No abstract

The field effect in metal-oxide-semiconductor (MOS) capacitors plays a key role in field-effect transistors (FETs), which are the fundamental building blocks of modern digital integrated circuits. Recent works show that the field effect can also be used to make optical/plasmonic modulators. In this paper, we report field effect electro-absorption modulators (FEOMs) each made of an ultrathin epsilonnear-zero (ENZ) film, as the active material, sandwiched in a silicon or plasmonic waveguide. Without a bias, the ENZ film maximizes the attenuation of the waveguides and the modulators work at the OFF state; contrariwise, depletion of the carriers in the ENZ film greatly reduces the attenuation and the modulators work at the ON state. The double capacitor gating scheme is used to enhance the modulation by the field effect. According to our simulation, extinction ratio up to 3.44 dB can be achieved in a 500-nm long Si waveguide with insertion loss only 0.71 dB (85.0%); extinction ratio up to 7.86 dB can be achieved in a 200-nm long plasmonic waveguide with insertion loss 1.11 dB (77.5%). The proposed modulators may find important applications in future on-chip or chip-to-chip optical interconnection.

Most dielectric materials have very weak electro-optic properties, whereas the optical properties of some plasmonic materials may be greatly tuned, especially around their plasma frequency, where dielectric constant is transiting between positive (“dielectric state”) and negative (“metallic state”) values. In this talk, we will review some of our recent work on electro-optical modulation and introduce a new concept, photonic MOS based on “optical property inversion”. This concept may provide inspiration for the development of nanophotonic devices. While the whole paper only discusses theory and modelling, some new experimental results will be presented in the on-site talk. Throughout this report, “static dielectric constant”,ɛ, refers to material dielectric constant in the DC or radio frequency (RF) regime; “optical dielectric constant”,ε, represents material dielectric constant in the near-infrared regime. This paper was re-written based on an Arxiv file [1].

An electro-optic modulator operating at visible wavelengths is demonstrated with TFLNOI (Thin Film Lithium Niobate on Insulator) flip-chip bonded on a foundry fabricated SiN (Silicon Nitride) photonic integrated chip, achieving a π phase shift with VπL = 7.5V.