Deep UV Light Source Research Articles

Real-time and quantitative protein detection via polyacrylamide gel electrophoresis and online intrinsic fluorescence imaging

The detection of intrinsic protein fluorescence is a powerful tool for studying proteins in their native state. Thanks to its label-free and stain-free feature, intrinsic fluorescence detection has been introduced to polyacrylamide gel electrophoresis (PAGE), a fundamental and ubiquitous protein analysis technique, to avoid the tedious detection process. However, the reported methods of intrinsic fluorescence detection were incompatible with online PAGE detection or standard slab gel. Here, we fulfilled online intrinsic fluorescence imaging (IFI) of the standard slab gel to develop a PAGE-IFI method for real-time and quantitative protein detection. To do so, we comprehensively investigated the arrangement of the deep-UV light source to obtain a large imaging area compatible with the standard slab gel, and then designed a semi-open gel electrophoresis apparatus (GEA) to scaffold the gel for the online UV irradiation and IFI with low background noise. Thus, we achieved real-time monitoring of the protein migration, which enabled us to determine the optimal endpoint of PAGE run to improve the sensitivity of IFI. Moreover, online IFI circumvented the broadening of protein bands to enhance the separation resolution. Because of the low background noise and the optimized endpoint, we showcased the quantitative detection of bovine serum albumin (BSA) with a limit of detection (LOD) of 20 ng. The standard slab gel provided a high sample loading volume that allowed us to attain a wide linear range of 0.03–10 μg. These results indicate that the PAGE-IFI method can be a promising alternative to conventional PAGE and can be widely used in molecular biology labs.

Detection of Sulfur Dioxide by Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS).

Sulfur dioxide (SO2) is an important precursor for the formation of atmospheric sulfate aerosol and acid rain. We present an instrument using Broadband Cavity-Enhanced Absorption Spectroscopy (BBCEAS) for the measurement of SO2 with a minimum limit of detection of 0.75 ppbv (3-) using the spectral range 305.5–312 nm and an averaging time of 5 min. The instrument consists of high-reflectivity mirrors (0.9985 at 310 nm) and a deep UV light source (Light Emitting Diode). The effective absorption path length of the instrument is 610 m with a 0.966 m base length. Published reference absorption cross sections were used to fit and retrieve the SO2 concentrations and were compared to fluorescence standard measurements for SO2. The comparison was well correlated, R2 = 0.9998 with a correlation slope of 1.04. Interferences for fluorescence measurements were tested and the BBCEAS showed no interference, while ambient measurements responded similarly to standard measurement techniques.

Complete decomposition of sulfamethoxazole during an advanced oxidation process in a simple water treatment system

A simple water treatment system consisting of a deep UV light (λ = 222 nm) source, a mesoporous TiO2/boron-doped diamond (BDD) photocatalyst, and a BDD electrode was prepared and used to decompose sulfamethoxazole (SMX) in an advanced oxidation process. The mesoporous TiO2/BDD photocatalyst used with the electrochemical treatment promoted SMX decomposition, but the mesoporous TiO2/BDD photocatalyst alone had a similar ability to decompose SMX as photolysis. Fragments produced through photocatalytic treatment were decomposed during the electrochemical treatment and fragments produced during the electrochemical treatment were decomposed during the photocatalytic treatment, so performing the electrochemical and photocatalytic treatments together effectively decomposed SMX and decrease the total organic carbon concentration to a trace.

Design and experiment of a tunable narrow-passband deep UV light source

Design and experiment of a tunable narrow-passband deep UV light source

High-efficiency AlGaN/GaN/AlGaN tunnel junction ultraviolet light-emitting diodes

AlGaN is the material of choice for high-efficiency deep UV light sources, which is the only alternative technology to replace mercury lamps for water purification and disinfection. At present, however, AlGaN-based mid- and deep UV LEDs exhibit very low efficiency. Here, we report a detailed investigation of the epitaxy and characterization of LEDs utilizing an AlGaN/GaN/AlGaN tunnel junction structure, operating at ∼ 265 nm , which have the potential to break the efficiency bottleneck of deep UV photonics. A thin GaN layer was incorporated between p + and n + -AlGaN to reduce the tunneling barrier. By optimizing the thickness of the GaN layer and thickness of the top n -AlGaN contact layer, we demonstrate AlGaN deep UV LEDs with a maximum external quantum efficiency of 11% and wall-plug efficiency of 7.6% for direct on-wafer measurement. It is also observed that the devices exhibit severe efficiency droop under low current densities, which is explained by the low hole mobility, due to the hole hopping conduction in the Mg impurity band and the resulting electron overflow.

Focus on photonics, spectrometry, and spectroscopy

Focus on photonics, spectrometry, and spectroscopy

55‐3: Distinguished Paper: Development of G6 Exposure Tool for 1.2 µm Resolution

We have proposed exposure method using Deep UV (DUV) exposure light to realize high resolution and high productivity in FPD lithography. [1] Here we show development concepts for our new G6 exposure tools with DUV light sources, and exposure test results with a test exposure tool.

Development of G6 exposure tool for 1.2 μm resolution

AbstractWe have proposed exposure method using Deep UV (DUV) exposure light to realize high resolution and high productivity in FPD lithography. Here, we show development concepts for our new G6 exposure tools with DUV light sources and exposure test results with a test exposure tool.

On compensation in Si-doped AlN

Controllable n-type doping over wide ranges of carrier concentrations in AlN, or Al-rich AlGaN, is critical to realizing next-generation applications in high-power electronics and deep UV light sources. Silicon is not a hydrogenic donor in AlN as it is in GaN; despite this, the carrier concentration should be controllable, albeit less efficiently, by increasing the donor concentration during growth. At low doping levels, an increase in the Si content leads to a commensurate increase in free electrons. Problematically, this trend does not persist to higher doping levels. In fact, a further increase in the Si concentration leads to a decrease in free electron concentration; this is commonly referred to as the compensation knee. While the nature of this decrease has been attributed to a variety of compensating defects, the mechanism and identity of the predominant defects associated with the knee have not been conclusively determined. Density functional theory calculations using hybrid exchange-correlation functionals have identified VAl+nSiAl complexes as central to mechanistically understanding compensation in the high Si limit in AlN, while secondary impurities and vacancies tend to dominate compensation in the low Si limit. The formation energies and optical signatures of these defects in AlN are calculated and utilized in a grand canonical charge balance solver to identify carrier concentrations as a function of Si content. The results were found to qualitatively reproduce the experimentally observed compensation knee. Furthermore, these calculations predict a shift in the optical emissions present in the high and low doping limits, which is confirmed with detailed photoluminescence measurements.

Deep-ultraviolet light source with a carbon nanotube cold-cathode electron beam

Deep-ultraviolet (UV) light is widely used in many industries including medicine because it has sufficient energy to kill viruses and bacteria. However, deep UV with a wavelength of 254 nm can damage human cells, so it is necessary to develop a deep-UV light source with a shorter wavelength to minimize the damage to human cells while still killing viruses. The authors used a carbon nanotube-based cold-cathode electron beam (C-beam) and wide-bandgap anode to fabricate a deep-UV light source with an emission wavelength below 250 nm. The anode was fabricated by annealing ZnO ink on a Si wafer; deep UV with a wavelength of 247 nm and full width at half maximum of 23 nm was obtained. In the case of C-beam irradiation of an anode fabricated on a quartz substrate, deep UV with wavelengths of 208, 226, and 244 nm was generated through excitation with a beam energy of 7 kV and beam currents of 0.3 and 0.5 mA.

Single-mode deep-UV light source at 191.7 nm by seventh-harmonic generation of a high-power, Q-switched, injection-locked 1342 nm Nd:YVO₄ laser.

A single-mode deep-UV laser at 191.7 nm is demonstrated by seventh-harmonic generation of a single-mode 1342 nm Nd:YVO₄ laser. The fundamental laser is an injection-locked, Q-switched ring laser at 10 kHz pulse repetition frequency. By cascaded second-harmonic and sum-frequency generation, an average power of 230 mW at 191.7 nm is achieved. At 185 mW, the setup features a Gaussian beam with a beam quality factor of M²<1.5. A pulse duration of 9 ns with pulse energy fluctuations of σ<3% is obtained. The long-term spectral width is approximately 240 MHz full width at half-maximum, measured with a homemade scanning confocal Fabry-Perot interferometer. This work opens possibilities in fiber Bragg grating production, allowing the inscription of long gratings.

Sensitization of Sn2+ on Tb3+ luminescence for deep UV excitation in phosphate glasses

Tb3+ and Sn2+ co-doped strontium phosphate glasses are prepared and their unique photoluminescence (PL) properties for deep UV excitation are investigated. With the co-doped Sn2+ ions, Tb3+ keeps the original PL behaviors under near UV excitation while its PL action for deep UV excitation is enhanced tremendously. PL emission and excitation spectra demonstrate the sensitization role of Sn2+ on the Tb3+ emissions for deep UV excitation that is associated with the strong deep UV absorption of Sn2+ for greatly enhancing the resonance of the Tb3+ excitation with the deep UV light source. The decay curves of Sn2+ and Tb3+ emissions for both singly doped and co-doped samples are single exponentially well fitted with almost the same emission lifetime (τ) values in the microsecond and millisecond time regimes, respectively, confirming that Sn2+ and Tb3+ act as an independent activator in the present phosphate glass matrix while an involved energy transfer from Sn2+ to Tb3+ is radiative. Moreover, Sn2+ and Tb3+ can be co-excited with deep UV light to emit tunable light from blue to green with the definite CIE chromaticity coordinate for different applications.

Excited-state dynamics of furan studied by sub-20-fs time-resolved photoelectron imaging using 159-nm pulses.

The excited-state dynamics of furan were studied by time-resolved photoelectron imaging using a sub-20-fs deep UV (198 nm) and vacuum UV (159 nm) light source. The 198- and 159-nm pulses produce photoionization signals in both pump-probe and probe-pump pulse sequences. When the 198-nm pulse precedes the 159-nm pulse, it creates the (1)A2(3s) Rydberg and (1)B2(ππ(∗)) valence states, and the former decays exponentially with a time constant of about 20 fs whereas the latter exhibits more complex wave-packet dynamics. When the 159-nm pulse precedes the 198-nm pulse, a wave packet is created on the (1)A1(ππ(∗)) valence state, which rapidly disappears from the observation window owing to structural deformation. The 159-nm photoexcitation also creates the 3s and 3px,y Rydberg states non-adiabatically.

Spatial wettability patterning of glass microchips for water-in-oil-in-water (W/O/W) double emulsion preparation

Double emulsions are of great potential in many applications, including cosmetics, foods, and drug delivery. However, current preparation methods for double emulsions are not able to satisfactorily control emulsion size and structure. Microfluidic techniques open up new opportunities for this field but challenges still remain. This article presents a partially hydrophilic and partially hydrophobic glass microchip for generating water-in-oil-in-water (W/O/W) double emulsions. The device was first hydrophobized by forming an octadecyltrichlorosilane layer through self-assembly on the entire microchannel surface. Then, a hydrophilic surface was obtained by spatially photodegrading the hydrophobic organic layer with a deep UV-light source and a photomask. Thus, a distinctive wettability contrast was achieved on different parts of the microchannel surface. By optimizing the UV irradiation time, W/O/W double emulsions were successfully created on the microchip. Double emulsions prepared by this device were monodisperse and had narrow size distribution with coefficient of variation values less than 8%. Moreover, both the size and the number of inner droplets could be controlled by adjusting the flow rates.

All solid-state 1917 nm deep-UV light source by seventh harmonic generation of an 888 nm pumped, Q-switched 1342 nm Nd:YVO_4 laser with excellent beam quality

In this paper we report on the realization of a deep-UV light source using the 1.3 μm transition of neodymium as pumping wavelength. The 191.7 nm radiation was obtained by generating the seventh harmonic of a high-power Q-switched 1342 nm Nd:YVO4 laser. A cesium lithium borate crystal was used for sum frequency mixing of the sixth harmonic and the fundamental. With a total of four conversion stages, up to 240 mW were achieved, with excellent beam quality at 155 mW (M2 < 1.7) and 190 mW (M2 < 1.9).

Nonadiabatic Electronic Dynamics in Isolated Molecules and in Solution Studied by Ultrafast Time–Energy Mapping of Photoelectron Distributions

Abstract Nonadiabatic electronic dynamics contribute to the diversity of chemical reactions. We investigate nonadiabatic dynamics in isolated molecules and aqueous solutions by time-resolved photoelectron spectroscopy. For isolated molecules in the gas phase, we combine two-dimensional imaging detection of electrons and a sub-20 fs deep UV and vacuum UV light source to measure time-evolution of the photoelectron kinetic energy and angular distributions. Time–energy mapping of photoelectron angular anisotropy reveals the S2 → S1 internal conversion dynamics through conical intersection in pyrazine, benzene, and toluene. The time–energy mapping is also employed to extract the photoelectron angular distribution in the molecular frame for nitric oxide. For electronic dynamics in aqueous solution, we employ time-resolved photoelectron spectroscopy using a liquid beam and an electrostatic or a time-of-flight electron energy analyzer. Successful observation of ultrafast electron-transfer reactions in aqueous solutions and measurement of electron binding energies of solvated species suggest promising future developments of this very young field.

Growth and Characterization of AlGaN Multiple Quantum Wells for Electron-Beam Target for Deep-Ultraviolet Light Sources

The structure of Si-doped AlGaN multiple quantum well (MQW) targets has been optimized for application to electron-beam (EB)-pumped deep-ultraviolet (UV) light sources. The deep-UV light emission from Si-doped AlGaN MQW targets pumped by a 10 kV EB has been evaluated. The targets exhibited a deep-UV light output power of over 15 mW at a peak wavelength of 256 nm for an EB input power of 2.0 W, and the conversion efficiency was estimated to be over 0.75%. These results demonstrate the advantageousness of using p-type-AlGaN-free AlGaN MQW targets as a material for application to EB-pumped deep-UV light sources.

Deep-UV nonlinear optical crystal KBe2BO3F2—discovery, growth, optical properties and applications

This review introduces in detail the history of the discovery of the nonlinear optical crystal KBe2BO3F2 (KBBF), with a full description of its growth, space structure, optical properties, and capability to generate deep-ultraviolet (UV) harmonic generation. Several important applications developed recently using all-solid-state deep-UV light sources, such as super-high-resolution laser photoemission spectrograph and 193 nm photolithography, will be reviewed.

Development of a high-power deep-ultraviolet continuous-wave coherent light source for laser cooling of silicon atoms

We developed a deep-UV single-mode coherent light source through two-stage highly efficient frequency conversions by use of external cavities. In the first stage, second-harmonic power of 500 mW was obtained by frequency doubling of a 746-nm Ti:sapphire laser with a conversion efficiency of 40%. In the second stage, 50-mW power at ~252nm was obtained by doubly resonant sum-frequency mixing of 373-nm light from the first-stage conversion and 780-nm light from a diode laser. The output performance of this deep-UV light source is sufficient for laser cooling of neutral silicon atoms.

1.9 GHz Low-Loss Surface Acoustic Wave Filter: Lift-Off Method and 3 mm Square Small Size Package

A novel 1.9 GHz low-loss surface acoustic wave (SAW) filter for personal handy phone systems has been produced. The 0.5 µm line and space electrode of SAW filter on the LiTaO3 substrate was fabricated by the lift-off process using negative photoresist. A deep UV light source was used in the photo exposure process. Electrodes with 0.2 µ m gap could be easily formed by the lift-off process. This SAW filter chip was mounted in the new small size (3.0 mm square) leadless ceramic package. Because the parasitic inductance and capacitance of this package are smaller than the usual 4.8 mm×5.2 mm package, a 1.9 GHz filter with small insertion loss of 1.7 dB was obtained. The suppression level of this filter at 4.5 GHz was greater than 30 dB.