Broadband, Integrated, Micron-Scale, All-Optical Si3N4/VO2 Modulators with pJ Switching Energy

Abstract

This document provides supplementary information to Broadband, Integrated, Micron-Scale, All-Optical Si 3 N 4 /VO 2 Modulators with pJ Switching Energy, ACS Photonics volume, rst page (year). First, the optical modes of the Si 3 N 4 /VO 2 waveguide modulator and their properties are given. Next, the details of the fabrication process and characterization of the all-optical modulator are provided. The remaining sections of the document elaborates on the measurements and subsequent calculations of 1 modulator insertion loss, switching energy, and the threshold uence for the insulatorto-metal transition in vanadium dioxide, as well as a comparison of our demonstrated device to previous work.Si 3 N 4 /VO 2 Modulator Modes and PropertiesThe wavelength-dependent refractive index n of vanadium dioxide (VO 2 ) is determined from ellipsometry of the deposited polycrystalline lm on a planar substrate; at λ = 1550 nm, the dielectric state refractive index is n d = 2.861 + 0.267i, and the metallic state value is n m = 1.664 + 3.291i. In comparison to previous published values, 1,2 both Re{n d } and Re{n m } from our data are ∼0.3 lower, while Im{n d } is lower but Im{n m } is higher. Although the waveguide is multi-moded at λ = 1550 nm, only the even modes are considered, as a carefully centered Gaussian beam excites only even modes. 3 Details of the modes of the Si 3 N 4 /VO 2 waveguide at the signal wavelength of λ = 1550 nm when VO 2 is in its dielectric state are given in Fig. 1. Here, we choose to utilize the predominantly transverse magnetic (TM) mode, because both a lower IL = 0.20 dB/µm (modal loss when VO 2 is dielectric) and higher ER = 3.04 dB/µm (dierence in modal losses between when VO 2 is metallic and dielectric) are attained compared to the transverse electric (TE) mode. Dierent Si 3 N 4 waveguide dimensions (e.g., w and h) have been scanned in the optimization for the extinction ratio (ER) and insertion loss (IL) in order to come up with the current design. The wavelength

TiN-GST-TiN all-optical reflection modulator for the 2 µm wave band reaching 85% efficiency

“…They reported 18.7 dB extinction ratio and 4.15 dB insertion loss, with 0.9 µm modulator length. HMK wong et al [62] experimentally demonstrated an ultracompact (4 µm modulator length) all-optical modulator, with 1.68 dB/µm and 0.98 dB/µm extinction ratio and insertion loss respectively. They used VO 2 as the active layer and achieved the FOM of 1.71.…”

Hybrid Si3N4/electro-optic polymer waveguide Mach-Zehnder interferometer for high-speed electro-optic switching

“…Silicon nitride (Si3N4) is one of the most significant waveguide materials in silicon photonics, owing to its advantages of CMOS-compatibility, large optical band gap, moderate refractive index, and lower transmission loss and larger fabrication tolerance than silicon. [1][2][3][4][5][6] Si3N4-based optical switches have important applications in optical cross connect (OXC), optical add-drop multiplexing (OADM), high-speed filter for DWDM and optical phase array for high-speed beam steering. [7][8][9] However, Si3N4 materials have a centro-symmetric structure and do not have EO effect, so they cannot be switched by EO modulation.…”

All-Optical Hybrid VO$_{2}$/Si Waveguide Absorption Switch at Telecommunication Wavelengths

“…Besides electrical triggering, optical excitation has been widely employed to investigate the VO 2 phase transition on thin-film structures and ultra-fast switching times as fast as femtoseconds have been achieved [7], [28], [31]- [36]. More recently, experimental demonstration of all-optical VO 2waveguide devices have been reported [26]- [28], [37]. However, experiments were carried out in a similar way to those focusing on the process behind the photo-induced phase transition of VO 2 using free-space pump-probe studies.…”

“…Conversely, in a waveguide approach, similar switching energies can only be achieved by increasing the power in order to compensate: (i) the exponential attenuation that suffers the light through the hybrid waveguide; and (ii) the low fraction of optical mode that interacts with the VO 2 . In [37], Wong et al obtained switching energies of few picojoules using a SiN waveguide but at the expenses of guiding a high peak power, which is unfeasible in silicon due to nonlinear effects [38]. On the other hand, in out-of-plane configurations, switching times range from few picoseconds to several seconds mainly due to the different optical pumping scheme and device structure.…”