H. S. Djie

Room-temperature broadband emission of an InGaAs/GaAs quantum dots laser.

We report the first demonstration to our knowledge of an ultrabroad emission laser using InGaAs/GaAs quantum dots by cycled monolayer deposition. The device exhibits a lasing wavelength coverage of approximately 40 nm at an approximately 1160 nm center wavelength at room temperature. The broadband signature results from the superposition of quantized lasing states from highly inhomogeneous dots.

InGaAs/GaAs Quantum-Dot Superluminescent Diode for Optical Sensor and Imaging

We report on the design and fabrication of a novel wideband superluminescent diode (SLD) based on InGaAs/GaAs quantum-dot structure. In this device, we monolithically integrate a photon absorber section to suppress lasing action and optical feedback oscillation. The fabricated SLDs produce a close-to-Gaussian shaped spectrum centered at 1210 nm with a bandwidth of 135 nm. Spectral ripple as low as 0.3 dB has been measured

Wideband quantum-dash-in-well superluminescent diode at 1.6 /spl mu/m

We demonstrate broadband superluminescent diode at ~1.6-mum peak emission wavelength using InAs-InAlGaAs quantum-dash-in-well structure on InP substrate. The fabricated device exhibits the close-to-Gaussian emission with a bandwidth of up to 140 nm. The device produces a low spectrum ripple of 0.3dB and an integrated power of 1.7 mW with the corresponding bandwith of 110 nm measured at 20 degC under 8 kA/cm2

Wavelength tuning and emission width widening of ultrabroad quantum dash interband laser

The authors report the demonstration of the bandgap-tuned InAs quantum dash broadband laser with widened laser emission linewidth at room temperature using postgrowth intermixing technique. The 100 nm wavelength blueshifted, as-cleaved laser exhibits ultrabroad lasing spectral coverage of ∼85 nm at a center wavelength of 1.54 μm with a total emission power of ∼1 W per device. Compared to the as-grown laser, this laser shows broader lasing bandwidth (∼41 nm) with improved spectral ripple (<1 dB).

Neutral ion-implantation-induced selective quantum-dot intermixing

High spatial band-gap tuning has been observed from an InGaAs∕GaAs quantum-dot (QD) structure implanted with electrically neutral species, As and P ions, at 200°C followed by a rapid thermal annealing. Phosphorous was found to be a more effective species to induce QD intermixing than the As at similar dose level. A blueshift as large as 126meV has been observed from the P+-implanted and intermixed sample, while only ∼14meV has been measured from the SixNy-capped sample.

Role of optical gain broadening in the broadband semiconductor quantum-dot laser

The authors present a theoretical model and analysis to gain a further insight of the broadband InGaAs∕GaAs quantum-dot laser characteristics. A detailed analysis of the role of both inhomogeneous and homogeneous optical gain broadenings on the broad lasing emission is incorporated in the theoretical model and compared with the experimental results. The experimental data of broadband laser signature agrees well with theoretical calculation confirming that the broadband stimulated emission from the laser at room temperature is a result of the occurrence of bistate lasing in highly inhomogeneous dots.

Group-III intermixing in InAs∕InGaAlAs quantum dots-in-well

We report selective postgrowth band gap tuning of InAs∕InGaAlAs quantum dots-in-well grown on InP substrate using impurity-free group-III intermixing. In contrast to most reported intermixing results, SixNy annealing cap results in a larger band gap blueshift than SiO2 annealing cap with a differential shift of 92nm after annealing at 800°C for 30s. Intermixing also results in large wavelength tuning from 1.6to1.37μm at room temperature, accompanied by luminescence linewidth reduction and intensity improvement. According to our theoretical model, we postulate that the unusual In(GaAl)As intermixing is governed by different interdiffusion rates of group-III atoms.

Defect Annealing of InAs–InAlGaAs Quantum-Dash-in-Asymmetric-Well Laser

We report the improvement of ~1.62-mum wavelength InAs-InAlGaAs quantum-dash-in-asymmetric-well laser performance using rapid thermal annealing. After the postgrowth annealing at 700 degC for 2 min, the internal quantum efficiency is increased from 90% to 93%, and the linewidth of the laser spectrum and the threshold current density is significantly reduced

The Influence of Nonequilibrium Distribution on Room-Temperature Lasing Spectra in Quantum-Dash Lasers

We demonstrate the effect of nonequilibrium carrier distribution in a self-assembled InAs-InAlGaAs quantum-dash-in-well semiconductor lasers on InP substrate. The progressive changes of electroluminescence spectrum with increasing injections show the presence of localized photon reabsorption and lasing action from different dash ensembles at room temperature as opposed to that obtained in typical self-assembled quantum-dot lasers only at low temperature below 100 K.

Postgrowth band gap trimming of InAs∕InAlGaAs quantum-dash laser

The authors demonstrate the selective postgrowth band gap engineering and the fabrication of band gap tuned laser in InAs–InAlGaAs quantum-dash lasers grown on InP substrate. The process utilizes nitrogen implantation to induce local defects and to enhance the group-III intermixing rate spatially upon the thermal annealing. Compared with the as-grown laser, intermixed laser with wavelength shifted by 127nm shows a 36% reduction in threshold current density and produces a comparable slope of efficiency. The integrity of the intermixed material is retained suggesting that intermixing process paves way to planar, monolithic integration of quantum-dash-based devices.