InGaAs-InGaAsP buried heterostructure lasers operating at 2.0 μm

Buried heterostructure lasers with highly strained InGaAs-InGaAsP active regions, emitting at 2 μm have been fabricated and tested. The lasers exhibited threshold current densities of 500 A/cm² for 1-mm-long cavities, an internal loss of 11 cm^-1, and characteristic temperatures as high as 50°C. The gain characteristics were also investigated and a linewidth enhancement factor of 8 was determined     

Définition théorique des paramètres en fort niveau d’un multipôle actif non linéaire

In this paper, large signal non linear P parameters are rigorously defined, allowing the characterization of non linear active n-port circuits in the frequency domain with the aim of computer aided design of power microwave devices. No a priori conditions bind the parameters to the variables describing the input signal. However the following rules apply to the parameters: they may be function of any input variables of the n-port circuit; the expression of the large-signal parameters should become identical to the expression of the linear parameters characterizing the n-port circuit under linear operating conditions when the values of the input variables tend to zero. An application of the definition to afet is demonstrated.     

Current Distribution and Nonlinearity of Open-Ends and Gaps in Superconducting Microstrip Structures

Superconducting devices are known to produce nonlinear effects. In planar structures, these nonlinearities depend on the current distribution on the strip, which definitely depends on the structure of device. This paper used a numerical method based on 3D-FEM to obtain the current distribution in the open-ends and gaps in the superconducting microstrip structures. This is used to present the nonlinear distributed circuit modeling of these discontinuities and its impact on the nonlinear phenomenon. This nonlinear circuit model is used in the Harmonic Balance (HB) method to analyze nonlinearity in the superconducting microwave devices. Therefore, this simple accurate enough nonlinear circuit model is warmly welcomed to retire the seemingly inevitable use of time- and memory-consuming numerical techniques for nonlinear analysis of discontinuities in superconducting microwave structures. As an example, we analyze a microstrip superconducting end-coupled band pass filter (BPF). These results are very useful for optimizing the resonators of the superconducting microwave filters in order to minimize its nonlinear distortions.     

High-power operation of highly reliable narrow stripe pseudomorphicsingle quantum well lasers emitting at 980 nm

Ridge waveguide pseudomorphic InGaAs/GaAs/AlGaAs single-quantum-well lasers exhibiting record high quantum efficiencies and high output power densities (105 mW per facet from a 6 μm wide stripe) at a lasing wavelength of 980 nm are discussed that were fabricated from a graded index separate confinement heterostructure grown by molecular beam epitaxy. Life testing at an output power of 30 mW per uncoated facet reveals a slow gradual degradation during the initial 500 h of operation after which the operating characteristics of the lasers become stable. The emission wavelength, the high output power, and the fundamental lateral mode operation render these lasers suitable for pumping Er³⁺-doped fiber amplifiers     

Laterally coupled InGaAsP/InP distributed feedback lasers at 1.5μm for chemical sensing applications

Data is presented on stable, tunable single-mode operation from laterally coupled InGaAsP/InP ridge waveguide distributed feedback lasers at ~1.5 μm, suitable for chemical sensing, realised by a greatly simplified fabrication process requiring a single MOCVD growth step. Completed lasers show sidemode suppression ratios as high as 47 dB and wavelength shifts with injection current of 0.035 nm/mA (or 4.5 GHz/mA)     

A perturbation and iterative perturbation analysis of linearly chirped grating lenses of medium Q in dielectric waveguides

A perturbation and iterative perturbation analysis of linearly chirped quasi-periodic structures of mediumQfactor in planar dielectric waveguides has been formulated. This analysis can be used to calculate the diffraction efficiency and the angular field of view of a given linearly chirped grating structure, for a specific incident beam including the effect of higher orders of diffractions. The numerical example of aF = 10 , f = 10m.m,Lambda_{min} = 2.06, Lambda_{max} = 4.25and grating groove length = 15 μm is presented.     

CW performance of an InGaAs-GaAs-AlGaAs laterally-coupleddistributed feedback (LC-DFB) ridge laser diode

Single-mode distributed feedback (DFB) laser diodes typically require a two-step epitaxial growth or use of a corrugated substrate. We demonstrate InGaAs-GaAs-AlGaAs DFB lasers fabricated from a single epitaxial growth using lateral evanescent coupling of the optical field to a surface grating etched along the sides of the ridge. A CW threshold current of 25 mA and external quantum efficiency of 0.48 mW/mA per facet were measured for a 1 mm cavity length device with anti-reflection coated facets. Single-mode output powers as high as 11 mW per facet at 935 nm wavelength were attained. A coupling coefficient of at least 5.8 cm^-1 was calculated from the subthreshold spectrum taking into account the 2% residual facet reflectivity     

C2F6reactive ion-beam etching of LiNbO3and Nb2O5and their application to optical waveguides

Properties of C2F6(freon 116) reactive ion-beam etching (RIBE) of LiNbO3, Ti-indiffused LiNbO3, and sputter-deposited Nb2O5film on LiNbO3are reported. A maximum differential etching ratio of approximately 5:1 has been measured for LiNbO3and the AZ 1350B Shipley photoresist. We have used this etching technique to fabricate diffraction gratings on both Ti-indiffused LiNbO3and Nb2O5- LiNbO3waveguides with measured throughput efficiencies in excess of 85 percent.     

A Proposed Equivalent Channel Power Delay Profile for a Millimeter Wave Wireless OFDM System and Optimum Guard Interval Evaluation in a Built-Up Area Propagation Scenario

Vertical plane launching ray tracing method has been applied for a real urban scenario and the delay characteristics of received signals in the overall coverage area have been extracted. Using these parameters, an equivalent channel power delay profile (ECPDP) has been introduced for the overall coverage area. For a millimeter wave wireless OFDM system, the optimum guard interval length which maximizes the mean of signal to interference and noise ratio has been simulated. Also, using the proposed ECPDP, the optimum guard interval length has been analytically extracted and compared with the simulated one.