Large mode area double-clad ytterbium-doped spun tapered fiber

We performed a comparative study of Yb-doped double-clad large mode area (MFDD31 _m) spun tapered fibers with different pitch lengths. A novel type of spun tapered fibers with constant pitch lengths of 7.5, 15, and 30 mm, internal birefringence as low as ∼10-8, and perfect output beam quality (M2 < 1.2) has been manufactured and investigated. We demonstrated the efficient direct amplification of a picosecond pulsed signal (95 ps/100 MHz, 1064 nm) in the spun active tapered fiber with optimized geometry providing an average output power of 71W(gain 32 dB, 74% slope efficiency). Efficient green light generation (∼D532 nm) with 17Waverage power (1.7 μJ) and 80 pm linewidth was demonstrated using the developed master oscillator power amplifier system.acceptedVersionPeer reviewe

Active tapered double-clad fiber with low birefringence

We addressed the problem of a state of polarization (SOP) drift caused by heating under intense clad pumping in different types of active tapered double-clad fibers. We investigated experimentally the variations of the SOP and degree of polarization (DOP) under clad pumping in polarization-maintaining (PANDA type) and regular (non-PM) Yb-doped double-clad large mode area tapered fibers. We discovered that the birefringence of active fibers is highly dependent on the launched pump power. To solve the problem of the SOP drift in active large mode are fibers, we, for the first time to the best of our knowledge, presented an active double-clad fiber with low intrinsic birefringence as a gain medium. An Yb-doped spun tapered double-clad fiber (sT-DCF) with intrinsic birefringence as low as 1.45×10−8 was manufactured and experimentally studied. We have proved experimentally that the DOP and SOP remains more stable in sT-DCF with increasing pump power compared to PM PANDA-type and regular non-PM tapered double-clad fibers. In particular, the SOP drift in sT-DCF is almost one order of magnitude less than in other tapered fibers, while the DOP drift in sT-DCF is comparable with the drift in PANDA-type fiber and one order of magnitude less than in the non-PM tapered fiber. An active sT-DCF showing efficient amplification was demonstrated in an all-fiber-based picosecond master-oscillator power-amplifier scheme. The system delivered 50 ps pulses at 1040 nm with an average power of 50 W, 34 dB gain, 26 µm MFD and perfect beam quality.publishedVersionPeer reviewe

Large mode area double clad ytterbium tapered fiber with circular birefringency

We demonstrated, for the first time to our best knowledge, an active tapered double clad fiber with circular birefringence and 35 μm core diameter. The output radiation had perfect beam quality (M2=1.18/1.1) and linearly polarized light with 15 dB of PER. The developed double clad active fiber was investigated for amplification of picosecond pulses in allfiber MOPA system. The MOPA system delivered 50 ps pulses with 55 W of the average power revealed 34.4 dB gain of the booster amplifier.publishedVersionPeer reviewe

Large mode area double-clad ytterbium-doped tapered fiber with low birefringence

We developed ytterbium-doped double-clad large mode area (MFD = 30 µm) spun tapered fibers with low internal birefringence and perfect beam quality (M2 < 1.2). Picosecond MOPA system (95ps/100 MHz, 1064 nm) based on proposed active tapered fiber with output average power of 64 W (gain 32 dB) is demonstrated.publishedVersionPeer reviewe

Random Laser Based on Ytterbium-Doped Fiber with a Bragg Grating Array as the Source of Continuous-Wave 976 nm Wavelength Radiation

A random narrow-linewidth lasing at a wavelength of 976 nm was obtained in an ytterbium-doped germanophosphosilicate fiber with an array of weakly reflecting fiber Bragg gratings (FBGs). A random laser cavity was formed by implementing the standard phase mask method of FBG inscription directly during the fiber drawing process. The UV radiation pulses of a KrF excimer laser (248 nm wavelength) synchronized with the fiber drawing speed were used to fabricate the in-fiber array of hundreds of similar FBGs. The developed laser’s slope efficiency in the backward-pumping scheme was measured as high as 33%. The stable continuous-wave operation mode of the laser was detected. The magnitude of the laser power fluctuations depends linearly on the cavity length. The random laser cavity modified with a single highlyreflected (90%) FBG demonstrates significantly better power stability and higher slope efficiency than the same one without an FBG

Random Laser Based on Ytterbium-Doped Fiber with a Bragg Grating Array as the Source of Continuous-Wave 976 nm Wavelength Radiation

A random narrow-linewidth lasing at a wavelength of 976 nm was obtained in an ytterbium-doped germanophosphosilicate fiber with an array of weakly reflecting fiber Bragg gratings (FBGs). A random laser cavity was formed by implementing the standard phase mask method of FBG inscription directly during the fiber drawing process. The UV radiation pulses of a KrF excimer laser (248 nm wavelength) synchronized with the fiber drawing speed were used to fabricate the in-fiber array of hundreds of similar FBGs. The developed laser&rsquo;s slope efficiency in the backward-pumping scheme was measured as high as 33%. The stable continuous-wave operation mode of the laser was detected. The magnitude of the laser power fluctuations depends linearly on the cavity length. The random laser cavity modified with a single highlyreflected (90%) FBG demonstrates significantly better power stability and higher slope efficiency than the same one without an FBG