Optical readout within microfluidic chips is a bottleneck limiting their industrial development. The integration of lasers operating in the visible range within a microfluidic platform is crucial for enabling in situ optical measurements in lab‐on‐a‐chip applications. In principle, microstructured single‐crystal silicon is an excellent optofluidic platform, which allows integration of microfluidic channels together with optical circuits including micro‐optics, waveguides, and resonant cavities. However, the silicon absorption below 1.1 µm is a fundamental limit that prohibits the use of silicon‐based microcavities as the feedback element for visible lasers and restricts their use to the infrared only. In this work, an ultra‐wide band silicon cavity enabled by two deeply etched hollow‐core planar waveguides is demonstrated. The proposed microcavity shows a broad bandwidth extending from 500 to 1600 nm with quality factors up to 2067. A tubular microfluidic channel is inserted between the mirrors of the optofluidic cavity. The microfluidic channel is filled with Rhodamine 6G (R6G) at 20 µL min−1 flow rate allowing successful demonstration of lasing on silicon at 562.4 nm. The laser beam propagates in‐plane (along the chip surface) and is handled with monolithically integrated input/output optical fiber grooves. This provides a unique silicon platform integrating hollow core optofluidic channels together with optical cavities, which is suitable for implementing optical readout in lab‐on‐a‐chip devices.

Irregular easy axis reorientation features are observed in numerical simulations of the nanomagnet coupled to the Josephson junction. We study magnetization bifurcations and chaos that appear in this system due to the interplay of superconductivity and magnetism. The bifurcation structure of magnetization under the variation of Josephson to magnetic energy ratio as a control parameter demonstrates several precessional motions that are related to chaotic behavior and orbits with different periodicities in the ferromagnetic resonance region. The effect of an external periodic signal on the bifurcation structure is also investigated. The results demonstrate high-frequency modes of a periodic motion and a chaotic response near resonance. Far from the ferromagnetic resonance, we observe a quasiperiodic behavior. The obtained results explain the irregular reorientation of the easy axis and the transitions between different types of motion.

No abstract

We study the microwave-induced magnetization reversal in two systems, the microwave-driven nanomagnet (NM-MW) and the nanomagnet coupled to a Josephson junction under the microwave field (NM-JJ-MW). The frequency of the applied cosine chirp pulse (CCP) changes nonlinearly with time to match the magnetization precession frequency. The coupling between the nanomagnet and Josephson junction reduces the magnetization switching time as well as the optimal amplitude of the microwave field as a result of manipulating the magnetization via Josephson-to-magnetic energy ratio G. The reversal effect in NM-JJ-MW is sufficiently robust against changes in pulse amplitude and duration. In this system, the increase of G decreases the possibility of the non-reversing magnetic response as the Gilbert damping increases without further increase in the external microwave field. We also discuss the magnetic response of the nanomagnet driven by the ac field of two Josephson junctions in which the time-dependent frequency is controlled by the voltage across the junctions. Our results provide a controllable scheme of magnetization reversal that might help to realize fast memory devices.

No abstract