RESUMO
We observe the coherence of the supercontinuum generated in a nanospike chalcogenide-silica hybrid waveguide pumped at 2 µm. The supercontinuum is shown to be coherent with the pump by interfering it with a doubly resonant optical parametric oscillator (OPO) that is itself coherent with the shared pump laser. This enables coherent locking of the OPO to the optically referenced pump frequency comb, resulting in a composite frequency comb with wavelengths from 1 to 6 µm.
RESUMO
Efficient generation of a broad-band mid-infrared supercontinuum spectrum is reported in an arsenic trisulphide waveguide embedded in silica. A chalcogenide "nano-spike", designed to transform the incident light adiabatically into the fundamental mode of a 2-mm-long uniform section 1 µm in diameter, is used to achieve high launch efficiencies. The nano-spike is fully encapsulated in a fused silica cladding, protecting it from the environment. Nano-spikes provide a convenient means of launching light into sub-wavelength scale waveguides. Ultrashort (65 fs, repetition rate 100 MHz) pulses at wavelength 2 µm, delivered from a Tm-doped fiber laser, are launched with an efficiency ~12% into the sub-wavelength chalcogenide waveguide. Soliton fission and dispersive wave generation along the uniform section result in spectral broadening out to almost 4 µm for launched energies of only 18 pJ. The spectrum generated will have immediate uses in metrology and infrared spectroscopy.
Assuntos
Arsenicais/química , Nanopartículas/química , Nanotecnologia/instrumentação , Refratometria/instrumentação , Sulfetos/química , Desenho de Equipamento , Análise de Falha de Equipamento , Raios InfravermelhosRESUMO
We explore the use of a highly nonlinear chalcogenide-silica waveguide for supercontinuum generation in the near infrared. The structure was fabricated by a pressure-assisted melt-filling of a silica capillary fiber (1.6 µm bore diameter) with Ga4Ge21Sb10S65 glass. It was designed to have zero group velocity dispersion (for HE11 core mode) at 1550 nm. Pumping a 1 cm length with 60 fs pulses from an erbium-doped fiber laser results in the generation of octave-spanning supercontinuum light for pulse energies of only 60 pJ. Good agreement is obtained between the experimental results and theoretical predictions based on numerical solutions of the generalized nonlinear Schrödinger equation. The pressure-assisted melt-filling approach makes it possible to realize highly nonlinear devices with unusual combinations of materials. For example, we show numerically that a 1 cm long As2S3:silica step-index fiber with a core diameter of 1 µm, pumped by 60 fs pulses at 1550 nm, would generate a broadband supercontinuum out to 4 µm.
RESUMO
In a controlled study, 10 dogs with normal and severely damaged lungs were subjected to nuclide angiocardiographic investigations into the function of the right ventricle. The pulmonary injury was produced by infusion of oleic acid (OA) into the right atrium during controlled ventilation (IPPV). The angiocardiographic examinations were performed using 133Xenon in the first pass technique. The study compared HFJV (HFJV 100, HFJV 300) with IPPV in the non-damaged lung as well as HFJV 300 with IPPV and CPPV (PEEP 1.0 kPa) after injury by OA. Whereas for the non-damaged lung no different right ventricular (RV) function between IPPV and HFJV was observed, the RV functional parameters after OA injury under HFJV showed, as opposed to CPPV, more favourable values on the whole. This became clear in particular in the significantly higher ejection fraction (RVEF) during HFJV. The RV function which is influenced during CPPV in terms of a favourable oxygenation is the consequence of an increased mean pressure in the airways with subsequent rise in the RV afterload and decrease in the RV preload. In contrast, the more favourable RV haemodynamics during HFJV are associated with a comparatively lower mean airway pressure and a significantly worse oxygenation. As the RV function also during HFJV has to be seen in direct dependence on the mean airway or intrapulmonary pressure necessary for sufficient oxygenation, the employment of this form of ventilation in the presence of an acute respiratory insufficiency has no impact on the RV haemodynamics different from the other compared forms of ventilation.
