In order to meet the requirements of the new laser radar and laser active lighting for the miniaturized line light source, a linear laser light source that can be transmitted over long distances has been successfully designed and prepared. This linear laser light source is based on 808nm semiconductor laser. Firstly, a set of orthogonal placement plano-convex aspherical lens is used for collimating the laser beam of gauss distribution, thus the parallel beams that can be transmitted over long distances is obtained, and then through the Powell prism. Finally, the semiconductor laser is shaped into a laser light source with the slender and uniform intensity distribution. And we also have carried out an example design simulation with the Zemax optical design software and built an experimental system, and a laser light source has been successfully prepared with the divergence angles 54° of the fast directions and the uniformity 23.5% of the linear spot. The experimental results can match the Zemax simulation results well, which proves that the design method in this article is correct, simple and useful.
The blue laser diode (LD) illuminator in this study was composed of a cerium doped yttrium aluminum garnet (Ce:YAG) crystal, a 450-nm laser diode and an optical fiber. After a first-principles calculation, the energy gap of the Ce:YAG crystal was found to be 4.71 eV, which was less than that of the YAG. The luminescent properties of the Ce:YAG were determined by the electronic distribution of the Ce (d) and Ce (f) orbits. The Ce:YAG crystal had two characteristic absorption peaks of Ce<sup>3+</sup> at 332 nm and 455 nm. Hence, the 450-nm LD excited fluorescence spectra of a Ce:YAG crystal can be used for laser illumination. We discovered that the luminous efficiency of the LD increased with increasing color temperature for 4000 K, 5000 K, 6000 K and 6500 K but not for 3500 K, due to the low light transmittance of the thickest Ce:YAG crystal. The highest color-rendering index was about 70.0. Also, the blue laser without the 430-nm light from spectral radiance was, compared to an LED, a more serious eye hazard. We calculated that the permissible exposure time of the LD was longer than that of an LED. We also discovered that LD illumination is more secure than LED illumination.
Laser beam quality is an important parameter to evaluate the spatial characteristics of laser field. Based on the Wigner distribution function, the beam quality characteristics of one-dimensional field are analyzed and the beam quality factor is divided into intensity term, wavefront term and coherence term. The model shows that the incoherence in laser field affects the coherence term of the beam quality through the incoherence coefficient k(x<sub>1</sub>,y<sub>1</sub>,x<sub>2</sub>,y<sub>2</sub>), and then affects the beam quality of the whole field. The beam quality evolution trend of diode lasers with mode hopping or multi-mode in longitudinal mode is analyzed by simulation. It is shown that when the order of longitudinal modes in the laser increases, the influence on the beam quality is related to the laser field distribution, the depravation of beam quality is proportionally related with the transverse mode component of diode lasers.
As the critical component of concentrating photovoltaic module, secondary concentrators can be effective in increasing the acceptance angle and incident light, as well as improving the energy uniformity of focal spots. This paper presents a design of transmission-type secondary microprism for dense array concentrating photovoltaic module. The 3-D model of this design is established by Solidworks and important parameters such as inclination angle and component height are optimized using Zemax. According to the design and simulation results, several secondary microprisms with different parameters are fabricated and tested in combination with Fresnel lens and multi-junction solar cell. The sun-simulator IV test results show that the combination has the highest output power when secondary microprism height is 5mm and top facet side length is 7mm. Compared with the case without secondary microprism, the output power can improve 11% after the employment of secondary microprisms, indicating the indispensability of secondary microprisms in concentrating photovoltaic module.
A high-power high-beam-quality 1064nm Nd:YAG rod laser and SHG by intracavity-frequency-doubling are reported. With two common side-pumped Nd:YAG rod modules in the short cavity, we achieved an 78.5W near diffraction-limited pulsed wave 1064nm laser(M<sup>2</sup>=1.5) with pulse frequency 30kHz, pulse width 94ns and a good power stability of ±1% for over two hours. Finally, a 40W pulsed green laser with pulse width of 92ns in a near diffraction-limited beam (M<sup>2</sup>=1.45) is generated using an LBO crystal as the frequency doubler in the cavity.
This article describes high beam quality and kilowatt-class diode laser system for direct materials processing, using
optical design software ZEMAX® to simulate the diode laser optical path, including the beam shaping, collimation,
coupling, focus, etc.. In the experiment, the diode laser stack of 808nm and the diode laser stack of 915nm were used
for the wavelength coupling, which were built vertical stacks up to 16 bars. The threshold current of the stack is 6.4A,
the operating current is 85A and the output power is 1280W. Through experiments, after collimating the diode laser
beam with micro-lenses, the fast axis BPP of the stack is less than 60mm·mrad, and the slow-axis BPP of the stack is
less than 75mm·mrad. After shaping the laser beam and improving the beam quality, the fast axis BPP of the stack is
still 60mm·mrad, and the slow-axis BPP of the stack is less than 19mm·mrad. After wavelength coupling and focusing,
ultimately the power of 2150W was obtained, focal spot size of 1.5mm * 1.2mm with focal length 300mm. The laser
power density is 1.2×10<sup>5</sup>W/cm<sup>2</sup>, and that can be used for metal remelting, alloying, cladding and welding. The total
optical coupling conversion efficiency is 84%, and the total electrical - optical conversion efficiency is 50%.
High-power diode laser system is still belonging to the novel laser system currently. To realize the output of fiber
coupled high power diode laser will greatly enhance the applications of diode laser. In this article, we simulated beam
shaping and fiber coupling of diode laser with optical design software ZEMAX<sup>R</sup>, and discussed the problems would be
attended in the process of fiber coupling. Experiments on the beam shaping and fiber coupling were studied. Shape the
diode laser beam, homogenize fast and slow axis beam quality, and then realize high power diode laser output through
polarization coupling and wavelength coupling. Finally through the self-developed fiber coupling device, we achieved a
multi-wavelength high-power fiber-coupled diode laser output, the fiber core diameter 600um, NA 0.22. Before fiber
coupling the power of the diode laser was 773W, after fiber coupling, the output power was 664W, and the efficiency of
the fiber coupling is up to 85.9%.The fluctuation of the power is less than 1%.
KW-class high-beam quality diode laser system was introduced in this paper. In this system, the wavelengths of 808nm,
915nm, 940nm, and 980nm were used for the wavelength coupling and polarization coupling. The wavelength coupling
and polarization coupling can reach the optical efficiency of 91.4%. Before wavelength coupling, polarization coupling
and beam shaping, the maximum output power of the laser was 1200W, and after that, 1031W was achieved, so the
overall conversion efficiency reached 85.9 %. 12mm • mrad of the output beam quality was realized in both the fast axis
and the slow axis. Through intelligent control, the diode laser can work in different wavelength, different power and
different pulse width. Because of its output power and beam quality, this laser system can be used in the
ultra-long-distance laser detection, laser remote sensing and many other demands.