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Proceedings Paper

Precise measurement of the length by means of DFB diode and femtosecond laser
Author(s): Radek Šmíd; Ondřej Číp; Josef Lazar; Jan Jezek; Bohdan Ružička
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Paper Abstract

Need of precise definition of the calibrated length is of great importance in industrial application in these days. The Fabry-Perot interferometer or etalon with very high stable laser produces length etalon sensitive in nanometer scale with linear response to its change. Fabry-Perot interferometer (etalon) with length L represents a set of equidistant frequencies that could be transmitted through the length etalon. Each frequency could be described as multiple of free spectral range of Fabry-Perot etalon which depends inversely to the mirror spacing. Tuning DFB diode covering the tuning frequency range of hundreds of GHz is used as laser source for detection of transmitted light. Found DFB diode laser wavelength transmitted through the Fabry-Perot etalon is measured by wavelengthmeter. Train of femtosecond laser pulses produces an optical frequency spectrum (optical comb) of separate equidistant frequencies with an offset frequency. Stabilized optical comb generates a very precise frequency rule. Frequency beat between DFB laser source and the closest femtosecond laser line is detected to find the exact frequency. This procedure is done in whole DFB laser diode tuning range. Such method produce about hundred of reproductive and well defined measured points in DFB laser diode tuning range. Measured points are treated by computer algorithm. Moreover the Fabry-Perot mirror distance changes could be precisely analyzed by this method.

Paper Details

Date Published: 17 June 2009
PDF: 7 pages
Proc. SPIE 7389, Optical Measurement Systems for Industrial Inspection VI, 738933 (17 June 2009); doi: 10.1117/12.827577
Show Author Affiliations
Radek Šmíd, Institute of Scientific Instruments (Czech Republic)
Ondřej Číp, Institute of Scientific Instruments (Czech Republic)
Josef Lazar, Institute of Scientific Instruments (Czech Republic)
Jan Jezek, Institute of Scientific Instruments (Czech Republic)
Bohdan Ružička, Institute of Scientific Instruments (Czech Republic)


Published in SPIE Proceedings Vol. 7389:
Optical Measurement Systems for Industrial Inspection VI
Peter H. Lehmann, Editor(s)

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