Abstract
We demonstrate an optically controlled waveplate at ~1323 nm using the 5S(1/2)-5P(1/2)-6S(1/2) ladder transition in a Rb vapor cell. The lower leg of the transitions represents the control beam, while the upper leg represents the signal beam. We show that we can place the signal beam in any arbitrary polarization state with a suitable choice of polarization of the control beam. Specifically, we demonstrate a differential phase retardance of ~180 degrees between the two circularly polarized components of a linearly polarized signal beam. We also demonstrate that the system can act as a Quarter Wave plate. The optical activity responsible for the phase retardation process is explained in terms of selection rules involving the Zeeman sublevels. As such, the system can be used to realize a fast Stokesmetric imaging system with a speed of ~3 MHz. When implemented using a tapered nano fiber embedded in a vapor cell, this system can be used to realize an ultra-low power all-optical switch as well as a Quantum Zeno Effect based all-optical logic gate by combining it with an optically controlled polarizer, previously demonstrated by us. We present numerical simulations of the system using a comprehensive model which incorporates all the relevant Zeeman sub-levels in the system, using a novel algorithm recently developed by us for efficient computation of the evolution of an arbitrary large scale quantum system.
Highlights
All-optical switching is important for optical communication and quantum information processing [1,2,3,4,5]
In order to determine the polarization of the signal beam after passing through the cell, we inserted an analyzer before detector A, consisting of a voltage-controlled liquid crystal retarder (LCR), whose fast axis is placed at 45 degrees to the initial polarization direction of the signal beam, followed by a polarizer with its axis orthogonal to initial polarization of the signal beam
As the probe laser was scanned across the 6S1/2 manifold, the detuning of the control beam was varied in order to maximize the transmission through the orthogonal polarizer over the largest possible bandwidth
Summary
All-optical switching is important for optical communication and quantum information processing [1,2,3,4,5]. Theoretical and experimental investigations of optically controlled polarization rotation using ladder transitions in alkali metals have been carried out previously [17,18,19,20,21] All of these works employ the EIT effect where the upper leg is excited by a strong control field while the lower leg is probed by a weak optical field. Excited state polarization spectroscopy is related to our work in the sense that they study the modification of the properties of the optical field coupling the upper leg [23, 24] They are primarily concerned with obtaining adispersion like signal with high SNR for laser frequency stabilization [25, 26] and are based on polarization dependent selective absorption of the probe, while our work is concerned with nearly lossless polarization rotation intended to be used in all-optical switching.
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