Control of edge bulge evolution during photoresist reflow and it's application to diamond micro-lens fabrication

We present an empirical study of profile evolution of lithographically defined photoresist (PR) patterns during thermal reflow and apply the findings to diamond micro-lens fabrication. During PR reflow, a bulge forms at the edge of the PR pattern and propagates inwards as the temperature and PR thickness are increased. An empirical relationship for this propagation is derived. Furthermore, it was found that at a certain reflow temperature and a limited pattern size, there is a minimum initial thickness of the PR pattern for forming spherical lens profiles. Based on these findings, diamond micro-lenses with a diameter of 400 µm and a previously unachieved radius of curvature of over 13 mm were fabricated. This is underpinned by forming PR micro-lens patterns with a large radius of curvature and transferring the PR patterns through low-selectivity Ar/Cl2 inductively coupled plasma etching

Experimental study on microlaser fluorescence spectrometer

This paper presents a kind of miniature handheld laser fluorescence spectrometer, which integrates a laser emission system, a spectroscopic system, and a detection system into a volume of 100 × 50 × 20 mm3. A universal serial bus interface is connected to PC for data processing and spectrum display. The emitted laser wavelength is 405 nm. A spectral range is 400 to 760 nm and 2-nm optical resolution has been achieved. This spectrometer has the advantages of compact structure, small volume, high sensitivity, and low cost. 1.Introductio

Integrating diamond with GaN photonic device

The nitrogen vacancy is a photostable emitter in diamond which is optically accessible at room temperature and a potential candidate for quantum information processing as a spin register. The challenge facing research today is the efficient collection and manipulation of the NV’s emissions, such as enhancing the zero phonon line transitions for a coherent spin-photon interface. This project focuses on integrating ultra-thin diamond membranes with established photonic devices. By bonding the diamond to GaN, for example, mode simulations show that light can be coupled significantly into and out of the defect allowing processing across large area PICs

Ultra-portable explosives sensor based on a CMOS fluorescence lifetime analysis micro-system

The paper published in AIP Advances (a new journal from the American Institute of Physics) had 1100 article downloads in the first 5 months after publication, and was on the journal’s “most read” list for 4 months. The work was featured by AIP in a Physics News Highlight and press release which resulted in >50 international internet articles and an article in Laser Focus World.This work explores the use of a green-light-emitting copolymer as a chemosensor to detect nitroaromatic-based explosive vapors by recording photoluminescence (PL) and time-resolved PL decay. We show successful detection of 10 ppb 1,4-dinitrobenzene (DNB) vapor. Both a conventional time-correlated single photon counting (TCSPC) device and CMOS time-resolved fluorescence lifetime microsystem are used in the DNB detection. An ultra-portable on-site explosive sensor based on the micro-system has also been demonstrated. This gives rise to the potential for real-time, reliable, inexpensive organic/inorganic hybrid explosives detection.Peer reviewe

Concept of a GaN-LED-based positioning system using structured illumination

Accurate self-orientation within a space can be achieved using only a simple photodetector and a remote Gallium Nitride micro-light-emitting diode array, emitting a time series of varying spatial illumination patterns onto the scene

GaN directional couplers for integrated quantum photonics

Large cross-section GaN waveguides are proposed as a suitable architecture to achieve integrated quantum photonic circuits. Directional couplers with this geometry have been designed with aid of the beam propagation method and fabricated using inductively coupled plasma etching. Scanning electron microscopy inspection shows high quality facets for end coupling and a well defined gap between rib pairs in the coupling region. Optical characterization at 800 nm shows single-mode operation and coupling-length-dependent splitting ratios. Two photon interference of degenerate photon pairs has been observed in the directional coupler by measurement of the Hong-Ou-Mandel dip with 96% visibility.Comment: 4 pages, 5 figure

Aging characteristics of blue InGaN micro-light emitting diodes at an extremely high current density of 3.5kAcm−2

The aging characteristics of blue InGaN micro-light emitting diodes (micro-LEDs) with different sizes have been studied at an extremely high current density 3.5 kA cm−2 for emerging microLED applications including visible light communication (VLC), micro-LED pumped organic lasers and optogenetics. The light output power of micro-LEDs first increases and then decreases due to the competition of Mg activation in p-GaN layer and defect generation in the active region. The smaller micro-LEDs show less light output power degradation compared with larger micro-LEDs, which is attributed to the lower junction temperature of smaller micro-LEDs. It is found that the high current density without additional junction temperature cannot induce significant micro-LED degradation at room temperature but the combination of the high current density and high junction temperature leads to strong degradation. Furthermore, the cluster LEDs, composed of a micro-LED array, have been developed with both high light output power and less light output degradation for micro-LED applications in solid state lighting and VLC

Active-matrix GaN micro light-emitting diode display with unprecedented brightness

Displays based on microsized gallium nitride light-emitting diodes possess extraordinary brightness. It is demonstrated here both theoretically and experimentally that the layout of the n-contact in these devices is important for the best device performance. We highlight, in particular, the significance of a nonthermal increase of differential resistance upon multipixel operation. These findings underpin the realization of a blue microdisplay with a luminance of 10⁶ cd/m²

Visual Attention and Eye Gaze During Multiparty Conversations with Distractions

Our objective is to develop a computational model to predict visual attention behavior for an embodied conversational agent. During interpersonal interaction, gaze provides signal feedback and directs conversation flow. Simultaneously, in a dynamic environment, gaze also directs attention to peripheral movements. An embodied conversational agent should therefore employ social gaze not only for interpersonal interaction but also to possess human attention attributes so that its eyes and facial expression portray and convey appropriate distraction and engagement behaviors