Nonlinear Mach-Zehnder Interferometer Research Articles

A gateway to synthesis of all-optical devices of desired functionalities

I propose combining of all-optical devices to produce an all-optical device that exhibits a desired input–output (I/O) characteristic (i.e., a desired functionality). There could be infinite distinct combinations of same/different all-optical devices of same/different parameters resulting in possibility of infinite number of all-optical devices with distinct I/O characteristics, and hence, the proposal presented here opens-up a gateway to synthesis of all-optical devices of desired functionalities. To give a few of examples in support of the proposal, I show certain series and parallel combinations of nonlinear Mach-Zehnder interferometers (NMZIs) to synthesize an (i) ideal optical switch (with step like I/O characteristic), (ii) optical isolator/optical stabilizer (iii) optical pulse generator (iv) optical power filter and (v) optical limiter. The analytical findings are verified using BPM simulations in presence of losses also.

Flexible All-Optical 8QAM Signal Format Conversion Using Pump Assisted Nonlinear Optical Loop Mirror

A flexible all-optical format interconversion scheme based on a pump assisted nonlinear optical loop mirror (NOLM) is proposed and numerically simulated for the first time to our knowledge. In this scheme, input multi-Gbps 8QAM signals are divided into clockwise (CW) and counter-clockwise (CCW) components by a 3-dB optical coupler (OC), which also couples light from the input pump into the NOLM from the CCW direction. The numerical model of the pump assisted NOLM with CW and CCW optical paths is simplified using a nonlinear Mach-Zehnder interferometer (MZI). Optical signals in the upper MZI arm will be mainly affected by the self-phase modulation (SPM) effect when traversing the highly nonlinear fiber (HNLF) and those in the lower MZI arm are impacted by cross-phase modulation (XPM) in addition to SPM when they experience the HNLF with the input pump light. When the upper-arm optical signal with SPM phase shift and the lower arm optical signal with SPM and XPM phase shifts are coherently mixed, a new converted 8QAM signal can be obtained. The power transfer function (PTF) of the pump assisted NOLM and the relative phase shift (RPS) between the input and the output optical signals are theoretically provided and verified. By only changing the input power of the 8QAM signal and the pump light, all-optical format interconversion of square-, standard- and star-shaped 8QAM signals can be achieved. Furthermore, the proposed scheme can achieve format conversion from the 30 Gbps square-shaped 8QAM signal to a 20 Gbps quadrature phase shift keying (QPSK) signal. The scheme performance is analyzed via constellation diagrams, eye diagrams, the error vector magnitude (EVM) and the bit error rate (BER) of the optical signals. The scheme developed can be deployed in optical gateways to connect different optical networks by dynamically selecting their appropriate modulation formats.

Engineering superpositions of N00N states using an asymmetric non-linear Mach–Zehnder interferometer

We revisit a method for mapping arbitrary single-mode pure states into superpositions of N00N states using an asymmetric non-linear Mach–Zehnder interferometer (ANLMZI). This method would allow one to tailor-make superpositions of N00N states where each axis of the two-mode joint-photon number distribution is weighted by the statistics of any single-mode pure state. The non-linearity of the ANLMZI comes in the form of a χ(3) self-Kerr interaction occurring on one of the intermediary modes of the interferometer. Motivated by the non-classical interference effects that occur at a beam splitter, we introduce inverse-engineering techniques aimed toward extrapolating optimal transformations for generating N00N state superpositions. These techniques are general enough so as to be employed to probe the means of generating states of any desired quantum properties.

All-Optical Regeneration and Format Conversion for 4APSK Signals Based on Nonlinear Effects in HNLF

An all-optical format conversion and regeneration scheme about 4-ary amplitude and phase shift keying (4APSK) signals is proposed and numerically simulated based on nonlinear effects in the high nonlinear fiber (HNLF). The input 4APSK signal is firstly converted into a regular quadrature phase shift keying (QPSK) signal by the nonlinear Mach-Zehnder interferometer (MZI) based on the self-phase modulation (SPM). Secondly, a degenerate phase-sensitive amplification (PSA) based on the four-wave mixing (FWM) is utilized to convert the regular-QPSK into two binary phase shift keying (BPSK) signals. The nonlinear MZI configuration is also used to compress the amplitude noise of BPSK. Thirdly, one phase shifter and one variable optical attenuator (VOA) are used to adjust the relative phase and power relationships of the two amplitude-regenerated BPSK signals. The regenerated 4APSK and converted QPSK signals can be generated in one 3-dB optical coupler through coherent addition of the two regenerated BPSK signals. The error-vector-magnitude (EVM) and the bit-error-rate (BER) are calculated and compared to evaluate the scheme performance. The proposed scheme can be applied as an optical regenerator or format convertor at the network gateway to increase the transmission distance or connect optical networks with different modulation formats.

All-Optical Format Conversion of 2-Dimensional MQAM to MPSK Based on Nonlinear Mach-Zehnder Interferometer With Wavelength Preservation

An all-optical format conversion scheme of 2-dimensional multiple-quadrature amplitude modulation (MQAM) to multiple-phase shift keying (MPSK) signals is proposed and numerically simulated by using the nonlinear Mach-Zehnder interferometer (MZI) configuration with wavelength preservation. The input octal-quadrature amplitude modulation (8QAM) signal is generated through the phase modulator (PM) and amplitude modulator (AM) and injected into the nonlinear MZI configuration. The designed nonlinear MZI configuration includes two 3 dB optical couplers (OCs), a piece of high nonlinear fiber (HNLF) and a variable optical attenuator (VOA) in the upper interfering arm and a piece of standard single mode fiber (SSMF) or tunable optical delay line (TODL) and a variable phase shifter (VPS) in the lower interfering arm. The converted octal-phase shift keying (8PSK) signal can be obtained from the nonlinear MZI configuration through vector superposition between the input optical signal and itself with some nonlinear phase shift. The needed asymmetric nonlinear phase shift is mainly induced by the big nonlinear index difference between HNLF and SSMF. The error vector magnitude (EVM) and bit error rate (BER) performance of the scheme are calculated before and after format conversion with the different input and receiver optical-signal-noise-ratios (OSNRs). The scheme can be used in the intermediate node to connect the different networks which adopt 8QAM and 8PSK signals, respectively.

Nonlinear Mach-Zehnder interferometer isolator.

Isolators are important devices in optics, especially for low noise systems, as even a small amount of back reflection can be detrimental to the quality of the signal generated by the source impacting downstream applications. Traditionally, magneto-optical materials have been used in isolators for bulk and fiber based optical systems. However, they tend to have high insertion loss, and are complicated to integrate on a photonics chip. Another class of isolators is based on optical nonlinearity that do not require external magnetic bias. However, the devices demonstrated so far suffer from either limited bandwidth, high insertion loss or fabrication complexity. In this work, we demonstrate a monolithic, fully complementary metal-oxide-semiconductor compatible, nonlinear Mach-Zehnder interferometer isolator based on third order optical nonlinearity, that overcomes such issues. In this proof of principle study, we show up to 15 dB isolation with 0.4 dB insertion loss and a device footprint of 0.4 mm2 which can easily be improved on further. The device is broadband and is independent of wavelength, material, and the platform. Not only can such a device be used for integrated optical systems but also for the fibre based optical systems.

Simultaneous Enhancement of Contrast and Power of Femtosecond Laser Pulses by Nonlinear Interferometer

We showed that the nonlinear Mach–Zehnder interferometer may be used not only for enhancing temporal contrast, as proposed earlier, but also for increasing pulse power due to efficient pulse compression. The interferometer introduces into the output pulse a nonlinear phase equal to π/2. This allows increasing laser power by a factor of 1.5 only by means of a chirped mirror. Use of an additional nonlinear plate leads to a multi-fold power increase retaining the contrast enhancement.

Optical half and full adders using the nonlinear Mach–Zehnder interferometer

Digital circuit is designed with logic gates. Utilizing these common logic gates, one can carry out completely different arithmetic and logic functions. All-optical arithmetic and logic functions are a great deal in anticipation in elevated pace conversation systems. In this paper, we have proposed 2-bit (half adder) and 3-bit (full adder) data processing circuits utilizing nonlinear Mach–Zehnder interferometer (NMZI) switch. Via numerical simulations, these data processing circuits are studied theoretically and checked.

Integrable all-optical switch for photonic integrated circuits

A completely new model of an all-optical switch (AOS) is proposed using a silicon photonic crystal (PhC) slab based nonlinear Mach–Zehnder interferometer (NMZI). Both arms of the NMZI are designed using p-toluene sulfonate (PTS) based slotted PhC waveguides (PTS-SPCWs). Extreme optical confinement in SPCW is used here to intensify optical nonlinearities of PTS. The intensified nonlinearity produces significant phase changes in optical pulses within a small waveguide length, even when the optical power is sufficiently small. One arm of the NMZI is coupled with a control wave to incur additional phase shift compared to the other due to cross-phase modulation, in addition to self-phase modulation, which is a common phenomenon for both. The differential phase shift originates destructive/constructive interference, leading to a successful switching operation of the AOS. Switching characteristics of the AOS are evaluated for a variety of parameters. A typical example shows that the AOS can switch off 12.55 mW probe power with an extinction ratio of ≈ 50.5 d B by applying 5.65 mW control power, while the device footprint is merely 259 µ m 2 . The low-power and high-speed operation makes this small footprint AOS device suitable for applications in photonic integrated circuits.

Integrable all-optical NOT gate using nonlinear photonic crystal MZI for photonic integrated circuit

A silicon photonic crystal (PhC)-based nonlinear Mach–Zehnder interferometer (NMZI) is used to design a new model for an all-optical NOT gate. The nonlinear arm of the NMZI is considered to be made of a slotted-PhC waveguide, where the slot is filled with silicon nanocrystal ( S i N C / S i O 2 ) material. The high nonlinearity of the S i N C / S i O 2 and low group velocity of the PhC make it possible to attain a significant phase shift in low-power high-frequency pulses traveling through the nonlinear arm. A control wave is utilized to increase the phase shift by the cross-phase modulation phenomenon. A complete study on the phase variation is performed by varying various parameters such as powers and pulse widths of the probe and control signal. The study is used to determine the length of the nonlinear arm to calculate the transfer characteristic of the device. The transfer characteristic shows a successful inversion operation in the power range of 28–60 mW for a pulse width of 3 ps. The overall dimension of the device is found as ≈ 112 × 7 µ m 2 . Tolerances of the device performance under fabrication imperfections are analyzed by allowing random variations in the positions and the radii of the holes. This study reveals that the inversion characteristic is sustained, even for the significant fabrication imperfections.

Nonlinear Mach–Zehnder interferometer with ultrabroadband squeezed light

We study both theoretically and experimentally the interference pattern in a nonlinear Mach–Zehnder interferometer formed by two aperiodically-poled crystals, where broadband squeezed light is generated by both crystals via parametric down-conversion with a common quasi-monochromatic pump. This configuration is important for measuring the squeezing produced by the first crystal and also for measuring a small phase shift introduced by a sample between the crystals. On the basis of the approximate quantum Rosenbluth formula for each crystal we develop an analytic model for the field evolution in the interferometer. We report an experimental observation of the interference fringes, caused by the dispersion of the generated PDC waves in both crystals forming the interferometer. We observe a displacement of the interference pattern caused by a sample between the crystals and infer the phase shift within a band of 20 nm. The experimental data are in a good agreement with the predictions of the developed model, up to imperfections of the samples.

Parameter Estimation of Wormholes beyond the Heisenberg Limit

We propose to exploit the quantum properties of nonlinear media to estimate the parameters of massless wormholes. The spacetime curvature produces a change in length with respect to Minkowski spacetime that can be estimated in principle with an interferometer. We use quantum metrology techniques to show that the sensitivity is improved with nonlinear media and propose a nonlinear Mach–Zehnder interferometer to estimate the parameters of massless wormholes that scales beyond the Heisenberg limit.

All-optical bit magnitude comparator device using metal–insulator–metal plasmonic waveguide

A plasmonic metal–insulator–metal (MIM) waveguide has great success in confining the surface plasmon up to a deep subwavelength scale. The structure of a nonlinear Mach–Zehnder interferometer (MZI) using a plasmonic MIM waveguide has been analyzed. A one-bit magnitude comparator has been designed using an MZI and two linear control waveguides. The device works on the Kerr effect inside the plasmonics waveguide. The mathematical description of the device is explained. The simulation of the device is done using MATLAB® and the finite-difference time-domain (FDTD) method.

Amplifier action of a nonlinear Mach–Zehnder interferometer by using of saturable nonlinear arm

Nonlinear Mach–Zehnder interferometer is one of important components in integrated optical circuits. This paper displays amplification of one beam by the other in a saturable nonlinear Mach–Zehnder interferometer, having two input ports and one output port. In this paper, we import two input beam, one as control beam and the other one as input beam, we could amplify the input beam by means of control beam. We carried out the simulations and numerical calculation by using of beam propagation method.

Design of Full-Adder and Full-Subtractor Using Metal-Insulator-Metal Plasmonic Waveguides

The metal-insulator-metal (MIM) waveguides are considered best among all plasmonic waveguides for propagation of optical signal to deep sub-wavelength scale. In this paper, MIM plasmonic waveguides based Mach-Zehnder interferometer (MZI) is developed. It possesses nonlinear Kerr material in one of its linear arm for controlling of optical signal with light intensity. Self phase modulation (SPM) and cross phase modulation (XPM) processes inside nonlinear MZI are used to design novel and compact full-adder and full-subtractor. Analysis and verification of proposed devices are carried out using FDTD and MATLAB simulations.

Filtration and extraction of quantum states from classical inputs

We propose using nonlinear Mach-Zehnder interferometer (NMZI) to efficiently prepare photonic quantum states from a classical input. We first analytically investigate the simple NMZI that can filtrate single photon state from weak coherent state by preferrentially blocking two-photon component. As a generalization, we show that the cascaded NMZI can deterministically extract arbitrary quantum state from a strong coherent state. Finally, we numerically demonstrate that the cascaded NMZI can be very efficient in both the input power and the level of cascade. The protocol of quantum state preparation with NMZI can be extended to various systems of bosonic modes.

All-optical NOT and AND gates using counter propagating beams in nonlinear Mach–Zehnder interferometer made of photonic crystal waveguides

Counter propagating beams (inputs) through nonlinear Mach–Zehnder interferometer (NMZI) with Kerr type nonlinearity and made of photonic crystal waveguides (PCW) are simulated using two dimensional finite difference time domain (FDTD) method. It is shown that PCW based NMZI of proper parameters could be used as NOT and AND logic gates. The results obtained here are compared with earlier published results of NMZI made of conventional step index waveguides (SIW). Operating powers and/or device length would be much smaller in case of PCW based NMZI as compared to SIW based NMZI if same nonlinear material is used.

A DSP-Based Control Method For a Nonlinear Mach–Zehnder Interferometer DPSK Regenerator

A frequency offset and phase control method is described for a differential-phase-shift-keying (DPSK) 2R (reamplification and reshaping) regenerator based on a nonlinear Mach–Zehnder interferometer. The controller is comprised of a coherent receiver, analog-to-digital converters (ADCs), a digital signal processor, and an optical frequency/phase shifter. For a 40 Gb/s DPSK signal, simulation results demonstrate that an ADC sampling rate of only 335.94 MSa/s is needed to adequately estimate the frequency offset and phase noise, and adjust the pump signal accordingly. The cascadability of the 2R regenerator is evaluated in recirculating loop simulations for different regenerator spacings, using both ideal DPSK signals and captured experimental DPSK signals. The influence of residual span dispersion on the performance is investigated.

ALL-OPTICAL LOGIC GATES BASED ON SPATIAL-SOLITON INTERACTIONS IN OPTICAL COMMUNICATION SPECTRAL REGION

New designs of all-optical logic gates based on spatial-soliton interactions in optical communication spectral regions were proposed. The proposed structures are composed of local nonlinear Mach-Zehnder interferometer (MZI) waveguide structures with multi-input ports and two nonlinear output ports. They can be used to design various all-optical logic gates. The nonlinear MZI waveguide structure with local nonlinear waveguides functions like a phase shifter. It employs angular deflection of spatial solitons controlled by the phase modulation created in the local nonlinear MZI. The light-induced index changes in the local nonlinear MZI waveguide structures break the symmetry of structure and make the output signal beam propagate through different nonlinear output waveguides. By properly choosing the input control power, the spatial solitons will be switched to different output ports. The numerical results show that the proposed local nonlinear MZI waveguide structures could really function as all-optical logic gates in the optical communication spectral region.

Switching behaviour of nonlinear Mach–Zehnder interferometer based on photonic crystal geometry

Nonlinear Mach–Zehnder interferometer (NMZI) created with photonic crystal waveguides (PCW) and with Kerr-type nonlinearity has been investigated in this paper. The NMZI has been simulated using two-dimensional finite difference time domain (2D-FDTD) method. Input verses output (I /O) characteristics have been obtained for different lengths of the nonlinear arm, nonlinear coefficients of the nonlinear arm, wavelengths of the input beam, sizes of defect rods and NMZI offset. The results obtained are compared with earlier published results of NMZI created with conventional step index waveguides (SIW). It is shown that all useful features of light switching offered by SIW-based NMZIs are also possible with PCW-based NMZIs of extremely small dimensions. Moreover, PCW-based NMZIs offer additional useful feature not available with SIW-based NMZIs.