Contents I. Introduction
To meet the ever-increasing demand for data traffic, modulation speed (i.e., Buad rate) exceeds 100 GBaud [1]. High-speed EML is a strong candidate for such high-speed modulation applications along with ring modulators [2], the photon-photon resonance of directly modulated lasers [3], and so on. EMLs are mounted on ceramic substrates, called sub-mount. A peaking circuit consisting of Au wires, a termination resistor, and an RF transmission line enhances the modulation bandwidth. However, as Baud rates increase, it is becoming increasingly challenging to suppress bandwidth degradation and resonance in such a peripheral circuit of the EML. Previous reports revealed that a stepped sub-mount or flip-chip mounting technique of an RF signal line improves EML bandwidth, but there are costly challenges [4], [5]. In this paper, we report a high-speed EML on a cost-effective conventional sub-mount but lateral short RF input avoiding resonance of RF signal pattern.
