By tens-of-picosecond resolved fluorescence detection we study Förster resonance energy transfer between a donor
and a black-hole-quencher bound at the 5'- and 3'-positions of an oligonucleotide probe matching the highly
polymorphic region between codons 51 and 58 of the human leukocyte antigen DQB1 0201 allele, conferring
susceptibility to type-1 diabetes. The probe is annealed with non-amplified genomic DNAs carrying either the
0201 sequence or other DQB1 allelic variants. We detect the longest-lived donor fluorescence in the case of
hybridization with the 0201 allele and definitely faster and distinct decays for the other allelic variants, some of
which are single-nucleotide polymorphic.
By using hybrid photodetectors we exploited the photon-number correlations existing in bipartite optical states
to demonstrate the effect of multiple-photon subtraction on the generation of conditional states in the pulsed
regime. We operated on both classical and quantum Gaussian bipartite states in the mesoscopic regime without
background subtraction and corrections. The obtained conditional states are non-Gaussian in nature, thus particularly
useful for applications to Quantum Information. All the experimental results are in excellent agreement
with theoretical models.
By tens-of-picosecond resolved fluorescence detection (TCSPC, time-correlated single-photon counting) we study
Förster resonance energy transfer between a donor and a black-hole-quencher acceptor bound at the 5'- and 3'-positions of a synthetic DNA oligonucleotide. This dual labelled oligonucleotide is annealed with either the
complementary sequence or with sequences that mimic single-nucleotide polymorphic gene sequences: they differ
in one nucleotide at positions near either the ends or the center of the oligonucleotide. We find donor fluorescence
decay times whose values are definitely distinct and discuss the feasibility of single nucleotide polymorphism
genotyping by this method.
We present an experimental scheme for the reconstruction of the Wigner function of optical states. The method
is based on direct intensity measurements by non-ideal photodetectors operated in the linear regime. We mix,
at a beam-splitter, the signal state with a set of coherent probes of known complex amplitudes, and measure the
probability distribution of the detected photons for each probe. The Wigner function is given by a suitable sum of
those probability distributions. For comparison, the same data are analyzed to obtain the number distributions
and the Wigner functions for photons.
A snake photon detection based imaging technique developed by our group is explained in details and its performances
compared with those obtained by other experimentalists. The technique is based on simultaneous
application of time and spatial-mode selection. We also show that in these very particular working conditions
commonly used plastic tissue phantoms display non tissue-like scattering properties.
Joint signal-idler photoelectron distributions of twin beams have been measured recently in two distinct regimes:
either the mean number of photon pairs per one pump pulse is lower that the number of independent modes or
vice versa. Exploiting a microscopic quantum theory for joint quasi-distributions in parametric down-conversion
based on the model of superposition of signal and noise we characterize properties of twin beams in terms of quasidistributions
using experimental data. In parallel to the microscopic model, joint signal-idler photon-number
distribution is reconstructed using the method of maximum likelihood. Negative values as well as oscillating
behavior in quantum region are characteristic for the joint signal-idler quasi-distributions of integrated intensities.
The larger the mean number of photon pairs per mode the weaker the quantum features are. However, they
survive even in the mesoscopic regime, i.e. when tens of photon pairs per mode are present on average. Also
the conditional and difference photon-number distributions are shown to be sub-Poissonian and sub-shot-noise,
respectively. Violation of classical inequalities for photon-number distributions is discussed.
We demonstrate, by direct measurement of the number of photons in signal and idler, that the twin-beam of light
produced by ps-pulsed spontaneous parametric downconversion is endowed with sub-shot-noise photon-number
correlations in a mesoscopic intensity regime (more than 1000 detected photons). The noise reduction, calculated
from the variance of the difference in the numbers of detected-photons, resulted to be 3.25 dB below the shot-noise
level. From experimental data we can recover joint photon-number distribution and a negative-valued
joint signal-idler quasi-distributions of integrated intensities, which demonstrates the nonclassical character of
the generated field.
We implement a frequency degenerate seeded downconversion process in which the seed field is a spatially
multimode chaotic field. The two output fields are quantum correlated in space and intensity and maintain the
same spatial and temporal structure as the seeding field and thus represent two almost twin multimode fields
that can be used for ghost imaging applications.
Laser techniques have demonstrated very promising applications for diagnostic and restoration purposes in art conservation. Nevertheless only in the last decade a growing interest in Europe has brought this innovative approach to be tested and validated on various important tasks: laser cleaning of stone, metals, paintings, paper etc; structural laser diagnostics of frescoes and art objects; compositional laser diagnostics of materials; environmental laser monitoring etc. Many programs funded by the European Commission have contributed to the development of new laser instruments and techniques. Presently the COST Action G7 is pursuing the main task of monitoring the advancements achieved in the development of new instrumentation, accumulating validation of laser based techniques with case studies, extending the use of laser for conservation in Europe and other countries, selecting best practices and preparing safety guidelines.
In the interaction among three non-collinear plane-waves under type I phase matching conditions, if one among the fields is non-depleted, the remaining two are holographic replicas of each other. We calculate the holographic wave-front generated by a non-plane object wave-front and a plane reference wave-front and present experimental holographic images, ofpoint-source objects, obtained by choosing object- and reference-field frequencies among o, ''2 and w in any possible combination. With the plane reference at (03, the holographic field generated by downconversion is phase-conjugate with respect to the object field, an effect suitable for all-optical real-time treatments of optical bits. Preliminary applications to optical computing and imaging are presented. The feasibility of frill correction ofphase distortions in powerftil-laser beam profiles is discussed.
3-D holographic images of extended diffusing objects are simultaneously recorded and reconstructed by optical cross- correlation in a second-order non-linear crystal. An interaction geometry in which the phase-matched object and reference fields propagate slightly non-colinearly is particularly convenient to obtain these Second Harmonic Generated (SHG) holograms.
A method of wavefronts' cross-correlation by means of Second Harmonic Generated Hologram (SHG hologram) is considered. According to this method, the interference pattern of an object and reference waves is recorded in a nonlinear light-sensitive material using its second order nonlinearity. The SHG hologram generates a wave that forms the reconstructed image of the object, the frequency of the reconstructed wave being doubled. An expression that describes the electrical field of the reconstructed wave is deduced. It is suggested to use the transforming properties of the SHG hologram for constructing the network of changeable interconnection lines which operates on the principle 'light is controlled by light'. The experiment has confirmed the ability of the SHG hologram of forming high quality images of arbitrary objects. The ways of overcoming the effect of doubling the frequency of the light after each act of a signal transformation are considered. The theory has shown that by using the effect of 'down-conversion' it is possible either to return the frequency of the signal to its initial value or to sustain the value of the frequency at the constant level.
A new method of wavefronts' cross-correlation by means of so-called Second-Harmonic-Generated Hologram (SHG hologram) is considered. According to this method the interference pattern of an object wave and a reference wave is recorded in nonlinear light-sensitive material using its second order nonlinearity. The SHG hologram generates the wave that forms the reconstructed image of the object without time delay in the moment when interfering wavefronts intersect the image of the object without time delay in the moment when interfering wavefronts intersect the light-sensitive material, the frequency of the reconstructed wave being doubled in comparison with the frequency of the recorded waves. The expression that describes the electrical field of the reconstructed wave is deduced. Basing on this expression the methods for the construction of the image generated by SHG hologram are developed. It is suggested to use the transforming properties of the SHG hologram for constructing the network of changeable interconnection lines, which operates on the principle `light is controlled by light'. The experiment on the recording of the SHG hologram was carried out. The SHG hologram was recorded in BBO I crystal with the help of Nd:YAG pulse laser. The experiment has confirmed the ability of the SHG hologram to form high quality images.
Progress in the use of miniature optoelectronic systems based on Coherent-Light-Emitting- Diodes (CLEDs) and CLED-pumped solid-state lasers (Microlasers) is reported for: (1) retina photocoagulation with 800 nm diode lasers and 532 nm Nd:YAB Microlasers; (2) endoscopic photocoagulation of gastrointestinal tumors with an 800 nm high power multi-CLED system; (3) 800 nm diode laser-assisted microvascular anastomosis; (4) photodynamic therapy of tumors with 780 nm CLED and 660 nm LED.
Irradiation with 86 J/cm2 of cultures of Fisher-rate thyroid cells (FRTL5) in the presence of daunomycin derivatives at wavelengths between 488 and 595 nm i.e., in the visible- absorption bands of these drugs, is shown to enhance their cytotoxicity. Daunomycin, its 4- demethoxy derivative, 5-iminodaunomycin, and two amino-substituted 4-demethoxy derivatives of daunomycin are tested. While a 2-h exposure to the drugs in the dark produces 50 short-term cell mortality at dosages (LD50) in the range 23 to 138 (mu) g/ml, irradiation administered during the cell exposure to the drugs is found to lower the LD50 values down to the range 45 to 289 ng/ml. Furthermore, while the LD50 values for all drugs in the absence of photoactivation are similar, if light is administered those for the 4- demethoxy compounds are lowered by 3 orders of magnitude and those for the other derivatives by 2 orders of magnitude. Microfluorimetric investigations reveal that photoactivation causes fading of the drug fluorescence in the perinuclear cytoplasm. The effect is more pronounced for drugs with higher photosensitizing properties. The nonfluorescent photoproducts which are formed in the cells during photoactivation exhibit a cytotoxic activity that is, at long term, lower than that of the original drug. The authors cannot yet assess which excited-state property of anthracyclines plays the key role in the photosensitized reaction(s) responsible for both short-term cell kill and long-term toxic effects. The show, however, that such property is strongly affected by the removal of the methoxy group from the C4 position.