Frequency-domain detection of superluminal group velocity in a distributedBragg reflector

Using a free-space configuration and a frequency-domain detection setup, gr oup velocities of electromagnetic waves in a distributed Bragg reflector ar e investigated. Experimental data indicates that, near the regions of minim al transmission in our configuration, the group velocity is 2.1 times faste r than the speed of light in vacuum. A transmission model based on diagonal ization of the transfer matrix is used to compare the experimental data and the theoretical calculations, and good agreement between theory and experi ment is obtained, An overview of the experimental uncertainties and their e ffects on the measured quantities is provided.