arXiv subjects

Youngho Jung

Publications and source records attributed to Youngho Jung.

3 recordsLinked to original sources

arXiv2024

Implantable silicon neural probes with nanophotonic phased arrays for single-lobe beam steering

In brain activity mapping experiments using optogenetics, patterned illumination is crucial for deterministic and localized stimulation of neurons. However, due to optical scattering in brain tissue, light-emitting implantable devices are needed to bring precise patterned illumination to deep brain regions. A promising solution is silicon neural probes with integrated nanophotonic circuits that form tailored beam emission patterns without lenses. Here, we demonstrate neural probes with grating-based light emitters that generate a single steerable light beam across $> 60\%$ of the steering range with $\ge 4$ dB of background suppression for optogenetic photostimulation. The light emitters, optimized for blue or amber light, combine end-fire optical phased arrays with slab gratings to suppress higher-order sidelobes.

physics.optics↗

arXiv2022

Microcantilever-integrated photonic circuits for broadband laser beam scanning

Laser beam scanning is central to many applications, including displays, microscopy, three-dimensional mapping, and quantum information. Reducing the scanners to microchip form factors has spurred the development of very-large-scale photonic integrated circuits of optical phased arrays and focal plane switched arrays. An outstanding challenge remains to simultaneously achieve a compact footprint, broad wavelength operation, and low power consumption. Here, we introduce a laser beam scanner that meets these requirements. Using microcantilevers embedded with silicon nitride nanophotonic circuitry, we demonstrate broadband, one- and two-dimensional steering of light with wavelengths from 410 nm to 700 nm. The microcantilevers have ultracompact ~0.1 mm$^2$ areas, consume ~31 to 46 mW of power, are simple to control, and emit a single light beam. The microcantilevers are monolithically integrated in an active photonic platform on 200-mm silicon wafers. The microcantilever-integrated photonic circuits miniaturize and simplify light projectors to enable versatile, power-efficient, and broadband laser scanner microchips.

physics.optics↗

arXiv2020

Observation of photoelectric nonvolatile memory and oscillations in VO2 at room temperature

Vanadium dioxide (VO2) is a phase change material that can reversibly change between high and low resistivity states through electronic and structural phase transitions. Thus far, VO2 memory devices have essentially been volatile at room temperature, and nonvolatile memory has required non-ambient surroundings (e.g., elevated temperatures, electrolytes) and long write times. Here, we report the first observation of optically addressable nonvolatile memory in VO2 at room temperature with a readout by voltage oscillations. The read and write times had to be kept shorter than about 150 μs. The writing of the memory and onset of the voltage oscillations had a minimum optical power threshold. This discovery demonstrates the potential of VO2 for new computing devices and architectures, such as artificial neurons and oscillatory neural networks.

physics.app-ph↗