Electro-optical impedance

Photocurrent with subband light to provide information on surface states" Optoelectric impedance (photopotential or current response to modulated illumination) or electro-optic impedance (photoresponse to potential modulation) for information on the contribution of minority, majority, and injected carriers in recombination and multiplication ... 

C. Gabrielli, M. Keddam, H. Perrot, and R. Torresi [1994] Lithium Insertion in WO3 Studied by Simultaneous Measurements of Impedance, Electrogravimetric and Electro-Optical Transfer Functions. J. Electroanal. Chem. 378, 85-92. 

For a low-frequency, Mach-Zehnder modulator, the impedance is dominated by the electrode capacitance and resistance as shown in Fig. 9.57. A Smith chart plot for a MZM is shown in Fig. 9.58. Unlike the laser diode, a modulator on lithium niobate has no junctions consequently the impedance is independent of modulator bias. As was the case with the diode laser, it is often important to match the modulator impedance to the system impedance, typically 50 or 75 real. However, unlike the diode laser, modulators fabricated in electro-optic materials that are also piezoelectric can have perturbations in their impedance due to coupling of some of the modulation signal into compressional waves. The coupling can be significant at frequencies where the modulator crystal is resonant. The dashed curve in Fig. 9.58 shows an acoustic resonance at 150 MHz. A number of techniques (Betts, Ray and Johnson, 1990) have been developed to suppress these acoustic modes to insignificant levels, as is evidenced by the solid curve in Fig. 9.56. 

Fig. 20.29 (a) Equivalent circuit and (b) the electro-optical complex plane plot for a polypyrrole/polystyrenesulfonate composite film. Zd is a charge transport impedance within the polymer film (modeled as a transmission line circuit). ( ) Electrical data ( ) optical data. AE is the applied ac potential, and the total charge zlU is divided into doublelayer charging (A d) and Faradaic A Q ) components. (Reproduced with permission from Ref. 144.)... 

Followed by the invention of liquid crystal electro-optic effect by the RCA Corporation in the United States in 1962, the invention of the twisted nematic (TN)-type liquid crystal display by Hoffmarm-La Roche in Switzerland in 1970, and the development of the integrated circuit (IC), the global race to develop electronic calculators and watches started. As the impedance matching is good between LCDs and ICs, an LCD can be driven directly from the IC with a button battery, combining the advantages of compactness with low power consumption. 

---