Ultra-short electron bunch length measurement was demonstrated with a dual-band Michelson interferometer observing coherent transition radiation (CTR). Simultaneous detection of CTR with two different infrared detectors with different bands enabled precise determination of the bunch length. The methodology analysis of the obtained interferograms was also examined with a model-based analysis. The capability of electron bunch lengths for the present measurement system was evaluated to be 3–100 fs with non-precise measurement region of 15–30 fs. Experimental frequency spectra of CTR were also reconstructed under assumption a Gauss-distribution electron bunch and gave good agreement with a Gaussian bunch form factor. Detailed analysis of obtained interferograms revealed simultaneous dual-band detection is important to examine obtained value of bunch lengths.
