Two-section DFB Laser
The schematic view of the two-section-DFB laser is shown in Fig. 1. The two-section DFB laser contains two sections: the active section and the reflection section. The reflection section acting as a distributed reflector, is integrated right behind the active section. Both sections contain the gratings, while only one section has current injection when the DFB laser is normally working.
Fig. 1. Schematic diagram of the two-section DFB laser
The active section has a special structure with the phase shift positioned closer to the reflection section. The reflection section is carefully designed to provide sufficient reflection and chirp if needed. The microscope image of the fabricated device is shown in Fig. 2.
Fig. 2. Microscope image of the fabricated two-section DFB laser
The two-section DFB laser has four key merits:
1. Simple and robust fabrication process;
2. Accurately wavelength locked by a distributed Bragg reflector;
3. Close to 100% yield for side-mode suppression ratio;
4. High Reliability with both anti-reflection (AR) coating.