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We propose a volatile static all-optical memory capable of storing phase information of a slowly-varying electric field. The scheme and its realization (a memory circuit) are based on two mutually coupled lasers subject to external optical injection. The proposed circuit has a single optical input for write and hold operations and two opposite-sign outputs for reading the memory. The proposed circuit operates with a single wavelength of light, a single direction of propagation, and without a need to switch the state of polarization. We prove mathematically that the proposed arrangement has equilibrium points that may discreetly quantify and store the phase in a bistable manner. The circuit is studied numerically for solid-state and semiconductor lasers with zero and non-zero linewidth enhancement factors, respectively. Simulations based on a rate equation system confirm the essential findings. Using typical parameters of a semiconductor laser and optimizing for a possibly wide range of operation, the write-read operations were simulated using PRBS-9 at the rate of 1 Gb/s with negligible errors. The proposed circuit will enable integrated memory implementations for future all-optical signal processing and computing systems.

An all-optical computer has remained an elusive concept. To construct a practical computing primitive equivalent to an electronic Boolean logic, one should utilize nonlinearity that overcomes weaknesses that plague many optical processing schemes. An advantageous nonlinearity provides a complete set of logic operations and allows cascaded operations without changes in wavelength or in signal encoding format. Here we demonstrate an all-optical majority gate based on a vertical-cavity surface-emitting laser (VCSEL). Using emulated signal coupling, the arrangement provides Bit Error Ratio (BER) of 10−6 at the rate of 1 GHz without changes in the wavelength or in the signal encoding format. Cascaded operation of the injection-locked laser majority gate is simulated on a full adder and a 3-bit ripple-carry adder circuits. Finally, utilizing the spin-flip model semiconductor laser rate equations, we prove that injection-locked lasers may perform normalization operations in the steady-state with an arbitrary linear state of polarization.

We report on the selection of contact metallisations for ZnSe-based metal-semiconductor-metal ultraviolet photo­de­tectors. Our evaluation is based on Ni/Au, Cr/Au, and hybrid Ag-nanowire contacts. Low values of dark current of 0.32 nA, 0.82 nA and 1.64 nA at bias voltage of 15 V were achieved for photodetectors with Ag-NW, Ni/Au and Cr/Au interdigital contacts, respectively. The best performance of our ZnSe-based ultraviolet photodetectors is observed for Ni/Au interdigital contacts. This is due to the higher Schottky barrier height, which is equal to ~ 1.49 eV for Ni/Au contacts in comparison with ~ 1.26 eV for Cr/Au contacts.A very high responsivity of 5.40 AW-1at bias voltage of 15 V for light with a wave­length of 325 nm is obtained for devices withNi/Auinterdigital contacts. Moreover, the maximum of photocurrent on/off ratio of 20342 and minimum of NEP of ~ 3 × 10-15 W Hz-1/2 at bias voltage of 15 V was achieved for this type of device.

All-optical signal processing remains an active field of research [1] , [2] . The fundamental challenge is the nature of photons that do not interact with each other but require a nonlinear medium. Majority gates have been proposed in a number of arrangements [3] , [4] , including injection-locked lasers [5] . Recently, we have demonstrated such an all-optical majority gate based on a vertical-cavity surface-emitting laser (VCSEL) [6] . Here we demonstrate numerically operation of a set of consequent majority gates based on injection locking technique taking into account noise in lasers. The operation principle is to transmit and process Phase-Shift Keyed (PSK) optical signal, and at the same time suppress the amplitude variation after each majority gate (make a normalization procedure, Fig. 1 ). We use here a special operation mode of a phase-locked laser suppressing the amplitude variations while keeping the phase modulation.

An analytical study of dynamical properties of a semiconductor laser with optical injection of arbitrary polarization is presented. It is shown that if the injected field is sufficiently weak, then the laser has nine equilibrium points, however, only one of them is stable. Even if the injected field is linearly polarized, six of the equilibrium points have a state of polarization that is elliptical. Dependence of the equilibrium points on the injected field is described, and it is shown that as the intensity of the injected field increases, the number of equilibrium points decreases, with only a single equilibrium point remaining for strong enough injected fields. As an application, a complex-valued optical neural network with working principle based on injection locking is proposed., Final version, to appear in SIAM Journal on Applied Dynamical Systems (SIADS)

This contribution deals with the investigation and characterisation of fully integrated broadband Terahertz (THz) Schottky diodes using silver (Ag) metallic nanowires (NWs) with 120 nm diameter as bridge contacts for zero-bias operating THz detectors based on highly doped Gallium Arsenide (GaAs) and Indium Gallium Arsenide (InGaAs) layers. The combination of InGaAs and metallic NWs shows almost 7 times higher forward current than the metallic NW with GaAs at 0.27 V with a capacitance of 0.5 fF and a series resistance of $29\ \Omega$ . The highest calculated cut-off frequency of 10.7 THz was obtained for a NW contacted vertical InGaAs diode.

In this paper, we report the fabrication and characterization of a THz Gunn source based on Gallium Nitride (GaN) with side-contact and field-plate technologies. This source works stable at operating voltages up to 20 V due to good passivation layer and good heat sink to the GaN substrate. The GaN-based Gunn diode has relatively high forward current of 0.9 A and a high current drop of about 50 mA for higher frequency and output power.

Wavelength division multiplex (WDM) passive optical network (PON) is considered for converged fixed mobile broadband access networking. We propose to utilize low-cost tunable lasers at the remote sites, together with a centralized wavelength locker. Practical implementations require a transparently added downstream signaling channel and upstream per-channel pilot tones for channel tagging and remote wavelength control. We demonstrate, for the first time, 26-Gbps discrete multitone transmission modulated on a low-cost wide tunable vertical surface emitting laser over up to 40 km of standard single-mode fiber. The results confirm that converged fixed mobile WDM-PON systems based on low-cost lasers carrying discrete multitone modulation are a technically viable approach.

We report on the results of a numerical study of quantum transport in ZnSe-based resonant-tunneling diodes (RTDs) and quantum cascade oscillators (QCOs) with fixed and unequal barrier heights. It is found that the negative differential resistance exists up to room temperature in the current–voltage characteristics of the RTD and QCO devices with unequal barrier heights. Further, we demonstrate that QCOs with unequal barrier heights have a better frequency and power performance characteristics compared with RTDs and are more beneficial for high-power terahertz generation at room temperature. For the best QCO device with 100 periods of quantum cascading, a maximum output power of ~7–9 $\mu \text{W}$ for the operating frequency range from 0.1 to ~6 THz at room temperature was achieved.

For the first time, Gunn effect is shown using a side-contact (SC) technology. Our THz Gunn source is based on 2 $\mu$ m thick gallium nitride (GaN) with stable operation up to 22 V due to better heat sink and side contact technology. A diode current of about 1 A was achieved for high output power.

In this paper we report a new terahertz (THz) Schottky detector module based on vertically contacted highly doped (1 x 1018 cm-3) indium gallium arsenide (InGaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact and a standard evaporated contact (SD). These Schottky diodes were placed on a silicon lens and integrated with a preamplifier on a printed circuit board (PCB). Furthermore, three different antennas for this detector module were investigated.

Ever growing optical data transmission networks and miniaturization of spectroscopic equipment demand for small, energy efficient and mass-produced optical components. Here we present distributed Bragg reflector (DBR) mirror based widely tunable optical Fabry-Perot filters comprising a novel material combination namely, silicon carbide (SiC) and silicon dioxide (SiO 2 ) layers with refractive indices of 2.46 and 1.45, respectively. The resulting refractive index step of 1, provides high reflectivites (>99.5%) with wide stopbands of more than 300 nm [1]. Hence, large wavelength tuning range and a narrow full width at half maximum (FWHM) filtered signals can be produced. Structuring the dielectric layers by surface micromachining creates a free standing movable mirror supported by four beams. Due to inherent stress created during low-temperature plasma enhanced chemical vapor depositions (PECVD) we obtain a tunable stable plane concave resonator. In the end the cross section of a filter shows a fixed bottom DBR deposited on a silicon substrate, a tunable airgap and an electrothermally actuated top MEMS DBR with a gold electrode for heating current I MEMS . On the substrate backside where the filtered signal is exiting an anti-reflection coating is deposited.

The effect of using graphene as 2D nanoelectrode for continuous wave (CW) terahertz (THz) photomixers were investigated. The multilayer graphene (6–8 and 3–5 MLG) sheets were used as six-finger interdigital nanoelectrodes on a low- temperature-grown (LTG) GaAs photoconductor. The MLG nanoelectrode shows unique properties with high short-circuit current capabilities and reliable high photocurrents. The number of graphene layers play a big role on the electrical and the optical properties of graphene nanoelectrode. In one hand, a thinner graphene increases the transparency of the nanoelectrodes to improve the power conversion efficiency, and on the other hand, a thicker graphene is required to carry high current densities and enhance the photomixer performance.

An ultra-wideband (UWB) doublet pulse generation technique in the optical domain for UWB-over-fiber systems is presented. Our solution is based on the direct modulation of a semiconductor laser, optical filtering, and chromatic dispersion in a transmission fiber. When the integration of the transmitter in optical access network infrastructure is considered, the transmission length difference, or the difference in accumulated dispersion, is an issue to exactly obtain the desired pulse shape. To solve this problem, we propose to adjust the transmitter operation point, specifically the laser chirp, with respect to the targeted transmission fiber length. Bit error rate measurements prove that doublet pulses can be achieved with fiber length variation from 15 to 40 km of single-mode fiber.

A new terahertz (THz) photomixer based on semi-insulating GaAs (SI-GaAs) with silver nanowire (Ag-NW) is for the first time demonstrated for continuous wave (CW) THz radiation. The use of the Ag-NW greatly enhanced the THz output power (‘” two order of magnitude) and compensated the large carrier lifetime of the SI-GaAs photoconductor.

In this paper we report a new THz Schottky detector based on vertically contacted high doped (1 × 1018cm −3) indium gallium arsenide (InGaAs) by using a small diameter (100 nm) silver nanowire (NW) as air-bridge contact. Compared to Schottky diodes based on gallium arsenide (GaAs) it has better zero-bias operation of 100 μA @ 0.05 V raising to more than 1 mA @ 0.27 V for lower noise application.

We report on numerical study of room-temperature terahertz quantum cascade lasers (THz QCLs) based on a nonpolar m-plane ZnMgO/ZnO employing a 2-well design scheme with variable barrier heights and a delta-doped injector well. We show that by varying and optimizing constituent layer widths and doping level of the injector well, high power performance of THz QCLs can be achieved at room temperature: optical gain and radiation frequency is varied from 108 cm−1@ 2.18 THz to 300 cm−1 @ 4.96 THz. These results show that among II-VI compounds the ZnMgO/ZnO material system is optimally suited for high-performance room-temperature THz QCLs.

It is necessary to reconstruct the textbooks and change some pedagogical methods in lecturing of electrodynamics… It turned out to be necessarily to elaborate the electrodynamics from fundamental principles taking into account possible magnetic effects.

In the initial stage of research on MMs emphasis was put on exploring materials that potentially lead to a biaxial anisotropic (linear dichroism) effective material response [1, 2, 3, 4, 5, 6]. Recently research was also extended toward the exploration of meta-atoms that affect off-diagonal elements of the effective material tensors (elliptical dichroism). It expands the number of observable optical phenomena, leading to, e.g., optical activity [7, 8, 9, 10, 11] bidirectional and asymmetric transmission [12, 13, 14] or chirality-induced negative refraction [15, 16, 17]. In general, investigating the geometry of the MM (the meta-atoms geometry and their arrangement) allows us to determine the form of the effective material tensors in the quasistatic limit as extensively discussed in [8]. From such considerations it is possible to conclude on the symmetry of the plasmonic eigenmodes sustained by the MAs and on the polarization of the eigenmodes allowed to propagate in the effective medium [12]. But in order to determine the actual frequency dependence of the tensor elements, more extended models are needed which start in their description of the MA properties from scratch [14].

The interaction between the small particles (meta-atoms), either dielectric or metallic, and the propagation of an optical excitation in a regular chain of such particles has been extensively investigated [1, 2, 3, 4, 5, 6]. Interest in the behavior of chains of metallic nanoparticles was driven mainly by the pursuit of subwavelength guiding structures for a new generation of the optoelectronic components in the area of communication and information processing. Nevertheless, theoretical tools for the modeling of these chains (irrespective to the nature and sizes) remain invariant: the electromagnetic excitation in the particles is supposed to be described by taking into account all possible eigenmodes [1, 3] and interactions between all particles in a chain.

New enhanced type photomixers for continuous wave (CW) terahertz (THz) generation were fabricated using 3–5 layers and 6–8 layers of graphene material. These multilayer graphene (MLG) sheets were used as 2-D nanoelectrodes on low-temperature-grown (LTG) GaAs photoconductor. The MLG nanoelectrode shows unique properties with high short-circuit current capabilities and reliable high photocurrents. Furthermore, due to the transparency of the MLG, the use of these graphene 2-D nanoelectrodes in THz photomixers allows an efficient optical power illumination for high photocurrent generation and shows a reliable CW THz emission.

An overview of the interaction of the plasmonic nanostructures and quantum systems has been presented in the introductions to Chap. 10 and this chapter. In this chapter peculiarities appearing in the description of the plane wave propagation in MMs will be underlined, and then developed using the model discussed in Chap. 10.

In this chapter, the nonlinear optical response of MMs evoked by second-order multipoles is analyzed for the split-ring resonator, although the introduced formalism can be applied to arbitrary structures.

One of the main drawbacks of plasmonic nanostructures, restricting their potential application, is the intrinsic (ohmic) losses caused by the interaction of the free electrons of the metal with thermostat (irreversible losses) and radiative losses. The more localized light is to the metal surface, the more concentrated the plasmonic field fraction is inside the metal resulting in the appearance of higher dissipative losses (Maier in Opt Express 14:1957, 2006, 1).

It is assumed that system (2.1) is strictly valid without any approximations. Actually, system (2.1) can be elaborated in the framework of the minimum action approach; nevertheless, one should remember that the minimum action principle does not give an unambiguous form of the MEs (2.1), but instead gives a set of different forms which satisfy the requirement of relativistic invariance. The “right” form can be chosen based on the evident requirement of correspondence of the results of the final system of equations to the observed physical effects.

The classical consideration of the radiative losses for a free dipole (with dynamics described by in the frame of harmonic oscillator (HO) equation) leads to a well-known extra term in the dynamic equation proportional to the third time derivative.

The problem of the relaxation dynamics of a two-level quantum system (QS) is considered in the frame of the developed in [1] approach and compared with the known and widely used math tools. The commonly accepted in publications approach appears to be questionable from the point of view of basic principles.

The most results of this chapter have been originally obtained in Chipouline et al. (Metamaterials 6:77, 2012 [1]), Miroshnichenko et al. (Nat Commun 6:8069, 2015 [2]) with new, partially previously unpublished interpretations.

Before discussing the problems of coupled dynamics of the classical and quantum objects, it is worth to make several remarks about compatibility of quantum mechanics and ME. Surprisingly, they are not compatible. Reminding, ME have been elaborated in the frame of the classical dynamics for the charges interacting with the fields.

We present an all-optical computing scheme based on normalization operations of injection-locked lasers. We show cascaded operations in cellular automaton by an all-optical Conway’s Game of Life and simulate 100 generations of gaming.

In this chapter, the influence of the short-range lateral disorder in the MAs positioning on the effective parameters of the MMs is investigated using the multipole approach. Random variation of the near field quasi-static interaction between MAs in form of double-wires is shown to be the reason for the effective permittivity and permeability changes. The obtained analytical results are compared with known experimental data.

Our goal is to elaborate a dispersion relation as a function of the particular parameters of the MAs using the general expressions obtained in chapter ( 3.61). In order to find the relations for the dipole, quadrupole, and magnetic dipole moments ( 3.57) it is necessary to express charge dynamics in the MAs as the functions of the averaged fields.

We demonstrate direct modulation of a widely tunable microelectromechanical system (MEMS) vertical-cavity surface-emitting laser (VCSEL). The wavelength tuning is realized with electrothermal actuation of a SiO $_x$ /SiN $_y$ -based MEMS distributed Bragg reflector (DBR). The DBR is deposited in a low-temperature plasma-enhanced chemical vapor deposition chamber on a InP-based half-VCSEL by means of surface micromachining. More than 60 nm of mode-hop free continuous tuning with a center wavelength of 1554 nm is achieved. A maximum 3-dB small-signal modulation response ( $S_{21}$ ) bandwidth of 7.05 GHz is reported. Quasi-error-free operation of a back-to-back link is demonstrated at 10 Gb/s for a record 47-nm tuning range, showing the compatibility of the MEMS tunable VCSEL as a cost-effective optical source in access networks and interconnects.

New types of continuous-wave (CW) terahertz (THz) photomixers were fabricated using 1-D and 2-D nanocontacts on low-temperature-grown (LTG) GaAs as well as nitrogen-ion-implanted $({\rm N}^{+}{\rm i})$ GaAs. The 1-D and 2-D nanocontacts were formed by silver nanowires and graphene sheets, respectively. A silver nanowire (Ag-NW) with a physical diameter of $\varnothing \hbox{60 nm}$ and $\varnothing \hbox{120 nm}$ can handle currents of $>\! \hbox{10}$ and $>\! \hbox{30 mA}$ , respectively, without electromigration, thus enabling reliable high photocurrents. The small diameter of such a nanowire electrode in 1-D photomixers reduces the device capacitance by a factor of more than ten compared with photomixers with conventional interdigital fingers. Thus, these nanowire properties can be used for the fabrication of photomixers with cut-off frequencies $>\hbox{2 THz}$ and with extremely reliable operation. A multilayer graphene (MLG) of 6–8 layers shows unique properties with high short-circuit current capabilities of $>\hbox{9 mA/(10}~\mu \hbox{m width})$ and reliable high photocurrents. Furthermore, the MLG absorbs only 2.3% of white light and is ideal as a transparent nanocontact. The use of these graphene electrodes in 2-D photomixers allows an efficient optical power illumination for high photocurrent generation and shows the potential for reliable CW THz emission. Initial THz measurements confirmed the high possibilities of these new nanocontact photomixers.