Bi-junction carrier depletion type electro-optic phase-shifters

Silicon photonic integrated circuits (PICs) combine dense optical system integration with industrial scalability by adopting well-established CMOS fabrication processes [1]. An electro-optic phaseshifter (EOP) represents a basic building unit of several PICs applications [1], including datacom optical switches [3], PIC-FPGAs [4], and beam steering [5]. In-situ resistive-heaters in close vicinity of waveguides [2], or free-carrier injection/depletion in doped junctions [3], are common methods to build EOPs. Literature reports thermal shifters consuming 24.7 mW to achieve DC large signal π-phaseshift [2], power consumption of injection PIN implementations [5] and depletion PN modulators [6] of 10 mW and ≈ 0 mW respectively. A thermal EOP naturally avoids carrier-induced optical insertion losses (IL), in contrast to a PIN/PN modulator. Thus, thermal and PIN/PN methods trade-off IL with electrical power rather than minimizing both [2,3]. An EOP of low optical losses and low electrical power is highly desired in large-signal, and low-speed applications [5, 7].