Moving toward optoelectronic logic circuits for visible light: a chalcogenide glass single-mode single-polarization optical waveguide switch
In this paper, we propose an arsenic trisulfide (As-S) optical waveguide switch-based logic gate mainly comprised of a photorefractive Sn1As20S79 waveguide core and a LiNbO3 crystal substrate. In combination with the unique optical stopping effect of Sn1As20S79, this device can realize logical operations on an electrical signal and an optical signal, holding promises to be applied in optoelectronic logic circuits. While most of the previous research on As-S has focused on applications in the infrared regime, this device operates at the visible wavelengths of 632.8 and 441.6 nm, which are the specific wavelengths for optical stopping. As the kernel part of this logic gate, an optical waveguide switch based on an electro-optic coupler is employed to control optical signals by electrical signals, providing a solid foundation of operation for an electro-optic logic function. Some crucial design specifications of the switch are optimized by means of simulation analysis. It is found that less than 10 V of applied voltage is sufficient to realize a satisfactory function of the switch. A coupling efficiency of 90% and an extinction ratio of greater than 10 dB are achieved by simulating the lightwave propagation in the waveguide switch. Since the waveguide structure of the switch has no upper cladding, it is different from that of a ridge waveguide or a buried waveguide, and is, thus, convenient to fabricate by only using UV exposure without etching. Our work will open new possibilities for photoelectric hybrid logical operation in visible light, and, thus, provide fertile ground for applications in programmable optical chips.