We have been developing a detection system using lasers for foreign materials in some foods such as raisins, tomatoes, and grapes. Here we describe experimental results required for constructing the detection system. We have observed that some foreign materials mixed in raisins could be discriminated by taking laser emission reflectance ratios at appropriately chosen two laser wavelengths. Based on the experimental results, a prototype of the foreign food detection system has been produced.

We have been developing the vacuum ultraviolet (VUV) light sources and novel applications using such short wavelength emission sources. High quality amorphous Si thin films were successfully produced at room temperature as a result of photo-dissociation of SiH 4 gas by using an Ar 2 * excimer lamp irradiation at 126 nm. To enhance such novel VUV processing applications, a compact VUV amplifier at 126 nm was developed by use of the optical-field-ionization (OFI) electrons. The gain-length product around 5 was obtained as a result of the optical feedback by using a VUV mirror. This amplifier was operated in a table-top size with a high repetition rate up to several kHz, which should be appropriate for any process applications. We also describe the schematic concept of the ultrashort pulse high-intensity VUV laser system at 126 nm with a pulse width of 100 fs.

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