Focus Issue Introduction: Advanced Solid-State Lasers 2020

This Joint Issue of Optics Express and Optical Materials Express features 15 articles written by authors who participated in the international online conference Advanced Solid State Lasers held 13?16 October, 2020. This review provides a summary of the conference and these articles from the conference which sample the spectrum of solid state laser theory and experiment, from materials research to sources and from design innovation to applications.ASSL (Advanced Solid-State Lasers) is the international conference devoted to recent advances in both materials and sources aspects of solid state lasers. Materials encompasses advances in optics, materials science, condensed matter physics and chemistry relevant to the development, characterization and applications of new materials for lasers and photonics. These include crystals, glasses and ceramics, as well as functionalized composite materials, from fibers and waveguides to engineered structures with pre-assigned optical properties. Materials used for fabrication of basic laser components are also a core part of the conference. Coherent and high brightness radiation sources include lasers as well as pump and nonlinear devices from the THz through X-ray spectral regions. Emphasis is on advances in science and technology, for improved power, efficiency, brightness, stability, wavelength coverage, pulse width, cost, environmental