Browsing by Author "Rocca, Jorge J., advisor"
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Item Open Access Characterization of laser-produced plasmas as light sources for extreme ultraviolet lithography and beyond(Colorado State University. Libraries, 2019) Yin, Liang, author; Rocca, Jorge J., advisor; Menoni, Carmen S., committee member; Marconi, Mario C., committee member; Yalin, Azer, committee memberLithography is a critical process in the fabrication of integrated circuits. The continuous increase in computing power for more than half a century has depended in the ability to print smaller and smaller features, which has required the use of light sources operating at increasingly shorter wavelengths. There is keen interest in the development of high-power light sources for extreme ultraviolet (EUV) lithography at λ=13.5 nm and future beyond extreme ultraviolet (BEUV) lithography near λ=6.7 nm. The work conducted in this dissertation has characterized aspects of laser-produced plasmas (LPPs) that serve as light sources for EUV / BEUV lithography. The laser pulse shape dependence of the conversion efficiency of λ=1.03 μm laser into in-band 13.5 nm EUV emission in a Sn LPP was studied as a function of laser pulse shape and durations. Laser pulses of arbitrary temporal shape with variable energy and pulse widths were generated using a programmable pulse synthesizer based on a diode-pumped chirped pulse amplification Yb: YAG laser. The pulse synthesizer is based on wave front splitting and pulse stacking for the generation of arbitrary shape laser pulses of Joule-level energy. Pulses ranging from hundreds of ps to several ns were generated with a single laser. The measurements showed the CE favors the use of nearly square pulses of duration longer than 2 ns, in agreement with hydrodynamic/atomic physics simulations. A significant increase in CE was observed when Q-switched pulses were substituted by square pulses of similar duration. Conditions were observed at which the EUV pulse duration significantly outlasts the laser pulse in the direction normal to the target surface, in contrast at grazing angles the measured EUV pulse duration is shorter and similar to the laser pulse duration. The physics leading to this angular anisotropy is discussed, along with the spectroscopic characterization of EUV emission and at-wavelength images that characterize the source size. Another aspect of this dissertation includes a comprehensive study of the emission from Gd and Tb LPPs in the λ=6.5 - 6.7 nm region. BEUV emission spectra were measured as a function of laser pulse duration (120 ps - 4 ns), emission angle, and spatial location within the plasma. At-wavelength images of the BEUV emitting plasma region were obtained as a function of irradiation parameters. The peak of the emission spectrum was observed to broaden and to shift to longer wavelengths as the laser pulses are shortened from ns to hundreds of ps. Transient self-consistent hydrodynamic/atomic physics simulations show that the picosecond irradiation creates significantly hotter plasmas in which the dominant emission originates from more highly ionized species. Gd LPP emission driven by nanosecond laser pulses best matched the reflectivity band of our La/B4C mirrors. Spatially resolved spectra of the Gd LPP were acquired for different laser parameters and were compared to simulations. The CE into in-band BEUV emission was determined by integrating angularly resolved measurements obtained using an array of calibrated energy monitors. A maximum CE of 0.47% / 0.45% for the Gd / Tb LPPs was obtained within a 0.6% bandwidth. The results are of potential interest BEUV lithography.Item Open Access Desk-top size high repetition rate 46.9 NM capillary discharge laser as photoionization source for photochemistry applications(Colorado State University. Libraries, 2006) Heinbuch, Scott, author; Rocca, Jorge J., advisorA portable high repetition rate desktop-size capillary discharge laser emitting at a wavelength of 46.9 nm (26.5 eV photon energy) was demonstrated and used as a photoionization source in nanocluster mass spectroscopy. The high photon energy allows the single-photon ionization of nanoclusters and other molecules, which, due to their high ionization potential, would otherwise require undesirable multi-photon ionization. This Ne-like Ar capillary discharge laser occupies a table area of approximately 0.4 x 0.4 m², smaller than that occupied by many widely used ultraviolet gas lasers. The laser's power supplies and gas handling system are designed to fit into small racks that can be placed underneath a standard optical table. The main spark-gap is electrically triggered to allow synchronization of the laser pulses with those of other lasers in photochemistry applications. Experiments were performed to characterize the laser output energy, average power and timing jitter. Tests were conducted to determine the capillary lifetime. Laser pulses with energy ~ 13 μJ were generated at 12 Hz repetition rate by single pass amplification in a 21 cm long Ne-like Ar capillary discharge plasma column. The standard deviation of the jitter was found to be 5 ns. Capillary lifetime tests at 12 Hz repetition rate determined that the laser output energy decays by a factor of two after about 2 10⁴ - 3 10⁴ shots. The laser was installed in a photochemistry laboratory where it is operated for many hours on a daily basis. The laser was successfully used as a single photon photoionization source for the study of hydrogen bonded nanoclusters and other small molecules using time of flight mass spectroscopy. The first mass spectra of water nanoclusters and other small molecules using this source have been obtained.Item Open Access Development of a high energy TI:Sapphire laser for the excitation of extreme ultraviolet lasers(Colorado State University. Libraries, 2011) Martz, Dale Herman, author; Rocca, Jorge J., advisor; Lee, Siu Au, committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee memberThis dissertation describes the design, construction and characterization of a high energy chirped-pulse amplification Titanium-Sapphire laser system for the excitation of Extreme Ultraviolet (EUV) lasers. Compact EUV lasers have made possible nano-scale imaging, dense plasma diagnostics and photo-chemistry and photo-physics studies. They also have the potential to make possible a variety of new studies of surfaces and materials and enable the development of unique metrology and processing tools for industry. The components developed to realize high energy operation of the Titanium-Sapphire laser include the development of a Nd:Glass zig-zag slab pump laser and novel 800 nm multi-layer dielectric diffraction gratings for picosecond compression. The Titanium-Sapphire laser was used to pump several table-top EUV lasers. Increased average power operation of a 13.9 nm nickel-like silver laser generating 20 uW was demonstrated. This is the highest average power obtained from a compact EUV laser to date. Injection seeding of the 13.9 nm EUV amplifier produced laser beams with greatly improved beam characteristics which includes a large reduction in beam divergence and a near Gaussian far-field profile. The laser was also used to pump a gain-saturated table-top laser at 10.9 nm in nickel-like tellurium.Item Open Access Development of a petawatt class Ti:Sapphire laser for the excitation of extreme radiation sources(Colorado State University. Libraries, 2020) Rockwood, Alex Pratt, author; Rocca, Jorge J., advisor; Lee, Siu Au, committee member; Roberts, Jacob L., committee member; Marconi, Mario C., committee memberThis dissertation describes the design, construction and characterization of a high peak power, high repetition rate, Titanium-Sapphire laser system. This chirped-pulse amplification (CPA) laser delivers femtosecond pulses of up to 0.85 PW peak power. By utilizing pump laser amplifiers with a slab configuration high repetition rate are achieved, 3.3Hz, the highest at which Petawatt-class lasers have been operated to date. This 800nm laser also has a high power, ultra-high contrast 400 nm beamline. By frequency doubling the 800 nm with a KDP crystal at ≥ 40% conversion we are able to achieve a contrast of > 1 × 10-12. The ability to focus this second harmonic beam to ~1.2 μm Full Width at Half Maximum (FWHM) spot size made it possible to achieve intensities up to ~ 6.5 ×1021 W/cm2. With these high intensities and high contrast this laser is a powerful tool in many applications especially in the study of laser/matter interactions at relativistic plasmas. This Ti:Sapphire laser was used for the excitation of plasma based soft x-ray (SXR) lasers. prior to this work compact, repetitively fired, gain-saturated x-ray lasers had been limited to wavelengths above λ = 8.85 nm. We were able to demonstrate SXR lasers operating in the gain-saturated regime down to wavelengths as low as λ = 6.85 nm in Ni-like Gd. Gain was also observed at λ = 6.4 nm, and λ = 5.8 nm in Ni-like Dy. As an application of plasma-based SXR lasers, single shot Fourier holograms covering a large area of view were demonstrated using an 18.9nm laser with high spatial coherence based on dual plasma amplifier. Compact SXR lasers have made possible applications in nano-scale imaging, dense plasma diagnostics and a variety of new studies of materials and surfaces. Other applications that were enabled by this Petwatt-class laser discussed elsewhere include the study of the interaction of relativistic laser pulses with aligned nanostructures, producing record conversion efficiency of optical laser light into picosecond x-ray pulses with photons of > 1 KeV energy and flashes of deuterium-deuterium fusion neutrons.Item Open Access Development of a very compact high repetition rate soft x-ray laser(Colorado State University. Libraries, 2010) Furch, Federico Juan Antonio, author; Rocca, Jorge J., advisor; Marconi, Mario, advisorOver the last 25 years, the field of soft x-ray lasers has evolved from facility size devices delivering a few shots per day, to table-top lasers operating at several shots per second. In these lasers the gain medium is a highly ionized, hot and dense plasma created by a sequence of short, high energy pulses from an optical laser. Current table-top soft x-ray lasers have enabled numerous applications such as nano-scale imaging, nano-fabrication and dense plasma diagnosis among others. However these lasers are still limited in repetition rate, and therefore average power, owing to thermal effects originated in the flash lamp pumped amplifiers of the optical driver laser. Direct diode-pumping of the driver laser opens the possibility of developing more compact, higher repetition rate optical laser systems to pump soft x-ray lasers. Directly pumping small quantum defect materials such as Yb:YAG with a narrow bandwidth source of the optimum wavelength allows to significantly increase the efficiency and then reduce the thermal load in the gain materials. In addition, cryogenic cooling of the laser materials significantly improves their thermal performance. This approach will allow for soft x-ray laser operation at much higher repetition rates. In this work I present the results of the demonstration of an all diode-pumped soft x-ray laser that constitutes the first of a new generation of more compact, higher repetition rate soft x-ray lasers in the spectral region between 10 and 20 nm. To pump these lasers we developed an all diode-pumped chirped pulse amplification laser system based on cryogenically cooled Yb:YAG. This optical laser generates pulses of 1 J of energy in 8.5 ps pulses at 10 Hz, the highest energy per pulse for sub-10 ps pulses from a diode-pumped system at the present time. This soft x-ray laser has the potential to operate at unsurpassed repetition rates in a reduced footprint.Item Open Access Fast electronic driver for optical switches(Colorado State University. Libraries, 2012) Woolston, Mark R., author; Rocca, Jorge J., advisor; Marconi, Mario C., committee member; Menoni, Carmen S., committee member; Yalin, Azer P., committee memberElectronically controlled optical switches are critical components in many optical systems, including pulsed lasers. Solid-state optical switches based upon the Pockels effect are widely utilized in research and industry, however Pockels cells require electronic drivers capable of switching several kilovolts quickly and cleanly. This thesis reviews Pockels cell designs and their typical applications in laser systems, discusses common drive circuit topologies found in literature, and describes the development of a fast, stable electronic driver for half-wave congured Pockels cell optical switches. In a crowded optical environment, it is frequently desirable to locate the Pockels cell at some distance from the driver electronics. The driver was developed to be capable of 1.4 ns optical transition times when connected to a 6 pF Pockels cell via 1.2 meters of 50 ohm coaxial cable. The driver is designed to operate in colliding-pulse mode at 6-8 kV, with 80 ampere typical switch currents. Total switch propagation delay is less than 100 ns, and thermal drift has been measured at less than 50ps/C°. These pulsers are currently used to drive Pockels cells in colliding pulse mode in pulse picking and slicing applications where optical rise times of < 2 ns and low drift are needed. Novel non-invasive diagnostic techniques for measuring and graphing pulse propagation in a repeatable manner along collapsing avalanche transistor chains are presented.Item Open Access Gain-saturated repetetive soft X-ray lasers with wavelengths spanning 9-30 nm and lasing down to 7.4 nm(Colorado State University. Libraries, 2011) Alessi, David Alan, author; Rocca, Jorge J., advisor; Lee, Siu Au, committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee memberThis dissertation describes the development of table-top soft X-ray lasers with wavelengths ranging from 30 nm to 7.4 nm. The laser transisitons occur within collisionally excited states of nickel-like and neon-like ions which are created from laser ablation of solid targets. A Nd:glass slab laser system was developed to provide 20J (and then upgraded to 40J) of laser light at 527 nm for pumping a table-top chirped pulse amplification Ti:sapphire laser. With this increase in pump energy, the Ti:sapphire system is capable of producing 12J uncompressed laser pulses at a 1Hz repetition rate. Stretched and compressed pulses from this Ti:sapphire laser system operating near 800 nm are used to both ionize the material to a high degree and heat the free electrons in these plasmas to temperatures required for high gain. Simulations from a 1.5D hydrodynamic/atomic model indicate a peak gain of 90 cm-1 for the 8.8 nm laser transition in nickel-like lanthanum is reached with an electron temperature of ~850 eV and a density of 6×1020 cm-3. By using the grazing incidence pumping geometry, gain saturated operation was demonstrated in the 2p53p 1S0 →2p5 3s 1P1 transition of neon-like titanium (λ = 32.6 nm) and vanadium (λ = 30.4 nm), as well as in the 3d94d1S0→3d9 4p1P1 transition in nickel-like tellurium (λ = 10.9 nm) and lanthanum (λ = 8.8 nm). Strong lasing was also demonstrated in the same neon-like transition in chromium (λ = 28.6 nm), as well as the same nickel-like transition in cerium (λ = 8.5 nm), praseodymium (λ = 8.2 nm), neodymium (λ = 7.9 nm) and samarium (λ = 7.4 nm). This is the first demonstration of the generation of bright gain-saturated sub-9-nm wavelengths with a table-top laser operating at 1-Hz repetition rate. The short wavelength, microjoule pulse energy, picosecond pulse duration and repetitive operation of these lasers will enable new applications such as sequential imaging of ultrafast nano-scale dynamic phenomena to be realized on a table top.Item Open Access Highly relativistic laser interactions with ordered nanostructures(Colorado State University. Libraries, 2019) Hollinger, Reed, author; Rocca, Jorge J., advisor; Prieto, Amy L., committee member; Menoni, Carmen, committee member; Marconi, Mario, committee memberHeating high density matter to extreme temperatures has been one of the primary motivations behind the construction of high power laser facilities around the world. The creation of simultaneously hot (multi-keV) and dense (on the order of a solid) plasma with small scale and mid-scale lasers is a difficult problem due to the barrier that the critical electron density imposes to optical lasers, typically limiting the heating to a very thin plasma into which the laser is inefficiently coupled. Experiments conducted at Colorado State University with joule level laser pulses have demonstrated that using high contrast, relativistic laser pulses it is possible to efficiently heat near solid density nanowire arrays volumetrically to multi-keV temperatures. This dissertation extends these results to the highly relativistic regime, demonstrating extremely high ionization states for volumes >5μm in depth. These relatively large volume plasmas have longer hydrodynamic cooling times while their radiative cooling time is greatly decreased due to the near solid electron densities. This results in very efficient conversion of optical laser light into x-rays since the plasma is able to radiate away more of its' energy as x-rays before cooling due to hydrodynamic expansion. With this technique, an x-ray conversion efficiency of nearly 20% was measured for photon energies greater than 1keV. After a significant upgrade to the laser, these interactions were explored at highly relativistic intensities up to 4x1021 Wcm−2, nearly 1000 times higher than initial experiments. Measurements of the energy deposition dynamics, including the time limit for energy coupling and the volume of the nanowire plasma were carried out in comparison to solid targets. The results show that at these intensities, it is possible to generate unprecedented degrees of ionization never before obtained with ultrashort pulse lasers, such as H-like Ni (27 times ionized) and Ne-like Au (69 times ionized).Item Open Access Lasing at 52.9 nm in Ne-like chlorine and steps towards shorter wavelength capillary discharge lasers(Colorado State University. Libraries, 2001) Frati, Maximo, author; Rocca, Jorge J., advisor; Wilbur, Paul, committee memberSignificant advances have been obtained in the past few years in the development of soft x-ray lasers. Both, laser-pumped and discharge-pumped schemes have been successfully demonstrated. In particular, a very compact capillary discharge laser has been demonstrated to deliver an average power of several mW in the 46.9 nm line of Ne-like Ar. The work presented in this thesis, that was motivated by the possibility extending the very practical discharge excitation scheme to other short wavelengths laser transitions, can be divided in two parts. The first resulted in the successful demonstration of amplified spontaneous emission in the 3 p ¹Sₒ - 3s ¹P₁ transition of Ne-like Cl at 52.9 nm. Laser pulses of ~1.5 ns duration with energies up to 10 μJ and a beam divergence 4 mrad were obtained at repetition rates of 0.5 - 1 Hz. This new 23.4 eV table top laser is of particular interest for applications requiring high peak fluxes of photons with energy slightly below the He photoionization threshold. The results discussed in the second part of this thesis represent the first steps necessary for the development of a discharge-pumped Ni-like Cd laser at 13.2 nm. A room temperature source of atomically pure Cd vapor was developed and used to inject Cd into the capillary channel, where it was excited by a fast high current pulse to produce a hot dense plasma. The first spectroscopic data of a capillary discharge plasma containing Ni-like Cd ions (Cdₓₓᵢ) was obtained and analyzed. These results can be of use in future works when trying to develop a collisionally excited discharge-pumped Ni-like Cd laser.Item Open Access Modeling of laser-created plasmas and soft x-ray lasers(Colorado State University. Libraries, 2010) Berrill, Mark Allen, author; Rocca, Jorge J., advisor; Marconi, Mario C., committee member; Menoni, Carmen S., committee member; Lee, Siu Au, committee memberThis dissertation describes the development of computer models to simulate laser created plasmas used to generate soft x-ray lasers. These compact short wavelength lasers have substantial average powers and very high peak brightness, that make them of significant interest for many applications. A better understanding of the plasmas is necessary to advance the development of these lasers into more compact, efficient, and higher power sources of coherent soft x-ray light. The plasma phenomena involved are complex, and require a detailed computer model of the coupled magneto-hydrodynamic and atomic physics processes to simulate their behavior. The computer models developed as part of this work consist of hydrodynamic equations, coupled with an atomic model, radiation transport, and a ray propagation equation. The models solve the equations in a 1.5D or 2D approximation, and predict the spatio-temporal plasma variation of the parameter s, including the electron density and temperature, and the ion populations, which are then used to compute the population inversion and the resulting laser gain. A 3D post processor ray trace code was developed to simulate the amplification of stimulated emission along the plasma column length including saturation effects. This allows for the direct calculation of the soft x-ray laser output and its characteristics. Simulation results were compared with experiments conducted at Colorado State University. The general behavior of the plasma and the soft x-ray laser are well described by the model. A specific comparison of the model results with experimental measurements is presented for the case of a collisionally excited 13.2 nm wavelength Ni-like cadmium laser. The model predicts that an optical laser pulse of 1 J energy and 8 ps duration impinging at 23 degrees grazing incidence into a pre-created laser plasma can rapidly heat it to temperatures above 600 eV at a density of 2 x 1020 electrons/cm3. This results in a computed peak small signal gain coefficient of 150 cm-1 in the 4d 1S0 to 4p 1P1 transition of Ni-like Cd at 13.2 nm. The model indicates that the amplified beam reaches the gain-saturated regime after 2.5 mm of propagation in the plasma, in agreement with the experimental observation of saturated behavior for propagation lengths of 2.5-3.0 mm. The computed soft x-ray laser pulse width of 5-9 ps moderately exceeds the experimental value of 5 ps and is the result of a stronger saturation broadening in the simulation. The simulated laser output energy of the order of 1 μJ is also in agreement with experiments. Simulations of injection-seeded Ne-like Ti and Ni-like Ag amplifiers that show very good agreement with the experimental results are presented. A direct comparison of the pulsewidth and the near and far-field beam profiles is made. Finally, the results of a simulation of a plasma created by irradiation of solid targets with a 46.9 nm soft x-ray laser, in which single photon photoionization is the dominant energy absorption mechanism are presented. Low absorption (silicon, Z=14) and high absorption (chromium, Z=24) targets were heated by ~1 ns duration soft x-ray laser pulses. The experimental spectra agree with 1 ½ D simulations in showing that the Si plasmas are significantly colder and less ionized than the Cr plasma, confirming that in contrast to plasmas created by visible wavelength lasers the plasma properties are largely determined by the absorption coefficient of the target material.Item Open Access Nanometer-scale machining with extreme ultraviolet lasers(Colorado State University. Libraries, 2013) Bravo, Herman, author; Yalin, Azer, advisor; Rocca, Jorge J., advisor; Marconi, Mario, committee memberThis thesis demonstrates the feasibility of direct machining in the nanometer scale using Extreme Ultraviolet (EUV) laser radiation. Laser machining of materials has been widely used for the development of micromechanical components and devices. Advances in technology further motivate the extension of laser machining of microstructures to smaller dimensions. The advent of high repetition rate table top EUV lasers has opened the possibility of extending laser machining to the nanometer-scale. It has been previously demonstrated that single laser shots from a 46.9 nm wavelength capillary discharge laser can ablate very clean holes with a diameter as small as 82 nm on polymethyl methacrylate (PMMA) photoresist. This thesis extends previous work by demonstrating nanometer-scale machining of polymers with a focused EUV laser beam. Sub-200 nm wide trenches several micrometers in length were machined on PMMA. These are,to our knowledge, the smallest ablated trenches machined with a focused laser beam. This work also discusses the study of warm plasmas created by EUV laser irradiation of solid targets in which single-photon photoionization is the dominant energy absorption mechanisms. Low-absorption (silicon, Z=14) and high-absorption (chromium, Z=24, and silver, Z=47) targets were heated by ~ 1 ns duration pulses from a 46.9 nm wavelength EUV laser. The spectra obtained agree with 1 1/2 dimension simulations in showing that the Si plasmas are significantly colder and less ionized, confirming that in contrast to plasmas created by optical lasers the plasma properties are largely determined by the absorption coefficient of the target material.Item Open Access Relativistic plasma nano-photonics for ultra-high energy density physics(Colorado State University. Libraries, 2014) Purvis, Michael Anthony, author; Rocca, Jorge J., advisor; Yalin, Azer P., committee member; Menoni, Carmen S., committee member; Marconi, Mario C., committee memberThe trapping of femtosecond laser pulses of relativistic intensity deep within ordered nanowire arrays is shown to volumetrically heat near solid density matter transforming it into ultra-hot highly ionized plasmas. The plasmas were generated by focusing intense ~ 60 femtosecond duration ultra-high-contrast laser pulses onto targets consisting of arrays of densely packed vertically aligned nanowires 35-80 nm diameter. X-ray spectra are presented showing that irradiation of Ni and Au nanowire arrays heats a plasma volume several µm in depth to reach extraordinarily high degrees of ionization (i.e. 26 times ionized Ni , 52 times ionized Au), in the process generating gigabar level pressures. Electron densities nearly 100 times greater than the typical critical density and multi-keV temperatures are achieved using laser pulses of only 0.5 J energy. The large plasma volume and high electron density lead to an increased hydrodynamic-to-radiative lifetime ratio that results in a significant increase in X-ray yield. Measurements from a filtered photodiode array reveal a 100X increase in emission with respect to polished flat targets for photons with energies greater than 9keV. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun.Item Open Access Soft x-ray laser interferometry of dense colliding plasmas and plasma jets(Colorado State University. Libraries, 2010) Grava, Jonathan, author; Rocca, Jorge J., advisor; Menoni, Carmen S., committee member; Marconi, Mario C., committee member; Lundeen, Stephen R., committee memberThis dissertation describes the study of dense plasmas created by laser irradiation of solid targets of various geometries using soft x-ray laser interferometry and hydrodynamic simulations. High contrast interferograms yielded electron density maps describing the evolution of several different plasmas that due to their high density gradients cannot be probed with optical lasers. In a first series of experiments, the evolution of dense aluminum plasmas produced by laser irradiation of 500 µm diameter semi-cylindrical targets was studied. Plasmas created heating the cavity walls with optical laser pulses of ~ 1×1012 W cm-2 peak intensity and 120 ps duration were observed to expand and converge on axis to form a localized high density plasma focus. Electron density maps were obtained using a 46.9 nm wavelength table-top capillary discharge soft x-ray laser probe in combination with an amplitude division interferometer based on diffraction gratings. The measurements showed that the plasma density on axis exceeds 1×1020 cm-3. The electron density profiles were compared with simulations conducted using the hydrodynamic code HYDRA, which showed that the abrupt density increase near the axis is caused by the convergence of plasma generated at the bottom of the groove and the side walls during laser irradiation. At late times in the plasma evolution, extreme ultraviolet radiation is emitted along a narrow arc outside the cavity. Complementary measurements of this lower electron density region were performed using optical interferometry. These measurements combined with two dimensional hydrodynamic simulations show that the emission results from a long lasting collisional shock that arises from the collision of counter-streaming plasmas originating from within the cavity and the surrounding flat walls of the target. The shock is sustained through tens of nanoseconds by the continuous arrival of plasma ablated by radiation emitted by the plasma itself. A second series of experiments was conducted to study collisional aluminum plasma jets created by optical laser irradiation of triangular grooves at an intensity of 1×1012 W cm-2. The dynamics and formation mechanism of dense plasma jets are of interest for basic plasma physics understanding and in some cases astrophysics, and motivate this series of experiments. Series of high-contrast soft x-ray laser interferograms obtained with the 46.9 nm laser mapped the plasma density evolution of an initially narrow plasma jet that expands along the symmetry plane and evolves into a broader plasma plume with significant side lobes. Simulations reveal that the jet formation is initiated by accelerated material ablated from the vertex of the cavity and is augmented by the continual sequential arrival of wall material along the symmetry plane, where it collides and is redirected outward. Radiative cooling is identified as an important process in maintaining the collimation of the jet. The last series of experiments demonstrates that high electron density (ne > 1.5×1021 cm-3) plasma jets can be generated by irradiation of cone targets with a laser pulse of only ~ 1 J energy. Two dimensional electron density maps of jets created by irradiation of conical Cu targets at an intensity of 6×1012 W cm-2 were obtained using soft x-ray laser interferometry. Radiation hydrodynamic simulations agree with experiments in showing that very high jet densities can be obtained with these relatively low laser pulse energies. The simulations revealed that radiation cooling of the plasma plays an important role in the jet evolution and collimation. These results further establish the use of soft x-ray laser interferometry as a powerful diagnostic tool for dense plasmas.Item Open Access Study of a high power capillary discharge(Colorado State University. Libraries, 1999) González, Juan José, author; Rocca, Jorge J., advisor; Wilbur, Paul J., committee memberThe direct generation by electrical discharges of hot and dense plasma columns with large length-to-diameter ratio is of interest for the development of efficient soft x-ray lasers and has resulted in the generation of coherent radiation at wavelength as short as 46.9 nm. This work presents the first experimental results of a new high power density capillary discharge designed to explore the generation of axially uniform plasma columns for the development of discharge pumped lasers at shorter wavelengths. A high power pulsed power generator based on a three-stage pulse compression scheme was developed. The final stage consist of a water dielectric Blumlein transmission line designed to generate current pulses of up to 225 kA with a 10-90 % rise-time of = 10 ns through the capillary load. Argon plasmas generated in polyacetal and ceramic capillaries were studied by means of time resolved soft x-ray pinhole camera images and time resolved XUV spectroscopy. The pinhole images show that the current pulse rapidly compresses the plasma to form a column with a soft x-ray emitting region with a diameter of ≈ 250 μm. Spectra in the 18-23 nm region are observed to be dominated by an ArXV line. The experimental data obtain is in agreement with model computations that suggest these discharge conditions should generate plasma columns of ~ 200-300 μm in diameter with electron temperatures > 250 eV and densities of 1-2x10 20 cm-3.Item Open Access Table-top, full-field, actinic microscope for extreme ultraviolet lithography mask characterization(Colorado State University. Libraries, 2010) Brizuela, Fernando, author; Rocca, Jorge J., advisor; Marconi, Mario C., committee member; Lundeen, Stephen, committee member; Attwood, David T., committee memberThe development of increasingly smaller, faster, and more complex electronic devices that significantly impact everyday life is driven by the ability of printing smaller and smaller components onto semiconductor chips. The number of transistors printed onto an integrated circuit has increased from about one thousand in the 1970 to over a billon in recent years. This exponential growth has been possible thanks to great advances in microlithography processing, and is expected to continue with the implementation of Extreme Ultraviolet Lithography (EUVL) for the printing of the next generation of semiconductor chips. Although EUVL is conceptually similar to conventional lithography in that a mask is projected onto the wafer with a set demagnification, the unique characteristics of extreme ultraviolet light have generated a myriad of technological challenges in the development of this new lithographic technique, including the availability of bright sources, photoresists, reflective optics, and metrology tools at these wavelengths. Of these challenges, the need for microscopes capable of characterizing the printability of absorber patterns on the reflective Mo/Si coated lithographic masks, has risen be to one of the highest priorities for chip manufacturers as they prepare to implement EUVL at high-volume manufacturing. Currently, only a very limited number of EUV microscopes for mask characterization are available. And although these few synchrotron-based microscopes have significantly contributed to the development of EUVL masks, their building-size illumination source make them unsuited for mask characterization in an industrial setting. This dissertation describes the development of the first compact, full-field microscope for at-wavelength characterization of EUVL masks. This microscope combines the output of a table-top 13.2 nm wavelength laser with state-of-the-art diffractive optics to render high quality images of the patterns on EUVL masks with 55 nm spatial resolution and acquisition times of less than 90 seconds. From these images we have demonstrated for the first time measurements of line-edge roughness and normalized intensity line slope of an EUVL mask using a compact microscope. This is significant because with this microscope that emulates the imaging conditions of a 4xdemagnification stepper it is possible to evaluate the mask quality and printability independently of photoresist response. It is foreseeable that these microscopes will not only contribute to the development of EUVL mask technology, but will also play a significant role in the path for the realization of convenient stand-alone metrology systems for on-site evaluation of EUVL masks.Item Open Access Volumetric creation of ultra-high-energy-density plasma by irradiation of ordered nanowire arrays(Colorado State University. Libraries, 2016) Bargsten, Clayton, author; Rocca, Jorge J., advisor; Marconi, Mario C., committee member; Roberts, Jacob L., committee memberCreating appreciable volumes of Ultra-High-Energy Density (UHED) matter in the laboratory is a challenge. Recent developments in the fabrication of vertically aligned nanowire array targets, in coordination with ultra-high-contrast femtosecond laser pulses focused to relativistic intensity, have opened the door to creating UHED matter using compact laser facilities with laser pulses of ~ 0.6 J. These high aspect ratio, vertically aligned nanostructure targets allow the laser energy to penetrate deep into the near-solid density material and heat plasmas to keV temperatures, generating Gbar pressures that are only surpassed in the laboratory by the central hot-spot of highly compressed thermonuclear fusion plasmas. The depth of the heated volume is key in governing the properties of these new UHED plasmas, and is reported here for the first time in vertically aligned nanowire arrays using a buried-tracer technique. In this study, arrays of 55 nm diameter nanowires, manufactured with a variable length segment of nickel on top of a buried cobalt segment, were irradiated with relativistic femtosecond laser pulses of (4±1) x 1019 W cm-2 intensity. Buried Co atoms are observed to ionize to the He-like state for depths greater than 4 μm, in good agreement with particle-in-cell simulations. The measured heat penetration demonstrates that the UHED plasma regime can be accessed with small high repetition rate lasers.