Weak-light ultraslow vector solitons via electromagnetically induced transparency

Abstract

We propose a scheme to generate temporal vector optical solitons in a lifetime broadened fivestate atomic medium via electromagnetically induced transparency. We show that this scheme, which is fundamentally different from the passive one by using optical fibers, is capable of achieving distortion-free vector optical solitons with ultraslow propagating velocity under very weak drive conditions. We demonstrate both analytically and numerically that it is easy to realize Manakov temporal vector solitons by actively manipulating the dispersion and self-and cross-phase modulation effects of the system. PACS numbers: 42.65.Tg, 42.50.GyThe vector nature of light propagating in a nonlinear medium has led to the discovery of a novel class of solitons, i. e. vector optical solitons, which are the solutions of two coupled nonlinear Schrödinger (NLS) equations describing the envelope evolution of two polarization components of an electromagnetic field. In recent years, considerable attention has been paid to the temporal [1,2,3,4,5,6] and spatial [7,8,9, 10] vector optical solitons in various nonlinear systems. Due to their remarkable property, vector optical solitons have promising applications for the design of new types of all-optical switches and logic gates [12].Up to now, most vector optical solitons are produced in passive media such as optical fibers [2,3,4,5,6,7,8,9,10], in which far-off resonance excitation schemes are employed in order to avoid unmanageable optical attenuation and distortion. However, due to the lack of distinctive energy levels, the nonlinear effect in such passive media is very weak, and hence to form vector solitons a very high input light-power is required. In addition, the lack of distinctive energy levels and transition selection rules also makes an active control very difficult. In particular, it is hard to realize Manakov[11] temporal vector optical solitons in optical fibers because the ratio between self-phase modulation (SPM) and cross-phase modulation (CPM) is not unity and there is also detrimental energy exchange between two polarization components due to the existence of four-wave mixing effect. Manakov vector optical solitons are of great interest, not only because the coupled NLS equations describing them have beautiful mathematical properties but also such solitons may be used to realize all-optical computing [13]. Different from spatial Manakov vector optical solitons, which have been observed more than ten years ago [8], temporal Manakov vector optical solitons have not been realized in experiment up to now.In this Letter, we propose a scheme to generate temporal vector optical solitons in a coherent five-level atomic system via electromagnetically induced transparency (EIT). This resonant EIT medium has been recently used to realize polarization qubit phase gate [14] and reversible memory devices for photon-polarization qubit [15]. We show that two continuous-wave (CW) control laser fields established prior to the injection of a pulsed probe field induce a quantum interferen...

Phase-controlled optical switching and slow- and weak-light solitons in a coherent molecular system with permanent dipole moments

“…EIT is a very typical quantum interference phenomenon, which can be used to manipulate physical properties for both light and matter, including large reduction of group velocity [2,3] and giant enhancement of Kerr nonlinearity [4,5]. Based on these important features, EIT has been used to realize slow light, quantum memory [6,7], highly efficient four-wave mixing [8], high-precision measurement [9], quantum phase gates [10,11], weak-light ultraslow solitons [12][13][14][15], spatial solitons [16][17][18][19][20], and so on.…”

Manipulation of a weak signal pulse by optical soliton via double electromagnetically induced transparency

“…The disadvantages mentioned above can be overcome by the discovery of electromagnetically induced transparency (EIT) in a resonant atomic system at very low light level [16]. Through the giant enhancement of self-Kerr and cross-Kerr nonlinearities induced by EIT, there are many interesting researches paying attention to numerous nonlinear optical progresses, including temporal (spatial) optical solitons [17][18][19], Manakov/ Thirring vector solitons [20][21][22][23][24][25], high-dimensional spatiotemporal optical solitons [26][27][28][29][30], efficient multiwave mixing [31], the bistable state [32], and so on. In addition, different from the mechanism of Manakov/Thirring model, trapping light by light here is that a soliton pulse formed by self-phase modulation (SPM) offers an external potential to a weak laser light pulse through CPM.…”

Gain-assisted high-dimensional self-trapped laser beams at very low light levels

“…EIT can be used not only for suppressing optical absorption but also for acquiring ultraslow group velocity, for enhancing Kerr nonlinearity [6], and for temporal [7][8][9] and spatial [10][11][12][13] optical solitons and vortices in resonant nonlinear systems. However, the EIT-based schemes have some inherent drawbacks such as the probe attenuation and spreading at room temperature and the long response time because of the character of ultraslow propagation.…”