Single longitudinal mode GaAs-based quantum dot laser with refractive index perturbation.

We report on the design, fabrication, and characterization of single longitudinal mode InAs/GaAs quantum dot lasers emitting at the 1.3 µm communication band. The influence of simply etched surface high-order gratings in the ridge of the Fabry-Perot lasers has been studied. A 35th-order surface grating is fabricated by standard photolithography to introduce the refractive index perturbation, which leads to the reduced mirror loss at the desired wavelength and thus realizing single longitudinal mode lasing. Stable single-mode operations are maintained at the injection current range of 45-100 mA with a side-mode suppression ratio up to 33 dB.

Ultra-broadband tunable single- and double-mode InAs/InP quantum dot external-cavity laser emitting around 1.65 µm.

We report an ultra-wide tunable single- and double-mode InAs/InP quantum dot (QD) external-cavity (EC) laser in a Littrow configuration. By combining the high modal gain of the QD material in the long wavelength range and an anti-reflection/high-reflection facet coating, the entire single-mode tuning range was increased up to 190 nm under a relatively low constant pulsed injection current. Furthermore, the tunable range was further increased to 230 nm at different bias currents. In addition, a mode spacing as wide as 100 nm was achieved using the same QD-EC device in the dual-mode operation, corresponding to a frequency difference of approximately 11 THz.

Continuously tunable mode-spacing of a dual-mode external cavity InAs/InP quantum dot laser.

A tunable double-mode external cavity InAs/InP quantum dot laser based on a dual-Littrow configuration is demonstrated. A 115 nm single-mode tuning spectrum with obviously varied mode intensity has been obtained. A modified tuning method has been adopted to realize continuously tunable mode-spacing between two modes. It is found that single and double modes coexist in the tuning spectrum when one grating angle is fixed while the other grating is rotated; the biggest mode-spacing between double modes is about 75 nm. A continuously tunable range of mode-spacing between double wavelengths has reached up to 80 nm by inserting an attenuation slice in the external optical feedback paths to balance the intensity of the double modes; the separation of double modes is about 50 nm at best. The average output power of the double-mode laser is about a few milliwatts.