Resonator-enhanced low power all-optical switch with a nonlinear ratio-variable coupler

One of the major challenges in realizing practical all-optical switching devices is the need for strong and fast material nonlinearity. The use of resonance-enhanced nonlinear effects in optical cavities has been explored as a promising way to lower the switching power. This paper provides numerically investigation of resonator-enhanced Mach-Zehnder interferometer all-optical switch by employing a nonlinear ratio-variable coupler with the merits of easy fabrication and excellent nonlinear optical controllability. This performs nonlinear optical switching with advantages of hundreds μW low switching threshold, steady switch ON/OFF states and a wide wavelength range by combining the high nonlinearity of ring and adjustable coupling ratio of RVC. Resonator finesse is controllable by incident power with potential applications in controllable photonic devices. Some undesirable effects involving attenuation, group delay and partial coherence lead to increase of switching power and low extinction ratio. Optical bistability and instability do not limit practical applications in optical switch. A desired tradeoff between response time and switching power can be achieved by controlling finesse. Picosecond ultrafast all-optical switch is predicted.