Over 100 GHz High Power Modified-Uni-Travelling-Carrier Photodiodes for Analog Optic Link

Since 1970s when fiber-optics were introduced, they have revolutionized the telecommunications industry. With the development of low loss fiber, fiber optic links have proved to be advantageous over their electronic counterparts (coaxial cables) for a number of applications in terms of low loss, high EMI immunity and large bandwidth. Although digital optic links dominate the fiber optics communications, there are growing interests in analog optic links for applications like RoF wireless communications, phased arrayed antennas, antenna remoting and radio astronomy most of which are for military use. As demand for high speed communication, the carrier frequency has to increase (in mmW range) to accommodate this change. Photonic generation of mmW carrier frequency can provide not only wide tunable carrier frequency range with low phase noise, but also reduce system cost by eliminating the expensive electronic components if an optical to electrical (O/E) converter can handle high enough power. At the same time, in mmW frequency, atmosphere attenuation due to oxygen, water absorption is not trivial, and high output power from the O/E converter is necessitated to compensate the large attenuation in order to provide large coverage for wireless communication. In conclusion, development of high power high speed photodiodes is necessitated for these applications.

In this work, over 100 GHz high power modified uni-travelling-carrier (MUTC) photodiodes for high speed and high power 1.55 µm applications were developed and characterized. Both surface normal photodiode and evanescently-coupled waveguide photodiode are realized with over 100 GHz frequency. To demonstrate the photonic integration capability with my photodiodes, a photonic integration of W-band emitter was realized by flip-chip bonding high power surface normal photodiodes onto a Vivaldi antenna with matching network.