Substrate removed GaAs-AlGaAs electrooptic modulators

A novel GaAs-AlGaAs electrooptic modulator utilizing push-pull metal electrodes was fabricated using substrate removal techniques and polymer integration. The scheme enables a significant drive voltage reduction over previous designs and should enable ultrahigh-speed adjustable chirp operation     

Narrow bandwidth electrooptic polarization modulator using GaAs quantum-well waveguides

An electrooptic TE-TM polarization converter using a strip-loaded GaAs-AlGaAs multiple quantum well waveguide is discussed. At a wavelength of 870.5 nm, or an energy of approximately 50 meV below the heavy hole exciton resonance, a polarization conversion efficiency of 0.6 degrees /V-mm has been achieved. In addition, a spectral bandwidth of approximately 0.6 nm has been measured for a 3.8-mm-long device. Results indicate that modal birefringence and electroabsorption, due to exciton broadening in the presence of a lateral field, has a significant effect on device efficiency and spectral bandwidth. The mode converter described should be well-suited for use with semiconductor laser diodes in optical signal processing and computing applications.<>     

A polarization independent guided-wave LiNbO/sub 3/ electrooptic switch employing polarization diversity

A 2*2 lithium niobate optical switch is demonstrated which uses polarization diversity to obtain polarization-independent operations with good crosstalk, a simple electrical drive configuration, and low drive voltage. The switch, on Z-cut LiNbO/sub 3/, is suitable for operation at 1.3 mu m with standard single-mode fibers. Resonant metal-loaded directional coupler mode-splitters enable the processing of each polarization component to be separately optimized. Switching voltages of 7 V for transverse magnetic and 24 V for transverse electric components have been achieved using a single substrate.<>     

Acoustooptic resonance in deep-etched GaAs-AlGaAs electrooptic modulators

Deep-etched GaAs-AlGaAs waveguide modulators are shown to generate acoustic waves that can cause elastooptic anomalies in the modulator response. The theory of acoustooptic interactions in linear electrooptic modulators is described and a one-dimensional (1-D) approximation of a deep-etched GaAs-AlGaAs waveguide modulator is developed. The 1-D theory is shown to predict the acoustooptic resonance phenomena that is seen in experimental devices.     

A field induced guide-antiguide modulator of GaAs-AlGaAs

A guide-antiguide modulator of GaAs-AlGaAs using the electric-field-induced waveguide concept was demonstrated. The device was formed with a central waveguide electrode sandwiched between two antiguide electrodes on the surface of a p-i-n multiple quantum well (MQW). Switching between lateral guiding and antiguiding was accomplished by reverse biasing either the central electrode or the adjacent electrodes to increase the index beneath these respective regions. The on-off ratio was measured to be 20:1 with a propagation loss of the on-state of about 5 dB/mm.<>     

A mechanically biased electrooptic polymer modulator

Mechanical biasing of an electrooptic polymer modulator is proposed and demonstrated by heterogeneously integrating waveguide structures with a piezoelectric element. Biasing is achieved by changing the path-length of one arms of a Mach-Zehnder interferometer by mechanically bending the waveguide structure. Applying ac voltage to the piezoelectric element generates a pilot tone, which is used to monitor the bias point of the modulator, while applying dc tunes the modulator to quadrature. The method separates the biasing and RF modulation of the device, thus avoiding the need for external biasing components and eliminating electrical bias drift     

Optical pulse generation using guided-wave electrooptic modulator with resonant electrodes and polarization reversal

This paper reports on optical pulse generation using a new guided-wave electrooptic (EO) phase modulator with long resonant electrodes and polarization reversal. Adopting polarization-reversal structure to a guided-wave EO modulator with long standing-wave resonant electrodes, high-efficiency optical modulation is obtained by the compensation of the transit-time effect. By operating a fabricated EO phase modulator with a large amplitude modulation signal, optical sidebands over 100 GHz were obtained. Furthermore, optical pulse trains of an /spl sim/ 25-ps pulsewidth and a 15.28-GHz repetition frequency were successfully obtained by controlling the generated optical sidebands by use of an optical synthesizer.     

High-contrast electron-transfer GaAs-AlGaAs multiple-quantum-well waveguide modulator

The development of a GaAs-AlGaAs multiple quantum well electron transfer waveguide modulator is reported. On-off ratios as high as 75:1 are obtained at 864.5 nm of an applied voltage of -5 to 10 V. It is shown that the wavelength and voltage characteristics of the device can be successfully interpreted in terms of the calculated energy band diagram.<>     

16-arrayed electrooptic polymer modulator

A 16-arrayed polymeric optical modulator is fabricated using an electrooptic (EO) polymer with a large EO coefficient and good thermal stability. The 16-arrayed modulator has lumped-type electrodes with a response time of less than 1 ns. The 16-arrayed modulator has good uniform modulation characteristics between the individual modulators. The deviation of half-wave voltages is 0.2 V and that of insertion losses about 1 dB. Crosstalks range from -28 to -36 dB and extinction ratios are more than 21 dB.     

A high-frequency GaAs optical guided-wave electrooptic interferometric modulator

The characteristics and frequency response of a GaAs monolithic guided-wave interferometric modulator operating at 1.3 μm are presented. The interfetometer consists of three-guide coupler input and output sections and single-mode p+-n--n+ slab-coupled rib-waveguide active arms. The measured electrical bandwidth of an interferometer with 2 mm long active arms was 2.2 GHz and limited by parasitics. This corresponds to a small signal optical bandwidth of ≈ 3.0 GHz when the interferometer is biased in a linear portion of the optical output versus voltage characteristics. Reduction of parasitics should result in a substantial increase in the bandwidth of these devices.     

非线性液晶聚合物电光调制器

文章描述了透明非线性液晶聚合物的合成，准直和非线性光学性质，给出了液晶事物电光调制器的制作和测试方法及应用。     

Extinction ratio of electrooptic light modulator

The dependence of the extinction ratio on the angle of inclination between the end surfaces of electrooptic crystals with natural birefringence and on the light spot size is described in the electrooptic light modulators.     

PLZT film waveguide Mach-Zehnder electrooptic modulator

We report the numerical analysis and the fabrication of a reversed-ridge PLZT film waveguide. It is single-mode, has low transmission loss, and has large transverse cross-section suitable for efficient coupling to single-mode optical fibers. We used this structure to fabricate Mach-Zehnder (MZ) waveguide modulators. The field distribution in the channel and Y branch waveguides was calculated using a beam propagation method to analyze the modal profiles and the propagation loss. The reversed-ridge waveguides and the MZ structures were fabricated on r-sapphire substrates with a patterned ITO spacer film by sol-gel deposition. At 1.55 μm the propagation loss was 2.7 dB/cm. In the MZ, the half-wave modulation voltage was 8.5 V using 1.55 μm light and electrode length of 3.5 mm     

A novel, wideband, lithium niobate electrooptic modulator

A set of floating electrodes and a relatively thick buffer layer of low-dielectric constant is interspaced between the coplanar RF transmission line and the LiNbO₃ substrate containing the optical wave-guide structure. The composite structure is designed to feature a 50-Ω characteristic impedance, to have an effective dielectric constant equal to that of the optical wave for close velocity match, and to have a 3 dB bandwidth of 40 GHz. The purpose of the floating electrodes is to optimize the modulation sensitivity resulting in an improvement of about 6 dB. As a result, the RF power required for full modulation is lower than heretofore reported changing over the range from below 2 GHz to 20 GHz, from 44 mW to less than 70 mW. The close agreement between the theoretical and experimental values of the design parameters demonstrates the usefulness of the quasistatic assumption in the analysis of the composite structure     

Integrated optic electrooptic modulator electrode analysis

Integrated optical (IO) switches and modulators are based on the electrooptic effect obtained by applying a voltage between electrodes fabricated on the surface of a crystal (for example, LiNbO3). In this paper, we calculate the change in the optical propagation constant in single modeZ-cut LiNbO3:Ti-diffused waveguides for a variety of electrode configurations. These calculations are compared to experimental data from IO devices. The calculations predict the observed variations in switching voltage with wavelength and electrode separation.     

A novel photodetector frequency response measurement techniqueusing an electrooptic modulator

Photodetector frequency response has been measured using an electrooptic modulator in a manner that does not require knowledge of the modulator frequency response. This paper discusses the theory and experimental results for the method and compares them to those obtained by using broadband noise from an optical amplifier     

0 to 3 GHz traveling-wave electrooptic modulator

A report is given on the construction and testing of a traveling-wave electrooptic modulator that requires a nominal 5-watt drive power to obtain 30 percent amplitude modulation from 0 to 3-GHz. The modulator employs potassium-dihydrogen-arsenate crystals and has been tested at 6328 Å with CW drive power.     

Optical circular-polarization modulator employing tilt-poled electrooptic polymers

A polymer-based integrated circular-polarization modulator (CPM) is demonstrated in this paper. Tilted poling is adopted to achieve polarization conversion in the electrooptic (EO) polymeric waveguide and then realize the power balance between transverse electric and transverse magnetic modes. Detailed analysis and experiments on polarization conversion are presented. The tensor nature of poled polymeric materials is used to generate the phase difference. Contact poling is applied to perform tilted poling and activate the EO effect of polymeric materials. With appropriate voltage control, the polarization state of the output from the CPM can alternate between the left and right-hand-circular states. The extinction ratios at the 45/spl deg/- and -45/spl deg/-tilted linearly polarized states are larger than 25 dB.     

Broad-band linearization of a Mach-Zehnder electrooptic modulator

Analog optical-link dynamic range in excess of 75 dB in a 1-MHz band has been achieved using specially designed electrooptic modulators that minimize one or more orders of harmonic and intermodulation distortion. To date, however, such “linearized” modulators have only enabled improved link dynamic ranges at frequencies below 1 GHz. Additionally, linearization across more than an octave bandwidth has required precise balancing of the signal voltage levels on multiple electrodes in a custom modulator, which represents a significant implementation challenge. In this paper, a link linearization technique that uses a standard Mach-Zehnder lithium-niobate modulator with only one RF and one dc-bias electrode to achieve broad-band linearization is discussed, resulting in a dynamic range of 74 dB in 1 MHz across greater than an octave bandwidth (800-2500 MHz). Instead of balancing the voltages on two RF electrodes, the modulator in this new link architecture simultaneously modulates optical carriers at two wavelengths, and it is the ratio of these optical carrier powers that is adjusted for optimum distortion canceling. The paper concludes by describing a second analogous link architecture in which it is the ratio of optical power at two modulated polarizations that is adjusted in order to achieve broad-band linearization