Resonance Suppression of Grounded Coplanar Waveguide in Submount for 40 Gb/s Optoelectronic Modules

Abstract

It is a key issue in optoelectronic modules to feed high-frequency microwave signals to device chips with low loss and reflection. In our work, microwave resonances in frequency response of 40 Gb/s optoelectronic modules are suppressed through theoretical and experimental optimization. Such resonances due to microstrip-like modes of grounded coplanar waveguide (GCPW) severely degrade the performance of optoelectronic devices. The resonances can be suppressed by introducing metal-walled via holes in GCPW submount. The diameter and the spacing of the via holes are optimized to be 0.2 mm and 0.8 mm, respectively. An electroabsorption modulated laser (EML) module with over 30 GHz modulation bandwidth has been demonstrated without obvious high frequency resonances.

A New Equivalent Circuit Scheme for Grounded Back-to-Back GCPW-MS-GCPW Transitions Fabricated on a Thin Low-K Substrate

“…Notably, Monolithic Microwave Integrated Circuits (MMICs) focus interest in reducing their footprint and increasing their operation bandwidth by adjusting the embedded transmission lines and transitions. Bandwidth optimization of many transitions has already been explored on thick film substrates [2][3][4]. It results in the integration of multiple via-holes along the transitions to reduce losses and improve mode conversion.…”

Ultra-broad bandwidth and low-loss GCPW-MS transitions on low-k substrates

“…According to the chosen type of technology, a portion of parallel plate waveguides can then create the possibility of parasitic resonances, which reduce the bandwidth of the circuits [5 -7]. Via-holes could eliminate some resonance peaks if they are appropriately located but this operation takes time and is expensive to do [6]. Instead of using via-holes to eliminate parasitic resonance, we show that, with thin low-k substrate on LRS wafers, one can realise cost-effective, low-loss and ultra-broad bandwidth GCPW-MS transitions by increasing the parasitic resonance frequencies.…”