We investigated femtosecond laser inscription of IG2 waveguides and photonic structures for mid-infrared applications. 1 x 4 beamsplitters are realized, achieving normalized splitting ratios of more than 90% among the four arms. In addition, both fundamental mode and multimode guiding in the mid-IR regime at 4.55 µm are demonstrated. The Mid-IR waveguiding properties at 4.55 µm will be presented for both single-mode and multimode waveguides with as low as 0.8 dB/cm propagation loss for the single-mode guiding and controllable mode field diameter.
This work is supported by the US National Aeronautics and Space Administration under STTR Contracts 80NSSC20C0027, 80NSSC21C0638, and 80NSSC22PA936.
We compare the double-track waveguide lasers inscribed inside Nd:YAG crystals using femtosecond laser pulses at 515 nm and 1030 nm. For both source wavelengths, the highly efficient, continuous wave, single mode and stable lasing at 1064 nm has been achieved in a monolithic cavity formed by the crystal with dielectric coatings at the input and output end facets. In addition to source wavelength, the lasing performance and guiding properties for track separations of 15 µm and 30 µm are compared.
Calcium Fluoride (CaF2) was identified among the first host crystals for active laser media. However, due to the need of charge compensation of Nd3+-doped fluorite crystal structures, other host materials like YAG, oxide and fluorite glasses were preferred over the years. Recent developments made on ytterbium-doped alkaline-earth fluorides have shown that it is possible to have better scalability of crystal growth, very high thermal conductivity, high laser-induced damage threshold, longer emission lifetime, lower nonlinear refractive index and large emission wavelength tuning range. Due to these reasons, Yb-doped CaF2 has once again proved to be a competitive material for high-energy and high-power operations.
Waveguides confine light propagation resulting in reduced lasing thresholds and enhanced laser efficiencies. By properly managing the three-dimensional translation of the focal volume of pulsed lasers, it is possible to create waveguides and other 3D structures inside crystals. Recently, depressed cladding waveguides written inside CaF2 were reported. In this work, we will present the first, to the best of our knowledge, double track waveguides inscribed inside doped and undoped CaF2 crystal with different pulse energies. Waveguide characterization, determination of mode-field diameter, analysis of polarization dependent guiding and also direct refractive index change measurements of the waveguides were performed and will be presented. Additionally, single pass gain and lasing experiments will be demonstrated both theoretically and experimentally.
We detail the full characterization of the anisotropy of the absorption properties of two different Yb-doped monoclinic borate compounds under polarized light. The studied crystals are Li6(Gd)0.75Yb0.25(BO3)3 and Li6Y0.75Yb0.25(BO3)3, respectively, and were grown by the Czochralski method. We focused on the study of their absorption at the zero line transition as a function of the polarization direction of the incident light for two different crystal cuts of each compound. We discuss the different eigenframes that must be considered in these materials, due to their monoclinic character, as well as the optimum crystal orientation for the considered absorption and show the potential influences when used as laser materials.
In this contribution we detail the full characterization of the anisotropy of the absorption properties of two different Yb-doped monoclinic borate compounds under polarized light. The studied crystals are Li6(Gd)0.75Yb0.25(BO3)3 and Li6Y0.75Yb0.25(BO3)3, respectively, grown by the Czochralski method. We focused on the study of their absorption at the zero line transition as a function of the polarization direction of the incident light for two different crystal cuts of each compound. We discuss the different Eigen frames that must be considered in these materials due to their monoclinic character, as well as the optimal crystal orientation for the considered absorption and the potential influences when used as laser materials.
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