Hasse, Kore

We show that the inscription velocity of fs-laser written structures in YAG crystals can be significantly improved by the use of MHz repetition rates for the writing process. Using a 10 MHz inscription laser, record high writing velocities up to 100 mm/s are achieved. Also, the selective etching process is accelerated using a diluted mixture of 22% H3PO4and 24% H2SO4. The diluted mixture enables selective etching of up to 9.6 mm long, 1 μm wide and 18 μm high microchannels in 23 days. The etching parameter D of 11.2 μm2/s is a factor of 3 higher than previously reported and the selectivity is even increased by an order of magnitude. c 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.

A neodymium (Nd) doped lithium-niobate-on-insulator (LNOI) was fabricated from a lithium niobate (LN) substrate diffusion-doped with Nd prior to the LNOI fabrication process. Diffusion doping enables the fabrication of differently doped regions on a single LNOI substrate, a key advantage for future applications in highly integrated photonics. Fluorescence spectra, emission cross-section, fluorescence lifetime, and small-signal gain of Nd:LNOI were determined for the first time to our knowledge and compared with data published for diffusion-doped ridge or channel waveguides in LN substrates. For an 11 mm-long sample, we achieve a small-signal gain for p (s) polarization of about 14 (10) dB when pumping with a Ti:Sapphire laser, which is promising for future active components in Nd:LNOI like amplifiers and lasers.