Catálogo de publicaciones - revistas

<jats:p>Based on the generalized truncated second-order moments, an approximate analytical formula of the beam propagation factor <jats:italic>M</jats:italic> <jats:sup>2</jats:sup> of high-power laser beams passing through the optical system with multiple hard-edged apertures is deduced. Numerical examples of the beams passing through an aperture-spatial filter are enclosed, and the influences of amplitude modulations (AMs) and phase fluctuations (PFs) on the beam propagation quality of high-power laser beams passing through the multi-apertured <jats:italic>ABCD</jats:italic> optical system are considered and discussed. It is shown that PFs are able to degrade the beam propagation quality of laser beams more than AMs when the high-power laser beams passing through the aperture-spatial filter, furthermore, one or two aperture-lens optical systems configured appropriate aperture parameters are both able to upgrade the beam propagation quality of high-power laser beams. The <jats:italic>M</jats:italic> <jats:sup>2</jats:sup> factor of Gaussian beam passing through the multi-aperture optical system is a special case in this paper.</jats:p>

<jats:p>Inhibiting the radiative radiation is an efficient approach to enhance quantum yields in a solar sell. This work carries out the inhibition of radiative recombination rate (RRR) in a quantum photocell with two coupled donors. We perform explicit calculations of the transition rates, energy gaps and the absorbed solar wavelength-dependent RRR, and find that two different regimes play the crucial roles in inhibiting RRR. One is the quantum coherence generated from two different transition channels, the other includes the absorbed photon wavelength and gaps between the donor and acceptor in this proposed photocell model. The results imply that there may be some efficient ways to enhance the photoelectron conversion compared to the classic solar cell.</jats:p>

<jats:p>We demonstrate a simple and fast way to produce <jats:sup>87</jats:sup>Rb Bose–Einstein condensates. A digital optical phase lock loop (OPLL) board is introduced to lock and adjust the frequency of the trap laser, which simplifies the optical design and improves the experimental efficiency. We collect atoms in a magneto-optical trap, then compress the cloud and cut off hot atoms by rf knife in a magnetic quadrupole trap. The atom clouds are then transferred into a spatially mode-matched optical dipole trap by lowering the quadrupole field gradient. Our system reliably produces a condensate with 2×10<jats:sup>6</jats:sup> atoms every 7.5 s. The compact optical design and rapid preparation speed of our system will open the gate for mobile quantum sensing.</jats:p>

<jats:p>We demonstrate the transmission of a microwave frequency signal at 10 GHz over a 112-km urban fiber link based on a novel simple-architecture electronic phase compensation system. The key element of the system is the low noise frequency divider by 4 to differentiate the frequency of the forward signal from that of the backward one, thus suppressing the effect of Brillouin backscattering and parasitic reflection along the link. In terms of overlapping Allan deviation, the frequency transfer instability of 4.2 × 10<jats:sup>−15</jats:sup> at 1-s integration time and 1.6 × 10<jats:sup>−18</jats:sup> at one-day integration time was achieved. In addition, its sensitivity to the polarization mode dispersion in fiber is analyzed by comparing the results with and without laser polarization scrambling. Generally, with simplicity and robustness, the system can offer great potentials in constructing cascaded frequency transfer system and facilitate the building of fiber-based microwave transfer network.</jats:p>

<jats:p>A theoretical model was proposed to describe the effects of external bias electric field on terahertz (THz) generated in air plasma. The model predicted that for a plasma in a bias electric field, the amplification effect of the THz wave intensity increases with the increase of the excitation laser wavelength. We experimentally observed the relationship between the THz enhancement effect and the electric field strength at different wavelengths. Experimental results showed a good agreement with the model predictions. These results enhance our understanding of the physical mechanism by which femtosecond lasers excite air to generate THz and extend the practical applications of THz generation and modulation.</jats:p>

<jats:p>Based on the generalized coupled nonlinear Schrödinger equation, we obtain the analytic four-bright–bright soliton solution by using the Hirota bilinear method. The interactions among four solitons are also studied in detail. The results show that the interaction among four solitons mainly depends on the values of solution parameters; <jats:italic>k</jats:italic> <jats:sub>1</jats:sub> and <jats:italic>k</jats:italic> <jats:sub>2</jats:sub> mainly affect the two inboard solitons while <jats:italic>k</jats:italic> <jats:sub>3</jats:sub> and <jats:italic>k</jats:italic> <jats:sub>4</jats:sub> mainly affect the two outboard solitons; the pulse velocity and width mainly depend on the imaginary part of <jats:italic>k<jats:sub>i</jats:sub> </jats:italic> (<jats:italic>i</jats:italic> = 1, 2, 3, 4), while the pulse amplitude mainly depends on the real part of <jats:italic>k<jats:sub>i</jats:sub> </jats:italic> (<jats:italic>i</jats:italic> = 1, 2, 3, 4).</jats:p>

<jats:p>The spectral evolution of bright soliton in a silicon-on-insulator optical waveguide is numerically simulated using the split-step Fourier method. The power and input chirp of the dark soliton and the second-order dispersion are varied to investigate the effect of dark soliton on the spectrum of bright soliton. The simulations prove that the dark soliton modifies the spectral shape of the bright soliton. Further, the variation in the power of dark soliton affects the splitting of bright soliton. Furthermore, the chirped dark soliton can improve the spectral width and flatness. The variation in the dispersion of dark soliton modifies the phase matching of the bright soliton and the dispersive wave emission, thereby affecting the spectral evolution.</jats:p>

<jats:p>The analytical expression of off-axis hollow Gaussian–Schell model vortex beam (HGSMVB) generated by anisotropic Gaussian–Schell model source is first introduced. The evolution properties of off-axis HGSMVB propagating in turbulent atmosphere are analyzed. The results show that the off-axis HGSMVB with smaller coherence length or propagating in stronger turbulent atmosphere will evolve from dark hollow beam into Gaussian-like beam with a larger beam spot faster. The beams with different values of integer order <jats:italic>N</jats:italic> or the position for hollow and vortex factor <jats:italic>R</jats:italic> will have almost the same Gaussian-like spot distribution at the longer propagation distance.</jats:p>

<jats:p>We introduce a modified weak value that is related to the mean value of input meter variable. With the help of the modified weak value, the validity conditions for various modified versions of weak value formalism are investigated, in terms of the dependence of the pointer shift on the mean value of the input meter. The weak value formalism, often used to represent the pointer shift, with the modified weak value is of great use in simplifying calculations and giving guidance of practical experiments whenever the mean value of the input meter variable is nonzero. The simulation in a qubit system is presented and coincident well with our theoretical result.</jats:p>

<jats:p>Narrowband and high-transmission optical filters are extensively used in color display technology, optical information processing, and high-sensitive sensing. Because of large ohmic losses in metallic nanostructures, metallic filters usually exhibit low transmittances and broad bandwidths. By employing both strong field enhancements in metallic nano-slits and the Wood’s anomaly in a periodic metallic grating, an extra-narrowband and high-transmission metallic filter is numerically predicted in an ultrathin single-layer metallic grating. Simulation results show that the Wood’s anomaly in the ultrathin (thickness <jats:italic>H</jats:italic> = 60 nm) single-layer metallic grating results in large field enhancements in the substrate and low losses in the metallic grating. As a result, the transmission bandwidth (transmittance <jats:italic>T</jats:italic> &gt; 60%) at <jats:italic>λ</jats:italic> = 1200 nm is as small as Δ<jats:italic>λ</jats:italic> <jats:sub>FWHM</jats:sub> = 1.6 nm, which is smaller than 4% of that in the previous thin dielectric and metallic filters. The corresponding quality factor is as high as <jats:italic>Q</jats:italic> = <jats:italic>λ</jats:italic>/Δ<jats:italic>λ</jats:italic> <jats:sub>FWHM</jats:sub> = 750, which is 40 times greater than that in the previous reports. Moreover, the thickness of our metallic filter (<jats:italic>H</jats:italic> = 60 nm) is smaller than 40% of that in the previous reports, and its maximum transmittance can reach up to 80%. In experiments, a narrowband metallic filter with a bandwidth of about Δ<jats:italic>λ</jats:italic> <jats:sub>FWHM</jats:sub> = 10 nm, which is smaller than 25% of that in the previous metallic filters, is demonstrated.</jats:p>