Ultrafast All-optical Switching Research Articles

Si-CMOS compatible epsilon-near-zero metamaterial for two-color ultrafast all-optical switching

Driven by the escalating demands of advanced technologies, developing integration strategies has kept pace with the realization of ultrafast components during the past two decades. Ultrafast all-optical switches enabled by artificial materials are considered at the forefront of the next generation of photonic integration for communications and high-volume data processing. Encouraged by these advancements, applications, and interest have increased toward all-optical switches based on epsilon-near-zero (ENZ) materials. However, some all-optical switches lack CMOS compatibility, require high energy activation, and are limited in switching speed and working wavelength. Here, we propose and demonstrate a multilayered ENZ metamaterial utilizing Si-compatible titanium nitride and indium-tin-oxide materials with two effective working wavelengths in the visible and near-infrared spectrum. This device enables switching time down to a few hundred femtoseconds utilizing minimal energy at the corresponding ENZ regions induced by intraband pumping. Our approach can enhance the adaptability of designing ENZ metamaterials for new hybrid integrated photonic components for low-power ultrafast all-optical terahertz modulation.

All-optical high-contrast femtosecond switching using nonlinearity from an epsilon-near-zero effect in plasmonic metamaterials.

Metamaterials opened a new realm to control light-matter interactions at sub-wavelength scale by engineering meta-atoms. Recently, the integration of several emerging nonlinear materials with metamaterial structures enables ultra-fast all-optical switching at the nanoscale and thus brings enormous possibilities to realize next-generation optical communication systems. This Letter presents a novel, to the best of our knowledge, design of plasmonic metamaterials for high-contrast femtosecond all-optical switching. We leverage magnetic plasmon (MP) resonance combined with the nonlinear effects of an epsilon-near-zero (ENZ)-material. The proposed design comprises a periodic array of two closely spaced Au-nanogratings deposited on an optically thick Au-substrate to excite MP-resonance. To enable a dynamically tunable resonance, the nanogrooves in meta-atoms are filled with an ENZ-material, cadmium-oxide (CdO). The intraband transition-induced optical nonlinearities in the ENZ-medium are studied using a two-temperature model. The MP-resonance ensures strong light-matter interactions enabling enhancement of the nonlinearities of the proposed structure. We observe that the pump-induced refractive index change in the CdO layer causes a redshift of the MP-resonance dip wavelength in the reflectance spectrum, leading to a high modulation depth of 0.83 at 1.55 µm. With an ultra-fast response time of 776 fs while maintaining a low pump-fluence of 75 µJ/cm2, the proposed metamaterial could help in realizing switches for next-generation optical computation systems.

Spatial Writing of Ultrafast All-Optical Switching.

Writing spatial information on ultrafast all-optical switching is essential for constructing ultrafast processing units in photonic applications, such as optical communication and computing networks. However, most methods ignore the fabrication and imaging of controllable switching area, limiting its spatial information and the further design in ultrafast devices. Here, we propose a method to spatially write in ultrafast all-optical switching based on MAPbI3 perovskite with nanocone structure and visualize the switching effect in arbitrary designed area. Due to the light confinement effect of nanocone fabrication using a fs laser, the light is strongly absorbed by perovskite and reach saturable absorption. It leads to ultrafast broadband transmittance change with 25 fs switching time and 10% modulation depth in nanocone perovskite area. Our preparation method offers high efficiency, performance, and flexibility for the spatial writing of ultrafast all-optical switching, which is promising for developing ultrafast all-optical networks and the next generation of communication technology.

All-optical ultrafast polarization switching with nonlinear plasmonic metasurfaces.

Optical switching has important applications in optical information processing, optical computing, and optical communications. The long-term pursuit of optical switch is to achieve short switching time and large modulation depth. Among various mechanisms, all-optical switching based on Kerr effect represents a promising solution. However, it is usually difficult to compromise both switching time and modulation depth of a Kerr-type optical switch. To circumvent this constraint, symmetry selective polarization switching via second-harmonic generation (SHG) in nonlinear crystals has been attracting scientists' attention. Here, we demonstrate SHG-based all-optical ultrafast polarization switching by using geometric phase controlled nonlinear plasmonic metasurfaces. A switching time of hundreds of femtoseconds and a modulation depth of 97% were experimentally demonstrated. The function of dual-channel all-optical switching was also demonstrated on a metasurface, which consists of spatially variant meta-atoms. The nonlinear metasurface proposed here represents an important platform for developing all-optical ultrafast switches and would benefit the area of optical information processing.

Asymmetric Laser Field Interaction with MXene Coated on the Side Surface of Optical Fibers for Ultrafast Nonlinear Switches.

In recent years, there has been significant interest in researching ultrafast nonlinear optical phenomena involving light-matter interactions in two-dimensional (2D) materials, owing to their potential applications in optics and photonics. MXene, a recently developed 2D material, has garnered considerable attention due to its graphene-like properties and highly tunable electronic/optical characteristics. Herein, we demonstrate ultrafast all-optical switches based on four-wave-mixing (FWM) utilizing the nonlinear optical property of MXene Ti3C2Tx. In order to realize the device, we deposited multilayered Ti3C2Tx in the form of a supernatant solution onto the polished surface of a side-polished optical fiber, enabling the interaction of Ti3C2Tx with the asymmetric evanescent field of the incident input. We systematically characterized the nonlinear optical responses derived from the Ti3C2Tx layers. The fabricated device exhibits notable performance metrics, an enhancement of the extinction ratio, and a conversion efficiency of the newly generated signal, displaying 5.3 and 5.2 dB, respectively. Additionally, the device operates at high modulation frequencies, reaching up to 20 GHz, and demonstrates high-resolution detuning with channel distances of up to 15 nm. Our findings highlight the potential of MXene-based materials for ultrafast optical data management systems.

Gd Doping at the Co/Pt Interfaces to Induce Ultrafast All-Optical Switching

Gd Doping at the Co/Pt Interfaces to Induce Ultrafast All-Optical Switching

All-optical switching based on coherent control of metasurface

In this paper, we propose a novel method to design ultrafast all-optical switchings based on the coherent perfect absorption principle of metasurface. Using the coherent interaction between two beams of coherent light and the metasurface, the absorption can be modulated between 0.3% and 98. 3%. Since no nonlinear dielectric is used, the ultrafast all-optical switching function can be achieved at arbitrary low intensity conditions. We further studied the mechanism of resonant absorption on metasurface, and analyzed the influence of geometric parameters on resonant absorption. Through time-domain simulation analysis, when the incident laser pulse duration is 40 fs, the switching response time is 82 fs, which provides a switching contrast ratio of more than 108.

Ultrafast single-pulse all-optical switching in synthetic ferrimagnetic Tb/Co/Gd multilayers

In this work, we investigate single-shot all-optical switching (AOS) in Tb/Co/Gd/Co/Tb multilayers in an attempt to establish AOS in synthetic ferrimagnets with high perpendicular magnetic anisotropy. In particular, we study the effect of varying Tb thicknesses to disentangle the role of the two rare-earth elements. Even though the role of magnetic compensation has been considered to be crucial, we find that the threshold fluence for switching is largely independent of the Tb content. Moreover, we identify the timescale for the magnetization to cross zero to be approximately within the first ps after laser excitation using time-resolved magneto–optic Kerr effect. We conclude that the switching is governed mostly by interactions between Co and Gd.

Experimental research on specially optical bistability based on atomic ensemble

Optical bistability (OB) phenomenon based on electromagnetic induced transparency has received widespread attention from researchers due to its good application prospects in ultrafast all-optical switches, high-speed all-optical exchange devices, optical storage, etc. In this paper, OB is realized in a thermal atomic ensemble by a probe transmission signal and a six-wave mixing signal. By adjusting the controllable parameters of the light field, such as the light field intensity, polarization state, incident angle of the light etc, the OB laws of related signal are discovered, analyzed, and summarized. These results will have potential application value in OB devices and signal processing.

Ultrafast All-Optical Switching Using Doped Chromoprotein Films

Next-generation communication networks require > Tbit/s single-channel data transfer and processing with sub-picosecond switches and routers at network nodes. Materials enabling ultrafast all-optical switching have high potential to solve the speed limitations of current optoelectronic circuits. Chromoproteins exhibit a large light-controlled refractive index change alleviating the driving energy requirements for optical switching. Here, we report femtosecond transient grating experiments demonstrating the feasibility of < 200 fs all-optical switching by hydrated thin films of photoactive yellow protein and compare the results with those obtained using bacteriorhodopsin. Possibilities for the practical utilization of the scheme in extremely high-speed optical modulation and switching/routing with nominally infinite extinction contrast are discussed.

Modeling of Polarization-Conversion and Rotation-Based Ultrafast All-Optical Ternary Logic Switch Using Microring Resonator

Modeling of Polarization-Conversion and Rotation-Based Ultrafast All-Optical Ternary Logic Switch Using Microring Resonator

Au/MXene based ultrafast all-optical switching

Au/MXene based ultrafast all-optical switching

Multifunctional graphene metadevice using dual metamaterial induced transparency in terahertz regime

The dual metamaterial induced transparency (dual-MIT) phenomenon, which can be significantly tailored via the depolarization field effect of the graphene overlayer, is demonstrated in our fabricated multifunctional terahertz metastructures composed of unequal-lengthed 3-bar arrays. Those metasurfaces could actively manipulate the phase and group delay at various frequencies, as well as the different polarization conversion capability. The introduction of graphene reinforces the amplitude modulation of dual MITs and further reduces the quenched power by 4 times with a rotated angle. Combined with carrier dynamics, the dual-MIT transient regulation can realize an ultrafast all-optical switch with 2-time enhancement in modulation speed. Based on the advantage of the dual-MIT windows with different frequencies and magnitudes, we have illustrated the encrypted imaging on the erasure and reappearance of the target pattern. Our work provides a lower power consumption option for ultrafast all-optical switch and opens up the opportunities for future communication and information security in terahertz regime.

All-optical diffraction and ultrafast switching in a terahertz-driven quantized graphene system

Over the past few years, we have witnessed a substantial evolution in graphene optoelectronics. The tunability of the electronic structure of graphene has led to the next generation of carbon-based nano-photonic devices. Motivated by the unique optical properties of graphene, in the present work, we show that the landau-quantized graphene can be regarded as a platform for implementing a 2D laser-induced grating with high diffraction efficiency in the far-field regime. We consider a 2D doped graphene monolayer with a four-level system in Λ-configuration driven by a terahertz field. The electromagnetically induced Fraunhofer diffraction patterns are simulated for a weak probe field passing through the graphene nano-sheet. The optimum conditions for the maximum diffraction efficiency are investigated. Then, it is shown that the probe beam propagation can be coherently controlled via applying a terahertz field. The possibility of ultrafast all-optical switching of the probe beam is investigated. The proposed system may find applications in integrated nano-photonic devices for optical communications, infrared spectroscopy, astronomy, optical sensing, and also the realization of all-optical switching processes.

Ultrafast all-optical switching in a silicon-polymer compound slotted photonic crystal nanobeam cavity

Ultrafast all-optical switching in a silicon-polymer compound slotted photonic crystal nanobeam cavity

Ultrafast All-Optical Polarization Switch Controlled by Optically Excited Picosecond Acoustic Perturbation of Exciton Resonance in Planar Microcavities

All-optical switching of the polarization of exciton polaritons is studied using a picosecond acoustic perturbation of the exciton resonance in high-$Q$ planar $\mathrm{Ga}\mathrm{As}$/$\mathrm{Al}\mathrm{As}$ microcavities. An irreversible switching of the degree of circular polarization from $22\mathrm{%}$ up to $82\mathrm{%}$ is realized in a microcavity pumped by a laser with a photon energy slightly exceeding the lower polariton resonance. The polarization switch is performed by a short-term, about 30-ps-long, blueshift of the exciton energy of ($\mathrm{In},\mathrm{Ga}$)$\mathrm{As}$ quantum wells in the cavity active layer by a 10-ps strain pulse generated in the $\mathrm{Ga}\mathrm{As}$ substrate by a violet femtosecond laser pulse and injected into the microcavity. The proposed all-optical control of light polarization using acoustic modulation of a polariton resonance opens the way for fast and easily tunable optical polarization switches.

Bridging atomistic spin dynamics methods and phenomenological models of single-pulse ultrafast switching in ferrimagnets

We bridge an essential knowledge gap on the understanding of all-optical ultrafast switching in ferrimagnets, namely, the connection between atomistic spin dynamics methods and macroscopic phenomenological models. All-optical switching of the magnetization occurs after the application of a single femtosecond laser pulse to specific ferrimagnetic compounds. This strong excitation puts the involved degrees of freedom, electrons, lattice, and spins out-of-equilibrium between each other. Atomistic spin models have quantitatively described all-optical switching in a wide range of experimental conditions, while having failed to provide a simple picture of the switching process. Phenomenological models are able to qualitatively describe the dynamics of the switching process. However, a unified theoretical framework is missing that describes the element-specific spin dynamics as atomistic spin models with the simplicity of phenomenology. Here, we bridge this gap and present an element-specific macrospin dynamical model which fully agrees with atomistic spin dynamics simulations and symmetry considerations of the phenomenological models.

Broad-Band Ultrafast All-Optical Switching Based on Enhanced Nonlinear Absorption in Corrugated Indium Tin Oxide Films.

Ultrafast all-optical switches based on epsilon-near-zero (ENZ)-enhanced nonlinear refraction in transparent conducting oxides have achieved exciting results in realizing large absolute modulations. However, broad-band, polarization-independent, and wide-angle ultrafast all-optical switches have been challenging to produce, due to the inherent narrow band, polarization-dependent, and angle-dependent characteristics of the ENZ effect. To this end, we propose an ultrafast all-optical switch based on the enhanced nonlinear absorption of corrugated indium tin oxide (ITO) thin films. Taking advantage of the perfect absorption and localized field enhancement of the ENZ and localized surface plasmon resonance modes, we significantly enhanced the nonlinear absorption of the corrugated ITO film in the 1450-1650 nm telecom band. The experimental results show that the nonlinear saturable absorption coefficient of the corrugated ITO film at 1450 nm was as high as -1.5 × 105 cm GW-1, enabling all-optical switching to obtain an extinction ratio of 14.32 dB and an ultrafast switching time of 350 fs at a pump fluence of 18.51 mJ cm-2. Furthermore, the all-optical switch achieved an extinction ratio of over 15 dB and an insertion loss of approximately 2.6 dB within the 200 nm absorption band and exhibited polarization-independent and wide-angle features. The ultrafast temporal response can be attributed to intraband transient bleaching of the corrugated ITO film. Our findings demonstrate that corrugated ENZ films can overcome the inherent narrow-band, polarization-dependent, and angle-dependent problems of natural ENZ materials without increasing the response time, making them a potential ENZ ultrafast all-optical switching material platform.

Bistable soliton switching dynamics in a PT -symmetric coupler with saturable nonlinearity

We investigate the switching dynamics in a $\mathcal{PT}$-symmetric fiber coupler composed of a saturable nonlinear material as the core. In such a saturable nonlinear medium, bistable solitons may evolve due to the balance between dispersion and saturable nonlinearity, which we extend in the context of the $\mathcal{PT}$-symmetric coupler. Our investigations of power-controlled and phase-sensitive switching show richer soliton switching dynamics than the currently existing conventional counterparts, which may lead to ultrafast and efficient all-optical switching dynamics at very low power owing to the combined effects of $\mathcal{PT}$ symmetry and saturable nonlinearity. In addition to the input power, the relative phase of the input solitons and saturable coefficient are additional controlling parameters that efficiently tailor the switching dynamics. Also, we provide a suitable range of system and pulse parameters that would be helpful for the practical realization of the coupler to use in all-optical switching devices and photonic circuits. Finally, we develop a variational approach to analytically investigate the switching dynamics in such $\mathcal{PT}$-symmetric couplers that excellently predicts the numerical findings.

Investigating the influence of ITO thin film thickness on the optical Kerr nonlinearity using ultrashort laser pulses

In this paper, we present results from the measurements of the optical Kerr nonlinearity of indium tin oxide (ITO) thin films of different thicknesses using the femtosecond (fs) Z-scan technique. ITO thin films were prepared by radio frequency magnetron sputtering on a glass substrate at room temperature. The coated ITO thin films were subsequently characterized by UV–visible absorption spectroscopy, x-ray diffraction, and scanning electron microscopy. Using ∼ 100 f s pulses at 80 MHz repetition rate, the optical Kerr nonlinearity in ITO with different thicknesses was investigated at different excitation wavelengths and incident pulse energies. The optical Kerr nonlinearity was found to be dependent on excitation wavelength, incident power, and ITO thickness, with a maximum value of ∼ 9 × 1 0 − 12 c m 2 / W at a wavelength of 820 nm, power of 1 W, and 170 nm ITO thickness. These results suggest that Kerr nonlinearity in ITO can be tailored by varying the film thickness, which would be ideal for ultrafast all-optical switching in future optoelectronic devices.