Mach-Zehnder Research Articles

Quantum interference of pulsed time-bin entanglement generated from silicon ring resonator

We demonstrate a pulsed operation of an entangled photon pair source that is based on a silicon ring resonator. Time-bin entangled photon pairs at telecommunication wavelengths are generated via spontaneous four-wave mixing, which is excited by a pulsed pump laser. The entanglement between the generated photon pair is analyzed by using asymmetric Mach–Zehnder interferometers followed by single-photon detectors, resulting in non-classical interference with a visibility exceeding a classical limit. The reason for the degradation of the interference visibility is discussed using the theoretical model with experimental parameters. Our experimental results show successful pulsed generation of entanglement, which represents an important step towards a synchronized quantum network based on silicon photonics.

Dispersive effects in ultrafast nonlinear phenomena: The case of optical Kerr effect

It is a basic principle that an effect cannot come before the cause. Dispersive relations that follow from this fundamental fact have proven to be an indispensable tool in physics and engineering. They are most powerful in the domain of linear response where they are known as Kramers-Kronig relations. However, when it comes to nonlinear phenomena the implications of causality are much less explored, apart from several notable exceptions. Here in this paper we demonstrate how to apply the dispersive formalism to analyze the ultrafast nonlinear response in the context of the paradigmatic nonlinear Kerr effect. We find that the requirement of causality introduces a noticeable effect even under assumption that Kerr effect is mediated by quasi-instantaneous off-resonant electronic hyperpolarizability. We confirm this by experimentally measuring the time-resolved Kerr dynamics in GaAs by means of a hybrid pump-probe Mach-Zehnder interferometer and demonstrate the presence of an intrinsic lagging between amplitude and phase responses as predicted by dispersive analysis. Our results describe a general property of the time-resolved nonlinear processes thereby highlighting the importance of accounting for dispersive effects in the nonlinear optical processes involving ultrashort pulses. Published by the American Physical Society 2024

On the Time-Dilation Paradox—Can it be Removed?

In special relativity theory, the velocity of light is assumed to be constant, independent of the reference frame. This creates paradoxes when observations in different reference frames are compared. The so-called twin-paradox is based on a Gedanken experiment with identical twins, one traveling in a spaceship and one remaining on Earth. Due to the time-dilation effect, the traveling twin, when returning to Earth is younger than the other twin. This paradox has been tentatively resolved by inserting asymmetry, but the fully symmetrical twin-paradox remains within the relativity theory. However, if the light velocity, instead of being absolute, is taken to be relative, the paradox can be resolved. By reevaluating the light-clock experiment and performing various other Gedanken experiments, it becomes apparent that constant movement, independent of velocity, is the same as “at rest” for any one reference frame and does not need to involve any relativistic effects. This would make the Lorentz–Voigt factor void, and red- and blue-shifts of electromagnetic (EM) radiation can be explained as true changes in light-velocities. Based on thinking experiments, new rules for light-velocities are proposed, which also could explain anomalous observations regarding Jupiter’s moon Io’s movement. Gravity and its effect on light are examined, and it is argued that planetary lensing of light can be simply explained as refraction in a planet’s atmosphere or by diffraction on the planet itself. Further, the light pressure can resolve the indistinguishability principle. Alternatives to relativity explanations are suggested for several observations that nullify Fresnel dragging and oppose the existence of an aether medium. A modified Mach–Zehnder interferometer is proposed as an instrument for measuring sub-c and super-c velocities of EM-waves. The “old” relativity theories are replaced by a novel postulate that an applied force, leading to changes in velocity, is the reason for time-dilation: what may be called mechanical relativity. A mathematical suggestion of mechanical relativity is presented, along with discussions on connections between time, energy, and gravity.

All-optical modulation of Fano-like resonances in apodized fiber Bragg grating using Er/Yb doped fiber

A novel all-optical scheme for fast modulation of Fano-like resonance using Er/Yb doped fiber (EYDF) is proposed and demonstrated experimentally. In the integrated system, an apodized fiber Bragg grating (AFBG) is inserted into one arm of the fiber Mach–Zehnder interferometer (MZI), and the asymmetric Fano-like resonances is generated by the interference between the MZI mode and AFBG mode. In addition, a section of EYDF is inserted into the other arm of the MZI to control the phase difference between the two arms of the MZI. By adjusting the power of optical pump applied to the EYDF, the transmission spectrum lineshapes of the integrated device can be effectively modulated into asymmetric Fano-like resonances, symmetric transmission dip or electromagnetically induced transparency-like resonances, which has a fast response speed. The proposed all-optical Fano-like modulation scheme is simple in structure, and has advantages of remote control and long-term stability, providing potential applications in the fields of fast and slow light, optical filters and fiber sensing.

Ultracompact silicon on-chip polarization controller

On-chip polarization controllers are extremely important for various optical systems. In this paper, a compact and robust silicon-based on-chip polarization controller is proposed and demonstrated by integrating a special polarization converter and phase shifters. The special polarization converter consists of a 1×1 Mach–Zehnder interferometer with two polarization-dependent mode converters at the input/output ends. When light with an arbitrary state of polarization (SOP) is launched into the chip, the TE0 and TM0 modes are simultaneously excited. The polarization extinction ratio (PER) and the phase difference for the TE0/TM0 modes are tuned by controlling the first phase shifter, the polarization converter, and the second phase shifter. As a result, one can reconstruct the light SOP at the output port. The fabricated polarization controller, as compact as ∼150 μm×700 μm, exhibits an excess loss of less than 1 dB and a record PER range of >54 dB for arbitrary input light beams in the wavelength range of 1530–1620 nm.

Label-Free DNA Hybridization Detection Using a Highly Sensitive Fiber Microcavity Biosensor.

A novel label-free optical fiber biosensor, based on a microcavity fiber Mach-Zehnder interferometer, was developed and practically demonstrated for DNA detection. The biosensor was fabricated using offset splicing standard communication single-mode fibers (SMFs). The light path of the sensor was influenced by the liquid sample in the offset open cavity. In the experiment, a high sensitivity of -17,905 nm/RIU was achieved in the refractive index (RI) measurement. On this basis, the probe DNA (pDNA) was immobilized onto the sensor's surface using APTES, enabling real-time monitoring of captured complementary DNA (cDNA) samples. The experimental results demonstrate that the biosensor exhibited a high sensitivity of 0.32 nm/fM and a limit of detection of 48.9 aM. Meanwhile, the sensor has highly repeatable and specific performance. This work reports an easy-to-manufacture, ultrasensitive, and label-free DNA biosensor, which has significant potential applications in medical diagnostics, bioengineering, gene identification, environmental science, and other biological fields.

Reconfigurable all-optical pattern recognition for PSK and QAM signals in high-speed optoelectronic firewalls.

In the fifth generation fixed networks (F5G) era, full-fiber-connected optical networks support emerging bandwidth-hungry services. However, optical networks are vulnerable to attack by tapping or other methods, which has been paid more and more attention in modern optical infrastructure. Therefore, high-speed optoelectronic firewalls appear as one of the promising technologies to guarantee security. The most significant and challenging component of a high-speed optoelectronic firewall is all-optical pattern recognition, especially for more advanced high-order modulation formats such as phase shift keying (PSK) or quadrature amplitude modulation (QAM) to satisfy efficient enhanced fixed broadband in F5G. In this paper, what we believe to be a novel reconfigurable all-optical pattern recognition system for PSK and QAM signals is proposed with two implementation architectures. The proposed system mainly consists of a generalized XNOR (GXNOR) and a recirculating loop. The two implementation architectures are precisely two realization methods of the GXNOR part. One employs two cascaded IQ Mach-Zehnder modulators and the other is implemented by the four-wave mixing. The numerical simulation results demonstrate that the two implementation architectures can both achieve all-optical pattern recognition for the reconfigurable high-order modulation formats of QPSK, 8PSK, and 16QAM with the recorded baud rate of 260GBaud.

Scan-less microscopy based on acousto-optic encoded illumination.

Several optical microscopy methods are now available for characterizing scientific and industrial processes at sub-micron resolution. However, they are often ill-suited for imaging rapid events. Limited by the trade-off between camera frame-rate and sensitivity, or the need for mechanical scanning, current microscopes are optimized for imaging at hundreds of frames-per-second (fps), well-below what is needed in processes such as neuronal signaling or moving parts in manufacturing lines. Here, we present a scan-less technology that allows sub-micrometric imaging at thousands of fps. It is based on combining a single-pixel camera with parallelized encoded illumination. We use two acousto-optic deflectors (AODs) placed in a Mach-Zehnder interferometer and drive them simultaneously with multiple and unique acoustic frequencies. As a result, orthogonal light stripes are obtained that interfere with the sample plane, forming a two-dimensional array of flickering spots - each with its modulation frequency. The light from the sample is collected with a single photodiode that, after spectrum analysis, allows for image reconstruction at speeds only limited by the AOD's bandwidth and laser power. We describe the working principle of our approach, characterize its imaging performance as a function of the number of pixels - up to 400 × 400 - and characterize dynamic events at 5000 fps.

Filterless Frequency Octupling Microwave Photonic Phase Shifter Based on Cascaded Mach–Zehnder Modulators

ABSTRACT In this paper, we propose a microwave photonic phase shifter (MPPS) without optical filtering to generate a frequency octupling microwave photonic (MWP) signal with 360º phase-shifting based on two cascaded Mach–Zehnder modulators (MZMs). Theoretical analysis is given to realize the high-quality frequency octupling MPPS by eliminating the undesired optical carrier and sidebands using an optical coupler (OC). Simulations show that the generated MMW signal has an electrical spurious suppression ratio (ESSR) higher than 33 dB. The impact of the non-ideal modulation index, extinction ratio, and phase drift is discussed and analyzed. Furthermore, the influence of different center frequencies, power, and linewidths of the laser is also analyzed.

Theoretical and Experimental Analysis of a 44 Recongurable MZI-Based Linear Optical Processor

A 4 4 reconfigurable Mach-Zehnder interferometer (MZI)-based linear optical processor is investigated through its theoretical analyses and characterized experimentally. The linear transformation matrix of the structure is theoretically determined using its building block, which is a 2 2 reconfigurable MZI. To program the device, the linear transformation matrix of a given application is decomposed into that of the constituent MZIs of the structure. Thus, the required phase shifts for implementing the transformation matrix of the application by means of the optical processor are determined theoretically. Due to random phase offsets in the MZIs resulting from fabrication process variations, they are initially configured through an experimental protocol. The presented calibration scheme allows to straightforwardly characterize the MZIs to mitigate the possible input phase errors and determine the bar and cross states of each MZI for tuning it at the required sate before programming the device. After the configuration process, the device can be programmed to construct the linear transformation matrix of the application. In this regard, using the required bias voltages, the phase shifts obtained from the decomposition process are applied to the phase shifters of the MZIs in the device.

Quantum optical control experiment using Mach–Zehnder interferometer and twisted nematic liquid crystals

A Mach–Zehnder interferometer with an optical phase control by a twisted nematic (TN) liquid crystal (LC) device was studied. In a typical TN LC device, a change in the optical rotation state of π/2 can be obtained by applying a voltage of about 5 V with a cell thickness of several-micron. The TN cell is inserted into one optical path in the Mach–Zehnder interferometer. We obtained a pattern change when voltage was applied to the LC cell due to the change of the optical interference state. As a result, a change in the number of photons under weak light conditions is observed.

Comparisons of the dynamic responses of diffusion flames subjected to acoustic disturbances in the fuel and air lines

In this paper, the dynamic responses of a laminar diffusion flame subjected to acoustic disturbances in the fuel line (ADF) and surrounded air flow (ADA) were experimentally studied. Experiments were conducted at different frequencies by keeping the velocity perturbation amplitudes for both ADF and ADA the same. Chemiluminescence data (CH* and OH*) measured by an intensified high-speed camera and density perturbations measured by a Mach–Zehnder interferometer (MZI) were used to identify the flame dynamic responses in detail. Results show that both ADF and ADA can induce flame oscillations by stimulating disturbances in the fuel flow but in different manners. The perturbations led by the ADF propagate along the flame front with a hydrodynamic wavelength, while those driven by the ADA are more likely to periodically squeeze and extend the flame region from the lateral interfaces, leading to a global periodic motion along the longitudinal direction. Both types of perturbation are difficult to propagate downstream due to the damping of flow perturbation. In addition, the flame oscillation patterns driven by the ADA remain the same under different disturbance frequencies. When the diffusion flame is simultaneously subjected to both ADF and ADA, the perturbations of them are mutually coupled at this time, but the oscillation patterns of the flame are dominated by the ADF. Due to the different mechanisms of two disturbances, the oscillation patterns after coupling are related to the disturbance frequency. Based on the above results, a model of the diffusion flame oscillation subjected to ADF and ADA was proposed.

Low-loss integrated dynamic polarization controller based on silicon photonics

<sec>A dynamic polarization controller (DPC) is an important component in fiber optic communication, optical imaging, and quantum technologies. The DPC can transform any input state of polarization (SOP) into any desired SOP to overcome polarization-related impairments resulting from high internally and externally induced birefringence. In this work, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. The whole chip is fabricated by using industry-standard silicon-on-insulator technology. Using the edge-coupling method, the coupler loss is reduced to less than 2 dB, and the total loss of DPC is reduced to 5.7 dB. Using a variable-step simulated annealing method, for a low-noise photodetector and high-static-extinction-ratio device, a dynamic polarization extinction ratio can reach more than 30 dB. The size of the DPC on the chip is 5.20 mm × 0.12 mm × 0.80 mm.</sec><sec>The DPC utilizes a 0°/45°/0°/45° structure, which can realize arbitrary polarization-based coordinate conversion with endless polarization control. The 0° and 45° transform structures and matrices are presented, and the principle of the 0° and 45° structures is explained in detail by using the Poincaré sphere.</sec><sec>A simulation using Lumerical is conducted to optimize the polarization rotator-splitter, which can transform the TM<sub>0</sub> mode light in one waveguide into the TE<sub>0</sub> mode light in the other waveguide while the TE<sub>0</sub> mode light in one waveguide remains unchanged. Based on the optimized structure, the static polarization extinction ratio of DPC can be measured to be a value greater than 40 dB.</sec><sec>The thermal phase shift (TPS) is characterized by using a Mach–Zehnder modulator. The length of the TPS is 400 μm, and the resistance of the metal heater is 2.00 kΩ. The maximum power consumed by the four TPSs is a total of 0.2 W. The modulation bandwidth of the DPC designed by our group is approximately 30 kHz. By considering an applied voltage of 5.6 V in the case of the TPS, the bandwidth–voltage product is 5.6 × 30 = 168 kHz·V.</sec><sec>To optimize the DPC parameters, such as the step length, electronic noise, and static polarization extinction ratio, numerical simulation results of the simulated annealing approach are analyzed in detail.</sec><sec>In conclusion, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. A dynamic polarization extinction ratio is obtained to be greater than 30 dB by using the variable-step simulated annealing method. The DPC is expected to be utilized in fiber or quantum communication systems to minimize size and further decrease costs.</sec>

Low-loss integrated dynamic polarization controller based on silicon photonics

<sec>A dynamic polarization controller (DPC) is an important component in fiber optic communication, optical imaging, and quantum technologies. The DPC can transform any input state of polarization (SOP) into any desired SOP to overcome polarization-related impairments resulting from high internally and externally induced birefringence. In this work, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. The whole chip is fabricated by using industry-standard silicon-on-insulator technology. Using the butting coupling method, the coupler loss is reduced to less than 2 dB, and the total loss of DPC is reduced to 5.7 dB. Using a variable-step simulated annealing method, for a low-noise photodetector and high-static-extinction-ratio device, a dynamic polarization extinction ratio can reach more than 30 dB. The size of the DPC on the chip is 5.20 mm × 0.12 mm × 0.80 mm.</sec><sec>The DPC utilizes a 0°/45°/0°/45° structure, which can realize arbitrary polarization-based coordinate conversion with endless polarization control. The 0° and 45° transform structures and matrices are presented, and the principle of the 0° and 45° structures is explained in detail by using the Poincaré sphere.</sec><sec>A simulation using Lumerical is conducted to optimize the polarization rotator-splitter, which can transform the TM<sub>0</sub> mode light in one waveguide into the TE<sub>0</sub> mode light in the other waveguide while the TE<sub>0</sub> mode light in one waveguide remains unchanged. Based on the optimized structure, the static polarization extinction ratio of DPC can be measured to be a value greater than 40 dB.</sec><sec>The thermal phase shift (TPS) is characterized by using a Mach–Zehnder modulator. The length of the TPS is 400 μm, and the resistance of the metal heater is 2.00 kΩ. The maximum power consumed by the four TPSs is a total of 0.2 W. The modulation bandwidth of the DPC designed by our group is approximately 30 kHz. By considering an applied voltage of 5.6 V in the case of the TPS, the bandwidth–voltage product is 5.6 × 30 = 168 kHz·V.</sec><sec>To optimize the DPC parameters, such as the step length, electronic noise, and static polarization extinction ratio, numerical simulation results of the simulated annealing approach are analyzed in detail.</sec><sec>In conclusion, a low-loss silicon photonics-integrated DPC is designed and demonstrated experimentally. A dynamic polarization extinction ratio is obtained to be greater than 30 dB by using the variable-step simulated annealing method. The DPC is expected to be utilized in fiber or quantum communication systems to minimize size and further decrease costs.</sec>

Design and analysis of corner scatter inclusion in photonic crystal-based ring resonator

One of the significant challenges in integrated optical systems is achieving miniaturization. Traditional components can limit the effective utilization of chip area. Devices with distinctive thickness and length characteristics, including the Mach Zehnder interferometer (MZI), the directional coupler, and waveguides, contribute to this issue, limiting the efficient use of chip area. Photonic crystals offer a solution to this problem. The proposed design results in two optical bandgap ranges, from 0.456586 to 0.675819 μm–1 and from 1.12855 to 1.16338 μm–1, both in TE mode with gap widths of 0.219233 and 0.34826 μm–1, respectively. The corresponding wavelength ranges are from 1479 to 2190 nm and 859 to 886 nm. The analysis of field propagation in the photonic crystal ring resonator (PCRR) is carried out using the finite-difference time domain (FDTD) method, while the bandgap analysis is performed by the plane wave expansion (PWE) method. This work primarily focuses on the incorporation of corner scatters in the PCRR. Corner scatters play a crucial role in guiding the field smoothly inside the ring, thus preventing the localization of light within the structure. After the simulation, various attributes were compared for both structures. At a resonant wavelength of 1550 nm, the input intensity is measured as 0.0591 a.u., and the output intensities for with and without corner scatter are 0.0458 and 0.0539 a.u., respectively.

Efficient optical nonreciprocity based on four-wave mixing effect in semiconductor quantum well

Optical nonreciprocity has been a popular research topic in recent years. Semiconductor quantum wells (SQWs) play a key role in many high-performance optoelectronic devices. In this paper, we propose a theoretical scheme to achieve nonmagnetic optical nonreciprocity based on the four-wave mixing effect in SQW nanostructures. Using the experimentally available parameters, the nonreciprocal behavior of the probe field in forward direction and backward direction is achieved through this SQW, where both nonreciprocal transmission and nonreciprocal phase shift have high transmission rates. Furthermore, by embedding this SQW nanostructure into a Mach-Zender interferometer, a reconfigurable nonreciprocal device based on high transmission nonreciprocal phase shift that can be used as an isolator or a circulator, is designed and analyzed. The device can be realized as a two-port optical isolator with an isolation ratio of 92.39 dB and an insertion loss of 0.25 dB, and as a four-port optical circulator with a fidelity of 0.9993, a photon survival probability of 0.9518 and a low insertion loss with suitable parameters. Semiconductor media have the advantages of easier integration and tunable parameters, and this scheme can provide theoretical guidance for implementing nonreciprocal and nonreciprocal photonic devices based on semiconductor solid-state media.

Dual-polarization photonic integrated biosensor in a Mach-Zehnder interferometer with coherent phase readout

Photonic integrated biosensors have garnered considerable attention due to their promising applications in various fields such as healthcare. Differentiating specific targets from interfering background effects is a challenging task. In this work, a dual-polarization Mach-Zehnder interferometer (MZI) with coherent phase readout is proposed to identify refractive index changes from different layers above the waveguide surface, thus improving sensor specificity. All the system building blocks have been designed for a 300 nm-thick silicon nitride platform, fabricated and characterized. The first experimental results show a bulk waveguide sensitivity of 0.17 RIU/RIU for TE polarization and 0.25 RIU/RIU for TM, confirming the correct functioning of the sensors when operating for each polarization separately. Future work will focus on simultaneous sensing with both polarizations and experiments with layered variation of refractive indices.

Enabling secure high-speed data transmission: Coherent chaotic optical communication with deep learning and electro-optic feedback

Coherent chaotic optical communication represents a present-day technique for attaining excessive-pace, long-distance statistics transmission with first-rate protection. This approach combines deep-gaining knowledge of chaotic synchronization (DLM-CS) models with virtual-sign processing algorithms to counteract fibre transmission impairments, resulting in a sturdy and green communiqu? device. Chaotic indicators are generated through electro-optic feedback, explicitly using Optical Intensity Chaos and Optical Phase Chaos (OIC), facilitated by Mach-Zehnder Modulator and Interferometer (MZM/MZI) modulators. Additionally, device getting to know-primarily based algorithms are hired to mitigate non-linearity in the communiqu? channel. Performance analysis in this context encompasses Bit Error Rate(BER), lengthy-distance communication competencies, chaotic signal periodicity, chaos synchronization, and safety. This technique allows for steady, high-speed facts transmission over prolonged distances, making it an important era for numerous packages, which includes telecommunications and statistics safety.

Low Coherence Interferometry Measurement: An Algorithm for fast processing with low noise and phase linearisation

This work proposes a signal processing algorithm to analyse the optical signal from a Low Coherence Interferometric (LCI) system. The system uses a Mach-Zehnder (MZ) interferometer to interrogate a Fabry-Perot cavity, working as an optical sensor. This algorithm is based on the correlation and convolution operations, which allows the signal to be reconstructed based on itself, as well as, on the linearization of the signal phase, allowing the non-linearities of the actuator incorporated on the MZ interferometer to be compensated. The results show a noise reduction of 30 dB in the signal acquired. As a result, a reduction of 8.2 dB in the uncertainty of the measurement of the physical measurand is achieved. It is also demonstrated that the phase linearization made it possible to obtain a coefficient of determination (namely, R-squared) higher than 0.999.

Highly Sensitive Strain and Temperature Sensors Based on Vernier Effect in Cascaded Mach–Zehnder Interferometer and Sagnac Interferometer

Highly Sensitive Strain and Temperature Sensors Based on Vernier Effect in Cascaded Mach–Zehnder Interferometer and Sagnac Interferometer