Search for: All records

We report Ge23Sb7S70 chalcogenide ring resonators with up to 8 × 104 quality factors operating around 3.6 µm wavelength fabricated through e-beam lithography. Their rib waveguide geometry can be engineered to support close-to-zero dispersion modes needed for mid-infrared microcomb generation. 

We present the results of direct measurements of the effect of mechanically applied biaxial strain on Auger recombination rates in InGaAs quantum wells grown on InP. By mounting these structures on a flexible membrane, we applied strain mechanically rather than by changing the quantum well alloy fraction. Specifically, we employed time-resolved photoluminescence spectroscopy to probe the recombination dynamics in the degenerate carrier regime. From these measurements, we extract the non-degenerate cubic Auger coefficient C30. We found that applying 1.59% tensile biaxial strain increased the Auger C30 coefficient by 325% in one of our samples. These results support the hypothesis that the mechanical strain induced by heteroepitaxy plays a direct role in mitigating Auger recombination in InP-based telecommunication-range lasers. 

Miniaturized microscopes for monitoring neural activity are an indispensable tool for neuroscience research. We present a novel MEMS based miniature microscope with patterned optogenetic stimulation capabilities enabling cell-specific 2-photon optogenetics and 2-photon imaging. 

In-situ monitoring techniques of reverse osmosis (RO) desalination systems, particularly those with chemical sensing capabilities, can provide the means for better understanding important scaling mechanisms as well as early scaling detection. In this work, both calcium sulfate and calcium carbonate scaling on RO membranes were detected concurrently in real time using Raman spectroscopy to provide a unique chemical fingerprint. Two different sampling methodologies (manual and automated) were employed, and their performance was evaluated by comparing the Raman detection times to concurrent values of flux decline. The manual sampling strategy resulted in the detection of calcium sulfate and calcium carbonate at mean permeate flux declines of 13 ± 10 % and 22 ± 3 %, respectively. The automated sampling strategy provided better performance, with detection of calcium sulfate and calcium carbonate at mean flux declines of 8 ± 5 % and 4 ± 3 %, respectively. The increasedsensitivity and decreased variability of the automated sampling strategy provided valuable preliminary insights for the selection of optimized sampling strategies. The ability to identify the chemical composition of different scaling crystals including their polymorphs is an important step toward better understanding of the crystallization pathways of multi-component feed streams used in seawater and brackish water RO desalination. 

We characterized the impact of mechanically-applied biaxial strain on Auger recombination in InGaAs quantum wells using time-resolved photoluminescence. Our results support that Auger recombination is reduced by mechanical distortion introduced by strained-layer epitaxy. 

We numerically compare the null quality for STED microscopy generated by Laguerre-Gaussian beams with orbital angular momentum and donut beams generated by incoherent addition of orthogonal Hermite Gaussian beams when imaging deep biological tissue. 

We present a new architecture for quantum-enhanced multiparameter estimation, where measured phases are cascaded along a single optical fiber. Embedded reflectors separate these phases, enabling novel fiber-based quantum distributed sensing of temperature and strain. 

In this work we present a two-dimensional micro-scale array of individually addressable, focal length tunable, electrowetting lenses fabricated using standard microfabrication techniques. The compact, transmissive nature of these arrays opens the possibility for integration into miniature optical systems involving wavefront shaping and beam steering.