RESUMEN
To investigate the characteristics of the achromatic bandwidth of composite achromatic quartz half-wave plates (QHWPs), three kinds of multi-element achromatic QHWPs with central wavelengths at 1000-3000 nm and relative deviation of the maximum phase retardation (Δδmax) of 1%-5% are discussed. Based on the particle swarm optimization algorithm, the maximum bandwidth of the composite achromatic QHWPs at room temperature is obtained. The results show that the achromatic bandwidth increases with Δδmax. At the same Δδmax, the achromatic bandwidth of four-element achromatic QHWPs is larger than that of two- and three-element achromatic QHWPs. The maximum achromatic bandwidth of four-element achromatic QHWPs can reach 2229 nm when Δδmax is 5%. In addition, the temperature effect on bandwidth in the wavelength range of 300-1500 nm is analyzed, and the maximum bandwidth of temperature insensitive composite achromatic QHWPs is 840 nm. The results provide a great reference for designing achromatic wave plates with broad bandwidths.
RESUMEN
In order to improve the output power of solar-pumped single-crystal fiber (SCF) lasers, we propose a novel solar concentrating system, to the best of our knowledge, consisting of a parabolic mirror, a 3D compound parabolic concentrator, and a hollow-core reflector. By ray tracing with TracePro, the influence of the fiber's diameter and the hollow reflector's shape on the solar absorption efficiency is theoretically investigated. A typical Nd:YAG SCF with a core diameter of 1 mm, length of 150 mm, and doping concentration of 1 at.% is selected for a simulation of laser operation. The output characteristics of the laser are analyzed by solving the rate equation and power transmission equation; the maximum output power and solar-to-laser conversion efficiency are 60.62 W and 4.64%, respectively. The thermal effects of the laser are simulated by Comsol software. When the input solar power is 1307.4 W, the temperature decreases sharply first and then saturates along the SCF fiber, with the maximum value of 69.18°C at the input fiber end. This concentrating system can effectively overcome the limitation of end-launching solar power into SCFs and has great potential in improving the output power of solar fiber lasers.
RESUMEN
In order to obtain a composite achromatic wave plate with adjustable retardation, temperature insensitivity, and achromatic bandwidth of 500 nm, a five-element composite achromatic quartz wave plate is designed based on particle swarm optimization. The total phase retardation can be adjusted by rotating the azimuth angle of the central wave plate. The results show that the total phase retardation is adjustable with the range of 90°-180° when the range of temperature and the achromatic wavelength is -20-80∘C and 750-1250 nm, respectively. The absolute value of the relative deviation of the maximum phase retardation is less than 3.6%, which meets the design requirements of the wave plate. The temperature insensitivity of the five-element wave plate is better than the three- and four-element wave plates. This method is of great reference value for designing this kind of composite achromatic wave plate.
