We present monolithic 910-nm high power vertical-cavity surface-emitting laser (VCSEL) module suitable for longdistance LIDAR (Light Detection and Ranging). The 910-nm high-power VCSEL array is finely designed and fabricated. The output power of a single VCSEL array (163 devices) reaches nearly 2 W under QCW operation, without being cooled. Driven by the external current source, the peak output power of a single VCSEL array reaches 25.5 W under pulsed operation with a repetition frequency of 10 kHz and a pulse width of 30 ns. To improve the pusled performance of VCSEL array, the monolithic VCSEL array module with integrated driver is developed. The peak output power of this module reaches nearly 85W. And its optical pulse width is 22 ns only. Thus integrated driver circuits demonstrate much better pulsed properties. The ranging setup is built and the detection distance of more than 20 m is realized. We believe that this monolithic VCSEL array with high power, dense package and superior impulse response has great commercial potential in future applications requiring intelligent driving like LIDAR for automotive.
Laser induced breakdown spectroscopy (LIBS) is a promising technique, analyzing spectrum of plasma, to detect elements of solid, liquid or gaseous samples. It has many advantages, including in-situ and online detection, remote analysis, non-preparation of samples, and simultaneously multi-elements detection. Aiming at detecting detrimental elements in the polluted river and water, in this paper, collinear dual-pulse (DP) Laser-induced breakdown spectroscopy (LIBS) with liquid jet was employed to analyze emission spectrum of Cu element in the CuSO4 solution. We investigated the effect of laser pulse energies ratio and time delay between two lasers on signal intensity, which were simply given by theoretical model in laser-induced plasma for explaining various behaviors of emission spectrum. It was inferred that the maximum signal enhancement of DP-LIBS experiment was roughly 4.5 times greater than that of SP case. The limit of detection (LOD) of Cu using DP-LIBS was approximately 15 times lower than that of SP-LIBS. Results of this research indicate that collinear DP-LIBS is an effective approach to improve the plasma emission intensity and reduce the value of LOD, the application of which can be considered into the environmental problem of the water pollution.
In order to further increase the fiber-coupled module output power, eight cm-bar 808 nm laser diodes, 50 w output each, fiber coupling module has been designed by using ZEMAX optical design software through space and polarization beam combination method. The core diameter of output fiber is 400 μm with a numerical aperture of 0.22. Finally the fiber output power is 350.2 W, with a coupling efficiency of 87.6%.
According to the special requirements of combination film in 10kW diode laser cladding source, the polarization combination film at 915nm was designed and grew. Film system is designed at different film materials based on the design theory. The non-QWOT film is optimized using the needle optimization and double sided coating by Optilayer software. The film was used in the 10kW diode laser source after high temperature aging testing. The film formed by Ta2O5 is very stable under IBAD, which can meet the reliability of 10kW diode laser cladding source in industry
In order to research the laser damage mechanism of high transmission single layer optical thin film for fused silica glass, finite element method was used to calculate laser induced damage threshold (LIDT) and an optical test system with a nanosecond solid-state lasers was set up to determine the LIDT according to standard of ISO 11254. Firstly, finite element model was created at COMSOL multi-physics software and the temperature of inclusion in the optical thin film was calculated with different physical parameter. It is found that temperature at center of the inclusion firstly decreases and then increase with the increasing of inclusion depth. It is also found that the temperature constantly increase with the radius increasing from 20nm to 100nm. Moreover, the inclusion temperature for MgF<sub>2</sub> thin film is higher than that of CaF<sub>2</sub> thin film. Lastly, LIDT were measured by the optical test system, and the average value of LIDT is 3.7J/cm<sup>2</sup> for MgF<sub>2</sub> thin film and 4.6J/cm<sup>2</sup> for CaF<sub>2</sub> thin film, which is well fit with the value calculated by COMSOL software. The study shows that finite element method is an effective method to calculate LIDT for optical thin film and impurity has significant impact on the LIDT of optical thin film and therefore decreasing the density of the impurity would increase the LIDT of the thin film.
Thermal effect of diode-pumped solid-state lasers (DPSSL) based on YAP/Tm:YAP composite crystal is studied by
using of finite element method (FEM). It is found that the peak temperature in a composite rod decreases to less than
80% of that in a non-composite crystal. Thermal stress of composite rod is obviously reduced to less than 70%
comparing with non-composite crystal. It is also demonstrated that length of thermal lens unchanged with increasing of
un-doped crystal length, which means that beam quality of composite laser wouldn’t be improved by non-composite
crystal. Therefore, it is concluded that using composite crystal would benefit for the properties of temperature and heat
stress while insignificance for beam quality of DPSSL.