Parallel random LiDAR with spatial multiplexing of a many-mode laser.

We propose and experimentally demonstrate parallel light detection and ranging (LiDAR) using random intensity fluctuations from a highly multimode laser. We optimize a degenerate cavity to have many spatial modes lasing simultaneously with different frequencies. Their spatio-temporal beating creates ultrafast random intensity fluctuations, which are spatially demultiplexed to generate hundreds of uncorrelated time traces for parallel ranging. The bandwidth of each channel exceeds 10 GHz, leading to a ranging resolution better than 1 cm. Our parallel random LiDAR is robust to cross-channel interference, and will facilitate high-speed 3D sensing and imaging.

Spatiotemporal lasing dynamics in a Limaçon-shaped microcavity.

Limaçon-shaped microdisk lasers are promising on-chip light sources with low lasing threshold and unidirectional output. We conduct an experimental study on the lasing dynamics of Limaçon-shaped semiconductor microcavities. The edge emission exhibits intensity fluctuations over a wide range of spatial and temporal scales. They result from multiple dynamic processes with different origins and occur on different spatiotemporal scales. The dominant process is an alternate oscillation between two output beams with a period as short as a few nanoseconds.

Impact of Cavity Geometry on Microlaser Dynamics.

We experimentally investigate spatiotemporal lasing dynamics in semiconductor microcavities with various geometries, featuring integrable or chaotic ray dynamics. The classical ray dynamics directly impacts the lasing dynamics, which is primarily determined by the local directionality of long-lived ray trajectories. The directionality of optical propagation dictates the characteristic length scales of intensity variations, which play a pivotal role in nonlinear light-matter interactions. While wavelength-scale intensity variations tend to stabilize lasing dynamics, modulation on much longer scales causes spatial filamentation and irregular pulsation. Our results will pave the way to control the lasing dynamics by engineering the cavity geometry and ray dynamical properties.

Remote sensing of pressure inside deformable microchannels using light scattering in Scotch tape.

We present a simple but effective method to measure the pressure inside a deformable microchannel using laser scattering in a translucent Scotch tape. Our idea exploits the fact that the speckle pattern generated by a turbid layer is sensitive to the changes in the optical wavefront of an impinging beam. A change in the internal pressure of a channel deforms the elastic channel, which can be detected by measuring the speckle patterns of a coherent laser beam that has passed through the channel and the Scotch tape. We demonstrate that with a proper calibration, internal pressure can be remotely sensed with the resolution of 0.1 kPa within a pressure range of 0-3 kPa after calibration.

Massively parallel ultrafast random bit generation with a chip-scale laser.

Random numbers are widely used for information security, cryptography, stochastic modeling, and quantum simulations. Key technical challenges for physical random number generation are speed and scalability. We demonstrate a method for ultrafast generation of hundreds of random bit streams in parallel with a single laser diode. Spatiotemporal interference of many lasing modes in a specially designed cavity is introduced as a scheme for greatly accelerated random bit generation. Spontaneous emission, caused by quantum fluctuations, produces stochastic noise that makes the bit streams unpredictable. We achieve a total bit rate of 250 terabits per second with off-line postprocessing, which is more than two orders of magnitude higher than the current postprocessing record. Our approach is robust, compact, and energy-efficient, with potential applications in secure communication and high-performance computation.

Genetic and phenotypic diversity of fenitrothion-degrading bacteria isolated from soils.

Twenty-seven fenitrothion-degrading bacteria were isolated from different soils, and their genetic and phenotypic characteristics were investigated. Analysis of the 16S rDNA sequence showed that the isolates were related to members of the genera Burkholderia, Pseudomonas, Sphingomonas, Cupriavidus, Corynebacterium, and Arthrobacter. Among the 27 isolates, 12 different chromosomal DNA fingerprinting patterns were obtained by polymerase chain reaction (PCR) amplification of repetitive extragenic palindromic (REP) sequences. The isolates were able to utilize fenitrothion as a sole source of carbon and energy, producing 3-methyl-4- nitrophenol as the intermediate metabolite during the complete degradation of fenitrothion. Twenty-two of 27 isolates were able to degrade parathion, methyl-parathion, and p-nitrophenol, but only strain BS2 could degrade EPN (O-ethyl-O-p-nitrophenyl phenylphosphorothioate) as a sole source of carbon and energy for growth. Eighteen of the 27 isolates had plasmids. When analyzed with PCR amplification and dot-blotting hybridization using various specific primers targeted to the organophosphorus pesticide hydrolase genes of the previously reported isolates, none of the isolates showed positive signals, suggesting that the corresponding genes of our isolates had no significant sequence homology with those of the previously isolated organophosphate pesticide-degrading bacteria.

Genetic and phenotypic diversity of parathion-degrading bacteria isolated from rice paddy soils.

Three parathion-degrading bacteria and eight pairs of bacteria showing syntrophic metabolism of parathion were isolated from rice field soils, and their genetic and phenotypic characteristics were investigated. The three isolates and eight syntrophic pairs were able to utilize parathion as a sole source of carbon and energy, producing p-nitrophenol as the intermediate metabolite during the complete degradation of parathion. Analysis of 16S rRNA gene sequence indicated that the isolates were related to members of the genera, Burkholderia, Arthrobacter, Pseudomonas, Variovorax, and Ensifer. The chromosomal DNA patterns of the isolates obtained by polymerase-chain-reaction (PCR) amplification of repetitive extragenic palindromic (REP) sequences were distinct from one another. Ten of the isolates had plasmids. All of the isolates and syntrophic pairs were able to degrade parathion-related compounds such as EPN, p-nitrophenol, fenitrothion, and methyl-parathion. When analyzed with PCR amplification and dot-blotting hybridization using various primers targeted for the organophosphorus pesticide hydrolase genes of previously-reported isolates, most of the isolates did not show positive signals, suggesting that their parathion hydrolase genes had no significant sequence homology with those of the previously-reported organophosphate pesticide-degrading isolates.

The adsorption characteristics of fluoride on commercial activated carbon treated with quaternary ammonium salts (Quats).

Commercial activated carbon was treated with six quaternary ammonium salts (Quats), namely, hexyltrimethylammonium (HTMA), octyltrimethylammonium (OTMA), decyltrimethylammonium (DCTMA), dodecyltrimethylammonium (DDTMA), Tetradecyltrimethylammonium (TDTMA), and hexadecyltrimethylammoium (HDTMA) as to enhance the fluoride adsorption capacity. In batch mode experiments, fluoride adsorption onto the Quats-treated activated carbon decreased dramatically with increase in solution pH. Fluoride removal by the Quats-treated activated carbons was closely related to the Quats chain length at less-than critical micelle concentration (CMC). Multi-site adsorption isotherm described fluoride adsorption characteristics well. Results showed that activated carbon treated with DDTMA exhibited the best fluoride adsorption density among all Quats investigated. DDTMA-treated activated carbons exhibited two-fold increase in the fluoride adsorption capacity compared to the untreated activated carbon. Results of regeneration, by alkaline desorption and/or Quats re-loading, showed fluoride-laden activated carbons have high reusability. DDTMA increased the positive surface charge of the activated carbon that enhanced fluoride adsorption. DDTMA-treated activated carbon was promising for fluoride removal from water with much enhanced removal capacity.

Suppressing spatiotemporal lasing instabilities with wave-chaotic microcavities.

Spatiotemporal instabilities are widespread phenomena resulting from complexity and nonlinearity. In broad-area edge-emitting semiconductor lasers, the nonlinear interactions of multiple spatial modes with the active medium can result in filamentation and spatiotemporal chaos. These instabilities degrade the laser performance and are extremely challenging to control. We demonstrate a powerful approach to suppress spatiotemporal instabilities using wave-chaotic or disordered cavities. The interference of many propagating waves with random phases in such cavities disrupts the formation of self-organized structures such as filaments, resulting in stable lasing dynamics. Our method provides a general and robust scheme to prevent the formation and growth of nonlinear instabilities for a large variety of high-power lasers.

Universal sensitivity of speckle intensity correlations to wavefront change in light diffusers.

Here, we present a concept based on the realization that a complex medium can be used as a simple interferometer. Changes in the wavefront of an incident coherent beam can be retrieved by analyzing changes in speckle patterns when the beam passes through a light diffuser. We demonstrate that the spatial intensity correlations of the speckle patterns are independent of the light diffusers, and are solely determined by the phase changes of an incident beam. With numerical simulations using the random matrix theory, and an experimental pressure-driven wavefront-deforming setup using a microfluidic channel, we theoretically and experimentally confirm the universal sensitivity of speckle intensity correlations, which is attributed to the conservation of optical field correlation despite multiple light scattering. This work demonstrates that a light diffuser works as a simple interferometer, and presents opportunities to retrieve phase information of optical fields with a compact scattering layer in various applications in metrology, analytical chemistry, and biomedicine.

Development of mobile platform integrated with existing electronic medical records.

OBJECTIVES: This paper describes a mobile Electronic Medical Record (EMR) platform designed to manage and utilize the existing EMR and mobile application with optimized resources. METHODS: We structured the mEMR to reuse services of retrieval and storage in mobile app environments that have already proven to have no problem working with EMRs. A new mobile architecture-based mobile solution was developed in four steps: the construction of a server and its architecture; screen layout and storyboard making; screen user interface design and development; and a pilot test and step-by-step deployment. This mobile architecture consists of two parts, the server-side area and the client-side area. In the server-side area, it performs the roles of service management for EMR and documents and for information exchange. Furthermore, it performs menu allocation depending on user permission and automatic clinical document architecture document conversion. RESULTS: Currently, Severance Hospital operates an iOS-compatible mobile solution based on this mobile architecture and provides stable service without additional resources, dealing with dynamic changes of EMR templates. CONCLUSIONS: The proposed mobile solution should go hand in hand with the existing EMR system, and it can be a cost-effective solution if a quality EMR system is operated steadily with this solution. Thus, we expect this example to be shared with hospitals that currently plan to deploy mobile solutions.