42 W femtosecond Yb:Lu2O3 regenerative amplifier.

We report on a femtosecond high-power regenerative amplifier based on Yb:Lu2O3. Exploiting the excellent thermo-mechanical properties of this material, we were able to achieve up to 64.5 W in continuous-wave regime, limited only by the available pump power. In pulsed operation, 42 W of average output power at a repetition rate of 500 kHz with 780 fs long pulses could be demonstrated, resulting in a pulse peak power of ∼100 MW. The spectrum was centered at 1034 nm with an FWHM of 2.4 nm, potentially allowing for even shorter pulses. At the maximum output power the beam was nearly TEM00, with an M2 value of 1.2 in both axes.

Single-grating-mirror intracavity stretcher design for chirped pulse regenerative amplification.

We report for the first time, to the best of our knowledge, an innovative design concept for intracavity pulse stretching in a regenerative amplifier, employing a single "grating-mirror" based on a leaky-mode grating-waveguide design. The very compact and flexible layout allows for femtosecond pulses to be in principle easily stretched up to nanosecond durations. The design has been tested in a diode-pumped Yb:CALGO regenerative amplifier followed by a standard transmission grating compressor. Sub-200-fs pulses (stretched pulses ≈110 ps) with 205-µJ energy at 20-kHz repetition rate have been demonstrated. In order to prove the robustness and potential for energy scaling of leaky-mode grating-waveguide intracavity stretcher, we generated stretched pulses with energies of up to ≈700 µJ (400-ps long) at a lower repetition rate of 10 kHz. A simple model is proposed for the study of the cavity in presence of induced spatial chirp.

High pulse energy multiwatt Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers.

We investigated and compared Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers at repetition rates 5-10 kHz, a frequency range interesting for industrial applications requiring relatively high pulse energy. Both materials allow for pulse energies close to 1 mJ with sub-400-fs pulses. The two laser materials offer comparable performance in the pump power range investigated. The same regenerative amplifiers can be run up to 500 kHz for much faster material processing, with maximum output power of up to 9.4 W.

Preliminary observations on tear film interferometry performed in horses.

This retrospective study evaluated tear film (TF) interferometry on horses examined in Northern Italy in 2019-2021. The objectives were to evaluate horses affected by keratitis, and to describe TF values in horses with no evidence of ocular disease. All horses received a complete ophthalmic examination and were examined with the Ocular Surface Analyser, Veterinary-setting, prior to eye manipulation, staining and sample collection. Eighteen horses with no evidence of ocular disease were included in the comparison group. Additionally, 46 horses displaying signs of keratitis (neovascularization, corneal opacities, ulceration, epithelial and subepithelial infiltrates) were evaluated. These horses were divided into presumed non-infectious and infectious or presumed infectious keratitis groups (one with proven bacterial origin, and the others with diagnosed or presumptive keratomycosis) with the former including immune-mediated keratitis. From the observations of TF interferometry in the comparison population the authors concluded that for non-invasive break-up time (NIBUT), the estimated preliminary reference interval was 10.4-31.2s, and for tear meniscus height (TMH), it was 0.215-0.457mm. Moreover, within the keratitis population, from an interferometric point of view punctate lesions of the ocular surface were present in all cases of active diagnosed or presumptive subepithelial keratomycosis but not in any of the non-infectious cases, either non-ulcerative or ulcerative. Limitations of the study include a relatively low number of horses examined and the fact that the diagnosis of infectious keratitis was presumptive and based on clinical improvement after treatment in some cases. To the authors' knowledge, this is the first report of TF interferometry performed in horses.

28-W, 217 fs solid-state Yb:CAlGdO4 regenerative amplifiers.

A new high-performance Yb:CaAlGdO(4) (Yb:CALGO) regenerative amplifier is demonstrated. Pumped by 116 W at ≈980 nm and seeded by means of a 92 fs oscillator, it generates as much as 36 W of average output power with chirped pulses, and 28 W with 217 fs compressed pulses at 500 kHz repetition rate. This corresponds to 56 µJ of pulse energy and 258 MW peak power. The compressed pulses have a time-bandwidth product of 0.69 and could be shortened further with an improved compressor setup.

Spatio-temporal characterization of few-cycle pulses obtained by filamentation.

Intense sub-5-fs pulses were generated by filamentation in a noble gas and subsequent chirped-mirror pulse compression. The transversal spatial dependence of the temporal pulse profile was investigated by spatial selection of parts of the output beam. Selecting the central core of the beam is required for obtaining the shortest possible pulses. Higher energy efficiency is only obtained at the expense of pulse contrast since towards the outer parts of the beam the energy is spread into satellite structures leading to a double-pulse profile on the very off-axis part of the beam. Depending on the requirements for a particular application, a trade-off between the pulse duration and the pulse energy has to be done. The energy of the sub-5-fs pulses produced was sufficient for the generation of high order harmonics in Argon. In addition, full simulation is performed in space and time on pulse propagation through filamentation that explains the double-pulse structure observed as part of a conical emission enhanced by the plasma defocusing.

Generation of intense few-cycle laser pulses through filamentation - parameter dependence.

Intense few-cycle laser pulses as short as 5.1 fs are generated though self-filamentation in a noble gas atmosphere. We study the dependence of the laser pulse fidelity on the driving pulse profile and chirp as well as on the gas parameters, quantify their pointing stability and spatial quality.

Evaluation of intraocular pressure in conscious ferrets (Mustela putorius furo) by means of rebound tonometry and comparison with applanation tonometry.

To determine normal intraocular pressure (IOP) values by means of rebound tonometry in unanaesthetised ferrets, and to compare rebound and applanation tonometry, 55 clinically healthy ferrets were included in an observational, prospective, blinded study. On 52 ferrets, IOP was measured by means of rebound and applanation tonometry. On 3 ferrets, rebound tonometry was performed every two hours over a 24-hour period. Mean IOPs of the 104 eyes obtained with the rebound tonometer were 14.07±0.35 (95% CI 13.37 to 14.77) tonometer-units (TU). The IOP was significantly higher in males than in females, controlling for age and weight. A study-ordered decrease in coefficient of variation (CV) was observed (measurement 1-52=21.2±1.4 per cent v measurement 53-104=14.4±1.1 per cent) and high CVs (>30 per cent) were significantly less frequent in measurement 53-104. A significant difference in IOP during the 24- hour measurements was found, with the lowest IOP recorded at 22:00. The tonometers presented poor agreement, and IOP values were not correlated. The difference in IOP estimation increased with the magnitude of the measurements. Applanation tonometry presented a significant higher frequency of per-eye IOP values exceeding 25 and 30 TU, and a significant lower repeatability (CV=37.1±2.6 per cent v 17.8±1.2 per cent) compared with rebound tonometry. In conclusion, several factors need to be considered when measuring IOP in ferrets.

Spectral signature of short attosecond pulse trains.

We report experimental measurements of high-order harmonic spectra generated in Ar using a carrier-envelope-offset (CEO) stabilized 12 fs, 800 nm laser field and a fraction (less than 10%) of its second harmonic. Additional spectral peaks are observed between the harmonic peaks, which are due to interferences between multiple pulses in the train. The position of these peaks varies with the CEO and their number is directly related to the number of pulses in the train. An analytical model, as well as numerical simulations, support our interpretation.

Quantum path interferences in high-order harmonic generation.

We have investigated the intensity dependence of high-order harmonic generation in argon when the two shortest quantum paths contribute to the harmonic emission. For the first time to our knowledge, experimental conditions were found to clearly observe interference between these two quantum paths that are in excellent agreement with theoretical predictions. This result is a first step towards the direct experimental characterization of the full single-atom dipole moment and demonstrates an unprecedented accuracy of quantum path control on an attosecond time scale.

Suspected latent vertebral metastasis of uveal melanoma in a dog: a case report.

A six-year-old intact male Pomeranian was examined because of right eye discomfort. An iris neoplasm was suspected and the eye was enucleated. A uveal melanoma with malignant features was diagnosed. The dog recovered uneventfully from surgery. A general physical examination was performed at 3-month intervals afterwards without any detectable problem, but 18 months after the first presentation the dog suffered a rapid, progressive paraplegia. Radiographic examination and myelography revealed a spinal cord compression at the level of the 8th thoracic (T8) vertebral body. Surgical exploration of the area revealed a potential vertebral neoplasm: histopathology confirmed a melanoma which was suspected to have resulted from metastasis from the previously diagnosed uveal melanoma.

[Ultrasonographic semiology of biliary prostheses]. / Semeiotica ecografica delle protesi biliari.

US was used to study 60 patients with different types of plastic (Home-made, Lunderquist, Miller, Carey-Coons, Lammer) and metallic (Z-stent, Wallstent) biliary stents, from October 1990 to March 1993. The optimal US approach was assessed, together with several US features which are typical of each type of endoprosthesis. As far as plastic endoprostheses are concerned, independent of manufacturing differences, the typical US pattern on longitudinal scans is a hyperechoic double line while, on transverse scans, the prosthesis cylinder is represented by short hyperechoic lines, resembling the mathematic equal sign. According to the different types, metallic stents appear as thin hyperechoic lines or narrow gratings on longitudinal scans and as hyperechoic spots following a circular pattern or as a hyperechoic ring on transverse scans.