Apart from classical and anomalous Hall effects, an appearance of transverse current in chiral systems has been recently discovered named as topological Hall effect (THE) as it was thought to be possible solely for topologically charged spin textures such as magnetic skyrmions. In this talk we focus on asymmetric electron scattering on chiral spin textures and tunnel transport across a semiconductor interface with account for exchange and spin-orbit interactions. We distinguish between chiral Hall effect (CHE) which requires local chirality of an effective magnetic field and the THE which requires also a non-zero topological charge. THE emerges in adiabatic regime of scattering, which can be described via geometrical Berry phase. With semi-classical approach we clarify why the spin Hall current in this case is proportional to the topological charge of a spin texture and does not depend on its size. For non-adiabatic regime we expand the scattering T-matrix in Born series and show that the scattering cross section acquires an asymmetric part, which depends on the local chirality of the spin texture leading to CHE independently of the topological charge. The analysis allowed us to clarify the reason for the spin Hall effect to vanish in this regime while preserving the charge Hall effect. We have also found theoretically the spin swapping effect for the exchange scattering on chiral spin textures. Further, with the T-matrix analysis we explain the asymmetry in the tunneling across a semiconductor interface emerging due to chiral configuration of exchange and spin-orbit fields leading to generation of transverse current.
We discuss wavelength stabilized all-epitaxial Tilted Cavity Lasers (TCLs). Optical cavity of a TCL favors propagation of only one tilted optical mode ensuring wavelength-selective operation. The possibility of full control of the thermal shift of the lasing wavelength d λ/dT in TCL
including positive, zero or negative shift, is proved theoretically. Broad-area
(100 μm) 970-nm-range devices have been fabricated showing a high temperature stability of the lasing wavelength
(0.13 nm/K), a high power operation (> 7 W in pulsed mode and > 1.5 W in continuous wave (cw) mode), and a narrow
vertical far-field beam divergence (FWHM ~ 20°). Single transverse mode edge-emitting 4 μm-wide-ridge TCLs
demonstrated high-power spatial and spectral single mode cw operation with a longitudinal side mode suppression ratio
(SMSR) up to 41.3 dB at 93 mW output power. Such a result is similar to the best values achieved for DFB lasers in the
same spectral range, while no etching and overgrowth is used in present case.
High concentration of optical power in a narrow exit angle is extremely important for numerous applications of laser diodes, for example, for low-cost fiber pumping and coupling, material processing, direct frequency conversion, etc. Lasers based on the longitudinal photonic band crystal (PBC) concept allow a robust and controllable extension of the fundamental mode over a thick multi-layer waveguide region to achieve a very large vertical optical mode spot size and, consequently, a very narrow vertical beam divergence. Many undesirable effects like beam filamentation, lateral multimode operation and catastrophic optical mirror damage (COMD) are strongly reduced. 650 nm GaInP/GaAlInP PBC lasers show narrow far field pattern (FWHM~7°) stable up to the highest output powers. Differential efficiency up to 85% is demonstrated. Total single mode output power as high as 150 mW is achieved in 4 μm-wide stripes in continuous wave operation, being limited by COMD due to not passivated facets. The lateral far field FWHM is 4 degrees. 840 nm GaAs/GaAlAs PBC lasers show a vertical beam divergence of 8° (FWHM) and a high differential efficiency up to 95% (L=500 μm). A total single mode CW power approaches 500 mW for 1 mm-long 4 μm-wide stripes devices at ~500 mA current, being COMD-limited. The lateral far field FWHM is 5 degrees. Another realization of a longitudinal PBC laser allows lasing in a single high-order vertical mode, a so-called tilted mode, which provides wavelength selectivity and substantially extends the possibility to control the thermal shift of the lasing wavelength. In a multilayer laser structure, where the refractive index of each layer increases upon temperature, it is possible to reach both a red shift of the lasing wavelength for some realizations of the structures, and a blue shift for some others. Most important, the absolute thermal stabilization of the lasing wavelength of a semiconductor laser can be realized.