RESUMO
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 â¼100 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.
RESUMO
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.
RESUMO
AIMS: The aim of this study was to report four cases of pleomorphic adenoma which were characterized by intra-vascular tumour. METHODS AND RESULTS: The patients ranged in age from 13-43 years, one was male while three were female. The tumours were situated in the parotid gland, submandibular gland and palate (two cases). The intra-vascular tumour consisted of single, clustered and solid cords of cells within multiple muscular walled blood vessels and capillaries both in the capsule and in the tumour. Immunoperoxidase staining confirmed that the intra-vascular cells were phenotypically identical to those of the tumour. The possibility that the intra-vascular tumour represents artefactual 'spillage' has been considered, however there is some histological evidence suggesting that this phenomenon represents true vascular invasion. CONCLUSIONS: The biological significance of intra-vascular tumour in pleomorphic adenomas is unknown. Thus far there has been no correlation with either recurrence or metastases.
