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<jats:title>Abstract</jats:title> <jats:p>Coherent control of fragmentation of CH<jats:sub>3</jats:sub>I using shaped femtosecond pulse train is investigated. The dissociation processes can be modulated by changing the separation of the shaped pulse train, and the yield of I<jats:sup>+</jats:sup> under the irradiation of the optimal pulse is significantly increased compared with that using the transform-limited pulse. We discuss the control mechanism of dissociation processes with coherent interference in time domain. A three-pulse control model is proposed to explain the counterintuitive experimental results.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The interaction of MeV <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{H}}}_{2}^{+}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_093401_ieqn3.gif" xlink:type="simple" /> </jats:inline-formula> molecular ions with thin layer graphene and graphite foils was studied by using a high-resolution electrostatic analyzer. A large number of fragment protons were observed at zero degree (along the beam direction) when the <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{H}}}_{2}^{+}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_093401_ieqn4.gif" xlink:type="simple" /> </jats:inline-formula> beam was passing through the monolayer graphene foil, which indicates that the electron of the <jats:inline-formula> <jats:tex-math><?CDATA ${{\rm{H}}}_{2}^{+}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> </mml:mrow> </mml:msubsup> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_093401_ieqn5.gif" xlink:type="simple" /> </jats:inline-formula> molecular ions can be stripped easily even by the monolayer graphene foil. More trailing than leading protons were found in the energy spectrum, which means significant wake effect was observed in the monolayer graphene foil. The ratio of the numbers of trailing protons over leading protons first increased with the thickness for the much thinner graphene foils, and then decreased with the thickness for the much thicker graphite foils, which indicates that the bending effect of the wake field on the trailing proton varied with the foil thickness.</jats:p>

<jats:p>We have investigated the electron scattering from the freely movable spin-1/2 particle in the presence of a linearly polarized laser field in the first Born approximation. The laser-dressed state of electrons is described by a time-dependent wave function which is derived from a perturbation treatment. With the aids of numerical simulations, we explore the dependencies of the differential cross section on the laser field intensity as well as the electron-impact energy. Due to the mobility of the target, the differential cross section of this process is smaller than that of Mott scattering.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>It is difficult to obtain a clear image in underwater turbulence environment with classical imaging methods due to the absorption, scattering, and underwater turbulence on the propagation beam. However, ghost imaging (GI), a non-locally imaging technique, has shown the turbulence-free ability in atmospheric turbulence by exploiting the second-order correlation between the signal beam and the reference beam. In this paper, we experimentally investigate the imaging quality of GI affected by the underwater environment, where the underwater environment is simulated by a 1 m × 0.4 m × 0.4 m tank with distilled water. The water temperature is controlled by a heater inside the tank, and a temperature gradient is obtained by putting the heater at different positions of the tank. The water vibration is produced by a heavy force, and the turbid medium is obtained by dissolving very small specks of CaCO<jats:sub>3</jats:sub> in the water. A set of Hadamard speckle pattern pairs are generated and modulated on the incident beam, and then the beam illuminates on an unknown object after passing through the simulated underwater environment. With the second-order correlations, the image is reconstructed under different temperature gradients, water vibration, and turbid medium ratios. The results show that GI has the turbulence-free ability under lower temperature gradient, water vibration, and turbid media. The structural similarity image measurement (SSIM) values of the reconstructed images only start to decrease when the temperature gradient is greater than 4.0 °C. The same temperature gradient produced at the different positions has a little effect on the quality of the underwater GI.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We propose a simple and efficient method that uses a single focused hybrid vector beam to confine metallic Rayleigh particles at multiple positions. We study the force mechanisms of multiple trapping by analyzing the gradient and scattering forces. It is observed that the wavelength and topological charges of the hybrid vector beam regulate the trapping positions and number of optical trap sites. The proposed method can be implemented easily in three-dimensional space, and it facilitates both trapping and organization of particles. Thus, it can provide an effective and controllable means for nanoparticle manipulation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>CsPbBr<jats:sub>3</jats:sub> nanocrystal is used as the saturable absorber (SA) for mode-locking Tm-doped fiber laser in a ring fiber cavity. The modulation depth, saturable intensity, and non-saturable loss of the fabricated SA are 14.1%, 2.5 MW/cm<jats:sup>2</jats:sup>, and 5.9%, respectively. In the mode-locking operation, the mode-locked pulse train has a repetition rate of 16.6 MHz with pulse width of 24.2 ps. The laser wavelength is centered at 1992.9 nm with 3-dB spectrum width of 2.5 nm. The maximum output power is 110 mW with slope efficiency of 7.1%. Our experiment shows that CsPbBr<jats:sub>3</jats:sub> nanocrystal can be used as an efficient SA in the 2-<jats:inline-formula> <jats:tex-math> <?CDATA ${\rm{\mu }}{\rm{m}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_094203_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> wavelength region.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We demonstrated a continuous wave (cw) single-frequency intracavity frequency-doubled Nd:YVO<jats:sub>4</jats:sub>/LBO laser with 532 nm output of 7.5 W and <jats:inline-formula> <jats:tex-math> <?CDATA $1.06\,{\rm{\mu }}{\rm{m}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>1.06</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_094204_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula> output of 3.1 W, and low intensity noise in audio frequency region. To suppress the intensity noise of the high power 532 nm laser, a laser frequency locking system and a feedback loop based on a Mach–Zehnder interferometer were designed and used. The influences of the frequency stabilization and the crucial parameters of the MZI, such as the power splitting ratio of the beam splitters and the locking state of the MZI, on the intensity noise of the 532 nm laser were investigated in detail. After the experimental optimizations, the laser intensity noise in the frequency region from 0.4 kHz to 10 kHz was significantly suppressed.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We presented a passively <jats:italic>Q</jats:italic>-switched (PQS) diode-pumped <jats:italic>c</jats:italic>-cut Tm, Ho:LuVO<jats:sub>4</jats:sub> laser with a black phosphorus saturable absorber for the first time. Under PQS mode, an average output power of 0.86 W and a peak power of 2.32 W were acquired from the Tm, Ho:LuVO<jats:sub>4</jats:sub> laser with the pump power of 14.55 W, corresponding to a pulse width of <jats:inline-formula> <jats:tex-math><?CDATA $2.89\,{\rm{\mu }}{\rm{s}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>2.89</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">s</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_094205_ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>, a pulse repetition rate of 71.84 kHz, and a pulse energy of about <jats:inline-formula> <jats:tex-math><?CDATA $6.70\,{\rm{\mu }}{\rm{J}}$?></jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6.70</mml:mn> <mml:mspace width="0.50em" /> <mml:mi mathvariant="normal">μ</mml:mi> <mml:mi mathvariant="normal">J</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_28_9_094205_ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>The acetic acid–water binary system is a classical hydroxy–carboxy mixed system, while new and interesting phenomena appear under stimulated Raman scattering (SRS). Compared with the weaker signal of the acetic acid–water binary system obtained in spontaneous Raman scattering, SRS provides a finer band and a relatively distinct structural transition point. The structural transformation points are respectively at 30% and 80% by volume ratio under the condition of spontaneous Raman spectroscopy, while they are respectively at 15% and 25% under the condition of SRS. This phenomenon is attributed to the generation of laser induced plasma and shockwave induced dynamic high pressure environment during SRS.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>We propose a novel kind of wide-range refractive index optical sensor based on photonic crystal fiber (PCF) covered with nano-ring gold film. The refractive index sensing performance of the PCF sensor is analyzed and simulated by the finite element method (FEM). The refractive index liquid is infiltrated into the cladding air hole of the PCF. By comparing the sensing performance of two kinds of photonic crystal fiber structures, a wide range and high sensitivity structure is optimized. The surface plasmon resonance (SPR) excitation material is chose as gold, and large gold nanorings are embedded around the first cladding air hole of the PCF. The higher order surface plasmon modes are generated in this designed optical fiber structure. The resonance coupling between the fundamental mode and the 5th order surface plasmon polariton (SPP) modes is excited when the phase matching condition is matched. Therefore, the 3rd loss peaks appear obvious red-shift with the increase of the analyte refractive index, which shows a remarkable polynomial fitting law. The fitnesses of two structures are 0.99 and 0.98, respectively. When the range of refractive indices is from 1.40 to 1.43, the two kinds of sensors have high linear sensitivities of 1604 nm/RIU and 3978 nm/RIU, respectively.</jats:p>