Browsing by Subject "Measurement by laser beam"

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Open Access
1.06μm-1.35μm coherent pulse generation by a synchronously-pumped phosphosilicate Raman fiber laser
(OSA, 2017) Elahi, Parviz; Makey, Ghaith; Turnalı, Ahmet; Tokel, Onur; İlday, Fatih Ömer
Summary form only given. Rare-earth-doped fiber lasers are attractive for microscopy and imaging applications and have developed over the past decades rapidly. They are unable to cover near-infra-red region entirely and therefore Raman and parametric process are promising for producing new wavelengths which are out of emission band of the current fiber lasers. Here, we demonstrate a synchronously-pumped Raman laser system for producing coherent signals spanning from 1.06 μm to 1.35 μm. The laser system comprises a passively-mode-locked oscillator, two stages of amplifier and a phosphosilicate Raman oscillator. The schematic of experimental setup is shown in Fig. 1(a). A mode locked oscillator operating at 37 MHz is using as a seed source. The output pulse duration and central wavelength are 6 ps and 1065 nm, respectively. 6 mW output from oscillator is launched to pre amplifier comprises 85-cm long Yb 401-PM pumped by a single mode diode through a PM wavelength division multiplexer (WDM). The power amplifier consists of a 3.5-m long Yb 1200-DC-PM with 6 μm core diameter and 125 μm cladding diameter pumped by a temperature stabilized, high power multimode diode laser via a multimode pump-signal combiner (MPC). A 30/70 coupler is employed for delivering pump signal at 1060 nm to the Raman oscillator comprises 4.2-m long ph-doped fiber. To synchronize pump and Raman and achieve coherent pulses, we adjust the length of cavity by a precise translation stage. By using proper filter inside the Raman cavity, different wavelengths are achieved.
Open Access
An all-fiber ultra-low numerical aperture high power fiber MOPA system with an output power above 500 W
(Institute of Electrical and Electronics Engineers Inc., 2019) Midilli, Yakup; Ortaç, Bülend
Optical fiber technology has been developed dramatically in the last two decades. Especially, the invention of the Large Mode Area (LMA) fibers has made a great impact, and consequently the power scale of the fiber lasers started to increase exponentially [1]. However, at a certain point this increase has been saturated due to the non-linear effects such as Stimulated Raman Scattering (SRS) and Thermal Modal Instability (TMI). Therefore, a new approach has been proposed to mitigate these so called problems by decreasing the numerical aperture (NA) of the LMA active fiber so that it behaves like an intrinsically single mode fiber. In the literature, an active fiber having ultra-low (<; 0.04) NA, is proposed [2, 3] in 2009; and finally, the highest power, which is 4.3 kW, was demonstrated in 2017 [4]. However, all of these works based on free space orientation. In this letter, we demonstrate all-fiber and monolithic version of the high power low NA fiber laser system based on an Yb-doped active fiber having 26 μm/410 μm core/cladding diameters respectively with a NA of 0.032 which has also been verified experimentally.