Influence of deposition parameters on composition and refractive index of femtosecond and nanosecond pulsed laser deposited gallium lanthanum oxysulphide

The influence of the deposition parameters on femtosecond and nanosecond pulsed laser deposited gallium lanthanum oxysulphide (GLSO) glass films has been investigated. A comparison between films deposited by femtosecond and nanosecond pulsed laser deposition (PLD) shows that the compositional range of each ablation regime varies significantly; in particular, femtosecond PLD shows a unique potential for selective fabrication of films with a high lanthanum content well outside the conventional glass-melting region. We demonstrate how manipulation of the PLD growth parameters can influence the stoichiometric transfer of the PLD process, leading to films with compositions that differ significantly from the GLSO target material. We also reveal how the refractive index of as-deposited films is dependent upon the composition and briefly discuss the thermal properties of bulk GLSO material of various compositions which indicate the potential for films grown by PLD to be used in optical data-storage device applications.     

Generation of bright monomeric red fluorescent proteins via computational design of enhanced chromophore packing

Red fluorescent proteins (RFPs) have found widespread application in chemical and biological research due to their longer emission wavelengths. Here, we use computational protein design to increase the quantum yield and thereby brightness of a dim monomeric RFP (mRojoA, quantum yield = 0.02) by optimizing chromophore packing with aliphatic residues, which we hypothesized would reduce torsional motions causing non-radiative decay. Experimental characterization of the top 10 designed sequences yielded mSandy1 (λ_em = 609 nm, quantum yield = 0.26), a variant with equivalent brightness to mCherry, a widely used RFP. We next used directed evolution to further increase brightness, resulting in mSandy2 (λ_em = 606 nm, quantum yield = 0.35), the brightest Discosoma sp. derived monomeric RFP with an emission maximum above 600 nm reported to date. Crystallographic analysis of mSandy2 showed that the chromophore p-hydroxybenzylidene moiety is sandwiched between the side chains of Leu63 and Ile197, a structural motif that has not previously been observed in RFPs, and confirms that aliphatic packing leads to chromophore rigidification. Our results demonstrate that computational protein design can be used to generate bright monomeric RFPs, which can serve as templates for the evolution of novel far-red fluorescent proteins.

We used computational design to increase quantum yield in a fluorescent protein by optimizing chromophore packing to reduce non-radiative decay, resulting in an >10-fold increase in quantum yield that was further improved by directed evolution.     

The effect of doping and processing conditions on the optical performance of Rh:BaTiO3

We demonstrate the advantages of using high levels of rhodium (2000–3200 ppm) to dope barium titanate for achieving finite absorption coefficients (0.36 cm^-1), high two-beam coupling gain (11.5 cm^-1), and acceptable response time (7 s) at 1.06 μm. We also report on the mass spectroscopy measurements on Rh:BaTiO₃ samples indicating a small segregation coefficient for rhodium (below 0.01) and the presence of a relatively large concentration (6000 ppm) of unintentionally added strontium. Received: 20 November 1998 / Revised version: 25 January 1999 / Published online: 12 April 1999     

Large photoinduced refractive index changes in pulsed-laser-deposited lead germanate glass waveguides with controllable refractive index sign change

Photosensitive lead germanate glass optical waveguides have been grown by pulsed laser deposition. The deposited waveguides are photosensitive over a broad ultraviolet spectral range (325-193 nm). Positive and/or negative refractive index changes have been observed, depending on the intensity of the ultraviolet radiation as well as on the deposition conditions. Absolute refractive index change values up to |(n|=1.06᎒^-2 have been measured.     

Feedback-controlled electro-kinetic traps for single-molecule spectroscopy

A principal limitation of single-molecule spectroscopy in solution is the diffusion-limited residence time of a given molecule within the detection volume. A common solution to this problem is to immobilize molecules of interest on a passivated glass surface for extending the observation time to obtain reliable data statistics. However, surface tethering of molecules often introduces artifacts, particularly when studying the structural dynamics of biomolecules. To circumvent this limitation, we investigated alternative ways to extend single-molecule observation times in solution without surface immobilization. Among various possibilities, the so-called anti-Brownian electro-kinetic trap (or ABEL trap) seems best suited to achieve this goal. The essential part of that trap is a feedback-controlled electro-kinetic steering of a molecule’s position in reaction to its diffusive Brownian motion which is monitored by fluorescence, thus keeping the molecule within a sub-micron sized detection volume. Fluorescence trace recordings of over thousands of milliseconds duration on individual dye molecules within an ABEL trap have been reported. In this short review, we shall briefly discuss the principle and some results of ABEL trapping of individual molecules with possible extensions to future works.     

The Role of Lignocellulosic Composition and Residual Lipids in Empty Fruit Bunches on the Production of Humic Acids in Submerged Fermentations

The aim of this research was to study the production of humic acids (HA) by Trichoderma reesei from empty fruit bunches (EFBs) of palm oil processing, with a focus on the effects of lignocellulosic content and residual lipids. EFBs from two different soils and palm oil producers were previously characterized about their lignocellulosic composition. Submerged fermentations were inoculated with T. reesei spores and set up with or without residual lipids. The results showed that the soil and the processing for removal of the palm fresh fruits were crucial to EFB quality. Thus, EFBs were classified as type 1 (higher lignocellulosic and fatty acids composition similar to the palm oil and palm kernel oil) and type 2 (lower lignocellulosic content and fatty acids composition similar to palm oil). Despite the different profiles, the fungal growth was similar for both EFB types. HA production was associated with fungal growth, and it was higher without lipids for both EFBs. The highest HA productivity was obtained from type 1 EFB (approximately 90 mg L⁻¹ at 48 h). Therefore, the lignocellulosic composition and the nature of the residual lipids in EFBs play an important role in HA production by submerged fermentation.

     

Self-ordered sub-micron structures in Fe-doped LiNbO3 formed by light-induced frustration of etching

We have produced millimetre-sized areas of self-ordered, sub-micron scale, complex structures in iron-doped single crystal lithium niobate, using the combined interaction of laser light and etching with acid. We report here the factors that influence the formation of the structures, and illustrate the types of structure that may be formed, using images taken by a scanning electron microscope (SEM) and subsequent Fourier Transform analysis of those images. We also consider the physical processes which initiate and control the growth of the structures.     

Inclusive production of K̄1(890) and K̄1(1420) in K̄−p interactions at 10 and 16 GeV/c

The inclusive production of K?¹(890) and K?¹(1420) is studied in K?^?p interactions at 10 and 16 GeV/c. At 10 GeV/c an enhancement in the ($\text{K}\text{?}{}^0\text{π}{}^{\mathrm{?}}$) mass distribution is found at 1.74 GeV, but no clear signal is seen at 16 GeV/c. The fraction of $\text{K}{}^0\text{'}\text{s}$ coming from decay of the $\text{K}{}^1\text{(890)}\text{or}\text{K}{}^1\text{(1420)}$ is large, being (50 ± 6)% and (45 ± 5)% at 10 and 16 GeV/c, respectively. The inclusive cross sections for K^1?(890) and $\text{K}{}^{10}\text{(890)}$ production are almost constant with energy from 8 to 32 GeV/c with values of 3.5 and 3.3 mb, respectively. The $\text{K}{}^1\text{(890)}$ production cross section is studied as a function of transverse and longitudinal variables and found to derive mainly from fragmentation of the incident K^? meson. The spectra of $\text{K}{}^0\text{'}\text{s}$ resulting from the decay of $\text{K}{}^1\text{(890)}$ are studied.     

Two-body hypercharge-exchange reactions in K−p and π+p interactions at 10 and 16 GeV/c

Cross-section values or upper limits are presented for twenty-five two-body hypercharge-exchange reactions in K^?p and π⁺p interactions at 10 and 16 GeV/c. The 16 GeV/c results are compared with some predictions of line-reversal plus exchange-degenerate Regge poles, of SU(3) and of the additive quark model. Agreement is found in all cases.     

Performance of a low-loss pulsed-laser-deposited Nd:Gd(3) Ga(5)O(12) waveguide laser at 1.06 and 0.94 mum

We report the laser performance of a low-propagation-loss neodymium-doped Gd(3)Ga(5)O(12) (Nd:GGG) waveguide fabricated by pulsed-laser deposition. An 8- mum -thick crystalline Nd:GGG film grown upon an undoped Y(3)Al(5)O(12) substrate lases at 1.060 and 1.062 microm when pumped by a Ti:sapphire laser operating at 740 or 808nm.Using a 2.2% output coupler, we observed a 1060-nm laser threshold of 4mW and a slope efficiency of 20%. Laser action was also achieved, for what we believe is the first time in Nd:GGG, on the quasi-three-level 937-nm transition. With a 2% output coupler at this wavelength a laser threshold of 17mW and a 20% slope efficiency were obtained. This demonstration of low propagation loss combined with the fact that these waveguides have a very high numerical aperture (0.75) makes pulsed-laser-deposited thin films attractive for high-power diode-pumped devices.