Technical Papers and Presentations

On-chip photonic modulators designs currently use NLO material stacks such as LiNbO3 or BaTiO3 on Si or use current injection across silicon waveguides to induce phase change required for optical modulation(Li 2020)(Li 2019). The other silicon compatible option explored is silicon-slotted waveguides with organic NLO material filling the slots add. Here, the main limiting factors are the photostability, thermal stability and low transition temperatures (Tg) of the organic materials and fixed wavelength of operation due to waveguide design. There have been constant efforts to evolve chromophores with higher NLO activity and higher Tg. Recently reported chromophore (HLD) marketed by Nonlinear Material Corporation can be operated at temperatures of up to 1500 C and is compatible with CMOS technology. HLD is reported to give large Pockel effect with a high r33 of 290pm/V, a Tg of 1500C with refractive index in the range of 1.83-1.85. Hence, as figure of merit is high the required voltage levels to induce effective refractive index change is very low.HLD can be spin coated or grown in-situ from powder (without host polymer) and the process will be CMOS compatible. This work discusses the design of a Si waveguide modulator incorporating a set of 1 D Bragg filters using 3 Si-HLD bilayers with a central Si defect region forming a wavelength selective Fabry Perot cavity as shown in Fig1(a). On application of voltage to the electrodes on either side of the waveguide, the Pockel effect induced index change of the HLD in the Bragg filter will selectively transmit one wavelength in the C-L band. The device design dimensions have been optimised such that when no voltage is applied the device does not transmit any wavelength in the 1530-1570nm region. So that a bit voltage of 0 corresponds to zero optical output. Desired wavelength of transmission can be varied by applying appropriate voltage at the electrodes. If the RF signal is applied to the electrodes, the device will give optical output whenever the bit is high, but the voltage level corresponding to the high bit variation will also select one wavelength. So, if a low-cost broadband super luminescent LED is used as a source, a high voltage in the range of 0.3 to 1V can select wavelengths within this band (Refer Fig1b).The high fs response time of HLD ensures that which is capable of 100s of GHz modulation. By modifying the design, this work can be extended to different materials that can provide gain and act as a on chip amplifier. The Wave Optics> Electromagnetic Waves and AC/DC > Electrostatics modules in COMSOL Multiphysics® are used for the simulation and modelling of optical phase modulation under the influence of applied electric fields. For the electrodes perfect electric conductor boundary condition is used.