Threshold simulation of 1.3-μm oxide-confined in-plane quantum-dot (InGa)As/GaAs lasers (original) (raw)
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Optical and Quantum Electronics, 2000
In the paper, a comprehensive fully self-consistent three-dimensional simulation of an operation of the GaAs-based oxide-confined long-wavelength 1.3-lm quantum-dot (QD) (InGa)As/GaAs verticalcavity surface-emitting diode lasers is demonstrated. The model has been intentionally prepared for the PC-class microcomputers to enable its easy application in designing optimal structures of the above devices with desired performance characteristics. An impact of some structure parameters on QD VCSEL room-temperature (RT) continuous-wave (CW) lasing thresholds is discussed. A stable RT CW operation on a single fundamental mode has been found to be possible in modern QD VCSELs with active regions containing more uniform and more dense QDs in stacks of QD layers. The desired single fundamentaltransverse-mode operation is possible for smaller active regions of diameters not exceeding 8 lm. In the case of larger active regions, on the other hand, higher-order transverse modes of an increasing order are excited first because of increasingly more non-uniform optical-gain distributions.
Effect of excited-state transitions on the threshold characteristics of a quantum dot laser
IEEE Journal of Quantum Electronics, 2001
The general relationship between the gain and spontaneous emission spectra of a quantum dot (QD) laser is shown to hold for an arbitrary number of radiative transitions and an arbitrary QD-size distribution. The effect of microscopic parameters (the degeneracy factor and the overlap integral for a transition) on the gain is discussed. We calculate the threshold current density and lasing wavelength as a function of losses. The conditions for a smooth or step-like change in the lasing wavelength are described. We have simulated the threshold characteristics of a laser based on self-assembled pyramidal InAs QDs in the GaAs matrix and obtained a small overlap integral for transitions in the QDs and a large spontaneous radiative lifetime. These are shown to be a possible reason for the low single-layer modal gain, which limits lasing via the ground-state transition for short (several hundreds of micrometers) cavity lengths.
Threshold Temperature Dependence of a Quantum-Dot Laser Diode With and Without p-Doping
IEEE Journal of Quantum Electronics, 2009
A study of the threshold characteristics of quantum-dot (QD) laser diodes shows how inhomogeneous broadening and p-doping influence the QD laser's temperature dependence of threshold 0. The analysis includes the additional parameters of homogeneous broadening, quantum state populations, and threshold gain. The results show that while the source of negative 0 can occur due to different effects, the transparency current plays a critical role in both undoped and p-doped QD lasers. Experimental trends of negative 0 and their dependence on p-doping are replicated in the calculated results. Inhomogeneous broadening is found to play a lesser role to the transparency current in setting 0. Homogeneous broadening is most important for uniform QDs with thermally isolated ground-state transitions.
Optical characteristics of 1.24-μm InAs quantum-dot laser diodes
IEEE Photonics Technology Letters, 2000
The optical characteristics of the first laser diodes fabricated from a single-InAs quantum-dot layer placed inside a strained InGaAs QW are described. The saturated modal gain for this novel laser active region is found to be 9-10 cm 01 in the ground state. Room temperature threshold current densities as low as 83 A/cm 2 for uncoated 1.24-m devices are measured, and operating wavelengths over a 190-nm span are demonstrated.
Simulation of characteristics of broadband quantum dot lasers
Optical and Quantum Electronics, 2008
Authors theoretically present the characterization of the multiple states broadband InGaAs/GaAs quantum-dot lasers that agrees well with the measured data. Based on the derived model, this new class of semiconductor laser is further characterized theoretically to gain an idea of the derivative characteristic such as linewidth enhancement factor in providing a picture of the competency of this novel device for diverse applications.
C.Y. Jin, H.Y. Liu, T.J. Badcock, K.M. Groom, M. Gutie´ rrez, R. Royce, M. Hopkinson and D.J. Mowbray, 2006
A high-growth-temperature GaAs spacer layer (HGTSL) is shown to significantly improve the performance of 1.3 mm multilayer InAs/GaAs quantum-dot (QD) lasers. The HGTSL inhibits threading dislocation formation, resulting in enhanced electrical and optical characteristics and hence improved performance of QD lasers. To further reduce the threshold current density and improve the room-temperature characteristic temperature (T0), the high- reflection (HR) coating and p-type modulation doping have been incorporated with the HGTSL technique. A very low continuous-wave room-temperature threshold current of 1.5 mA and a threshold current density of 18.8 A cm22 are achieved for a three-layer device with a 1 mm HR/HR cavity, while a very low threshold current density of 48 A/cm2 and a negative T0 are achieved in the p-doped lasers.
Gain Characterisation of 1.3μm GaAs Quantum Dot lasers
2012
Gain characterisation of a laser device is of fundamental importance to assist in the physical understanding of laser materials. Not only does it determine important parameters such as threshold, material loss and transparency current density, but is also a vital source of information regarding the evolution of states as a function of current density and temperature. The differential gain (dg/dn) is of key importance in determining the dynamic performance of a laser. Hence, the important role of gain characterisation has driven researchers to devise improved techniques for spectral gain measurement. This thesis discusses the gain characterisation of 1.3I¼m quantum dot, commercial Innolume material and bi-layer laser devices. Initially, different gain measurement techniques are reviewed. High resolution spectroscopy and variable stripe length methods are analysed and compared in detail. A technical review is presented for the first time for the commonly used Hakki and Paoli, segmente...
High-performance InAs/GaAs quantum dot laser with dot layers grown at 425 oC
Chinese Optics Letters, 2013
We investigate InAs/GaAs quantum dot (QD) lasers grown by gas source molecular beam epitaxy with different growth temperatures for InAs dot layers. The same laser structures are grown, but the growth temperatures of InAs dot layers are set as 425 and 500 • C, respectively. Ridge waveguide laser diodes are fabricated, and the characteristics of the QD lasers are systematically studied. The laser diodes with QDs grown at 425 • C show better performance, such as threshold current density, output power, internal quantum efficiency, and characteristic temperature, than those with QDs grown at 500 • C. This finding is ascribed to the higher QD density and more uniform size distribution of QDs achieved at 425 • C.
IEEE Photonics Technology Letters, 2000
The wavelength of InAs quantum dots in an In 0 15 Ga 0 85 As quantum-well (DWELL) lasers grown on a GaAs substrate has been extended to 1.3-m. The quantum dot lasing wavelength is sensitive to growth conditions and sample thermal history resulting in blue shifts as much as 73 nm. The room temperature threshold current density is 42.6 A cm 2 for 7.8-mm cavity length cleaved facet lasers under pulsed operation.