BEGIN:VCALENDAR VERSION:2.0 PRODID:Icfo X-PUBLISHED-TTL:P1W BEGIN:VEVENT UID:69db6d7f83cdd DTSTART:20220309T100000Z SEQUENCE:0 TRANSP:OPAQUE LOCATION:ICFO Auditorium and Online (Teams) SUMMARY:ICFO | SUKEERT CLASS:PUBLIC DESCRIPTION:Tunable laser sources in different spectral regions are of inte rest for a variety of applications including spectroscopy\, trace gas sens ing\, medical diagnostics\, LIDAR and material processing. Existing lasers have limited tunability and many spectral regions continue to remain inac cessible to lasers due to lack of suitable gain media. Nonlinear frequency conversion is a viable approach to cover such difficult spectral regions in the visible\, near and mid-infrared (mid-IR).\nOptical parametric oscil lators (OPO) can provide wide wavelength tunability with high output power s in good beam quality across continuous-wave (cw)\, nanosecond and ultraf ast picosecond and femtosecond time-scales. With the development of quasi- phase-matched (QPM) nonlinear materials in fan-out grating structure\, wid e wavelength tuning is possible at a fixed temperature\, enabling the deve lopment of rapidly tunable devices for practical applications. Difference- frequency-generation (DFG) is also an attractive approach for generating h igh powers in the mid-IR in a single-pass scheme.\nIn this thesis\, we hav e developed second-order nonlinear frequency conversion sources based on n anosecond and cw OPOs and cw DFG. Widely tunable green-pumped OPOs have be en developed by using fan-out grating structure for the first time in diff erent nonlinear materials\, and a high-power cw source in the mid-IR has b een developed by exploiting DFG. The sources developed in this thesis cove r a wavelength range spanning 677-2479 nm. One of the OPOs developed in th is work has also been deployed in an industrial environment in a device ch aracterization setup.\nIn green-pumped OPOs\, we demonstrate a widely tuna ble cw OPO based on PPKTP in a fan-out grating structure. The OPO is conti nuously tunable across 742-922 nm in the signal\, and 1258-1884 nm in the idler. Resonant wave output coupling has been deployed to extract useful s ignal power and reduce the thermal load\, and the OPO can deliver up to 1. 65 W of total output power. The use of output coupling results \; in s uperior performance of the OPO over pure singly-resonant oscillator (SRO) configuration.\nWe also develop the first green-pumped OPO based on MgO:cP PLT. Continuous wavelength tuning across 689-1025 nm in the signal and 110 6-2336 nm in the idler at room temperature has been achieved in the nanose cond OPO by using a fan-out grating structure. The OPO can provide up to 1 31 mW of average output power at 25 kHz \; repetition rate\, and the i dler passive power stability is 3.9% rms over 30 minutes.\nA cw OPO based on MgO:PPLN in a fan-out grating design is then described. The OPO is cont inuously tunable across 813-1032 nm in the signal and 1098-1539 nm in the idler. A short crystal length and signal output coupling are used to minim ise thermal effects\, and the OPO can generate up to 710 mW of total outpu t power with signal and idler passive power stabilities better than 2.8% r ms and 1.8% rms\, respectively over 1 hour and signal M^2<\;1.1.\nAs a p art of an industrial internship\, a cw green-pumped MgO:PPLN OPO is develo ped at Radiantis. The OPO is used as the input light source of a device ch aracterization setup to test sensors for the aerospace sector. Compared to the existing light source\, using the OPO results in orders-of magnitude- higher response of the InGaAs sensor\, leading to a more precise and accur ate characterization\, and \; lower measurement error\, thus improving the device evaluation process.\nFinally\, we demonstrate a high-power cw source at 2.26 &mu\;m using the DFG process. The source can deliver up to 3.84 W of output power at 2262 nm\, with a power stability better than 0.6 % rms over 1 hour\, in a Gaussian mode profile with M^2<\;1.2.\n \;\ nThesis Director: Prof Dr. Majid Ebrahim-Zadeh\nThesis Co-Director: Dr. Ch aitanya Kumar Suddapalli\n \; DTSTAMP:20260412T100135Z END:VEVENT END:VCALENDAR