Fig. 4

Multi-wavelength operation. a Multi-wavelength operation of the photonic–phononic memory for three different laser wavelengths λ for the data pulses (thin lines) (blue curve: 1549 nm, green curve: 1551.3 nm, red curve: 1552.9 nm). The efficiency of the memory remains the same (thick lines). The Brillouin frequency shift Ω was adjusted to 7.75 GHz, 7.74 GHz and 7.73 GHz, respectively. b Phase-matching condition for two data pulses and one write pulse phase-matched to data pulse 1 (corresponds to measurement c, d). The data pulse 2 is not phase-matched and therefore not affected by the write pulse 1. c Storage and retrieval of data pulse 1 (blue and red curve, respectively) while data pulse 2 (d) in a separate channel (100 GHz away from channel 1) is unaffected (blue dashed line: channel 1 off; red line: channel 1 stored and retrieved). e Phase-matching condition for two separate read pulses with data pulse 1 (corresponds to measurement f, g). One can see that read pulse 2 cannot readout phonon 1. f Shows the writing and retrieving of a data pulse (blue and red curve, respectively) in channel 1 while at the same time no readout pulse can be seen in channel 2 (g; blue dashed line: channel 1 off; red line: channel 1 stored and retrieved). h Phase-matching condition for two channels operating at two different wavelengths. i Storage and retrieval of data in channel 1 while simultaneously storing and retrieving data in channel 2 (j) (blue and red curve, respectively). For comparison the storage and retrieval of only channel 2 is depicted by the dashed orange line in j. Note: the difference in the noise floor between channel 1 and channel 2 is caused by the different noise properties of the two different photodiodes