Ultrashort pulse propagation through depressed-cladding channel waveguides in YAG crystal: Spatio-temporal characterization

• Published in: Optics and laser technology Vol. 123; p. 105898
• Main Authors: Morales-Vidal, Marta, Sola, Íñigo J., Castillo, Gabriel R., R. Vázquez de Aldana, Javier, Alonso, Benjamín
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2020; Elsevier BV
• Subjects: Channeled waveguides; Cladding; Crystals; Femtosecond pulsed lasers; Frequency converters; Inhomogeneity; Irradiation; Lanterns; Optical waveguides; Phase measurements; Photonics; Pulse measurements; Pulse propagation; Spectral interferometry; Ultrafast optics; Wave propagation; Waveguide lasers; Pulse measurements; Phase measurements; Ultrafast optics; Spectral interferometry; Channeled waveguides
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2019.105898

•Dispersion effect in the propagation of pulses through cladding waveguides.•Spatio-spectral and -temporal structure of pulses at the output of waveguides.•A different behavior between mono-modal and multi-modal waveguides is reported. Inscription of optical waveguides by direct femtosecond laser irradiation has become a very versatile tool for the development of integrated photonic devices, such as waveguide lasers, frequency converters or photonic lanterns, among many others. The potential application of such devices for the control and manipulation of ultrashort pulses requires the precise knowledge of the temporal distortions that may be induced in the pulse propagation. Currently, research in this topic is scarce, and to our knowledge there is no previous experimental study on the spatio-temporal characterization at the output of waveguides inscribed inside crystals. Here, we have firstly fabricated depressed-cladding waveguides with different modal behavior in YAG crystal by direct femtosecond laser irradiation. Then, we implemented an experimental method based on the fiber coupler assisted spectral interferometry technique, that allows obtaining: (1) the temporal dispersion of a pulse at the output of an inscribed waveguide and, (2) full spatio-spectral and spatio-temporal characterization of the output of single-mode and multi-mode waveguides. Our results suggest that the main contribution to the pulse dispersion is due to the material dispersion. Moreover, we found that multimodal waveguides may induce an appreciable inhomogeneity in the temporal features of the pulses that needs to be taken into account in the design of complex devices.