Avalanche multiplication and excess noise arising from both electron and hole injection have been measured on a series of In 0.52 Al 0.48 As p + -i-n + and n + -i-p + diodes with nominal avalanche region widths between 0.1 and 2.5 mum. With pure electron injection, low excess noise was measured at values corresponding to effective k=beta/alpha between 0.15 and 0.25 for all widths. Enabled ionization coefficients were deduced using a non-local ionization model utilizing recurrence equation techniques covering an electric field range from approximately 200 kV/cm to 1 MV/cm

An ultrafast high-contrast all-optical switch produced from a metal-organic vapor phase epitaxy-grown wafer incorporating a 50-period InGaAsP/InGaAsP multiple-quantum-well (MQW) saturable absorber (SA) and a distributed Bragg reflector is described. Postgrowth implantation with 4-MeV nitrogen ions reduces the MQW free-carrier lifetime, and hence the switch recovery time, to 5.2 ps. Incorporation of the MQW SA in an optical cavity results in switching contrast ratios greater than 10 dB. The all-optical switch is used to perform wavelength conversion of 2-ps pulses.

An ultrafast high-contrast all-optical switch produced from a metal-organic vapor phase epitaxy-grown wafer incorporating a 50-period InGaAsP/InGaAsP multiple-quantum-well (MQW) saturable absorber (SA) and a distributed Bragg reflector is described. Postgrowth implantation with 4-MeV nitrogen ions reduces the MQW free-carrier lifetime, and hence the switch recovery time, to 5.2 ps. Incorporation of the MQW SA in an optical cavity results in switching contrast ratios greater than 10 dB. The all-optical switch is used to perform wavelength conversion of 2-ps pulses.

We establish the MOVPE growth conditions of InAs/GaAs quantum dots (QDs) with photoluminescence (PL) emission from 1.1 to 1.25 mum in a commercial 8x3" multiwafer reactor (Aixtron 2400) for the production of telecommunication devices. We describe techniques to improve the QD size uniformity and minimize the number of defects. For PL emission at 1.1 mum,we achieve a dot density of similar to10(11) cm(-2) as measured by transmission electron microscopy.

Time-resolved photoluminescence measurements of an undoped InGaAsP multiple-quantum-well heterostructure at excess carrier densities between 10(14) and 10(16) cm(-3) reveal unexpectedly long carrier lifetimes, in excess of 2 mus. By fitting the appropriate rate equation parameters to our results, we establish that radiative recombination is the dominant relaxation process, and show that nonradiative recombination is much less pronounced than in similar quantum-well structures measured previously. (C) 2002 American Institute of Physics.

The reduction in penetration of the optical mode into the cladding layers in large optical cavity (LOC) laser structures offers the possibility of reducing the cladding-layer thickness. This could be particularly beneficial in GaInP-AlGaInP high-power devices by reducing the thermal impedance and the electrical series resistance. We have designed and characterized 650-nm LOC lasers by modeling the optical loss due to incomplete confinement of the optical mode by the cladding layers and calculating the thermally activated leakage current. This indicated that the cladding thickness could be reduced to 0.5 mum without adversely affecting performance. We investigated devices with 0.3-, 0.5-, and 1-mum-wide cladding layers. The measured optical mode loss of the 0.3 mum-wide cladding device was 36.2 cm(-)1 compared with 12.4 and 11.3 cm(-1) for the 0.5- and 1 mum-wide cladding samples, respectively. The threshold current densities of the 0.5- and 1.0-mum devices were similar over the temperature range investigated (120-320 K), whereas the 0.3-mum devices had significantly higher threshold current density. We show that this can be attributed to the higher optical loss and increased leakage current through the thin cladding layer. The intrinsic gain characteristics were the same in all the devices, irrespective of the cladding-layer thickness. The measured thermal impedance of 2-mm-long devices was reduced from 30.7 to 22.3 K/W by reducing the cladding thickness from I to 0.5 mum. Our results show that this can be achieved without detriment to the threshold characteristics.

We analyze the 1.5μm wavelength operation of a room temperature polarization switch based on electron spin dynamics in InGaAsP multiple quantum wells. An unexpected difference in response for left and right circularly polarized pump light in pump–probe measurements was discovered and determined to be caused by an excess carrier induced birefringence. Transient polarization rotation and ellipticity were measured as a function of time delay.

The luminescence properties of InGaN multiquantum well (MQW) light emitting diodes (LEDs) with various emission wavelengths were investigated using electroluminescence (EL) microscopy (ELM) and micro-EL (μ-EL) spectroscopy. Spatial inhomogeneity of the QW emission was observed as a function of the emission wavelength in spectrally resolved ELM images. The results show that the emission from diodes with shorter emission wavelengths exhibit less spatial inhomogeneity, while bright features were observed on the surface of samples with longer emission wavelengths. μ-EL spectra obtained from 5×5 μm2 regions show an increase in the full width at half maximum (FWHM) of the spectra with increasing injection current and emission wavelength. With increasing emission wavelength, there is a shift in the main emission area from the p-contact area to the n-contact. The μ-EL spectra obtained from different bright spots in the ELM images demonstrate the variation of main emission peak position and FWHM of the EL spectra. The results suggest that the band-tailing effect due to small self-organised In-rich regions play a key role in the emission of the InGaN MQWs.

Time-resolved photoluminescence measurements of an undoped InGaAsP multiple-quantum-well heterostructure at excess carrier densities between 1014 and 1016 cm−3 reveal unexpectedly long carrier lifetimes, in excess of 2 μs. By fitting the appropriate rate equation parameters to our results, we establish that radiative recombination is the dominant relaxation process, and show that nonradiative recombination is much less pronounced than in similar quantum-well structures measured previously.

We describe the development of InGaAsP multiquantum-well asymmetric Fabry-Perot modulators (AFPM) for RF-over-fiber applications. Advantages of the AFPM include low drive voltage and loss, high linearity and simple fiber alignment. Experimental results of initial devices, exhibiting 5.5-dB modulation depth and >3-GHz operation, are described. The effect of the optical power on the device performance was assessed, and the modulation bandwidth was found to be unaffected by incident optical powers up to 0 dBm. The linearity of the modulation characteristic was measured by carrying out two-tone intermodulation distortion tests, and a third-order intercept point of 30 dBm was observed.

Using a segmented-contact method, we have measured the optical mode loss in a series of AlGaInP 650 nm large optical cavity laser diodes with cladding layer thicknesses of 1.0, 0.5 and 0.3 µm. For the thinnest cladding layer the loss is 24 cm-1 greater than the other devices and by comparison with transfer matrix calculations we show that this is due to penetration of the mode into the outer GaAs layers. The results show that the cladding thickness can be reduced to about 0.5 µm without significant increase in loss and threshold current and this could be beneficial in reducing the electrical and thermal resistance of the cladding layer in high power structures.

We describe fast recovery at a wavelength of 1550 nm in a multiple-quantum-well (MQW) saturable absorber with InGaAsP quaternary wells and barriers using electric-field-induced carrier sweepout. The MQW SA is integrated with a distributed Bragg reflector in a p-type–intrinsic–n-type structure. Pump–probe measurements show that the recovery time can be reduced from >900 to 28 ps by application of a 151 kV/cm sweepout field. We measure the dependence of the recovery time on the energy of the saturating pulse and explain our results in terms of carrier dynamics in the sweepout field.

A report of a 1.55 /spl mu/m multichannel source using quaternary/quaternary multiple quantum well InGaAsP/InP quantum confined Stark effect tuning for dense wavelength division multiplex systems with 140 GHz channel spacing and 32 nm channel selection bandwidth.

The appearance of an S-shaped negative differential resistance (NDR) in GaInP/AlGaInP quantum well (QW) lasers has been observed in both single and multi-QW devices at temperatures between 100 and 200 K. Light–current (L–I) and current–voltage (I–V) relationships have been measured in detail at temperatures from 100 to 250 K, using three QW samples with different values of cladding layer thickness (1.0, 0.5 and 0.3 μm). The dependence of the S-shaped NDR characteristics on cladding thickness and laser output intensity shows that the high resistivity p-cladding layer is the cause of NDR. It is because of the impact ionisation of impurities in the p-cladding layer that an S-shaped NDR is produced. An impurity ionisation energy of ∼62 meV in p-type (Al0.7Ga0.3)0.52In0.48P is obtained from the I–V curve, which is consistent with that obtained from a hydrogenic model and accepted values.

The first passive e-switched operation is reported of an InGaAs/AlGaInAs diode laser with a frequency repetition ranging from 1 to 2.5GHz at the emitting wavelength of 1.58 mu m. This material is important as a thermally stable alternative to InGaAsP based laser systems operating around 1.5 mu m.