We report on demonstration of non-diffracting (Bessel) beams from Electrically Pumped Vertical External Cavity
Surface Emitting Lasers (EP-VECSELs), with output powers ranging up to hundreds of milliwatts and central lobe
diameters of 10-100 μm with propagation lengths up to few tens of centimeters. To our knowledge, this is the best result
for Bessel beams generated from semiconductor light sources and is comparable to that achievable from vibronic lasers.
Novel materials, notably quantum-dot (QD) semiconductor structures offer the unique possibility of combining
exploitable spectral broadening of both gain and absorption with ultrafast carrier dynamic properties. Thanks to these
characteristics QD-based devices have enhanced the properties of ultrashort pulse lasers and opened up new possibilities
in ultrafast science and technology. In this paper we review the recent progress on the development of novel quantumdot
SESAM structures for different lasers. We also demonstrate that QD structures can be designed to provide compact
and efficient ultrashort pulse laser sources with high and low repetition rates.
Using high speed photography at sub-microsecond temporal resolution, we observed laser-induced cavitation within a
thin film of liquid. In accordance with the literature, focusing a pulse of a gaussian-like intensity distribution into the
liquid, instigated a disk-shaped cavity. The propagation of an acoustic transient, generated during the formation and
expansion of the cavity, is evidenced by secondary cavitation stimulated in the surrounding liquid. Introducing a
laguerre-gauss holographic diffractive optic element into the beam path, re-distributes the optical energy into the socalled
'doughnut mode', with an axial intensity minimum. Focusing this modulated pulse into the liquid induced a ringshaped
cavity with a notably different dynamic to that of the disk cavity, due primarily to the encapsulated droplet,
which is present from cavity initiation through expansion and subsequent deflation. In this paper we present initial
observations on the novel dynamics of the ring-shaped cavity and discuss several of the distinctive features. Particularly
the secondary cavitation induced in the surrounding liquid, and the implicated multiplexing of the acoustic transient
generated during the ring-cavity expansion, is of interest.
Novel materials, notably quantum-dot (QD) semiconductor structures offer the unique possibility of combining
exploitable spectral broadening of both gain and absorption with ultrafast carrier dynamic properties. Thanks to these
characteristics QD-based devices have enhanced the properties of ultrashort pulse lasers and opened up new possibilities
in ultrafast science and technology. In this paper we will review recent results, which demonstrate that quantum-dot
structures can be designed to provide compact and efficient ultrashort pulse laser sources with extremely high and low
repetition rates.
The development of femtosecond lasers has continued rapidly over the past decade from laboratory systems to an
impressive range of commercial devices. Novel materials, notably quantum-dot semiconductor structures, have enhanced
the characteristics of such lasers and opened up new possibilities in ultrafast science and technology. In our most recent
work, it has been demonstrated that quantum-dot structures can be designed to provide an efficient means for the
generation and amplification of ultrashort optical pulses at high repetition rates. The work also confirms that quantum
dot based semiconductor saturable absorber mirrors exhibit a degree of flexibility which allows control and tuning of the
ultrashort pulse laser systems. Further developments in ultrashort-pulse solid-state, fibre and semiconductor external
cavity lasers, by means of both active and passive semiconductor quantum dot components are also presented.
Sol-gel glasses containing copper selenide nanoparticles and having absorption band at 1.1?2.2 ?m can be used as saturable absorber passive shutter for Q-switching and mode-locking of the solid-state lasers operating in the wavelength range of 1.0?1.5 ?m. The bleaching relaxation time of the glasses was measured to be 0.46?1.4 ns in dependence on copper selenide stoichiometry.
The silica sol-gel derived glasses co-doped with CuxO and CuxSe nanoparticles and Eu3+ ions have been fabricated. The analysis of luminescence spectra of a series of glasses with different composition allows us to suppose the direct energy transfer between copper oxide nanoparticle and Eu3+ ion. A luminescence signal of europium ions occurs as the result of excitation of the complex active centres (SiO2:Cu2O:Eu3+) in the absorption range of copper oxide.
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