Design of a Surface-Illuminated-Type Semiconductor Optical Modulator with Multi-Quantum-Well Structures

A surface-transmission-type semiconductor optical modulator using multi-quantum-well structures is designed. In order to realize a high extinction ratio and a low insertion loss with a lower driving voltage, a structure is proposed in which the voltage is applied in the transverse direction of the quantum well by means of comb-shaped conductive layers. The thickness of each layer is discussed. As an example of theoretical design with optimum conditions, a device structure realizing an extinction ratio between 10 and 20 dB and an insertion loss of 2 dB at a driving voltage of 5 V is presented. A high operating speed, up to several gigahertz, can be expected in a device with a surface area of 20 × 20 μm2. © 2000 Scripta Technica.