Vacuum ultraviolet second-harmonic generation in NH4B4O6F crystal
Summary
The paper reports the experimental observation of second-harmonic generation (SHG) reaching the vacuum-ultraviolet (VUV) region using the fluorooxoborate crystal NH4B4O6F. This follows theoretical and materials-design work that flagged NH4B4O6F as a promising deep-ultraviolet (DUV) nonlinear optical material. The authors present crystal growth and optical characterisation, demonstrate VUV frequency conversion, and compare the material’s practical advantages with existing VUV/DUV crystals.
Key Points
- Experimental SHG into the vacuum-ultraviolet has been realised in NH4B4O6F, validating prior predictions that this fluorooxoborate family is promising for DUV/VUV nonlinear optics.
- The work connects materials design (fluence-oxoborates, beryllium-free alternatives) with practical optical measurements and phase-matching tests.
- Crystal growth and basic optical characterisation (transparency, phase-matching behaviour and nonlinear response) are reported, supporting NH4B4O6F as a viable candidate for compact VUV sources.
- NH4B4O6F offers a beryllium-free route compared with some historical VUV crystals, reducing toxicity and fabrication complications associated with layered growth habits.
- Applications include tabletop VUV/DUV lasers for spectroscopy, angle-resolved photoemission (ARPES), photolithography research and other scientific instruments that need coherent VUV light.
- Further work will be needed on scaling crystal size, enhancing conversion efficiency, and quantifying laser-damage thresholds for high-power operation.
Context and relevance
This result sits at the intersection of nonlinear optics and materials chemistry. For years, crystals such as KBBF and related borate fluorides dominated DUV/VUV work but suffered from growth or toxicity issues. Fluorooxoborates—including NH4B4O6F—have been proposed as next-generation, beryllium-free alternatives; demonstrating VUV SHG in NH4B4O6F is an important experimental step that moves those proposals from theory and small-signal tests toward usable VUV devices. The paper therefore matters to researchers building compact VUV sources and to those tracking safer, more manufacturable NLO crystals for scientific and industrial lasers.
Author style
Punchy: This is a clean, attention-grabbing advance — it confirms a materials-design route (fluorooxoborates) and shows actual VUV conversion, not just simulations or predictions. If you care about enabling practical VUV lasers, read the methods and optical-characterisation sections closely.
Why should I read this
Quick, informal: If you want compact VUV light without the headache of tricky or toxic crystals, this is the one to skim. The paper actually demonstrates SHG in a beryllium-free fluorooxoborate, so it’s a real step towards safer, more scalable VUV sources — worth a read if you work in laser development, spectroscopy or VUV applications.
Source
Article Date: 2026-01-28
Article URL: https://www.nature.com/articles/s41586-025-10007-z
Article Image: (not provided)