ABSTRACT
We report on stable, long-term operation of a diode-pumped solid-state laser (DPSSL) amplifying 15 ns pulses at 1029.5 nm wavelength to 10 J energy at 100 Hz pulse rate, corresponding to 1 kW average power, with 25.4% optical-to-optical efficiency. The laser was operated at this level for over 45 minutes (â¼3 · 105 shots) in two separate runs with a rms energy stability of 1%. The laser was also operated at 7 J, 100 Hz for 4 hours (1.44 · 106 shots) with a rms long-term energy stability of 1% and no need for user intervention. To the best of our knowledge, this is the first time that long-term reliable amplification of a kW-class high energy nanosecond pulsed DPSSL at 100 Hz has been demonstrated.
ABSTRACT
We report on efficient and stable, type-I phase-matched second harmonic conversion of a nanosecond high-energy, diode-pumped, Yb:YAG laser. With a frequency-doubling crystal in an enclosed, temperature controller with optical windows, 0.5% energy stability was achieved for approximately half an hour. This resulted in 48.9 J pulses at 10 Hz (489 W) and a conversion efficiency of 73.8%. These results are particularly important for stable and reliable operation of high-energy, frequency-doubled lasers.
ABSTRACT
We report on the successful demonstration of second and third harmonic conversion of a high pulse energy, high average power 1030 nm diode pumped Yb-doped yttrium aluminum garnet (Yb:YAG) nanosecond pulsed laser in a large aperture lithium triborate (LBO) crystal. We demonstrated generation of 59.7 J at 10 Hz (597 W) at 515 nm (second harmonic) and of 65.0 J at 1 Hz (65 W) at 343 nm (third harmonic), with efficiencies of 66% and 68%, respectively. These results, to the best of our knowledge, represent the highest energy and power reported for frequency conversion to green and UV-A wavelengths.
ABSTRACT
In this paper, we present a model to predict thermal stress-induced birefringence in high energy, high repetition rate diode-pumped Yb:YAG lasers. The model calculates thermal depolarisation as a function of gain medium geometry, pump power, cooling parameters, and input polarisation state. We show that model predictions are in good agreement with experimental observations carried out on a DiPOLE 100 J, 10 Hz laser amplifier. We show that single-pass depolarisation strongly depends on input polarisation state and pumping parameters. In the absence of any depolarisation compensation scheme, depolarisation varies over a range between 5% and 40%. The strong dependence of thermal stress-induced depolarisation on input polarisation indicates that, in the case of multipass amplifiers, the use of waveplates after every pass can reduce depolarisation losses significantly. We expect that this study will assist in the design and optimisation of Yb:YAG lasers.
ABSTRACT
Interleukin (IL)-12 is a cytokine originally identified from medium conditioned by an Epstein-Barr virus transformed cell line. IL-12 has been shown to increase IFN-gamma secretion from NK and T cells, significantly enhance cytolytic activity in both of these cell types, and promote the development of Th1/Tc1 immune responses. These properties make IL-12 an attractive candidate for the development of various clinical protocols ranging from the treatment of viral diseases to tumor immunotherapy. The initial attempts to use IL-12 in the treatment of tumors demonstrated toxicity at potentially therapeutic doses. To circumvent the toxicity associated with IL-12 administration, the authors have developed an adoptive immunotherapy protocol that uses IL-12 for a brief period during ex vivo T cell activation. They show that IL-12 conditioning may be achieved without altering the growth characteristics of the in vitro expanding T cells. T cells generated in the presence of IL-12 show a shift to a Th1/Tc1 dominant phenotype. The resultant cells are more potent killers in vitro and in vivo as assessed by CTL assays and tumor regression. The ability to harness the potent Th1/Tc1 generating potential of IL-12 while avoiding its associated in vivo toxicity has the potential to benefit a large number of clinical trial protocols using adoptive transfer of T cells specific for tumors, viruses, or intracellular pathogens.