Generation of elliptical isolated attosecond pulse from oriented H_(2)^(+)in a linearly polarized laser field

We investigate the ellipticity of the high-order harmonic generation from the oriented H_(2)^(+)exposed to a linearly polarized laser field by numerically solving the two-dimensional time-dependent Schrodinger equation(2 D TDSE).Numerical simulations show that the harmonic ellipticity is remarkably sensitive to the alignment angle.The harmonic spectrum is highly elliptically polarized at a specific alignment angleθ=30°,which is insensitive to the variation of the laser parameters.The position of the harmonic intensity minima indicates the high ellipticity,which can be attributed to the two-center interference effect.The high ellipticity can be explained by the phase difference of the harmonics.This result facilitates the synthesis of a highly elliptical isolated attosecond pulse with duration down to 65 as,which can be served as a powerful tool to explore the ultrafast dynamics of molecules and study chiral light-matter interaction.

Dynamic study of compressed electron layer driven by linearly polarized laser

The dynamics of the compressed electron layer（CEL） are investigated when a linearly polarized（LP） laser pulse irradiates a plasma target. The turbulent motion of the CEL is investigated by a simple model, which is verified by particlein-cell（PIC） simulations. It is found that the compressed layer disperses in a few cycles of the laser duration, because the CEL comes back with a large velocity in the opposite direction of the laser incident. A larger wavelength laser can be used to tailor the proton beam by reducing the turbulence of the CEL in the region of the LP laser acceleration.

Correlation between the magic wavelengths and the polarization direction of the linearly polarized laser in the Ca^+ optical clock

The magic wavelengths for different Zeeman components are measured based on the ^40Ca^＋ optical clock. The dynamic dipole polarizability of a non-zero angular moment level has correlation with the polarization direction of the linearly polarized laser beam, and we show that the four hyperfine structure levels of 4S1/2,m=±1/2 and 3d5/2,m=±1/2 for ^40Ca^＋ have the same dynamic dipole polarizability at the magic wavelength and a certain polarization direction. In addition, the existence of a specific direction of polarization may provide a new idea for improving the precision of magic wavelength measurement in experiment.

A novel orthogonally linearly polarized Nd:YVO_4 laser

We presented a novel orthogonally linearly polarized Nd：YVO4 laser. Two pieces of a-cut grown-together composite YVO4/Nd：YVO4 crystals were placed in the resonant cavity with the c-axis of the two crystals orthogonally. The polarization and power performance of the orthogonally polarized laser were investigated. A 26.2-W orthogonally linearly polarized laser was obtained. The power ratio between the two orthogonally polarized lasers was varied with the pump power caused by the polarized mode coupling. The longitudinal modes competition and the corresponding variable optical beats were also observed from the orthogonally polarized laser. We also adjusted the crystals with their c-axis parallele to each other, and a 40.7-W linearly polarized TEM00 laser was obtained, and the beam quality factors were Mx^2 = 1.37 and My^2 = 1.25.

A Single-Frequency Linearly Polarized Fiber Laser Using a Newly Developed Heavily Tm3+-Doped Germanate Glass Fiber at 1.95 μm

A compact linearly polarized, low-noise, narrow-linewidth, single-frequency fiber laser at 1950nm is demonstrated. This compact fiber laser is based on a 21-mm-long homemade Tm3＋-doped germanate glass fiber. Over 100-mW stable continuous-wave single transverse and longitudinal mode lasing at 195Ohm are achieved. The measured relative intensity noise is less than -135dB/Hz at frequencies over 5 MHz. The signal-to-noise ratio of the laser is larger than 72dB, and the laser linewidth is less than 6kHz, while the obtained linear polarization extinction ratio is higher than 22 dB.

A Linearly Polarized Ho:YAG Laser at 2.09 μm with Corner Cube Cavity Pumped by Tm:YLF Laser

A linearly polarized operation Ho： YAG laser at 2090.5 nm with a corner cube cavity is demonstrated. A polarizer with high reflectivity for the s-polarized light at the laser wavelength is employed to achieve a linearly polarized laser. In the same case of resonator length, the corner cube can be used to cut the volume of the Ho：YAG laser and to enhance the stability of the system. The maximum linearly polarized output power of 5.8 W is achieved at the absorbed pump power of 23.3 W, corresponding to a slope efficiency of 29.7%, and the optical-optical conversion efficiency is around 24.9%. The M2 factors of the 2.09μm laser are 2.4 and 1.2 along the horizontal and vertical directions, respectively.

High-power all-fiber linearly polarized Yb-doped chirped pulse amplifier based on active polarization control

High-power ultrafast laser amplification based on a non-polarization maintaining fiber chirped pulse amplifier is demonstrated.The active polarization control technology based on the root-mean-square propagation(RMS-prop)algorithm is employed to guarantee a linearly polarized output from the system.A maximum output power of 402.3 W at a repetition rate of 80 MHz is realized with a polarization extinction ratio(PER)of>11.4 dB.In addition,the reliable operation of the system is verified by examining the stability and noise properties of the amplified laser.The M2factor of the laser beam at the highest output power is measured to be less than 1.15,indicating a diffraction-limited beam quality.Finally,the amplified laser pulse is temporally compressed to 755 fs with a highest average power of 273.8 W.This is the first time,to the best of our knowledge,that the active polarization control technology was introduced into the high-power ultrafast fiber amplifier.

Near-diffraction-limited linearly polarized narrow-linewidth random fiber laser with record kilowatt output

In this paper, we propose and experimentally investigate a linearly polarized narrow-linewidth random fiber laser(RFL) operating at 1080 nm and boost the output power to kilowatt level with near-diffraction-limited beam quality using a master oscillation power amplifier. The RFL based on a half-opened cavity, which is composed of a linearly polarized narrow-linewidth fiber Bragg grating and a 500 m piece of polarization-maintained Ge-doped fiber, generates a 0.71 W seed laser with an 88 pm full width at half-maximum(FWHM) linewidth and a 22.5 dB polarization extinction ratio(PER) for power scaling. A two-stage fiber amplifier enhances the seed laser to the maximal 1.01 k W with a PER value of 17 dB and a beam quality of M_x^2=1.15 and M_y^2=1.13. No stimulated Brillouin scattering effect is observed at the ultimate power level, and the FWHM linewidth of the amplified random laser broadens linearly as a function of the output power with a coefficient of about 0.1237 pm∕W.To the best of our knowledge, this is the first demonstration of a linearly polarized narrow-linewidth RFL with even kilowatt-level near-diffraction-limited output, and further performance scaling is ongoing.

Hundred-watt-level linearly polarized tunable Raman random fiber laser

A high power linearly polarized tunable Raman random fiber laser（RFL） was studied theoretically and experimentally. The parameters required for the system design were obtained through numerical simulation, based on which a hundred-watt-level linearly polarized tunable RFL was successfully demonstrated. The central wavelength can be continuously tuned from 1113.76 to 1137.44 nm, and the output power exceeds 100 W for all of the lasing wavelengths with the polarization extinction ratio（PER） exceeding 20 d B at the maximum output power.Besides, the linewidth, spectral evolution, and temporal dynamics of a specified wavelength（1124.72 nm） were investigated in detail. Moreover, the theoretical results and the experimental results fit well. To the best of our knowledge, this is the first time for a hundred-watt-level linearly polarized tunable RFL ever reported.

Investigation on extreme frequency shift in silica fiber-based high-power Raman fiber laser

In this paper, we experimentally investigated the extreme frequency shift in high-power Raman fiber laser(RFL). The RFL was developed by using a pair of fiber Bragg gratings with fixed and matched central wavelength(1120 nm)combined with a piece of 31-m-long polarization maintaining(PM) passive fiber adopted as Raman gain medium.The pump source was a homemade high-power, linearly polarized(LP) wavelength-tunable master oscillator power amplifier(MOPA) source with ～25 nm tunable working range(1055–1080 nm). High-power and high-efficiency RFL with extreme frequency shift between the pump and Stokes light was explored. It is found that frequency shift located within 10.6 THz and 15.2 THz can ensure efficient Raman lasing, where the conversion efficiency is more than 95% of the maximal value, 71.3%. In addition, a maximum output power of 147.1 W was obtained with an optical efficiency of71.3%, which is the highest power ever reported in LP RFLs to the best of our knowledge.