Dale Martz

Demonstration of a desk-top size high repetition rate soft x-ray laser.

We have demonstrated a new type of high repetition rate 46.9 nm capillary discharge laser that fits on top of a small desk and that it does not require a Marx generator for its excitation. The relatively low voltage required for its operation allows a reduction of nearly one order of magnitude in the size of the pulsed power unit relative to previous capillary discharge lasers. Laser pulses with an energy of ~ 13 microJ are generated at repetition rates up to 12 Hz. About (2-3) x 10 4 laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications.

Single-shot extreme ultraviolet laser imaging of nanostructures with wavelength resolution

We have demonstrated near-wavelength resolution microscopy in the extreme ultraviolet. Images of 50 nm diameter nanotubes were obtained with a single ~1 ns duration pulse from a desktop-size 46.9 nm laser. We measured the modulation transfer function of the microscope for three different numerical aperture zone plate objectives, demonstrating that 54 nm half-period structures can be resolved. The combination of near-wavelength spatial resolution and high temporal resolution opens myriad opportunities in imaging, such as the ability to directly investigate dynamics of nanoscale structures.

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.

Gain-saturated 10.9 nm tabletop laser operating at 1 Hz repetition rate

We report the demonstration of a gain-saturated 10.9 nm tabletop soft x-ray laser operating at 1 Hz repetition rate. Lasing occurs by collisional electron impact excitation in the 4dS01-->4pP11 transition of nickel-like Te in a line-focus plasma heated by a chirped-pulse-amplification Ti:sapphire laser. With an average power of 1muW and pulse energy up to approximately 2microJ, this laser extends the ability to conduct tabletop laser experiments to a shorter wavelength.

Temporal coherence and spectral linewidth of an injection-seeded transient collisional soft x-ray laser

The temporal coherence of an injection-seeded transient 18.9 nm molybdenum soft x-ray laser was measured using a wavefront division interferometer and compared to model simulations. The seeded laser is found to have a coherence time similar to that of the unseeded amplifier, ~1 ps, but a significantly larger degree of temporal coherence. The measured coherence time for the unseeded amplifier is only a small fraction of the pulsewidth, while in the case of the seeded laser it approaches full temporal coherence. The measurements confirm that the bandwidth of the solid target amplifiers is significantly wider than that of soft x-ray lasers that use gaseous targets, an advantage for the development of sub-picosecond soft x-ray lasers.

Improved beam characteristics of solid-target soft x-ray laser amplifiers by injection seeding with high harmonic pulses

Injection seeding of solid-target soft x-ray laser amplifiers with high harmonic pulses is shown to dramatically improve the far-field laser beam profile and reduce the beam divergence. Measurements and two-dimensional simulations for a 13.9 nm nickel-like Ag amplifier show that the amplified beam divergence depends strongly on the seed and can therefore be controlled by selecting the divergence of the seed. The near-field beam size of both the seeded and unseeded lasers is shown to be determined by the size of the gain region and the divergence of the amplified beams.

Extreme ultraviolet laser-based table-top aerial image metrology of lithographic masks

We have realized the first demonstration of a table-top aerial imaging microscope capable of characterizing pattern and defect printability in extreme ultraviolet lithography masks. The microscope combines the output of a 13.2 nm wavelength, table-top, plasma-based, EUV laser with zone plate optics to mimic the imaging conditions of an EUV lithographic stepper. We have characterized the illumination of the system and performed line-edge roughness measurements on an EUVL mask. The results open a path for the development of a compact aerial imaging microscope for high-volume manufacturing.

Interferometric lithography with an amplitude division interferometer and a desktop extreme ultraviolet laser

We demonstrate a compact interferometric lithography nanopatterning tool based on an amplitude division interferometer (ADI) and a 46.9 nm wavelength desktop size capillary discharge laser. The system is designed to print arrays of lines, holes, and dots with sizes below 100 nm on high resolution photoresists for the fabrication of arrays of nanostructures with physical and biological applications. The future combination of this ADI with high repetition rate tabletop lasers operating at shorter wavelengths should allow the printing of arrays of sub-10 nm size features with a tabletop setup.

Characterization of focused beam of desktop 10-Hz capillary-discharge 46.9-nm laser

The desktop capillary-discharge Ne-like Ar laser (CDL) providing 10-μJ nanosecond pulses of coherent 46.9-nm radiation with a repetition rate up to 12 Hz was developed and built at the Colorado State University in Fort Collins and then installed in Prague. The beam of the laser was focused by a spherical mirror covered with Si/Sc multilayer coating onto the surface of poly(methyl methacrylate) - PMMA. Interaction parameters vary by changing the distance between sample surface and beam focus. The samples were exposed to various numbers of shots. Analysis of damaged PMMA by atomic force (AFM) and Nomarski (DIC - differential interference contrast) microscopes allows not only to determine the key characteristics of the focused beam (e.g. Rayleighs parameter, focal spot diameter, tight focus position, etc.) but also to investigate mechanisms of the radiation-induced erosion processes.