Optics2026-04-261 minarXiv:2604.23499expressA Laser That Shines Without GapsAn ordinary laser emits narrow lines, like a string that sounds only one note. For spectroscopy, this is inconvenient: if a substance absorbs light between the lines, you might miss it.Urban Senica·Michael A. Schreiber·Mattias Beck·Christian Jirauschek·Jérôme Faist·Giacomo Scalariinvention of the laserAlbert EinsteinCharles TownesDavid WinelandlaserSpectral Analysiscoherent stateX-ray radiationspectrometer👍👎☆SimplePopularAdvanced