H. Sudo

Stability in single longitudinal mode operation in GaInAsP/InP phase-adjusted DFB lasers

A single longitudinal mode (SLM) operating condition for phase-adjusted (PA) DFB lasers has been made clear both experimentally and theoretically. As expected, we got a high SLM operation yield of 80 percent in a moderate coupled case up to a light output power of 10 mW. However, in the strongly coupled cases, the two-mode operation with the TE0 mode and the TE + 1 mode occurred frequently. To explain the two-mode operation and to optimize the PA-DFB laser structure, we have developed a theory. Taking the spatial hole burning along the laser axis into account, we succeeded in explaining the longitudinal mode behavior. From our theory, moderate coupling ( kL = 1.25 ) was found to be optimum to maintain the large threshold gain difference above threshold.

An ultrawide-band semiconductor optical amplifier having an extremely high penalty-free output power of 23 dBm achieved with quantum dots

A semiconductor optical amplifier (SOA) having a gain of >25 dB, noise figure of <5 dB, and 3-dB saturation output power of >19 dBm, over the record widest bandwidth of 90 nm among all kinds of optical amplifiers, and also having a penalty-free output power of 23 dBm, the record highest among all the SOAs, was realized by using quantum dots.

1.28μm lasing from stacked InAs∕GaAs quantum dots with low-temperature-grown AlGaAs cladding layer by metalorganic chemical vapor deposition

We report the device characteristics of stacked InAs∕GaAs quantum-dot lasers cladded by Al0.4Ga0.6As layer grown at a low temperature by metalorganic chemical vapor deposition. A blueshift in emission energy by the effect of postgrowth annealing can be suppressed when the annealing temperature is below 570°C. We achieved the 1.28μm continuous-wave lasing at room temperature of five layer stacked InAs∕GaAs quantum dots embedded in In0.13Ga0.87As strain-reducing layer whose p-cladding layer is grown at 560°C. From the experiments and calculations of the gain spectra of fabricated quantum-dot lasers, the observed lasing originates from the first excited state of stacked InAs quantum dots.

InAs∕GaAs self-assembled quantum-dot lasers grown by metalorganic chemical vapor deposition—Effects of postgrowth annealing on stacked InAs quantum dots

We investigated the effects of postgrowth annealing on stacked InAs∕GaAs quantum dots. The blueshift in emission energy by postgrowth annealing depends on the temperature of postgrowth annealing and the growth conditions of stacked InAs quantum dots, such as a spacer thickness or a stacking number. We can control the peak wavelength of stacked InAs quantum dots by changing the temperature of postgrowth annealing and the growth conditions of stacked InAs quantum dots. We achieved continuous-wave lasing with a threshold current of 16.4mA at the wavelength of 1.245μm from five layer vertically aligned InAs quantum dots whose upper cladding layer was grown at 600°C.

Catastrophic degradation of GaAlAs DH laser diodes

The catastrophic degradation of GaAlAs DH laser diodes is examined with the application of pulsed or dc current. The dependence of the pulsewidth on the degradation is measured using samples with or without facet coating. The light output PD at which the catastrophic degradation occurs decreases with an increase in the pulsewidth in the pulsewidth range 100 nsec to 10–50 μsec, and PD is constant over the pulsewidth of 10–50 μsec. The sample with an Al2O3 film coating has the highest PD. Photoluminescence patterns of the active layer in degraded samples both with and without facet coating show the growth of DLD’s in the 〈110〉 direction from the vicinity of a facet in the stripe region.

Ground state lasing at 1.34μm from InAs∕GaAs quantum dots grown by antimony-mediated metal organic chemical vapor deposition

The authors report the fabrication of GaAs-based quantum dot (QD) lasers grown by metal organic chemical vapor deposition above 1.30μm. They fabricated a laser diode with five stacked InAs∕Sb:GaAs(100) QD layers, grown by antimony-surfactant-mediated growth. Ground state lasing was obtained at 1.34μm, with internal quantum efficiency of 62%, internal loss of 4.5cm−1 and ground state modal gain above 12cm−1. Lasing above 1.30μm could be achieved because of the beneficial effects of antimony on both the coherent InAs∕Sb:GaAs QD density and the suppression of the emission blueshift, usually observed for InAs∕GaAs QDs during postgrowth annealing at 600°C.

Ultra-High speed InGaAsP/InP DFB lasers emitting at 1.3 &#181;m wavelength

A bandwidth of 13 GHz has been attained in a 1.3 μm DFB laser at 25 °C. A mesa structure was introduced to reduce the parasitic capacitance and the lasing wavelength was detuned from the gain peak to increase the differential gain. This bandwidth is the widest so far reported in 1.3 μm DFB lasers.

Interface properties of InAs quantum dots produced by antimony surfactant-mediated growth: Etching of segregated antimony and its impact on the photoluminescence and lasing characteristics

We present a method that improves the emission efficiency of InAs quantum dots (QDs) fabricated by antimony surfactant-mediated metal organic chemical vapor deposition. This process consists of removing the excess segregated antimony from the surface of InAs/Sb:GaAs QDs by applying a high arsenic pressure before capping. In such a way, one benefits from the advantages of InAs/Sb:GaAs QDs (high density, low coalescence) without the formation of antimony-induced nonradiative defects. Finally, we show that this better QD interface quality results in a strong decrease of the threshold current densities of InAs/Sb:GaAs QD lasers in the 1.3 μm band.

One‐step‐metalorganic‐vapor‐phase‐epitaxy‐grown AlGaInP visible laser using simultaneous impurity doping

We fabricated a GaInP/AlGaInP visible laser with a real‐index guide structure by one‐step metalorganic vapor phase epitaxy using simultaneous impurity doping. We achieved an effective self‐aligned current‐confinement structure in the AlGaInP cladding layer and a threshold current of only 18 mA. The laser had stable transverse‐mode oscillation with a beam astigmatism less than 1 μm.

CW Lasing at 1.35

We report the fabrication of GaAs-based quantum-dot (QD) lasers grown by metal-organic chemical vapor deposition (MOCVD) above 1.3 m. We fabricated a laser diode with ten stacked InAs-Sb:GaAs(100) QD layers, grown by antimony-surfactant-mediated growth. Ground-state lasing was obtained under continuous-wave operation at room temperature at 1.35 mum, with a maximum ground state modal gain of 19.3 cm-1. These values are the highest values reported for MOCVD-grown GaAs-based QD laser.