A wavelength-tunable mode-locked quantum dot laser using an In As/Ga As quantum-dot gain medium and a discrete semiconductor saturable absorber mirror is demonstrated.A dispersion prism,which has lower optical loss and less spectral narrowing than a blazed grating,is used for wavelength selection and tuning.A wavelength tuning range of 45.5 nm(from1137.3 nm to 1182.8 nm) under 140-m A injection current in the passive mode-locked regime is achieved.The maximum average power of 19 m W is obtained at the 1170.3-nm wavelength,corresponding to the single pulse energy of 36.5 p J.
A wide wavelength tuning range swept external-cavity laser using an In As/Ga As quantum-dot superluminescent diode as a gain device is demonstrated. The tunable filter consists of a polygon scanner and a grating in Littrow telescope-less configuration. The swept laser generates greater than 54-m W peak output power and up to 33-k Hz sweep rate with a sweep range of 150 nm centered at 1155 nm. The effects of injection current and sweep rate on the sweep performance of the swept laser are studied.
We report a new quantum dot superluminescent diode with a new device structure. In this device, a multimode-interferometer configuration and a J-bend structure were monolithically integrated. Owing to the multi-modeinterferometer structure, the superluminescent diode exhibits 60% increase in output power and 43% reduction in the differential resistance compared with the uniform waveguide width superluminescent diode fabricated from the same wafer. Our device produces an emission spectrum as wide as 103.7 nm with an output power of 2.5 m W at 600 m A continue-wave injection current. This broadband emission spectrum makes the axial resolution of the optical coherence tomography system employing the superluminescent diode to 6 m in theory, which is high enough for most tissue imaging.
We report the effect of the GaAs spacer layer thickness on the photoluminescence(PL) spectral bandwidth of InAs/GaAs self-assembled quantum dots(QDs).A PL spectral bandwidth of 158 nm is achieved with a five-layer stack of InAs QDs which has a 11-nm thick GaAs spacer layer.We investigate the optical and the structural properties of the multilayer-stacked InAs/GaAs QDs with different GaAs spacer layer thicknesses.The results show that the spacer thickness is a key parameter affecting the multi-stacked InAs/GaAs QDs for wide-spectrum emission.
With a chirped InAs/GaAs SML-QD (quantum dot) structure serving as the active region, the superluminescent diodes emitting at wavelength of around 970nm are fabricated. By using an active multimode interferometer configuration, these devices exhibit high continue-wave output powers from the narrow ridge waveguides. At continue-wave injection current of 800mA, an output power of 18.5mW, and the single Gaussian-like emission spectrum centered at 972nm with a full width at half maximum of 18nm are obtained.
The optical performance of a grating-coupled external cavity laser based on InAs/InP quantum dots is investigated. Continuous tuning from 1391 nm to 1468 nm is realized at an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented.
