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A stable, efficient, and powerful 1314 nm Nd:YLF laser inband-pumped by a wavelength-locked narrowband 880 nm laser diode is demonstrated. The influence of mode-to-pump ratio on the performance of the diode-end-pumped Nd:YLF laser has been systematically investigated by taking into account the thermal effect and the energy transfer upconversion effect. For the optimum mode-to-pump ratio of 0.84, the maximum continuous wave output power of 21.9 W was extracted under the pump power of 70 W, which corresponded to the optical power efficiency of 31.3% and the beam quality of M2 ≈ 1.6. The resultant output power stability was determined to be 0.059% (RMS) within 1 h. In addition, by increasing the mode-to-pump ratio to 1.0, the near-diffraction-limited beam (M2 ≈ 1.3) was achieved with the output power of 17.0 W and the optical power efficiency of 24.3%.

We demonstrate the first multi-segmented Nd:YLF laser, to the best of our knowledge. The multi-segmented crystal was designed to straightforwardly aim for the minimum thermal stress without sacrificing the overall laser efficiency, with the influence of the pump beam waist position considered in particular. Integrating the enhanced thermo-mechanical resistance of multi-segmented crystal and the alleviated heat load of low quantum defect pumping, this end-pumped 1314 nm Nd:YLF laser system delivered a maximum continuous-wave output power of up to 35.5 W under a pump power of 105 W, corresponding to an optical-to-optical efficiency of 33.8%. Furthermore, by incorporating an acousto-optic modulator, an active Q-switching oscillator was accomplished, yielding a maximum average output power of 22.9 W at a pulse repetition frequency (PRF) of 20 kHz and a largest pulse energy of 13.6 mJ at a PRF of 1 kHz.

Multi-physics coupling, composed of an intense THz laser and electric field, serves as a new approach to realize the ultrahigh-level enhancement on third-harmonic generation (THG) of cubic quantum dots (CQDs). The exchange of quantum states caused by anticrossing of intersubbands is demonstrated by the Floquet method and finite difference method with the increasing laser-dressed parameter and electric field. The results show that the rearrangement of the quantum states excites the THG coefficient of CQDs four orders of magnitude higher than that achieved with a single physical field. The optimal polarization direction of incident light that maximizes the THG exhibits strong stability along the z axis at high laser-dressed parameter and electric field.

We demonstrated an eye-safe diamond Raman laser intra-cavity pumped by the 1.3 μm fundamental field for the first time, to the best of our knowledge. The first-Stokes laser at 1634 nm was converted from the 1342 nm fundamental laser, which was produced by an in-band pumped double-end diffusion-bonded a-cut Nd:YVO4 crystal. Under an incident pump power of 21.2 W and an optimal pulse repetition frequency of 25 kHz, the maximum average output power of 2.0 W was obtained with the pulse duration of 5.7 ns and the peak power of 14 kW. The first-Stokes emission was found to be near diffraction limited (M2 ≈ 1.3) and to have a narrow linewidth (∼0.05 nm FWHM; instrument limited).

An efficient high-power nanosecond pulsed deep-red laser at 745 nm is produced by intracavity frequency-doubling an acousto-optically Q switched Nd:YLF/KGW Raman laser using a lithium triborate (LBO) crystal. The critically phase-matched type-I LBO crystal with an optimized length of 25 mm is adopted to enable efficient second-harmonic generation and to suppress unwanted cascaded Stokes fields. Under a repetition rate of 4 kHz, the maximum average output power of 4.1 W is obtained with the launched pump power of 50 W, resulting in an overall optical power conversion efficiency of 8.2%. The average beam quality factor is determined to be M2 = 1.46. The pulse energy is scaled up to 3.3 mJ at the repetition rate of 1 kHz, corresponding to a pulse width of 4.2 ns and a peak power of up to 0.8 MW. Moreover, we theoretically investigate the dependence of the conversion efficiency on the walk-off angle as well as the fundamental and first-Stokes losses, which will guide further optimization of experimental devices.

We demonstrated a deep-red laser source by intracavity frequency-doubled crystalline Raman laser for the first time, to the best of our knowledge. The actively Q -switched 1314 nm N d : L i Y F 4 laser was first converted to the eye-safe Raman laser using a K G d ( W O 4 ) 2 (KGW) crystal, which was subsequently frequency-doubled in a bismuth borate crystal. Benefiting from the KGW bi-axial properties, the deep-red laser source was able to lase separately at two different spectral lines at 730 and 745 nm. Under an optimal repetition rate of 4 kHz, the maximum average powers of 1.7 and 2.0 W were attained with good beam quality of M 2 ≈ 1.7 . The corresponding pulse durations were determined to be 3.0 and 2.8 ns with the peak powers up to approximately 140 and 180 kW, respectively.

The electronic state and nonlinear optical properties in the Y-shaped quantum dots has been theoretically investigated by adjusting the shape with the applied electric field. Within the effective-mass approximation, the energy levels and the wave functions of the system are obtained by means of the finite difference method. The results show that both the strength or the in-plane orientation of external electric field and the shape of regulable Y-shaped quantum dots have a significant influence on the electronic state, optical absorption coefficients and the refractive index changes.

A transparent Tm:Lu

Based on stochastic discount factor theory, this paper proposes a method to convert the traditional systemic risk measures of financial markets, such as VaR, ES, MES and SES, into risk-neutral measures. We proposed a novel way to neutralize the returns without relying on option price information. Then, we empirically analyzed and compared the systemic risks and changes between the A-shares in Shanghai and H-shares in Hong Kong before and after a stock market crash, and we found that systematic risk measures under risk neutrality could more accurately determine market system risks than traditional systemic risk measures. Moreover, these systemic risk measures have a certain market risk warning effect.

An actively Q-switched eye-safe orthogonally-polarized dual-wavelength intracavity Raman laser was demonstrated for the first time, to the best of our knowledge. The gain balanced dual-wavelength operation at 1314 and 1321 nm within an in-band pumped Nd:YLF laser was realized by slightly titling the cavity mirrors. Owing to the KGW bi-axial properties, two sets of simultaneous orthogonally-polarized dual-wavelength Raman lasers at 1470, 1490 nm and 1461, 1499 nm were achieved by simply rotating the KGW crystal for 90°, respectively. With an incident pump power of 30 W and an optimized pulse repetition frequency of 5 kHz, the maximum dual-wavelength Raman output powers of 2.6 and 2.4 W were obtained with the pulse widths of 5.8 and 6.3 ns, respectively, corresponding to the peak powers up to 89.7 and 76.5 kW.

We demonstrate the first nanosecond pulsed single longitudinal mode (SLM) intracavity-pumped diamond Raman laser, to the best of our knowledge. The eye-safe coherent source at 1634 nm, which was converted from the actively Q-switched 1342 nm Nd:YVO4 laser, yielded 4.35 W of multimode average output power with a pulse duration of 6 ns and peak power of 29 kW. By exploiting the spatial hole burning free gain mechanism in the Raman media, stable SLM operation was observed at low output power (0.46 W) for the free-running case. Furthermore, by incorporating an etalon in the fundamental standing-wave cavity, the spectral linewidth of the fundamental field was suppressed substantially below the diamond Raman gain linewidth and slightly less than the free spectral range of the mm-scale Raman resonator. Thereby, a much higher SLM output power of 1.63 W was obtained with a pulse duration of ∼9 ns and a spectral linewidth of ∼77 MHz.

A new approach for controlling intersubband transitions and optical properties of coaxial cylindrical quantum well is proposed. Considering the correct dressing effect for the confinement potential, the new ultra-wide tuning mechanism is based on the variation of quasibound states with the intensity of long-wavelength laser field. By means of the finite difference method, the results provide a new explanation for the anticrossing of energy levels and exhibit great potential for ultra-wide frequency tunability (ranging from terahertz to the mid-infrared region) of the optical absorption coefficient and refractive index changes by modulating the laser parameters and barrier thickness.

Tm3+-doped cubic potassium yttrium fluoride, KY3F10, is a promising laser crystal for efficient watt-level lasers at ∼1.9 μm because of the relatively easy crystal growth by the Czochralski method, advantageous thermo-optical properties, high available Tm3+ doping levels and very efficient cross-relaxation mechanism. A compact diode-pumped 8 at.% Tm3+:KY3F10 laser generated 1.85 W at 1891 nm with a slope efficiency of 65.2% and a laser threshold of 450 mW. A negative thermal lens was detected in this crystal owing to the negative dn/dT coefficient (−8.9 × 10−6 K−1). Passive Q-switching of the Tm3+:KY3F10 laser by single-walled carbon nanotube saturable absorber was demonstrated yielding 13.2 μJ/490 ns pulses at a repetition rate of 58 kHz.

A transparent Tm:Lu3Al5O12 ceramic is fabricated by solid-state reactive sintering at 1830 °C for 30 h using commercial α-Al2O3 and Lu2O3/Tm2O3 powders and sintering aids - MgO and TEOS. The ceramic belongs to the cubic system and exhibits a close-packed structure (mean grain size: 21 µm). The in-line transmission at ∼1 µm is 82.6%, close to the theoretical limit. The spectroscopic properties of the ceramic are studied in detail. The maximum stimulated-emission cross-section is 2.37×10−21 cm2 at 1749nm and the radiative lifetime of the 3F4 state is about 10 ms. The modified Judd-Ofelt theory accounting for configuration interaction is applied to determine the transition probabilities of Tm3+, yielding the intensity parameters Ω2 = 2.507, Ω4 = 1.236, Ω6 = 1.340 [10−20 cm2] and α = 0.196×10−4 cm. The effect of excited configurations on lower-lying interconnected states with the same J quantum number is discussed. First laser operation is achieved under diode-pumping at 792 nm. A 4 at.% Tm:Lu3Al5O12 ceramic laser generated 3.12 W at 2022-2035nm with a slope efficiency of 60.2%. The ceramic is promising for multi-watt lasers at >2 µm.

Monoclinic (wolframite-type) monotungstate crystals are promising for rare-earth doping. We report polarized room- and low-temperature spectroscopy and efficient high-power laser operation of such a Y b 3 + : M g W O 4 crystal featuring high stimulated emission cross section ( σ S E = 6 . 2 × 10 − 20 c m 2 at 1056.7 nm for light polarization E | | N m ), large Stark splitting of the ground state ( 765 c m − 1 ), large gain bandwidth (26.1 nm for E | | N g ), and strong Raman response (most intense mode at 916 c m − 1 ). A diode-pumped Y b 3 + : M g W O 4 laser generated 18.2 W at ∼ 1056 n m with a slope efficiency of ∼ 89 % and a linearly polarized laser output.

In this Letter, the frequency expansion of an orthogonally polarized dual-wavelength laser, based on the cascaded stimulated Raman scattering, was demonstrated for the first time, to the best of our knowledge. The dual-wavelength fundamental laser generated from two separate Nd:YLF crystals was free of gain competition. Integrating the benefit of the two different orthogonally polarized Raman gain peaks in the KGd(WO4)2 (KGW) crystal, two sets of first-Stokes orthogonally polarized dual-wavelength Raman lasers were first achieved by rotating the Raman crystal for 90°. Furthermore, by simply replacing the Raman output coupler, we attained another two sets of second-Stokes orthogonally polarized dual-wavelength Raman lasers via the cascaded Raman shift. At a pulse repetition frequency of 5 kHz, the maximum first-Stokes and second-Stokes dual-wavelength Raman output powers were 3.12 and 2.09 W, with the combined peak powers of approximately 240 and 290 kW, respectively.

We report on a passively Q-switched (PQS) yellow laser emitting at 589 nm by using type-I noncritical phase-matching LBO crystal intracavity frequency-doubled self-Raman laser. A 30-mm-length c-cut YVO4/Nd:YVO4/YVO4 composite crystal was employed to accelerate heat spread as well as enhance the Raman conversion efficiency. By using a Cr4+:YAG composite crystal with the initial transmission of 83%, a yellow emission with 660 mW average output power was obtained under the absorbed pump power of 17.5 W, corresponding to the diode-to-yellow conversion efficiency of 3.8% and slope efficiency of 8.1%, respectively. The pulse repetition frequency and pulse duration were measured to be 16 kHz and 2.8 ns, respectively, corresponding to the pulse energy of 41.3 μJ and peak power of 14.7 kW. To the best of our knowledge, this is the highest power of PQS yellow laser via intracavity frequency-doubled self-Raman laser.

A single-longitudinal-mode crystalline Raman laser in the 1.7 µm wave band was reported for the first time, to the best of our knowledge. The Y V O 4 Raman laser, which was intracavity-pumped by an actively Q -switched 1314 nm Nd:YLF laser, demonstrated the cascaded Stokes oscillation at 1715 nm. By inserting an etalon in the fundamental resonator, linewidth narrowing and power scaling of the second-Stokes laser were realized based on the spatial-hole-burning-free Raman gain. With an optimal pulse repetition frequency of 4 kHz, the maximum single-longitudinal-mode average output power of 1.8 W was acquired with the spectrum linewidth of ∼ 340 M H z . Further increasing the incident pump power, the second-Stokes laser transitioned to multimode regime, and the maximum average output power reached 2.7 W with the peak power as high as ∼ 380 k W .

We demonstrated a narrowband eye-safe intracavity Raman laser by incorporating a fused silica etalon into the fundamental resonator. The KGd(WO4)2 (KGW) Raman laser was pumped by an actively Q-switched Nd:YLF laser at 1314 nm. Thanks to the KGW bi-axial properties, two distinct eye-safe Raman lasers operating at 1461 and 1490 nm were obtained separately by rotation of the KGW crystal. At an optimized pulse repetition frequency of 4 kHz, the maximum average output powers of 3.6 and 4.0 W were achieved with the peak powers up to approximately 330 and 480 kW, respectively. The eye-safe Stokes emissions were narrow linewidth (∼0.05 nm FWHM; measurement limited) and near diffraction limited (M 2

Monoclinic 1.25 at.% Yb3+:MgWO4 crystals are grown by the Top-Seeded-Solution-Growth method and their room- and low-temperature spectroscopy is studied. A diode-pumped Yb3+:MgWO4 laser generates 18.2 W at ~1056 nm with a slope efficiency of ~89%.

We report on the frequency expansion of efficient passively Q-switched (PQS) orthogonally-polarized dual-wavelength laser for the first time, to our knowledge. The dynamic of pulse synchronization for the PQS dual-wavelength laser was analyzed theoretically. With two Nd:YLF crystals, the simultaneous PQS orthogonally-polarized dual-wavelength laser at 1047 and 1053 nm was obtained with the maximum output powers of 4.5 and 4.2 W, respectively, resulting in a total optical-to-optical conversion efficiency of 18.7%. The timing jitter between the 1047 nm main pulse and 1053 nm main pulse was 26.6 ns. Furthermore, substituting one of the Nd:YLF crystals for a Nd:YAG crystal, two sets of simultaneous orthogonally-polarized dual-wavelength lasers at 1047, 1064 nm and 1053, 1064 nm were generated with near 6 W of output power.

We report a high average power actively Q-switched (AQS) orthogonal polarization dual-wavelength Nd:YLF laser at 1047 and 1053 nm. The gain-to-loss balance of dual wavelengths was realized via an uncoated quartz etalon. A maximum continuous wave (CW) output power of 14.2 W was obtained under the incident pump power of 41.7 W, corresponding to an optical-to-optical conversion efficiency of 34.1% and a slope efficiency of 38.3%. Active Q-switching was accomplished by inserting an acousto-optic modulator in the cavity. Under the incident pump power of 40 W, this setup delivered a maximum average output power of 10 W at the pulse repetition frequency (PRF) of 30 kHz and the largest pulse energy of 3.4 mJ at the PRF of 1 kHz, respectively. To the best of our knowledge, these are the highest average output powers for both CW and AQS orthogonally polarized dual-wavelength lasers based on laser crystals.

We demonstrate an 806 nm laser diode end-pumped continuous-wave (CW) and actively Q-switched (AQS) orthogonally-polarized dual-wavelength Nd:YLF laser operating at 1314 and 1321 nm. Benefitting from the small difference of the stimulated emission cross sections at 1314 and 1321 nm in Nd:YLF crystal, the power equalized emissions at both wavelengths were achieved by simply titling the output coupler. A maximum CW output power of 9.2 W was obtained with the incident pump power of 32.5 W, giving an optical-to-optical conversion efficiency of approximately 28% and a slope efficiency of approximately 33%. Furthermore, active Q-switching was realized by inserting a Brewster-cut acousto optic modulator. For an incident pump power of 30 W, this oscillator delivered an average power of 6.5 W at a pulse repetition frequency (PRF) of 20 kHz, and a pulse energy of 2.6 mJ with a peak power of approximately 72 kW at a PRF of 1 kHz.

An in-band pumped passively Q-switched (PQS) self-Raman laser with a c-cut Nd:YVO4 composite crystal is demonstrated for the first time to our knowledge. A Cr4+:YAG composite crystal was utilized to improve the stability and misalignment sensitivity of the resonator. The PQS self-Raman output performance was systematically investigated with different initial transmissions (T0) of the Cr4+:YAG and different transmissions (TS) of the Raman output coupler. In addition, the focus position of the incident pump beam and cavity length have been optimized during the experiment. With Cr4+:YAG of T0=90% and output coupler of TS=10%, the maximum average output power at 1178 nm was up to 2.53 W under the absorbed pump power of 20.6 W, corresponding to an optical-to-optical conversion efficiency of 12.3%. The pulse repetition frequency and pulse width were measured to be 39.1 kHz and 20.4 ns, respectively, and the corresponding pulse energy and peak power were calculated to be 64.7 μJ and 3.2 kW. At the full output power, the fluctuation of Raman output power was less than ±0.5% within one hour. To the best of our knowledge, we have improved the PQS self-Raman laser about 3.2 times.

We originally proposed a method for obtaining an orthogonally polarized dual-wavelength Raman laser via a polarized-dependent effect of Raman shifting. Pumping a-cut YVO4 crystal with a passively Q-switched Nd:YAG laser, the system not only emitted a conventional Raman emission at 1175.4 nm but also a Raman emission at 1165.2 nm, which originated from the Raman shifts of 890 cm−1 and 816 cm−1, respectively. The polarization directions of the emissions at 1175.4 nm and 1165.2 nm were found to be along the c-axis and b-axis of the YVO4 crystal respectively, which enabled the orthogonally polarized operation. With a type-II KTP crystal, their sum-frequency generation (SFG) was obtained for the first time, and this result proved that the pulse series of these two emissions were simultaneous.