Catálogo de publicaciones - revistas

<jats:p> <jats:italic>Soliton molecules were first discovered in optical systems and are currently a hot topic of research. We obtain soliton molecules of the (2+1)-dimensional fifth-order KdV system under a new resonance condition called velocity resonance in theory. On the basis of soliton molecules, asymmetric solitons can be obtained by selecting appropriate parameters. Based on the N-soliton solution, we obtain hybrid solutions consisting of soliton molecules, lump waves and breather waves by partial velocity resonance and partial long wave limits. Soliton molecules, and some types of special soliton resonance solutions, are stable under the meaning that the interactions among soliton molecules are elastic. Both soliton molecules and asymmetric solitons obtained may be observed in fluid systems because the fifth-order KdV equation describes the ion-acoustic waves in plasmas, shallow water waves in channels and oceans</jats:italic>.</jats:p>

<jats:p> <jats:italic>We report the realization of quantum logic spectroscopy on the</jats:italic> <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub>→ <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>0</jats:sub> <jats:italic>clock transition of a single</jats:italic> <jats:sup>27</jats:sup> <jats:italic>Al</jats:italic> <jats:sup>+</jats:sup> <jats:italic>ion. This ion is trapped together with a</jats:italic> <jats:sup>40</jats:sup> <jats:italic>Ca</jats:italic> <jats:sup>+</jats:sup> <jats:italic>ion in a linear Paul trap, coupled by Coulomb repulsion, which provides sympathetic Doppler laser cooling and also the means for internal state detection of the clock state of the</jats:italic> <jats:sup>27</jats:sup> <jats:italic>Al</jats:italic> <jats:sup>+</jats:sup> <jats:italic>ion. A repetitive quantum nondemolition measurement is performed to improve the fidelity of state detection. These techniques are applied to obtain clock spectroscopy at approximately 45 Hz. We also perform the preliminary locking on the</jats:italic> <jats:sup>1</jats:sup> <jats:italic>S</jats:italic> <jats:sub>0</jats:sub> → <jats:sup>3</jats:sup> <jats:italic>P</jats:italic> <jats:sub>0</jats:sub> <jats:italic>clock transition. Our work is a fundamental step that is necessary toward obtaining an ultra-precision quantum logic clock based on</jats:italic> <jats:sup>40</jats:sup> <jats:italic>Ca</jats:italic> <jats:sup>+</jats:sup>-<jats:sup>27</jats:sup> <jats:italic>Al</jats:italic> <jats:sup>+</jats:sup> <jats:italic>ions</jats:italic>.</jats:p>

<jats:p> <jats:italic>Boron carbide (B</jats:italic> <jats:sub>4</jats:sub> <jats:italic>C) coatings have high reflectivity and are widely used as mirrors for free-electron lasers in the x-ray range. However, B</jats:italic> <jats:sub>4</jats:sub> <jats:italic>C coatings fabricated by direct-current magnetron sputtering show a strong compressive stress of about</jats:italic> −3 <jats:italic>GPa. By changing the argon gas pressure and nitrogen-argon gas mixing ratio, we are able to reduce the intrinsic stress to less than</jats:italic> −1 <jats:italic>GPa for a 50-nm-thick B</jats:italic> <jats:sub>4</jats:sub> <jats:italic>C coating. It is found that the stress in a coating deposited at 10 mTorr is</jats:italic> −0.69 <jats:italic>GPa, the rms roughness of the coating surface is 0.53 nm, and the coating reflectivity is 88%, which is lower than those of coatings produced at lower working pressures. When the working gas contains 8% nitrogen and 92% argon, the B</jats:italic> <jats:sub>4</jats:sub> <jats:italic>C coating shows not only</jats:italic> −1.19 <jats:italic>GPa stress but also a low rms roughness of 0.16 nm, and the measured reflectivity is 93% at the wavelength of 0.154 nm</jats:italic>.</jats:p>

<jats:p> <jats:italic>A high-Q quartz crystal microbalance (QCM) sensor with a fundamental resonance frequency of 210 MHz is developed based on inverted mesa technology. The mass sensitivity reaches</jats:italic> 5.332 × 10<jats:sup>17</jats:sup> <jats:italic>Hz/kg at the center of the electrode, which is 5–7 orders of magnitude higher than the commonly used 5 MHz or 10 MHz QCMs (their mass sensitivity is</jats:italic> 10<jats:sup>10</jats:sup>–10<jats:sup>12</jats:sup> <jats:italic>Hz/kg). This mass sensitivity is confirmed by an experiment of plating 1-ng rigid aluminium films on the surface of the QCM sensor. By comparing the changes in QCM equivalent parameters before and after coating the aluminum films, it is found that the QCM sensor maintains the high-Q characteristics of the quartz crystal while the mass sensitivity is significantly improved. Therefore, this QCM sensor may be used as a promising analytical tool for applications requiring high sensitivity detection</jats:italic>.</jats:p>

<jats:p> <jats:italic>We report on an injection seeded 1 kHz single frequency pulsed Nd:YAG ring laser with pulse energy of 5.2 mJ and pulse width of 9.9 ns. The ramp-fire technique is used to maintain single frequency operation and the cavity length is modulated by an intracavity RbTiOPO</jats:italic> <jats:sub>4</jats:sub> <jats:italic>(RTP) crystal. The frequency stability (rms) of the output pulse is 1.99 MHz over 1 min and the linewidth is 64 MHz</jats:italic>.</jats:p>

<jats:p> <jats:italic>We propose a design and numerical study of an optically blueshift and redshift switchable metamaterial (MM) absorber in the terahertz regime. The MM absorber comprises a periodic array of metallic split-ring resonators (SRRs) with semiconductor silicon embedded in the gaps of MM resonators. The absorptive frequencies of the MM can be shifted by applying an external pump power. The simulation results show that, for photoconductivity of silicon ranging between 1 S/m and 4000 S/m, the resonance peak of the absorption spectra shifts to higher frequencies, from 0.67 THz to 1.63 THz, with a resonance tuning range of 59%. As the conductivity of silicon increases, the resonance frequencies of the MM absorber are continuously tuned from 1.60 THz to 1.16 THz, a redshift tuning range of 28%. As the conductivity increases above 30000 S/m, the resonance frequencies tend to be stable while the absorption peak has a merely tiny variation. The optical-tuned absorber has potential applications as a terahertz modulator or switch</jats:italic>.</jats:p>

<jats:p> <jats:italic>A V-folded digital laser using a spatial light modulator (SLM) for intra-cavity loss shaping is exploited to generate Hermite–Gaussian modes with on-demand mode order. With a π/2 astigmatic mode converter, vortex beams carrying on-demand orbital angular momentum (OAM) with a tunable range from −11ħ to 12ħ are obtained. The mode order of the HG mode, hence the OAM of the vortex beam, is digitally switched by changing the phase pattern imposed on the SLM without requiring any mechanic alignment of the cavity. This work has great potential applications in various OAM-tunable vortex beams</jats:italic>.</jats:p>

<jats:p> <jats:italic>Landau–Zener–Stückelberg (LZS) interference has drawn renewed attention to quantum information processing research because it is not only an effective tool for characterizing two-level quantum systems but also a powerful approach to manipulate quantum states. Superconducting quantum circuits, due to their versatile tunability and degrees of control, are ideal platforms for studying LZS interference phenomena. We use a superconducting Xmon qubit to study LZS interference by parametrically modulating the qubit transition frequency nonlinearly. For dc flux biasing of the qubit slightly far away from the optimal flux point, the qubit excited state population shows an interference pattern that is very similar to the standard LZS interference in linear regime, except that all bands shift towards lower frequencies when increasing the rf modulation amplitude. For dc flux biasing close to the optimal flux point, the negative sidebands and the positive sidebands behave differently, resulting in an asymmetric interference pattern. The experimental results are also in good agreement with our analytical and numerical simulations</jats:italic>.</jats:p>

<jats:p> <jats:italic>Optical operations have served as the basis of spectroscopy and imaging in terahertz regimes for a long time. Available lenses are practical tools for modulations. We fabricate a kind of biconvex lens from the natural dolomite cluster. The lens works well at 0.1 THz based on the relatively high refractive index and low absorption coefficients. Compared with the lens fabricated by a dolomite stone, such a lens can focus dispersive terahertz beam efficiently in terahertz imaging systems, which indicates that natural minerals hold promising applications in terahertz optics</jats:italic>.</jats:p>

<jats:p> <jats:italic>A femtosecond LBO optical parametric oscillator (OPO) with widely adjustable repetition rate by fractionally decrement of the cavity length is demonstrated. The repetition rate of 755MHz to 1.43 GHz at an interval of 75.5MHz is realized, which is 10 to 19 times that of the pump laser. The properties of output signal at 750nm at different repetition rates are studied. The power of signal decreases with increasing the repetition rate. The maximum power of 194mW at the repetition rate of 755MHz and the minimum power of 22mW at repetition rate of 1.43 GHz for the signal at 750nm are obtained for the pump power of 3 W</jats:italic>.</jats:p>