ABSTRACT
A 253 J with 26â ns at 0.2â Hz laser performance was demonstrated using a LD pumped cryogenically cooled Yb:YAG ceramics laser amplifier. A high energy storage of 344 J was achieved with a stored energy density of 0.58 J/cm3 using a 1 kJ output multidirectional-pumping system. High energy-extraction efficiency of 56.5% was achieved with high energy fluence of 4.63 J /cm2. To the best of our knowledge, this is the highest output energy obtained with a repetitive nanosecond pulse by LD pumped solid-state laser. This paper presented a design of 1 kJ amplifier based on experimentally proven numerical data.
ABSTRACT
Er3+/Dy3+ co-doped double-clad ZBLAN optical fiber has been used to obtain amplified spontaneous emission (ASE) broadband light sources cladding-pumped by 980-nm multimode laser diode (LD) sources. It has been demonstrated that mid-infrared broadband emission extending from 2515 to 3735 nm was obtained by energy transfer between Er3+ and Dy3+. We experimentally investigated the optimum design of Er3+/Dy3+ co-doped ZBLAN fiber in terms of ion concentration, fiber length, pumping configuration, and pumping power. The ASE output power was more than 2.5 mW when the LD pump power was set at 5 W. To assess its potential for gas sensing applications, the fabricated ASE light source was used to successfully detect methane gas with concentrations at 1% and 5%. The simple and stable construction of our ASE light source is suitable for practical purposes.
ABSTRACT
We report, to the best of our knowledge, the highest power conductive-cooled active-mirror amplifier (CcAMA) using Yb:YAG with a pulse energy of 10 J. By using four liquid-nitrogen circulating cooled laser heads, we achieved a repetition rate, pulse energy, and average power of 33.3 Hz, 9.3 J, and 310 W, respectively. The problem of wavefront distortion, which is difficult to solve with a large-aperture active-mirror laser, is suppressed by using reinforcing materials with the same thermal expansion coefficient. We have confirmed that the wavefront distortion is small (0.15λ P-V per head) at 100 Hz operation, which paves the way for 100 Hz operation with the CcAMA concept.
ABSTRACT
An actively Q-switched mid-infrared Fe:ZnSe laser pumped by a continuous wave fluoride fiber laser has been developed. Stable operation with a pulse duration of 20 ns and a repetition rate of 40 kHz at 4 µm was achieved. The maximum peak power was 1.1 kW. The high-repetition rate, high-peak power nanosecond pulsed laser, which has been created for the first time, to the best of our knowledge, in an actively Q-switched Fe:ZnSe laser, should prove a suitable light source for laser processing and molecular sensing.
ABSTRACT
Fast isochoric laser heating is a scheme to heat matter with a relativistic intensity (>10^{18} W/cm^{2}) laser pulse for producing an ultrahigh-energy-density (UHED) state. We have demonstrated an efficient fast isochoric heating of a compressed dense plasma core with a multipicosecond kilojoule-class petawatt laser and an assistance of externally applied kilotesla magnetic fields for guiding fast electrons to the dense plasma. A UHED state of 2.2 PPa is achieved experimentally with 4.6 kJ of total laser energy that is one order of magnitude lower than the energy used in the conventional implosion scheme. A two-dimensional particle-in-cell simulation confirmed that diffusive heating from a laser-plasma interaction zone to the dense plasma plays an essential role to the efficient creation of the UHED state.
ABSTRACT
A fluoride-fiber-based master oscillator power amplifier (MOPA) for 30-W class continuous-wave (cw) operation at 2.8-µm wavelength has been demonstrated. To overcome the low durability of ZBLAN fibers, various novel technologies for using fluoride glass with a ZBLAN-fiber-based side-pump combiner have been adopted in the system. A maximum cw output power of 33 W and stable operation under 23-W output have been demonstrated. We suggest that such fiber MOPA systems will open up advanced fluoride fiber technology for next-generation high-power mid-IR lasers.
ABSTRACT
A method of 2-dimensional (2-D) space-scanned (in the x-y plane) spatiotemporal double-slit interference is used to reconstruct the 2-D pulse-front (in the x-y-t domain) of a femtosecond pulsed beam. While comparing with recent other methods, the method possesses two advantages: no reference pulse/beam is required anymore, and an arbitrarily distorted pulse-front, not just pulse-front tilt and pulse-front curvature, could be detected. Meanwhile, the influence of different factors of unknown pulsed beams and optical elements on the measurement reliability is also analyzed for engineering applications.
ABSTRACT
The prospect for developing a passively Q-switched Yb:YAG/Cr:YAG monolithic microchip laser that operates at cryogenic temperature is theoretically analyzed. It is concluded that such a system has the potential to deliver laser pulses with improved energy and increased peak power in comparison with composite Yb:YAG/Cr:YAG or Nd:YAG/Cr:YAG devices that are operated at room temperature. Consequently, a cryogenically cooled Yb:YAG/Cr:YAG system is built and the emission performances are investigated. Laser pulses with 3.2 mJ energy, 6.1 MW peak power and high beam quality of M2 = 1.8 are achieved. By increasing the pump beam diameter, laser pulses with higher energy 32 mJ are obtained at 25 MW peak power with M2 = 5.4. To our knowledge, these are the best results obtained from passively Q-switched composite Yb:YAG/Cr:YAG monolithic microchip lasers.
ABSTRACT
Comparing with the non-collinear optical parametric amplification (NOPA), the gain bandwidth could be significantly enhanced by the wide-angle NOPA (WNOPA), i.e., with a divergent signal (WNOPA-S) or pump (WNOPA-P). In a uniaxial crystal, the spectral symmetry/asymmetry of WNOPA is introduced. In WNOPA-S, the ultra-broadband gain spectrum can be obtained in two phase-matching directions at both sides of the pump, however, the output is heavily angularly dispersed. In WNOPA-P, although the gain bandwidth enhancement is only achieved in one phase-matching direction, i.e., on the opposite side of the crystal axis, it is free of angular dispersion. The stabilities of the gain spectrum in NOPA and in WNOPA-P are experimentally compared and theoretically analyzed. Compared with NOPA, WNOPA-P supports an even broader and more stable gain spectrum, and compared with WNOPA-S, WNOPA-P is angular-dispersion-free. The conversation efficiency of WNOPA-P is the same as NOPA. We suppose WNOPA-P is ideally suitable for the amplification of stable ultra-broadband few-cycle pulse lasers.
ABSTRACT
Fast isochoric heating of a pre-compressed plasma core with a high-intensity short-pulse laser is an attractive and alternative approach to create ultra-high-energy-density states like those found in inertial confinement fusion (ICF) ignition sparks. Laser-produced relativistic electron beam (REB) deposits a part of kinetic energy in the core, and then the heated region becomes the hot spark to trigger the ignition. However, due to the inherent large angular spread of the produced REB, only a small portion of the REB collides with the core. Here, we demonstrate a factor-of-two enhancement of laser-to-core energy coupling with the magnetized fast isochoric heating. The method employs a magnetic field of hundreds of Tesla that is applied to the transport region from the REB generation zone to the core which results in guiding the REB along the magnetic field lines to the core. This scheme may provide more efficient energy coupling compared to the conventional ICF scheme.
ABSTRACT
The passively Q-switched operation of a cryogenically cooled Yb:YAG/Cr:YAG microchip laser was demonstrated with end pumping by a photonic crystal surface emitting laser (PCSEL). This laser generated 70 µJ/1.7 ns/3.2 kHz pulses with near diffraction limited beam quality (M2=1.1) at 1029.4 nm. There were no coupling optics between the microchip laser crystal and PCSEL, which made the system simple and compact.
ABSTRACT
We demonstrate the first actively Q-switched fiber laser operating in the 3.5 µm regime. The dual-wavelength pumped system makes use of an Er3+ doped ZBLAN fiber and a germanium acousto-optic modulator. Robust Q-switching saw a pulse energy of 7.8 µJ achieved at a repetition rate of 15 kHz, corresponding to a peak power of 14.5 W.
ABSTRACT
We have demonstrated that a pulsed electromagnetic wave (Sommerfeld wave) of subterahertz frequency and 11-MV/m field strength can be induced on a metal wire by the interaction of an intense femtosecond laser pule with an adjacent metal foil at a laser intensity of 8.5×10^{18}W/cm^{2}. The polarity of the electric field of this surface wave is opposite to that obtained by the direct interaction of the laser with the wire. Numerical simulations suggest that an electromagnetic wave associated with electron emission from the foil induces the surface wave. A tungsten wire is placed normal to an aluminum foil with a gap so that the wire is not irradiated and damaged by the laser pulse, thus making it possible to generate surface waves on the wire repeatedly.
ABSTRACT
We have developed a quasi-continuous wave diode end-pumped cryogenically cooled Yb:YAG/Cr:YAG passively Q-switched microchip laser. A maximum energy of 12.1 mJ with 3.7 MW of peak power was obtained. To the best of our knowledge, this is the highest energy and peak power obtained by an Yb:YAG/Cr:YAG microchip laser so far.
ABSTRACT
We have demonstrated the continuous-wave operation of a highly efficient 2.8 µm Er-doped Lu2O3 ceramic laser at room temperature. An Er:Lu2O3 ceramic with a doping concentration of 11 at.% afforded a slope efficiency of 29% and an output power of 2.3 W with pumping at 10 W. To our knowledge, these are the highest slope efficiency and output power obtained to date for an Er:Lu2O3 ceramic laser at 2.8 µm. In addition, we prepared ceramics with various doping concentrations and determined their emission cross sections by fluorescence lifetime measurements and emission spectroscopy.
ABSTRACT
We report the femtosecond laser inscription of fiber Bragg gratings (FBGs) in an Er-doped fluoride glass fiber used for lasing at a mid-infrared wavelength of 2.8 µm. The lasing evolution is discussed in terms of the FBG reflectivity, wavelength transition to the Bragg wavelength, and output power of the mid-infrared fiber laser. A first-order and short (2.5-mm-long) Bragg grating showed a reflectivity of 97%, because of a laser-induced index modulation of 1.1 × 10-3. This modulation was sufficient to saturate this system's output power. The laser oscillator is designed to lase in the atmospheric window of 2799-2800 nm slope. Further, this oscillator's efficiency is as high as 29.1% for the launched pump power over the range of 0.4-4.6 W and at a lasing wavelength of 2799.7 nm. This oscillator also exhibited a FWHM bandwidth of 0.12 nm.
ABSTRACT
We have demonstrated a highly efficient 2.8 µm Er-doped Lu2O3 ceramic laser and investigated the lasing dynamics by time-resolved spectroscopy. During room-temperature continuous wave operation, a slope efficiency of 22% was achieved with a high-quality transparent ceramic. To our knowledge, this is the highest slope efficiency obtained by an Er:Lu2O3 ceramic laser. In addition, an output peak power of 1.2 W was obtained during quasi-continuous wave operation. Time-resolved spectroscopy showed that the emission wavelengths exhibited a red shift from 2715 to 2845 nm, which indicated that continuous wave operation may be possible at 2740 and 2845 nm.
ABSTRACT
A simple and compact spectral-broadening system is presented that is based on a single-stage statically pressurized Ar filled hollow core fiber. By optimizing the inner diameter of the hollow core fiber, a bandwidth of 300 nm is obtained. This is the broadest bandwidth known to date with millijoule level energy near the 1-µm wavelength by a single stage gas filled hollow core fiber.
ABSTRACT
Herein, a theory for modeling the problem of scattering pulse-induced temporal contrast degradation in chirped-pulse amplification (CPA) lasers is introduced. Using this model, the temporal evolutions of the scattering and signal pulses were simulated, the temporal contrasts for different cases were compared, and finally the theoretical prediction was verified by an experimental demonstration. The result shows that the picosecond and the nanosecond temporal contrast is mainly determined by the scattering pulses generated in the stretcher and the compressor, respectively. In addition, the B-integral accumulation will further degrade the temporal contrast, especially the picosecond temporal contrast. We believe it is helpful for solving the problem of the picosecond pedestal contrast (i.e., noise limit). With reference to these results, some suggestions for the temporal contrast improvement are presented.
ABSTRACT
The thermally induced depolarization and Verdet constant of CeF3 crystals-their most important characteristics-have been studied in the 79-293 K temperature range. It has been found that thermal effects reduce substantially upon cooling down to 79 K and the Verdet constant grows in inverse proportion to the temperature. It was shown that CeF3 crystals are not inferior to TGG as a medium for Faraday isolators, including cryogenic ones.
