Single-mode Fabry-Perot laser with deeply etched slanted double trenches

This work proposed and demonstrated a single-mode Fabry-Perot (FP) laser structure with a pair of deeply etched slanted trenches inside the cavity. We implemented the proposed mode selection scheme in conventional 1310 nm InAlGaAs/InP strained-layer multiple-quantum-well ridge waveguide FP laser diodes and obtained single-mode operation with a side-mode suppression ratio (SMSR) as high as 35 dB. The single-mode yield was approximately 55%, and other device performance measures such as the threshold and the slope efficiency were not greatly affected. Additionally, temperature cycling and aging tests show no exceptional disadvantages when compared with the performance of conventional FP lasers. Fiber-optic transmission tests show that the proposed device can send directly modulated 2.5 Gbps and 6.25 Gbps optical signals for distances of over 50 km in standard single-mode fiber. Thus, as a cost-effective solution, this device is promising as a replacement for conventional distributed feedback laser diodes in specific applications where single-mode operation is indispensable but precise control of the lasing wavelength and/or very high SMSR (e.g., >40 dB) are not required.