Continuous-wave frequency tripling and quadrupling by simultaneous three-wave mixings in periodically poled crystals: application to a two-step 1.19-10.71-microm frequency bridge

We observed cw third-harmonic generation in a periodically poled LiNbO(3) crystal by cascading optimally phase-matched second-harmonic and sum-frequency generation. Other processes, such as fourth-harmonic generation, are allowed by the flexibility of quasi-phase matching. We demonstrate a divide-by-nine (1.19- 10.71-microm) frequency chain that uses only two lasers.     

Certified reference materials chlorobiphenyls (IUPAC nos 28, 52, 101, 118, 153 and 180) in dried sewage sludge — CRM 392

Summary Six chlorinated biphenyls — CB IUPAC nos 28, 52, 101, 118, 153 and 180 — have been certified in a dried sewage sludge of a mainly residential area. After a thorough preparation the material has been studied for the within- and between bottle homogeneity as well as for its long term stability. The certification of the CBs in the dried sludge has been performed with 18 well trained laboratories, applying different methods of extraction, clean-up and chromatographic separation. ECD has been used as final detection and MS to verify the peak identities. All methods for the homogeneity and stability studies as well as those used for the certification campaign are described. CB 138 could not be certified as it co-eluted with CB 183. The major precautions followed by the participants to ensure traceability of the results to the basic units are also discussed. They highlight the level of quality control requested from certifying laboratories. The certified values were obtained after a technical discussion of the methods followed and of each of the individual results. They are given together with the indicative value for CB 138+CB 163.