BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69f24217c85ef DTSTART:20201202T140000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:ICFO Auditorium and Online (Teams) SUMMARY:ICFO | BIPLOB NANDY CLASS:PUBLIC DESCRIPTION:Tunable narrow-linewidth and broadband laser sources in the mid -infrared (mid-IR) wavelength range are extremely desirable in all time sc ales for their several useful applications in spectroscopy\, imaging\, opt ical communication and medical sciences to name a few. The one very import ant application of high-power tunable narrow-linewidth mid-IR laser source s in the 2 µ\;m wavelength range is the ability to pump cascaded mid- IR optical parametric oscillators (OPO) for generating tunable wavelengths beyond 4 µ\;m using semiconductor nonlinear crystals such as ZnGeP2 (ZGP) or orientation patterned GaAs (OP-GaAs). These crystals have very go od linear and nonlinear optical properties along with good transparency be yond 4 µ\;m wavelengths unlike oxide-based materials such as MgO:PPLN which have strong multi phonon absorption beyond 4 µ\;m wavelengths. However\, both ZGP and OP-GaAs cannot be pumped by commercially available 1 µ\;m lasers due to linear and nonlinear absorptions below~2 µ \;m wavelengths. In this thesis\, we have demonstrated some very useful hi gh-power narrow linewidth tunable 2 µ\;m nanosecond and picosecond hi gh-repetition-rate sources with very good spatial beam qualities. We have further demon strated a picosecond mid-IR idler-resonant MgO:PPLN based OP O with intra-cavity second-harmonic-generation (SHG). This helps in coveri ng the essential wavelength gap between 1.064 µ\;m and 1.45 µ\;m when pumped by Yb- ber laser at 1.064 µ\;m. This wavelength gap is g enerally not covered by MgO:PPLN based SROs that are signal resonant due t o the material transparency of MgO:PPLN which doesn't allow the idler wave to go above ~4 µ\;m wavelength\, thereby restricting the signal wave from reaching below ~1.45 µ\;m.Due to the requirement of synchronous pumping\, the OPOs typically tend to be relatively bulky and of large siz e\, which can restrict its practical utility in space-constrained applicat ions. We address this challenge by demonstrating a compact picosecond high -repetition rate singly resonant (SRO) with intracavity-mirror-retro-re ec tor \; ber (IMRF) that enables two-fold reduction in the form-factor. This IMRF OPO demonstrates a high wavelength tunability from~1.45 µ\; m to~4 µ\;m with high spectral brightness and exceptionally good outp ut beam quality. In our attempt to further reduce the size and complexity of nonlinear frequency conversion sources\, we have demonstrated the \ ; rst single-pass optical parametric generation (OPG) and ampli cation (OP A) in MgO:PPLN with record high conversion e ciency of >\;59% without th e requirement of any seed-laser. We have demonstrated a record-low pump th reshold energy of 7.5 nJ which is remarkably small and opens a whole new a rea of research on single-pass frequency conversion devices based on OPG/O PA. Our system is highly tunable near~2 µ\;m region with >\;8 W of single-pass output power while pumped with~14 W of pump power at 1064 nm. Finally\, in this thesis\, we have demonstrated the rst phase-locked picos econd OPO with record high output power and spectral bandwidth near~2 &mic ro\;m wavelength region. Such a device can be used as a high spectral brig htness phase-locked super-continuum source for a huge array of application s. DTSTAMP:20260429T173831Z END:VEVENT END:VCALENDAR