Chapter 11: Electro-optic modulators and photodiodes

The requirements for electro-optic modulators and photodiodes for advanced interferometric gravitational-wave detectors are very specialized. Commercially, available devices are usually not suitable for those detectors. In this chapter we give an overview of the aspects that need to be considered when building custom devices. We will show the characteristics of electro-optic modulators, and how they are used to create modulation sidebands and can be designed to satisfy the strict detector requirements. We also show how unwanted modulation effects can be avoided. Several electro-optic modulator-specific applications in gravitational-wave detectors will be addressed. In the second part of the paper we will show the characteristics of photodetectors, inherent and external noise sources, and how basic low noise photodetector circuits can be used to address the strict requirements of advanced gravitational-wave detectors.