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VERSION:2.0
PRODID:Icfo
X-PUBLISHED-TTL:P1W
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UID:69d4b36c0e557
DTSTART:20251217T090000Z
SEQUENCE:0
TRANSP:OPAQUE
LOCATION:Elements Room and Online (Teams)
SUMMARY:ICFO | OMID KOKABEE
CLASS:PUBLIC
DESCRIPTION:In a synchronously pumped optical parametric oscillator (SPOPO)
 \, the pump laser pulses are timed to arrive at the OPO crystal in synchro
 nism with the circulating signal pulses\, enabling efficient energy transf
 er and the generation of high-power\, high-repetition-rate\, widely tunabl
 e\, ultrashort pulses. This synchronization allows SPOPOs to achieve high 
 conversion efficiencies and excellent temporal\, spectral and spatial char
 acteristics. The research presented in this thesis focuses on the developm
 ent of high-power ultrafast SPOPOs at repetition rates from 76 MHz to as h
 igh as 1 GHz covering the visible to mid-infrared spectrum.\nFirst\, we pr
 esented a method for efficient generation of femtosecond pulses with wide 
 tuning in the red spectrum using a periodically-poled LiNbO3 (PPLN) as the
  nonlinear gain crystal combined with bismuth triborate (BIBO) for interna
 l frequency doubling. High nonlinear gain in both PPLN and BIBO\, combined
  with collinear pumping\, results in a conversion efficiency of 17.2%\, pr
 oviding tunable coverage across the 665-785 nm range. The large spectral a
 cceptance in PPLN and BIBO facilitates convenient wavelength tuning by adj
 usting the SPOPO cavity delay\, without modifying other parameters such as
  PPLN crystal temperature\, BIBO phase-match angle\, or pump wavelength.\n
 Further\, we reported the implementation of a femtosecond SPOPO operating 
 at an approximate repetition rate of 1 GHz using a novel technique to enha
 nce the MHz pump repetition rate. The system uses PPLN as the nonlinear me
 dium and features an innovative cavity design exceeding the fundamental sy
 nchronous cavity length. Driven by a Kerr-lens mode-locked (KLM) Ti:sapphi
 re laser operating at 76 MHz\, the system generates near-transform-limited
  pulses at the 13th harmonic of the pump laser frequency\, corresponding t
 o 988 MHz. Internal dispersion compensation using a pair of SF11 prisms in
  the linear cavity configuration achieves stable near-transform-limited ou
 tput signal pulses up to the 14th harmonic of the pump laser repetition ra
 te\, corresponding to 1064 MHz.\nLater\, we introduced a universal method 
 for maximizing output power from optical oscillators through interferometr
 y. By incorporating an antiresonant ring interferometer into one arm of th
 e oscillator cavity\, continuously variable output coupling is achieved ov
 er a broad spectral range and under any operating conditions. Demonstrated
  using a femtosecond SPOPO\, this technique enables continuously adjustabl
 e output coupling from 1% to 60%. At an optimized output coupling of appro
 ximately 30%\, around 200 mW of power is extracted\, more than double the 
 output compared to a conventional output coupler with around 4%. The metho
 d maintains a Gaussian beam profile and near-transform-limited pulse durat
 ions.\nAdditionally\, we detailed the development and characterization of 
 a highly efficient and stable picosecond SPOPO system based on magnesium o
 xide-doped PPLN (MgO:PPLN)\, pumped by a ytterbium (Yb) fiber laser. The s
 ystem achieves exceptional performance in power output and conversion effi
 ciency\, with a total average power extraction of 11.7 W. This includes 7.
 1 W of signal radiation at 1.56 &mu\;m and 4.6 W of idler radiation at 3.3
 3 &mu\;m\, with a remarkable extraction efficiency of 73%. This performanc
 e is accompanied by superior spectral and spatial beam characteristics\, e
 xhibiting exceptional output power stability.\nWednesday December 17\, 10:
 00 h. \nElements Room and Microsoft Teams Meeting
DTSTAMP:20260407T073404Z
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