C. Z. Tong

High-Temperature Continuous-Wave Single-Mode Operation of 1.3-

In this letter, we have demonstrated continuous-wave single-mode operation of 1.3-mum InAs-GaAs quantum-dot (QD) vertical-cavity surface-emitting lasers (VCSELs) with p-type modulation-doped QD active region from 20degC to 60degC. The highest output power of 0.435 mW and lowest threshold current of 1.2 mA under single-mode operation are achieved. The temperature-dependent output characteristics of QD-VCSELs are investigated. Single-mode operation with a sidemode suppression ratio of 34 dB is observed at room temperature. The critical size of oxide aperture for single-mode operation is discussed.

\mu

The competition of ground state (GS) and excited state (ES) is investigated from the as-grown and thermally annealed 1.3 μm ten-layer p-doped InAs/GaAs quantum dot (QD) lasers. The modal gain competition between GS and ES are measured and analyzed around the ES threshold characteristics. Our results show that two-state competition is more significant in devices with short cavity length operating at high temperature. By comparing the as-grown and annealed devices, we demonstrate enhanced GS and suppressed ES lasing from the QD laser annealed at 600 °C for 15 s.

m p-Doped InAs–GaAs Quantum-Dot VCSELs

The modal gain and differential gain of 1.3-mum p-doped and undoped InAs/GaAs quantum-dot (QD) lasers have been investigated as a function of injection current under different operation temperatures. The results show that p-doping improves the modal and differential gains in QD lasers at high temperatures. Exponential decrease in the differential gain profiles were observed in both types of lasers from 20degC to 80degC. Theoretical calculations based on the rate equation model for the undoped QD laser gain at different temperatures are presented.

Two-state competition in 1.3 μm multilayer InAs/InGaAs quantum dot lasers

In this paper, we present results from room-temperature continuous-wave operation of 1.3-mum p-doped InAs-GaAs quantum-dot (QD) vertical-cavity surface-emitting lasers (VCSELs) with high T 0 of ~510 K and low threshold current density of ~65 A/cm2 per QD layer. The highest output power from the device is over 0.74 mW. The temperature characteristics of the devices are investigated. It is demonstrated that deterioration in QD VCSEL performance due to self-heating results from the temperature sensitivity of QD emission, instead of mismatch between the gain wavelength and cavity modes. The real temperature at the QD VCSEL active region above threshold is estimated from the shift in lasing wavelength, which is in good agreement with calculations based on a self-consistent rate equation and thermal conduction model. The analysis shows that enhancing the carrier confinement in the QD wetting layer contributes to improving the saturated output power of the QD VCSEL.

Temperature Characteristics of Gain Profiles in 1.3-

The modal gain and differential gain of 1.3-μm InAs-GaAs quantum-dot (QD) lasers with different doping concentrations have been investigated as a function of injection current under different operation temperatures from 20°C to 120°C. The results show that QD laser with light doping density can improve the characteristic temperature (To), modal gain, and differential gain and reduce the threshold current density.

\mu\hbox{m}\ p

GaAs quantum dots formed by Ar+ bombardment under normal beam incidence are investigated in both sputtering time and energy domains. When ion energy is maintained at 1000 eV, the surface morphology is found to saturate with high dot uniformity at 3600 s sputtering time. For longer sputtering times, the surface pattern becomes significantly disordered with fluctuations of ∼28 and ∼24 nm in dot height and base width, respectively. The temporal evolution of dots formed at lower ion energies exhibits a similar trend, as observed at 1000 eV. However, the surface morphology develops in a smaller size scale. Based on the experimental results, we propose a power law model to interpret the correlation between sputtering time and energy as well as their impact on the evolution of lateral dot sizes. The experimental results are in good agreement with the theoretical prediction. Furthermore, photoluminescence is performed to characterize the as-grown and annealed GaAs/AlGaAs quantum dots formed by ion sputtering and ...

-Doped and Undoped InAs/GaAs Quantum-Dot Lasers

We present the 1.3-μm InAs quantum dot (QD) vertical cavity surface emitting lasers (VCSELs) with novel planar electrodes configuration. The lasing wavelength is around 1274 nm. The lowest threshold current of wafer level device is ~1 mA, which corresponds to a low threshold current density of ~1.3 kA/cm2 or 76 A/cm2 per QD layer. The maximum output power of 1 mW can be obtained at room temperature. High temperature stability can be seen in temperature dependence L-I characteristics of InAs QD VCSEL 3-dB modulation frequency response of 1.7 GHz can be obtained in the small signal response measurements.

Temperature Characteristics of 1.3-

The influence of quantum dot (QD) density, uniformity and layer number on the 3dB bandwidth of 1.3μm InAs-InGaAs QD VCSELs is investigated by the small signal analysis of all-pathway rate equations. The dependence of bandwidth on the QD density is shown. Linearly dependence of bandwidth on the QD uniformity is demonstrated. High speed operation (> 10GHz) of QD VCSEL emitting at 1.3μm is predicated.

\mu

The threshold characteristic and output power of 1.3 μm quantum dot (QD) vertical-cavity surface-emitting laser (VCSEL) with dots-under-a-well and dots-in-a-well InAs/GaAs QD structures are investigated by using rate equation model and output power model. The influence of VCSEL and QD structures on the modal gain of VCSEL is analyzed. Threshold current density, quantum efficiency, and characteristic temperature are simulated for different QD structures. The dependence of output power of 1.3 μm QD VCSEL on the QD structure, threshold current, quantum efficiency, and oxide-aperture size is investigated in detail.

m p-Doped InAs–GaAs Quantum-Dot Vertical-Cavity Surface-Emitting Lasers

The 1.3 mum InAs quantum dot (QD) vertical cavity surface emitting lasers (VCSELs) with novel planar electrodes configuration were fabricated. The lasing wavelength is around 1273 nm. The typical threshold current is lower than 6 mA. The output power of 0.9 mW with slope efficiency of 0.13 W/A has been recorded. Temperature dependence of the L-I-V relationship of InAs QD VCSELs was investigated. High temperature stability can be achieved with the temperature from 15degC to 50degC. The comparison of temperature characteristics of InAs QD VCSEls with two different oxide aperture sizes indicates the small oxide aperture leads to the more preferable temperature insensitivity.