Digital interference microscopy and density reconstruction of picosecond infrared laser desorption at the water-air interface

Abstract

Material ablation and evaporation using pulsed infrared lasers pose promising approaches for matrix-free laser desorption ionization and in laser surgery. For the best results, key parameters such as laser wavelength, pulse duration, and pulse energy need to be carefully adjusted to the application. We characterize the dynamics at the water-air interface induced by a 10 ps infrared laser tuned to the water absorption band at 3 lm, a parameter set facilitating stress confined desorption for typical absorption depths in biological samples and tissue. By driving the ablation faster than nucleation growth, cavitation induced sample damage during the ablation process can be mitigated. The resultant explosive ablation process leads to a shock front expansion and material ejection which we capture using off-axis digital interference microscopy, an interference technique particularly useful for detecting the phase shift caused by transparent objects. It is demonstrated that the method can yield local density information of the observed shock front with a single image acquisition as compared to the usually performed fit of the velocity extracted from several consecutive snapshots. We determine the ablation threshold to be ð0:560:2Þ J cm À2 and observe a significant distortion of the central parts of the primary shock wave above approximately 2:5 J cm À2. The differences in plume shape observed for higher fluences are reflected in an analysis based on shock wave theory, which shows a very fast initial expansion.

Sample preparation free tissue imaging using Laser Desorption – Rapid Evaporative Ionisation Mass spectrometry (LD-REIMS)

“…While diathermal ablation involves macroscopic thermal damage including charring, UV laser desorption results in the excessive fragmentation of gaseous molecules and ions. In contrast, infrared lasers (especially short pulse width resonant mid-infrared lasers) transfer the molecular content of tissues into the gas phase efficiently and without significant thermal damage or fragmentation (35,36). These properties make the technique one of the most promising candidates for a universal tissue profiling method equally capable of tissue imaging as well as bulk or even in-vivo tissue analysis.…”

Enabling Cellular Resolution Molecular Pathology for Surgical Interventions Using Laser Desorption – Rapid Evaporative Ionization Mass spectrometry

“…While diathermal ablation involves macroscopic thermal damage including charring, UV laser desorption results in excessive fragmentation of gaseous molecules and ions. In contrast infrared lasers (especially short pulse width resonant mid-infrared lasers) transfer the molecular content of tissues into the gas phase efficiently and without notable thermal damage or fragmentation (34,(60)(61)(62). These properties make the technique one of the most promising candidates for a universal tissue profiling method equally capable of tissue imaging as well as bulk or even in vivo tissue analysis.…”

Picosecond infrared laser driven sample delivery for simultaneous liquid-phase and gas-phase electron diffraction studies

“… 41 In this regard, PIRL–DIVE represents a laser driven molecular beam with orders of magnitude higher number densities than electrospray or conventional molecular beams using differential pumping. 31,39,42,43 In principle, any size molecule can be introduced into both gas phase and nanoscale liquid domains with the same sample delivery system. In this regard, the PIRL–DIVE method is truly unique.…”