B. M. Luther

Sub-38 nm resolution tabletop microscopy with 13 nm wavelength laser light

We have acquired images with a spatial resolution better than 38 nm by using a tabletop microscope that combines 13 nm wavelength light from a high-brightness tabletop laser and Fresnel zone plate optics. These results open a gateway to the development of compact and widely available extreme-ultraviolet imaging tools capable of inspecting samples in a variety of environments with a 15-20 nm spatial resolution and a picosecond time resolution.

Saturated high-repetition-rate 18.9-nm tabletop laser in nickellike molybdenum

We report saturated operation of an 18.9-nm laser at 5-Hz repetition rate. An amplification with a gain-length product GL of 15.5 is obtained in the 4d 1S0-4p 1P1 laser line of Ni-like Mo in plasmas heated at grazing incidence with approximately 1-J pulses of 8.1-ps duration from a tabletop laser system. Lasing is obtained over a broad range of time delays and pumping conditions. We also measure a GL of 13.5 in the 22.6-nm transition of the same ion. The results are of interest for numerous applications requiring high-repetition-rate lasers at wavelengths below 20 nm.

Dynamics of polar solvation in acetonitrile–benzene binary mixtures: Role of dipolar and quadrupolar contributions to solvation

While dynamics of polar solvation have been tabulated for a wide range of pure polar solvents, substantially less is known about the dynamic response of solvent mixtures. Here, results for polar solvation dynamics are presented for the nonassociating mixture of a dipolar solvent, acetonitrile, and a quadrupolar solvent, benzene. The solvation response observed is sensitive to the mixing of the pure solvents, affecting both the inertial and diffusive components of the solvation response function. Addition of acetonitrile to benzene increases the amplitude of the inertial response. At high benzene mole fractions, the diffusive relaxation reveals a slow component attributed to translational diffusion of the acetonitrile.

Demonstration of a 100 Hz repetition rate gain-saturated diode-pumped table-top soft x-ray laser

We demonstrate the operation of a gain-saturated table-top soft x-ray laser at 100 Hz repetition rate. The laser generates an average power of 0.15 mW at λ=18.9  nm, the highest laser power reported to date from a sub-20-nm wavelength compact source. Picosecond laser pulses of 1.5 μJ energy were produced at λ=18.9  nm by amplification in a Mo plasma created by tailoring the temporal intensity profile of single pump pulses with 1 J energy produced by a diode-pumped chirped pulse amplification Yb:YAG laser. Lasing was also obtained in the 13.9 nm line of Ni-like Ag. These results increase by an order of magnitude the repetition rate of plasma-based soft x-ray lasers opening the path to milliwatt average power table-top lasers at sub-20 nm wavelengths.

Demonstration of a compact 100 Hz, 0.1 J, diode-pumped picosecond laser

We have demonstrated an all-diode-pumped Yb:YAG chirped pulse amplification laser that produces 100 mJ pulses of 5 ps duration at 100 Hz repetition rate. The compact laser system combines a room-temperature Yb:YAG regenerative amplifier for increased bandwidth and a cryogenically cooled Yb:YAG four-pass amplifier for improved heat dissipation and increased efficiency. The optical efficiency of this amplifier is higher than that of other diode-pumped systems of comparable energy.

Demonstration of an all-diode-pumped soft x-ray laser.

We have demonstrated an 18.9 nm Ni-like molybdenum soft x-ray laser, pumped by a compact all-diode-pumped Yb:YAG laser. The solid-state pump laser produces 8.5 ps pulses with up to 1 J energy at 10 Hz repetition rate. This diode-pumped laser has the potential to greatly increase the repetition rate and the average power of soft x-ray lasers on a significantly smaller footprint.

High-energy 13.9 nm table-top soft-x-ray laser at 2.5 Hz repetition rate excited by a slab-pumped Ti:sapphire laser

We have demonstrated repetitive operation of a table-top lambda=13.9 nm Ni-like Ag soft-x-ray laser that generates laser pulses with 10 microJ energy. The soft-x-ray laser is enabled by a Ti:sapphire laser pumped by high-repetition-rate frequency-doubled high-energy Nd:glass slab amplifiers. Soft-x-ray laser operation at 2.5 Hz repetition rate resulted in 20 microwatt average power.

Large area high efficiency broad bandwidth 800 nm dielectric gratings for high energy laser pulse compression.

We have demonstrated broad bandwidth large area (229 mm × 114 mm) multilayer dielectric diffraction gratings for the efficient compression of high energy 800 nm laser pulses at high average power.

Quasi-elastic neutron scattering study of dimethyl-sulfoxide-water mixtures: probing molecular mobility in a nonideal solution.

The translational and rotational motions of water and dimethyl sulfoxide, [DMSO, (CH(3))(2)SO] have been investigated using quasi-elastic neutron scattering. Water-DMSO mixtures at five DMSO mole fractions, chi(DMSO), ranging from 0 to 0.75, were measured. Hydrogen-deuterium substitution was used to extract independently the water proton dynamics (d-DMSO-H(2)O), the DMSO methyl proton dynamics (h-DMSO-D(2)O) and to obtain background corrections (d-DMSO-D(2)O). The translational diffusion of water slows down significantly compared to bulk water at all chi(DMSO)>0. The rotational time constant for water exhibits a maximum at chi(DMSO)=0.33 that corresponds to the observed maximum of the viscosity of the mixture. Data for DMSO can be analyzed in terms of a relatively slow tumbling of the molecule about its center-of-mass in conjunction with random translational diffusion. The rotational time constant for this motion exhibits some dependence on chi(DMSO), while the translational diffusion constant shows no clear variation for chi(DMSO)>0. The results presented reinforce the idea that due to the stronger associative nature of DMSO, DMSO-water aggregates are formed over the whole composition range, disturbing the tetrahedral natural arrangement of the water molecules. As a consequence adding DMSO to water causes a drastic slowing down of the dynamics of the water molecule, and vice versa.

Development of High Energy Diode-Pumped Thick-Disk Yb:YAG Chirped-Pulse-Amplification Lasers

We discuss the results of work directed toward the development of high energy (>;1 J), high average power, diode-pumped picosecond lasers. The design and operation of diode-pumped chirped-pulse-amplification Yb:YAG lasers that combine either room temperature or cryogenically-cooled regenerative amplifiers with cryo-cooled power amplifiers for superior thermal performance and efficient energy extraction are discussed. Results obtained using thick-disk amplifiers include the generation of 100 mJ, 5-ps duration laser pulses at 100-Hz repetition rate, and 1-J pulses of 8.5-ps duration at 10-Hz repetition rate. The performance of the amplifiers in terms of pulse energy and bandwidth under a variety of pump condition is presented.