High Power Diode Laser Stacks Research Articles

Study on the Technique of Beam Coupling for High Power Diode Laser Stack

High-power lasers based on GaAs bars meanwhile are well established as reliable and highly efficient laser sources. Continuous improvement of the material itself, mounting and cooling techniques during the last years have led to increased output power and high lifetimes. This paper summarized beam shaping technology of high-power lasers and evaluated these advantages and disadvantages. The beam coupling methods of the high power laser array were expatiated and a new beam coupling structure was present in the paper, also as the results and analysis of polarization coupled experiment.

Two-dimensional beam shaping and homogenization of high power laser diode stack with rectangular waveguide

In this paper, the research work of two-dimensional beam shaping and homogenization of high power laser diode (LD) stack by a rectangular waveguide is presented. Both the theoretical simulation and experiment results have shown that the diode stack beam can be shaped into a uniform square spot with a dimension of 10 mm × 10 mm and the non-uniformity less than 5% along both directions of slow axis and fast axis, the shaped beam has a uniform pumping depth over 10 mm, which is well to be used for a rectangular laser medium end pumping.

The Beam Characteristics of High Power Diode Laser Stack

Direct diode lasers have some of the most attractive features of any laser. They are very efficient, compact, wavelength versatile, low cost, and highly reliable. However, the full utilization of direct diode lasers has yet to be realized. However, the poor quality of diode laser beam itself, directly affect its application ranges, in order to better use of diode laser stack, need a proper correction of optical system, which requires accurate understanding of the diode laser beam characteristics. Diode laser could make it possible to establish the practical application because of rectangular beam patterns which are suitable to make fine bead with less power. Therefore diode laser cladding will open a new field of repairing for the damaged machinery parts which must contribute to recycling of the used machines and saving of cost.

Generation of neutral atomic beams utilizing photodetachment by high power diode laser stacks

We demonstrate the use of high power diode laser stacks to photodetach fast hydrogen and carbon anions and produce ground term neutral atomic beams. We achieve photodetachment efficiencies of ∼7.4% for H(-) at a beam energy of 10 keV and ∼3.7% for C(-) at 28 keV. The diode laser systems used here operate at 975 nm and 808 nm, respectively, and provide high continuous power levels of up to 2 kW, without the need of additional enhancements like optical cavities. The alignment of the beams is straightforward and operation at constant power levels is very stable, while maintenance is minimal. We present a dedicated photodetachment setup that is suitable to efficiently neutralize the majority of stable negative ions in the periodic table.

Narrow-bandwidth and stable-wavelength operation of spatial beam-combining high-power laser-diode stack configuration using a single volume Bragg grating

The spectral bandwidth was effectively suppressed and the wavelength was locked for two high-power laser-diode (LD) stacks with an external-cavity configuration that consisted of a stripe mirror and volume Bragg grating. During operation at a drive current of 100 A, the bandwidth was reduced from 2.59 to 0.31 nm (8.4-fold reduction), and a peak power output of 581 W was achieved. The power spectral density of the combined beam was increased to 1874 W/nm from 279 W/nm. The high-power-density external-cavity LD stack source showed a narrow spectral bandwidth and stable spectrum over the entire current range.

基于微透镜阵列的半导体激光器堆栈匀化系统

The intensity distribution of diode laser is not uniform due to the broad-area and ridge-waveguide designs, the poor beam quality is the limiting factor of applications. In order to achieve homogenized spot by the beam shaping of high-power diode laser stack, a homogenization system for diode laser stack beams based on microlens array is designed. The diode laser beam shaping theory and process of microlens array are analyzed. The lower limit of clear aperture of microlens is confirmed by the analysis of the impact of the diffraction of microlens edge on the spot homogeneity. The intensity angle distribution of spot is defined by paraxial matrix optical analysis. The simulation and experimental test are carried out for the microlens array beam shaping system, realizing the spot with the homogeneity of 91.89%. ©, 2015, Science Press. All right reserved.

Beam reshape of high power laser diode stack

Based on the ray tracing method the laser intensity distribution of single DL bar collimated with micro spherical cylindrical lens was analyzed in detail. We found that the intensity distribution of output laser have a better flat shape when the divergence angle is about 5. A beam reshape system was designed for a 25-bar DL stack. The system includes microlens of fast axis collimating, coupling lens of fast axis and coupling lens of slow axis. The laser medium to be pumped was designed at the focus plane of fast axis coupling lens and close to the imaging plane of slow axis coupling lens. A 7 mm8 mm pump beam was obtained with intensity uniformity of 90%. The coupling efficiency of the beam reshaping system reached 85%.

Beam shaping of high power diode laser stack into homogeneous line

In this paper, analysis of beam shaping and homogenization of high power diode laser stack into a line focus with dimension of 10 mm × 0.5 mm was reported. The beam shaping and homogenization was simulated by using ZemaX-ray tracing technique. The results have shown that intensity distribution after beam shaping and homogenization at the work piece is a flat top for the slow axis with homogeneity over 95% and a Gaussian distribution for the fast axis.

高功率叠阵二极管激光器光束整形

高功率叠阵二极管激光器光束整形

Double-end-pumped Nd:YVO4 slab laser at 1064 nm

We demonstrate a high-power laser diode stacks double-end-pumped Nd:YVO4 1064 nm slab laser with a folded stable-unstable hybrid resonator. An output power of 220 W was obtained at the pump power of 490 W with optical conversion efficiency of 44.9%. At the output power of 202 W, the M2 factors in the unstable direction and in the stable direction were 1.7 and 2.3, respectively.

A beam shaping design for coupling high power diode laser stack to fiber with capability of spectral narrowing and stabilizing

We applied a VHG-FAC lens in our design in this work to collimate the fast axis and lock the output spectrally. We used a beam shaping technique to improve the beam symmetry and power density of a high power diode laser stack with a stripe mirror plate, a V-Stack mirror and polarization beam combining elements. By this technique, the beam of a high power diode laser stack is effectively coupled into a standard 365μmcore diameter and a NA=0.22 fiber. By this technique, compactness, higher efficiency, narrower spectral line width and lower production cost of the diodes are possible.

Beam shaping design for coupling high power diode laser stack to fiber

A beam shaping technique that rearranges the beam for improving the beam symmetry and power density of a ten-bar high power diode laser stack is simulated considering a stripe mirror plate and a V-Stack mirror in the beam shaping system. In this technique, the beam of a high power diode laser stack is effectively coupled into a standard 550 μm core diameter and a NA=0.22 fiber. By this technique, compactness, higher efficiency, and lower cost production of the diode are possible.

Efficient pump beam shaping for high-power thin-disk laser systems

We report a beam-shaping technique whereby the output power from a high-power laser-diode stack is efficiently coupled, reconfigured, and transmitted to a thin-disk laser by means of a compact optical fiber bundle. By using this technique, the power density is increased by a factor of 2 when compared to direct coupling with a octagonal fused silica rod while the numerical aperture is kept constant. Transmission efficiency of 80% was measured for the beam shaper without antireflection coating. The top-hat distribution is numerically calculated at the thin-disk laser crystal.

Beam-shaping method for uniform illumination by superposition of tilted Gaussian beams

Efficient beam shaping with uniform illumination is required in laser active imaging and detecting systems. In this paper, a beam-shaping method by superposition of tilted fundamental-mode Gaussian beams to produce nearly uniform illumination is proposed. The analytical formula for the average intensity of propagating multitilted Gaussian beams (MTGBs) is derived and used to study the uniformity of the beam profile with Fourier analysis. It is found that the MTGB maintains its flat-topped shape as it propagates and its uniformity is controlled by the parameters of fundamental-mode beams and superposition. Numerical examples are given. The method is used to reconfigure the beams of a high-power laser diode stack to form a MTGB shape for illumination of a 9×11.6-deg angular field. The simulation results from ASAP software show a shaping efficiency of 75%, and the rms deviation of the irradiance distribution from a flat-top shape is approximately 8%.

Beam-shaping technique for improving the beam quality of a high-power laser-diode stack

We report a beam-shaping technique that reconfigures the beams to improve the beam quality and enhance the power density for a ten-array high-power laser-diode stack by using two optical rectangular cubes and two stripe-mirror plates. The reshaped beam has threefold improvement in beam quality, and its power density is effectively enhanced. On the basis of this technique, we focus the beam of the high-power laser-diode stack to effectively end pump a high-power fiber laser.

Effective Suppression of Beam Divergence for High-Power Laser-Diode Stack Based on External-Cavity Technique

We demonstrate an off-axis external-cavity configuration designed to effectively suppress the beam divergence of a high-power laser-diode stack. The off-axis external cavity consists of a set of beam-transformation systems and a stripe mirror. Thirty-eight off-axis external-cavity laser diodes are individually formed for the high-power laser-diode stack. At a drive current of 40 A, the divergence angle of the slow axis is reduced from 7.6° without the external cavity to 1.6° with the external cavity. The external-cavity laser-diode stack achieves a cw power output of 45 W, or 72.4% of the cw power output of a free-running laser-diode stack.

407 W End-pumped Multi-segmented Nd:YAG Laser

A composite crystalline Nd:YAG rod consisting of 5 segments with different dopant concentrations for high power diode end-pumping is presented. A maximum laser output power of 407 W with an optical-to-optical efficiency of 54 % was achieved by longitudinal pumping with a high power laser diode stack.