All-optical Control Of Light Research Articles

Efficient control of light propagation assisted by photothermal effect in a graphene-integrated all-fiber device

Graphene has arisen as an efficient photothermal (PT) nanomaterial owing to the strong light-matter interaction, ultrafast and nonradiative annihilation of the photoexcited carriers, and high thermal conductivity. Combined with the unique optical properties such as universal absorption coefficient at broadband wavelengths, the PT effect in graphene can be synergistically utilized for all-optical control of light. Here, we report an efficient transmission control of propagating light in graphene-covered side-polished fiber through the PT effect of graphene. When the local heat was generated via PT effect in graphene, a significant change in optical transmission was observed through two different mechanisms. The first one was implemented by the absorption change at the graphene layer via the asymmetrical reshaping of the mode-field distribution, resulting in the optical transmission change of up to 25 dB. The other mechanism was realized by the guiding property switching from the radiation mode to the guided mode of the light, resulting in the all-optical transmission control of over 56 dB at 1550 nm. The proposed method proves that the PT effect assists the broadband and efficient all-optical control with great versatility in graphene-integrated all-fiber devices.

All-optical light control with a AlGaAs-based metal-PhC cavity via multiple optical Tamm states

All-optical light control is the key technology for realizing optical computing, ultrahigh-speed information processing, and optical neural network. In this work, all-optical light control is investigated with a AlGaAs-based metal-photonic crystal (PhC) cavity, based on photorefractive effect and optical Tamm state. The proposed structure can generate multiple optical Tamm states in the stop-band of the PhC. That makes the optical properties of the proposed structure highly dependent on the refractive index of the AlGaAs layer. Through turning on and off the gate laser, the refractive index of the AlGaAs layer slightly changes. This tiny variation will strongly influence the intensity of the signal light. Simulated results show the normalized intensity of the reflected signal light can be tuned from ~0.0 to ~0.5 under suitable conditions. Meanwhile, this all-optical light control can be adjusted by changing the incident angle or the position of the signal light.

Terahertz Spoof Surface Plasmonic Logic Gates.

SummaryLogic gates are important components in integrated photonic circuitry. Here, a series of logic gates to achieve fundamental logic operations based on linear interference in spoof surface plasmon polariton waveguides are demonstrated at terahertz frequencies. A metasurface-based plasmonic source is adopted to couple free-space terahertz radiation into surface waves, followed by a funnel-shaped metasurface to efficiently couple the surface waves to the waveguides built on a domino structure. A single Mach-Zehnder waveguide interferometer can work as logic gates for four logic functions: AND, NOT, OR, and XOR. By cascading two such interferometers, NAND and NOR operations can also be achieved. Experimental investigations are supported by numerical simulations, and good agreement is obtained. The logic gates have compact sizes and high intensity contrasts for the output “1” and “0” states. More complicated functions can be envisioned and will be of great value for future terahertz integrated computing.

Bound states in the continuum for optomechanical light control with dielectric metasurfaces.

We investigate a reconfigurable dielectric metasurface merging optomechanical interaction and quasi-bound states in the continuum promising for all-optical light control light. The surface consists of a dimerized high-contrast grating with a compliant bilayer structure. The optical forces induced by a control light field lead to structural deformations changing the optical response. We discuss requirements for the geometry and optical force distribution to enable an efficient optomechanical coupling, which can be exploited to tune reflectivity, phase and polarization of a beam impinging on the metasurface. Numerical results explore some tunable devices as mirrors, saturable output couplers, phase modulators and retarder plates.

All-optical inverter based on carbon nanotube-polyvinyl alcohol thin film

All-optical light control plays an important role in optical signal processing and communications. In this Letter, we demonstrate an all-optical inverter using carbon nanotube (CNT)-polyvinyl alcohol (PVA) thin film and obtain a long-time stable output due to the environmental insensitivity of the device. The thermo-optic effect in the CNT-PVA thin film generates a thermal lens and modifies the beam propagation in the thin film. The obtained all-optical inverter has a front (trailing) time constant of ∼55 μs (44 μs) for 1550 nm signal pulses and ∼7 kHz response bandwidth.

Tailorable Dynamics in Nonlinear Optical Metasurfaces.

Controlling light with light is essential for all-optical switching, data processing in optical communications and computing. Until now, all-optical control of light has relied almost exclusively on nonlinear optical interactions in materials. Achieving giant nonlinearities under low light intensity is essential for weak-light nonlinear optics. In the past decades, such weak-light nonlinear phenomena have been demonstrated in photorefractive and photochromic materials. However, their bulky size and slow speed have hindered practical applications. Metasurfaces, which enhance light-matter interactions at the nanoscale, provide a new framework with tailorable nonlinearities for weak-light nonlinear dynamics. Current advances in nonlinear metasurfaces are introduced, with a special emphasis on all-optical light controls. The tuning of the nonlinearity values using metasurfaces, including enhancement and sign reversal is presented. The tailoring of the transient behaviors of nonlinearities in metasurfaces to achieve femtosecond switching speed is also discussed. Furthermore, the impact of quantum effects from the metasurface on the nonlinearities is introduced. Finally, an outlook on the future development of this energetic field is offered.

All-Optical Control of Light in Micro- and Nanophotonics

The pursuit of high-speed and chip-scale signal processing has promoted extensive exploration of all-optical control of light in micro- and nanophotonic platforms. All-optical switching and modulation are essential operations for optical communication systems and data networks and have been implemented by exploiting varieties of linear and nonlinear optical processes. In this regard, the optical control of materials’ refractive index is the primary technique, which facilitates the modulation of light attributes in a fast and reversible manner. A sustainable progress in the field of all-optical control primarily requires a deep understanding of optical phenomena that govern the manipulation of the refractive index. However, since most of such optical processes are intrinsically weak, utilizing resonating photonic structures of various kinds is often necessary to pave the way for the practical implementation of all-optical modulators for real-world applications. In this Perspective, we first present a conci...

Fiber all-optical light control with low-dimensional materials (LDMs): thermo-optic effect and saturable absorption.

In this paper, we review the recent studies on all-optical light control based on two main nonlinear mechanisms in LDMs: the thermo-optic effect and saturable absorption. The compactness of LDMs makes them the ideal medium for all-optical control systems. Many all-optical devices are demonstrated based on the properties of thermo-optic effects and saturable absorption. The materials characteristics and fabrication and the future prospects for all-optical control will also be shown.

Resonance-assisted light–control–light characteristics of SnS2 on a microfiber knot resonator with fast response

An all-optical light–control–light functionality with the structure of a microfiber knot resonator (MKR) coated with tin disulfide (SnS2) nanosheets is experimentally demonstrated. The evanescent light in the MKR [with a resonance Q of ∼59,000 and an extinction ratio (ER) of ∼26 dB] is exploited to enhance light–matter interaction by coating a two-dimensional material SnS2 nanosheet onto it. Thanks to the enhanced light–matter interaction and the strong absorption property of SnS2, the transmitted optical power can be tuned quasi-linearly with an external violet pump light power, where a transmitted optical power variation rate ΔT with respect to the violet light power of ∼0.22 dB/mW is obtained. In addition, the MKR structure possessing multiple resonances enables a direct experimental demonstration of the relationship between resonance properties (such as Q and ER), and the obtained ΔT variation rate with respect to the violet light power. It verifies experimentally that a higher resonance Q and a larger ER can lead to a higher ΔT variation rate. In terms of the operating speed, this device runs as fast as ∼3.2 ms. This kind of all-optical light–control–light functional structure may find applications in future all-optical circuitry, handheld fiber sensors, etc.

Highly sensitive all-optical control of light in WS2 coated microfiber knot resonator.

All-optical light-control-light functionality is realized in a layered tungsten disulfide (WS2) nanosheet coated microfiber knot resonator (MKR) structure. Mainly due to the photon generated excitons induced refractive index variation in WS2 nanosheets, a large variation in the transmitted power (∆T) can be observed under external violet/red laser excitation. The ∆T variation rates can reach up to ~0.4 dB/mW under violet pump light excitation whereas the state of the art light-control-light structures usually has a variation rate of less than 0.25 dB/mW. In terms of the response time, the averaged rise/fall time is ~0.12/0.1 s. The demonstrated structure has the advantages of easy fabrication, low cost and high sensitivity, therefore, it might be a promising candidate for building future all-fiber-optics based functional devices and all-optical circuitry.

Multichannel and Binary-Phase All-Optical Control with On-Chip Integrated Subwavelength Plasmonic Waveguides

The control of light with light at a nanometer scale is a fundamental issue in optics. In this study, we demonstrate nanoscale all-optical control of light based on linear optics in an on-chip integrated subwavelength plasmonic waveguide system. The signal intensities of multiple output channels are all-optically manipulated simultaneously in various manners by coupling the fields of a standing wave in the main waveguide to the nearby subwavelength branch waveguides. More importantly, the phase differences between different output channels equal either 0 or π, thereby exhibiting an interesting binary characteristic. This phenomenon provides both phase robustness and switchable features, which significantly facilitate further applications at nanometer scales. As a demonstration, two output channels are used to drive a two-element plasmonic nanoantenna, and the dynamical control of the emission direction of the nanoantenna is successfully presented. The proposed control mechanism displays an ultrafast respo...

All-optical control of light on a graphene-on-silicon nitride chip using thermo-optic effect

All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms (e.g., silicon and III-V semiconductors). However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions. Instead, silicon nitride (Si3N4) provides a possibility to realize all-optical large-scale integrated circuits due to its insulator nature without TPA and FCA. In this work, we investigate the physical dynamics of all-optical control on a graphene-on-Si3N4 chip based on thermo-optic effect. In the experimental demonstration, a switching response time constant of 253.0 ns at a switching energy of ~50 nJ is obtained with a device dimension of 60 μm × 60 μm, corresponding to a figure of merit (FOM) of 3.0 nJ mm. Detailed coupled-mode theory based analysis on the thermo-optic effect of the device has been performed.

Dynamics of the light-induced atomic desorption at homogeneous illumination

An experimental investigation of Light-Induced Atomic Desorption (LIAD) at homogeneous illumination in uncoated Rb glass cell is reported. The dynamics parameters of LIAD and their dependences on the illumination intensity in uncoated cell are measured and compared with these in paraffin-coated cell and the theoretical dependences for coated cell at homogeneous illumination. The homogeneous illumination not only increases the yield of LIAD, but increases the rates of desorption and adsorption. The results are interesting for the better understanding of the process of LIAD and the atom-surface interaction, for the development of new LIAD-loaded atomic devices, all-optical control of light, optical sensors miniaturization, and new methods for surface and coating diagnostics and nanostructuring.

Large optical nonlinearity of ITO nanorods for sub-picosecond all-optical modulation of the full-visible spectrum.

Nonlinear optical responses of materials play a vital role for the development of active nanophotonic and plasmonic devices. Optical nonlinearity induced by intense optical excitation of mobile electrons in metallic nanostructures can provide large-amplitude, dynamic tuning of their electromagnetic response, which is potentially useful for all-optical processing of information and dynamic beam control. Here we report on the sub-picosecond optical nonlinearity of indium tin oxide nanorod arrays (ITO-NRAs) following intraband, on-plasmon-resonance optical pumping, which enables modulation of the full-visible spectrum with large absolute change of transmission, favourable spectral tunability and beam-steering capability. Furthermore, we observe a transient response in the microsecond regime associated with slow lattice cooling, which arises from the large aspect-ratio and low thermal conductivity of ITO-NRAs. Our results demonstrate that all-optical control of light can be achieved by using heavily doped wide-bandgap semiconductors in their transparent regime with speed faster than that of noble metals.

Anomalous nonlinear absorption in epsilon-near-zero materials: optical limiting and all-optical control.

We investigate nonlinear absorption in films of epsilon-near-zero materials. The combination of large local electric fields at the fundamental frequency and material losses at the harmonic frequencies induce unusual intensity-dependent phenomena. We predict that the second-order nonlinearity of a low-damping, epsilon-near-zero slab produces an optical limiting effect that mimics a two-photon absorption process. Anomalous absorption profiles that depend on low permittivity values at the pump frequency are also predicted for third-order nonlinearities. These findings suggest new opportunities for all-optical light control and novel ways to design reconfigurable and tunable nonlinear devices.

Optical bistability in Ag-Al2O3 one-dimensional photonic crystals

Here, we demonstrate the nonlinear optical responses of Ag-Al2O3 one-dimensional photonic crystals (1D PCs). The linear transmission spectra of the proposed 1D PC show higher transmission at shorter wavelengths and lower transmission at longer wavelengths with “N” pairs of Ag-Al2O3 will support “N − 1” transmission peaks. By using 5 pairs of Ag-Al2O3, the optical bistability behavior of light transmission at low input intensity for the resonant modes is numerically demonstrated. Then, we performed a Z-scan experimental technique to show the enhanced nonlinear optical transmission of Ag-Al2O3 1D PC. These results can pave the way for achieving all-optical control of light for potential applications such as all-optical switching, optical logic, optical computation, etc.

Localized structures in dissipative media: from optics to plant ecology.

Localized structures (LSs) in dissipative media appear in various fields of natural science such as biology, chemistry, plant ecology, optics and laser physics. The proposal for this Theme Issue was to gather specialists from various fields of nonlinear science towards a cross-fertilization among active areas of research. This is a cross-disciplinary area of research dominated by nonlinear optics due to potential applications for all-optical control of light, optical storage and information processing. This Theme Issue contains contributions from 18 active groups involved in the LS field and have all made significant contributions in recent years.

All-optical switching of silicon disk resonator based on photothermal effect in metal-insulator-metal absorber.

Efficient narrowband light absorption by a metal-insulator-metal (MIM) structure can lead to high-speed light-to-heat conversion at a micro- or nanoscale. Such a MIM structure can serve as a heater for achieving all-optical light control based on the thermo-optical (TO) effect. Here we experimentally fabricated and characterized a novel all-optical switch based on a silicon microdisk integrated with a MIM light absorber. Direct integration of the absorber on top of the microdisk reduces the thermal capacity of the whole device, leading to high-speed TO switching of the microdisk resonance. The measurement result exhibits a rise time of 2.0μs and a fall time of 2.6μs with switching power as low as 0.5mW; the product of switching power and response time is only about 1.3 mW·μs. Since no auxiliary elements are required for the heater, the switch is structurally compact, and its fabrication is rather easy. The device potentially can be deployed for new kinds of all-optical applications.

Discrete photonics resonator in coupled waveguide arrays.

We demonstrate both theoretically and experimentally that discrete diffraction resonance can be designed, fabricated, and successfully probed in functionalized - guidonic - coupled waveguide arrays. We evidence that double-barrier patterning of the coupling creates wavelength-independent angular tunnel resonance in the transmitted and the reflected intensity of light beams freely propagating in the plane of the array. Transmission peaks obtained are associated with resonant excitation of the engineered array bound supermodes of the functionalized array, in agreement with accurate and practical numerical modeling based on extended coupled-mode theory. The linear operation of the guidonic resonant tunneling double barrier makes up an original resonator for discrete photonics, suitable for all-optical control of light.

The mobility of nonlocal solitons in fading optical lattices

We study the soliton mobility in nonlocal nonlinear media with an imprinted fading optical lattice. The results show that the transverse mobility of solitons varies with the lattice decay rate and the nonlocality degree, which provides an opportunity for all-optical control of light.