High brightness fiber laser pump sources based on single emitters and multiple single emitters

Abstract

Driven by the potential of the fiber laser market, the development of high brightness pump sources has been pushed during the last years. The main approaches to reach the targets of this market had been the direct coupling of single emitters (SE) on the one hand and the beam shaping of bars and stacks on the other hand, which often causes higher cost per watt. Meanwhile the power of single emitters with 100µm emitter size for direct coupling increased dramatically, which also pushed a new generation of wide stripe emitters or multi emitters (ME) of up to 1000µm emitter size respectively "minibars" with apertures of 3 to 5mm. The advantage of this emitter type compared to traditional bars is it's scalability to power levels of 40W to 60W combined with a small aperture which gives advantages when coupling into a fiber.We show concepts using this multiple single emitters for fiber coupled systems of 25W up to 40W out of a 100µm fiber NA 0.22 with a reasonable optical efficiency. Taking into account a further efficiency optimization and an increase in power of these devices in the near future, the EUR/W ratio pushed by the fiber laser manufacturer will further decrease.Results will be shown as well for higher power pump sources. Additional state of the art tapered fiber bundles for photonic crystal fibers are used to combine 7 (19) pump sources to output powers of 100W (370W) out of a 130µm (250µm) fiber NA 0.6 with nominal 20W per port. Improving those TFB´s in the near future and utilizing 40W per pump leg, an output power of even 750W out of 250µm fiber NA 0.6 will be possible. Combined Counter-and Co-Propagated pumping of the fiber will then lead to the first 1kW fiber laser oscillator.

GaAs-Based High Power Diode Laser

“…Table1.The development of the international high power single emitter [1][2][3] Emitting To further improve the laser output power, monolithic integration technology will be used to make more than a dozen emitters be a new laser diode array (called cm bar), its output power can be reached to kilowatts, shown in Table 2. In terms of Ultra-high power Bar, Spectra Physics with 87% fill factor (65 emitters, each light emitting width 125µm ,150µm length cavity length 5mm), using double-sided cooling technology (the water temperature reaches 5 ° C)wavelength of 808nm, 940nm, 980nm with maximum output power of 800W, 1010W, 950W, the maximum electro-optical conversion efficiency were 54.3%, 67.4%, 70% [8].…”

100-W 105-μm 0.15NA fiber coupled laser diode module

“…Traditional fiber coupled diode lasers have been based either on bars or fiber coupled single emitters 1,2,3,4 . In bar-based systems, the asymmetric beam quality in the fast and slow axis requires the use of expensive micro-optical beam shaping systems.…”