Coherence of Light .

Chung-Hyun Lee, Yosep Kim, Dong-Gil Im +3 more

Coherent light detection and ranging (LIDAR) offers exceptional sensitivity and precision in measuring the distance of remote objects by employing first-order interference. However, the ranging capability of coherent LIDAR is principally constrained by the coherence time of the light source determined by the spectral bandwidth. Here, we introduce coherent two-photon LIDAR, which eliminates the range limitation of coherent LIDAR due to the coherence time. Our scheme capitalizes on the counterintuitive phenomenon of two-photon interference of thermal light, in which the second-order interference fringe remains impervious to the short coherence time of the light source determined by the spectral bandwidth. By combining this feature with transverse two-photon interference of thermal light, we demonstrate distance ranging beyond the coherence time without relying on time-domain interference fringes. Moreover, we show that our coherent two-photon LIDAR scheme is robust to turbulence and ambient noise. This work opens up novel applications of two-photon correlation in classical light.

Л.М. Сороко

Dilawar Ali, Muhammad Umer Iftikhar, Muqaddar Abbas +1 more

Abstract A cold atomic medium (Rydberg medium) with cascade configuration under the blockade mechanism is considered. A partial coherent light (PCL) beam is incident on the medium, which makes an angle θ with z-axis. We study the influence of PCL field on the transmission spectrum and find high transmission of probe field for PCL field. Conversely, it is investigated that the transparency of probe field decrease for coherent light field. The transmission of probe field is also studied via beam width of PCL field and investigated high transmission of probe field for small beam width and vice versa. Interestingly, the Goos-Hänchen shift (GHS) in the transmitted light (TL) is studied for PCL field. Large negative and positive GHS in the TL are investigated for PCL field and small beam width of PCL field.

Jan Peřina

Taek Jeong, Jumi Park, Han Seb Moon

In quantum memory based on an atomic medium, we may have a question about whether all information on the stored light is preserved. In particular, the phase coherence between the stored and retrieval light pulses is very interesting, because it can indicate the relationship between the coherence time and storage time of the light. In this paper, we investigate the phase coherence time of light stored in a warm atomic vapor, by examining the beat-note interference between the retrieval light pulse and a reference light beam optically delayed using an optical fiber. The beat-note interference fringes are measured for different reference-light optical delays. The observed retrieval-light phase indicates that the phase of the input probe light is preserved in the medium. However, we further confirm that the retrieval-light phase coherence depends on the phase coherence of the coupling light used for retrieval in the storage process.