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A fully-functional photonic integrated circuit (PIC) platform with supporting active and passive components in the extended short- and mid-wave infrared spectral regime is of significant research interest for next-generation optical systems. Here we design offset quantum well-based photonic integrated circuits which primarily consist of four section-based widely tunable single-mode lasers emitting at 2560 nm. The platform requires the selective removal of InGaAsSb multi-quantum wells located above a GaSb-based optical waveguide layer and then subsequent single blanket GaSb regrowth. Encouraging preliminary experimental results on regrowth are also reported to confirm the feasibility of the proposed PICs. The simulation result for the tunable laser design shows that a tuning range as wide as ~120 nm is possible. The quasi-theoretical work performed here is an initial step towards demonstrating complex non-telecommunication PICs which could offer a comprehensive range of photonic functionalities.

One-dimensional (1D) electronic transport and induced superconductivity in semiconductor nanostructures are crucial ingredients to realize topological superconductivity. Our approach for topological superconductivity employs a two-dimensional electron gas (2DEG) formed by an InAs quantum well, cleanly interfaced with an epitaxial superconductor (epi-Al). This epi-Al/InAs quantum well heterostructure is advantageous for fabricating large-scale nanostructures consisting of multiple Majorana zero modes. Here, we demonstrate transport studies of building-blocks using a high-quality epi-Al/InAs 2DEG heterostructure, which could be put together to realize various proposed 1D nanowire-based nanostructures and 2DEG-based networks that could host multiple Majorana zero modes. The studies include (1) gate-defined quasi-1D channels in the InAs 2DEG and (2) quantum point contacts for tunneling spectroscopy, as well as induced superconductivity in (3) a ballistic Al-InAs 2DEG-Al Josephson junction. From 1D transport, systematic evolution of conductance plateaus in half-integer conductance quanta is observed with Landé g-factor of 17, indicating the strong spin–orbit coupling and high quality of the InAs 2DEG. The improved 2DEG quality leads to ballistic Josephson junctions with enhanced characteristic parameters such as IcRnand IexcRn, the product of superconducting critical current Ic(and excess current Iexc) and normal resistance Rn. Our results of electronic transport studies based on the 2D approach suggest that the epitaxial superconductor/2D semiconductor system with improved 2DEG quality is suitable for realizing large-scale nanostructures for quantum computing applications.

In this study, we systematically investigated the anisotropic magnetoresistance (AMR) effect in half-metallic Co2MnSi Heusler alloy films epitaxially grown by molecular beam epitaxy. The fourfold symmetric AMR was observed in the temperature range of 25-275 K. In addition, the films exhibited a marked change in twofold symmetric AMR below 100 K. This specific temperature dependence of the AMR effect in Co2MnSi films can be caused by the tetragonal crystal field because of the distortion of the lattice at low temperatures. The influence of tetragonal distortion on both the AMR effect and half-metallicity is also discussed by first-principles calculations.