Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userStrong coupling-enabled broadband non-reciprocity
105
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Non-reciprocity of signal transmission enhances capacity of communication channels and protects transmission quality against possible signal instabilities, thus becoming an important component ensuring coherent information processing. However, non-reciprocal transmission requires breaking time-reversal symmetry (TRS) which poses challenges of both practical and fundamental character hindering the progress. Here we report a new scheme for achieving broadband non-reciprocity using a specially engineered hybrid microwave cavity. The TRS breaking is realized via strong coherent coupling between a selected chiral mode in the microwave cavity and a single collective spin excitation (magnon) in a ferromagnetic yttrium iron garnet (YIG) sphere. The non-reciprocity in transmission is observed spanning nearly a 0.5 GHz frequency band, which outperforms by two orders of magnitude the previously achieved bandwidths. Our findings open new directions for robust coherent information processing in a broad range of systems in both classical and quantum regimes.
rate research
Read More
The Brewsters law predicts zero reflection of p-polarization on a dielectric surface at a particular angle. However, when loss is introduced into the permittivity of the dielectric, the Brewster condition breaks down and reflection unavoidably appears. In this work, we found an exception to this long-standing dilemma by creating a class of nonmagnetic anisotropic metamaterials, where an anomalous Brewster effects with independently tunable absorption and refraction emerges. This loss-independent Brewster effect is bestowed by the extra degrees of freedoms introduced by anisotropy and strictly protected by the reciprocity principle. The bandwidth can cover an extremely wide spectrum from dc to optical frequencies. Two examples of reflectionless Brewster absorbers with different Brewster angles are both demonstrated to achieve large absorbance in a wide spectrum via microwave experiments. Our work extends the scope of Brewster effect to the horizon of nonmagnetic absorptive materials, which promises an unprecedented wide bandwidth for reflectionless absorption with high efficiency.
Similarly to their purely electric counterparts, spintronic circuits may be presented as networks of lumped elements. Due to interplay between spin and charge currents, each element is described by a matrix conductance. We establish reciprocity relations between the entries of the conductance matrix of a multi-terminal linear device, comprising normal metallic and strong ferromagnetic elements with spin-inactive interfaces between them. In particular, reciprocity equates the spin transmissions through a two-terminal element in the opposite directions. When applied to geometric spin ratchets, reciprocity shows that certain effects, announced for such devices, are, in fact, impossible. Finally, we discuss the relation between our work and the spintronic circuit theory formalism.
Phase change materials (PCMs) have long been used as a storage medium in rewritable compact disk and later in random access memory. In recent years, the integration of PCMs with nanophotonic structures has introduced a new paradigm for non-volatile reconfigurable optics. However, the high loss of the archetypal PCM Ge2Sb2Te5 in both visible and telecommunication wavelengths has fundamentally limited its applications. Sb2S3 has recently emerged as a wide-bandgap PCM with transparency windows ranging from 610nm to near-IR. In this paper, the strong optical phase modulation and low optical loss of Sb2S3 are experimentally demonstrated for the first time in integrated photonic platforms at both 750nm and 1550nm. As opposed to silicon, the thermo-optic coefficient of Sb2S3 is shown to be negative, making the Sb2S3-Si hybrid platform less sensitive to thermal fluctuation. Finally, a Sb2S3 integrated non-volatile microring switch is demonstrated which can be tuned electrically between a high and low transmission state with a contrast over 30dB. Our work experimentally verified the prominent phase modification and low loss of Sb2S3 in wavelength ranges relevant for both solid-state quantum emitter and telecommunication, enabling potential applications such as optical field programmable gate array, post-fabrication trimming, and large-scale integrated quantum photonic network.
Light-matter interactions can occur when an ensemble of molecular resonators is placed in a confined electromagnetic field. In the strong coupling regime the rapid exchange of energy between the molecules and the electromagnetic field results in the emergence of hybrid light-matter states called polaritons. Multiple criteria exist to define the strong coupling regime, usually by comparing the splitting of the polariton bands with the linewidths of the uncoupled modes. Here we highlight the limitations of these criteria and study strong coupling using spectroscopic ellipsometry, a commonly used optical characterisation technique. We identify a new signature of strong coupling in ellipsometric phase spectra. Combining ellipsometric amplitude and phase spectra yields a distinct topological feature that we suggest could serve as a new criterion for strong coupling. Our results introduce the idea of ellipsometric topology and could provide further insight into the transition from the weak to strong coupling regime.
It is well known that optical absorption saturation of intersubband transitions in doped semiconductor quantum wells is independent of the introduced doping in the absence of a cavity. When inserting the system in a resonator, we show that this remains valid only in the weak light-matter coupling regime. In the strong light-matter coupling regime instead, we demonstrate that absorption saturation is no more doping independent and it is instead tailorable. Based on this unified formalism for saturation in weak and strong coupling, we provide designs for semiconductor saturable absorption (SESAM) mirrors and bistable systems operating in the mid-infrared range of the electromagnetic spectrum and with extremely low saturation intensities. Countering intuition, we show that the most suitable region to exploit low saturation intensities is not the ultra-strong coupling regime, but is instead at the onset of strong light-matter coupling.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
