A temporal cloak scheme based on tunable optical delay and advance is theoretically proposed. An input optical signal is divided into two parts, and the front part is advanced while the rear part is delayed. A temporal gap which contains negligible optical energy is opened to hide events from observers, which can be closed by doing the inverse process. Different from the previous schemes that use continuous wave light, we use an optical data stream as the probe beam. Simulations have been done to investigate performance of the temporal cloak. The developed scheme can be applied in fiber-optical signal processing and secure communications.
A temporal cloak scheme based on tunable optical delay and advance is theoretically proposed. An input optical signal is divided into two parts, and the front part is advanced while the rear part is delayed. A temporal gap which contains negligible optical energy is opened to hide events from observers, which can be closed by doing the inverse process. Different from the previous schemes that use continuous wave light, we use an optical data stream as the probe beam. Simulations have been done to investigate performance of the temporal cloak. The developed scheme can be applied in fiber-optical signal processing and secure communications.
Recent research has revealed a significant ability to manipulate and control a light beam to hide events in time-domain. Achieving highly functional temporal cloaking, which open up and subsequently close intensity gaps in the probe beam to conceal events from the observer with satisfied performances, are still difficult in optical fiber communication. Here, we propose and experimentally demonstrate a temporal cloak system based on ultra-short-pulse generation and time-domain fraunhofer diffraction. We succeed in hiding 83 percent of the whole time axis and cloak pseudorandom dark return-to-zero data bitrate at 10 Gbit/s. The four states of temporal cloaking and condition of cloaking off have been investigated in this paper.
Recent research on time cloaking has revealed a fascinating approach to hide temporal events from an interrogating optical field, by opening up and subsequently closing intensity gaps in a probe beam. Experiments thus far have demonstrated temporal cloaking of nonlinear interactions and high-speed optical data. Here we report a temporal cloak with the new capability not only to hide optical data, but also to concurrently transmit it along another wavelength channel for subsequent readout, masking the information from one observer while directing it to another. Additionally, the cloak succeeds in passing modulated data unscathed through a scrambling event, providing a new form of tampering resistance. Both examples launch a paradigm shift in temporal cloaking: instead of using time cloaks primarily to disrupt communication, we show how they can also improve data transmission, in turn greatly widening the range of possible applications in telecommunications.
The pursuit of invisibility cloaks has long been a central theme in science fiction literature. One approach involves altering the waveform transmitted to the observer in the spatial domain, represented by meta-materials. Another approach is to open a window in the time domain. Specifically, researchers for the first time opened a single or periodic time gap in the probe light sent to the observer, thereby hiding an event within this time gap [Nature481, 62 (2012)10.1038/nature10695]. However, the absence of an optical carrier in the opened window prevented the recovery of the hidden event even for the cooperator. Now, we have demonstrated a novel temporal cloak that can recover hidden events. In this temporal cloak, the opening and closing of time gaps are achieved through the precise manipulation of photon density and phase synchronization in the injection-locked laser. During the process, the inevitable spontaneous emission photons are utilized to carry the event information. The cloaking window demonstrates both flexibility and reconfigurability, with its size achieving a breakthrough extension to 2.5 µs compared with dispersion-based methods. These advancements represent a significant step towards the realization of time cloaking and have a direct impact on secure communication.
Summary form only given. Due to a growing demand of security in transmission systems, recent research have been focus on the ability to manipulate a light beam in such a way to hide, namely to cloak, an event over a finite time or localization in space. The main idea is to create a hole or a gap in the spatial or time domain so as to allow for an object or a data to be kept hidden for a while and then to be restored [1-2]. Here we experimentally demonstrate a new type of temporal cloaking based on the ability for an arbitrary polarized light beam to self-organize and trap its state of polarization (SOP) in an optical fiber and then, to self-scramble in a reverse manner. We analyze the performance of our system by alternatively spying and then cloaking a 10Gbit/s signal propagating in an optical fiber and threaten by an attempt of hacking though an optical parametric based copying process. We successfully show that a quasi-annihilation of the probing operation (cloaking mode) or alternatively an error-free copying process (spying mode) can be achieved, both modes being independent from the incident SOP. The principle is illustrated in Fig. 1a. After travelling through a transmission system, an incident signal reaches the cloaking/spying zone with an arbitrary SOP. At this point, a continuous wave (cw) probe is then used to attempt a copy of the transmitted signal through a fiber optical parametric amplifier (FOPA). Since parametric process in optical fiber is highly polarization dependent, the conversion efficiency towards the copy wave (i.e. the idler) is strongly dependent on the incident signal SOP, which in usual situation where SOP randomly fluctuates, does not allow any kind of stable processing. Nevertheless, a successful cloaking or spying operation could be performed if one can trap the incident signal SOP orthogonal or parallel to the probe state. Here, this operation of polarization trapping is realized by means of an all-optical Omnipolarizer (OP) [3] in which self-organization of light SOP is spontaneously achieved by means of a counter-propagating four-wave mixing between the signal beam and its own backward replica generated through a reflective-loop [3]. As a consequence, in the cloaking zone, if the OP traps the signal SOP orthogonally to the probe state, no idler is generated and the signal remains hidden. At the opposite, if the OP locks the incident signal SOP parallel to the probe state, a maximal idler is then generated and the signal is kept hacked independently of its input SOP. Finally, to keep a transparent operation for the user, polarization randomness of the signal is restored thanks to a second Omnipolarizer, in which a high power backward replica induces the self-polarization process to become chaotic, leading to the unexpected behavior of the device to play the role of all-optical scrambler.Γ
Considered to only exist in fairy tales in the past, invisibility cloaks have been successively converted into reality no matter in the spatial domain or the temporal domain. Inspired by the spatial cloaking, time gaps are utilized to hide temporal events. However, a sophisticated synchronization for cloaking is indispensable in these cloaking techniques, therefore leaving inconvenience for the realization of the temporal cloak. Here, by exploiting the temporal Talbot effect, we propose a brand new scheme and concept to achieve a temporal cloak without any synchronization for the cloaking process, under which the intensity-modulated event is directly turned into invisibility in intensity through temporal averaging effect induced by the Talbot effect. We successfully realize the temporal cloak for periodic and pseudo-random signals. We also find that the higher order temporal Talbot effect is beneficial to the cloaking performance. Due to the transformed information on the phase, the data could be recovered from the intensity-cloaked waveform, leading to a non-full-field cloak. This method and its concept render a distinct perspective for the temporal cloak, extend temporal cloak to the pulsed-wave, and promote the development of confidential communication.