Generation Of Ultraviolet Light Research Articles

Collimated UV light generation by two-photon excitation to a Rydberg state in Rb vapor

We use two continuous-wave (CW) laser beams of 780 nm and 515 nm to optically drive $^{85}$Rb atoms in a heated vapor cell to a low-lying Rydberg state 10D$_{5/2}$. We observe a collimated ultraviolet (UV) beam at 311 nm, corresponding to the transition frequency from the 11P$_{3/2}$ state to the 5S$_{1/2}$ state. This indicates the presence of a coherent four-wave mixing process, built up by two input laser fields as well as a terahertz (THz) radiation of 3.28 THz that is generated by amplified spontaneous emission between the 10D$_{5/2}$ and the 11P$_{3/2}$ states. We characterize the 311 nm UV light generation and its dependence on various physical parameters. This scheme could open up a new possibility for generating narrow-band THz waves as well as deep UV radiation.

Thresholdless deep and vacuum ultraviolet Raman frequency conversion in hydrogen-filled photonic crystal fiber

Coherent ultraviolet light has many uses, for example, in the study of molecular species relevant in biology and chemistry. Very few, if any, laser materials offer ultraviolet transparency along with damage-free operation at high-photon energies and laser power. Here we report efficient generation of narrowband deep and vacuum ultraviolet light using hydrogen-filled hollow-core photonic crystal fiber. Pumping above the stimulated Raman threshold at 532 nm, coherent molecular vibrations are excited in the gas, permitting thresholdless wavelength conversion in the ultraviolet with efficiencies close to 60%. The system is uniquely pressure tunable, allows spatial structuring of the out-coupled radiation, and shows excellent performance in the vacuum ultraviolet. As the underlying scattering process is effectively linear, our approach can also in principle operate at the single-photon level, when all other alternatives are extremely inefficient.

Optimization of Zn2SiO4 Anode Structure for Deep Ultraviolet Generation With Carbon Nanotube Emitters

Ultraviolet (UV) light is applied to various industrial and medical devices. In particular, deep UV light with short wavelengths could minimize the damage to human cells when it is used to virus and bacterial sterilization. We optimized the Zn2SiO4 anode structure to improve deep UV light generation with a carbon nanotube (CNT) cold cathode based electron beam (C-beam) pumping. Annealing at 1000 °C and 400 mTorr produces anode with the highest deep UV intensity. Using a 100-nm SiOx layer between Zn2SiO4 and quartz substrate, the intensity of deep UV light at a wavelength of 226 nm was increased by 1.8 times.

Toroidal Dipole-Enhanced Third Harmonic Generation of Deep Ultraviolet Light Using Plasmonic Meta-atoms

The harmonic generation of light with plasmonic and all-dielectric nanostructures has gained much recent interest. This approach is especially promising for short wavelength (i.e., ultraviolet (UV)) generation, where conventional nonlinear crystals reach their limits both in transparency and in their ability to achieve phase-matching between the input and output fields. Here, we demonstrate that the third harmonic generation of deep UV light in an indium tin oxide (ITO) film can be substantially enhanced by a metasurface consisting of metallic toroidal meta-atoms covered with an alumina layer for protection against laser-induced damage. This approach combines the benefits of the large nonlinear susceptibility of ITO with the unique field enhancement properties of a toroidal metasurface. This ITO-meta-atom combination produces a third harmonic signal at a wavelength of 262 nm that is nominally five times larger than that of an ITO film patterned with a conventional hotspot-enhanced plasmonic dimer array. This result demonstrates the potential for toroidal meta-atoms as the active engineered element in a new generation of enhanced nonlinear optical materials and devices.

Harmonic generation by atomic and nanoparticle precursors in a ZnS laser ablation plasma

Harmonic generation of a driving laser propagating across a laser ablation plasma serves for the diagnosis of multicomponent plumes. Here we study the contribution of atomic and nanoparticle precursors to the generation of coherent ultraviolet and vacuum ultraviolet light as low-order harmonics of the fundamental emission (1064nm) of a Q-switched Nd:YAG laser in a nanosecond infrared ZnS laser ablation plasma. Odd harmonics from the 3rd up to the 9th order (118.2nm) have been observed with distinct temporal and spatial characteristics which were determined by varying the delay between the ablation and driving nanosecond pulses and by spatially scanning the plasma with the focused driving beam propagating parallel to the target. At short distances from the target surface (≤1mm), the harmonic intensity displays two temporal components peaked at around 250ns and 10μs. While the early component dies off quickly with increasing harmonic order and vanishes for the 9th order, the late component is notably intense for the 7th harmonic and is still clearly visible for the 9th. Spectral analysis of spontaneous plume emissions help to assign the origin of the two components. While the early plasma component is mainly constituted by neutral Zn atoms, the late component is mostly due to nanoparticles, which upon interaction with the driving laser are subject to breakup and ionization. With the aid of calculations of the phase matching integrals within the perturbative model of optical harmonic generation, these results illustrate how atom and nanoparticle populations, with differing temporal and spatial distributions within the ablation plasma, contribute to the nonlinear medium.

Generation of femtosecond laser pulses at 396 nm in K3B6O10Cl crystal**Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB922401 and 2013CB922402) and the National Natural Science Foundation of China (Grant Nos. 11474002, 61205130, and 61575219).

K3B6O10Cl (KBOC), a new nonlinear optical crystal, shows potential advantages for the generation of deep ultraviolet (UV) light compared with other borate crystals. In this paper we study for the first time the second harmonic generation (SHG) of a femtosecond Ti:sapphire amplifier with this crystal. Laser power is obtained to be as high as 220 mW at the central wavelength of 396 nm with a 1-mm-long crystal, and the maximum SHG conversion efficiency reaches 39.3%. The typical pulse duration is 83 fs. The results show that second harmonic (SH) conversion efficiency has the room to be further improved and that the new nonlinear crystal is very suited to generate the high efficiency deep ultraviolet laser radiation below 266 nm.

Tunable ultraviolet and blue light generation from Nd:YAB random laser bolstered by second-order nonlinear processes.

Ultraviolet and blue light were obtained by nonlinear frequency conversion in a random laser (RL) based on Nd0.10Y0.90Al3(BO3)4 nanocrystalline powder. RL operation at 1062 nm, due to the 4F3/2 → 4I11/2 transition of neodymium ions (Nd3+), was achieved by exciting the Nd3+ with a tunable beam from 680 to 920 nm covering the ground state absorption transitions to the 4F9/2, (4F7/2,4S3/2), (4F5/2,2H9/2), and 4F3/2 states. Light from 340 to 460 nm was obtained via the second-harmonic generation of the excitation beam while tunable blue light, from 417 to 486 nm, was generated by self-sum-frequency mixing between the excitation beam and the RL emission.

Laser-assisted vacuum arc extreme ultraviolet source: a comparison of picosecond and nanosecond laser triggering

Extreme ultraviolet (EUV) light generation by hybrid laser-assisted vacuum arc discharge plasmas, utilizing Sn-coated rotating-disc-electrodes, was investigated. The discharge was initiated by localized ablation of the liquid tin coating of the cathode disc by a laser pulse. The laser pulse, at 1064 nm, was generated by Nd:YAG lasers with variable energy from 1 to 100 mJ per pulse. The impact of shortening the laser pulse from 7 ns to 170 ps on the EUV generation has been investigated in detail. The use of ps pulses resulted in an increase in emission of EUV radiation. With a fixed discharge energy of ~4 J, the EUV conversion efficiency tends to plateau at ~2.4 ± 0.25% for the ps laser pulses, while for the ns pulses, it saturates at ~1.7 ± 0.3%. Under similar discharge and laser energy conditions, operating the EUV source with the ps-triggering resulted also in narrower spectral profiles of the emission in comparison to ns-triggering. The results indicate an advantage in using ps-triggering in laser-assisted discharges to produce brighter plasmas required for applications such as metrology.

266 nm ultraviolet light generation in Ga-doped BaAlBO3F2 crystals.

BaAlBO3F2 (BABF) crystals are a recently developed and promising nonlinear optical material, notably for the third harmonic generation of ultraviolet (UV) light at 355 nm. However, the fourth harmonic generation of UV light at 266 nm has never been obtained by using a BABF crystal due to its relatively small birefringence. We demonstrate that the birefringence of BABF can be effectively increased by doping it with Ga3+. The fourth harmonic generation of UV light at 266 nm was achieved for the first time in a Ga-doped BABF crystal.

Laser impact on a drop

First Page

Ultraviolet Light Generation in Gas-Filled Kagome Photonic Crystal Fiber

Kagome hollow-core photonic crystal fibers were found to be ideal for the occurrence of ultrafast non-linear optics. This article reports the optimal conditions for the generation of ultraviolet light using a gas filled kagome hollow-core-photonic crystal fiber. It is shown that by changing the pressure of the gas and the input pulse characteristics, the efficiency of conversion and quality of ultraviolet light can be improved, as well as tuning its central frequency. Results suggest that a highly coherent and tunable ultraviolet light source can be constructed, which can find numerous applications.

Graphene-containing plasma: a medium for the coherent extreme ultraviolet light generation

We demonstrate the high-order harmonic generation of femtosecond pulses in the laser ablation plume containing the graphene nanoparticles. The harmonics up to the 33rd order were observed. The presence of graphene nanoparticles in the laser plasma was confirmed during the analysis of ablation debris. The comparative studies of harmonic generation from the ablation of graphene, carbon nanotubes, and diamond nanoparticles showed the advanced properties of the latter medium.

Statistical uncertainty of 2.5×10−16for the199Hg1S0−3P0clock transition against a primary frequency standard

High-resolution spectroscopy has been carried out on the ${}^{199}Hg$ ${}^{1}{S}_{0}\ensuremath{-}{\phantom{\rule{0.16em}{0ex}}}^{3}{P}_{0}$ spin and dipole forbidden transition, where the atoms are confined in a vertical one-dimensional optical lattice trap using light at the magic wavelength. We describe various characteristics of the resulting line spectra and assess the strength of the Lamb-Dicke confinement. Through a series of absolute frequency measurements of the ${}^{199}Hg$ clock transition with respect to the LNE-SYRTE primary frequency standard, recorded over a 3-month period, we demonstrate a statistical fractional uncertainty of $2.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$. We include details relating to the generation of ultraviolet light at three wavelengths necessary for the experiment: 253.7 nm for cooling and detection, 265.6 nm for clock transition probing, and 362.570 nm for lattice trapping, along with further aspects related to the magic wavelength evaluation.

Generation of quasi-cw deep ultraviolet light below 200 nm by an external cavity with a Brewster-input KBBF prism coupling device

We report the generation of coherent deep ultraviolet light at 199nm with a maximum average power of 32mW by frequency quadrupling a picosecond pulse train from a Ti:sapphire laser. Two frequency-doubling stages were taking place in resonant cavities that can enhance conversion efficiency of second harmonic generations (SHGs). To reduce the extra-loss of the resonant cavity, a Brewster-input KBe2BO3F2 (KBBF) prism coupling device (PCD) was designed and employed in the second stage SHG for the first time.

Simultaneous generation of UV at 411 nm and red at 671 nm in a dual-structure periodically poled LiTaO3 crystal

A dual-color laser of red at 671 nm and ultraviolet (UV) at 411 nm was generated from dual-wavelength fundamental waves at 1342 and 1064 nm with a single periodically poled LiTaO3 (PPLT) optical superlattice. The PPLT sample used consists of two segments in a series: the first segment has a period of 14.55 μm for the second-harmonic generation (SHG) of 1342 nm and the second segment has periods of around 10.3 μm for the generation of UV light by sum-frequency mixing (SFG) of 1064 and 671 nm. An average output power of 3 and 79 mW for UV and red, respectively, has been obtained.

Broadly tunable ultraviolet light generation in a compact MgO-doped periodically-poled stoichiometric lithium tantalate optical parametric oscillator with a high-Q cavity

A compact tunable UV laser source based on intracavity sum frequency generation in a MgO-doped periodically-poled stoichiometric lithium tantalate optical parametric oscillator is reported. UV output at an approximately 1 mW level of power over the range of 364 to 378 nm with a bandwidth of 0.5 nm was obtained with a crystal that has just one periodically-poled grating period. The full tuning range can be as much as approximately 68 nm, from 324 to 392 nm by varying the crystal temperature from room temperature to 250 degrees C. This will cover nearly the entire UVA range.

UV laser-induced damage tolerance measurements of CsB 3O 5 crystals and its application for UV light generation

Cesium triborate, CsB 3O 5 (CBO), is an excellent nonlinear optical crystal for ultraviolet light generation. CBO crystals can be grown by top seeded solution growth from self flux solutions. The growth of large-size crystal is difficult because of the multi-nucleation and dissolution of seed during growth. These problems have been avoided and large size crystals (159.2 g) of size 50 × 45 × 45 mm 3 ( a × b × c) have been grown. The bulk laser-induced damage threshold (LIDT) of CBO was determined using an 1-on-1 technique by the third-harmonic (355 nm) light of longitudinal single-mode Q-switch Nd:YAG laser. The bulk LIDT was found to be two times that of fused quartz for a 6 ns pulse. The as-grown CBO crystal has been used to generate the highest ever reported third-harmonic power of 103 W for the case of a single-pass frequency-conversion system using a high-power Nd:YAG laser.

二极管泵浦Nd:YVO4晶体四倍频335.5nm紫外激光器

The generation of ultraviolet (UV) light at 335.5 nm based on frequency quadrupling of a diode-end-pumped Q-switched Nd:YVO4 laser at 1342 nm was demonstrated. KTP crystal was used for generation of wavelength of 671 nm by intracavity doubling and LBO (BBO) crystal was exploited for the subsequent external fourth harmonic generation (FHG). With 6.3-W absorbed pump power and 10-kHz frequency repetition rate, the UV output power of 35 and 63 mW were obtained by using LBO and BBO as frequency quadrupling nonlinear crystals, respectively. The experimental results show that the conversion efficiency (red-UV) of 6.4% for BBO crystal is higher than that of 3.5% for LBO crystal, but the UV beam quality obtained by LBO crystal is better than by BBO crystal.

Experimental study on extreme ultraviolet light generation from high power laser-irradiated tin slab

An experimental system has been set up for producing extreme ultraviolet light with high conversion efficiency by employing high power YAG laser irradiated tin slab. The dependence of extreme ultraviolet light intensity and conversion efficiency on the pump energy were studied， and the saturation effect of conversion efficiency was observed. The highest conversion efficiency of 1.6% in producing 13.5nm extreme ultraviolet light with 0.27nm bandwidth was achieved at pump energy of 250mJ, which corresponds to an intensity of 1.8×1011W/cm2.

Influence of 4-cyano-4′-biphenylcarboxylic acid on the orientational ordering of cyanobiphenyl liquid crystals at chemically functionalized surfaces

We report two methods that involve tailoring of the chemical composition of the nematic liquid crystal 4-cyano-4′-pentylbiphenyl to achieve control over the orientational ordering of the liquid crystal on chemically functionalized surfaces. The first method involves the direct addition of 4-cyano-4′-biphenylcarboxylic acid to 4-cyano-4′-pentylbiphenyl. The second method involves exposure of 4-cyano-4′-pentylbiphenyl to ultraviolet light and photochemical generation of a range of products, including 4-cyano-4′-biphenylcarboxylic acid. The addition of the acid or exposure to ultraviolet light accelerated the rate at which the liquid crystal exhibited an orientational transition from planar to perpendicular (homeotropic) alignment on surfaces presenting ammonium groups. The appearance of the homeotropic orientation of the UV-treated 4-cyano-4′-pentylbiphenyl on ammonium-terminated surfaces was dependent on the thickness of the film of liquid crystal (13–50 μm), consistent with a dipolar coupling between the liquid crystal and the electric field associated with an electrical double layer generated at the ammonium surface. Although the addition of 4-cyano-4′-biphenylcarboxylic acid or UV treatment of the liquid crystal also promoted homeotropic orientations on surfaces presenting hydroxyl groups, the orientations of the UV-treated liquid crystal on the hydroxyl-terminated surface did not change with thickness of the film of liquid crystal in the manner observed on the ammonium-terminated surfaces. The latter result indicates that the mechanism leading to homeotropic anchoring on hydroxyl-terminated surfaces is distinct from that on ammonium-terminated surfaces. Measurements performed using polarization modulation infrared reflection–absorption spectroscopy suggest that hydrogen bonding between the 4-cyano-4′-biphenylcarboxylic acid and the hydroxyl-terminated surface is responsible for the homeotropic anchoring on the surface. Finally, the orientation of the liquid crystal on methyl-terminated surfaces was not influenced by the addition of 4-cyano-4′-biphenylcarboxylic acid nor UV treatment. These results illustrate how the chemical composition of liquid crystals can be manipulated to achieve control over their ordering on surfaces that possess chemical functionality relevant to the development of liquid crystal-based sensors and diagnostic tools. We illustrate the utility of this approach by using the tailored liquid crystal to amplify and optically transduce the presence of proteins arrayed on ammonium-terminated surfaces.