A.H. Clark

Long-wavelength monolithic GaInNAs vertical-cavity optical amplifiers

We report on the continuous-wave amplification characteristics of an optically pumped 1.3-/spl mu/m multiple-quantum-well GaInNAs-GaAs vertical-cavity semiconductor optical amplifier (VCSOA). The VCSOA structure was monolithically grown by molecular beam epitaxy and operated in reflection mode in a fiber-coupled system. The maximum on-chip gain attained, limited by the onset of laser action, was 15.6 dB at 196 mW of 980-nm pump power. For a chip gain of 10.4 dB, the optical bandwidth was 10.8 GHz and the saturation output power was -9 dBm. By varying the pump laser power, a maximum extinction ratio of 22.3 dB was obtained. Temperature-controlled tuneable operation of the device is also presented and demonstration of 9 dB of chip gain obtained over 9.5 nm with an optical bandwidth of 12 GHz is reported.

Optical characteristics of 1.55 μm GaInNAs multiple quantum wells

We report the optical characterization of high-quality 1.55μm GaxIn1−xNyAs1−y multiquantum wells (MQWs), grown on GaAs with Ga(In)N0.01As spacer layers. The transitions between the quantized QW states of the electrons and holes have been identified using photoluminescence excitation spectroscopy. Their energies are consistent with theoretical fitting based on the band anticrossing model. It is also confirmed by detailed spectroscopic measurements that the addition of even a small amount of In to GaN0.01As barriers remarkably improves the optical characteristics of the QWs. The results imply that although strain-compensated GaInNAs MQWs provide a feasible approach to realizing 1.55μm optical emission, the relative lattice mismatch between the wells and barriers is critical to the optical quality of the related QWs.

Effect of multilayer barriers on the optical properties of GaInNAs single quantum-well structures grown by metalorganic vapor phase epitaxy

We report on the effects of combined strain-compensating and strain-mediating layers of various widths on the optical properties of 1.3 μm GaInNAs∕GaAs single quantum well structures grown by metalorganic vapor phase epitaxy (MOVPE). While the emission wavelength of GaInNAs∕GaAs quantum wells can be redshifted by the adoption of strain-compensated GaNAs layers, the material quality is degraded by the increased stress at the well∕barrier interface. This detrimental effect can be cured by inserting a strain-mediating InGaAs layer between them. Contrary to what is expected, however, the emission wavelength is blueshifted by the insertion of the InGaAs layer, which is attributed to the reduced N incorporation due to the improved interface quality. Our results indicate that the optical properties of MOVPE-grown GaInNAs∕GaAs quantum wells can be optimized in quantum efficiency and emission wavelength by combination of strain-compensating and strain-mediating layers with suitable characteristics.

1.3 /spl mu/m GaInNAs monolithic vertical-cavity semiconductor optical amplifier

We report development of a monolithically-grown GaInNAs/GaAs vertical amplifier for 1.3 /spl mu/m operation. When optically-pumped using a 980 nm fibre-coupled diode, demonstration of up to 17.7 dB of on-chip gain has been realised. Amplification with 12.8 dB peak gain, 12 GHz bandwidth and saturation output power of -4.8 dBm is also reported.

Amplification and laser action in diode-pumped 1.3 /spl mu/m GaInNAs vertical-cavity structures

We report fibre-coupled CW diode pumping of 1.3 /spl mu/m GaInNAs/GaAs vertical-cavity semiconductor optical amplifiers (VCSOAs) and surface emitting lasers (VCSELs). The GaInNAs/GaAs structures are monolithic and are specifically designed for optical pumping, offering advantages in design simplification and added functionality. They allow us to demonstrate up to 1.09 dB of amplification and up to 213 /spl mu/W of 1297.2 nm laser emission. Both the 980 nm pump light and 1.3 /spl mu/m signal are coupled to/from the devices by fibers, giving promising systems-compatible demonstrators of GaInNAs-based amplifier technology.

Photoluminescence characterization of midinfrared InNxAs1–x/In0.53Ga0.47As/InP multiquantum wells with various N contents

pare a series of samples which are nominally identical in structure but differ only in N content in the range 0–5%. The photoluminescence PL measurements were carried out in a liquid He cooled flow cryostat of which the temperature can be controlled from 5 to 300 K. The excitation for the PL measurements was provided by a high power cw diode laser 670 nm. The PL signal was collected in a backscattering geometry via CaF2 optics, dispersed by a 0.46-m grating monochromator, and then detected by a thermoelectrically cooled InGaAs detector using standard lock-in techniques. Figure 1 shows the PL spectra at low 5K and room 300 K temperatures, respectively, of three samples of differing N contents N = 0, N = 0.25%, and N = 5%. All the PL spectra are dominated by an emission band denoted as band A with wavelength longer than 2 m which is attributed to the near-band-edge transition of the QWs. The N-induced bowing effect in these structures is evidenced by the PL redshift with the increase of the N content. By observing the

Spectroscopic characterization of 1.3μm GaInNAs quantum-well structures grown by metal-organic vapor phase epitaxy

We report optical studies of high-quality 1.3 mm strain-compensated GaInNAs/ GaAs single-quantum-well structures grown by metalorganic vapor phase epitaxy. Photoluminescence excitation sPLEd spectroscopy shows clearly the electronic structure of the two-dimensional quantum well. The transition energies between quantized states of the electrons and holes are in agreement with theoretical calculations based on the band anti-crossing model in which the localized N states interact with the extended states in the conduction band. We also investigated the polarization properties of the luminescence by polarized edge-emission measurements. Luminescence bands with different polarization characters arising from the electron to heavy-hole and light-hole transitions, respectively, have been identified and verify the transition assignment observed in the PLE spectrum.

Photoluminescence properties of dilute nitride InNAs/InGaAs/InP multi-quantum wells for mid-infrared applications

We report the photoluminescence characterization of a series InNAs/InGaAs multi-quantum wells (MQWs) of various N content on InP substrates. The emission wavelength of these QWs can be tuned effectively by N content. However, the bowing effect is weaker than in GaNAs and GaInNAs. The optical properties of these hetero-structures are closely related to quality of the interface between the barriers and the QWs which is influenced by N content. Two effects of N in this material system have been clarified. On the one hand, the incorporation of N into InAs matrix is beneficial as far as the reduction of band-gap and the lattice constant are concerned. On the other hand, the PL efficiency increases dramatically with the increase of N content. Optimized design and growth could be achieved by trading off between these two effects.

Influence of strain-compensating and strain-mediating layers on the optical properties of MOVPE-grown GaInNAs single quantum-well structures

In summary, we have investigated the dependence of the optical properties of GaInNAs QWs grown by MOVPE on GaNAs SCLs and InGaAs SMLs. Introduction of only SCLs between the GaAs and GaInNAs QW deteriorates the epitaxial quality of the QW due to the increased stress between tensile-strained GaNAs and compressive-strained GaInNAs. This detrimental effect of the interface can be countered by the insertion of a layer of InGaAs. Contrary to what observed in MBE, MOVPE-grown GaInNAs QW with combined SCLs/SMLs demonstrated blue-shifted PL due to the decrease N content with improved QW quality.