Maobin Yi

Large electro-optic effect in sol-gel-processed poled TiO2/SiO2 films doped with organic azo dye

Highly transparent TiO2/SiO2 films prepared using sol-gel technique doped with organic azo dye, Disperse Red 1(DR1) have been investigated. Processing parameters such as spin speed, spin time, and ambient atmosphere, and solution synthesis parameters such as catalysis method, alcohol dilution ratio, and component molar percentages, may affect the film formation. The refractive index increases follow along with the raising of the molar ratio between TiO2 and SiO2. When the molar ratio between TiO2 and SiO2 is zero, i.e. no titania precursor in the initial solution, the refractive index is minimum 1.49 at 1300nm, whereas when there is no TEOS in the initial solution, the refractive index is maximum 1.81 at 1300nm. The sol-gel thin film is spin-coated on ITO glass substrate with better uniformity. The electric-optic coefficient γ33=42pm/V was measured by simple reflection technique at a fundamental wavelength of 1300nm. The hybrid organic-inorganic sol-gel film is well balanced material in its simplicity for film formation, nonlinearity, and thermal stability sufficient for device fabrication. Moreover, the measurement system was calibrated and the measured electric-optic coefficient of the gallium arsenide crystal is in excellent agreement with the known value.

Poling of organic polymer films for external electro-optic measurement

A second-order nonlinear optical polymer was synthesized with bis-phenol-A as the polymer backbone, p-nitroaniline as the chromophore and cinnamyl group as the photo-sensitizer. The polymer films were obtained by spin-coating and poling by three methods respectively. These methods of poling include needle electrode corona poling, parallel wire electrode corona poling and contact poling, which were used to obtain the molecular orientation. The uniformity of the side-chain polymer films have been studied by external electro-optic measurement. The spatial resolution of system is 3 micrometers . Experimental results demonstrated that parallel wire electrode corona poling is easier to obtained large poled area with good uniformity than that of other methods.

Sol-gel-processed TiO2/SiO2 films for electro-optic effect

Sol-gel-processed TiO2/SiO2 films doped with organic azo dye have been investigated. The film was spin-coated on the ITO coated glass substrate and rapidly condensed by evaporation of the solvent from the liquid film. The thickness of the hybrid films can be varied from 0.2 to 0.6 micron. When the prehydrolyzed tetraethoxysilane (TEOS) sol and titania precursor(titanium butoxide) are mixed together with various molar ratios, the refractive index of the film may vary from 1.49 to 1.81 at 1300nm. The film is aged at 80°C for 2 h and then corona poled at 120°C for 1 h so that the dye molecules are dispersed in numerous pores of the oxide matrix. The absorbance spectra of the film measured by a UV-visible spectrophotometer show that the process of aging and poling in the sample preparation causes the pores in the oxide matrix to shrink and nonlinear molecules are aligned in the direction of the poling field and are trapped in the pores. The electro-optic coefficient r33 is 42 pm/V at a fundamental wavelength of 1300nm. The nonlinearity is stable at 80°C for 2500h at least. The excellent thermal stability of the hybrid organic/inorganic film is an advantage for optical applications.

Anomalous Electro-Optic Effect in Polar Liquid Films

We present an anomalous electro-optic effect in polar liquid films: liquids, usually considered to be isotropic, possess the linear electro-optic effect that occurs only in materials lacking inversion symmetry. Due to the observed large effect in the low-frequency range and slow response speed, this strange effect was thought to come from the field-induced orientation of large mass. Therefore, we brought forward a physical model that contributed to the interpretation of this phenomenon: field-induced pre-oriented, short-range orderly dipole clusters in liquid films break the macroscopic symmetry and results in this asymmetric effect. Finally, combined with spectral analysis, the formation of clusters induced by an electric pulse was proved.

The exact validation for measuring the electro-optic coefficients of organic/inorganic hybrid material film

Exact expressions for calculating the electro-optic (EO) coefficients of GaAs and polymer or organic/inorganic hybrid film using simple reflection technique have been deduced. For different approximate conditions, several expressions have been contrasted. After strictly verified, the measuring systems are accurately adjusted, and with the measured data the numerical value of γ33 can be calculated. The measured EO coefficient of GaAs is in excellent agreement with the known value. The organic/inorganic hybrid material is prepared by sol-gel process during which dispersed red 1 (DR1) is doped in tetraethoxysilane (TEOS) as the chromophore with a concentration of approximately 13% by weight. And γ33 of hybrid material over 20pm/V could be easily obtained.

A voltage calibration technique of electro-optic probing for characterization internal to IC’s chip

Abstract This paper simulates the electric potential distribution and the electro-optic (EO) signal amplitude in a longitudinal poled EO polymer external probe tip on the electric signal transmission lines under test. The influence of the circuit layout on the EO probing is discussed. A novel probing configuration with a poled polymer EO probe tip is built and demonstrated for the first time, by which the signal voltage level corresponding to the EO signal can be calibrated. Using the new probe tip, we examine the influence of the variations of the linewidth and the spacing between neighboring lines on the EO signal. The results indicate that when the vertical distance between the tested point on the lines and the reference electrode is not larger than that between the tested point and its neighboring conductor, the disturbance from circuit layout can be avoided so that the voltage calibration of EO signal can be carried out.

Electro-optic probe in low frequency range

The synchronous paragenesis of piezoelectric resonance together with EO modulation, its effect on the electro-optic probing in low frequency range, and a new voltage calibration technique which can utilize the piezoelectric resonance to enhance the voltage sensitivity of EO probing, are reported for the first time.

Electro-optic effect of dye-doped silica thin films

Sol-gel-processed silica films doped with Disperse red 1 (DR1) as well as sol-gel-processed DR1/TiO2/SiO2 films are prepared. The reaction process of sol-gel system is discussed theoretically. The optimal preparation for the dye-doped silica film is investigated as well. The content of catalyzer and the various mol ratio of raw materials in starting solution have influence on the electro-optic performance of the hybrid films. The film was spin-coated on the ITO coated glass substrate and rapidly condensed by evaporation of the solvent. Disperse red 1 (DR1) are doped in the three-dimensional silicon dioxide/titanium dioxide network possessing a high electro-optic coefficient r33. The EO coefficients of the poled DR1/SiO2 films and the poled DR1/TiO2/SiO2 films achieved 65 pm/V and 72 pm/V, respectively. An EO measurement system is fabricated. The hybrid films are spin coated on the low reflection mirror and corona poled after aging in order to induce the nonlinear performance. The EO output signals of the two silica films are detected. The experimental results show that the EO output signals change both amplitude and frequency with the input signal. The nonlinearity of the poled DR1/SiO2 films is relaxed less than 5% after 2000 h at 80°C. The EO coefficient of DR1/TiO2/SiO2 films is relaxed less than 5% after 2500 h at 80°C The excellent thermal stability of the hybrid organic/inorganic film has potential applications in the fields of electro-optics and optoelectronics.

Research of spatial resolution in external electro-optic probing

A new rnethod, based on zero point of longitudinal electric field, was used to deterrnine the spatial resolution of electro-optic (EO) probing systern. To examine the spatial resolution of internal and external EO probing systems, an interdigital structure is fabricated on GaAs substrate with and without a layer of Si02 between the electrode and the substrate respectively. Considering Si02 layer or air gap between electrode and EO crystal, the result of electro-optic probing was simulated which is well accorded with experiment. The result indicates that spatial resolution of less than 0.5um and lum are obtained in internal and external EO probing system respectively.

Microwave packaging of high-speed optoelectronic devices

We use a new impedance graded line that is backland coplanar wave-guide to design transmission line. During the permission of measurement scope on project, we can perform arbitrarily matching for 5(Omega) approximately 75(Omega) , calculated in the method of quasi-static analysis, using the microwave matching network and high-frequency encapsulation, we can improve our work frequency and effective power effectively.