RESUMO
A coherence sidelobe suppression method for a laser diode (LD) is proposed, based on the white-noise-current modulation and external cavity feedback. The theoretical model of the coherence of the white-noise-current-modulated external cavity laser (WECL) is established, which details the spectrum broadening mechanism and the coherence sidelobe suppression. At the noise current modulation, the coherence sidelobe induced by the internal cavity is lowered by the external cavity feedback, and the position of the coherence sidelobe induced by the external cavity is controlled with the cavity length, which can extend the coherence range without the sidelobes. The experimental results demonstrate that the 98.4% sidelobe suppression ratio (SLSR) of the WECL is achieved in dynamic interferometry, which is about 20% higher than that of the laser diode only with the white-noise-current modulation. This new, to the best of our knowledge, method can avoid the stray fringe cross talk caused by the multiple coherence sidelobes in the surface error measurements of parallel plates.
RESUMO
An all-fiber orthogonal-polarized white-noise-modulated laser (AOWL) for short-coherence dynamic interferometry is proposed. Short-coherence laser is achieved by current modulating of a laser diode with the band-limited white noise. A pair of orthogonal-polarized lights with adjustable delay for short-coherence dynamic interferometry are output by the all-fiber structure. In the non-common-path interferometry, the AOWL can significantly suppress the interference signal clutter with 73% side lobe suppression ratio, that improves the positioning accuracy of zero optical path difference. The wavefront aberrations of a parallel plate are measured with the AOWL in the common-path dynamic interferometers, avoiding the fringe crosstalk.