Search results for "tunable"
showing 10 items of 76 documents
Photoluminescence of Si nanocrystals embedded in SiO2: Excitation/emission mapping
2014
Time-resolved photoluminescence from Si nanocrystals produced by 1100∘C thermal annealing of SiOx/SiO2 multilayers were investigated by tunable laser excitation, achieving a detailed excitation/emission pattern in the visible and UV range. The emission lineshape is a gaussian curve inhomogenously broadened because of the size distribution of Si nanocrystals, the excitation spectrum consists of the overlap of two gaussian bands centered around 3.4 and 5.1 eV. The mapping of luminescence spectral components with the lifetime points out the energy cubic dependence of the spontaneous emission rate. These findings are interpreted on the basis of models proposed in literature that associate this …
Tunable photoluminescence properties of selenium nanoparticles: biogenic versus chemogenic synthesis
2020
Abstract Various technological and biomedical applications rely on the ability of materials to emit light (photoluminescence [PL]), and, among them, metal nanoparticles (NPs) and semi-conductor Quantum Dots (QDs) represent ideal candidates as sensing probes and imaging tools, portraying better PL features than conventional organic dyes. However, the knowledge of PL behavior of semiconductor NPs – i.e., selenium; SeNPs – is still in its infancy, especially for those synthesized by microorganisms. Considering the essential role played by biogenic SeNPs as antimicrobial, anticancer, and antioxidant agents, or food supplements, their PL properties must be explored to take full advantage of them…
Accelerated stabilization of coherent photon states
2018
| openaire: EC/H2020/681311/EU//QUESS Control and utilization of coherent states of microwave photons is a ubiquitous requirement for the present and near-future implementations of solid-state quantum computers. The rate at which the photon state responds to external driving is limited by the relaxation rate of the storage resonator, which poses a trade-off between fast control and long storage time. Here, we present a control scheme that is designed to drive an unknown photon state to a desired coherent state much faster than the resonator decay rate. Our method utilizes a tunable environment which acts on an ancillary qubit coupled to the resonator. By periodically resetting the qubit and…
Multi-longitudinal mode emission in a bidirectional laser model
2011
Multi-longitudinal mode emission is a fundamental issue in laser physics. Interestingly enough, the mechanisms responsible for the transition from single- to multi-longitudinal mode emission have not been completely clarified yet. For example, it is well known that in unidirectional ring lasers the Rabi splitting of the lasing transition can lead to multimode emission even in a homogeneously broadened medium, the so called Risken-Nummedal—Graham-Haken instability (RNGHI) [1]. In spite of being known since the late sixties, only in the recent years a couple of experiments have demonstrated “dressed” versions of the RNGHI [2], i.e., up to day there are not clear demonstrations of this basic m…
Multimode emission in inhomogeneously broadened ring lasers
2001
The threshold for multilongitudinal-mode emission in inhomogeneously broadened ring lasers is analytically investigated. In the homogeneous limit the multimode instability corresponds to the classical Risken–Nummedal–Graham–Haken instability. It is found that by increasing the inhomogeneous linewidth, the instability threshold is decreased and the growth of high-frequency side modes is favored. In the limit where the population-inversion decay rate γ‖ is much smaller than the polarization decay rate γ⊥ (class B lasers), analytical expressions for the instability threshold are found, which are then generalized to three-level lasers for a comparison with experimental results obtained with erb…
Resonance Ionization Laser Ion Source - Off-line tests at TRIUMF
2004
Resonance ionization laser ion sources (RILIS) developed into the most powerful tool for radioactive ion beam production at on-line facilities, as they provide a selective ionization process with inherent suppression of unwanted isobaric contaminations at the ion source. While typical tunable laser systems for these applications are based on dye lasers, we developed an all solid state laser system which consists of three pulsed titanium:sapphire (ti:sa) lasers pumped by a single high repetition rate Nd:YAG laser. Each ti:sa laser provides up to 2.5 W average output power at 12 kHz repetition rate in the wavelength region of 700-950 nm with optional frequency doubling in BBO crystals. This l…
Ion storage technique for very long living states: The decay rate of the 5D 3/2 state of Ba II
1979
The metastable 5D 3/2 state of Ba+ is used to demonstrate the possibility of the ion storage technique for the measurement of extremely long lived states. The ions are confined in a r.f. quadrupole trap and excited by a strong pulsed tunable dye laser to the 6P 1/2 state which partially decays into the 5D 3/2 state. Sampling of the time development of the ground state population leads to the determination of the 5D 3/2 decay rate. Using He as a buffer gas at a pressure of about 10−6 mbar to initially store the ions, varying the gas density and extrapolating to zero pressure, we find for the lifetime $$\tau _{D_{3/2} } = 17.5 \pm 4s$$ .
29SiH4 and 30SiH4: Dipole moment parameters of the dyad from Stark effect observations with laser sidebands
1990
Abstract The linear Stark effect within the ν 2 ν 4 dyad of 29SiH4 and 30SiH4 has been investigated by applying the infrared sideband technique at microwave modulation frequencies. Two vibration-induced dipole moment parameters have been measured for each isotopomer on natural abundance samples.
Statistical description of soliton clustering in fiber lasers with slow-gain dynamics
2014
We demonstrate theoretically that the dynamic clustering of solitons observed in a variety of experiments are due to the initial phase and position of interacting solitons with the slow gain dynamics of the fiber laser.
Tunable defects in colloidal photonic crystals
2006
We present a bottom-up approach for the construction of tunable functional defects in colloidal photonic crystals (CPCs). These structures incorporate polyelectrolyte multilayer (PEM) planar defects embedded in silica CPCs through a combination of evaporation induced self-assembly and microcontact transfer printing. We show how the enormous chemical diversity inherent to PEMs can be harnessed to create chemically active defect structures responsive to solvent vapor pressures, light, temperature as well as redox cycling. A sharp transmission state within the photonic stopband, induced by the PEM defect, can be precisely, reproducibly and in some cases reversibly tuned by these external stimu…