Silicon ring resonator electro-optical modulator utilizing epsilon-near-zero characteristics of indium tin oxide

Abstract

One crucial component in optical communication systems is the optical modulator. It links between the electric and optical domains as it transforms the electric signal into an optical stream. Electro-optical modulation is a very popular scheme. Recently, indium tin oxide (ITO) has been intensively used in optical modulators due to its epsilon-near-zero characteristics. A silicon electro-optic ring resonator modulator is proposed in terms of the outspread application of ITO. An extinction ratio of about 14 dB as well as an insertion loss of 0.075 dB are achieved at a standard telecommunication wavelength of 1.55 microns. The design has low losses, high efficiency, and compact size.

Design of low power silicon electro optic modulators based on hybrid plasmonic ring resonator

“…The bandwidth of the ITO based ring resonator modulators is limited due to the large interface between the silicon waveguide and ITO/HfO 2 in the ring, which causes the high capacitance [20]. The proposed structure in this paper seeks to reduce the silicon and ITO/HfO 2 interface in the ring to improve speed and other characteristics such as quality factor, ER, and low IL.…”

“…The Drude-Lorentz model is used to describe the permittivity of ITO [20,37,48]. The real part of permittivity decreases, and the imaginary part increases as the voltage increases.…”

“…According to equation (4), a modulation speed of 57.3 GHz is obtained. Power consumption per bit is 147 fJ bit −1 , lower than the similar structure [20]. According to equation (5), the modulation depth is 0.57 dB μm −1 .…”

“…Resonant-based structures [12,16] and plasmonic-based structures [17,18] are designed to improve the performance of optical modulators. Optical modulators based on ring resonator structure [19][20][21] have the potential to reduce the size of silicon-based modulators because light passes through the ring waveguide several times, increasing the light-matter interaction compared to other structures such as Mach-Zehnder Interferometer (MZI) modulator [22][23][24]. The mechanism of the ring resonator modulator is based on changes in the refractive index of the ring waveguide, which changes the resonance conditions [25][26][27].…”

“…Where R is an internal impedance and assumed to be 50 Ω [37,50], A is the cross-sectional area between the Si waveguide and ITO/HfO 2 and is equal to = p A 2 rh Thus, the modulation speed is 81.82 GHz, which has improved compared to [20]. Power consumption per bit is obtained from the equation = E bit CV 2 3.…”