During the last two decades, lithium niobate has been extensively studied for applications in integrated optical circuits. However, it is difficult to integrate lithium niobate optical devices with semiconductor electronic devices because of incompatibility of the materials. In recent years, semiconductor materials are emerging as the main contender in applications; these materials have the advantage that both the optical and electronic devices can be integrated. Further, the semiconductor technology has advanced rapidly allowing us to engineer device parameters very precisely. In semiconductor opto-electronic devices, i.e. bulk and quantum well structures, mainly electro-absorption has been used for amplitude modulation of light. The electro-refraction effect is most useful for devices employing phase modulation techniques but this effect cannot be effectively utilized in semiconductors since the strongest electro-refraction effect is near the absorption edge of the material. Recently, organic materials have been shown to have electro-optic coefficients of equal or larger than that of lithium niobate. There are major advantages of organic materials: (a) the organics can be deposited on semiconductor substrates and therefore both electronic and optical circuits can be integrated (b) in organic materials the electro-refraction can be effectively utilized to obtain both amplitude and phase modulation (c) the organic material composition can be adjusted to satisfy some device requirements. In this paper, a comparison of these material systems will be made in terms of device applications.
L. M Walpita,
"Organic Materials In Future Integrated Opto-Electronic Circuits", Proc. SPIE 1177, Integrated Optics and Optoelectronics, (5 January 1990); doi: 10.1117/12.963319; https://doi.org/10.1117/12.963319