Theses
< 2020>
2020-02-17
SANDRA DE VEGA
2020-02-21
ESTHER GELLINGS
2020-03-26
NICOLA DI PALO
2020-03-30
ANGELO PIGA
2020-06-08
VIKAS REMESH
2020-06-23
DAVID ALCARAZ
2020-06-30
GERARD PLANES
2020-07-09
IRENE ALDA
2020-07-16
ALBERT ALOY
2020-07-27
MARIA SANZ-PAZ
2020-10-08
ZAHRA RAISSI
2020-11-17
ZAHRA KHANIAN
2020-11-27
PAMINA WINKLER
2020-12-02
BIPLOB NANDY

Development and Study of Novel Mid-Infrared Frequency Conversion Sources



BIPLOB NANDY
December 2nd, 2020 BIPLOB NANDY Optical Parametric Oscillators
ICFO-The Institute of Photonic Sciences


Tunable narrow-linewidth and broadband laser sources in the mid-infrared (mid-IR) wavelength range are extremely desirable in all time scales for their several useful applications in spectroscopy, imaging, optical communication and medical sciences to name a few. The one very important application of high-power tunable narrow-linewidth mid-IR laser sources in the 2 µm wavelength range is the ability to pump cascaded mid-IR optical parametric oscillators (OPO) for generating tunable wavelengths beyond 4 µm using semiconductor nonlinear crystals such as ZnGeP2 (ZGP) or orientation patterned GaAs (OP-GaAs). These crystals have very good linear and nonlinear optical properties along with good transparency beyond 4 µm wavelengths unlike oxide-based materials such as MgO:PPLN which have strong multi phonon absorption beyond 4 µm wavelengths. However, both ZGP and OP-GaAs cannot be pumped by commercially available 1 µm lasers due to linear and nonlinear absorptions below~2 µm wavelengths. In this thesis, we have demonstrated some very useful high-power narrow linewidth tunable 2 µm nanosecond and picosecond high-repetition-rate sources with very good spatial beam qualities. We have further demon strated a picosecond mid-IR idler-resonant MgO:PPLN based OPO with intra-cavity second-harmonic-generation (SHG). This helps in covering the essential wavelength gap between 1.064 µm and 1.45 µm when pumped by Yb- ber laser at 1.064 µm. This wavelength gap is generally not covered by MgO:PPLN based SROs that are signal resonant due to the material transparency of MgO:PPLN which doesn’t allow the idler wave to go above ~4 µm wavelength, thereby restricting the signal wave from reaching below ~1.45 µm.Due to the requirement of synchronous pumping, the OPOs typically tend to be relatively bulky and of large size, which can restrict its practical utility in space-constrained applications. We address this challenge by demonstrating a compact picosecond high-repetition rate singly resonant (SRO) with intracavity-mirror-retro-re ector ber (IMRF) that enables two-fold reduction in the form-factor. This IMRF OPO demonstrates a high wavelength tunability from~1.45 µm to~4 µm with high spectral brightness and exceptionally good output 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 (OPA) in MgO:PPLN with record high conversion e ciency of >59% without the requirement of any seed-laser. We have demonstrated a record-low pump threshold energy of 7.5 nJ which is remarkably small and opens a whole new area of research on single-pass frequency conversion devices based on OPG/OPA. Our system is highly tunable near~2 µm 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 picosecond OPO with record high output power and spectral bandwidth near~2 µm wavelength region. Such a device can be used as a high spectral brightness phase-locked super-continuum source for a huge array of applications.


PhD Thesis Defense, December 2, 2020. 15:00. Online (Teams)

Thesis Advisor: Prof Dr Majid Ebrahim-Zadeh
Thesis Co-advisor: Dr Chaitanya K. Suddapalli