Transfer of orbital angular momentum of light using electromagnetically induced transparency

We experimentally investigate the transfer of orbital angular momentum (OAM) of light in a solid driven by electromagnetically induced transparency (EIT). Under the condition of dynamical EIT, the OAM of the probe pulse is stored and retrieved in the experimental medium. By using a four-level double-lambda system to control the retrieval process of EIT storage, we show that OAM can be transferred from the probe field or the second control field to the newly generated signal field, which has a new spatial-frequency mode compared with the input mode. Furthermore, we use EIT-based four-wave mixing to investigate the direct OAM transfer without experiencing the storage, where we do not need to switch off and back on the control field.

Figure 1

(a) Levels of ${}^{3}H_4\to {}^{1}D_2$ optical transition of Pr:YSO and the applied light fields. (b) The experimental setup of OAM transfer. BS, beam splitter; M, mirror; AOM, acousto-optic modulator; SLM, spatial light modulator; L, lens; PD, photodiode. (c) The doughnut-type intensity profile of LG-mode vortex beam. (d) The self-interference pattern of optical vortex beam with the tilted-lens method.

Figure 2

(a) Experimental pulse sequences of OAM storage. (b) The self-interference patterns of the retrieved probe pulse for different input charges $l_P=-2,-1,+1,+2$. (c) The storage efficiency vs the storage time. (d) The similarity vs the storage time.

Figure 3

(a) Experimental pulse sequences of OAM transfer based on EIT storage. (b) The self-interference patterns of the generated signal field for different input charges $l_P=-2,-1,+1,+2$. (c) The self-interference patterns of the generated signal field for different input charges $l_{C2}=-2,-1,+1,+2$.

Figure 4

(a) Experimental pulse sequences of OAM transfer based on FWM. (b) The self-interference patterns of the generated signal field for different input charges $l_P=-2,-1,+1,+2$. (c) The self-interference patterns of the generated signal field for different input charges $l_{C2}=-2,-1,+1,+2$.