High-speed Electro-optic Modulator Research Articles

Development of (Pb,La)(Zr,Ti)O3 Electro-Optic Thin Film for High-Speed Spatial Light Modulator

A high-speed electro-optic spatial light modulator (EOSLM) was successfully fabricated with (Pb,La)(Zr,Ti)O3 (PLZT) electro-optic thin film. This EOSLM has a longitudinal structure, so a large electro-optic effect is necessary for low driving voltage (<20 V). We have investigated the relationship between the orientation of polycrystalline PLZT and the electro-optic effect; we found that (111)-orientated PLZT has a large electro-optic effect, which shows a more than 0.025 refractive index change and a 183 pm/V electro-optic constant. With this PLZT film, we fabricated a prototype spatial light modulator (SLM) chip, which has 180×180 pixel arrays. The measured optical switching speed of this device was 7 ns, which is the highest switching speed for two-dimensional pixel array devices. Coded random data is clearly demonstrated with the prototype chip.

Dielectric studies of metal complexes of thiourea crystals for electro-optic modulation

In the present study three crystals of thiourea family viz. Zinc Thiourea Chloride (ZTC), Zinc Thiourea Sulfate (ZTS) and Bisthiourea Cadmium Chloride (BTCC) were grown from aqueous solution by slow evaporation technique. The grown crystals were studied by powder XRD, FT-IR and UV-visible. The dielectric study of grown crystals was carried out in X-band using transmission line wave guide method. It was found that the BTCC has lowest dielectric constant among three metal complexes of thiourea crystals (ZTC, ZTS and BTCC), therefore it can be used for high speed electro-optic modulation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

High-speed travelling-wave BaTiO 3 thin-film electro-optic modulators

The first successful realisation of high-speed travelling-wave BaTiO3 thin-film electro-optic waveguide modulators with 3 dB modulation bandwidth of 15 GHz at 1.55 µm wavelength is reported. Quasi-velocity-matched electrodes for BaTiO3 thin-film modulators are achieved by addition of a SiO2 buffer layer. Its microwave and electro-optic response are characterised.

Optimizing Design for the Traveling Wave Electrodes in Low-Drive High-Speed Electro-Optic Polymer Modulators

Electro-optic (EO) polymer modulators are very promising in the realization of cost-effective and high-performance optical transmissions. In this article, general strategies and specific designs of the traveling wave electrodes in EO polymer modulators were presented to reduce the modulator drive power while maintaining a broadband response. The optimum device parameters and corresponding conditions were estimated using finite element method based on electrode design. In calculating the results, the comprehensive characteristics of polymer modulator with 1.21 V half-wave voltage and 91 GHz bandwidth was demonstrated with electro-optic interaction length is 20 mm, electro-optic coefficient is 55 pm/V, and operation wavelength is 1.319 μm. These results agree with the 0.8 V half-wave voltage and 30 mm electro-optic interaction length reported in Science. In the five designs presented, a hybrid electrode structure combining CPW and microstrip lines were advanced. The characteristics of this structure are like that of microstrip lines with a single-arm electrode on one arm of the waveguide, but it solves the problem of microstrip to coaxial line transition and corona polarization.

High-speed silicon electrooptic Modulator design

An electrically driven Mach-Zehnder waveguide modulator based on high-index contrast silicon split-ridge waveguide technology and electronic carrier injection is proposed. The excellent optical and carrier confinement possible in high-index contrast waveguide devices, together with good thermal heat sinking and forward biased operation, enables high-speed modulation with small signal modulation bandwidths beyond 20 GHz, a V/sub /spl pi// times length figure of merit of V/sub /spl pi//L=0.5 V/spl middot/cm and an insertion loss of about 4 dB. The modulator can be fabricated in a complementary metal-oxide-semiconductor compatible way.

Micrometre-scale silicon electro-optic modulator

Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides, light emitters, amplifiers and lasers approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.

Modeling and analysis of high-speed electro-optic modulation in high confinement silicon waveguides using metal-oxide-semiconductor configuration

We analyze the electrical and optical properties of a silicon electro-optic waveguide modulator using a metal-oxide-semiconductor (MOS) configuration. The device performance is studied under different modes of operation of the MOS diode and gate oxide thicknesses. Our calculations indicate that this scheme can be used for achieving high-speed submicron waveguide active devices on silicon on insulator. A microring resonator intensity modulator is predicted to exhibit switching times on the order of tens of picoseconds with modulation depth of 73% by employing a bias voltage of only 5 V.

Performance limitations of a Y-branch directional-coupler-based polymeric high-speed electro-optical modulator

To find the optimal driving voltage and bandwidth for electro- optic polymer-waveguide-based directional couplers, four electrode structures are investigated. They are the microstrip line (MSL), the asym- metric coplanar waveguide with ground (ACWG), the coplanar wave- guide with ground (CPWG), and the edge-coupled microstrip line (CMSL). UV15:Polymethyl methacrylate/dispersed-red 1:UV11-3-based directional couplers are evaluated. The CPWG and the ACWG have al- most the same driving voltages, which are about twice the driving volt- age of the CMSL. The MSL has the largest driving voltage, which is 20 to 25% higher than the diving voltages of the CPWG and ACWG. Simula- tion results further conclude that the MSL has the largest bandwidth, and its bandwidth is about 1.6 times that of the bandwidth of the CMSL, which has the narrowest bandwidth. The bandwidths of the ACWG and CPWG are 1.4 and 1.2 times that of the CMSL, respectively. The driving voltages for the four different devices are experimentally confirmed. © 2004 Society of Photo-Optical Instrumentation Engineers.

Multisectional modeling of high-speed electrooptic modulators integrated in a microwave circuit CAD environment

We present a new multisectional model for high-speed electrooptic modulators, fully integrated within the framework of a microwave circuit computer-aided design (CAD) suite (MWOFFICE). Starting from geometrical and layout parameters, the model allows both simple (traveling-wave) and complex (phase reversal, periodically loaded) structures to be assembled, analyzed, and optimized from the standpoint of the electrical and electrooptic response (including chirp effects) both in small-signal (analog) and in large-signal (digital) operation, exploiting standard simulator tools. At no additional effort, parasitic and passive elements (such as optical or electrical delay paths) can be directly included in the modulator schematic, and the effect of transitions and package parasitics can be readily accounted for at a circuit level. Moreover, model integration within a circuit CAD suite enables one to seamlessly perform driver and modulator design and optimization within the same monolithic or hybrid circuit environment. Comparisons with experimental and literature data and design examples are presented to validate the approach and stress its potential in the design of high-speed electrooptic modulators.

High-speed electrooptic modulator characterization using optical spectrum analysis

This paper presents our latest studies on high-speed electrooptic modulator characterization using the optical spectrum analysis method. Several new characterization techniques are theoretically analyzed and experimentally demonstrated for the measurement of critical device parameters at very high modulation frequencies. Applying this method in our wide-band electrooptic (EO) modulator characterization experiment, we have successfully measured halfwave voltages, frequency responses, and the chirp parameter at frequencies over 10 GHz for several typical high-speed LiNbO/sub 3/ modulators. Our experiment showed that the optical spectrum analysis provides an accurate and convenient platform for ultra-high-speed EO modulator characterization.

Implementing of a precision fast thermoelectric cooler controller using a personal computer parallel port connection and ADN8830 controller

A complete design of a compact precision and fast thermoelectric cooler (TEC) controller with a parallel port connection to a personal computer (PC), using a pulse width modulation technique by a dedicated smart driver, and digital control designed using very high-speed integrated circuit hardware description language is presented. The design allows replacement of the PC with an “on board” embedded microcontroller. This circuit is demonstrated as a TEC controller for a high-speed electro-optical modulator.

Polarized optical absorption and photoluminescence measurements in single-crystal thin films of 4′-dimethylamino-N-methyl-4-stilbazolium tosylate

Single-crystal thin films of the anhydrous (red) and the hydrated (orange) phases of the organic salt 4′-dimethylamino-N-methyl-4-stilbazolium tosylate were grown by a modification of the shear method. The optical absorption coefficients of the films were measured with light polarized along and normal to the dipole/molecular axis at both resonant and off-resonant wavelengths, and a strong dichroism was observed at the resonant wavelengths. The absorption measurements are important considering potential applications of these films (red phase) in high-speed single-pass thin-film electro-optic modulators [M. Thakur, J. Xu, A. Bhowmik, and L. Zhou, Appl. Phys. Lett. 74, 635 (1999)] and other photonic devices. Highly polarized photoluminescence (PL) has been observed in these films. The PL efficiencies of the red- and orange-phase single-crystal films were measured to be about 12% and 14%, respectively, which are significantly higher than the maximum PL efficiency measured in solution (3%).

Optical sampling technique for fast electro-opticdevices

An optical sampling technique based on modelocked diode lasers has been used to characterise, with picosecond temporal resolution, a high-speed electro-optic modulator. A modulator bandwidth of 28 GHz was found.

Ferroelectric Liquid Crystals for Nonlinear Optics: can we Really do It?

AbstractFerroelectric liquid crystals (FLCs) are true liquids with a thermodynamically stable polar structure. Furthermore, in some systems excellent polar stereocontrol has been demonstrated (&gt; 80% of the molecular dipole oriented along the polar axis with infinite “thermal stability”). These properties make FLCs an interesting candidate for second order NLO applications. However, until now the orientation of organic functional arrays with “large β”, typified by the disperse red 1 (DRI) chromophore, has not been demonstrated.Herein we report the initial results of a study directed towards providing a solution to this problem. Specifically, a new FLC dopant wherein the DRI chromophore (p-nitro-p'-dialkyl-aminoazobenzene unit) is oriented along the polar axis in FLC mixtures up to 30% by weight is described. These results suggest that it will be possible to obtain FLCs with good stereocontrolled orientation of large β functional arrays. Given that hybrid VLSI silicon/FLC optical chips are under intense investigation as micro-displays, and manufacturing issues for this class of devices are being addressed in the display context, the materials presented here suggest VLSI/FLC chips may be useful as high speed electro-optic modulators as well.

Nlo Polymer Material Systems for Electro-Optic Devices

ABSTRACTNon linear optical (NLO) polymers have great potential to be fabricated into integrated electro-optic (E/O) devices for use as high speed electro-optic (E/O) switches, modulators and interconnects in computer and communication systems [1,2]. The fabrication of practical integrated E/O devices requires a material system that meets the final device requirements and can be processed using standard fabrication technologies [3]. Applications of polymer E/O devices in electronic systems have been limited by the relatively low thermal stability and poor processability of non linear optical (NLO) polymers. This paper describes a thermally stable electro-optic material system and the fabrication process to make compact integrated E/O devices for application in electronic systems. This material system consists of high thermal stability polyimide core and cladding materials. The active NLO material is a side chain polyimide that uses a new high activity and high thermal stability chromophore.

Novel two-arm microwave transmissionline for high-speed electro-optic polymer modulators

The authors demonstrate the use of a novel microwave design for high-speed electro-optic polymer modulators. A two-arm Mach-Zehnder-like transmission line may be used to reduce Vπ in a push-pull modulator without problems of dielectric breakdown or crosstalk during poling.

Nonlinear Optical Effects in Polar Dielectric Materials

The electro-optical and nonlinear optical properties of organic materials are reviewed. Molecular crystals, Langmuir-Blodgett films and poled polymers are shown to have interesting properties for applications as high-speed electro-optic modulators, optical frequency converters or all optical signal processors.

Low-loss silicon carbide optical waveguides for silicon-based optoelectronic devices

A SiC-on-SiO/sub 2/ waveguide structure is proposed and analyzed. The analysis shows that the planar SiC waveguide has low loss and good beam confinement in the guiding core for the fundamental mode at 1.3 mu m and 0.7 mu m. In addition, such a waveguide displays strong mode discrimination (>20 dB) between the fundamental and the higher-order modes. Single-mode SiC/SiO/sub 2/ rib waveguides with large dimensions are also analyzed. The waveguides are single-moded even if the waveguide dimensions are large as long as the rib width-height ratio is appropriate. In addition, such large-dimension rib waveguides should exhibit low loss due to the large SiC-layer thickness and can be used for waveguiding either over the communication wavelength range 1.3-1.6 mu m or the silicon light source at 0.7 mu m. Furthermore, electrooptic modulators can potentially be fabricated with SiC-on-SiO/sub 2/ waveguide structures compactly. Such modulators should offer potential candidates for high-speed electrooptic modulation for silicon-based optoelectronic devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Organic Molecular Crystals for Optical Data Processing

Abstract We report on the nonlinear optical properties of a new class of organic compounds built of trihalides interacting weakly with donor type molecules. The adducts of iodoform with sulphur (CHI3. 3S8) and iodoform with quinoline (CHI3.3C9H7N) exhibit sizeable electrooptic effects and second harmonic generation comparable to those of the most efficient organic coumpounds such as MNA (methylnitroaniline). For both iodoform compounds the angle-tuned phase matching of type I and II has been observed. The comparison between the electrooptic effect and the second harmonic generation suggests that in these materials the electrooptic effect is mostly electronic in origin. This permits the construction of high speed electrooptical modulators and switching devices operating at very high frequencies up to the terahertz region. The macroscopic optical nonlinearity of the adducts stems mainly from the nonlinearity of the iodoform molecule. The largest electrooptic coefficients (r22 = 2.2pm/V) and the largest nonl...

Microwave characteristics of high-speed traveling-wave electrooptic modulators on III-V semiconductors

Microwave characteristics of III-V semiconductor traveling wave electrooptic modulators were studied rigorously by using the method of lines. This approach makes it possible to construct a complete computer model of double-rib, multilayer strip waveguide modulators which are out of reach of the classical methods. Both p-i-n junction and Schottky-barrier junction controlled devices have been investigated. The fringing microwave field has been found to play an important role in improving the modulator bandwidth. For the first time, a nonperfect electrode of finite thickness has been modeled. The method of lines algorithm has proved to be a valuable CAD tool for design and optimization of high-speed modulators. >