Spectral cloaking, by creating a spectral hole in a probe signal within which the spectrum of an obstacle signal can hide, is an important technology for encrypted communications and signal processing. Previous studies mainly rely on electro-optic modulations to realize spectral cloaking, which, however, suffer from inherent bandwidth limitations. By constructing a nonlinear four-wave mixing (FWM) time lens, we achieve the spectral Talbot effect and apply it to realize broadband spectral cloaking. We analyze the conditions to realize integer and fractional spectral Talbot effect, whereby arbitrary scaling of the free spectral range (FSR) of an input frequency comb can be achieved. By further cascading two FWM time lenses with reversible dispersions, we achieve FSR reconstruction for the input signal via spectral multiplication and division, thus creating a broadband spectral cloak up to 40 GHz in between. Such a cloak can hide the spectral information of an obstacle signal from being probed by the signal light, thus realizing invisible functionality. We establish an all-optical approach for realizing advanced spectral cloaking through FSR control, paving also promising avenues toward high-security encryption and antijamming optical communications.
Spectral cloaking, by creating a spectral hole in a probe signal within which the spectrum of an obstacle signal can hide, is an important technology for encrypted communications and signal processing. Previous studies mainly rely on electro-optic modulations to realize spectral cloaking, which, however, suffer from inherent bandwidth limitations. By constructing a nonlinear four-wave mixing (FWM) time lens, we achieve the spectral Talbot effect and apply it to realize broadband spectral cloaking. We analyze the conditions to realize integer and fractional spectral Talbot effect, whereby arbitrary scaling of the free spectral range (FSR) of an input frequency comb can be achieved. By further cascading two FWM time lenses with reversible dispersions, we achieve FSR reconstruction for the input signal via spectral multiplication and division, thus creating a broadband spectral cloak up to 40 GHz in between. Such a cloak can hide the spectral information of an obstacle signal from being probed by the signal light, thus realizing invisible functionality. We establish an all-optical approach for realizing advanced spectral cloaking through FSR control, paving also promising avenues toward high-security encryption and antijamming optical communications.
We experimentally demonstrate two innovative applications of photonic technologies previously solidified in the field of classical optical communications. In the first application, we exploit electro-optic modulator technology to develop a novel "time cloak,'' a device which hides events in time by manipulating the flow of a probing light beam. Our temporal cloak is capable of masking high-speed optical data from a receiver, greatly improving the feasibility of time cloaking and bringing such exotic concepts to the verge of practical application. In the second specialization, high-resolution Fourier-transform pulse shaping---perfected for multi-wavelength telecom networks---is applied to shape the correlations of entangled photon pairs, states which have received considerable attention in nonlocal tests of quantum theory and in quantum key distribution. Using nonlinear waveguides fabricated out of periodically poled lithium niobate, we are able to demonstrate ultrafast coincidence detection with record-high efficiency, which coupled with our pulse shaper allows us to realize for the first time several capabilities in biphoton control, including high-order dispersion cancellation, orthogonal spectral coding, correlation train generation, and tunable delay control. Each of these experiments represents an important advance in quantum state manipulation, with the potential to impact developments in quantum information. And more generally, our work introducing telecommunication technology into both temporal cloaking and biphoton control highlights the potential of such tools in more nascent outgrowths of classical and quantum optics.
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.
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.
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
Restricted to picosecond scale time gaps, the previous reported temporal cloaking schemes are hardly possible for practical applications. In this paper, we report a nanosecond scale temporal cloaking regime based on the fast/slow light effect in unbalanced fiber Mach-Zehnder interferometers. By exerting a radio frequency modulation onto the probe light, we broke through the gap time limit. A time gap up to 5.3ns was created and experimentally observed. The modulation signal in the time gap was concealed efficiently. Realizing nanosecond time gaps is critical for potential applications of temporal cloaking, such as secure communication and signal processing. This solution may push this fascinating idea into reality
Time-frequency entangled photons ("biphotons") exhibit joint spectral and temporal correlations that are unattainable with classical light. Besides being deployed for tests of quantum nonlocality, these photonic states are desirable for a unique range of applications that can significantly impact communications and computation. In this dissertation, we describe novel schemes based on spectral and temporal domain processing for manipulating and characterizing broadband biphotons. Implementing frequency-dependent filters, first, we present and demonstrate a technique for controlling the relative delay between a pair of entangled photons, relying on pump frequency tuning and the quantum concept of nonlocal dispersion cancellation. Next, we demonstrate near-field frequency-to-time mapping, a technique adopted from classical photonics, for arbitrary control of biphoton temporal correlations. Subsequently, we generate temporal correlation trains by creating biphoton frequency combs through programmable spectral amplitude shaping and demonstrate the temporal Talbot effect with entangled photons for the first time. Moreover, in the absence of fast single-photon detectors, we show how electro-optic phase modulation (originally a time-dependent operation) can be used to examine the coherence of biphoton frequency combs. Lastly, we introduce a scheme based on electro-optic intensity modulation, another time-domain operation, for improving the resolution in biphoton temporal correlation measurements. Overall, our body of work could provide additional insight into the manipulation and characterization of biphoton states, as well as contribute towards the improvement of quantum technologies.