Unveiling the dynamical diversity of quantum dot lasers subject to optoelectronic feedback

This paper investigates experimentally and numerically the nonlinear dynamics of an epitaxial quantum dot laser on silicon subjected to optoelectronic feedback. Experimental results showcase a diverse range of dynamics, encompassing square wave patterns, quasi-chaotic states, and mixed waveforms exhibiting fast and slow oscillations. These measurements unequivocally demonstrate that quantum dot lasers on silicon readily and stably generate a more extensive repertoire of nonlinear dynamics compared to quantum well lasers. This pronounced sensitivity of quantum dot lasers to optoelectronic feedback represents a notable departure from their inherent insensitivity to optical feedback arising from reflections. Moreover, based on the Ikeda-like model, our simulations illustrate that the inherent characteristics of quantum dot lasers on silicon enable rapid and diverse dynamic transformations in response to optoelectronic feedback. The emergence of these exotic dynamics paves the way for further applications like integrated optical clocks, optical logic, and optical computing

High Thermoelectric Performance of a Heterogeneous PbTe Nanocomposite

In this paper, we propose a heterogeneous material for bulk thermoelectrics. By varying the quenching time of Na doped PbTe, followed by hot pressing, we synthesized heterogeneous nanocomposites, a mixture of nanodot nanocomposites and nanograined nanocomposites. It is well-known that by putting excess amounts of Na (i.e., exceeding the solubility limit) into PbTe, nanodots with sizes as small as a few nanometers can be formed. Nanograined regions with an average grain size of ca. 10 nm are observed only in materials synthesized with an extremely low quenching rate, which was achieved by using a quenching media of iced salt water and cold water. Dimensionless thermoelectric figures of merit, <i>zT</i>, of those heterogeneous nanocomposites exhibited a <i>zT</i> around 2.0 at 773 K, which is a 25% increase compared to <i>zT</i> of a homogeneous nanodot nanocomposite with the largest quenching time in our experiment, i.e. furnace cooled. The power factor increase is 5%, and the thermal conductivity reduction is 15%; thus, <i>zT</i> increase mainly comes from the thermal conductivity reduction

Re-tracing the past: mixing realities in museum settings

Interactive exhibits are now commonplace in museum settings, providing ‘edutainment’ for visitors. However, many technologies co-exist uneasily with more traditional methods of display. In this paper we describe a design strategy for mixing realities in museum spaces. An approach is adopted for designing interactives which complement rather than replace conventional methods. Our approach is explored through an exhibition which provides visitors with the opportunity to hear and leave opinions on unclassified historical artefacts. An analysis of visitor interaction reveals that avoiding simulation of established methods can allow visitors to weave novel and traditional practices. These results indicate designs for mixing realities in broader settings

Dispersive-wave-agile optical frequency division

The remarkable frequency stability of resonant systems in the optical domain (optical cavities and atomic transitions) can be harnessed at frequency scales accessible by electronics using optical frequency division. This capability is revolutionizing technologies spanning time keeping to high-performance electrical signal sources. A version of the technique called 2-point optical frequency division (2P-OFD) is proving advantageous for application to high-performance signal sources. In 2P-OFD, an optical cavity anchors two spectral endpoints defined by lines of a frequency comb. The comb need not be self-referenced, which greatly simplifies the system architecture and reduces power requirements. Here, a 2P-OFD microwave signal source is demonstrated with record-low phase noise using a microcomb. Key to this advance is a spectral endpoint defined by a frequency agile single-mode dispersive wave that is emitted by the microcomb soliton. Moreover, the system frequency reference is a compact all-solid-state optical cavity with a record Q-factor. The results advance integrable microcomb-based signal sources into the performance realm of much larger microwave sources