Silicon-based optoelectronic switches and modulators at 1.3 and 1.55-um fiber-optic communications-wavelengths for fiber-to-home interconnects and local area networks (LAN) offer the possibility of integrating optical elements and advanced electronics on a silicon substrate using bipolar or complementary metal-oxide semiconductor (CMOS) technology. Most of the proposed Si electro-optic (E-O) switches, however, require long interaction distance and high drive powers for obtaining a significant modulation depth. Long interaction lengths are undesirable in order to achieve high levels of integration and miniaturization. High electrical powers may induce competing thermo-optic effects.
The PI proposes a new class of micrometer-size planar Si electro-optic switches with low power consumption and high modulation depth.
The device is based on a planar Fabry-Perot (F-P) microcavity. Free-carrier plasma dispersion effect [1,2] is used to modulate the refractive index of the cavity region by using a lateral p-i-n diode. Both optical field and injected carriers are strongly confined in the microcavity using high-index-contrast Si/SiO2 distributed Bragg reflectors (DBR) and trench isolation. The optical confinement accounts for the small size of the structure and its high modulation depth. The carrier confinement accounts for the device low power consumption.
The PIs preliminary calculations show that a 20-micron long device can have 80% modulation depth under 25 microwatt power drives. To the best of their knowledge this corresponds to the first practical Si integrated photonic active device.
This new class of active devices will function as a building block for active on-chip Si devices. These devices include tunable filters, tunable grating, modulators, switches, adaptive couplers among others. All-optical systems on a chip could become a reality where inexpensive, compact active and passive devices could be integrated and monolithically grown on a chip.
