Broadband optical delay with large dynamic range

摘要: The use of atomic media to produce optical delay has predominantly exploited the steep dispersion associated with electromagnetically induced transparency (EIT)[1]. While this can lead to very low group velocities it has a severe bandwidth limitation owing to the narrow spectral range over which the transparency and steep dispersion occur, making delays longer than the pulse width difficult to obtain.An attractive approach to realising a wide-bandwidth delay line utilises the intrinsic positive dispersion and high transmission between two absorption lines in an atomic vapour [2]. We have explored the delay and transmission properties of optical pulses tuned between the 85Rb (F= 2) and 87Rb (F= 1) components of the Rb D2 line, separated by about 2.5 GHz [3]. The observed optical delays for pulses at the frequency of peak transmission are shown in Fig 1a) for temperatures between 105◦ C and 135◦ C. A …