Nicolas Chevalier

Room temperature operation of GaAsP(N)/GaP(N) quantum well based light-emitting diodes: Effect of the incorporation of nitrogen

This letter deals with the electroluminescence emission at room temperature of two light-emitting diodes on GaP substrate, based on ternary GaAsP/GaP and quaternary GaAsPN/GaPN multiple quantum wells. In agreement with tight-binding calculations, an indirect band gap is demonstrated from the temperature-dependent photoluminescence for the first structure. High efficiency photoluminescence is then observed for the second structure. Strong electroluminescence and photocurrent are measured from the diode structures at room temperature at wavelengths of 660 nm (GaAsP/GaP) and 730 nm (GaAsPN/GaPN). The role of the incorporation of nitrogen on the optical band gap and on the nature of interband transitions is discussed.

Room temperature photoluminescence of high density (In,Ga)As/GaP quantum dots

We report on the achievement of high density (In,Ga)As self-assembled quantum dots on GaP substrate with a good homogeneity. Good structural and electronic properties have been achieved, as revealed by room temperature photoluminescence measurements and by comparison to both InAs/GaAs and InAs/InP materials reference systems. This is supported by atomistic calculations where the indium incorporation in InGaAs/GaP quantum structures is found to enhance both the type-I bandlineup and direct bandgap properties. The photoluminescence temperature dependence of the bandgap evidences the quantum confinement effects. Our results provide a valid framework to implement silicon optical devices based on InGaAs/GaP nanostructures.

41 GHz and 10.6 GHz low threshold and low noise InAs/InP quantum dash two-section mode-locked lasers in L band

This paper reports recent results on InAs/InP quantum dash–based, two-section, passively mode-locked lasers pulsing at 41 GHz and 10.6 GHz and emitting at 1.59 μm at 20 °C. The 41-GHz device (1 mm long) starts lasing at 25 mA under uniform injection and the 10.6 GHz (4 mm long) at 71 mA. Their output pulses are significantly chirped. The 41-GHz laser exhibits 7 ps pulses after propagation in 60 m of a single-mode fiber. The 10.6-GHz laser generates one picosecond pulses with 545 m of a single-mode fiber. Its single side-band phase noise does not exceed –80 dBc/Hz at 100 kHz offset, leading to an average timing jitter of 800 fs.

Achievement of High Density InAs/GaInAsP Quantum Dots on Misoriented InP(001) Substrates Emitting at 1.55 µm

InAs quantum dot (QD) formation on InP(001) has been investigated by gas source molecular beam epitaxy as a function of the substrate misorientation, arsenic pressure and temperature. A large improvement on quantum dot shape and density was obtained thanks to the use of substrates misoriented toward the [110] direction and low arsine flow rate. Round-shaped small QDs (diameter: 26 nm) in high density (9×1010 QDs/cm2) have been achieved using optimized growth conditions. Room temperature laser emission around 1.55 µm from was obtained with a threshold current density of 1 kA/cm2 for 1 mm long cavity.

Enhancement of the polarization stability of a 1.55 µm emitting vertical-cavity surface-emitting laser under modulation using quantum dashes

Polarization controlled quantum dashes (QDHs) Vertical Cavity Surface Emitting Lasers (VCSELs) emitting at 1.6 µm grown on InP(001) are investigated and compared with a quantum well (QW) similar VCSEL. Polarization stability of optically-pumped VCSELs under a low frequency modulation is investigated. While major fluctuations of the polarization-resolved intensity are observed on QW-based structures, enhanced polarization stability is reached on QDH-based ones. Statistical measurements over a large number of pulses show an extremely low variation in QDH VCSEL polarized output intensity, related to the intrinsic polarization control. This makes QDH VCSEL ideal candidate to improve telecommunication networks laser performances.

10-GHz 1.59-μm quantum dash passively mode-locked two-section lasers

This paper reports the fabrication and the characterisation of a 10 GHz two-section passively mode-locked quantum dash laser emitting at 1.59 μm. The potential of the devices mode-locking is investigated through an analytical model taking into account both the material parameters and the laser geometry. Results show that the combination of a small absorbing section coupled to a high absorption coefficient can lead to an efficient mode-locking. Characterisation shows mode-locking operation though output pulses are found to be strongly chirped. Noise measurements demonstrate that the single side band phase noise does not exceed -80 dBc/Hz at 100 kHz offset leading to an average timing jitter as low as 800 fs. As compared to single QW lasers these results constitute a significant improvement and are of first importance for applications in optical telecommunications.

VCSEL Based on InAs Quantum-Dashes With a Lasing Operation Over a 117-nm Wavelength Span

We report an InP based vertical cavity surface emitting laser (VCSEL) achieving a lasing operation between 1529 and 1646 nm. This optically-pumped VCSEL includes a wide-gain bandwidth active region based on InAs quantum dashes and wideband dielectric Bragg mirrors. Based on a wedge microcavity design, we obtain a spatial dependence of the resonant wavelength along the wafer, enabling thus to monitor the gain material bandwidth. We demonstrate a 117 nm continuous wavelength variation of the VCSEL emission, a consequence of the important and wide gain afforded by the use of optimized quantum dashes.

Coherent integration of photonics on silicon through the growth of nanostructures on GaP/Si

Selected results obtained in the framework of MBE grown nanostructure for photonics on silicon are repsented in this paper. We present first a comprehensive study of GaAsPN/GaPN quantum wells (QWs) grown onto GaP substrates, in the light of a comparison with their N-free GaAsP/GaP QWs counterpart system. High density of small InGaAs/GaP Quantum Dots are presented next with their PL properties. Finally, RT photoluminescence properties of GaAsPN/GaPN QWs onto Si substrate are presented and discussed in term of carrier injection efficiency. However, for future development, optical properties of the active area must be improved and are tightly bound to the structural perfection of the GaP/Si template layer. To address this point, structural analyses including X-Ray Diffraction (lab setup and synchrotron) and Transmission Electron Microscopy have been performed, with a particular care for typical III-V/Si defect characterisation. First results of Si buffer layer growth are also presented as a perspective for future low defect MBE grown GaP/Si template layers.

Improvement of 1.55 µm InAs QD laser using vicinal (001)InP substrate

We present an improvement of threshold current density of InAs QD lasers emitting at 1.55µm on vicinal InP(001) substrate. High round shaped QDs density were achieved by combining the right off-cut direction of the InP(001) substrate with the optimized arsenic flux. A maximum QDs density of 9×10¹⁰cm⁻² was obtained using a low arsine flow rate and an InP(001) substrate misoriented toward the [1–10] direction. Room temperature laser emission around 1.55µm from round shaped quantum dots was obtained with a threshold current density of 1kA/cm² from 1mm long cavity.

Design of InGaAs/InP 1.55μm vertical cavity surface emitting lasers

The design of an electrically pumped InGaAs quantum well based vertical cavity surface emitting laser (VCSEL) on InP substrate is presented. Such optically pumped VCSELs have already been demonstrated. To design electrically pumped VCSEL, three simulations steps are needed: optical simulation gives access to the electric field repartition, to design the active zone and the Bragg mirrors. Thermal simulation is helpful to design metallic contacts while the energy band diagram is obtained by electrical simulation to design the buried tunnel junction useful for carrier injection. All these simulations are compared to experiment.