Abstract
Silica-based photonic integrated circuits (PICs) have been making major advances and are finding increasing applications in optical communications, networking, and signal processing. For the next generation of photonic integrated circuits, it is desirable to add more functionality as well as to increase the integration level. This would involve introducing a variety of heterogenous materials and devices on the same substrates, using a monolithic and/or hybrid integration method. In this paper we describe the results of our efforts of developing/incorporating new functions to the silica-based integrated circuits. 1) Optical amplifiers, suitable for monolithic integration with other guided-optic devices, are promising as loss-compensating devices for photonic integrated circuits. 2) Silicon is the most commonly used substrate for silica-based PICs. A novel method has been developed for forming 2D waveguides on silicon substrates, utilizing the photoelastic effect in Si induced by thin-film stress. This method does not require any separate guiding layer nor etching of silicon, and therefore is expected to increase the flexibility in designing/implementing advanced PICs on Si. 3) Ferroelectric materials possess various functional properties and are expected to play an important role in advanced PICs. The major challenges and progress are discussed in achieving monolithic integration of functional films, such as PZT, on silica and Si substrates.