the device delivers faster switching (500 ms) and better coloration efficiency up to 540 cm2/C, thanks to the complementary redox activity of the PANI and P3HT electrodes.

Ultrafast strong-field terahertz nonlinear nanometasurfaces

Abstract Strong-field terahertz (THz)–matter interaction permits the investigation of nonequilibrium behaviors in the nonperturbative zone. However, the unavailability of a high-field free-space THz source with high repetition rates, excellent beam quality, and high stability hinders its development. In this work, we obtain the nonlinear modulation dynamics of a “THz-nano” metasurface on silicon substrates using a time-resolved strong-field THz-pump THz-probe (TPTP) with a thousand orders local field enhancement through confining THz waves into nano-gaps (15 nm, λ/33,000). By switching the THz field strength, we successfully realize a self-modulation ∼50 GHz frequency shift, which is further verified via the TPTP ultrafast time-resolution technique. The phenomenon is attributed to the impact ionization (IMI) of the silicon substrate under the excitation of extremely confined strong THz fields in nano-gaps. Both strong-field induced intervalley scattering (IVS) and IMI effects of photodoped silicon occurring in nano-gaps and large-area substrates were also observed by 800 nm optical injection of carriers. These aforementioned findings provide a robust research platform for the realization of ultrafast time resolution nanoscale strong-field THz–matter interaction and new ideas for nonextreme laboratories to realize extreme THz science, applications, and THz nonlinear modulation device development.

An integrated device for electro-optic modulation and dense wavelength division multiplexing based on photonic crystals

We proposed an integrated device for electro-optic (EO) modulation and dense wavelength division multiplexing (DWDM) based on photonic crystals (PhCs). The transmittance performance of the designed structure was modelled and analyzed according to the time-domain coupled mode theory (CMT), using three-dimensional finite-difference time-domain (3D-FDTD) method to calculate the parameters of the proposed device for verification. The numerical results show that the proposed integrated device can realize the functions of “on”, “off” modulation and DWDM with a channel spacing of 0.8 nm at the operating wavelengths of 1555 nm and 1554.2 nm. The minimum insertion loss, channel crosstalk and modulation voltage are 0.7 dB, − 29.04 dB and 0.88 V, respectively. The maximum extinction ratio and modulation speed are 21.51 dB and 29.4 GHz. The designed integrated device has the advantages of low loss, compact size (41.28μm×11.18μm), narrow channel spacing, large extinction ratio, which can be easily expanded the number of channels and used in highly integrated large-capacity optical communication systems and data center.

Broadband Enhancement of Optical Nonlinearity in a Plasmonic Nanocavity Coupled with an Epsilon-Near-Zero Film

Nonlinear optics plays a crucial role in various fields, including microscope, all-optical data processing, and quantum information. However, nonlinear optical responses in natural materials are generally very weak, and therefore it is extremely difficult to design all-optical active devices at the subwavelength scale. Here, a dielectric-metal hybrid system is proposed to acquire optical nonlinearity enhancement through the strong coupling between the epsilon-near-zero mode in an indium tin oxide (ITO) nanofilm and the localized surface plasmon in a nanocavity. Such a coupled system exhibits a nonlinear refractive index n2 up to 10.31 cm2/GW and an absorption coefficient β up to 1.0 × 106 cm/GW, over three orders and two orders of magnitude larger than those of bare ITO, respectively. In addition, enhanced nonlinear responses can be observed in a wide wavelength range (∼1400 nm bandwidth) in the near infrared region. Our results provide an efficient way for the development of low-power all-optical modulation devices.

Multifunctional and tunable ultra-broadband linear to circle polarization converter based on VO2-integrated material

Considering that the metastructures (MSs) previously proposed usually perform in a single state, herein, a multifunctional and tunable ultra-broadband linear to circle (LTC) polarization converter based on phase transition material vanadium dioxide ( V O 2 ) is proposed in the terahertz (THz) region. By manipulating the temperature, the function of the LTC polarization conversion (PC) can be conveniently switched between transmission and reflection states. When the environment temperature is low, V O 2 presents the insulating state, and the MS can achieve ultra-wideband LTC PC from 0.57–0.83 THz with a relative bandwidth (RB) of 37.3%. When the temperature exceeds 68°C, LTC PC with the frequency bandwidth of 0.83–1.20 THz and 0.83–1.17 THz can be obtained in a reflection state when electromagnetic waves propagate forward and backward, whose RBs are 36.4% and 34.0%, respectively. Meanwhile, a broadband linear to linear (LTL) PC can also be realized in the range of 1.19–1.41 THz for the forward incident wave and 1.16–1.37 THz for the backward incident wave. The designed MS offers an effective method to realize four different functions and has tremendous potential value in realizing THz modulation devices, electromagnetic cloaking, and communication systems.

Multifunctional terahertz absorber based on the Dirac semimetal and vanadium dioxide.

In this paper, a multifunctional terahertz (THz) absorber based on Dirac semimetal and vanadium dioxide (V O 2) is proposed. By modulating the temperature of V O 2, the absorber can be switched between the narrow band and wide band. When V O 2 is in the metallic state, the absorber has a broadband absorption effect with a bandwidth of approximately 4THz. It has the advantages of insensitivity to polarization and wide-angle absorption. When V O 2 is in the insulating state, the absorber has two absorption peaks with absorptivity exceeding 90% and sensitivities of 297.7 and 402GHz/RIU, and thus can be used as a highly sensitive sensor for cell detection. When the Fermi level of the Dirac semimetal is changed, the absorption characteristics can be modulated. The absorber has broad application prospects in multifunctional modulated devices.

Upscaling of Carbon-Based Perovskite Solar Module.

Perovskite solar cells (PSCs) and modules are driving the energy revolution in the coming photovoltaic field. In the last 10 years, PSCs reached efficiency close to the silicon photovoltaic technology by adopting low-cost solution processes. Despite this, the noble metal (such as gold and silver) used in PSCs as a counter electrode made these devices costly in terms of energy, CO2 footprint, and materials. Carbon-based perovskite solar cells (C-PSCs) and modules use graphite/carbon-black-based material as the counter electrode. The formulation of low-cost carbon-based inks and pastes makes them suitable for large area coating techniques and hence a solid technology for imminent industrialization. Here, we want to present the upscaling routes of carbon-counter-electrode-based module devices in terms of materials formulation, architectures, and manufacturing processes in order to give a clear vision of the scaling route and encourage the research in this green and sustainable direction.

Active terahertz beam deflection based on a phase gradient metasurface with liquid crystal-enhanced cavity mode conversion.

Active manipulation of terahertz (THz) beam deflection and intensity is highly desired for possible applications in wireless communication, radar, and remote sensing. Here, by integrating the phase-gradient metasurfaces and tunable liquid crystal materials, we demonstrate an active THz beam deflection device based on polarization mode conversion. The resonant modes in the photonic cavity formed by the double-layer metasurface and the tunable anisotropic liquid crystal material in the cavity not only improve the polarization conversion efficiency of the device, but also actively regulate the resonance matching conditions. As a consequence, a beam deflection of 47.5° with 50% diffraction intensity at 0.69 THz is achieved in the x-to-y polarization conversion mode, and this beam can be actively modulated with an ultrahigh modulation depth of 99.6% by rotating the anisotropic optical axis of liquid crystals. Moreover, the proposed device can also work as the deflection of 32.5° in the y-to-x polarization conversion mode at 0.94 THz with a maximum diffraction intensity of 38% and an intensity modulation depth of 97.8%. This work provides a new approach based on liquid crystal photonic devices for wavefront manipulation and active modulation for THz waves.

Non-mechanical self-alignment system for free-space optical communications based on a cascaded liquid crystal optical antenna.

Free-space optical (FSO) communication has attracted extensive attention in recent years. To maintain a reliable FSO link, two main issues need to be addressed: beam drift and vibration. In this paper, we demonstrate a non-mechanical self-alignment system based on a cascaded liquid crystal optical antenna, in which a frequency decoupled hybrid integration Kalman filter (FDHI-KF) method is proposed to achieve predictive beam drift tracking and vibration mitigation. By leveraging the integrated control on our lab-made liquid crystal phase modulation devices, and implementing the adaptive algorithm on a heterogeneous field programmable gate array (FPGA), this system is capable of realizing precise self-alignment without any moving parts. Experiments are conducted to verify its performance in practical applications. We envision it to set a benchmark for future liquid crystal non-mechanical beam-steering systems in FSO communications.

Preparation and optoelectronic characteristics of perovskite module devices in air assisted by polymer inner packaging layern

The preparation of traditional organic-inorganic lead-halogen hybrid perovskite solar cells often requires strict nitrogen glove box conditions, thus hindering their industrial scalability. This study develops a large-area perovskite film formation process and designs a novel device structure to achieve a dual enhancement of module device efficiency and stability in a high humidity air environment (55%). High-quality perovskite thin films are successfully prepared by vacuum extraction in ambient air, followed by a double-end low-temperature photopolymerization process utilizing acrylate monomer molecules for inner encapsulation modification of the freshly formed perovskite thin films. The influences of these techniques on the photoelectric characteristics of perovskite thin films and devices are investigated. The results indicate that uniform and dense perovskite films can be achieved in ambient air with a pumping time of 60 s. By adjusting the concentration of ethylene glycol dimethacrylate monomer molecules used in the low-temperature photopolymerization process, the surface defects on the perovskite film can be effectively controlled. The optimal concentration of 1 mg/mL results in perovskite film with optimal morphology and fluorescence intensity. Furthermore, rigid module device and flexible module device (effective area: 18 cm²), based on the polymer inner encapsulation, demonstrate outstanding outdoor photoelectric conversion efficiencies of 19.51% and 18.17%, respectively (with the highest indoor low-light conversion efficiencies of 34.5% and 30.2%, respectively). Notably, the untreated flexible device exhibits a significant decline in photoelectric conversion efficiency, falling below 50% of the initial value after one month of exposure to air. In contrast, device incorporating the polymer inner encapsulation layer maintains over 90% of their original efficiency, highlighting their excellent humidity resistance stability. Moreover, the polymer encapsulation layer also greatly improves the bending stability of the flexible device. This research paves the way for industrial-scale producing perovskite solar cells and addressing the challenges associated with humidity and large-area fabrication. The findings contribute to advancing perovskite solar cell technology and offering a pathway for high-efficiency and stable devices suitable for practical applications.

Three-channel Integrated Device for Graphene Electro-optic Modulation and Mode Division Multiplexing

Three-channel Integrated Device for Graphene Electro-optic Modulation and Mode Division Multiplexing

Sensor/actuator colocation feasibility for distributed damping control using active power modulation

Multi-use distributed active power modulation devices, including energy storage, have the potential to transform the dynamic performance and resilience of modern power systems. Rapid response characteristics relative to traditional power delivery equipment paired with traditional uses (arbitrage, reserve, etc.) make storage an obvious choice for multi-use operation, adding value for asset owners while augmenting stability for reliable operation. Limitations to distributed power control are investigated to provide guidance for those interested in separated sensors and actuators. Substantive distance between the sensor/actuator pair results in non-minimum phase (NMP) which complicates the control design, reducing feedback system effectiveness. It is shown that wide-area control (WAC) is limited by the presence of NMP induced by closed right-half plane (CRHP) zeros - a consequence of sensors placed at locations separated from modulation bus(es). Such geographic separation may be driven by economics, asset owner jurisdiction, technology and/or policy, and is therefore unavoidable. This work suggests that system designers must perform a collocation study before control design and testing. A well-known WAC architecture using synchrophasors as sensors and energy storage devices for active power injection is presented as a detailed case study. • Collocated sensor–actuators pose difficulties which may force modest separation. • Closed right-half plane (CRHP) zeros may result due to such separation. • Noncollocated sensor–actuator pairs may reduce performance and threaten stability. • Bandwidth and performance limitations regarding collocation are determined.