Volatile organic compound photoionization utilizing tunable quasi-monochromatic vacuum ultraviolet down to 120 nm obtained by third harmonic generation from a suspended dielectric nanomembrane

We present a table-top light source of continuously tunable quasi-monochromatic vacuum ultraviolet (VUV) coupled to a custom-built photoionization detector and demonstrate its capacity to induce photoionization in trace levels of volatile organic compounds at ambient saturated vapor pressure. A high-power pulsed monochromatic laser powers an optical parametric amplifier that subsequently feeds into two materials inducing consecutively second harmonic generation (SHG) and third harmonic generation (THG). While the SHG is obtained in a bulk BBO crystal, the THG originates from suspended SiO₂ nanomembranes. We demonstrate the photoionization of ethanolamine and eucalyptol at THG pump wavelengths of 390 nm and 360 nm respectively, providing evidence of VUV light generation at 130 nm and down to 120 nm, going beyond the state-of-the-art of demonstrated VUV generation in dielectric nanomembranes. This proof-of-concept system highlights the transformative potential of dielectric nanomembranes in facilitating compact, efficient and tunable VUV light sources for spectroscopy and sensor technology without the necessity of vacuum technology.