This essential work provides a thorough description of the fundamentals and applications in the field of laser-tissue interactions. Concepts such as the optical and thermal properties of tissue, and ...optical breakdown and its related effects, are treated in detail.
Sesquioxides combine excellent thermomechanical properties, comparably low phonon energies and a strong crystal field, making them ideally suited for broad band emitting high power laser materials in ...the infrared and mid-infrared spectral range. In this paper, the latest progress on diode pumped highly efficient high-power solid-state lasers based on rare-earth doped sesquioxides, Lu 2 O 3 , Sc 2 O 3 , and Y 2 O 3 , as well as different mixed sesquioxides (Lu a Sc b Y c ) 2 O 3 with a + b + c = 1 is reviewed. While Yb 3+ -doped sesquioxides allow for record high efficiencies at several 100 W of output power in continuous wave operation and record high average powers in pulsed mode in the 1-μm spectral range, Tm 3+ - and Ho 3+ -doped sesquioxides enable efficient broad band laser operation and ultrashort pulse duration around 2 μm. Finally, Er 3+ -doped sesquioxides enabled the highest efficiencies and output powers demonstrated so far at room temperature in the mid-infrared range at 3 μm.
Ultrafast lasers operating at high repetition rates, in particular the GHz range, enable new possibilities in laser-material processing, particularly accessing the recently demonstrated ...ablation-cooled regime. We provide a unified perspective of the unique opportunities created by operating at high repetition rates together with our efforts into the development of enabling laser technology, including new results on further scaling up the capabilities of the laser systems. In order to access GHz repetition rates and microjoule-level pulse energies without requiring kilowatts of average power, we implement burst-mode operation. Our results can be grouped into two distinct directions: low- and high-power systems. Pulsed pumping is employed in the later stages of low-power systems, which have low burst repetition rates to achieve high pulse energies, whereas the technique of doping management is developed for the continuously pumped power amplifier stage of high power systems. While most of the developments have been at 1-\mum wavelength range due to the relative maturity of the laser technology, we also report the development of Tm-fiber lasers around the 2- \mum region specifically for tissue processing and laser-surgery applications.
A face-pumped Nd:YAG slab laser with high-power output and temperature fluctuation adaptability is proposed and demonstrated for the first time. A two-dimensional (2D) vertical-cavity ...surface-emitting laser (VCSEL) array at 808 nm with a low wavelength shift coefficient is used as the pump source with a total pump power of 1.38 kW. The array is cooled by a double-layer vascularized macro-channel heat sink for effective heat management. A 1064 nm maximum power of 437 W from the slab laser is obtained by optimizing the output coupling, and the power variation is only ±4.9% over the temperature range from 16 °C to 34 °C. The results show that the high-power slab laser pumped by VCSEL has an excellent performance in temperature tolerance and lower requirements for coolant, which is only water cooled by the macro-channel heat sink and no need for deionized water; it also provides a solution for high power lasers used in the complicated environment. Furthermore, it is possible to scale the output power to ~kW-level by further increasing the VCSEL pump power.
Inertial confinement fusion implosions designed to have minimal fluid motion at peak compression often show significant linear flows in the laboratory, attributable per simulations to percent-level ...imbalances in the laser drive illumination symmetry. We present experimental results which intentionally varied the mode 1 drive imbalance by up to 4% to test hydrodynamic predictions of flows and the resultant imploded core asymmetries and performance, as measured by a combination of DT neutron spectroscopy and high-resolution x-ray core imaging. Neutron yields decrease by up to 50%, and anisotropic neutron Doppler broadening increases by 20%, in agreement with simulations. Furthermore, a tracer jet from the capsule fill-tube perturbation that is entrained by the hot-spot flow confirms the average flow speeds deduced from neutron spectroscopy.
Deep ultraviolet (DUV) lasers are essential elements to versatile applications such as spectroscopy and lithography, and several techniques including free-electron lasers, excimer lasers and ...high-order harmonic conversion have been developed for DUV laser generation, yet the wavelength tunability and compactness are still challenging. Here, for the first time, we experimentally demonstrate a compact tunable continuous-wave (CW) DUV laser source by direct intracavity frequency doubling of visible fiber lasers. Efficient green/yellow laser emission is enabled by the down-conversion in the Ho<inline-formula><tex-math notation="LaTeX">^{3+}</tex-math></inline-formula>- or Dy<inline-formula><tex-math notation="LaTeX">^{3+}</tex-math></inline-formula>-doped ZBLAN fibers while the miniaturized cavity consists of a home-made fiber pigtail mirror and diffraction grating. The second harmonic generation from visible to ultraviolet is subsequently implemented by utilizing a BBO module intracavity. The achieved CW DUV lasers yield wavelength tuning range of 269.5-275.4 nm and 283.6-289.9 nm in the presence of an ultra-narrow linewidth of <inline-formula><tex-math notation="LaTeX">< </tex-math></inline-formula>0.025 nm. The produced power at 272.6 nm reaches 1.36 mW and a maximum visible-to-DUV efficiency of 5.3‰ is estimated with the green laser excitation. Our work therefore provides new possibilities for the realization of a new class of compact, wavelength tunable, and cost-effective CW DUV laser sources.
Cylindrical vector beams (CVB) with large topological charges extend their potential applications on high security optics communications, microparticle manipulation and high-resolution imaging, which ...are sensitive to laser wavelength. CVBs operating at new laser wavelengths converted with stimulated Raman scattering effect in Raman solid-state lasers fulfill requirements of these potential applications. Here, CVBs in form of Laguerre-Gaussian (LG0,l) with tunable topological charges have been generated directly in an annular pumped Raman microchip laser constructed with Yb3+:Y3Al5O12 crystal and vanadate crystal. The topological charge is tuned from 3 to 6 by changing applied pump power. Stable LG0,6 CVB is obtained in Raman microchip laser when pump power is in the range from 4 to 6.1 W. Maximum output power of 420 mW is obtained for LG0,6 vortex Raman laser at input pump power of 6.1 W, the optical conversion efficiency is 6.8%. The state of polarization of generated CVBs with topological charge l is E0,l(φ,r) = Eφ × sin(l-1)φ+ Er × cos(l-1)φ, Eφ, Er are unit vectors along azimuthal and radial directions. LG0,3 vortex laser oscillates in multi-longitudinal-mode around 1050 nm. LG0,4 and LG0,5 vortex lasers oscillate 1050 nm and 1076 nm two-wavelengths. LG0,6 vortex laser oscillates in multi-longitudinal-mode. Polarization purity is over 95% for LG0,l (l = 3, 4, 5, 6) CVBs generated in the Raman microchip laser. High beam quality is achieved for CVBs with measured M2 nearly equal to l +1.
High-power mid-infrared 2.8-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> ultrafast laser has potential applications in the fields of laser surgery due to its ...wavelength overlap with the absorption peak of water. In this work, we demonstrate a 2.8-<inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> picosecond Raman laser in a methane-filled hollow-core anti-resonant fiber (HC-ARF) with average power of 4 W, pulse energy of 40 <inline-formula> <tex-math notation="LaTeX">\mu \text{J} </tex-math></inline-formula>, and beam quality of 1.47. The laser beam quality improvement at mid-infrared Raman conversion in methane-filled HC-ARF is firstly observed. This work heralds a promising approach to generate mid-infrared ultrafast Raman laser with multi-Watt level average power and high beam quality.
This study aimed to obtain and investigate ZnCrsub.2Sesub.4 single crystals doped with rhenium. The single crystals were obtained by applying chemical vapour transport. An X-ray study confirmed the ...cubic (Fd3¯m) structure of the tested crystals. Thermal, magnetic, electrical, and specific heat measurements accurately determined the physicochemical characteristics, which revealed that the obtained single crystals are p-type semiconductors with antiferromagnetic order below the Néel temperature Tsub.N = 21.7 K. The Debye temperature had a value of 295 K. The substitution of Re-paramagnetic ions, possessing a screened 5d-shell, in place of Zn-diamagnetic ions, caused an increase in the activation energy, Fermi energy, and Fermi temperature compared to the pure ZnCrsub.2Sesub.4. The boost of the dc magnetic field induced a shift of Tsub.N towards lower temperatures and a spin fluctuation peak visible at Hsub.dc = 40 and 50 kOe. The obtained single crystals are thermally stable up to 1100 °C.
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