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Mar 2002

Volume 73, Issue 3, pp. 1103-1683

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back to top OPTICS; ATOMS and MOLECULES; SPECTROSCOPY

Device for frequency chirp measurements of optical transmitters in real time

Tapio Niemi, Simo Tammela, and Hanne Ludvigsen

Rev. Sci. Instrum. 73, 1103 (2002); http://dx.doi.org/10.1063/1.1448898 (5 pages) | Cited 2 times

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We present a new automated device for measurement of time-resolved frequency chirp of optical transmitters. It measures chirp in real time by utilizing two temperature-tunable silicon-wafer etalons as frequency discriminators. The time-resolved frequency chirp in a range of ±12 GHz can be measured with a time resolution of approximately 40 ps. © 2002 American Institute of Physics.
Show PACS
42.79.Sz Optical communication systems, multiplexers, and demultiplexers
42.60.Fc Modulation, tuning, and mode locking
07.60.Ly Interferometers
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Highly reproducible laser beam scanning device for an internal source laser desorption microprobe Fourier transform mass spectrometer

Jill R. Scott and Paul L. Tremblay

Rev. Sci. Instrum. 73, 1108 (2002); http://dx.doi.org/10.1063/1.1445868 (9 pages) | Cited 12 times

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Traditionally, mass spectrometry has relied on manipulating the sample target to provide scanning capabilities for laser desorption microprobes. This has been problematic for an internal source laser desorption Fourier transform mass spectrometer (LD-FTMS) because of the high magnetic field (7 Tesla) and geometric constraints of the superconducting magnet bore. To overcome these limitations, we have implemented a unique external laser scanning mechanism for an internal source LD-FTMS. This mechanism provides adjustable resolution enhancement so that the spatial resolution at the target is not limited to that of the stepper motors at the light source (∼5 μm/step). The spatial resolution is now limited by the practical optical diffraction limit of the final focusing lens. The scanning mechanism employs a virtual source that is wavelength independent up to the final focusing lens, which can be controlled remotely to account for focal length dependence on wavelength. A binary index provides an automatic alignment feature. The virtual source is located ∼9 ft from the sample; therefore, it is completely outside of the vacuum system and beyond the 50 G line of the fringing magnetic field. To eliminate reproducibility problems associated with vacuum pump vibrations, we have taken advantage of the magnetic field inherent to the FTMS to utilize Lenz’s law for vibrational dampening. The LD-FTMS microprobe has exceptional reproducibility, which enables successive mapping sequences for depth-profiling studies. © 2002 American Institute of Physics.
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07.75.+h Mass spectrometers
42.62.-b Laser applications
68.43.Tj Photon stimulated desorption
79.20.La Photon- and electron-stimulated desorption
42.79.Bh Lenses, prisms and mirrors

Two straightforward methods for the measurement of optical losses in planar waveguides

Roberta Ramponi, Roberto Osellame, and Marco Marangoni

Rev. Sci. Instrum. 73, 1117 (2002); http://dx.doi.org/10.1063/1.1448143 (4 pages) | Cited 30 times

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Two new straightforward methods for the evaluation of optical losses in planar waveguides are proposed and discussed. The first method exploits a single nonsliding isosceles prism and it allows the attenuation to be determined through the measurement of the power exiting the waveguide and the evaluation of the coupled power. It requires a very simple operation procedure, it allows a mode-selective determination of losses, and it presents a good accuracy provided that the sample is not too short. The second method uses end-fire coupling and it is based on the measurement of the output power together with the power back-reflected by the output face of the waveguide. The main advantage of the method is that it can be very accurate also for shorter waveguides and that its accuracy is to a high degree insensitive with respect to the optical depth of the waveguide. It provides better results in the case of high refractive index waveguides that give an intense back-reflected signal. Experimental results obtained with both methods on two different waveguides are presented. © 2002 American Institute of Physics.
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42.82.Et Waveguides, couplers, and arrays
42.79.Gn Optical waveguides and couplers
42.87.-d Optical testing techniques
42.82.Bq Design and performance testing of integrated-optical systems
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