A Mach-Zehnder interferometer electro-optic switch with ultralow voltage-length product using poled-polymer/silicon slot waveguide

Abstract

By using poled-polymer/silicon slot waveguides in the active region and the Pockels effect of the poled-polymer, we propose a kind of Mach-Zehnder interferometer (MZI) electro-optic (EO) switch operated at 1 550 nm. Structural parameters are optimized for realizing normal switching function. Dependencies of switching characteristics on the slot waveguide parameters are investigated. For the silicon strip with dimension of 170 nm×300 nm, as the slot width varies from 50 nm to 100 nm, the switching voltage can be as low as 1.0 V with active region length of only 0.17-0.35 mm, and the length of the whole device is only about 770-950 µm. The voltage-length product of this switching structure is only 0.17-0.35 V·mm, and it is at least 19-40 times smaller than that of the traditional polymer MZI EO switch, which is 6.69 V·mm. Compared with our previously reported MZI EO switches, this switch exhibits some superior characteristics, including low switching voltage, compact device size and small wavelength dependency.In recent years, optical switching devices have received more and more attention due to their wide applications in optical communication and optical signal processing systems. In our previous reports, based on rib/rectangular waveguides and the poled polymer AJ309 [1,2] , different non-resonant electro-optic (EO) switches have been numerically proposed, and they usually exhibit a switching voltage of 2-5 V and an EO region length of 3-6 mm, which indicates a voltage-length product of 5-30 V·mm [3][4][5] . For a lower EO coefficient, a long active region is required to drop the switching voltage below 1 V, but this will lead to long waveguide length, which is not allowed in low-voltage, ultra-compact and chip-level interconnection. Besides polymer EO switches, silicon EO switches also have shown great potential for being compatible with standard complementary metal-oxide-semiconductor (CMOS) processing technology. So far, silicon EO switches have been widely demonstrated based on free carrier depletion [6][7][8] or injection [9,10] in diode structures or CMOS structures [11] . To meet the needs of optical communication, an optical switch should possess some important characteristics, involving small device dimension, suitable electrical and optical bandwidth, large voltagelength product, high extinction ratio and low power consumption.Compared with other waveguide structures, such as rib waveguide and rectangular waveguide, the slot waveguide has been proven to be a good candidate to design and fabricate integrated optical devices. In this paper, we propose a kind of Mach-Zehnder interferometer (MZI) EO switch operated at 1 550 nm by using poled-polymer/ silicon slot waveguides in the active region and silicon waveguides in the passive region, and the Pockels effect is exploited via the poled-polymer cladding in the slot waveguide. Through optimization, the device can perform normal switching functions. An impressive advantage of this structure is that its voltage-length product is reduced by at least 19-40 ti...