Half-Wave Dipolar Metal-Semiconductor Laser

Nano-scale lasers harnessing metallic plasmons hold promise across physical sciences and industrial applications. Plasmons are categorized as surface plasmon polaritons (SPP) and localized surface plasmons (LSP). While SPP has gained popularity for nano-lasers by fitting a few cycles of SPP waves into resonators, achieving LSP lasing in single nanoparticles remains an elusive goal. Here, we highlight the equivalence of LSP and SPP within resonant systems and present lasers oscillating in the lowest-order LSP or, equivalently, half-cycle SPP. This diffraction-limited dipolar emitter is realized through strong coupling of plasmonic oscillation in gold and dielectric resonance in high-gain III-V semiconductor in the near infrared away from surface plasmon frequencies. The resulting single-mode stimulated emission peak exhibits linewidth Q factors over 50 at room temperature, with wide tunability spanning from 1190 to 1460 nm determined by resonator sizes ranging from 190 to 280 nm. A semiconductor laser model elucidates the temporal and spectral buildup dynamics under optical pumping. Notably, linewidth Q values surpassing 250 are attained from higher-order, isolated laser particles within live biological cells. These results offer fresh perspectives in nanophotonics and indicate promising opportunities for multiplexed biological applications

Laser Particle Stimulated Emission Microscopy

We introduce an optical microscopy technique that utilizes micro- or nanolasers embedded in a sample as imaging probes. The narrow spectra and nonlinear power dependence of stimulated emission from the laser particles yield optical sectioning, subdiffraction resolution, and low out-of-focus background. A proof of concept is demonstrated using perovskite nanowires.National Science Foundation (U.S.) (Grant ECCS-1505569)National Institutes of Health (U.S.) (Grants DP1EB024242 and P41EB015903)Massachusetts General Hospital. Research Scholar Award Progra

Ultrasmall InGa(As)P dielectric and plasmonic nanolasers

Nanolasers have great potential as both on-chip light sources and optical barcoding particles. We demonstrate ultrasmall InGaP and InGaAsP disk lasers with diameters down to 360 nm (198 nm in height) in the red spectral range. Optically pumped, room-temperature, single-mode lasing was achieved from both disk-on-pillar and isolated particles. When isolated disks were placed on gold, plasmon polariton lasing was obtained with Purcell-enhanced stimulated emission. UV lithography and plasma ashing enabled the fabrication of nanodisks on a wafer-scale, with intended random size variation. Silica-coated nanodisk particles generated stable sub-nanometer spectra from within biological cells across an 80 nm bandwidth from 635 to 715 nm.Comment: 25 pages, 5 main figures, 8 supplementary figures, 3 supplementary table

Toward biomaterial-based implantable photonic devices

Optical technologies are essential for the rapid and efficient delivery of health care to patients. Efforts have begun to implement these technologies in miniature devices that are implantable in patients for continuous or chronic uses. In this review, we discuss guidelines for biomaterials suitable for use in vivo. Basic optical functions such as focusing, reflection, and diffraction have been realized with biopolymers. Biocompatible optical fibers can deliver sensing or therapeutic-inducing light into tissues and enable optical communications with implanted photonic devices. Wirelessly powered, light-emitting diodes (LEDs) and miniature lasers made of biocompatible materials may offer new approaches in optical sensing and therapy. Advances in biotechnologies, such as optogenetics, enable more sophisticated photonic devices with a high level of integration with neurological or physiological circuits. With further innovations and translational development, implantable photonic devices offer a pathway to improve health monitoring, diagnostics, and light-activated therapies. Keywords: biomaterials; biocompatible; biodegradable; optics; photonicsUnited States. Department of Defense (Award FA9550-13-1-0068)National Institutes of Health (U.S.) (Award P41-EB015903)National Institutes of Health (U.S.) (Award R01-CA192878)National Science Foundation (U.S.) (Award CBET-1264356)National Science Foundation (U.S.) (Award ECCS-1505569

Ferroelectric field effect induced charge carrier transport modulation at quantum dot solar cell heterojunction interface

Inherent unidealistic properties associated with materials and device structures inevitably limit the performance of photovoltaic devices. To overcome the inherent limit, judicious use of ferroelectric materials has been introduced. Here, we demonstrate modulations of charge carrier transport at the heterojunction interface with respect to polarities of electric dipoles. Attributed to an additional electric field by the ferroelectric effect, a built-in potential at the junction increases, leading to enhanced charge carrier transport, reduced charge recombination, and, consequently, enhanced power conversion efficiency of lead sulfide quantum dot solar cells. The coupling of the ferroelectric effect with the solar cell provides an important platform to further develop solution-processable flat panel solar cell technology

Quantum dots for hybrid energy harvesting: from integration to piezo-phototronics

Energy harvesting, which converts wasted environmental energy into electricity by utilizing various physical effects, hasattracted tremendous research interests as is one of the key technologies to realize advanced electronics in the future. In this review, we introduce recent progress in the field of hybrid energy harvesting technology. In particular, we focus on a quantum dots (QD)‐based hybrid energy harvesting device. Attributed to fascinating material properties that QD possess, employment of QDs into hybrid energy harvesting has shown great potential for independent and sustainable energy supply.First, an integration of a QD solar cell into a mechanical energy harvester is discussed to harness different types of environmental energy sources simultaneously. Second, a comprehensive explanation of a piezotronic and piezo‐phototronic effect is provided, which is followed by QD‐based piezo‐phototronic applications. Finally, we summarize recent progress that has been made in energy harvesting technology involving a photovoltaic and piezo/triboelectric effec

Smartphone-based multispectral imaging: system development and potential for mobile skin diagnosis

We investigate the potential of mobile smartphone-based multispectral imaging for the quantitative diagnosis and management of skin lesions. Recently, various mobile devices such as a smartphone have emerged as healthcare tools. They have been applied for the early diagnosis of nonmalignant and malignant skin diseases. Particularly, when they are combined with an advanced optical imaging technique such as multispectral imaging and analysis, it would be beneficial for the early diagnosis of such skin diseases and for further quantitative prognosis monitoring after treatment at home. Thus, we demonstrate here the development of a smartphone-based multispectral imaging system with high portability and its potential for mobile skin diagnosis. The results suggest that smartphone-based multispectral imaging and analysis has great potential as a healthcare tool for quantitative mobile skin diagnosis. © 2016 Optical Society of America.1

Monolayer optical memory cells based on artificial trap-mediated charge storage and release.

Monolayer transition metal dichalcogenides are considered to be promising candidates for flexible and transparent optoelectronics applications due to their direct bandgap and strong light-matter interactions. Although several monolayer-based photodetectors have been demonstrated, single-layered optical memory devices suitable for high-quality image sensing have received little attention. Here we report a concept for monolayer MoS2 optoelectronic memory devices using artificially-structured charge trap layers through the functionalization of the monolayer/dielectric interfaces, leading to localized electronic states that serve as a basis for electrically-induced charge trapping and optically-mediated charge release. Our devices exhibit excellent photo-responsive memory characteristics with a large linear dynamic range of ∼4,700 (73.4 dB) coupled with a low OFF-state current (<4 pA), and a long storage lifetime of over 104 s. In addition, the multi-level detection of up to 8 optical states is successfully demonstrated. These results represent a significant step toward the development of future monolayer optoelectronic memory devices

Charge transport modulation of a flexible quantum dot solar cell using a piezoelectric effect

Colloidal quantum dots are promising materials for flexible solar cells, as they have a large absorption coefficient at visible and infrared wavelengths, a band gap that can be tuned across the solar spectrum, and compatibility with solution processing. However, the performance of flexible solar cells can be degraded by the loss of charge carriers due to recombination pathways that exist at a junction interface as well as the strained interface of the semiconducting layers. The modulation of the charge carrier transport by the piezoelectric effect is an effective way of resolving and improving the inherent material and structural defects. By inserting a porous piezoelectric poly(vinylidenefluoride‐trifluoroethylene) layer so as to generate a converging electric field, it is possible to modulate the junction properties and consequently enhance the charge carrier behavior at the junction. This study shows that due to a reduction in the recombination and an improvement in the carrier extraction, a 38% increase in the current density along with a concomitant increase of 37% in the power conversion efficiency of flexible quantum dots solar cells can be achieved by modulating the junction properties using the piezoelectric effect