A groove GaInAsP laser on semi-insulating InP using a laterally diffused junction

Low threshold current GaInAsP/InP groove lasers have been fabricated on semi-insulating InP substrates. Three n-type layers are grown with a single liquid phase epitaxial (LPE) growth process, and the p-n junction is formed by a lateral Zn diffusion. The active layer inside the groove provides a real index waveguide. Threshold currents as low as 14 mA with 300 μm cavity length are obtained. A single longitudinal mode at 1.3 μm up to1.4 I_{TH}is observed. The lasers operate with a single lateral mode when the active region width is less than 2.5 μm. This laser is suitable for monolithic integration with other optoelectronic devices

Experimental search for anisotropic flux flow resistivity in the a-b plane of optimally doped epitaxial thin films of YBCO

Transport measurements along the node and anti-node directions in the a-b plane of optimally doped and epitaxial thin films of YBCO are reported. Low bias magnetoresistance measurements near and below T_c show that the flux flow resistivity along the node and anti-node directions versus magnetic field are indistinguishable. This result suggests that within the experimental error of our measurements, no correspondence is found between the flux pinning properties in YBCO and the d-wave nature of the order parameter.Comment: 5 figure

Evidence for Induced Magnetization in Superconductor-Ferromagnet Hetero-structures: a Scanning Tunnelling Spectroscopy Study

We performed scanning tunneling spectroscopy of c-axis oriented YBCO films on top of which ferromagnetic SRO islands were grown epitaxially in-situ. When measured on the ferromagnetic islands, the density of states exhibits small gap-like features consistent with the expected short range penetration of the order parameter into the ferromagnet. However, anomalous split-gap structures are measured on the superconductor in the vicinity of ferromagnetic islands. This observation may provide evidence for the recently predicted induced magnetization in the superconductor side of a superconductor/ ferromagnet junction. The length scale of the effect inside the superconductor was found to be an order of magnitude larger than the superconducting coherence length. This is inconsistent with the theoretical prediction of a penetration depth of only a few superconducting coherence lengths. We discuss a possible origin for this discrepancy

Mode stabilized terrace InGaAsP lasers on semi-insulating InP

Mode stabilized terrace InGaAsP lasers have been fabricated on semi-insulating InP substrates. The fabrication involves a selective, single-step liquid phase epitaxial growth process, and a lateral Zn diffusion. Two versions of the terrace lasers are fabricated, and threshold currents as low as 35 mA and 50 mA respectively are obtained. The lasers operate with a stable single lateral mode. High power performance is observed. These lasers are suitable for monolithic integration with other optoelectronic devices

Low threshold InGaAsP/InP lasers with microcleaved mirrors suitable for monolithic integration

Low threshold InGaAsP/InP injection lasers on semi-insulating InP substrates have been developed with mirrors fabricated by the microcleavage technique. Miniature suspended bridges containing the laser channels have been formed and then microcleavage has been accomplished by the use of ultrasonic vibrations. Lasers with current thresholds as low as 18 mA with 140-µm cavity length and with 35–45% differential quantum efficiency have been obtained

Monolithic integration of a very low threshold GaInAsP laser and metal-insulator-semiconductor field-effect transistor on semi-insulating InP

Monolithic integration of 1.3-µm groove lasers and metal-insulator-semiconductor field-effect transistors (MISFET) is achieved by a simple single liquid phase epitaxy (LPE) growth process. Laser thresholds as low as 14 mA for 300-µm cavity length are obtained. MIS depletion mode FET's with n channels on LPE grown InP layer show typical transconductance of 5–10 mmho. Laser modulation by the FET current is demonstrated at up to twice the threshold current

Phases of a two dimensional large N gauge theory on a torus

We consider two-dimensional large N gauge theory with D adjoint scalars on a torus, which is obtained from a D+2 dimensional pure Yang-Mills theory on T^{D+2} with D small radii. The two dimensional model has various phases characterized by the holonomy of the gauge field around non-contractible cycles of the 2-torus. We determine the phase boundaries and derive the order of the phase transitions using a method, developed in an earlier work (arxiv:0910.4526), which is nonperturbative in the 'tHooft coupling and uses a 1/D expansion. We embed our phase diagram in the more extensive phase structure of the D+2 dimensional Yang-Mills theory and match with the picture of a cascade of phase transitions found earlier in lattice calculations (arxiv:0710.0098). We also propose a dual gravity system based on a Scherk-Schwarz compactification of a D2 brane wrapped on a 3-torus and find a phase structure which is similar to the phase diagram found in the gauge theory calculation.Comment: 28 pages (+ 17 pages of appendix + 6 pages of ref.); 8 figures; (v2) LaTeX Showkeys command deleted; (v3) refs and minor clarifications added; emphasized the new proposal for applying holography to nonsupersymmetric gauge theory; (v4) modified the arguments about holography; (v5) minor corrections, version appeared in PR