Search results for "SHIFT"
showing 10 items of 1226 documents
Far-field light imaging in the presence of atmospheric turbulence with rotating anti-phase apertures: Theoretical investigation
2017
We investigated the diffraction of far-field light objects in the presence of turbulence formed by an optical system with a rotating anti-phase mask. This mask facilitates to detect the position of faint companion in every direction around the bright companion. In the presence of atmospheric turbulence, diffraction images of distant objects are beyond the diffraction limits, the proposed phase shift mask has a merit to compensate the turbulence results high contrast astronomical imaging under partially coherent light illumination and it is proficient to increase the resolution limits in a Sparrow criterion sense. In this approach, we demonstrated the mask fabrication in laboratory condition…
Spectral anomalies in supercontinuum focused waves
2006
The diffraction-induced spectral anomalies in the focal plane of an apertured spherical wave with supercontinuum flat-top power spectrum are investigated. Coherent broadband radiation (also incoherent white light) demonstrates a strong blue shift in the vicinity of the optical axis, and discrete spectral gaps with overall red shift arise out of this central region. Unlike narrow-band light, the spectral switch effect fades away with ultra-broad spectra.
Compressive holography with a single-pixel detector.
2013
This Letter develops a framework for digital holography at optical wavelengths by merging phase-shifting interferometry with single-pixel optical imaging based on compressive sensing. The field diffracted by an input object is sampled by Hadamard patterns with a liquid crystal spatial light modulator. The concept of a single-pixel camera is then adapted to perform interferometric imaging of the sampled diffraction pattern by using a Mach-Zehnder interferometer. Phase-shifting techniques together with the application of a backward light propagation algorithm allow the complex amplitude of the object under scrutiny to be resolved. A proof-of-concept experiment evaluating the phase distributio…
Transverse effects in ring fiber laser multimode instabilities
2000
We study the influence of the transverse structure of pump and lasing fields and of the width of the doped region on the conditions for the appearance of the multimode instability in an ${\mathrm{Er}}^{3+}$-doped ring fiber laser. We show that the instability can be inhibited while maintaining a large output power when the radius of the doped region is a fraction of the core radius.
Puzzling out the proton radius puzzle
2014
The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today’s nuclear physics: after more than 50 years of research the radius of a basic constituent of matter is still not understood. This paper presents a summary of the best existing proton radius measurements, followed by an overview of the possible explanations for the observed inconsistency between the hydrogen and the muonic-hydrogen data. In the last part the upcoming experiments, dedicated to remeasuring the proton radius, are described.
ISR Experiment at A1-Collaboration
2019
The discrepancy between the proton charge radius extracted from the muonic hydrogen Lamb shift measurement and the best present value obtained from the elastic scattering experiments, remains unexplained and represents a burning problem of today’s nuclear physics. In a pursuit of reconciling the puzzle an experiment is underway at MAMI, which exploits the radiative tail of the elastic peak to study the properties of electromagnetic processes and to extract the proton charge form factor $ \left( {\mathop G\nolimits_E^p } \right) $ at extremely small Q2. This paper reports on the latest results of the first such measurement performed at the three-spectrometer facility of the A1-Collaboration,…
Isotope shift of40,42,44,48Ca in the 4s2S1/2→ 4p2P3/2transition
2015
We report on improved isotope shift measurements of the isotopes 40,42,44,48Ca in the 4s2S1/2→4p2P3/2 transition using collinear laser spectroscopy. Accurately known isotope shifts in the 4s2S1/2→4p2P1/2 (D1) transition were used to calibrate the ion beam energy with an uncertainty of ΔU ≈ ± 0.25 V. The accuracy in the D2 transition was improved by a factor of 5–10. A King-plot analysis of the two transitions revealed that the field shift factor in the D2 line is about 1.8(13)% larger than in the D1 transition which is ascribed to relativistic contributions of the 4p1/2 wave function.
Fluctuating laser field that induces a blueshift in harmonic generation
1998
The spectrum of a two-level atom in the presence of a multimode laser pulse is calculated. The field is allowed to fluctuate in amplitude or in phase; the emitted spectrum has richer emission lines than in the case of the nonfluctuating field and shows peaks shifted toward the blue with respect to the traditional harmonic peaks. The position of the lines is predicted by the formula ω2n+1=(2n+1)(1+Δ)ωL with Δ being a parameter that can be found numerically. In this way the fluctuations seem to result in an effective increase of the laser frequency.
Discovery of a redshifted X-ray emission line in the symbiotic neutron star binary 4U 1700+24
2005
We present the spectral analysis of an XMM-Newton observation of the X-ray binary 4U 1700+24, performed during an outburst in August 2002. The EPIC-PN spectrum above 1 keV can be modeled by a blackbody plus Comptonization model, as in previous observations. At lower energies, however, we detect a prominent soft excess, which we model with a broad Gaussian centered at ~0.5 keV. In the high resolution RGS spectrum we detect a single emission line, centered at 19.19^{+0.05}_{-0.09} \AA. We discuss two possible interpretations for this line: O VIII at redshift z=0.012^{+0.002}_{-0.004} or Ne IX at redshift z~0.4.
Gravitational waves from neutron stars at different evolutionary stages
2003
We study how the internal structure of a neutron star and the physical processes that may occur during its evolution affect the quasi-normal mode spectrum, and consequently the gravitational radiation it emits. We discuss whether these modes can be excited and how much energy they should carry for the gravitational signal to be detectable by the first generation of interferometric antennas or by the new generation of high-frequency gravitational detectors, interferometric or resonant, that are under investigation.