Laser Diode Beam Shaping Research Articles

Influence of positioning errors of optical shaping components for single emitter laser diode on beam shaping effects

Beam shaping is required for semiconductor lasers to achieve high optical fiber coupling efficiency in many applications. But the positioning errors on optics may reduce beam shaping effects, and then lead to low optical fiber coupling efficiency. In this work, the positioning errors models for the single emitter laser diode beam shaping system are established. Moreover, the relationships between the errors and the beam shaping effect of each shapers are analysed. Subsequently, the relationship between the errors and the optical fiber coupling efficiency is analysed. The result shows that position errors in the Z axis direction on the fast axis collimator have the greatest influence on the shaping effect, followed by the position errors in the Z axis direction on the converging lens, which should be strictly suppressed in actual operation. Besides, the position errors have a significant influence on the optical fiber coupling efficiency and need to be avoided.

宽发射面激光二极管光束整形系统的光学设计

宽发射面激光二极管光束整形系统的光学设计

Shaping laser diode beam into three rectangles by a DOE array to divide input wavefront

To resolve the variability of the intensity distribution and the divergence of the laser diode (LD) output beam in a beam shaping system, a diffractive optical element (DOE) array is proposed in LD beam shaping. This DOE array can divide the wavefront of input beam. All light diffracted by all DOE array units is super-positioned on the output plane, and the tolerance for the input beam is improved by this means. Using the above DOE array laser shaped method, three rectangles intensity distribution are realized from Gaussian beam with the diffraction efficiency of 90.5% and the uniformity of 96%. When the half divergence angle of the LD varies from 2o to 16o in slow and fast axis directions, respectively, the diffraction efficiency maintains to be approximate 90% and its uniformity is more than 95%. When the defocus of the lens to collimate LD beam varies from -32 to 32 \mu m, numerical experiments indicate that uniformity and the diffraction efficiency of the shaped beam by the DOE array do not vary.

Laser diode beam shaping by optical interference

We recently proposed a novel beam shaping technique that employs Lloyd’s mirror interference. In this study, we apply this technique to three commercial laser diodes: laser diodes used for optical pumping of solid-state lasers, for laser beam printers, and for laser displays. The elliptical output beams from these laser diodes could be transformed into nearly circular beams by inserting a mirror-polished GaAs substrate below the active layer of each laser diode and adjusting its height. The experimentally observed far-field patterns were predicted fairly well by numerical calculations based on Huygens’ integral. We confirmed that our beam shaping technique is applicable to laser diodes with various wavelengths and vertical beam divergence angles. We also describe the monolithic configuration of the beam shaping system, which can be fabricated by dry etching.

High power fiber lasers

In this review article, the development of the double cladding optical fiber for high power fiber lasers is reviewed. The main technology for high power fiber lasers, including laser diode beam shaping, fiber laser pumping techniques, and amplification systems, are discussed in detail. 1050 W CW output and 133 W pulsed output are obtained in Shanghai Institute of Optics and Fine Mechanics, China. Finally, the applications of fiber lasers in industry are also reviewed.

Laser diode beam shaping with GRIN lenses using the twisted beam approach and its application in pumping of a solid-state laser

We report a novel beam shaping method for laser diodes based on the concept of twisted Gaussian Schell-model beams using GRIN lenses. This method enables a more symmetric pump as well as a compact setup for pumping of solid-state lasers. In the experiment with a standard 2 W diode, the beam quality factors in the two orthogonal directions were equalized to M x 2 ≈ 24 and M y 2 ≈ 18 , respectively, which pumped an intra-cavity frequency-doubled Nd:YAG laser at 946 nm with an output of 28 mW at 473 nm.

Ultra-precision machining of reflector array for laser diode beam shaping

Ultra-precision machining is an effective approach to achieve high dimension accuracy and surface finish required in optical and laser components. An extensive study using a two-axis diamond turning machine is conducted to machine the reflector arrays used for laser diode beam shaping. To position the workpiece precisely, theoretical analysis is made so that the dimensional accuracy can be achieved. Investigations into machining burr reduction are carried out. With the process developed, reflectors with optical surface finish of 8 nm in Ra and minimized burr size of less than 0.5 μm have been achieved.

An experimental study of micromachining step-mirrors for laser-diode beam shaping

Micro and ultra-precision machining is an effective approach to achieve the high-dimensional accuracy and surface finish required in optical and laser components. In this paper, an extensive study using a two-axis diamond turning machine is conducted to machine the step-mirrors used for laser-diode beam shaping. To position the workpiece precisely, theoretical analysis is made so that dimensional accuracy can be achieved. Investigations into machining burr reduction are carried out. With the process developed, step-mirrors with an optical surface finish of 8 nm in Ra and a minimized burr size of less than 0.5 µm are achieved.