Electro-optic Modulator Device Research Articles

Lithium Niobate Electro-Optic Modulation Device without an Overlay Layer Based on Bound States in the Continuum.

Electro-optic modulation devices are essential components in the field of integrated optical chips. High-speed, low-loss electro-optic modulation devices represent a key focus for future developments in integrated optical chip technology, and they have seen significant advancements in both commercial and laboratory settings in recent years. Current electro-optic modulation devices typically employ architectures based on thin-film lithium niobate (TFLN), traveling-wave electrodes, and impedance-matching layers, which still suffer from transmission losses and overall design limitations. In this paper, we demonstrate a lithium niobate electro-optic modulation device based on bound states in the continuum, featuring a non-overlay structure. This device exhibits a transmission loss of approximately 1.3 dB/cm, a modulation bandwidth of up to 9.2 GHz, and a minimum half-wave voltage of only 3.3 V.

Active metasurface in the near-infrared region by gating ultrathin TiN films.

Ultrathin titanium nitride (TiN) films have become a novel material flatform for constructing active metasurfaces in the near-infrared region. In this Letter, we numerically achieved the dual functions of switchable linear dichroism (LD) and tunable perfect absorption in a G-shape gold resonators/TiN film hybrid metasurface by gating ultrathin TiN films. As the carrier density of TiN decreases, the modulation depth for LD strength is about 70% at 1211 nm. Meanwhile, the response wavelength of perfect absorption (∼1) shifts to the blue by around 130 nm with a change of carrier density of 12%. Our proposed active metasurface with the capability of strength-switchable LD and wavelength-tunable perfect absorption has considerable potential in dynamic electro-optic modulation and flat photonic devices with reconfigurable functionalities.

High figure of merit observed in SBN thin film based EO modulator employing WCSPR technique

Present work demonstrates an efficient Waveguide coupled Surface Plasmon Resonance (WCSPR) based electro-optic (EO) modulator device utilizing Strontium Barium Niobate (SBN) films with enhanced figure of merit. Pulsed laser deposition (PLD) technique was employed to monitor the effect of incident laser fluence from 1.4Jcm-2 to 1.6Jcm-2 on the crystallographic property of Sr0.75Ba0.25Nb2O6(SBN75). For comparison Sr0.60Ba0.40Nb2O6(SBN60) thin film deposited under optimized conditions were also utilized for studying the characteristics of developed WCSPR-EO modulator. Enhancement in the resolution of the WCSPR-EO system from 1.61RIU-1 for SBN60 thin film to 0.59RIU-1 for SBN75 thin film has been obtained. Improved Figure of merit (FOM) with higher sensitivity of about 47.5° and maximum modulation index of 41.73% estimated for prism/air–gap/Au/SBN75/LSCO/Si (WCSPR-EO) modulator system which paves a way for potential application of SBN75 thin film for optoelectronic devices.

Towards low-power near-infrared modulators operating at telecom wavelengths: when graphene plasmons frustrate their metallic counterparts

A free-space electro-optic modulator device exploiting graphene’s surface plasmon polariton (SPP) at near-infrared frequencies is proposed and theoretically studied. The device is made up of two resonant structures, the first being a metallic SPP displaying broadband absorption, and the second graphene’s own SPP, which is shown to frustrate the metallic plasmon when excited, leading to a narrow reflectance peak. Doping of the graphene to achieve Fermi-level tuning is shown to shift the wavelength of the frustration phenomenon, thereby enabling the use of the device as a modulator. A reduction of 20% in the switching energy is expected due to the unique principle of operation which, crucially and contrary to most work in this field, does not rely on electroabsorption but electrorefraction changes in graphene. This coupled SPP resonator geometry also permits efficient channeling of optical energy from free space into graphene’s SPP at near-infrared frequencies.

Integrated electro-optic modulators in x-cut lithium niobate thin film

Integrated optics is poised to revolutionize several data communication applications. The development of high performance electro-optic modulators is essential for the technology to be viable. In this paper, single-mode electro-optic modulators in x-cut lithium niobate thin film are designed, simulated, and analyzed. The single-mode conditions of lithium niobate ridge waveguides are analyzed in detail. The design parameters of Y-branch and separation distances between electrodes and ridge waveguides are optimized. The half-wave voltage of the electro-optic modulator with device lengths of 10 mm is determined. The half-wave voltage-length product is about 2.2 V·cm indicating the efficient electric-optical modulation. This study is helpful for understand of electro-optic modulator structures in lithium niobate thin film, as well as for the fabrication of high-performance and multifunctional electro-optic modulation devices.

Dynamic electro-optic response of graphene/graphitic flakes in nematic liquid crystals

Electric field induced dynamic reorientation phenomenon of graphene/graphitic flakes in homogeneously aligned nematic liquid crystal (NLC) medium has been demonstrated by optical microscopy. The flakes reorient from parallel to perpendicular configuration with respect to boundary plates of confining cells for an applied field strength of as low as tens of millivolt per micrometer. After field removal the reoriented flakes recover to their initial state with the help of relaxation of NLC. Considering flake reorientation phenomenon both in positive and negative dielectric anisotropy NLCs, the reorientation process depends on interfacial Maxwell-Wagner polarization and NLC director reorientation. We propose a phenomenological model based on electric field induced potential energy of graphitic flakes and coupling contribution of positive NLC to generate the rotational kinetic energy for flake reorientation. The model successfully explains the dependence of flake reorientation time over flake shape anisotropy, electric-field strength, and flake area. Using present operating scheme it is possible to generate dark field-off state and bright field-on state, having application potential for electro-optic light modulation devices.

CMOS compatible micro-oven heater for efficient thermal control of silicon photonic devices

We present a heater design for efficient thermo-optic control of silicon photonic devices. The oven-shaped heater is simply realized by using metal contacts/via's in a standard CMOS process. We found both theoretically and experimentally that the micro-oven doubles the heating efficiency over traditional metal strip heaters. Compared to existing high efficiency heater designs, the oven heater is more robust and most importantly it can be easily integrated into electro-optic modulator devices.

Speed Performance Degradation of Electrooptic Modulator Devices by Neutrons Irradiations at High Temperature Effects

In the present paper, we have deeply investigated the transmission efficiency degradation of electrooptic modulator devices in thermal irradiated hard environments over wide range of the operating parameters. It is well known that the radiation-induced electrooptic modulator defects can modify the initial doping concentrations, creating generation-recombination centres and introducing trapping of carriers. Additionally, rate of the lattice defects is thermally activated and reduces for increasing irradiation temperature as a result of annealing of the damage. Both the ambient temperature and the irradiation dose possess sever effects on the electro-optical characteristics and consequently the performance characteristics of electroptic modulator devices. As well as we have deeply developed the modelling basics of electrooptic modulator devices, which may be used to analyzed the modulator quantum efficiency, dark current, modulating voltage, modulating frequency, 3-dB bandwidth, transmitted signal bandwidth, modulator quality factor, modulator sensitivity, modulator sensitivity bandwidth product, switching voltage, modulator device performance index, operating switching time and speed response of these irradiated electrooptic modulator devices after different irradiation fluences.

Ultra High Speed Semiconductor Electrooptic Modulator Devices for Gigahertz Operation in Optical Communication Systems

The effects of electrodes geometry and temperature on high frequency radio frequency transmission characteristics are deeply investigated against semiconductor material based electro optic modulator devices such as aluminum gallium arsenide (AlGaAs) and optical waveguide parameters. On the other hand, we have developed the optimization of the electro-optic modulator parameters where the effective index plays an essential role in the evaluation of the bandwidth structure. Therefore, a theoretical analysis of the capacitance, the characteristic impedance and the effective index determine how to increase the bandwidth. The effects of design parameters on the modulating voltage and optical bandwidth are also investigated for different materials based electro-optic modulators by using rigorous transmission modeling techniques. The low-loss wide-bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics.

High speed performance of semiconductor electrooptic modulators for multi Gigahertz communication systems operation

The effects of electrodes geometry and temperature on high frequency radio frequency transmission characteristics are deeply investigated against semiconductor material based electro optic modulator devices such as aluminum gallium arsenide (AlGaAs) and optical waveguide parameters. On the other hand, we have developed the optimization of the electro-optic modulator parameters where the effective index plays an essential role in the evaluation of the bandwidth structure. Therefore, a theoretical analysis of the capacitance, the characteristic impedance and the effective index determine how to increase the bandwidth. The effects of design parameters on the modulating voltage and optical bandwidth are also investigated for different materials based electro-optic modulators by using rigorous transmission modeling techniques. The low-loss wide-bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals, while the development of high capacity optical communication systems has required the use of microwave techniques in optical transmitters and receivers. These two strands have led to the development of the research area of microwave photonics. Key words: Electrooptic modulator, semiconductor material, optical bandwidth, high transmission performance.

Cascaded Bragg reflectors for a barium titanate thin film electro-optic modulator

An electro-optic modulator integrated with a Bragg reflector structure utilizing a barium titanate thin film platform is proposed and its optical properties are simulated. An electro-optic modulator with a drive voltage-length product of 27 mV cm is achievable with a cascaded Bragg reflector structure. Phase matching conditions can be obtained using a simple Bragg reflector structure, and a > 100 GHz bandwidth is predicted for a millimetre-long electro-optic modulator device.

Responsivity optimization and stabilization in electro-optic field sensors

Electro-optic (EO) modulation devices, which utilize an external electric field to modulate a beam of optical radiation, are strongly affected by parasitic effects, which change the polarization state of the optical beam. As a result, very small changes in the birefringence or optical path length within the EO material can result in very large fluctuations of the amplitude and phase of the optical modulation signal. A method of actively analyzing the modulated beam is described and demonstrated, which eliminates these fluctuations and keeps the modulation device stably operating at its peak responsivity. Applications to electric field detection and measurements are discussed.

Intercalated Smectic A Phases in Banana‐Shaped Liquid Crystals with Carbonate End Groups

Novel, symmetrical, bent-core mesogens, namely substituted 1,3-phenylenebis{4'-[(ethoxycarbonyl)oxy]-1,1'-biphenyl}-4-carboxylates, are prepared with carbonate groups at both ends of the molecules. The mesophase properties are investigated for different electron-donating and -withdrawing substituents connected to the central ring at different positions. These compounds exhibit nematic and/or smectic A intercalated (SmA(int)) mesophases. Electro-optical studies show a very significant electric-field-induced biaxiality that is fast (<1 ms) and large (0.03) associated with a high birefringence (0.33 at 500 nm, 10 V mum(-1) field) for the unsubstituted analogue. For one substance this effect is observable from above 100 degrees C down to room temperature. Such electric-field-induced biaxiality may find practical applications in fast electro-optic modulation devices.

One-dimensional photonic crystals in reflection geometry for optical applications

We investigate some properties of one-dimensional photonic band-gap materials that have the possibility of total internal reflection at one or more interfaces. The proposed structures have application for electro-optic modulation, sensing, and other optical devices. A specific example for electro-optic modulation is presented. Certain advantages of this arrangement may make it a desired geometry for specific applications like sensing.

Polymeric electro-optic materials: optimization of electro-optic activity, minimization of optical loss, and fine-tuning of device performance

Larry R. DaltonUniversity of WashingtonDepartment of ChemistrySeattle, Washington 98195-1700andUniversity of Southern CaliforniaLoker Hydrocarbon Research InstituteLos Angeles, California 90089-1661E-mail: dalton@chem.washington.eduE-mail: ldalton@methyl.usc.eduAbstract. Translation of the large molecular hyperpolarizability of chro-mophores into large macroscopic electro-optic activity by electric fieldpoling of chromophore-containing polymers is opposed by molecular-shape-dependent intermolecular electrostatic interactions. Modificationof chromophore structure (shape) to minimize the deleterious effect ofsuch interactions leads to significant improvement in electro-optic activ-ity. Drive voltage requirements for polymeric modulator devices are re-duced to values ranging from 0.7 to 5 V. Optical loss of electro-opticpolymer materials, at the communication wavelengths of 1.3 and 1.55mm, is defined by C–H, O–H, and N–H vibrational absorptions and byscattering from index of refraction gradients in the material. The formerare significantly reduced by partial deuteration and halogenation to val-ues slightly less than 1 dB/cm. A major source of optical loss encoun-tered in the utilization of polymeric electro-optic modulator devices iscoupling losses associated with the mode mismatch between silica fiberwaveguides and polymeric modulator waveguides. Recently, alternativecoupling strategies based on utilization of tapered transitions and verticaltransitions have dramatically reduced coupling losses. Total insertionlosses comparable to those for lithium niobate devices are realized. Fi-nally, a phototrimming technique is developed that enables fine-tuning ofthe performance of circuit elements such as power splitters.

Quantum-confined stark effect in single CdSe nanocrystallite quantum dots

The quantum-confined Stark effect in single cadmium selenide (CdSe) nanocrystallite quantum dots was studied. The electric field dependence of the single-dot spectrum is characterized by a highly polarizable excited state ( approximately 10(5) cubic angstroms, compared to typical molecular values of order 10 to 100 cubic angstroms), in the presence of randomly oriented local electric fields that change over time. These local fields result in spontaneous spectral diffusion and contribute to ensemble inhomogeneous broadening. Stark shifts of the lowest excited state more than two orders of magnitude larger than the linewidth were observed, suggesting the potential use of these dots in electro-optic modulation devices.

The Prom Device In Optical Processing Systems

The operation of an electro-optic image modulator device for use in real-time optical processing systems is described. The PROM (Pockel's Read-Out Optical Modulator) is used to provide temporary storage of image or digital data which can then be read out by a laser for coherent optical processing. The stored image may undergo certain operations, such as level slicing, edge enhancement, or contrast inversion by utilizing the electronic characteristics of the device. This feature is useful for incoherent image processing, and also allows zero order suppression in coherent processing applications. The rapid recyclability, high optical quality and high resolution demonstrated by the device are required for practical utilization of the device in the applications described.

Stress Plate Optical Modulator for Circular Dichroism Measurements

The fused silica stress plate modulator described below offers several advantages over the other known electrooptic modulation devices: primarily, high transmission over a broad wavelength range, and large aperture. When operated at its electromechanical resonance frequency of 16.7 kHz, the modulator requires only low voltage, low power drive to operate as a +/-lambda/4 plate. Complete constructional details are given, including a model from which resonance frequencies may be calculated. As part of a circular dichroism apparatus, the modulator has allowed measurement of effects as small as 1 part in 10(5). The possibility of extension of the operating range into the vacuum uv is discussed.