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We have studied n- and p-type doping-induced performance degradation of AlAs/GaAs distributed Bragg reflectors (DBRs) for applications in vertical cavity lasers (VCLs). Based on high-accuracy optical reflectance and triple-axis x-ray diffraction measurements on a variety of differently doped DBR structures grown by metalorganic vapor-phase epitaxy, a fitting procedure was employed to extract the doping-dependent optical loss. A striking observation is that the reflectance of these DBRs is much more sensitive to n- than p-type doping incorporation. While in the latter case the loss can be well accounted for by intervalence-band and free-carrier absorption, additional loss mechanisms must be considered for n-type DBRs. We relate the losses to doping-enhanced interdiffusion effects resulting in increased interface scattering. These findings should have important consequences for the design of VCLs, demonstrating the importance of reduced n-type doping concentrations and/or growth temperatures, or the application of alternative device concepts, e.g., employing intracavity contacts. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents a study which reported the successful carbidation of titanium in a layer forming on the surface of a titanium sample submitted to multipulse excimer laser treatment in methane at a slightly superatmospheric pressure. Background on titanium carbide; Description of the experimental setup; Results.

Proposes a new laser method for the deposition of high purity, hard fcc titanium nitride layers of unlimited thickness. Requisite for titanium nitride formation; Results of electron microscopy investigations.

Examines an evidence of refractive index change by thallium (TI) indiffusion into LiNbO[sub3] substrate as a result of multipulse free-running ruby laser irradiation. Analysis of thermal behavior of the structures under the action of the free-running ruby laser irradiation; Description of the visual and optical microscopy evidence; Impact of TI implantation on the ordinary refractive index value.

This article reports on a modified cavity phase-shift (CAPS) method for accurate and reliable characterization of high reflectance mirrors. Our approach relies on using a directly modulated Fabry-Pérot laser to circumvent the difficulties encountered in previous attempts with the CAPS method. The Fabry-Pérot laser diode ensures a constant coupling between the probe laser and test cavity modes. This results in a stable beam intensity transmitted through the test cavity allowing for accurate measurements of the phase shift from which the absolute reflectance can be determined. The experimental arrangement presented in this article is versatile and easy to use. The method is nondestructive and especially suited for the characterization of distributed Bragg reflectors (DBRs) employed in vertical-cavity optoelectronic devices. A premium feature of this method is its capability to probe a relatively small area of less than 1 mm which can be positioned anywhere across the surface of the wafer. We demonstrate the use of the method by measuring the absolute reflectance of metalorganic vapor-phase epitaxy grown AlAs/GaAs DBRs for 1.3 µm vertical-cavity lasers. [ABSTRACT FROM AUTHOR]

The authors report the design and fabrication of micromechanically tunable filters using a novel stable resonator geometry. The filters consist of a 1λ air-gap cavity with two InP/air-gap Bragg reflectors. The design of the micromechanical structure ensures a stable resonator geometry under actuation that provides constant performance throughout the entire tuning range of 65 nm. The devices are micromachined from a monolithic all epitaxial InP-InGaAs structure that can be integrated with an InP-based photo detector or emitter in a low-cost component for coarse wavelength division multiplexing systems operating in the 1.3 or 1.55 μm band [ABSTRACT FROM PUBLISHER]

The properties of 1.2-µm highly strained InGaAs quantum wells (QWs) grown on GaAs substrates have been analyzed. Optical gain spectra versus injection current and temperature, transparency current density, as well as other figures of merit were assessed from measurements on broad-area and ridge-waveguide lasers based on these QWs. Such active regions are of interest for a range of applications, including GaAs-based high-power lasers and vertical-cavity lasers for wavelengths beyond 1.2 µm. [ABSTRACT FROM AUTHOR]

We demonstrate a long wavelength (λ=1.56 μm) vertical-cavity laser built on a low-loss resonator formed by two InP/air-gap Bragg reflectors. The monolithic, InP-based structure uses a periodic gain active region with six strain-compensated quantum wells. The photopumped vertical-cavity laser requires record low power density of only 370 W/cm2 to reach threshold at 25 °C. The equivalent threshold current density is estimated to be as low as 400 A/cm2. Continuous-wave operation is demonstrated up to 32 °C despite the low heat conductivity of the reflectors. The emission is single mode and a power of up to 110 μW has been coupled into a single-mode fiber. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report the design and fabrication of micromechanically tunable filters with a 10-nm bandwidth for the 1550-nm wavelength range. The electrostatic actuation provides a tuning range of 30 nm and a low actuation power. The filters consist of a monolithic, vertical Fabry-Perot resonant cavity based on an epitaxial InGaAsP-InP Bragg reflector. An actuable InP micromechanical structure suspended over a 1×-thick air-gap provides for the tuning of the cavity. Our design aims primarily for a device that is simple, robust and that can be integrated with an InP-based photodetector or emitter in a low-cost component for optical data interconnects [ABSTRACT FROM PUBLISHER]

We have investigated the residual stress distribution and its relation to the presence of impurity atoms in InP layers grown by metalorganic vapor phase epitaxy (MOVPE) on top of lattice-matched GaInAs layers. The homogeneous and gradient components of the stress have been directly measured using highly sensitive micromechanical test structures. Secondary ion mass spectrometry depth profiling of the composition evidenced that residual As and Ga atoms are present throughout the relatively thick (>0.5 μm) InP layers. Our investigations show that the distribution of these impurities accounts for the measured residual stress in the layers and, at the same time, it is specific to the MOVPE growth technique. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]