Electro-optical dual modulation on resistive switching behavior in BaTiO3/BiFeO3/TiO2 heterojunction

The novel BaTiO3/BiFeO3/TiO2 multilayer heterojunction is prepared on a fluorine-doped tinoxide(FTO) substrate by the sol–gel method. The results indicate that the Pt/Ba TiO3/BiFeO3/TiO2/FTO heterojunction exhibits stable bipolar resistive switching characteristic, good retention performance, and reversal characteristic. Under different pulse voltages and light fields, four stable resistance states can also be realized. The analysis shows that the main conduction mechanism of the resistive switching characteristic of the heterojunction is space charge limited current(SCLC) effect. After the comprehensive analysis of the band diagram and the P–E ferroelectric property of the multilayer heterojunction, we can deduce that the SCLC is formed by the effect of the oxygen vacancy which is controlled by ferroelectric polarizationmodulated change of interfacial barrier. And the effective photo-generated carrier also plays a regulatory role in resistance state(RS), which is formed by the double ferroelectric layer Ba TiO3/BiFeO3 under different light fields. This research is of potential application values for developing the multi-state non-volatile resistance random access memory(RRAM) devices based on ferroelectric materials.

Modulation Depth Based on Frequency-shift Characteristic of LiNbO3 Waveguide Electro-optic Intensity Modulator

The modulation depth, defined according to practical modulation results, which changes with the microwave power and its frequency, is significant for systems utilizing the frequency-shift characteristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator （EOIM）. By analyzing the impedance mismatch between the microwave source and the EOIM, the effective voltage applied to the RF port of the EOIM is deprived from the microwave power and its frequency. Associating with analyses of the phase velocity mismatch between the microwave and the optical wave, the theoretical modulation depth has been obtained, which is verified by experimental results. We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias for the system based on the frequency-shift characteristic of the EOIM.

A High-Performance Silicon Electro-Optic Phase Modulator with a Triple MOS Capacitor

We propose and analyze a novel Si-based electro-optic modulator with an improved metal-oxide-semiconductor （MOS） capacitor configuration integrated into silicon-on-insulator （SOl）. Three gate-oxide layers embedded in the silicon waveguide constitute a triple MOS capacitor structure, which boosts the modulation efficiency compared with a single MOS capacitor. The simulation results demonstrate that the Vπ Lπ product is 2. 4V · cm. The rise time and fall time of the proposed device are calculated to be 80 and 40ps from the transient response curve, respectively,indicating a bandwidth of 8GHz. The phase shift efficiency and bandwidth can be enhanced by rib width scaling.

Mach-Zehnder Electro-Optic Polymer Modulator with C orona Poled Core Layer

A Mach-Zehnder(MZ) electro-optic(EO) modulator are real iz ed,with three optical layers as polymer materials.The functional layer is the co rona poled crosslinkable polyurethane.The ridge waveguide is fabricated by using the spin-coating,poling,photolithography and oxygen reactive ion etching(RIE) techniques.The mode and the modulation properties of these devices are demonstra ted in a micron control system,while the light source works at the wavelength of 1 31 or 1 55 micron.

Organic electro-optic polymer materials and organic-based hybrid electro-optic modulators

High performance electro-optic modulator,as the key device of integrated ultra-wideband optical systems,have be-come the focus of research.Meanwhile,the organic-based hybrid electro-optic modulators,which make full use of the advant-ages of organic electro-optic(OEO)materials(e.g.high electro-optic coefficient,fast response speed,high bandwidth,easy pro-cessing/integration and low cost)have attracted considerable attention.In this paper,we introduce a series of high-perform-ance OEO materials that exhibit good properties in electro-optic activity and thermal stability.In addition,the recent progress of organic-based hybrid electro-optic devices is reviewed,including photonic crystal-organic hybrid(PCOH),silicon-organic hy-brid(SOH)and plasmonic-organic hybrid(POH)modulators.A high-performance integrated optical platform based on OEO ma-terials is a promising solution for growing high speeds and low power consumption in compact sizes.

Measurement of Frequency Shift Characteristics Based on LiNbO_3 Waveguide Electro-Optic Intensity Modulator

High-speed and wide-band LiNbO3 waveguide electro-optic intensity modulator has drawn great attention in the field of optical fiber communication and sensor. This paper reports the research results on the measurement of frequency shift characteristics of Mach-Zehnder electro-optic intensity modulator. Two measurement methods of frequency shift characteristics for high and low frequency modulations are studied in theory and experiment and demonstrate different results. The realization of a multi-wavelength optical source based on Mach-Zehnder electro-optic intensity modulator has been introduced. The technique to reach the maximum intensity for interesting shift frequency, particularly for heterodyne detection of Brillouin distributed optical fiber sensing, has been given.

Low-power electro-optic phase modulator based on multilayer graphene/silicon nitride waveguide

Electro-optic modulator is a key component for on-chip optical signal processing.An electro-optic phase modulator based on multilayer graphene embedded in silicon nitride waveguide is demonstrated to fulfill low-power operation.Finite element method is adopted to investigate the interaction enhancement between the graphene flake and the optical mode.The impact of multilayer graphene on the performance of phase modulator is studied comprehensively.Simulation results show that the modulation efficiency improves with the increment of graphene layer number,as well as the modulation length.The 3-dB bandwidth of around 48 GHz is independent of graphene layer number and length.Compared to modulator with two-or four-layer graphene,the six-layer graphene/silicon nitride waveguide modulator can realizeπphase shift at a low-power consumption of 14 fJ/bit when the modulation length is 240μm.

Analysis of electro-optical intensity modulator for bunch arrival-time monitor at SXFEL

A bunch arrival-time monitor(BAM) based on an electro-optical intensity modulation scheme is currently under development at Shanghai Soft X-ray Free-Electron Laser to meet the high-resolution requirements for bunch stability. The BAM uses a radio frequency signal generated by a pickup cavity to modulate the reference laser pulses in an electro-optical intensity modulator(EOM), and the bunch arrival-time information is derived from the amplitude change of the laser pulse after laser pulse modulation.EOM is a key optical component in the BAM system.Through the basic principle analysis of BAM, many parameters of the EOM are observed to affect the measurement resolution of the BAM system. Therefore, a systematic analysis of the EOM is crucial. In this paper, we present two schemes to compare and analyze an EOM and provide a reference for selecting a new version of the EOM.

Magneto and Electro-Optic Intensity Modulator Based on Liquid Crystal and Magnetic Fluid Filled Photonic Crystal Fiber

We propose a novel light intensity modulator based on magnetic fluid and liquid crystal（LC） filled photonic crystal fibers（PCFs）. The influences of electric and magnetic fields on the transmission intensity are theoretically and experimentally analyzed and investigated. Both the electric and magnetic fields can manipulate the molecular arrangement of LC to array a certain angle without changing the refractive index of the LC. Therefore, light loss in the PCF varies with the electric and magnetic fields whereas the peak wavelengths remain constant. The experimental results show that the transmission intensity decreases with the increase of the electric and magnetic fields. The cut-off electric field is 0.899 V/um at 20 Hz and the cut-off magnetic field is 195 m T. This simple and compacted optical modulator will have a great prospect in sensing applications.

Experimental comparison between corona and contact poling for EO polymer modulators

Two different poling techniques-corona poling and contact poling in the backdrop of electro-optic （EO） polymer modulators are compared. A 3-layer structure EO polymer modulator is prepared for the poling. The poling setups and procedures of these two different methods are given. It is found that a well-controlled precure step is very critical, otherwise it will result in either lower poling efficiency or damaged film. Experimental results show that contact poling does not create severe surface damage as corona poling and poling voltage is much lower, but corona poling provides higher EO effect than contact poling. Besides, contact poling can provide poling size as large as the substrate size.

Broad-band spatial light modulation with dual epsilon-near-zero modes

Epsilon-near-zero(ENZ)modes have attracted extensive interests due to its ultrasmall mode volume resulting in ex-tremely strong light-matter interaction(LMI)for active optoelectronic devices.The ENZ modes can be electrically toggled between on and off states with a classic metal-insulator-semiconductor(MIS)configuration and therefore allow access to electro-absorption(E-A)modulation.Relying on the quantum confinement of charge-carriers in the doped semiconductor,the fundamental limitation of achieving high modulation efficiency with MIS junction is that only a nanometer-thin ENZ confinement layer can contribute to the strength of E-A.Further,for the ENZ based spatial light modulation,the require-ment of resonant coupling inevitably leads to small absolute modulation depth and limited spectral bandwidth as restric-ted by the properties of the plasmonic or high-Q resonance systems.In this paper,we proposed and demonstrated a dual-ENZ mode scheme for spatial light modulation with a TCOs/dielectric/silicon nanotrench configuration for the first time.Such a SIS junction can build up two distinct ENZ layers arising from the induced charge-carriers of opposite polar-ities adjacent to both faces of the dielectric layer.The non-resonant and low-loss deep nanotrench framework allows the free space light to be modulated efficiently via interaction of dual ENZ modes in an elongated manner.Our theoretical and experimental studies reveal that the dual ENZ mode scheme in the SIS configuration leverages the large modulation depth,extended spectral bandwidth together with high speed switching,thus holding great promise for achieving electric-ally addressed spatial light modulation in near-to mid-infrared regions.

Simulation design of thin film lithium niobate electro-optic modulator with bimetallic layer electrodes

Thin-film lithium niobate electro-optical modulator will become the key device in the future optical communication,which has the advantages of high modulation rate,low half-wave voltage,large bandwidth,and easy integration compared with conventional bulk lithium niobate modulator.However,because the electrode gap of the lithium niobate film modulator is very narrow,when the microwave frequency gets higher,it leads to higher microwave loss,and the electro-optical performance of the modulator will be greatly reduced.Here,we propose a thin film lithium niobate electro-optic modulator with a bimetallic layer electrode structure to achieve microwave loss less than 8 dB/cm in the range of 200 GHz,exhibiting a voltage-length product of 1.1 V·cm and a 3 dB electro-optic bandwidth greater than 160 GHz.High-speed data transmission test has been performed,showing good performance.

Potassium tantalate niobate crystals:Efficient quadratic electro-optic materials and their laser modulation technology

Electro-optic(EO)crystals are important material for all-solid-state laser technology,which can be used to fabricate various laser modulators,such as EO switches,laser deflectors,and optical waveguide.The improvements in new high-efficiency EO crystal materials have held great significance to the development of laser technology.Potassium tantalate niobate(KTN)is a popular multifunctional crystal because of its remarkable and excellent quadratic EO effect.KTN EO modulation technology offers numerous advantages,such as high efficiency,good stability,a quick response time,and inertia-free characteristics.In this paper,we summarize the research progress of KTN series crystals systemically,including the theoretical exploration on quadratic EO effect,solid-melt crystal growth technique,comprehensive physical characterization,new physical effect and mechanisms exploration,new EO devices development and design.The EO modulation technique based on the Kerr effect of KTN series crystal offers obvious advantages in reducing the drive voltage and device size,which could better meet the developmental needs of future lasers with a wide wavelength,miniaturization,and integration.This may provide theoretical guidance and an experimental basis for the design and development of new EO crystal devices and promote the development of laser technology.

Fluorescence emission difference microscopy based on polarization modulation

In this paper,we propose a new fluorescence emission difference microscopy(FED)technique based on polarization modulation.An electro-optical modulator(EOM)is used to switch the excitation beam between the horizontal and vertical polarization states at a high frequency,which leads to solid-and donut-shaped beams after spatial light modulation.Experiment on the fluorescent nanoparticles demonstrates that the proposed method can achieve~λ=4 spatial resolution.Using the proposed system,the dynamic imaging of subcellular structures in living cells over time is achieved.

Coupled thermal-optic effects and electrical modulation mechanism of birefringence crystal with Gaussian laser incidence

We study the Gaussian laser transmission in lithium niobate crystal（LiNbO3） by using the finite element method to solve the electromagnetic field＇s frequency domain equation and energy equation. The heat generated is identified by calculating the transmission loss of the electromagnetic wave in the birefringence crystal, and the calculated value of the heat generated is substituted into the energy equation. The electromagnetic wave＇s energy losses induced by its multiple refractions and reflections along with the resulting physical property changes of the lithium niobate crystal are considered.Influences of ambient temperature and heat transfer coefficient on refraction and walk-off angles of O-ray and E-ray in the cases of different incident powers and crystal thicknesses are analyzed. The E-ray electrical modulation instances, in which the polarized light waveform is adjusted to the rated condition via an applied electrical field in the cases of different ambient temperatures and heat transfer coefficients, are provided to conclude that there is a correlation between ambient temperature and applied electrical field intensity and a correlation between surface heat transfer coefficient and applied electrical field intensity. The applicable electrical modulation ranges without crystal breakdown are proposed. The study shows that the electrical field-adjustable heat transfer coefficient range becomes narrow as the incident power decreases and wide as the crystal thickness increases. In addition, it is pointed out that controlling the ambient temperature is easier than controlling the heat transfer coefficient. The results of the present study can be used as a quantitative theoretical basis for removing the adverse effects induced by thermal deposition due to linear laser absorption in the crystal, such as depolarization or wave front distortion, and indicate the feasibility of adjusting the refractive index in the window area by changing the heat transfer boundary conditions in a wide-spectrum laser.

Greatly enhanced electro-optic modulation efficiency in titanium in-diffusion PIN-PMN-PT waveguide

Electro-optic modulators,which convert electrical signals onto the transmission light,are key devices in electro-optic modulating systems.Modulation efficiency is one of the most important parameters of an electro-optic modulator,which directly determines the footprint and power consumption of the device.Generally,modulation efficiency strongly depends on the electro-optic response of the crystal.The Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)(PIN-PMN-PT)single crystal with giant electro-optic coefficient(λ_(c))and high transparency indicates the potential to achieve greatly enhanced modulation efficiency.In this study,a prototype PIN-PMN-PT phase modulator was fabricated based on a titanium(Ti)in-diffusion waveguide,which is reported for the first time.The influences of titanium in-diffusion on the composition and domain structure of the PIN-PMN-PT single crystal were studied by transmission electron microscopy(TEM)and piezoelectric force microscopy(PFM),respectively.Finally,a half-wave voltage(V_(π))of 2.3 V was obtained using a device with 6-mm-long(L)electrodes.Furthermore,the electro-optic modulation efficiency(V_(π)L)was calculated as 1.38 V-cm,which was approximately one order of magnitude lower than that of commercial lithium niobate(LiNbO_(3),LN)phase modulators.Such enhanced modulation efficiency indicates more compact device and lower power consumption,which is of great significance for electro-optic modulation systems used in micro-fiber gyroscope,integrated photonic devices,etc.

Parallel generation of low-correlation wideband complex chaotic signals using CW laser and external-cavity laser with self-phase-modulated injection

A novel scheme for generating optical chaos is proposed and experimentally demonstrated,which supports to simultaneously produce two low-correlation chaotic signals with wideband spectrum and suppressed time-delay-signature(TDS).In the proposed scheme,we use the output of an external-cavity semiconductor laser(ECSL)as the driving signal of a phase modulator to modulate the output of a CW laser.Then the phase-modulated continuous-wave(CW)light is split into two parts,one is injected back into the ECSL that outputs one chaotic signal,while the other part is passed through a dispersion module for generating another chaotic signal simultaneously.The experimental results prove that the proposed scheme has three merits.Firstly,it can improve the bandwidth of ECSL-based chaos by several times,and simultaneously generate another wideband flat-spectrum chaotic signal.Secondly,the undesired TDS characteristics of the simultaneously-generated chaotic signals can be efficiently suppressed to an indistinguishable level within a wide parameter range,as such the complexities of the chaotic signals are considerably high.Thirdly,the correlation coefficient between these two simultaneously-generated chaotic signals is smaller than 0.1.The proposed scheme provides an attractive solution for parallel multiple chaos generation,and shows great potential for multiple channel chaos communications and multiple random bit generations.

Femtojoule electro-optic modulation using a silicon– organic hybrid device

Energy-efficient electro-optic modulators are at the heart of short-reach optical interconnects,and silicon photonics is considered the leading technology for realizing such devices.However,the performance of all-silicon devices is limited by intrinsic material properties.In particular,the absence of linear electro-optic effects in silicon renders the integration of energy-efficient photonic–electronic interfaces challenging.Silicon–organic hybrid(SOH)integration can overcome these limitations by combining nanophotonic silicon waveguides with organic cladding materials,thereby offering the prospect of designing optical properties by molecular engineering.In this paper,we demonstrate an SOH Mach–Zehnder modulator with unprecedented efficiency:the 1-mm-long device consumes only 0.7 fJ bit^(-1) to generate a 12.5 Gbit s^(-1) data stream with a bit-error ratio below the threshold for hard-decision forward-error correction.This power consumption represents the lowest value demonstrated for a non-resonant Mach–Zehnder modulator in any material system.It is enabled by a novel class of organic electro-optic materials that are designed for high chromophore density and enhanced molecular orientation.The device features an electro-optic coefficient of r33<180 pm V^(-1) and can be operated at data rates of up to 40 Gbit s^(-1).

The effect of conductor loss on half-wave voltage and modulation bandwidth of electro-optic modulators

In this paper, we theoretically deduce the expressions of half-wave voltage and 3-dB modulation bandwidth in which conductor loss is taken into account. The results suggest that it will affect the theoretical values of half-wave voltage and bandwidth as well as the optimized electrode's dimension whether considering the conductor loss or not. As an example, we present a Mach-Zehnder (MZ) type polymer waveguide amplitude modulator. The half-wave voltage increases by 1 V and the 3-dB bandwidth decreases by 30% when the conductor loss is taken into account. Besides, the effects of impedance mismatching and velocity mismatching between microwave and light wave on the half-wave voltage, and 3-dB bandwidth are discussed.

An autobias control system for the electro optic modulator used in a quantum key distribution system

In a quantum key distribution system, it is crucial to keep the extinction ratio of the coherent pulses stable. This means that the direct current bias point of the electro-optic modulator （EOM） used for generating coherent pulses must be locked. In this paper, an autobias control system based on a lock-in-amplifier for the EOM is introduced. Its drift information extracting theory and control method are analyzed comprehensively. The long term drift of the extinction ratio of the coherent pulses is measured by a single photon detector, which indicates that the autobias control system is effective for stabilizing the bias point of the EOM.