High performance 1689-nm quantum well diode lasers

1689-nm diode lasers used in medical apparatus have been fabricated and characterized. The lasers had pnpn InP current confinement structure, and the active region consisted of 5 pairs of InGaAs quantum wells and InGaAsP barriers. Stripe width and cavity length of the laser were 1.8 and 300 pm, respectively. After being cavity coated. and transistor outline (TO) packaged, the lasers showed high performance in practice. The threshold current was about 13 +/- 4 mA, the operation current and the lasing spectrum were about 58 6 mA and 1689 +/- 6 nm at 6-mW output power, respectively. Moreover, the maximum output power of the lasers was above 20 mW.

A study of resonance electron capture ionization on a quadrupole tandem mass spectrometer

Procedures that allow the realization of resonance electron capture (REC) mode on a commercial triple-quadrupole mass spectrometer, after some simple modifications, are described, REC mass spectrometry (MS) and tandem mass spectrometry (MS/MS) experiments were performed and spectra for some compounds were recorded. In particular, the charge-remote fragmentation (CRF) spectra of [M - H](-) ions of docosanoic and docosenoic acids under low-energy collisionally activated dissociation (CAD) conditions were obtained, and showed that there were no significant differences for [M - H](-) ions produced at different resonances (i,e. for [M - H](-) ions with different structures). This observation was explained on the basis of results obtained from deuterium-labeled fatty acids, which showed that different CRF ions (but with the same m/z value in the absence of labels) could be produced by different mechanisms, and all of them were obviously realized under CAD conditions that made spectra practically indistinguishable. The other example, which compared the REC-MS/MS spectrum of [M - H](-) ions and EI-MS/MS spectrum of M+. ions of daidzein, demonstrated the potential of the REC-MS/MS technique for more complex structure elucidation. Copyright (C) 2000 John Wiley & Sons, Ltd.