Brillouin frequency shift measurement by zero-crossing point search in virtually synthesized spectra of Brillouin gain and loss

We demonstrate a method for fast and precise Brillouin frequency shift measurement based on searching for the zero-crossing point of a virtually composed spectra of Brillouin gain and loss, obtained by dual-frequency probe beam. Simulations and experiments show that searching for the zero-crossing point of virtually synthesized Brillouin gain spectrum can be easily done without a large error compared with the peak search of Brillouin gain spectrum in the conventional method.