Akira Watanabe invented a specially designed nozzle in 1989, which generates ultra thin liquid film. As shown in the picture, the generated uniform liquid film exhibits optical interference pattern by which one can measure film thickness accurately.
The liquid-film nozzle originally developed as a key component for stabilization of femtosecond dye laser. Although it has not been used for a long time after advent of solid-state laser, Watanabe revived the liquid-film nozzle in 2009, in application of terahertz time-domain spectroscopy (THz-TDS) to liquid sample measurements.
In 2015, FEMTO deployments, Inc. started utilizing this technology in a contamination-free, disposable cartridge system for THz-TDS measurement, for wider commercialization of THz technologies.