Broadband loss characterization of traveling-wave substrate integrated electro-optical devices

In this paper, broadband including microwave and millimeter-wave (mmW) characteristics of conventional optoelectronic devices with emphasis on waveguide photodetector (WGPD), traveling-wave (TW) photodetector and modulator are compared with our newly proposed substrate integrated electro-optical devices. In the newly proposed devices, substrate integrated circuit (SIC) concept is applied to the design of conventional TW photodetectors and modulator to realize a new SIC-based optoelectronic device configuration expected with high operation frequency and bandwidth. Microwave and mmW losses are one of the important bandwidth limitations for the microwave and mmW photonic devices. Different sources of loss including ohmic, dielectric and radiation losses in microstrip (MS) and coplanar waveguide (CPW) of the conventional type and substrate integrated waveguide (SIW) based electro-optical devices are analyzed and compared. Isotropic and anisotropic substrates are used for the loss analysis. The results show that the total microwave loss, which increases against frequency in the conventional MS and CPW waveguides, can be made almost constant in SIC-based devices. In addition, to demonstrate the SIC concept suitable for electro-optical devices, microwave part of SIW-photodetector and SIW-modulator are fabricated and the results obtained from measurement and simulation are compared.