Applications In Optical Information Processing Research Articles

Controllable hybrid shape of correlation and squeezing

Two- and three-mode correlation and squeezing of spontaneous parametric four-wave mixing (SPFWM) and fourth-order fluorescence (FL) composite signals are investigated theoretically and experimentally in both homonuclear (two-level) and heteronuclearlike (V-type level) molecular systems of $\mathrm{P}{\mathrm{r}}^{3+}$:YSO. By selecting different time positions, changing the power, and changing the frequency detuning of the laser field, the competition between the composite signals is demonstrated. It is found that as the laser parameters change, the signal evolves from a nonlinear ${\ensuremath{\chi}}^{(4)}$ process resulting in a FL signal to a SPFWM signal $({\ensuremath{\chi}}^{(3)}$ process). In addition, the competition effect between the signals determines the evolution of the shape of the correlation from a pure sharp to a two-stage (mixed) shape and finally to a pure broad peak amplitude. Furthermore, the signal evolution determines the magnitude of squeezing, which can control the noise level. Such progress may find potential applications in optical hybrid communication and information processing.

Annular beam with segmented phase gradients

An annular beam with a single uniform-intensity ring and multiple segments of phase gradients is proposed in this paper. Different from the conventional superposed vortices, such as the modulated optical vortices and the collinear superposition of multiple orbital angular momentum modes, the designed annular beam has a doughnut intensity distribution whose radius is independent of the phase distribution of the beam in the imaging plane. The phase distribution along the circumference of the doughnut beam can be segmented with different phase gradients. Similar to a vortex beam, the annular beam can also exert torques and rotate a trapped particle owing to the orbital angular momentum of the beam. As the beam possesses different phase gradients, the rotation velocity of the trapped particle can be varied along the circumference. The simulation and experimental results show that an annular beam with three segments of different phase gradients can rotate particles with controlled velocities. The beam has potential applications in optical trapping and optical information processing.

Lifetime Autler-Townes Splitting of Dressed Multi-Order Fluorescence in Pr3+:YSO

For first time, we study primary and secondary Autler-Townes (AT) splitting of multi-order fluorescence (FL) in time domain. The AT-splitting of multi-order FL signals are controlled by changing power, detuning, and polarization of single and double dressing in a heteronuclear-like molecule system of Pr+3:YSO. The primary and secondary AT-splitting is caused by double cascaded dressing in time domain. The AT-splitting of multi-order FL in time domain is more sensitive than that of in spectral domain. Such results have potential applications in quantum communication and optical information processing on photonic chip.

A photon-photon quantum gate based on a single atom in an optical resonator.

That two photons pass each other undisturbed in free space is ideal for the faithful transmission of information, but prohibits an interaction between the photons. Such an interaction is, however, required for a plethora of applications in optical quantum information processing. The long-standing challenge here is to realize a deterministic photon-photon gate, that is, a mutually controlled logic operation on the quantum states of the photons. This requires an interaction so strong that each of the two photons can shift the other's phase by π radians. For polarization qubits, this amounts to the conditional flipping of one photon's polarization to an orthogonal state. So far, only probabilistic gates based on linear optics and photon detectors have been realized, because "no known or foreseen material has an optical nonlinearity strong enough to implement this conditional phase shift''. Meanwhile, tremendous progress in the development of quantum-nonlinear systems has opened up new possibilities for single-photon experiments. Platforms range from Rydberg blockade in atomic ensembles to single-atom cavity quantum electrodynamics. Applications such as single-photon switches and transistors, two-photon gateways, nondestructive photon detectors, photon routers and nonlinear phase shifters have been demonstrated, but none of them with the ideal information carriers: optical qubits in discriminable modes. Here we use the strong light-matter coupling provided by a single atom in a high-finesse optical resonator to realize the Duan-Kimble protocol of a universal controlled phase flip (π phase shift) photon-photon quantum gate. We achieve an average gate fidelity of (76.2 ± 3.6) per cent and specifically demonstrate the capability of conditional polarization flipping as well as entanglement generation between independent input photons. This photon-photon quantum gate is a universal quantum logic element, and therefore could perform most existing two-photon operations. The demonstrated feasibility of deterministic protocols for the optical processing of quantum information could lead to new applications in which photons are essential, especially long-distance quantum communication and scalable quantum computing.

Optical processes of photonic band gap structure with dressing field in atomic system

We experimentally investigate probe transmission signals (PTS), the four-wave mixing photonic band gap signal (FWM BGS), and the fluorescence signal (FLS) in an inverted Y-type four level atomic system. For the first time, we compare the FLS of the two ground-state hyperfine levels of Rb 85. In particular, the second-order and the fourth-order fluorescence signals perform dramatic dressing discrepancies under the two hyperfine levels. Moreover, we find that the dressing field has some dressing effects on three such types of signals. Therefore, we demonstrate that the characteristics of PTS, FWM BGS, and FLS can be controlled by frequency detunings, the powers or phases of the dressing field. Such research could have potential applications in optical diodes, amplifiers, and quantum information processing.

Tunable Plasmonic Wavelength Demultiplexing Device Using Coupled Resonator System

Plasmonic devices have recently been widely studied recently due to their properties of light confinement, which shows great potential applications in optical information processing. Here, in exploiting plasmonic metal–insulator–metal (MIM) side-coupled cavities, we present a theoretical implementation of the plasmonic wavelength demultiplexer (PWDM) device. The proposed PWDM device is designed using an add–drop-drop structure, which consists of one input port and two output ports. The transmission of the plasmonic field on the drop ports could be tuned by changing the gap between the waveguide and plasmonic resonators. Our approach captures the wavelength demultiplexing properties of the plasmonic field using the proposed structure. The performance of our device is analyzed based on the structure with three waveguides coupled with two square cavities.

Detection of orbital angular momentum using a photonic integrated circuit.

Orbital angular momentum (OAM) state of photons offer an attractive additional degree of freedom that has found a variety of applications. Measurement of OAM state, which is a critical task of these applications, demands photonic integrated devices for improved fidelity, miniaturization, and reconfiguration. Here we report the design of a silicon-integrated OAM receiver that is capable of detecting distinct and variable OAM states. Furthermore, the reconfiguration capability of the detector is achieved by applying voltage to the GeSe film to form gratings with alternate states. The resonant wavelength for arbitrary OAM state is demonstrated to be tunable in a quasi-linear manner through adjusting the duty cycle of the gratings. This work provides a viable approach for the realization of a compact integrated OAM detection device with enhanced functionality that may find important applications in optical communications and information processing with OAM states.

Tunable multiple plasmon-induced transparency with side-coupled rectangle cavities

The tunable multiple plasmon-induced transparency (PIT) effect is investigated numerically in a metal-insulator-metal (MIM) waveguide with three side-coupled rectangular resonators. The system exhibits dual-mode PIT effects in the visible and near-infrared regions. By adjusting the geometrical parameters of the structure, we can manipulate not only each single PIT window, but also the double PIT windows simultaneously. Our structures may have potential applications for optical communication, integrated optics, and optical information processing. The finite element method (FEM) illustrates our theoretical design.

Phase-controlled two-wave mixing in a moving grating

Two-wave mixing is fundamental to applications in optical signal processing, holographic information, and imaging science. Conventionally, it takes place in a nonlinear medium where self-induced optical grating can effectively couple two optical waves. However, it demands high input power to trigger nonlinearities and is complicated by the phase shift of the optical grating for the given medium. Here, we separate these physical processes by studying near-degenerated two-wave mixing in a moving grating induced independently by an external acoustic optical modulator. Two-wave mixing is observed under Bragg’s phase matching condition, which is greatly affected by phase shifting. Moreover, we show that two-wave mixing here is unidirectional due to the propagation of acoustic waves, which may offer new avenues for applications in optical information processing.

Dynamic lossless polarization gate using a coherently prepared atomic medium.

We propose a dynamic lossless all-optical polarization gate using coherently prepared atomic media. We show that the loss/gain of two circularly polarized components of a linearly polarized probe field can be simultaneously eliminated by locking the power of the pump field and the external magnetic field intensity simultaneously. Using the polarization selective Kerr phase shift method, we can write π/2 (-π/2) phase shift to the right (left) circularly polarized component of the linearly polarized probe field with a choice of "magic" wavelength for the probe field. Consequently, the linear polarization state for the probe field acquires a 90° rotation at the exit of the medium. The scheme proposed in this Letter is helpful for applications in optical and quantum information processing and computation.

Controllable lifetime of fourth-order fluorescence and spontaneous parametric four-wave mixing in Pr^3+:YSO

We report the measured dressed lifetimes of fourth-order fluorescence and spontaneous parametric four-wave mixing signals by the perturbation chain method in a two-level and heteronuclear-like molecule system of Pr3+:YSO both in theory and experiment. The lifetime of the fourth-order fluorescence depends on the nonlinear processes in the perturbation chain, and can be modulated by the dark state due to the dressing effect and the induced dipole–dipole interaction by changing the frequency detuning and power of the controlling field. Such results can find potential applications in all-optical communication and optical information processing on photonic chips.

High‐Performance Broadband Circularly Polarized Beam Deflector by Mirror Effect of Multinanorod Metasurfaces

Manipulation of light phase and amplitude by plasmonic metasurfaces has immensely promising applications in optical imaging, information processing, communications, and quantum optics. However, the controllability of efficiency and bandwidth is relatively low for the single‐layer metasurfaces. Here, a high efficiency and broadband circularly polarized (CP) beam deflector based on multirod single‐layer metasurfaces is presented. Each unit can be regarded as an imperfect polarizer, and the phase and amplitude induced by the mirror effect can be easily controlled. Owing to the plasmonic hybridization, the high efficiency and broadband characteristics of the proposed metasurfaces are theoretically and experimentally demonstrated. Meanwhile, an easy way to determine the polarization degree of the incident light based on Poincaré sphere is also proved by the multirod metasurfaces. Our work provides a simple alternative way to enhance the efficiency of CP anomalous light and thus has robust applications in nanophotonics and nanooptics.

High-speed nonreciprocal magnetoplasmonic waveguide phase shifter

In the realm of modern day optical computing prospects, plasmonics provides a unique means of consolidating electronics and photonics in a nanoscale platform. For advanced optical information processing applications, there is a pressing need for configurable plasmonic platforms that mimic the functionalities of their electrical counterparts. In such a pursuit, the ability to actively manipulate plasmonic phenomena must first be realized via an electrical stimulus. An attractive architecture is realized by incorporating magneto-optical materials into devices, as the degree of electrical control they provide is unattainable by other material systems. Properties of the material are influenced by external magnetic fields, which can be conveniently generated by current passing through nearby metallic structures. While ferromagnetic metals are far too lossy for plasmonic integration, magnetic garnets can facilitate a robust and tunable architecture in a waveguide geometry. Here, we investigate a bismuth-substituted yttrium iron garnet platform for a high bandwidth active optical phase shifter. Our device is capable of imparting a large nonreciprocal phase shift of 6.99 rad/mm, while confining 70% of the modal power to the 0.081 μm2 cross-sectional area of the core. By considering the Landau–Lifshitz–Gilbert formalism, we show that the magnetoplasmonic phase shifter is operable in both underdamped and critically damped modes, and is fully tunable through the applied magnetic fields and pulsewidth. This magnetoplasmonic building block opens doors to a new class of nanoplasmonic devices, such as optical phase modulators, isolators, and optical clocks that will satisfy key applications in nanoscale optical information networks.

Spin noise amplification and giant noise in optical microcavity

When studying the spin-noise-induced fluctuations of Kerr rotation in a quantum-well microcavity, we have found a dramatic increase of the noise signal (by more than two orders of magnitude) in the vicinity of anti-crossing of the polariton branches. The effect is explained by nonlinear optical instability of the microcavity giving rise to the light-power-controlled amplification of the polarization noise signal. In the framework of the developed model of built-in amplifier, we also interpret the nontrivial spectral and intensity-related properties of the observed noise signal below the region of anti-crossing of polariton branches. The discovered effect of optically controllable amplification of broadband polarization signals in microcavities in the regime of optical instability may be of interest for detecting weak oscillations of optical anisotropy in fundamental research and for other applications in optical information processing.

Optical asymmetric image encryption using gyrator wavelet transform

In this paper, we propose a new optical information processing tool termed as gyrator wavelet transform to secure a fully phase image, based on amplitude- and phase-truncation approach. The gyrator wavelet transform constitutes four basic parameters; gyrator transform order, type and level of mother wavelet, and position of different frequency bands. These parameters are used as encryption keys in addition to the random phase codes to the optical cryptosystem. This tool has also been applied for simultaneous compression and encryption of an image. The system's performance and its sensitivity to the encryption parameters, such as, gyrator transform order, and robustness has also been analyzed. It is expected that this tool will not only update current optical security systems, but may also shed some light on future developments. The computer simulation results demonstrate the abilities of the gyrator wavelet transform as an effective tool, which can be used in various optical information processing applications, including image encryption, and image compression. Also this tool can be applied for securing the color image, multispectral, and three-dimensional images.

Extracting the phase information from atomic memory by intensity correlation measurement.

We demonstrate experimentally controlled storage and retrieval of the optical phase information in a higher-order interference scheme based on Raman process in (87)Rb atomic vapor cells. An interference pattern is observed in intensity correlation measurement between the write Stokes field and the delayed read Stokes field as the phase of the Raman write field is scanned. This result implies that the phase information of the Raman write field can be written into the atomic spin wave via Raman process in a high gain regime and subsequently read out via a spin-wave enhanced Raman process, thus achieving optical storage of phase information. This technique should find applications in optical phase image storage, holography and information processing.

Optical processes in different types of photonic band gap structures

For the first time, we investigate the photonic band gap (PBG) structure in the static and moving electromagnetically induced grating (EIG) through scanning the frequency detunings of the probe field, dressing field and coupling field. Especially, the suppression and enhancement of the four wave mixing band gap signal (FWM BGS) and the probe transmission signal (PTS) can be observed when we scan the dressing field frequency detuning in the FWM BGS system. It is worth noting that the PBG structure and FWM BGS appear at the right of the electromagnetically induced transparency (EIT) position in the case of scanning the frequency detuning of the coupling field in the FWM BGS system, while the PBG structure and FWM BGS appears at the left of the EIT position on the condition of scanning the probe field frequency detuning. Moreover, in the moving PBG structure, we can obtain the nonreciprocity of FWM BGS. Furthermore, we can modulate the intensity, width, location of the FWM BGS and PTS through changing the frequency detunings and intensities of the probe field, dressing field and coupling field, sample length and the frequency difference of coupling fields in EIG. Such scheme could have potential applications in optical diodes, amplifiers and quantum information processing.

Engineering of near-IR photon pairs to be factorable in space-time and entangled in polarization.

We present a source of near-infrared photon pairs based on the process of spontaneous parametric downconversion (SPDC), for which the joint signal-idler quantum state is designed to be factorable in the frequency-time and in the transverse position-momentum degrees of freedom. Our technique is based on the use of a broadband pump and vector group velocity matching between the pump, signal, and idler waves. We show experimentally that a source based on this technique can be configured for the generation of: i) pure heralded single photons, and ii) polarization-entangled photon pairs which are free from spectral correlations, in both cases without resorting to spectral filtering. While critical for many applications in optical quantum information processing, such a source has not previously been demonstrated.

Slow light propagation and bistable switching in a graphene under an external magnetic field

In this letter, we show the possibility of controlling the optical bistability and group index switching in graphene under the action of strong magnetic and infrared laser fields. By using quantum-mechanical density matrix formalism, we obtain the equations of motion that govern the optical response of graphene in strong magnetic and optical fields. We found that by properly choosing the parameters of the system, the bistable behaviors and group velocity can be controlled. These results may have potential applications in telecommunication and optical information processing.

Electronic structures and second hyperpolarizabilities of annulenes derivatives

Organic nonlinear optical materials have attracted considerable attention in recent years because of their potential applications in photonic devices and optical information processing. Recent studies have shown that annulene derivatives exhibit good second-order nonlinear optical properties, but their third-order nonlinear optical properties are studied little. In this paper, the values of molecular static linear polarizability α and second hyperpolarizability γ of substituted annulenes have been investigated with different levels of HF, B3LYP, BHandHLYP and CAM-B3LYP at different basis sets, respectively. Their ultraviolet spectra have also been calculated by using the TD-B3LYP method. It is found that the quality of the basis set is important for the hyperpolarizability calculations, and diffuse functions are important to obtain accurate results for the second hyperpolarizability. We also study the structure-optical property relationship for annulene. It is found that annulene molecular structure has a significant influence on third-order nonlinear optical response. Increasing the conjugation length and introducing push-pull electronic groups can enhance the second hyperpolarizability. But the introduction of push-pull electronic groups can enhance the hyperpolarizability more remarkably than increasing the conjugation length dose, which may be due to the fact that the introduction of push-pull electronic groups can provide a large number of polarizable electrons whereas increasing the conjugation length can only enhance the electron delocalization. Meanwhile the push-pull electronic group substituted annulenes can also exhibit high transparency in visible region. Thus, this work has a good reference for designing nonlinear optical material with high, nonlinear optical coefficient and good transparency. In addition, for the same push-pull electronic groups, the higher conjugation degree and the longer πup -conjugated bridge result in the decrease of HOMO-LUMO energy gap and transition energy which benefits the enhancement of nonlinear optical response. Our results demonstrate that annulene derivative shows both high transparency and large second hyperpolarizability, and thus becomes a promising candidate for third-order nonlinear optical material. In addition, the dynamic (hyper) polarizabilities of considered annulene molecules are calculated by using CAM-B3LYP method. It is found that in near-infrared region, with the increase of frequency of incident light, α (ω; ω), γ (-ω; ω, 0, 0) and γ (-2ω; ω, ω, 0) are all increased, and the near-resonance enhancement effect occurs. Under the condition of far resonance, α (ω; ω), γ (-ω; ω, 0, 0) and γ (-2ω; ω, ω, 0) change little. This dispersion effect may be helpful for the experimental study and applications as well.