Electro-optical Conversion Research Articles

All-Optical Entanglement Swapping.

Entanglement swapping, which is a core component of quantum network and an important platform for testing the foundation of quantum mechanics, can enable the entangling of two independent particles without direct interaction both in discrete variable and continuous variable systems. Conventionally, the realization of entanglement swapping relies on the Bell-state measurement. In particular, for entanglement swapping in continuous variable regime, such Bell-state measurement involves the optic-electro and electro-optic conversion, which limits the applications of the entanglement swapping for constructing broadband quantum network. In this Letter, we propose and demonstrate a measurement-free all-optical entanglement swapping. In our scheme, a high-gain parametric amplifier based on the four-wave mixing process is exploited to realize the function of Bell-state measurement without detection, which avoids the introduction of the optic-electro and electro-optic conversion. Our results provide an all-optical paradigm for implementing entanglement swapping and pave the way to construct a measurement-free all-optical broadband quantum network.

A High Precision and Multifunctional Electro-Optical Conversion Efficiency Measurement System for Metamaterial-Based Thermal Emitters.

In this study, a multifunctional high-vacuum system was established to measure the electro-optical conversion efficiency of metamaterial-based thermal emitters with built-in heaters. The system is composed of an environmental control module, an electro-optical conversion measurement module, and a system control module. The system can provide air, argon, high vacuum, and other conventional testing environments, combined with humidity control. The test chamber and sample holder are carefully designed to minimize heat transfer through thermal conduction and convection. The optical power measurements are realized using the combination of a water-cooled KBr flange, an integrating sphere, and thermopile detectors. This structure is very stable and can detect light emission at the μW level. The system can synchronously detect the heating voltage, heating current, optical power, sample temperatures (both top and bottom), ambient pressure, humidity, and other environmental parameters. The comprehensive parameter detection capability enables the system to monitor subtle sample changes and perform failure mechanism analysis with the aid of offline material analysis using scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction. Furthermore, the system can be used for fatigue and high-low temperature impact tests.

Editorial: Physical Model and Applications of High-Efficiency Electro-Optical Conversion Devices

Editorial: Physical Model and Applications of High-Efficiency Electro-Optical Conversion Devices

Functional flexible photonics-assisted frequency measurement based on combination of stimulated Brillouin scattering and a Mach – Zehnder interferometer

A functional flexible photonics-assisted frequency measurement (PFM) is proposed. Owing to polarisation multiplexing, the electro-optic (O/E) conversion can be performed in a single optical path, which endows the system high stability and concise configuration. Moreover, using a specially designed functional coarse/accurate frequency measurement (C/AFM) module, a large covering range, moderate accuracy, and fast response frequency measurement results can be ensured in a radar warning receiver (RWR), whereas high accurate results can be used in an electronic countermeasures receiver (ECMR). The simulation results show that a strict monotonous amplitude comparison function (ACF) can be constructed based on the structure of a Mach – Zehnder interferometer (MZI) to map the signal frequency, with a measurement error of less than 0.2 GHz in the range of 1 – 31 GHz. This coarse measurement results can be used to perform radar warning. Based on this result, a highly accurate frequency measurement result is achieved through stimulated Brillouin scattering (SBS). The results reveal that the accuracy is improved to better than 20 MHz. Noteworthy, the C/AFM module consists of purely passive devices, which makes this system meet the potential of integration.

Improved electro-optical and photoelectric performance of GaN-based micro-LEDs with an atomic layer deposited AlN passivation layer.

The quantum efficiency of GaN-based micro-light-emitting diodes (micro-LEDs) is of great significance for their luminescence and detection applications. Optimized passivation process can alleviate the trapping of carriers by sidewall defects, such as dangling bonds, and is regarded as an effective way to improve the quantum efficiency of micro-LEDs. In this work, an AlN passivation layer was prepared by atomic layer deposition to improve the electro-optical and photoelectric conversion efficiency in GaN-based micro-LEDs. Compared to conventional Al2O3 passivation, the AlN passivation process has a stronger ability to eliminate the sidewall defects of micro-LEDs due to the homogeneous passivation interface. Our experiments show that the AlN-passivated device exhibits two orders of magnitude lower forward leakage and a smaller ideality factor, which leads to significantly enhanced external quantum efficiency (EQE). For 25*25 μm2 micro-LEDs, the EQE of the AlN-passivated device was 18.3% and 57.7% higher than that of the Al2O3-passivated device in luminescence application and detection application, respectively.

Investigation on reduction of dross height by analyzing beam intensity distribution in fiber laser cutting

Nowadays, fiber lasers have become a main energy source in laser cutting because of their highly electro-optical conversion efficiency and high beam quality. However, the amount of dross produced by fiber laser cutting is larger than that by CO2 laser cutting, and postprocessing is required to obtain a flat surface without dross, which leads to increasing the processing cost. If fiber laser achieves dross-free cutting of a steel plate, further expansion of cutting applications can be expected. Therefore, in order to achieve further reduction of dross, the influence of beam intensity distribution on dross height was investigated by fiber laser cutting experiments and ray tracing analysis. The laser cutting experiment of steel plate cold commercial with 3.2 mm thickness was carried out by a 3 kW fiber laser with nitrogen assist gas, and a round Gaussian mode of 114 μm spot diameter and a square top-hat mode of 132 μm were used. The square top-hat mode can achieve smaller dross height below 12 μm, which is approximately half of the round Gaussian mode. Ray tracing analysis revealed that the square top-hat mode increased the uniformity of absorbed energy on the cutting front surface, and the more uniform intensity distribution contributed to a small ellipticity of the cutting front shape of the kerf. It was clarified that the shape of the cutting front with a small ellipticity reduced the amount of molten metal ejected from the side of the kerf, which resulted in the reduction of dross height by the fiber laser cutting.

Improvement of the High-Performance Al-Doped LiNi1/3Co1/3Mn1/3O2 Cathode Material for New Electro-Optical Conversion Devices

The ternary cathode material LiNi1/3Co1/3Mn1/3O2 has been extensively focused on as the power sources for new electro-optical conversion devices and lithium-ion batteries. To improve the electrochemical performance, Al doping is one of the effective strategies. Based on the density functional theory of first-principles, the band gap, volume, partial density of states, lithiation formation energy, electron density difference, and electrons’ potential energy of Li1.0-xAlxNi1/3Co1/3Mn1/3O2 were simulated and analyzed with Materials Studio, Nanodcal and Matlab. Results show that Li0.9Al0.1Ni1/3Co1/3Mn1/3O2 has a better conductivity and cycling capability. The potential energy maps of Li1.0-xAlxNi1/3Co1/3Mn1/3O2 simulated in Matlab indicate that the rate capability of LiNi1/3Co1/3Mn1/3O2 is promoted after Al doping. Our theoretical advice could be an important choice for the power application of new optoelectronic devices. In addition, our methods could provide some theoretical guidance for the subsequent electrochemical performance investigations on doping of optoelectronic devices or lithium-ion battery materials.

Bidirectional interconversion of microwave and light with thin-film lithium niobate

Superconducting cavity electro-optics presents a promising route to coherently convert microwave and optical photons and distribute quantum entanglement between superconducting circuits over long-distance. Strong Pockels nonlinearity and high-performance optical cavity are the prerequisites for high conversion efficiency. Thin-film lithium niobate (TFLN) offers these desired characteristics. Despite significant recent progresses, only unidirectional conversion with efficiencies on the order of 10−5 has been realized. In this article, we demonstrate the bidirectional electro-optic conversion in TFLN-superconductor hybrid system, with conversion efficiency improved by more than three orders of magnitude. Our air-clad device architecture boosts the sustainable intracavity pump power at cryogenic temperatures by suppressing the prominent photorefractive effect that limits cryogenic performance of TFLN, and reaches an efficiency of 1.02% (internal efficiency of 15.2%). This work firmly establishes the TFLN-superconductor hybrid EO system as a highly competitive transduction platform for future quantum network applications.

1.5-W 520 nm continuous-wave output from a 50 μm/0.22NA fiber-coupled laser diode module

In this paper, a high brightness fiber-coupled module with a central wavelength of 520 nm is simulated and designed by ray-tracing software ZEMAX and then is experimentally implemented. Three 1-W continuous-wave green LD single emitters based on TO-9-package are successively collimated, spatially combined, and focused into an optical fiber with a core diameter of 50 μm and a numerical aperture of 0.22. The final output power of 1.53 W is obtained, corresponding to an optical–optical conversion efficiency of 51% and an electro-optical conversion efficiency of 10%. The tolerances between the simulation and the experimental result are analyzed and explained.

The Development of Color Display Technology

Light-emitting devices play a vital role in people’s lives, and their extremely wide application has won the attention and research of many scientists for a long time. Light emitting diode based on semiconductor energy band and electro-optical conversion is the mainstream light-emitting devices. Furthermore, control the light by nano optical technology such as plasmon effect and the quantum dot is also attractive. This article reviews the latest research progress of the above three light-emitting devices and their principles and characteristics. Finally, we briefly summarized the advantages and disadvantages of these devices, as well as the possible development directions and potential applications of the next generation light-emitting devices.

Optically addressed spatial light modulator based on nonlinear metasurface

Spatial light modulators (SLMs) are devices for modulating amplitude, phase, or polarization of light beams on demand. Such devices are regarded as the backbone for optical information parallel processing and future optical computers. Currently, SLMs are mainly operated in an electrical addressing manner, wherein the optical beams are modulated by electrical signals. However, future all-optical information processing systems prefer to control light directly by light (i.e., optically addressed, OA) without electro-optical conversion. Here, we present an OASLM based on a metasurface (MS-OASLM), whose operation principle relies on nonlinear polarization control of read light by another write light at the nanoscale. Its resolution is more than 10 times higher than a typical commercial SLM and achieves 500 line pairs per millimeter (corresponding to a pixel size of only 1 μm). The MS-OASLM shows unprecedented compactness and is only 400 nm in thickness. Such MS-OASLMs could provide opportunities to develop next generation all-optical information processing and high resolution display technologies.

Multi-optical parametric oscillator based on electro-optical polarization mode conversion at 3.3 μm and 3.84 μm

The multi-optical parametric oscillator (MOPO) based on electro-optical polarization mode conversion is reported in this paper, which get two idle lights at 3.3 μm and 3.84 μm simultaneously. In the optical parametric cavity, two electro-optical polarization mode converters are placed to rotate the parametric light polarization. When the electric field intensity of electro-optical polarization mode converters are 11.5 V/mm and 34.9 V/mm respectively, the maximum output power of 3.3 μm and 3.84 μm are 2.03 W and 2.25 W, the conversion efficiency to 1064 nm is 8.3% and 9.2%, and the power ratio of 3.3 μm to 3.84 μm is 0.90. The experimental results confirm that the electro-optical polarization mode converters can regulate the conversion of MOPO, resulting in the suppression of back conversion, and the adjustment of parametric light gain.

Effect of ambient temperature and heating time on high-power LED

LED is widely used in various fields as a new style of light sources. Today the efficiency of LED electro-optical conversion is only 20%, and the rest of energy release in the form of heat, which is generating higher junction temperature. The junction temperature rise will cause serious thermal problems and affect the performance of the LED. In this paper, we mainly focus on the research of the thermal problem of the high-power LED. The result shows that the junction temperature and thermal resistance of the R and G-based LEDs increase with the increase of the ambient temperature and the heating time. This leads to an increase in operating current, ambient temperature, and usage time during operation of the high-power LED, which causes the low luminous efficiency of the LED, thereby increasing the amount of heat generated, which easily causes aging of the device and permanent light decay. Therefore, reducing the thermal resistance and junction temperature in the previous LED design will greatly help the thermal and optical improvement of the LED.

A review on the electroluminescence properties of quantum-dot light-emitting diodes

Abstract Quantum-dot light-emitting diodes (QLEDs) are unarguably the most successful member of rapidly developing family of devices based on quantum dots (type II−VI group compounds). Herein, the electroluminescence properties and fabrication/characterization technologies of QLEDs are reviewed. Particular emphasis is devoted to the dynamic processes of charge carriers and the related characterization technology because QLEDs are electro-optic conversion devices whose performance is to a great extent determined by the carrier transport/distribution and exciton formation. The utility of spectroscopic technologies, including steady/transient electroluminescence and photoluminescence, electro-absorption spectrum, and differential absorption spectrum are explained. Additionally, displacement current measurement technology is also discussed due to its potential to characterize the trapped charges within the devices. The strategies to improve the device performance by interface modification and QD design are summarized and the corresponding physics and chemistry mechanisms are discussed. Finally, a summary and outlook are shown about the challenge faced by QLED, as well as possible pathway to enhancing the device performance.

Efficient all-optical modulator based on a periodic dielectric atomic lattice.

All-optical devices used to process optical signals without electro-optical conversion plays a vital role in the next generation of optical information processing systems. We demonstrate an efficient all-optical modulator that utilizes a periodic dielectric atomic lattice produced in a gas of 85Rb vapor. Four orders of diffraction patterns are observed when a probe laser is passed through the lattice. The frequency shift of the peak of each diffraction order can be tuned by adjusting the control laser power and two-photon detuning, enabling this device to be used as a multi-channel all-optical modulator. Both theoretical simulations and experimental results demonstrate that this modulator can operate over a frequency band extending from about 0 to 60 MHz. This work may pave the way for studying quantum information processing and quantum networking proposed in atomic ensembles.

Integrated and spectrally selective thermal emitters enabled by layered metamaterials

Abstract Nanophotonic engineering of light–matter interaction at subwavelength scale allows thermal radiation that is fundamentally different from that of traditional thermal emitters and provides exciting opportunities for various thermal-photonic applications. We propose a new kind of integrated and electrically controlled thermal emitter that exploits layered metamaterials with lithography-free and dielectric/metallic nanolayers. We demonstrate both theoretically and experimentally that the proposed concept can create a strong photonic bandgap in the visible regime and allow small impedance mismatch at the infrared wavelengths, which gives rise to optical features of significantly enhanced emissivity at the broad infrared wavelengths of 1.4–14 μm as well as effectively suppressed emissivity in the visible region. The electrically driven metamaterial devices are optically and thermally stable at temperatures up to ∼800 K with electro-optical conversion efficiency reaching ∼30%. We believe that the proposed high-efficiency thermal emitters will pave the way toward integrated infrared light source platforms for various thermal-photonic applications and particularly provide a novel alternative for cost-effective, compact, low glare, and energy-efficient infrared heating.

Analysis and Experiment of the Laser Wireless Energy Transmission Efficiency Based on the Receiver of Powersphere

Long-distance wireless energy transmission is realized by photoelectric conversion through lasers and photovoltaic cells. However, existing devices have low transmission power and low transmission efficiency. Exploring the main factors that limit the transmission efficiency during transmission is necessary to improve the transmission power and efficiency, and theoretically analyze these factors that affect transmission efficiency, such as beam quality, divergence angle, wavelength and so on. This will provide research directions for subsequent work. A multiwavelength laser wireless energy transmission experimental platform was built by using powersphere, laser with three different wavelengths and other devices. This platform was used for transmission efficiency verification experiment. The total electro-optical-electric conversion efficiency values obtained by the 532, 1030, and 808 nm lasers are 0.01%, 0.08%, and 0.11%, respectively. The corresponding laser-to-electric conversion efficiency values are 1.37%, 1.60%, and 0.73%, respectively. Experimental results show that the electro-optic conversion efficiency of the laser and the photoelectric conversion efficiency of the photovoltaic receiver is the main reasons for the low conversion efficiency of the system. In addition, factors such as the expansion ratio of the beam expander, laser collimation, laser uniformity at the photovoltaic receiver end, and circuit structure, affect the conversion efficiency of the system.

Design of high efficiency diode laser module for wireless power transmission

Laser wireless power transmission in unmanned aerial vehicle, satellite station and lunar robot power supply has potential application prospect, whose efficiency becomes the key to the application bottleneck. In order to improve the electro-optic conversion efficiency of the transmitter, the spot uniformity and the effective power ratio in window at the receiver, a design scheme of high efficiency diode laser for the transmitter of laser wireless power transmission was proposed. A high power and high efficiency diode laser system was designed, which is based on space combination with high efficiency, what’s more, the unevenness of the intensity at the receiving end can be optimized to 0.207, and the power ratio in the effective window is more than 94%. A laser wireless power transmission experimental device was built, whose power is over kilowatt, and the rectangular spot was outputted directly by diode laser system, which is matched with rectangular photovoltaic cell, thus the battery array layout rate was improved. The feature of multi-beam modulation was used to improve uniformity of the intensity, which is beneficial to improve the optic–electro conversion efficiency of battery and simplify the power management at the receiving end. The design and research provide reference for the practical application of laser wireless power transmission.

Bidirectional Electro-Optic Wavelength Conversion in the Quantum Ground State

Fiber optic communication is the backbone of our modern information society, offering high bandwidth, low loss, weight, size and cost, as well as an immunity to electromagnetic interference. Microwave photonics lends these advantages to electronic sensing and communication systems, but - unlike the field of nonlinear optics - electro-optic devices so far require classical modulation fields whose variance is dominated by electronic or thermal noise rather than quantum fluctuations. Here we present a cavity electro-optic transceiver operating in a millikelvin environment with a mode occupancy as low as 0.025 $\pm$ 0.005 noise photons. Our system is based on a lithium niobate whispering gallery mode resonator, resonantly coupled to a superconducting microwave cavity via the Pockels effect. For the highest continuous wave pump power of 1.48 mW we demonstrate bidirectional single-sideband conversion of X band microwave to C band telecom light with a total (internal) efficiency of 0.03 % (0.7 %) and an added output conversion noise of 5.5 photons. The high bandwidth of 10.7 MHz combined with the observed very slow heating rate of 1.1 noise photons s$^{-1}$ puts quantum limited pulsed microwave-optics conversion within reach. The presented device is versatile and compatible with superconducting qubits, which might open the way for fast and deterministic entanglement distribution between microwave and optical fields, for optically mediated remote entanglement of superconducting qubits, and for new multiplexed cryogenic circuit control and readout strategies.

Employing a Laser Headlight Electrical System to Measure and Calculate Electro-Optic Conversion Efficiencies of Blue-Beam Laser Diodes

In this study, a laser headlight electrical system was developed and implemented to measure and compare the electro-optic characteristics of the blue-beam laser diodes (BBLDs). To observe different temperatures (from negative to positive temperatures) that cause optical output power (OOP) and electrical power variations of the BBLDs, BBLDs were placed in an ambient temperature testing chamber, and the electro-optic characteristics of the BBLDs were measured to estimate the electro-optic conversion efficiencies. The different OOPs and electro-optic conversion efficiencies at different temperatures can be obtained when OOP adjustment was performed by average current and low-frequency pulse-duty cycle modulation technologies. Moreover, this study developed a human–machine interface using the LabVIEW software; therefore, the laser headlight electrical system can be controlled and monitored by a computer with the controller area network (CAN) bus communication. Finally, the prototype of the laser headlight electrical system was achieved, and three BBLDs were driven; furthermore, the white light of the headlight can be produced by mixing blue laser beams with a yellow fluorescence ceramic wafer.