Cladding Light Strippers Research Articles

Efficient Suppression of Backward Light Scattering for Optical Fiber Cladding Light Stripper

This study investigates a method for the effective suppression of backscattering within optical fiber cladding light strippers (CLSs) with a periodically grooved structure. First, the relationship between the backscattering of cladding light and the surface roughness of the cladding for a periodically grooved CLS is theoretically investigated using the ray-tracing method. It is found that the backscattering of cladding light depends on the surface roughness of the grooves and that undesired backscattering significantly affects the stripping capability of a CLS. Based on the theoretical results, we propose a periodically grooved CLS structure with multiple unetched sections of a suitable length and verify its effectiveness by comparing its lightwave stripping performance with that of a conventional CLS design in both theoretical and experimental ways. Unlike the conventional structure, our proposed structure demonstrates almost uniform lightwave stripping without localized overheating.

Atomic layer deposition of zirconium oxide thin film on an optical fiber for cladding light strippers

Cladding light strippers are essential components in high-power fiber lasers used for removal of unwanted cladding light that can distort the beam quality or even damage the whole fiber laser system. In this study, an Atomic Layer Deposition system was used for the first time to prepare the cladding light stripper devices using a 40 nm thick zirconia layer grown on optical fiber. The thickness of the zirconia coating was confirmed using the Scanning Electron Microscopy (SEM) and the Ellipsometry techniques. The elemental analysis was also performed using the wavelength dispersive X-ray spectroscopy technique. The Raman spectroscopy and XRD data confirm the structure of the atomic layer deposition-grown zirconia thin films to be predominantly amorphous. The cladding light stripper devices formed using the zirconia thin films with the lengths of 8.5 and 15.5 cm were able to strip approximately 30% (~1.5 dB) and 40% (~2.3 dB) of the unwanted cladding light.

Combined method for the fabrication of high-power cladding light stripper using a buffered oxide etchant.

Cladding light strippers (CLSs) are vital and one of the critical components for high-power fiber laser applications. In this study, we show the first studies of the formation mechanisms and optimum conditions of a CLS device using a buffered oxide etchant by a combined method of stain (wet) etching and vapor-phase etching. This high-power CLS was shown to result in a stripping performance of ∼17.2 dB at the launched power of 333W (pump limited). The thermal imaging demonstrates that the maximum temperature reached when operating the device at maximum launched power was ∼75°C. The atomic force microscopy (AFM) results show that the combined method yields crystal-like structures with the height in microscales, whereas other conventional methods give only nanoscale roughness. The method also preserves the diameter of the CLS device close to the bare fiber with about 10μm tapering leads to a high surface area to strip unwanted light, which is good for heat dissipation. The combined method possesses the outcome of two methods, including both the crystal-like structures and nanosized hillocks, resulting in high-power stripping performance and robustness.

2 kW single-mode fiber laser employing bidirectional-pump scheme

A 2 kW single-mode fiber laser with two cascade home-made cladding light strippers (CLSs) has been demonstrated by employing bidirectional-pump scheme. 2.009 kW signal power is obtained when pump power is 2.63 kW and the slope efficiency is 76.6%. Raman Stokes light is less than -47 dB at 2.009 kW even with a 10-m delivery fiber with core/inner cladding diameter of 20 μm/400 μm. The beam quality M2≤1.2 and the spectral FWHM bandwidth is 4.34 nm. There is no transverse mode instability and the output power stability of ±0.14% is achieved by special thermal management for a more uniform temperature distribution on the Yb-doped gain fiber.

CO2 laser-fabricated cladding light strippers for high-power fiber lasers and amplifiers.

We present and characterize a simple CO2 laser processing technique for the fabrication of compact all-glass optical fiber cladding light strippers. We investigate the cladding light loss as a function of radiation angle of incidence and demonstrate devices in a 400 μm diameter fiber with cladding losses of greater than 20 dB for a 7 cm device length. The core losses are also measured giving a loss of <0.008±0.006 dB/cm. Finally we demonstrate the successful cladding light stripping of a 300 W laser diode with minimal heating of the fiber coating and packaging adhesives.

高功率光纤激光器包层光滤除器的温度场研究

Unwanted cladding light in output of double-cladding fiber lasers has major adverse effect on the beam quality,spectral characteristics,and reliability and stability of lasers.It is of vital importance to strip the cladding light for engineering of the double-cladding fiber lasers.The thermal effect of high power cladding light strippers is studied theoretically and experimentally.The temperature distribution is simulated by means of computational fluid dynamics based on ANSYS.The experiments validate that the temperature simulation is effective and applicable for stripping power ranging from 15 W to 600 W.Furthermore,a kW-level cladding light stripper is optimized based on the thermal simulation.After optimization,the temperature of the stripper declines by up to 46℃,and the stripper can run stably at about 80℃.

Cascaded Cladding Light Extracting Strippers for High Power Fiber Lasers and Amplifiers

We demonstrate efficient cladding light extracting through cascaded strippers for high-power fiber lasers and amplifiers. A selected part of the fiber is divided into five segments, and the fluoroacrylate jackets of three interval segments are gradually removed and replaced with different higher index polymers. It is shown that such cascaded strippers can overcome the challenging problems of localized heating and thermal degradation of the recoating materials, which are limiting factors for the conventional high power cladding light strippers. The power-handling capability of the device is tested up to cladding light of power up to 150 W. A high attenuation of 18 dB has been achieved, whereas the maximum local temperature is less than 64 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> C. We anticipate that this simple configuration offers a practical solution for cladding light extracting in high power fiber lasers and amplifiers.

全光纤激光器光束质量的优化

On the basis of laser structures,factors affecting on the beam quality were experimentally explored to improve the beam quality of fiber lasers.A hundred-watts class all-fiber laser with an output power of 300Wat 1 080nm was built when the maximum pump power was 436 W.The beam quality(M2)was tested,and experiments show that the M2 is 1.13and optical-optical conversion efficiency is 69%.Then,the change of the radial power distribution of the laser beam that transported in a fiber was experimentally analyzed.The result shows that the cladding light power increases initially and remains constant afterwards as the transmission distance of laser beam increases in the fiber. Therefore,different beam qualities can be obtained after stripping the cladding light at any selected transmission distance.In addition,the higher laser output power can be obtained when the cladding light stripper is set inside instead of outside of the cavity under the same pumping conditions.However,a worse beam quality is left in this case.Finally,a better beam quality M2 at 1.07is obtained by setting two cladding light strippers outside and insider the cavity,respectively.