30-Gbps Directly Modulated Semiconductor Lasers Based on Surface High-Order Gratings

Semiconductor lasers with surface high-order gratings have been fabricated and measured. $31^{\mathrm {st}}$ -order gratings were defined by the standard contact-type i-line photolithography near the front facet and subsequently etched into the ridges of the semiconductor lasers by the inductively coupled plasma. Both the static and dynamic characteristics were investigated. The threshold current and maximum output power are 22 mA and 12 mW, respectively. Side-mode suppression ratios are larger than 35 dB at bias currents except approximately 145 mA due to mode hopping. −3 dB bandwidth of the small signal response is 13.8 GHz at 130 mA. The eye diagram at a bit rate of 30 Gbps is clearly open.