Μm AlGaInAs Research Articles

Design and Optimization of 1.55 μm AlGaInAs MQW Polarization Mode Controllers

A 1.55 μm AlGaInAs multi-quantum-well (MQW) ridge waveguide polarization mode controller (PMC) is proposed. The design is based on an asymmetric half-ridge waveguide structure in which the ridge is shallow etched on one side and has a deeply etched mesa structure on the other side. The Finite-Element Method (FEM) was used to simulate the PMC and optimize its structural parameters comprehensively. Furthermore, the fabrication tolerances were also investigated in detail. The optimized PMC has a polarization conversion efficiency (PCE) of around 92.5% with a half-beat length of 1250 μm. When the PMC length was fixed at 1250 μm, to achieve a PCE derivation less than 8%, the tolerances for the ridge waveguide width and shallow etch height were 1.60 μm to 1.65 μm and 2.13 μm to 2.18 μm, respectively. In order to reduce interband gap absorption loss, the quantum well intermixing (QWI) technique was used in the model to realize a blueshift (200 nm) in the PMC. QWI is a simple, flexible, and low-cost technique for fabricating a PMC integrated with a laser diode and reduces parasitic reflections, which would otherwise degrade the overall performance. QWI also eliminates MQW material anisotropy and alleviates the birefringence effect without the need for regrowth, achieving nearly uniform properties as a bulk material.

Investigation of 1.3 μm AlGaInAs multi‐quantum wells for electro‐absorption modulated laser

Monolithic photonic integrated circuits (PIC) transmitters using the prefixed optical phase switching concept for BPSK modulation format have been shown promising at 1.55 μm band. These devices could also be crucial for short reach connections and access networks. With this aim, we are studying basic quantum well designs for a laser and an electro‐absorption modulator switch to be integrated by selective area growth into PICs at 1.3 μm. Photocurrent measurements and band offset modeling have been performed to determine the MQW stack well‐fitted for this application. Broad area laser measurements have also been checked on these structures to verify the material lasing properties. A 6 nm thick well with low barrier seems to be the best trade‐off between absorption and shift for 1.3 μm EAM and it also gives good lasing properties.

160 GHz Passively Mode-Locked AlGaInAs 1.55 μm Strained Quantum-Well Lasers With Deeply Etched Intracavity Mirrors

We have characterized the reflectivity, modal discrimination, and passive mode locking performance of diode lasers with intracavity reflectors (ICR) composed of a different number of slots. Upon analysis, we demonstrate that a monolithic semiconductor mode-locked laser comprising a compound cavity formed by a single deeply etched ICR slot fabricated using the 1.55 μm AlGaInAs strained quantum-well material provides the best harmonic (M = 4) mode-locking performance, with Gaussian-pulses generated at a pulse repetition rate of 161.8 GHz and a pulse duration of 1.67 ps, providing a time-bandwidth product of 0.81.

Uncooled, low-driving-current 25.8 Gbit/s direct modulation using 1.3 [micro sign]m AlGaInAs MQW distributed-reflector lasers

Uncooled, low-driving-current 25.8 Gbit/s direct modulation with clear eye-opening up to 85°C is demonstrated using 1.3 µm AlGaInAs multiple quantum well (MQW) distributed-reflector lasers. The peak driving currents were as low as 30.0 and 38.9 mA at 25 and 85°C, respectively.

160 GHz harmonic mode-locked AlGaInAs 155μm strained quantum-well compound-cavity laser

We characterized the reflectivity and the modal discrimination of intracavity reflectors (ICRs) with different numbers of slots and presented harmonic mode-locking operation of a monolithic semiconductor laser comprising a compound cavity formed by a single deeply etched slot ICR fabricated from 1.55 μm AlGaInAs strained quantum well material. Gaussian pulses were generated at a 161.8 GHz repetition rate with a pulse duration of 1.67 ps and a time-bandwidth product of 0.81.

Dependence of facet stress on reliability of AlGaInAs edge-emitting lasers

The relationship between facet stress and reliability of AlGaInAs edge-emitting lasers is unclear despite it being an important issue. We prepared two 1.3 μm AlGaInAs Fabry–Pérot buried-heterostructure (BH) lasers that were identical except that they had tensile and compressive stress at the facet. The magnitude of the facet stress was controlled to be approximately 200 MPa in both lasers. We performed three reliability tests. In forward-biased electrostatic discharge tests, which can evaluate the resistance to optical damage, the cumulative degradation ratio of the compressive stressed laser was 33% lower than that of the tensile stressed laser. This result indicates a reduction in the optical absorption due to enlargement of the energy band gap at the facet. In the long-term aging of the light output power of 8 mW at 85 °C over 5 000 h, no dependence of the facet stress on the lifetime was observed. Since a major limitation of InP-based BH lasers is the BH interface, the aging results are reasonable. In the accelerated aging of a large current of 200 mA at 85 °C over 800 h, degradation (defined as an increase in the threshold current of over 10%) was observed only in the tensile stressed laser. This degradation differed completely from that caused by optical absorption; dislocation loops covered the entire active layer at the facet. To the best of our knowledge, this is the first time such degradation has been reported. We found the degradation depends on the facet stress and that compressive stress can suppress the degradation.

Electrostatic-discharge-induced degradation of 1.3μm AlGaInAs∕InP buried heterostructure laser diodes

Degradation of 1.3μm AlGaInAs buried heterostructure laser diodes due to electrostatic discharge (ESD) is studied. The degradation mechanism of this material has not previously been clear and so the ESD tolerance was evaluated. Degradation occurred at 0.5 and 2.5kV for forward and reverse polarities, respectively. Because that ESD tolerance for forward polarity is insufficient for practical applications, we focused on it in analyzing the degradation mechanism. Elliptically shaped melted regions are observed in the active layer of the facet. Such regions developed inside a cavity under the application of ESD pulses. These results indicate that degradation is caused by melting due to optical absorption.

High-Temperature and High-Frequency Operation of 1.3 μm AlGaInAs ∕ InP Laser Diodes Using Silicon Oxide Planarization

In this article, a self-terminated oxide polish (STOP) planarization technique is utilized to fabricate high-temperature and high-speed ridge-waveguide laser diodes (LDs). The as-cleaved LDs fabricated by this STOP technique exhibit a threshold current of 8.5 and , and a light output power of 27 and at for 0 and , respectively. The characteristic temperature is from 0 to and from 80 to . The full width at half maximum of the lateral far-field angle is for the conventional ridge LDs and reduces to for the LDs by the STOP technique. The modulation bandwidth at of the LDs can reach 16.9 at and at .

Numerical Study on Optimization of Active Regions for 1.3 µm AlGaInAs and InGaAsN Material Systems

The peak material gains of 1.3 µm semiconductor material systems are numerically studied with a LASTIP simulation program. Specifically, the optical properties of the AlGaInAs and InGaAsN material systems are investigated. Simulation results suggest that, using a p-type AlInAs electron stopper layer, improved temperature dependence of slope efficiency in the operating temperature range from 25 to 85 °C can be obtained for a ridge-waveguide AlGaInAs/InP laser structure. On the other hand, using a strain-compensated active region consisting of In0.36Ga0.64As0.99N0.01 (6 nm)/GaAs0.99N0.01 (10 nm), a high laser performance and stimulated emission characteristics can be achieved for a ridge-waveguide InGaAsN/GaAs laser structure.

Effects of n-type modulation-doping barriers and a linear graded-composition GaInAsP intermediate layer on the 1.3μm AlGaInAs∕AlGaInAs strain-compensated multiple-quantum-well laser diodes

We report the fabrication, characterization, and comparison of four 1.3μm AlGaInAs∕AlGaInAs strain-compensated multiple-quantum-well (SC-MQW) laser structures: (1) sample A—with only an undoped SC-MQW active region, (2) sample B—with an undoped SC-MQW active region and a linear graded-composition (LGC) GaInAsP intermediate layer, (3) sample C—with an n-type modulation-doping (MD) SC-MQW active region, and (4) sample D—with an n-type MD-SC-MQW active region combined with a LGC GaInAsP intermediate layer. The inclusion of either n-type modulation-doped SC-MQW active region or LGC GaInAsP intermediate layer can improve the performance of a laser diode (LD). The LD sample D, which includes both an n-type MD-SC-MQW active region and a LGC GaInAsP intermediate layer, exhibits the best overall performance including a threshold current of 12.5mA, a characteristic temperature of 85K in 20–80°C temperature range, a lasing wavelength shift of 0.38nm∕K, and a relaxation frequency response of 9.9GHz.

Reliability analysis of AlGaInAs lasers at 1.3 [micro sign

Long-term reliability of 2.5 and 10 Gbit/s 1.3 µm AlGaInAs lasers has been demonstrated. Analysis of accelerated life test predicts median life of ≥1.57×106 h (180 years) at 85°C.

Effect of InGaAsP intermediate layer in 1.3 μm AlGaInAs strain-compensated multiple quantum well laser diodes

The effect is investigated of introducing a linearly graded-index separate-confinement-heterostructure InGaAsP intermediate layer between the InGaAs cap layer and the InP cladding layer to improve the characteristics of 1.3 μm AlGaInAs strain-compensated multiple-quantum-well laser diodes (LDs). With the InGaAsP intermediate layer, 3 μm-ridge-strip LDs without facet coating under CW operation exhibit a threshold current of 16 mA, a resistance of 5.8 Ω, a characteristic temperature of 75 K in the range 20–70°C and 41 K at 70–100°C, a differential quantum efficiency of 50% and a low slope efficiency drop of −1.3 dB between 20 and 70°C. These characteristics are better than those of LDs without the InGaAsP intermediate layer. A wavelength swing of 0.48 nm/°C for LDs operated at 50 mA is achieved.

Wavelength dependence of the modal refractive index in 1.3 μm InGaAsP, AlGaInAs and GaInNAs lasers using high pressure

AbstractWe report the variation of the modal refractive index at threshold with lasing wavelength in 1.3 μm InGaAsP, AlGaInAs and GaInNAs multiple quantum well lasers by measuring mode spectra under pressure up to 15 kbar. It is shown that the decrease of index with lasing wavelength is about 4% on average in the pressure range studied. We also find that the modal refractive index reduces with increasing injection current and is very sensitive to the injection current around laser threshold.

Improved temperature dependence of 1.3 [micro sign]m AlGaInAs-based MQW semiconductor diode lasers revealed by hydrostatic pressure

The threshold current Ith of 1.3 µm AlGaInAs devices increases by ~8% over a 1 GPa pressure range contrasting with decreases of 10–15% in 1.3 µm InGaAsP devices. This can be explained with 50% nonradiative recombination in InGaAsP and only ~20% in AlGaInAs devices, resulting in a much improved temperature dependence of Ith.

Molecular-beam-epitaxy growth of strained Ga 1− x In xAs/AlInAs/InP and application to 1.55 μm multi-quantum-well lasers

Dependence of critical layer thickness ( h c ) and photoluminescence (PL) intensity on growth temperature ( T g ) was investigated for 1% compressively strained Ga 0.32In 0.68As/AlInAs on InP. We found, for the first time, a strong T g dependence of h c in this system with h c of 24 nm at 500°C and 14 nm at 530°C. The PL intensity increased with T g , reaching a maximum at 530°C. We fabricated 1.55 μm multi-quantum-well (MQW) lasers with 1% compressively strained wells under optimized growth conditions. Threshold current density as low as 1.08 kA/cm 2 at a cavity length of 800 μm was obtained. This threshold current density is one of the lowest values obtained for 1.55 μm AlGaInAs MQW lasers grown by molecular beam epitaxy (MBE).

Molecular beam epitaxy growth of lattice-matched [formula omitted] multiple quantum well distributed feedback laser structures with gratings defined by implantation enhanced intermixing

AlGaInAs GaInAs multiple quantum wells (MQWs) are particularly suited for planar device integration using local refractive index modification by masked implantation enhanced intermixing (MIEI). Suitable molecular beam epitaxy (MBE) growth conditions are elaborated to achieve 1.3 μm AlGaInAs GaInAs MQW distributed feedback (DFB) lasers taking advantage of the capability of the MIEI process to define the gratings. High-quality MBE overgrowth on AlGaInAs necessary for device completion after H ∗ radical treatment is demonstrated.