Minimisation of Parasitic Capacitance in Lumped-Element Electro-Absorption Modulators for High-Speed Optical Components (original) (raw)
Photonics
This paper presents an investigation into the parasitic capacitance of an RF contact scheme for lumped-element EAMs. Test structures are fabricated to analyse this parasitic capacitance via S11 characterisation using a vector network analyser (VNA). Optimisations of the contact scheme lead to the parasitic capacitance being reduced to <10 fF. EAMs using this contact scheme are fabricated and characterised using S11 measurements. These S11 measurements are used to simulate S21 measurements, which predict a f3dB bandwidth of near 80 GHz using an equivalent circuit model.
Related papers
Optics express, 2012
Standing wave effect of applied electrical field on optical modulation in multiple-cascaded integration (CI) electroabsorption modulator (EAM) and high-impedance transmission line (HITL) has been investigated in this paper. As modulation frequency is increased to the scale that electrical wavelength is in the order of optical modulator length, multiple electrical reflection and self-interference on impedance-mismatch boundaries becomes significant, leading to strong position-dependent field distribution and degrading modulation bandwidth. Sharp bandwidth roll of electrical-optical (EO) conversion by standing wave has been found experimentally in CI structure, consistent with simulation results. By comparing different segment number and length of CI- structure, larger section number of design can overcome such problem to get more flatten bandwidth response. Such simple CI for 300μm long EAM has been demonstrated with flat EO response of -3dB drop 45GHz and -10dB microwave reflection ...
Analysis of a GaAs/AlGaAs electrooptic modulator for high-speed communications
2010
An analysis of a GaAs/AlGaAs electrooptic intensity modulator is carried out by using the finite element method. The microwave properties, e.g., the effective index, the characteristic impedance, and the frequency dependent attenuations are calculated using quasi-TEM analysis. The 3-dB optical bandwidth is estimated and it is shown that microwave losses in the dielectric material is an important factor in determining the bandwidth of the modulator. Next, to carry out the optical analysis, electrooptic effect is considered and optical mode fields and half-wavelength voltage length product is calculated using a vectorial finite element method. The results are compared with the published results and very good agreements have been found.
High-Speed Electro-Optic Modulator Design Considerations
2011
Designers of electro-optic modulators and related devices often use separate tools to study the optical and electrical portions of the device. The flexibility of Comsol Multiphysics makes it possible to construct unified models of EO phenomena including realistic waveguide profiles and anisotropic material properties. We demonstrate the use of the RF Module to compute both RF and optical waveguide modes and calculate the velocity mismatch and overlap efficiency between them. Realistic index profiles for diffused waveguides are computed using the Transport of Diluted Species physics mode with anisotropic diffusion coefficients.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.