Demonstration of a 1 TW peak power, joule-level ultrashort Tm:YLF laser.

We report on the demonstration of a diode-pumped, Tm:YLF-based, chirped pulse amplification laser system operating at λ ≈ 1.9 µm that produces amplified pulse energies exceeding 1.5 J using a single 8-pass power amplifier. The amplified pulses are subsequently compressed to sub-300 fs durations by a diffraction grating pair, producing record >1 TW peak power pulses. To the best of our knowledge, this is the highest peak power demonstrated for any solid-state, near-2 µm laser architecture and illustrates the potential of Tm:YLF for the next generation of high-power, diode-pumped ultrashort lasers.

Office-Based Multilevel Radiofrequency Ablation for Mild-to-Moderate Obstructive Sleep Apnea.

Objective: Investigate multilevel radiofrequency ablation (RFA) as an alternative therapy for patients with mild-to-moderate obstructive sleep apnea (OSA). Study Design: Prospective, open-label, single-arm, nonrandomized clinical trial. Setting: Multicenter academic and private clinics. Methods: Patients with mild-to-moderate OSA (apnea-hypopnea index [AHI] 10-30; body mass index ≤ 32) were treated with 3 sessions of office-based RFA to the soft palate and tongue base. The primary outcome was a change in the AHI and oxygen desaturation index (ODI 4%). Secondary outcomes included subjective sleepiness level; snoring level; and sleep-related quality of life. Results: Fifty-six patients were enrolled, with 43 (77%) completing the study protocol. Following 3 sessions of office-based RFA to the palate and base of the tongue, the mean AHI decreased from 19.7 to 9.9 (p = .001), while the mean ODI (4%) decreased from 12.8 to 8.4 (p = .005). Mean Epworth Sleepiness Scale scores declined from 11.2 (±5.4) to 6.0 (±3.5) (p = .001), while Functional Outcomes of Sleep Questionnaire scores improved from a mean of 14.9 at baseline to 17.4 (p = .001). The mean visual analog scale snoring scale was reduced from 5.3 (±1.4) at baseline to 3.4 (±1.6) at 6 months posttherapy (p = .001). Conclusion: Office-based, multilevel RFA of the soft palate and base of the tongue is a safe and effective treatment option with minimal morbidity for properly selected patients with mild-to-moderate OSA who are intolerant or refuse continuous positive airway pressure therapy.

Trapezius fasciocutaneous flap for burn reconstruction.

This case involves a 30-year-old female who suffered extensive facial burns as an outcome of a horrific assault. The patient subsequently underwent 2 surgeries with the ultimate goal of reducing the cosmetic, physical, and thus mental burden the assault caused. The technique of choice was the novel trapezius fasciocutaneous flap for burn reconstruction of the neck. It is discussed that while this technique is still deemed a novel procedure, its unique characteristics make it an excellent choice for cases similar to this one. While this approach has not been widely popularized in the treatment of patients with burn contracture requiring reconstruction, the donor site characteristics and ideal functionality make the trapezius fasciocutaneous flap such an excellent choice. This particular type of graft yields a hidden donor site, contains rich vascularity with physical qualities similar to those of facial skin, specifically in regard to thickness, color, and texture, and ultimately produces the most ideal cometic outcome. Further, the wide arc of rotation unique to this flap allows for better manipulation and mobility at the transplanted location. While the anatomic implications are very relevant to head and neck surgery, this method also produces exemplary cosmetic outcomes when compared to other graft procedures.

Femtosecond damage experiments and modeling of broadband mid-infrared dielectric diffraction gratings.

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.

A Case of Melkersson-Rosenthal Syndrome Treated With 5-FU.

The rarity of Melkersson-Rosenthal syndrome, or orofacial granulomatosis, can present with persistent midface bogginess. The management for previous reported cases has included corticosteroid injections, antihistamines, and antibiotics. In the current reported case, the patient was treated with 5-fluorouracil and has been responding positively. Additionally, the patient has not shown signs of steroid atrophy.

Spatio-temporal focal spot characterization and modeling of the NIF ARC kilojoule picosecond laser.

The advanced radiographic capability (ARC) laser system, part of the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, is a short-pulse laser capability integrated into the NIF. The ARC is designed to provide adjustable pulse lengths of ∼1-38ps in four independent beamlets, each with energies up to 1 kJ (depending on pulse duration). A detailed model of the ARC lasers has been developed that predicts the time- and space-resolved focal spots on target for each shot. Measurements made to characterize static and dynamic wavefront characteristics of the ARC are important inputs to the code. Modeling has been validated with measurements of the time-integrated focal spot at the target chamber center (TCC) at low power, and the space-integrated pulse duration at high power, using currently available diagnostics. These simulations indicate that each of the four ARC beamlets achieves a peak intensity on target of up to a few 1018W/cm2.

Injection laser system for Advanced Radiographic Capability using chirped pulse amplification on the National Ignition Facility.

We report on the design, performance, and qualification of the injection laser system designed to deliver joule-level chirped pulse beamlets arranged in dual rectangular beam formats into two main laser amplifier beamlines of the National Ignition Facility. The system is designed to meet the requirements of the Advanced Radiographic Capability upgrade with features that deliver performance, adjustability, and long-term reliability.

Active cooling of pulse compression diffraction gratings for high energy, high average power ultrafast lasers.

Laser energy absorption and subsequent heat removal from diffraction gratings in chirped pulse compressors poses a significant challenge in high repetition rate, high peak power laser development. In order to understand the average power limitations, we have modeled the time-resolved thermo-mechanical properties of current and advanced diffraction gratings. We have also developed and demonstrated a technique of actively cooling Petawatt scale, gold compressor gratings to operate at 600W of average power - a 15x increase over the highest average power petawatt laser currently in operation. Combining this technique with low absorption multilayer dielectric gratings developed in our group would enable pulse compressors for petawatt peak power lasers operating at average powers well above 40kW.

Picosecond laser damage performance assessment of multilayer dielectric gratings in vacuum.

Precise assessment of the high fluence performance of pulse compressor gratings is necessary to determine the safe operational limits of short-pulse high energy lasers. We have measured the picosecond laser damage behavior of multilayer dielectric (MLD) diffraction gratings used in the compression of chirped pulses on the Advanced Radiographic Capability (ARC) kilojoule petawatt laser system at the Lawrence Livermore National Laboratory (LLNL). We present optical damage density measurements of MLD gratings using the raster scan method in order to estimate operational performance. We also report results of R-on-1 tests performed with varying pulse duration (1-30 ps) in air, and clean vacuum. Measurements were also performed in vacuum with controlled exposure to organic contamination to simulate the grating use environment. Results show sparse defects with lower damage resistance which were not detected by small-area damage test methods.

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.

Acoustic phonetics in a clinical setting: a case study of /r/-distortion therapy with surgical intervention.

Acoustic measures are used to document the speech of a 6-year-old child with persistent /r/-distortion through several treatment interventions. The child originally presented a complex of speech disorders and was treated by a speech-language pathologist using phonological process techniques. The procedures successfully corrected most of his speech problems, although /r/ remained severely distorted. The primary acoustic manifestation of this distortion was a high third formant. Surgical correction of a banded lingual frenulum, along with adenoton-sillectomy indicated for sleep apnea, is shown to have had a small effect in lowering the third formant. A dramatic change was seen on reintroduction of therapy, when an extreme drop in third formant frequencies for /r/ was observed. The acoustic data are interpreted using speaker-internal controls derived from a dialect-appropriate adult model.