Optical Switching Devices Research Articles

A Narrow Dual-Band Monolayer Unpatterned Graphene-Based Perfect Absorber with Critical Coupling in the Near Infrared

The combination of critical coupling and coupled mode theory in this study elevated the absorption performance of a graphene-based absorber in the near-infrared band, achieving perfect absorption in the double bands (98.96% and 98.22%), owing to the guided mode resonance (the coupling of the leak mode and guided mode under the condition of phase matching, which revealed 100% transmission or reflection efficiency in the wavelet band), and a third high-efficiency absorption (91.34%) emerged. During the evaluation of the single-structure, cross-circle-shaped absorber via simulation and theoretical analysis, the cross-circle shaped absorber assumed a conspicuous preponderance through exploring the correlation between absorption and tunable parameters (period, geometric measure, and incident angle of the cross-circle absorber), and by briefly analyzing the quality factors and universal applicability. Hence, the cross-circle resonance structure provides novel potential for the design of a dual-band unpatterned graphene perfect absorber in the near-infrared band, and possesses practical application significance in photoelectric detectors, modulators, optical switching, and numerous other photoelectric devices.

Optical Polarization Sensitive Ultra-Fast Switching and Photo-Electrical Device.

Ultra-fast electrical switches activated with an optical-polarized light trigger, also called photo-polarized activated electrical switches, are presented. A set of new transistor circuits is switched by light from above, illuminating deep V-grooves, whose angle is sensitive to the polarization of the incident. Thus, this application may serve for encryption/decryption devices since the strongest electrical responsivity is only obtained for very specific spatial polarization directions of the illumination beam. When this V-groove is sufficiently narrow, the device mainly responds to one polarization and not to the other. In such a way, electrons are generated only for one specific polarization. While the nature of the data remains electronic, the modulation control is optic, creating a photo-induced current depending on the polarization direction. This coupled device acts as a polarization modulator as well as an intensity modulator. The article focuses on the integration of several devices in different configurations of circuitry: dual, triple, and multi-element. Case studies of several adjacent devices are presented with varying critical variables, such as the V-groove aperture dimensions. Analytical models and complementary numerical analyses are presented for the future smooth integration into Complementary Metal-Oxide-Semiconductor (CMOS) technology.

Tunable Plasmon-Induced Transparency in Dual Hexagonal Resonators With Rotatable Embedded Bar

In this paper, tunable plasmon-induced transparency (PIT) is achieved in a novel and compact plasmonic system which consists of dual hexagonal resonators with rotatable rectangular bar embedded in resonators and a metal-insulator-metal (MIM) waveguide. The proposed structure is numerically investigated by finite-difference time-domain (FDTD) method. The numerical simulation results reveal that by rotating the embedded bar to different angles, PIT can realize in different wavelengths. Tunability in transparency peak wavelength, transmission, and optical delay are also obtained when the angle of embedded bars are changed. In addition, the influences of other structural parameters on transmission and optical delay are analyzed in detail. This proposed structure may provide a novel manipulation for tunable PIT and potentially be applied in highly integrated optical storage and switch devices.

An optical switch based on a Mn–CuInS thin film

Low-toxicity zinc blende Mn–CuInS (MCIS) thin films and a corresponding optical switch were fabricated and examined using multiple measurements. Transient absorption spectroscopy indicated that multiple carrier processes occurred during carrier relaxation. The optical switch devices showed good responsivity and stability. The kinetics of the photo-generated charge carriers were affected by carrier concentration and showed no electric-field dependence. These prepared devices showed potential for rapid photodetection applications.

Dispersed-Monolayer Graphene-Doped Polymer/Silica Hybrid Mach-Zehnder interferometer (MZI) Thermal Optical Switch with Low-Power Consumption and Fast Response.

This article demonstrates a dispersed-monolayer graphene-doped polymer/silica hybrid Mach–Zehnder interferometer (MZI) thermal optical switch with low-power consumption and fast response. The polymer/silica hybrid MZI structure reduces the power consumption of the device as a result of the large thermal optical coefficient of the polymer material. To further decrease the response time of the thermal optical switch device, a polymethyl methacrylate, doped with monolayer graphene as a cladding material, has been synthesized. Our study theoretically analyzed the thermal conductivity of composites using the Lewis–Nielsen model. The predicted thermal conductivity of the composites increased by 133.16% at a graphene volume fraction of 0.263 vol %, due to the large thermal conductivity of graphene. Measurements taken of the fabricated thermal optical switch exhibited a power consumption of 7.68 mW, a rise time of 40 μs, and a fall time of 80 μs at a wavelength of 1550 nm.

Ultrafast Plasmonic Optical Switching Structures and Devices

[This submission is based on the contacts with Prof. Pavesi by code JMDC(100%.2019.FPHY.832).] Plasmonic structures possess rich physics related to the sensitivity of plasmon resonance to the change in the environmental dielectric constant, the enhanced light scattering and optical extinction, and the local field enhancement enabled strong light-matter interactions, which have been applied in refractive-index sensors, optical feedback in various micro- or nano-cavity lasers, surface enhanced Raman scattering spectroscopy, and high-sensitivity molecular detection. However, ultrafast optical response is another important aspect of plasmons, which can be utilized to achieve switching of optical signals in different spectral bands. These optical switching designs are very important for applications in optical logic circuits and optical communication system. In this review, we summarize a series of reports on ultrafast plasmonic optical switches, where we focus our discussions on the structural and device designs, instead of on their physics. By categorizing the designs of optical switches into different groups by their featured performances, we intend to propose the development trend and the commonly interested mechanisms of such ultrafast optical switches. We hope this review will supply helpful concepts and technical information for further development and new applications of ultrafast optical switching devices.

Dopant-induced photoresponsivity in coumarin-dye-sensitized nanowire NiO/p-Si heterojunction

This article presents dopant-induced photoresponsivity in Coumarin (CO)-dye-sensitized nanowire NiO/p-Si. The photoresponse modulation of Al/CO doped NiO/p-Si/Al heterojunction relates to different configurations of NiO under light. This performance is controlled by different concentration of CO-doping based on calcination and carbon (C) incorporation of NiO. Some electronic parameters are determined (the rectification ratio RR, the engineered ideality factor n and barrier height φb). CO doped NiO/p-Si photodiode can be designed as light-switchable systems with the tunable ON and OFF states. The capacitance (C)-time (s) measurements show that the heterojunction has photocapacitive behavior as a result of the doping amount of CO in NiO. Results show that we should pay more attention to the influence of CO dye on metal oxides and/or NiO for the optical switching devices and photodiode.

Dynamic Tuning of Optical Transmittance of 1D Colloidal Assemblies of Magnetic Nanostructures

Smart materials with switchable optical properties may find interesting applications in designing advanced intelligent systems. Herein, the dynamic tuning of optical transmission is reported by controlling the orientation of 1D colloidal assemblies of magnetic nanostructures. Colloidal magnetic nanostructures of Fe3O4, including nanospheres, nanorods, and nanodiscs, are assembled into 1D chains under external magnetic fields. Magnetic tuning of the orientation of the nanochains results in a pronounced contrast in optical transmittance, which is strongly dependent on the size and shape of the primary nanostructures. Contrary to the intuitive expectation, the 1D chains of the nanospheres and nanorods exhibit lower transmittance when they are oriented parallel rather than perpendicular to the incident light, whereas the nanodisc counterpart responds oppositely due to the unique “edge‐to‐edge” assembly mode of the nanodiscs. The dynamic tuning of the optical transmittance through magnetic means is believed to have broad applications in the design of novel switchable optical devices. As an example, the incorporation of orientation‐dependent optical properties of 1D chains into the construction of intelligent polymer films with their transparency sensitive to rotation and bending is demonstrated.

Array of Mach Zehnder Modulators for Realization of Parity Generator/Checker

The electro-optic effect is one of the most important techniques for modulation and switching purpose in optical communication. The Mach–Zehnder interferometer (MZI) structure functioning on the principle of electro-optic effect behaves as the influential optical switching device. This paper contains discussion of electro-optic effect based MZI structure and its efficient application to construct parity generator and checker. Titanium (Ti) in-diffused lithium niobate profile of MZI through computer simulation has been used for this purpose. Basic 2*2 switch is transformed as MZI for the design of parity device over a functional wavelength range of 1.3 µm to 1.65µm. This simulated design is analyzed with different Ti-LiNbO3 stripe thicknesses, in order to attain the optimum Ti-LiNbO3 stripe thickness and also to improve the performance of the switch on its crosstalk, power imbalance, extinction ratio and transition losses. The simulation model of proposed optical parity device has been implemented using the OptiBPM and OptiSystem softwares have been used for suitable verification of the discussed schemes.

Facile preparation of high fluorescent carbon quantum dots from orange waste peels for nonlinear optical applications.

A facile and eco-friendly hydrothermal method was used to prepare carbon quantum dots (CQDs) using orange waste peels. The synthesized CQDs were well dispersed and the average diameter was 2.9±0.5nm. Functional group identification of the CQDs was confirmed by Fourier transform infrared spectrum analysis. Fluorescence properties of the synthesized CQDs exhibited blue emission. The fluorescence quantum yield of the CQDs was around 11.37% at an excitation wavelength of 330nm. The higher order nonlinear optical properties were examined using a Z-scan technique and a continuous wave laser that was operated at a wavelength of 532nm. Results demonstrated that the synthesis of CQDs can be considered as promising for optical switching devices, bio-scanning, and bio-imaging for optoelectronic applications.

VO2 film with small hysteresis width and low transition temperature

In this paper, we investigate the vanadium dioxide (VO2) film as optical switching deposited on Al doped zinc oxide (AZO) glass substrates by DC reactive magnetron sputtering. Field-emission scanning electron microscopy reveal that the deposited VO2 film consists of irregular nanostructured grains. The optical tests by means of UV–visible spectrophotometer show that the deposited VO2 film exhibits excellent optical switching properties with a very small phase-transition hysteresis width of 2.9 °C as well as a low phase-transition temperature of about 48 °C. More interesting, the semiconductor-to-metal transition is readily induced by Joule heat produced by electrical current through the AZO conductive layer, which is more efficient and convenient compared with the traditional heating of the sample by heating plate. This work is of crucial importance for potential applications of VO2 film in compact optical switching devices.

Ultra-sharp Plasmonic Super-cavity Resonance and Light Absorption

Nano-structured metals have attracted a great amount of attention in recent years due to the exciting plasmonic and photonic properties. However, the intrinsic high loss of the metals inevitably leads to the low-Q plasmonic resonance, hampering numerous applications on optoelectronics. Here, we demonstrate an ultra-sharp light absorber platform by an optical nano-cavity coupled plasmonic grating. The introduced dielectric nano-cavity not only provides strong optical field localization with the incident light but also enhances the hybridization coupling with the surface plasmons of the metal nano-structure, which eventually produces the plasmonic super-cavity resonance with the spectral bandwidths down to sub-nanometer scale and the spectral Q factor up to ~1 03. Moreover, the spectral slope reaches 52.8%/nm, indicating a sharp lineshape. Near-unity absorption with A of 99.7% is simultaneously achieved. These features suggest the designing such plasmonic-photonic hybridized super-cavity structure being a promising route for achieving ultra-sharp light absorber, which can be utilized as subtractive monochromatic filters, plasmonic and optical switch devices, photo-thermal sensors, and biochemical detectors.

Layer-modulated two-photon absorption in MoS2: probing the shift of the excitonic dark state and band-edge

Questions hovering over the modulation of bandgap size and excitonic effect on nonlinear absorption in two-dimensional transition metal dichalcogenides (TMDCs) have restricted their application in micro/nano optical modulator, optical switching, and beam shaping devices. Here, degenerate two-photon absorption (TPA) in the near-infrared region was studied experimentally in mechanically exfoliated MoS2 from single layer to multilayer. The layer-dependent TPA coefficients were significantly modulated by the detuning of the excitonic dark state (2p). The shift of the quasiparticle bandgap and the decreasing of exciton binding energy with layers were deduced, combined with the non-hydrogen model of excitons in TMDCs and the scaling rule of semiconductors. Our work clearly demonstrates the layer modulation of nonlinear absorption in TMDCs and provides support for layer-dependent nonlinear optical devices, such as optical limiters and optical switches.

Design and development of plasmonic and nanophotonic devices

Research work at Dr. Anuj Dhawan’s laboratory at IIT Delhi is primarily based on the design and development of nanophotonic and plasmonic devices. Dr. Dhawan’s research group has primarily focused on the design and modeling of plasmonic chemical and biological sensors, optical switches, and photonic waveguides and interconnects. In this paper, firstly research work carried out in Dr. Dhawan’s laboratory on sensor devices based on surface plasmon resonance, localized surface plasmon resonance, and surface-enhanced Raman scattering, is described. Subsequently, the research work being carried out in Dr. Dhawan’s laboratory on fabrication of plasmonic nanostructures and their characterization, is discussed. Finally, EM modeling of optical switching devices—consisting of a plasmonic nanostructure system consisting of an array of gold nanowires separated from an underlying gold film by a vanadium dioxide thin film spacer layer—is discussed.

Study of transmission property of periodic layer consisting of SiO2 and TiO2 layers with anisotropic liquid crystal (LC) and LiNbO3 as defect layers for optical switching

Abstract This paper reports the theoretical investigation of transmission properties of a one-dimensional periodic layer consisting of SiO2 and TiO2 layers with anisotropic liquid crystal (LC) and LiNbO3as defect layers with the variation of incident angle, temperature and applied a voltage across the crystal. The optical transmission properties of the considered structure have been calculated by using a 4 × 4 transfer matrix method (TMM). The transmittance of the considered structure with LC and LiNbO3as defects gives rise to defect mode wavelength peak inside the bandgap region. The transmittance peak of the defect mode shows the blue shift in the transmission of periodic structure for TE and TM polarizations with incident angle, applied voltage, and temperature. Further, the transmission behavior of defect modes and terminal wavelengths are analyzed with the variation of incident angle and temperature. The transmission of the considered structure has found the tunable characteristics due to the presence of anisotropic defect layer LC and LiNbO3. The one-dimensional periodic layer consisting of SiO2 and TiO2 layers with the defect layers of anisotropic materials, liquid crystal (LC) and LiNbO3, as may be used to design optical switching devices.

Wide temperature range of an electrically tunable selective reflection of light by oblique helicoidal cholesteric

ABSTRACTOblique helicoidal cholesteric liquid crystals (ChOH) offer an unprecedented opportunity to tune selective reflection of light in a broad spectral range from ultraviolet to infrared by an electric field. The major problem is that the temperature range of stable ChOH is typically above the room temperature and is relatively narrow, a few degrees. In this work, we demonstrate that by using a mixture of flexible dimeric and rod-like molecules, one can significantly expand the temperature range of intense Bragg reflection, from 16°C to 27°C. We demonstrate that the selective reflection peak, reflection intensity, bandwidth and threshold electric field are all temperature dependent and discuss the associated mechanisms. The results show that both the electric field and temperature can be used to tune the structural colour of oblique helicoidal cholesteric structures. The proposed material can be used in switchable optical devices based on liquid crystals, such as light modulators, indoor smart windows, and filters.

Optical temperature sensor and switch controlled by competition between phonon and polarization dressing in Pr3+:YSO

We explore the alteration that occurs in Autler–Townes (AT) splitting caused by the competition of phonon intensity and polarized dressing fields in second-order fluorescence (FL) signals in both the spectral and the time domain. By varying the polarization dressing along with temperature, we control the AT-splitting of the FL signal. Furthermore, we analyze the noise correlation and squeezing of spontaneous four-wave mixing (SP-FWM) to investigate the effect of phonon and polarized dressing fields. These results are applied for optical temperature sensors and switching devices, which can be controlled by the competition between phonon and polarization dressing. Optical temperature sensor sensitivity and switching speeds are 96% and 15 ns, respectively.

Ultrafast nonlinear transparency driven at a telecom wavelength in an organic semiconductor system

Ultrafast laser-induced transparency is demonstrated using femtosecond (fs) pump-probe experiments in the organic P3HT:PCBM (donor:acceptor) blend structure. For above band gap pumping, ultrafast transient signals strongly depend on the probe photon energy. Most intriguingly, for below band gap pumping at 0.95 eV, or 1.3 µm at a telecom wavelength, a huge transmission increase up to 30% only during the laser pulse ∼100 fs is observed as a pump-driven, quasi-instantaneous suppression of absorption for the high photon-energy energy probe beam. We attribute the observed laser-driven transparency to dynamic Franz-Keldysh effect, at least one order of magnitude stronger compared to the multiphoton nonlinearities. Our results may be used for development of low-cost, beyond 100 Gbit/s optical switching devices.

Multifunctional TiO2/ormosils organic-inorganic hybrid films derived by a sol-gel process for photonics and UV nanoimprint applications

Multifunctional TiO2/ormosils organic-inorganic hybrid films that contain azobenzene and photosensitive groups are prepared by combining a low temperature sol-gel process and a spin-coating technique. The optical waveguide and the structural properties of the hybrid films are characterized and investigated respectively by different techniques. The photo-responsive properties of the hybrid films are induced by a photo-irradiation under UV light at a wavelength of 365 nm. Finally, micro-lens arrays are built in the hybrid films by using a UV soft imprint technique. These results indicate that the as prepared hybrid films with multifunctional photonic properties are promising candidates for integrated optics and photonic applications, which would allow the direct integration onto a single chip of the optical micro-elements and the optical data storage and optical switching devices.

Nonlinear absorption and optical limiting of Ag–CdSe nano-hybrids of different growth times

Metal-semiconductor Nano-composites have enormous applications due to Plasmon –exciton coupling. Open aperture Z-scan is investigated for Ag–CdSe hybrid nanostructure, a toggle from saturable absorption process SA to reverse saturable absorption RSA is observed upon laser power increment. Proofs of crystal and morphological structure are given by selected area electron diffraction (SAED) and high resolution transmission electron microscope (HRTEM). Red shifting in photoluminescence spectra PL is observed which is ascribed to the particle size increment. Intriguing nonlinear findings can be used to engineer optical switching devices and optical limiters.