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UID:20260522T221036EDT-1367lnDeX2@132.216.98.100
DTSTAMP:20260523T021036Z
DESCRIPTION:Abstract\n\n \n\nHigh-power fiber lasers (HPFL) based on Ytterb
 ium-doped fibers are widespread in metal processing for cutting\, drilling
 \, and welding. However\, the power scaling of HPFLs is limited by factors
  of stimulated Raman scattering (SRS) and transverse mode instability (TMI
 ). This thesis has investigated novel components and strategies mitigate t
 hese detrimental effects.\n\nFirst\, we demonstrate an HPFL with chirped a
 nd tilted fiber Bragg grating (CTFBG) inserted inside the gain medium for 
 an improved SRS threshold of 1.8 kW. In comparison\, the insertion of a CT
 FBG after the gain medium only increases SRS threshold of the HPFL from 1.
 54 kW to 1.64 kW. Furthermore\, a broadened SRS-rejection band is achieved
  by the design of a cascade CTFBG. The intra-gain medium insertion of the 
 cascade CTFBG further enhances the SRS threshold to 2 kW.\n\nSecond\, we d
 emonstrate an experimental optimization on master-oscillator power-amplifi
 er lasers with an SRS filter inserted in between the X m long oscillator a
 nd the (40-X) m long amplifier stage\, where X takes values of 10\, 20\, 3
 0 and 40 m. Results show that the insertion of an SRS filter when X=30 m l
 eads to the largest output power of 2 kW. When an SRS filter is inserted a
 fter the oscillator with X≤30 m\, SRS threshold is increased but at the co
 st of reducing the power conversion efficiency (PCE). The insertion of an 
 SRS filter when X>30 m results in a significant decrease in PCE that const
 rains the power scaling.\n\nThird\, we present the first pump recycler for
  kW HPFL. The pump recycler is a pump-and-signal (6+1)×1 tapered fiber bun
 dle with pump fibers being spliced in pairs. 78% of the cladding pump ligh
 t entering the pump recycler can be recirculated back to the cladding. Com
 pared to a 40 m long HPFL that has PCE=73% and SRS threshold=1.54 kW\, the
  pump-recycled 20 m HPFL has PCE =70.5% and SRS threshold of 2.78 kW\, sho
 wing an 80% improvement in SRS threshold.\n\nLast\, we demonstrate a forwa
 rd-pump HPFL with record high power of 3 kW. SRS and TMI are simultaneousl
 y suppressed thanks to the combination of the 78% pump recycler and the pu
 mping wavelength at 915 nm. Besides\, the gain fiber lengths of the oscill
 ator and amplifier are experimentally redistributed. It shows a 19% increa
 se in the TMI threshold by shortening the length of the oscillator from 20
  m to 5 m.\n
DTSTART:20230621T180000Z
DTEND:20230621T200000Z
LOCATION:Room 603\, McConnell Engineering Building\, CA\, QC\, Montreal\, H
 3A 0E9\, 3480 rue University
SUMMARY:PhD defence of Weixuan Lin – Novel components and strategies to red
 uce nonlinear impairments of high-power fiber lasers
URL:/ece/channels/event/phd-defence-weixuan-lin-novel-
 components-and-strategies-reduce-nonlinear-impairments-high-power-348740
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