We demonstrated a 1.21-W 532-nm picoseconds (ps) green laser via second-harmonic generation (SHG) using type-I phase-matched K3B6O10Cl (KBOC) as a nonlinear optical crystal. The ps green laser was successfully generated from two types of 1064-nm ps lasers with one being operated at 10 kHz and the other at 10 Hz. Using a 7.38-W pumping power at 10 kHz as the pump, the SHG output power at 532 nm was 1.21 W with a pulse width of 34.4 ps. For the 10-Hz ps laser with pumping energy of 4.95 mJ per pulse, the output at 532 nm was 1.78 mJ per pulse, which corresponds to an optical conversion efficiency of 36.0%. The experimental results show that the KBOC crystal is a promising nonlinear optical crystal for generating ps green laser.
An investigation of laser cleaning of the oxide layers on the surface of the hot-rolled steel sheets was presented both experimentally and theoretically. By using a ∼100-ns pulsed laser, the optimized experimental parameters, such as the scanning speed, spatial overlap between two adjacent scans, and laser power density, were studied to obtain efficient and high-quality cleaning and avoid the formation of new oxide layer due to the heating by the laser. The temperature elevation and ablation depth were simulated and the data agree well with the experimental results. The change of composition of the surface layer, the surface roughness, and hardness due to laser ablation were also measured.
This paper reports a study on the relationship between the combining efficiency and reflectivity of output coupler of diode array in spectral beam combining. The combining efficiency is analyzed theoretically by using principle of the resonator. The simulation shows that high reflectivity will lead to low combining efficiency, and low reflectivity may cause the failure of wavelength locking. With increasing of the reflectivity of the OC, the combining efficiency changes like a downward parabola which has a maximum value of ~10%. The experiments demonstrate that the highest efficiency is obtained at a reflectivity of 10%, and the experimental results agree well with the theoretical analysis.
In this paper, we present the design of a 6 kW fiber-coupled laser diode system by using ZEMAX, and power scaling and fiber coupling techniques for high-power laser diode stacks were introduced in detail. Beams emitted from eight laser diode stacks comprised of four 960 W stacks with center wavelength of 938 nm and four 960 W stacks with center wavelength of 976 nm are combined and coupled into a standard fiber with a core diameter of 800 μm and numerical aperture of 0.22. Simulative result shows that the final power came out of the fiber could reach 6283.9 W, the fiber-coupling efficiency is 87%, and the brightness is 8.2 MW/ (cm2·sr).
We represent a design of a high brightness, fiber coupled diode laser module based on 16 single emitters at 915nm. The module can produce more than 150 Watts output power from a standard fiber with core diameter of 105μm and numerical aperture (NA) of 0.22. To achieve a high power and high brightness laser beam, the spatial beam combination and polarization beam combination are used to combine output of 16 single emitters into a single beam, and then an aspheric lens is used to couple the combined beam into an optical fiber. The simulation show that the total coupling efficiency is more than 95% and the highest brightness is estimated to be 11MW/ (cm2*sr).
Third-harmonic generation (THG) with high output power based on the type-I phase-matching La2CaB10O19 (LCB) crystal was investigated in yz plane (θ=48.7°, φ=90°), in which direction the effective nonlinear coefficient (deff) of LCB is 0.7, much larger than the previous reports in other direction. The maximum output power we obtained at 355 nm was as high as 11.5 W, and the beam quality was measured to 1.47 in x direction and 2.56 in y direction. The angular bandwidth and temperature bandwidth in this direction were measured, which are larger than the previous reports also.
We demonstrated a Q-switched Nd:LuVO4 laser with fundamental mode at 1064 nm using BaB2O4 electro-optic Q-switching. High-efficiency operation of Q-switched laser with dynamic to static ratio of 91.4% was realized. When the absorbed pump power was 6.59 W, the maximum average output power of 2.88 W was achieved with a repetition rate of 50 kHz. The optical conversion efficiency and slope efficiency were 43.7% and 55.5%, respectively. The minimum pulse width of 17.8 ns was achieved. Meanwhile, the pulse energy and peak power were 57.6 μJ and 3.2 kW, respectively. To the best of our knowledge, this study is the first to demonstrate about the electro-optically Q-switched laser in Nd:LuVO4 crystal.
We report a compact, 130-W single-stage master oscillator power amplifier with a high peak power of 51.3 kW and a narrow spectral linewidth of 0.1 nm. The seed source is a single-mode, passively mode-locked solid-state laser at 1064 nm with an average power of 2 W. At a repetition rate of 73.5 MHz, the pulse duration is 30 ps. After amplification, it stretches to 34.5 ps. The experiment enables the optical-to-optical conversion efficiency to reach 75%. To the best of our knowledge, this is the first report of such a high-power, narrow spectral linewidth, high peak power picosecond-pulse fiber amplifier based on a continuous-wave, mode-locked solid-state seeding laser. No amplified spontaneous emission and stimulated Raman scattering were observed when the pump was increased.
A high-power high efficiency picosecond (ps) 355 nm ultraviolet (UV) laser was reported based on the nonlinear optical crystal of type-I phase-matching La2CaB10O19 (LCB) which possesses the characteristic of non-hygroscopicity. The high-power third harmonic generation was successfully achieved from a 1064 nm ps fundamental laser. The maximum output power of 7.81 W of 355 nm UV laser was obtained from 35.2 W 1064 nm ps laser (80 MHz repetition rate, 10 ps pulse width) with optical conversion efficiency of 22.2%. The experimental results show that the LCB crystal has a promising prospect in generating high-power high efficiency UV laser.
During the process of laser ranging, the interaction between the target and the laser beam has the close relationship with the light scattering characteristic of the target surface, which can be characterized by the bidirectional reflectivity distribution function (BRDF). This paper discusses the effects of target reflective characteristics by the BRDF model and the Lambertian model. The BRDF is definited by surface parameters, such as surface roughness, correlation lengths and refractive index, incident angle and wavelength, which the Lambertian model does not include the detailed properties of the target. The results show BRDF is more precise than Lambertian model in factual environment. The main work is the research on calculating and comparing the minimal detectable power of laser rangefinder obtained the two models under different incident angles and surface roughness. The angular dependence of the BRDF is related to the microscopic properties of the surface. It showS that when the surface roughness increases the detectable power decreases rapidly. Modeling and simulation of the typical target shape of parabolic is provided in this paper on the bases of the BRDF and the LRCS is calculated. According the above study, it will provide some fruitful reference for further parameters choice of laser rangefinders and laser radar.
We have proposed a metallic dipole-ellipsoid-bagel nanostructure for the generation of high harmonics via two-color laser field. Comparing with the case of the one-color field, this nanostructure enables a broader bandwidth and smoother harmonic spectra under the condition of the two-color incidence field, which is in favor of the generation of extreme-ultraviolet (XUV) radiation and isolated attosecond pulses. Numerical techniques are employed to optimize nanoantennas and attain enhanced plasmonic field. The electromagnetic properties of this nanostructure is fully analyzed and discussed. The nanostructure support the highest enhancement fact of 2500 for both of 800-nm and 1500-nm incidence, and effectively enhance the field intensity exceed 103 in the volumn of 50×50×50 nm3.This nanostructure would benefit for the generation of high-harmonic, extreme-ultraviolet (XUV) radiation via plasmonic enhanced filed in a two-color multi-cycle laser field. This work would have potential application in the ultra-sensitive color sensor and the source of isolated attosecond pulses via multicycle laser.
We demonstrated a passively Q-switched Nd:YAG laser operating at 1.319 μm using a transmission-type single-wall carbon nanotube (SWCNT) as the saturable absorber. This is the first report on using SWCNT as a Q-switcher for 1.319 μm Nd:YAG laser in a side-pumped configuration. A maximum output power of 780 mW was obtained with 1.15-μs pulse duration and 42.7-kHz repetition rate.
During the process of laser propagation in free space, energy attenuation is brought by atmospheric medium. One of the major problems about laser propagation is that atmospheric component does not remain constant within the whole altitude band. So working out the relatively accurate attenuation coefficient is a research interest of many researches for several years. On this basis of analysis of the atmospheric component distributing characteristic, simple and practical simulate approach was given to meet the needs of laser rangefinder. The main work is the research on 1.06μm YAG laser transmission characteristics in the atmosphere, and the atmosphere loss of the mathematical model is investigated. The paper discussed the influence of atmospheric attenuation on ranging ability of laser rangefinder and analyzed the atmospheric attenuation theoretical. It showed that when the attenuation coefficient γ increases the detectable distance decreases rapidly. In the condition of three transmission modes, which are ground-to-ground mode, ground-to-air mode and air-to-air mode, the relationships between atmospheric transmittance and different visibility, different zenith angle were analyzed. Minimal detectable power of laser rangefinder represents ranging ability in above-mentioned three different modes was formulated with atmospheric transmittance. Based on the results, we can adjust the experimental parameters and achieve more desirable results. It has positive influence for the design of laser rangefinder.
In this paper, we investigated the characteristic of radar target, the spherical and the pyramidal missile warheads, and compared the RCS and performance of the targets with and without the cover of the plasma metamaterials. Numerical simulation is obtained by the numerical calculation Finite-difference time-domain method (FDTD). The parameters of plasmonic structures as a metamaterial cloak was designed and optimized. The relationship between the parameters of the cloak and the corresponding electromagnetic characteristic of the target are analyzed by the simulation and discussion in broadband radar signals. After optimization, the plasma cover could attenuate 40 dBsm of the radar cross section (RCS) of the targets maximally. The result shows that the anomalous phenomenon of cloaking and stealth effects induced by plasma materials for the radar target, which might have potential application of military affairs.
We have theoretically investigated and optimized a nano-periodical highly-efficient blazed grating, which is used as an outcoupler for extreme-ultraviolet (XUV) radiation. The rigorous coupled-wave analysis (RCWA) with S matrix method is employed to optimize the parameters of the grating. The grating is designed to be etched on top layers of IR reflector, performs as a highly-reflective mirror for IR light and highly-efficient outcoulper for XUV. The diffraction efficiency of -1 order of this XUV outcoupler is greater than 20% in the range near 60 nm, which allows high resolution spectroscopy of the 1s-2s transition in He+ at around 60 nm with extreme precision. The theoretical calculations are verified by the experimental results.
We theoretically investigate utilizing the enhanced plasmonic fields in metallic nanostructures. Numerical techniques are employed to optimize nanoantennas to attain the enhanced plasmonic fields up to 270. In the volume of 15 × 15 × 30 nm3 in nanoantenna, the intensity could be enhanced to 1014 W/cm2 for high harmonic generation (HHG). Optimal conditions for the production of MHz isolated attosecond pulse of 140 attosecond via HHG have been identified. These findings open up the possibility for the development of a compact source of ultrashort XUV pulses with MHz repetition rates. our simulations indicate a potential route towards the temporal shaping of the plasmonic near-field and in turn the generation of single attosecond pulses. Such XUV sources, which may operate at MHz repetition rate, could find applications in high-precision spectroscopy and for spatio-time-resolved measurements of collective electron dynamics on nanostructured surfaces. Moreover, the asymmetric cross nanoantennas is proposed to control the polarizations and select the wavelengths via varying the ratio of nanoantennas and generate the XUV pulse in both polarized direction.
Black silicon is very promising for the third generation Solar Cells, because of its fascinating light absorption of above
98% in visible spectrum and more than 90% in 800-2500 nm, and its surface micro-nano structures enlarge light trapping
intermediate impurities levels caused by supersaturated doping expand absorptive limitation of crystalline Si. In recent
years femtosecond laser pulses were widely used in the process of improving the absorptance by irradiating silicon
surfaces with in the presence of different gases. Nevertheless, picosecond laser used to fabricate large-area black silicon is seldom reported. A diode-pumped picosecond Nd:YAG regenerative amplifier laser system designed for microstructuring the crystalline silicon was reported in this paper. At the repetition of 1 kHz, the system generated 1 W average-power, 26-ps-long pulses with a pulse energy of 1 mJ at 1064 nm, which corresponds the peak power of 38.5 MW. A 0.5 W second-harmonic 532 nm laser is achieved with a 20 mm long noncritically phase-matched lithium triborate (LBO) crystal from the 1W 1064 nm laser. igh optical absorption black Si irradiated with 1064 nm and 532 nm picosecond pulses in SF6 at different laser fluence. And the relationship between the surface morphology and the wavelength or the laser fluence was researched.
Seven output wavelengths ranged from violet to mid-infrared have been observed simultaneously from a optical parametric oscillator with a periodically poled lithium niobate crystal. The pump laser is diode-pumped Q-Switched Nd:YVO4 laser with the wavelengths at 1064 nm. The turning output wavelengths can be obtained by changing the periods or temperatures of PPLN. The seven output wavelengths, corresponding to the sum frequency generation of the pump and the doubling signal ( 2ωs+ωp), the third harmonic generation of the signal ( 3ωs ), the second harmonic generation of the pump (2ωp), the sum frequency generation of the pump and the signal (ωs+ωp), the second harmonic generation of the signal (2ωs), the signal (ωs) and the idler (ωi), measured are 433, 488, 532, 616, 731, 1463 and 3902 nm, at the period of 28.7 μm with the temperature of 333 K. These data showed good agreement with those calculated by the Sellmeier equation. This phenomenon may find novel applications in photonic devices.
We report a high power continuous tunable blue light generation by frequency doubling of signal wave from a nanosecond 532-nm-pumped optical parametric oscillator (OPO) in LiB3O5 (LBO). The nonlinear crystal BiB3O6 (BiBO) is used for the second harmonic generation (SHG). Three BiBO crystals have been arranged for the walkoff compensation SHG. The large blue tuning range from 450 to 495 nm with average output powers around 1 W have been achieved. The maximum output power is up to 1.3 W at 470 nm.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.