Far-infrared spectroscopy obtained with the ISO LWS has shown that there is strong variation (more than 2 orders of magnitude) in the [C II]/FIR ratios in galaxies extending from blue compact dwarfs, to normal and starburst galaxies, down to elliptical and ultraluminous galaxies (ULIGs). The variation in the relative [C II] 158 µm line strength has been attributed to low metallicity in blue com...

In the early 1950s, Golay studied binary sequence pairs whose autocorrelation properties are ideal for use in the design of multislit spectrometers. He found examples for some small lengths, but, unable to find more, he suggested that perhaps further examples do not exist and turned his attention to an alternative solution to the design problem (involving what are now called Golay complementary...

We theoretically discuss the impact of the cavity configuration on the possible longitudinal mode multistability in homogeneously broadened lasers. We present a general method allowing to perform a direct bifurcation diagram and to determine the stability of the solutions of a Travelling wave model. We find, in agreement with recent experimental reports, that multistability is more easily reach...

In optical testing, when the wave-front error of a test optic is much larger than the wavelength of visible light, it may be difficult to analyze the closely spaced interference fringes in the interferogram. The use of a less-sensitive testing technique or a long-wavelength interferometer would be preferred for this purpose. In addition, when the optic is to be tested in transmission, the wavel...