Arms Of Mach-Zehnder Interferometer Research Articles

Silicon photonics foundry fabricated, slow-light enhanced, low power thermal phase shifter

In this research, we developed a low-power silicon photonics foundry-fabricated slow-light thermal phase shifter (SLTPS) where the slow-light (SL) effect is achieved using an integrated Bragg grating (BG) waveguide. Heating the grating induces a red shift in the transmission spectrum, leading to an increased group index ng during operation, which facilitates a further reduction in the voltage needed for a π phase shift, i.e., Vπ. Additionally, we investigated a compact Mach–Zehnder Interferometer (MZI) that incorporates the SLTPS in both arms with a phase shifter length of 50 μm. A detailed theoretical analysis was conducted to address the non-idealities of the SL-MZI due to uneven optical power splitting and unbalanced loss in the two MZI arms. Vπ and power consumption for a π phase shift (Pπ) of the SL-MZI were quantified for operation in the slow-light regime, demonstrating a Vπ of 1.1 V and a Pπ of 3.63 mW at an operational wavelength near the photonic band edge. The figure of merit Pπ×τ is commonly used to assess the performance of thermal optical switches. The SL-MZI in this work has achieved a low Pπ×τ of 5.1 mW μs with an insertion loss of 4.4 dB, indicating a trade-off with the Vπ reduction.

Interval Adjustable Dual-Wavelength Erbium-Doped Fiber Laser Based on Cascaded Two Mach-Zehnder Interferometers

An interference filter is designed by cascading two Mach-Zehnder interferometers (MZIs), which is then utilized in the construction of a wavelength interval adjustable dual-wavelength Erbium-doped fiber laser (EDFL). Each MZI consists of two 3 dB optical couplers (OCs) connected in series. The input light is split into two arms at the first OC and recombined at the second OC. The first MZI (MZI 1) has a smaller free spectral range (FSR) and is used for selecting the output wavelength of the laser. The second MZI (MZI 2) has a larger FSR and forms an envelope structure on the comb-like spectrum of MZI 1. By adjusting the optical path difference between the two arms of MZI 2, the FSR of the envelope can be changed, thereby altering the interval of the output wavelengths. The implemented filter is inserted into the EDFL to achieve stable dual-wavelength output. By stretching one arm of MZI 2, the interval of the dual-wavelength can be adjusted from 4.64 to 13.94 nm, with the side-mode suppression ratio of over 44 dB for all wavelengths.

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.

Multimode optical switch based on cascaded Mach-Zehnder interferometer waveguides.

We present a 1 × 1 multimode optical switch for E11, E21, E12, and E22 modes based on cascaded Mach-Zehnder interferometer (MZI) waveguides, where the primary MZI is used to split E11, E21, E12, and E22 modes into E11 or E12 mode and then couple back to the original mode at the output, and the secondary MZIs are the modulation arms of the primary MZI. In addition, the secondary MZIs are designed to be mode-insensitive for switching E11 and E12 modes simultaneously. As a proof of concept, we fabricate the device with polymer material to achieve thermo-optic switching for the four modes. Our experimental device exhibits the extinction ratios of larger than 10.2 dB with a power consumption of 5.5 mW and response times of less than 1.28 ms for each mode. The presented device can be widely applied in mode-division multiplexing (MDM) systems where multimode switching is needed.

Design and simulation of a dynamically tunable 1× 2 power splitter using MZI configuration in the telecom regime

We propose an ultra-broadband, ultra-compact and a dynamically tunable power splitter on a silicon on Insulator (SOI) platform with a 220 nm thick silicon light-guiding layer, using two multimode interference (MMI) couplers connected with graphene-based waveguides as the phase-tuning section through a Mach-Zehnder Interferometer (MZI) configuration. First, we theoretically present and demonstrate a novel design for the MMI couplers by combining the plane wave expansion method (PWEM) and the mode expansion conjecture concept. To verify the proposed theory, a center-fed MMI coupler and a MMI coupler, respectively, as the input and output sections of our proposed device, are designed and simulated. The simulation results achieved by Lumerical FDTD show good agreement with the design theory. Then, a highly tunable graphene-embedded silicon waveguide, for the highly efficient modulation of the effective mod index (EMI), is duly designed using Lumerical Mode Solutions. As the two MZI arms, a pair of the proposed waveguides is introduced into the middle of the cascaded MMI couplers. Accordingly, the integration properties of the analytically designed MMI couplers and the numerically designed waveguide is demonstrated through our proposed device for the aim of achieving any wanted power splitting ratio. To this end, we consider the case that the real part of the EMI of the waveguide in the lower MZI arm is modulated by varying the graphene Fermi level values, being the same for all the layers belonging to the same waveguide, while that of the upper arm is constant. The corresponding power splitting ratio can be dynamically tuned in the range of All reported results assume TE polarization. The designed MZI-based splitter possesses a bandwidth of over the wavelength range from to for various power splitting ratios, maintaining the averaged insertion loss and the averaged power imbalance, respectively, below as low as and The overall footprint of the proposed device is also highly small, i.e., about

GeSbSeTe-based high extinction ratio optical modulator.

In this paper, a design for a high extinction ratio Mach-Zehnder optical modulator is proposed. The switchable refractive index of the germanium-antimony-selenium-tellurium (GSST) phase change material is employed to induce destructive interference between the waves passing through Mach-Zehnder interferometer (MZI) arms and to realize amplitude modulation. A novel, to the best of our knowledge, asymmetric input splitter is designed for the MZI to compensate for unwanted amplitude differences between MZI arms and increase the modulator performance. Three-dimensional finite-difference-time-domain simulations show a very high extinction ratio (ER) and low insertion loss (IL) of 45 and 2dB, respectively, for the designed modulator at the wavelength of 1550nm. Moreover, the ER is above 22dB, and the IL is below 3.5dB in the wavelength range of 1500-1600nm. The thermal excitation process of GSST is also simulated using the finite-element method, and the speed and energy consumption of the modulator are estimated.

A Mach–Zehnder Interferometer Refractive Index Sensor on a Spoof Surface Plasmon Polariton Waveguide

In this paper, we experimentally and numerically confirm a planar Mach–Zehnder interferometer (MZI) device for sensing dielectric samples based on a spoof surface plasmon polariton (SSPP) waveguide. The MZI system is constructed using two different ultrathin transmission lines with distinct dispersion units supporting SSPPs. After SSPPs propagate a certain propagation distance, a resonant dip is formed at a specific frequency due to destructive interference, whose displacement enables the SSPP to be modulated by one of the MZI arms loaded with dielectric samples. We investigate how the variations in the permittivity and thickness of dielectric samples affect the sensibility. Through an error analysis between the experimental measurements and numerical calculations, it is demonstrated that the plasmonic sensor based on the MZI has a high precision. The proposed technique is compact and robust and paves a versatile route toward the chip-scale functional devices in microwave circuits.

A compact realization of Feynman Reversible and NOR logic gate using Plasmonic waveguide based MZI for all-optical signal processing

The reversible logic function becomes a potential solution in the regime of optical switching and computing. The one-to-one mapping between inputs and outputs in a reversible gate is a key advantage, that prevents information loss. The reversible logic gates have shown potential applications in low-power complementary metal-oxide semiconductors and in quantum computing. Therefore, to utilize these benefits of reversible functions, we have proposed an all-optical compact circuit to realize the functioning of Feynman reversible and NOR logic gates. The proposed all-optical circuit is modeled within the footprints of 87μm by using a plasmonic metal–insulator–metal (MIM) waveguide-based Mach–Zehnder interferometer (MZI). The numerical investigation of the MZI is done by evaluating the power imbalance and extinction ratio. The results show that the optical signal propagating in a single MZI with an extinction ratio of 15.1 dB for the power difference of 0.001 W/μm (∼0.1 dB) and 0.0012 W/μm (∼0.79 dB) for logic ‘0’ and logic ‘1’, respectively. The logic ‘0’ and ‘1’ is represented by low (0.028 W/μm) and high (0.038 W/μm) power signals. At logic ‘0’ the optical signal propagates in linear arms of MZI with ‘π’ phase variation, which causes constructive interference (CI) and thrives the signal at the cross-port. For logic ‘1’ the optical signal experiences ‘0’ phase variation in linear arms of MZI, and due to destructive interference reaches its through-port. The investigated results of the proposed circuit are attained by using the finite difference time domain (FDTD) method.

Photonic crystal based interferometric design for label-free all-optical sensing applications.

Optical sensing devices has a great potential in both industrial and biomedical applications for the detection of biochemicals, toxic substances or hazardous gases thanks to their sustainability and high-selectivity characteristics. Among different kinds of optical sensors based on such as fibers, surface plasmons and resonators; photonic crystal (PC) based optical sensors enable the realization of more compact and highly efficient on-chip sensing platforms due to their intriguing dispersive relations. Interferometric devices based on PCs render possible the creation of biochemical sensors with high sensitivity since a slight change of sensor path length caused by the captured biochemicals could be detected at the output of the interferometer via the interferences of separated beams. In this study, a new type of Mach-Zehnder Interferometer (MZI) using low-symmetric Si PCs is proposed, which is compatible with available CMOS technology. Intended optical path difference between the two MZI channels is provided by the periodic alignments of symmetry-reduced PC unit cells in the MZI arms. Unlike the conventional symmetrical PC based MZIs, Fano resonances exist for the proposed MZI design, i.e. transmission dips and peaks appear in the output spectrum, and the location of dip and peak frequencies in transmission spectra can be efficiently controlled by utilizing interference phenomenon. Exploiting this effect, any refractive index change at the surrounding medium could be distinctly observed at the transmission spectra. In the view of such results, it is convenient to say that the proposed MZI configuration is suitable for efficient optical sensing of toxic gases as well as liquids. The designed all-dielectric MZI system is numerically investigated in both spectral and spatial domains to analyze its interferometric tunability: an optical sensitivity of about 300 nm/RIU is calculated for gaseous analytes whereas that sensitivity value is around 263.2 nm/RIU in the case of liquid analytes. Furthermore, high quality factor of Q > 45000 is obtained at Fano resonances with Figure-of-Merit (FoM) value of FoM ∼ 8950 RIU-1(7690 RIU-1) in the case of gas analytes (liquid analytes), which is the indication of enhanced optical sensing performance of the proposed MZI design. Considering all the above-mentioned advantages, the proposed interferometric configurations based on low-symmetric PCs could be utilized for efficient photonic sensor applications that require controllable output power or sensing of gaseous and liquid substances.

Mach-Zehnder interferometer comb filter for multi-wavelength mode-locked generation from erbium-doped fiber laser.

A picosecond pulse multi-wavelength erbium-doped fiber ring laser based on an optically switchable/tunable Mach-Zehnder interferometer (MZI) filter is proposed and experimentally demonstrated. The MZI configuration is constructed with two 3 dB couplers and two short pieces of endlessly single-mode photonic crystal fiber with different lengths in each arm. The combination of the MZI and a polarization controller (PC) acts as a selective comb filter and a mode-locking device. By adjusting the pump power or the first PC (PC1) state, the laser can emit up to 10 channels with a 20 nm tuning range (1530 to 1550 nm). Furthermore, by changing the PC1 condition, stable picosecond mode-locking generation with a repetition rate of 13.5 MHz is realized. To achieve wavelength spacing tunable multiple-channel laser emissions, the MZI is configured by incorporating a second PC (PC2) in one arm of the conventional MZI. Four channels of picosecond mode-locking pulses with a repetition rate of 11.6 MHz in the range of 1530-1550 nm are realized by carefully controlling the pump power and/or PC2 state. With the manipulation of intracavity birefringence through PCs with comb filtering via MZI, the proposed structure may be a potential tool in various photonics applications.

Tunable filter based on two concatenated symmetrical long period fiber gratings as Mach-Zehnder interferometer and its fiber lasing application

This work presents a highly stable switchable and tunable erbium-doped fiber laser based on a Mach-Zehnder interferometer (MZI) made with two symmetrical LPFGs separated by an SMF segment of 5 cm in length. The core and the cladding of the SMF central segment act like the MZI arms, whereas the LPFG1-SMF and SMF-LPFG2 splices act as optical couplers. The emission is switchable from one single emission at 1563.6 nm, a side mode suppression ratio (SMSR) of ∼55 dB, and linewidth of 0.15 nm, to a dual emission located at 1563.98 and 1573.89 nm, reaching a high SMSRs of 56 dB, and linewidths ∼0.10 nm. Moreover, the laser emission can be tuned from 1569 to 1572 nm applying torsion to the MZI from 0° to 330° obtaining a nearly linear sensitivity of 9.2 pm/° with low hysteresis. Additionally, the laser operation stability was tested over 60 min, obtaining the power and wavelength fluctuations lower than 0.086 dB and 0.028 nm respectively. To the best of our knowledge, this is the first time that symmetric LPFGs have been used as a torsion sensitive WSF. For its high wavelength stability and SMSR, the MZI can be a low-cost alternative WSF while the switchable and tunable laser can be useful as an optical source for spectroscopy and communications applications.

Performance of microheaters for tunable on-chip interferometer

Mach-Zehnder interferometer (MZI) is a valuable practical tool in many optical science areas. In particular, high-contrast MZI are required for experimental realization of displacement-based quantum receivers that can discriminate weak coherent states of light with the minimum error rate. In this work we study phase modulators of tunable on-chip interferometer on silicon nitride (Si3N4) platform for telecom wavelength (1550 nm) consisting of several MZI. Phase modulators on one of the arms of MZI consists of microheaters and waveguide. Microheaters heat waveguides changing its refractive index due to thermo-optical effect providing a phase shift. We measure the bandwidth of phase modulators and study their operation in pulse mode.

Reconfigurable Mach–Zehnder interferometer for dynamic modulations of spoof surface plasmon polaritons

Abstract We propose an ultrathin reconfigurable Mach–Zehnder interferometer (MZI) for realizing dynamic frequency and amplitude modulations of spoof surface plasmon (SSP) signal. Active varactor diodes are integrated in the SSP unit cells on one of the MZI arms to introduce asymmetry to the MZI structure, which can control the interference patterns by varying bias voltages applied on the varactor diodes. We show that the spectral positions of multiple sharp interference dips are very sensitive to the change of diode capacitance, thereby allowing for good frequency modulation. We also demonstrate continuous amplitude modulation by tuning the varactor diodes at multiple selected frequencies. To verify the reconfigurable feature of the proposed SSP MZI, the frequency shift keying (FSK) and amplitude modulations have been experimentally demonstrated on the same structure. The modulation depth of the amplitude modulation can be further improved by designing geometrical parameters of the SSP structure, reaching a significant amplitude change from 0.88 to 0.05 in experiments.

High-Q-Factor Tunable Silica-Based Microring Resonators

A high-Q-factor tunable silica-based microring resonator (MRR) is demonstrated. To meet the critical-coupling condition, a Mach–Zehnder interferometer (MZI) as the tunable coupler was integrated with a racetrack resonator. Then, 40 mW electronic power was applied on the microheater on the arm of MZI, and a maximal notch depth of about 13.84 dB and a loaded Q factor of 4.47 × 106 were obtained. The proposed MRR shows great potential in practical application for optical communications and integrated optics.

Passive amplitude-phase modulations and sensing based on Mach–Zehnder interferometer of spoof surface plasmon polaritons

We numerically and experimentally demonstrate an ultrathin and compact Mach–Zehnder interferometer (MZI) for sensing and amplitude/phase modulations of spoof surface plasmon polariton (SSPP) waves. For a specific frequency, the magnitude and phase of the far-field transmission are modulated when a dielectric sample is loaded on one of the MZI arms. The phase difference between the SSPP waves propagating along the sensing and reference arms causes the outputs from both arms to interfere, allowing small perturbations in the sensing arm to be detected. Our study shows that the sensitivity of the proposed SSPP MZI is significantly higher than that of the single-armed SSPP waveguide, and also better than that of the conventional MZI formed with the traditional microstrip lines. The dependence of the sensitivity on the structural parameters such as geometrical parameters of the detected material and the arm length of MZI is discussed, revealing the possibility of realizing miniaturized MZI with high sensitivity.

Power-Efficient O-Band 40 Gbit/s PAM4 Transmitter Based on Dual-Drive Cascaded Carrier-Depletion and Carrier-Injection Silicon Mach-Zehnder Modulator With Binary Driving Electronics at CMOS Voltages

We present an O-band four-level pulse amplitude modulation (PAM4) transmitter based on a dual-drive silicon modulator with binary driving electronics at CMOS voltages, effectively eliminating the need for power-hungry digital-to-analog converters (DACs) and RF drivers. The fabricated dual-drive silicon modulator has cascaded p - n junction and p - i - n junction embedded in each arm of Mach-Zehnder interferometer, implementing high-speed data modulation and efficient bias control, respectively. Power dissipation of around 611 fJ/bit is obtained when synthesizing 46 Gb/s PAM4, showing high power efficiency. The fabricated silicon modulator exhibits a π-voltage-length product of 4.5 V·mm, and a 3-dB bandwidth of up to 27 GHz. Meanwhile, to implement a power-efficient PAM4 transceiver, the digital signal processing (DSP) at the receiver side is also discussed by balancing the performance and complexity. With a low-complexity DSP, negligible power penalty is observed after transmission over 38-km SSMF for both synthesized 20 Gb/s and 40 Gb/s PAM4. The presented PAM4 transmitter takes the advantages of both carrier-depletion and carrier-injection phase shifters for effective data modulation and bias control in PAM4 signalingand provides a power-efficient transmitter solution by eliminating the use of power-hungry DACs or RF drivers for datacenter interconnects.

A low-finesse all-fiber sinusoidal phase modulation interferometer for displacement measurement

We present an all-fiber sinusoidal phase modulation (SPM) interferometer for displacement measurement based on an in-built electro-optical modulator (EOM). The interferometer consists of a fiber-optical Mach–Zehnder interferometer (MZI) and a low-finesse fiber-optic Fabry–Pérot interferometer (FPI) through a circulator. The EOM is combined in one arm of MZI for generating modulating reference beam. Reflected beams from an object and the end of the fiber interfere with the reference beam. The phase differences between the reflected beam from the object and the modulated reference beam are demodulated using an improved phase generated carrier demodulation algorithm which is realized on a field-programmable gate array. Compared with the conventional fiber-optic Fabry–Pérot interferometer, this SPM interferometer effectively expands the working distance. Furthermore, we also demonstrate the effect of the phase difference between the fiber end and the reference arm on the measurement. The displacement can only be extracted correctly when the phase difference deviation between the fiber end and the reference arm is smaller than +/−0.29 rad. The experiment results show that the measurement range of the presented interferometer is up to 20 mm with a nonlinear error of ±53.4 nm. The interferometer has a displacement resolution of 45 pm∕Hz over 20 Hz.

A Microscale Numerical Analysis of Ex-OR and Ex-NOR Logic Gates by Using Single Plasmonic MZI

This work is focused on a detailed mathematical and numerical simulation–based analysis of Ex-OR and Ex-NOR logic gates at microscale by employing metal-insulator-metal (MIM) plasmonic waveguide–based Mach-Zehnder interferometer (MZI). The geometry of MIM waveguide is designed by considering the air as dielectric material in between silver metallic layers. The bulk plasma frequency and damping constant of silver metallic layers are considered as ωp = 140 × 1014 rad/s and $${\varvec{\gamma}}=$$ 0.4 × 1014 rad/s, respectively. A nonlinear Kerr-material with response in the order of picosecond is employed in linear arms of MZI to switch the phase of optical signals. The design of single MZI is modelled within the footprints of 19 × 3 µm with a high extinction ratio (ER) of 29 dB. The phase change property of MZI is utilized to validate the operation of Ex-OR and Ex-NOR gates. The results suggest that the proposed plasmonic-based logic gates can pave the path for efficient all optical signal processing system.

Numerical simulation of all-optical logic functions at micrometer scale by using plasmonic Metal-Insulator-Metal (MIM) waveguides

All-optical integrated circuits are quite useful in the regime of ultrafast computing to overcome the limitations of existing electronic components. In this work, we have modelled two different all-optical integrated circuits to validate the operations of OR, AND, NOR, XOR, XNOR logic gates and half-adder circuit. To cascade the integrated circuits, a plasmonic metal–insulator-metal (MIM) waveguide based Mach-Zehnder interferometer (MZI) has been used. The signal switching is attained by using MEH-PPV [poly(2-methoxy-5-(28-ethylhexyloxy)-PPV)] as nonlinear Kerr material in one linear arm of MZI. The relative linear permittivity, response time and RI of nonlinear Kerr material are 2.7225, 2.0 e−15 s, and 1.67, respectively. The switching of signal across the output ports of MZI depends on the principle of self-phase and cross-phase modulation, which depends on the power of input signals. Signal power of 0.326 W/µm and 0.828 W/µm is used for low and high intensity which corresponds to logic level ‘0′ and ‘1′, respectively. The projected integrated circuits are analyzed at the wavelength of 1550 nm with transverse magnetic (TM) polarization under the contour of perfect matched layer (PML) as boundary conditions. The results conclude that the extinction ratio (ER) of single MZI is gradually decreasing with respect to the increase in power difference. For proposed design of single MZI the attained value of ER is 24 dB at the power difference of 0.3 dB. The authentication of proposed integrated circuits is done by using finite difference time domain (FDTD) based method.

Design Rule of Mach-Zehnder Interferometer Sensors for Ultra-High Sensitivity.

A design rule for a Mach-Zehnder interferometer (MZI) sensor is presented, allowing tunable sensitivity by appropriately choosing the MZI arm lengths according to the formula given in this paper. The present MZI sensor designed by this method can achieve an ultra-high sensitivity, which is much higher than any other traditional MZI sensors. An example is given with silicon-on-insulator (SOI) nanowires and the device sensitivity is as high as 106 nm/refractive-index -unit (or even higher), by choosing the MZI arms appropriately. This makes it possible for one to realize a low-cost optical sensing system with a detection limit as high as 10−6 refractive-index-unit, even when a cheap optical spectrum analyzer with low-resolution (e.g., 1 nm) is used for the wavelength-shift measurement.