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We present multi-joule-level energy extraction from Tm:YLF. The tabletop, diode-pumped system consists of a Tm:YLF oscillator followed by a 4-pass Tm:YLF amplifier, which produced 3.88J in 20ns pulses and up to 38.1J in long-pulse mode.

We report on the first multi-joule-level Tm:YLF amplifier. In this experimental setup, a Tm:YLF oscillator seeds a 4-pass diode-pumped Tm:YLF amplifier, producing output energies of 3.88J in 20ns and up to 38.1J in long-pulse operation.

We report on the generation of high energy, high power pulses in a tabletop diode-pumped Tm:YLF-based laser system, which delivers amplified pulse energies up to 108 J, as well as GW peak power performance when seeded with nanosecond duration pulses. Furthermore, the high power and efficiency capabilities of operating Tm:YLF in the multi-pulse extraction (MPE) regime were explored by seeding the experimental setup with a multi-kHz burst of pulses exhibiting a low individual pulse fluence, resulting in a 3.6 kW average power train of multi-joule-level pulses with an optical-to-optical efficiency of 19%.

High peak and average power lasers with high wall-plug efficiency, like the Big Aperture Thulium (BAT) laser, have garnered tremendous attention in laser technology. To meet the requirements of the BAT laser, we have developed low-dispersion reflection multilayer dielectric (MLD) gratings suitable for compression of high-energy pulses for operations at 2 micron wavelength. We carried out 10000-on-1 damage tests to investigate the fluence damage thresholds of the designed MLD gratings and mirrors, which were found between 100-230 mJ/cm2. An ultrashort pulsed laser (FWHM = 53 fs, λ = 1.9 μm) operating at 500 Hz was used in the serpentine raster scans. The atomic force microscope images of the damage sites show blister formation of the underlying layers at lower fluences but ablation of the grating pillars at higher fluences. We simulated the dynamic electronic excitation in the MLD optics with a finite-difference in the time domain approach in 2D. The simulation results agree well with the LIDT measurements and the observed blister formation. This model is able to evaluate the absolute LIDT of MLD gratings.

We report the demonstration of a diode-pumped Tm:YLF laser operating at 1.88 µm that produces pulse energies up to 3.88 J in 20 ns. The compact system consists of a Q -switched cavity-dumped oscillator generating 18 mJ pulses, which are then amplified in a four-pass power amplifier. Energies up to 38.1 J were obtained with long-pulse amplifier operation. These results illustrate the high energy storage and extraction capabilities of diode-pumped Tm:YLF, opening the path to high peak and average power mid-infrared solid-state lasers.

High-energy ultrashort pulse optical lasers operating at high repetition rate are required to drive intense compact coherent soft X-ray sources, including soft X-ray lasers, for applications in nanoscience and nanotechnology, material studies, and high field science. This paper reviews two types of high-power solid-state laser systems developed at Colorado State University to pump compact, high repetition rate, and plasma-based soft X-ray lasers. One is a flashlamp-pumped, petawatt-class Ti:sapphire chirped-pulse amplification laser that generates 0.85 PW pulses of 30 fs duration at 3.3 Hz repetition rate. Using a fraction of the output energy from this laser, we have demonstrated gain-saturated, compact, repetitive lasers down to 6.85 nm in Ni-like Gd and have observed gain in shorter wavelength transitions, down to 5.85 nm in Ni-like Dy. The second type of pump laser is an all diode-pumped chirped-pulse amplification system based on cryogenically cooled Yb:YAG active mirror amplifiers that produces 1 J pulses of picosecond duration at 500 Hz repetition rate. These compact diode-pumped laser systems have enabled new advances in high-average-power tabletop soft X-ray lasers that include 100 Hz demonstrations at wavelengths ranging from 10.9 to 18.9 nm, as well long duration operation at these high repetition rates for periods up to one hour. These and other recent results that include the operation of an 18.9 nm laser Ni-like Mo laser at 400 Hz repetition rate open a path to compact kilohertz repetition rate soft X-ray lasers.

We demonstrate optical parametric amplification using a spatially-homogenized pump beam for the first time and investigate the impact of pump beam angular content on OPA efficiency and bandwidth.

We demonstrate the generation of 1.1 J pulses with a duration of 4.5 ps at 1 kHz repetition rate (1.1 kW average power) from a diode-pumped cryo-cooled chirped pulse amplification Yb:YAG laser.

We demonstrate a 1.1 kW average power picosecond laser emitting 1.1 J pulses of 4.5 ps duration at 1 kHz repetition rate from a cryogenically cooled diode-pumped chirped pulse amplification Yb:YAG laser.

European physical journal special topics 229(24), 3675 - 4284 (2020). doi:10.1140/epjst/e2020-000127-8, This report presents the conceptual design of a new European research infrastructure EuPRAXIA. The concept has been established over the last four years in a unique collaboration of 41 laboratories within a Horizon 2020 design study funded by the European Union. EuPRAXIA is the first European project that develops a dedicated particle accelerator research infrastructure based on novel plasma acceleration concepts and laser technology. It focuses on the development of electron accelerators and underlying technologies, their user communities, and the exploitation of existing accelerator infrastructures in Europe. EuPRAXIA has involved, amongst others, the international laser community and industry to build links and bridges with accelerator science — through realising synergies, identifying disruptive ideas, innovating, and fostering knowledge exchange. The Eu-PRAXIA project aims at the construction of an innovative electron accelerator using laser- and electron-beam-driven plasma wakefield acceleration that offers a significant reduction in size and possible savings in cost over current state-of-the-art radiofrequency-based accelerators. The foreseen electron energy range of one to five gigaelectronvolts (GeV) and its performance goals will enable versatile applications in various domains, e.g. as a compact free-electron laser (FEL), compact sources for medical imaging and positron generation, table-top test beams for particle detectors, as well as deeply penetrating X-ray and gamma-ray sources for material testing. EuPRAXIA is designed to be the required stepping stone to possible future plasma-based facilities, such as linear colliders at the high-energy physics (HEP) energy frontier. Consistent with a high-confidence approach, the project includes measures to retire risk by establishing scaled technology demonstrators. This report includes preliminary models for project implementation, cost and schedule that would allow operation of the full Eu-PRAXIA facility within 8—10 years., Published by Springer, Heidelberg

We demonstrate the generation of 1.1 J pulses of picosecond duration at 1 kHz repetition rate (1.1 kW average power) from a diode-pumped chirped pulse amplification Yb:YAG laser. The laser employs cryogenically cooled amplifiers to generate λ = 1030 n m pulses with average power of up to 1.26 kW prior to compression with excellent beam quality. Pulses are compressed to 4.5 ps duration with 90% efficiency. This compact picosecond laser will enable a variety of applications that require high energy ultrashort pulses at kilohertz repetition rates.

Figure 20.1 was not correct in the published article. The original article has been corrected. The published apologizes for the inconvenience.

We report the demonstration of a pulse synthesizer based on spatial beam splitting and pulse stacking for the generation of picosecond laser pulses of Joule-level energy with arbitrary shape. An array of liquid crystals is used to control the amplitude of ten individual sub-pulses, and sliding retroreflectors are used to adjust their temporal separations. The synthesizer was used in combination with a λ=1.03 µm diode-pumped cryogenically-cooled Yb: YAG chirped pulse amplification laser to synthesize 1.3 J pulses or pulse trains of arbitrary shapes up to 9 ns duration with a temporal resolution as short as 8 ps. This pulse synthesizer offers the opportunity to incorporate a self-learning system to search for the optimal laser pulse shapes for various applications including optimized plasma conditions in laser-plasma based soft x-ray lasers and plasma sources for extreme ultraviolet lithography.

Plasma-based soft x-ray lasers (SXRL) enable experiments requiring bright, high energy, soft x-ray laser pulses to be conducted in compact facilities. Recent advances in high energy, high repetition rate, ultrashort pulse solid state lasers now make it possible to extend their wavelenght range, increase their repetition rates, and improve their efficiency. Recently we extended the operation of gain-saturated compact repetitive x-ray lasers down to λ=6.85 nm in Ni-like Gd [1]. Isoelectronic scaling of these collisionally excited laser transitions produced strong lasing at 6.67 nm and 6.11 nm in Ni-like Tb and amplification at 6.41 nm and 5.85 nm in Ni-like Dy [1]. This recent progress will be summarized, and efforts to further extend laser operation to shorter wavelengths will be reviewed. We will also discuss the possibility of increasing the efficiency of plasma-based soft x-ray lasers by controlling the pulse shape of the pump pulses. Prospects of these SXRL will be discussed. Work supported by the US Department of Energy Basic Energy Sciences and by the National Science Foundation [1] A. Rockwood, Y. Wang, S. Wang, M. Berrill, V.N. Shlyaptsev, and J.J. Rocca, "Compact gain-saturated x-ray lasers down to 6.85 nm and amplification down to 5.85 nm". Optica. 5, 257, (2018).

We report on the development and characterization of kW-average-power cryogenically-cooled amplifiers generating Joule-level pulses of picosecond duration at 1 kHz. Analysis of the thermal and multilayer coating damage behavior of a high-energy kilowatt-average-power diode-pumped Yb:YAG active mirror based on measurements and simulations is presented.

Scaling the particle beam luminosity from laser wakefield accelerators to meet the needs of the physics community requires a significant, thousand-fold increase in the average power of the driving lasers. Multipulse extraction is a promising technique capable of scaling high peak power lasers by that thousand-fold increase in average power. However, several of the best candidate materials for use in multipulse extraction amplifiers lase at wavelengths far from the 0.8&ndash, 1.0 &mu, m region which currently dominates laser wakefield research. In particular, we have identified Tm:YLF, which lases near 1.9 &micro, m, as the most promising candidate for high average power multipulse extraction amplifiers. Current schemes to scale the laser, plasma, and electron beam parameters to alternative wavelengths are unnecessarily restrictive in that they stress laser performance gains to keep plasma conditions constant. In this paper, we present a new and more general scheme for wavelength scaling a laser wakefield acceleration (LWFA) design point that provides greater flexibility in trading laser, plasma, and electron beam parameters within a particular design point. Finally, a multipulse extraction 1.9 &micro, m Tm:YLF laser design meeting the EuPRAXIA project&rsquo, s laser goals is discussed.

Novel architectures of Petawatt-class, high peak power laser systems that allow operating at high repetition rates are opening a new arena of commercial applications of secondary sources and discovery science. The natural path to higher average power is the reduction of the total heat load induced and generated in the laser gain medium and eliminating other inefficiencies with the goal to turn more energy into laser photons while maintaining good beam quality. However, the laser architecture must be tailored to the specific application and laser parameters such as wavelength, peak power and intensity, pulse length, and shot rate must be optimized. We have developed a number of different concepts tailored to secondary source generation that minimize inefficiencies and maximize the average power. The Scalable Highaverage- power Advanced Radiographic Capability (SHARC) and the Big Aperture Thulium (BAT) laser are examples of two such high average power laser concepts; SHARC is designed for production of ion beams and x-rays, and exploration of high energy density physics at 1.5 kW average power, and BAT is envisioned for driving laser-based electron accelerators at 300 kW average power.

We report results of a study of the laser induced damage threshold (LIDT) behavior of ion beam sputtered H f O 2 / S i O 2 multilayer coatings on Yb:YAG using 1-on-1 and N-on-1 test protocols. The tests were conducted at ambient, vacuum, and cryogenic conditions using 280 ps pulses at λ = 1030 n m . The 1-on-1 LIDT of antireflection (AR) stacks is found to be only slightly reduced under vacuum and cryogenic conditions, while that of high reflectivity (HR) stacks is insensitive to environmental conditions within the uncertainty of the measurements. Cryogenic N-on-1 tests show the LIDT of the HR coating is almost the same as in the 1-on-1 tests. Conversely, the cryogenic N-on-1 test of the AR coating shows damage at ∼ 13 J / c m 2 , a fluence lower than the 20.4 J / c m 2 of 1-on-1 tests. The AR damage behavior is found to be affected by imperfections at the Yb:YAG surface. These findings show that high surface quality is required to increase energy extraction from active mirror laser amplifiers.

Canine hypoadrenocorticism (CHA) is a life-threatening condition that affects approximately 3 of 1,000 dogs. It has a wide array of clinical signs and is known to mimic other disease processes, including kidney and gastrointestinal diseases, creating a diagnostic challenge. Because CHA can be fatal if not appropriately treated, there is risk to the patient if the condition is not diagnosed. However, the prognosis is excellent with appropriate therapy. A major hurdle to diagnosing CHA is the lack of awareness and low index of suspicion. Once suspected, the application and interpretation of conclusive diagnostic tests is relatively straight forward. In this study, machine learning methods were employed to aid in the diagnosis of CHA using routinely collected screening diagnostics (complete blood count and serum chemistry panel). These data were collected for 908 control dogs (suspected to have CHA, but disease ruled out) and 133 dogs with confirmed CHA. A boosted tree algorithm (AdaBoost) was trained with 80% of the collected data, and 20% was then utilized as test data to assess performance. Algorithm learning was demonstrated as the training set was increased from 0 to 600 dogs. The developed algorithm model has a sensitivity of 96.3% (95% CI, 81.7%–99.8%), specificity of 97.2% (95% CI, 93.7%–98.8%), and an area under the receiver operator characteristic curve of 0.994 (95% CI, 0.984–0.999), and it outperforms other screening methods including logistic regression analysis. An easy-to-use graphical interface allows the practitioner to easily implement this technology to screen for CHA leading to improved outcomes for patients and owners.

The demonstration of a Yb:YAG chirped pulse amplification laser producing 1 J, 5 ps pulses at 500 Hz repetition rate [1] and recently 1 J pulses at 1 kHz repetition rate [2] relied on efficient thermal management and high performance multilayer dielectric coatings on the laser amplifier active mirrors. In the active mirror configuration, the Yb:YAG amplifier crystals use HfO2/SiO2 multilayer dielectric anti-reflection (AR) and high reflection (HR) coatings. The Joule-level amplifier is operated in vacuum and at liquid nitrogen boiling temperature (77 K) with 1030 nm, 220 ps duration laser pulses making four reflections from each HR coating and 8 passes through each AR coating. The LIDT performance of these coatings is crucial to the future scaling of these amplifiers. In this work we describe results of an investigation of the laser induced damage threshold (LIDT) of Yb:YAG active mirror laser amplifier disks at atmospheric, vacuum and cryogenic temperature conditions. The measurements were conducted for 220 ps pulses, the typical pulse duration of stretched pulses we are using to implement kW-class average power CPA laser amplifiers [1,2]. We measured the 1-on-1 (single-shot) and 3000-on-1 LIDT on Yb:YAG crystals with and without the coatings. The results show that the LIDT for single shot damage occurs near 20 J/cm2, and 100% damage probability occurs near 29 J/cm2 for either the uncoated or coated Yb:YAG crystal at atmospheric conditions. Similar results were obtained in the vacuum and cryogenic temperatures tests. This leads to the conclusion that the Yb:YAG material itself, and not the coatings, is the limiting factor in the LIDT. This work was performed under the auspices of the U.S. Department of Energy, Office of High Energy Physics, Accelerator Stewardship Program under Award DE-SC0016136. References [1] C. Baumgarten, M. Pedicone, H. Bravo, H. Wang, L. Yin, C. S. Menoni, J. J. Rocca, and B. A. Reagan, Optics Letters 41, 3339 (2016). [2] Brendan A Reagan, Cory Baumgarten, Elzbieta Jankowska, Han Chi, Herman Bravo, Kristian Dehne, Michael Pedicone, Liang Yin, Hanchen Wang, Carmen S Menoni, Jorge J Rocca, High Power Laser Science and Engineering 6, e11 (2018).

We report a chirped pulse amplification laser designed to produce Joule-level pulses of picosecond duration at 1 kHz repetition rate. This laser is based on cryogenically-cooled Yb:YAG active mirror amplifiers. A technique for mapping the temperature distribution within the active mirrors in 3D is discussed.

Soft X-ray lasers (SXRLs) produce the highest energy pulses of coherent ultrashort wavelength radiation. Their large number of photons per pulse allow us to perform single-shot imaging of nanoscale objects, to develop material composition sensitive nanoprobes, and to conduct interferometric diagnostics of bright dense plasmas. However, until recently, with the exception of capillary discharge lasers at 46.9 nm, their average power was limited by the low repetition rate of the high energy optical pump lasers required to drive them and by the relatively low pumping efficiency. To overcome this limitation, we have developed a diode-pumped, picosecond Yb:YAG CPA laser driver that allowed us to demonstrate the first table-top SXRL capable of 100 Hz repetition rate gain saturated operation. These new pump lasers combined with efficient plasma heating techniques enable the operation of SXRLs at four orders of magnitude higher repetition rate than the first plasma-based collisional SXRLs (Fig. 2.1). Laser operation at 100 Hz repetition rate generated an average power of 0.2 mW at 18.9 nm (Ni-like Mo) and 0.1 mW at λ = 13.9 nm (Ni-like Ag). We have recently improved upon this diode-pumped laser technology, demonstrating a record 0.5 kHz repetition rate, 1 J, picosecond laser with good beam quality and high stability. We will discuss the results of the first demonstration of a compact table-top soft X-ray laser at repetition rates up to 400 Hz using this new pump laser.

Recent results in the development of diode-driven high energy, high repetition rate, picosecond lasers, including the demonstration of a cryogenic Yb:YAG active mirror amplifier that produces 1.5 J pulses at 500 Hz repetition rate (0.75 kW average power) are reviewed. These pulses are compressed resulting in the generation of ${\sim}5~\text{ps}$ duration, 1 J pulses with 0.5 kW average power. A full characterization of this high power cryogenic amplifier, including at-wavelength interferometry of the active region under ${>}1~\text{kW}$ average power pump conditions, is presented. An initial demonstration of operation at 1 kW average power (1 J, 1 kHz) is reported.

We will review recent progress in the development of high repetition, high average power rate soft x-ray lasers at 10-20 nm wavelength at Colorado State University, and the compact diode- pumped solid state lasers that drive them. The latter includes the development of a 1 J picosecond laser capable of operating at 500 Hz repetition rate. Results that demonstrate soft x-ray laser operation at the highest repetition rate reported to date: 400 Hz, and prospects of the use of these lasers in applications are discussed.

We present an analysis of the thermal behavior of a high-energy kilowatt-average-power diode-pumped cryogenically cooled Yb:YAG active mirror laser amplifier based on measurements and simulations. Maps of the temperature distribution of the laser material at pump powers up to 1 kW were obtained for the first time by spatially and spectrally resolving the fluorescence induced by a scanning probe beam. The wavefront distortion resulting from the front surface deformation and the overall deformation of the gain medium assembly were measured using a Mach–Zehnder interferometer. The measured deformations agree well with the results of thermomechanical modeling using finite element method simulations, and with the results of focal length shift measurements. The relative contributions to the optical path difference (OPD) of the mechanical deformations, refractive index changes, and electronic contribution are discussed. We show that the Cr4+:YAG cladding plays a significant role in both the temperature distribution and the overall OPD changes. The pump-induced mechanical deformations of the assembly dominate the OPD changes in this kilowatt-average-pump-power cryogenically cooled Yb:YAG active mirror laser.

We report the demonstration of a chirped pulse amplification laser system that produces 1.5 J pulses at 0.5 kHz repetition rate and 0.75 kW average power. These pulses are subsequently compressed resulting 1 J, ~5 ps duration pulses at 500 Hz repetition rate. The 8-pass main amplifier consists of two diode-pumped, cryogenic-temperature Yb:YAG active mirrors cooled by a thermally efficient, high capacity cryogenic-cooling system. This amplifier operates with an opticalto- optical efficiency of 37%. The amplified pulses have excellent beam quality with a measured M2 factor of ~ 1.3. Over 30 minutes of continuous operation, we measured a shot-to-shot pulse energy fluctuation of only 0.75% RMS over the nearly 1 million shots fired. This laser was employed to make the first demonstration of a compact, plasma-based EUV/soft x-ray laser operating at a repletion rate of 400 Hz. In this proof-of-principle demonstration, shaped 1 J pulses of picosecond duration were focused onto a rotating molybdenum target at grazing incidence. The resulting plasma is collisionally ionized to the Ni-like ionic stage where a large, transient population inversion results in production of bright λ = 18.9 nm laser pulses.

Tasub2/subOsub5/sub/SiOsub2/subhigh reflection (HR) interference coatings for λ∼1 μm offer superior performance at high irradiance conditions. However, these coatings are not good candidates for high peak power conditions in comparison to HfOsub2/sub/SiOsub2/submultilayer stacks. Here we show that the modification of the top layers design of a quarter wave Tasub2/subOsub5/sub/SiOsub2/subhigh reflector leads to 4-5 fold increase in the laser damage fluence compared to a quarter wave (Tasub2/subOsub5/sub/SiOsub2/sub)sup15/supwhen tested at λ=1.03 μm using pulse durations of 0.19 and 4 ns and peak power densities of 43.5 and 216 GW/cmsup2/sup. One of the designs achieved a laser damage threshold fluence of 174 J/cmsup2/supat 4 ns, which is 10% higher than that of a HfOsub2/sub/SiOsub2/subquarter wave design.

Results of a study of laser induced damage of ion beam sputtered single layers and capped single layers of Sc2O3, HfO2 and Ta2O5 in a controlled atmosphere and in an ultra-high vacuum (UHV) show the choice of material is paramount to achieving the best performance.

The recent development of a diode-pumped, kilowatt-class average power, high energy picosecond laser is discussed. Its use in pumping high repetition rate soft x-ray lasers and prospects for scaling will be discussed.

Lawrence Livermore National Laboratory (LLNL) and Colorado State University (CSU) have co-developed a planarization process to smooth nodular defects. This process consists of individually depositing then etching tens of nanometers of SiO2 with a ratio of 2:1, respectively. Previous work shows incorporating the angular dependent ion surface etching and unidirectional deposition reduces substrate defect cross-sectional area by 90%. This work investigates the micro-structural and optical modifications of planarized SiO2 films deposited by ion beam sputtering (IBS). It is shown the planarized SiO2 thin films have ~3x increase in absorption and ~18% reduction in thin film stress as compared to control (as deposited) SiO2. Planarized SiO2 films exhibit ~13% increase in RMS surface roughness with respect to the control and super polished fused silica substrates. Laser-induced damage threshold (LIDT) results indicate the planarization process has no effect on the onset fluence but alters the shape of the probability vs fluence trace.

High reflection and anti-reflection interference coatings based on amorphous oxides for high energy lasers operating at wavelengths in the 1–2μm with superior performance to laser damage are demonstrated.

Our recent progress in the development of high energy, picosecond lasers with high average power will be presented, including the demonstration of a cryogenic Yb:YAG laser that produces 1 Joule, 5 picosecond pulses at 0.5 kHz repetition rate.

As we follow Moore's Law and pack more and more components onto each computer chip, we must extend the limits of manufacturing. Looking ahead, efficient sources of light at a wavelength around 6.7 nm are needed for beyond-extreme-ultraviolet (BEUV) lithography, to create integrated circuits beyond the 7-nm logic node. This study measures and models plasmas of Gd and Tb, prepared using a single laser tuned over a broad range of parameters. These plasmas do emit at the desired wavelength, and calculations indicate that a conversion efficiency of 6% could ultimately be realized.

We report the demonstration of a diode-pumped chirped pulse amplification Yb:YAG laser that produces λ=1.03 μm pulses of up to 1.5 J energy compressible to sub-5 ps duration at a repetition rate of 500 Hz (750 W average power). Amplification to high energy takes place in cryogenically cooled Yb:YAG active mirrors designed for kilowatt average power laser operation. This compact laser system will enable new advances in high-average-power ultrashort-pulse lasers and high-repetition-rate tabletop soft x-ray lasers. As a first application, the laser was used to pump a 400 Hz λ=18.9 nm laser.

Plasmas emitting near λ=6.7nm are of interest for beyond EUV lithography (BEUVL). We have conducted a comprehensive study of the spectral characteristics, conversion efficiency, and source size of Gd and Tb laser-produced plasmas over a broad range of laser pulsewidths (120ps-4ns) and irradiation intensities (1.4×10 11 -6.1×10 13 W/cm 2 ). The data over the entire parameter range was acquired using a single diode-pumped Yb: YAG laser. The angular distribution of the BEUV emission was measured using an array of calibrated energy-monitors, allowing for an accurate estimate of the BEUV yield. A similar conversion efficiency of 0.47% into a 0.6% bandwidth in 2π solid angle was measured for both Gd and Tb plasma.

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.

A 38-year-old man presents to his primary care physician for follow-up and review of the results of a 24-hour ambulatory monitor that was placed after an emergency department evaluation for palpitations and chest pain 2 days earlier. He had been hospitalized 2 months earlier for severe headaches and elevated blood pressure. A workup for secondary causes of hypertension was negative, and he was started on bisoprolol and hydrochlorothiazide. He subsequently began experiencing intermittent episodes of lightheadedness and presyncope. Three days before seeing his primary care physician, he developed palpitations and central chest pressure radiating to his back associated with dyspnea at rest. When his wife, a registered nurse, checked his pulse and blood pressure, his heart rate was 140 to 160 beats per minute and regular. It slowed with a coached Valsalva maneuver. His wife noted his blood pressure was 140/70 mm Hg. He was taken to a local emergency department where, on arrival, his symptoms resolved and his vital signs normalized. The evaluation in the emergency department included electrolytes, a troponin, and a chest film that were all reportedly normal. He was discharged wearing a 24-hour ambulatory monitor with instructions to follow up with his primary care physician. He reported no syncopal episodes and denied orthopnea, paroxysmal nocturnal dyspnea, or lower-extremity edema. His past medical history includes hypertension and degenerative joint disease. His only medications are the bisoprolol, hydrochlorothiazide, and an occasional nonsteroidal anti-inflammatory drug for back pain. He has no allergies, but he had had an intolerable cough when taking an angiotensin-converting enzyme inhibitor for his hypertension in the past. He has no history of tobacco or illicit drug use. He occasionally drinks alcohol and 1 caffeinated beverage daily. He is married with 2 young daughters and is employed as a mechanical engineer. He recalls that a paternal …

An estimated 16 million people in the United States have coronary artery disease (CAD), and approximately 325,000 people die annually from cardiac arrest. About two-thirds of unexpected cardiac deaths occur without prior recognition of cardiac disease. A vast majority of these deaths are attributable to the rupture of 'vulnerable atherosclerotic plaques'. Clinically, plaque vulnerability is typically assessed through imaging techniques, and ruptured plaques leading to acute myocardial infarction are treated through angioplasty or stenting. Despite significant advances, it is clear that current imaging methods are insufficiently capable for elucidating plaque composition--which is a key determinant of vulnerability. Further, the exciting improvement in the treatment of CAD afforded by stenting procedures has been buffered by significant undesirable host-implant effects, including restenosis and late thrombosis. Nanotechnology has led to some potential solutions to these problems by yielding constructs that interface with plaque cellular components at an unprecedented size scale. By leveraging the innate ability of macrophages to phagocytose nanoparticles, contrast agents can now be targeted to plaque inflammatory activity. Improvements in nano-patterning procedures have now led to increased ability to regenerate tissue isotropy directly on stents, enabling gradual regeneration of normal, physiologic vascular structures. Advancements in immunoassay technologies promise lower costs for biomarker measurements, and in the near future, may enable the addition of routine blood testing to the clinician's toolbox--decreasing the costs of atherosclerosis-related medical care. These are merely three examples among many stories of how nanotechnology continues to promise advances in the diagnosis and treatment of vulnerable atherosclerotic plaques.

A diode-pumped CPA laser based on cryogenically-cooled Yb:YAG amplifiers that produces 1 Joule pulses at repetition rates up to 500Hz with good beam quality was demonstrated and used to pump a table-top soft x-ray laser.

High reflection Ta2O5/SiO2 and HfO2/SiO2 interference coatings that incorporate top thick layers of SiO2 with superior performance are demonstrated for 1-2μm high energy lasers are demonstrated.

We discuss new results of the demonstration of 100 Hz table-top soft x-ray lasers operating at wavelengths from 10.9 nm to 18.9 nm and report the highest soft x-ray laser average power to date at sub-20 nm wavelength. The results include the generation of average powers up to 0.2 mW at λ = 18.9 nm, 0.1 mW at λ = 13.9 nm, and 20 μW at λ = 11.9 nm. These lasers are driven by a compact chirped pulse amplification laser system featuring diode-pumped, cryogenically-cooled Yb:YAG power amplifiers that produces 1 J pulses of 5 ps FWHM duration at 100 Hz repetition rate. The driver laser pulse shape was tailored to more efficiently pump soft x-ray plasma amplifiers operating at sub-15 nm wavelengths leading to a threefold increase in the λ = 13.9 nm laser pulse energy and lasing down to 10.9 nm. The pump pulse profile consisting of a nanosecond ramp followed by two closely spaced peaks of picosecond duration, is shown to create a plasma with an increased density of Ni-like lasing ions at the time of peak temperature, resulting in a larger gain coefficient over a temporally and spatially enlarged space. The development of rotating solid targets with high shot capacity has allowed the uninterrupted operation of the λ = 18.9 nm soft x-ray laser for hundreds of thousands of consecutive shots making it suitable for applications in nanoscience and nanotechnology that require high photon flux at short wavelengths. As a proof-of-principle demonstration of the utility of this laser in such applications we have lithographically printed an array of nanometer-scale features through coherent Talbot self imaging. These results open the path to milliwatt average power table-top soft x-ray lasers.

Respiratory and pharmacologic interventions are used during auscultation of heart sounds. These same principles may be utilized in the echocardiography laboratory to aid diagnosis. Four physical maneuvers and one pharmacologic intervention performed in the echocardiography laboratory are described. A brief discussion of applications in specific clinical situations is then presented. The Valsalva maneuver involves having the patient inspire deeply followed by a forceful exhalation against a closed glottis for approximately 10 seconds. Placing the hand on the patient’s abdomen by the examiner provides a force for the patient to strain against and ensures that the abdominal muscles are tightening.1 Some patients who have difficulty with this may find it best to insert their index finger in the mouth and attempt to blow out with lips sealed. Alternatively, the patient may blow into a manometer to maintain 40 mmHg or more.2 The Valsalva maneuver involves the following four phases

Heat generation is a key obstacle to scaling high energy solid-state lasers to the multi-kilowatt average powers required for several key applications. We demonstrate an accurate, in situ, noninvasive optical technique to that makes three-dimensional (3-D) temperature maps within cryogenic amplifiers operating at high average power. The temperature is determined by analyzing the fluorescence spectra with a neural network function. The accuracy of the technique relies on a calibration that does not depend on simulations. Results are presented for a cryogenic Yb:YAG active mirror laser amplifier operating at different pump conditions. The technique is applicable to other solid-state lasers materials.

We show the threshold fluence for damage of Ta2O5/SiO2 multilayer interference coatings measured using 0.19 ns and 4 ns pulses with λ=1.03 µm can be increased by 2x when modifying the coating’s top layer design.