Articles you may be interested inStrain relaxation of epitaxial ( Ba 0.6 Sr 0.4 ) ( Zr 0.3 Ti 0.7 ) O 3 thin films grown on SrTiO 3 substrates by pulsed laser deposition

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The interband cascade laser differs from any other class of semiconductor laser, conventional or cascaded, in that most of the carriers producing population inversion are generated internally, at semimetallic interfaces within each stage of the active region. Here we present simulations demonstrating that all previous interband cascade laser performance has suffered from a significant imbalance of electron and hole densities in the active wells. We further confirm experimentally that correcting this imbalance with relatively heavy n-type doping in the electron injectors substantially reduces the threshold current and power densities relative to all earlier devices. At room temperature, the redesigned devices require nearly two orders of magnitude less input power to operate in continuous-wave mode than the quantum cascade laser. The interband cascade laser is consequently the most attractive option for gas sensing and other spectroscopic applications requiring low output power and minimum heat dissipation at wavelengths extending from 3 µm to beyond 6 µm.

High quality ͑111͒ and ͑100͒ oriented Co/Pt superlattices have been prepared using the magnetron sputtering technique. The extraordinary Hall effect and magnetic properties in a series of these Co/Pt superlattices have been studied. We have established the existence of a large enhanced moment at the Co/Pt interfaces. Tensile strain in the magnetic layers is found to dominate the perpendicular magnetic anisotropy for the ͑111͒ orientation. From a systematic variation of the Co layer thickness we have determined that the extraordinary Hall resistivity is dominated by interface scattering. Further, large deviations from the commonly used scaling relations linking the extraordinary Hall resistivity and the ordinary resistivity are observed. These are discussed within a model proposed by Zhang.

We describe the use of a near-field scanning microwave microscope to quantitatively image the dielectric permittivity and tunability of thin-film dielectric samples on a length scale of 1 µm. We demonstrate this technique with permittivity images and local hysteresis loops of a 370 nm thick Ba0.6Sr0.4TiO3 thin film at 7.2 GHz. We also observe the role of annealing in the recovery of dielectric tunability in a damaged region of the thin film. We can measure changes in relative permittivity ǫr as small as 2 at ǫr = 500, and changes in dielectric tunability dǫr/dV as small as 0.03 V −1 .

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We review the history, development, design principles, experimental operating characteristics, and specialized architectures of interband cascade lasers for the mid-wave infrared spectral region. We discuss the present understanding of the mechanisms limiting the ICL performance and provide a perspective on the potential for future improvements. Such device properties as the threshold current and power densities, continuous-wave output power, and wall-plug efficiency are compared with those of the quantum cascade laser. Newer device classes such as ICL frequency combs, interband cascade vertical-cavity surface-emitting lasers, interband cascade LEDs, interband cascade detectors, and integrated ICLs are reviewed for the first time.

We describe the use of a near-field scanning microwave microscope to image the permittivity and tunability of bulk and thin film dielectric samples on a length scale of about 1 m. The microscope is sensitive to the linear permittivity, as well as to nonlinear dielectric terms, which can be measured as a function of an applied electric field. We introduce a versatile finite element model for the system, which allows quantitative results to be obtained. We demonstrate use of the microscope at 7.2 GHz with a 370 nm thick Ba 0.6 Sr 0.4 TiO 3 thin film on a LaAlO 3 substrate. This technique is nondestructive and has broadband ͑0.1-50 GHz͒ capability. The sensitivity of the microscope to changes in permittivity is ⌬⑀ r ϭ2 at ⑀ r ϭ500, while the nonlinear dielectric tunability sensitivity is ⌬⑀ 113 ϭ10 Ϫ3 ͑kV/cm͒ Ϫ1 .