Butterfly Packaged Ultra-Narrow Linewidth Single Frequency Teardrop Laser Diode

In this letter, an InP-based single facet teardrop laser which integrates a 1 × 2 multi-mode interferometer and a linear curvature loop reflector deep-etched by inductively coupled plasma is demonstrated. The teardrop lasers which have the loop reflectors with different radius of curvature values (25, 50, 75, 100, and 150 μm) have been successfully designed and fabricated, and the one with 75-μm radius loop shows the lowest lasing threshold and highest slope efficiency. The butterfly packaged teardrop laser with 150-μm radius loop reflector shows a single frequency emission at 1562.5 nm with 30-dB side mode suppression ratio and 75-kHz ultra-narrow linewidth at room temperature with 100-mA current injection on the MMI and 60 mA on the ring.