Traditional Mach-Zehnder Interferometer Research Articles

Enhanced phase sensitivity in a Mach-Zehnder interferometer via photon recycling.

We propose an alternative scheme for phase estimation in a Mach-Zehnder interferometer (MZI) with photon recycling. It is demonstrated that with the same coherent-state input and homodyne detection, our proposal possesses a phase sensitivity beyond the traditional MZI. For instance, it can achieve an enhancement factor of ∼9.32 in the phase sensitivity compared with the conventional scheme even with a photon loss of 10% on the photon-recycled arm. From another point of view, the quantum Cramér-Rao bound (QCRB) is also investigated. It is found that our scheme is able to achieve a lower QCRB than the traditional one. Intriguingly, the QCRB of our scheme is dependent of the phase shift ϕ while the traditional scheme has a constant QCRB regardless of the phase shift. Finally, we present the underlying mechanisms behind the enhanced phase sensitivity. We believe that our results provide another angle from which to enhance the phase sensitivity in a MZI via photon recycling.

Biosensor based on plasmonic Mach-Zehnder interferometer with metallic gratings

In this paper, a Mach-Zehnder interferometric sensing structure based on silver nanochains of surface plasmons is optimized. The structure consists of a reference arm, a sensing arm and a nanowire waveguide. Nanowire waveguides are composed of silicon nanowires wrapped with a certain thickness of silver. Introduce two silver nanochains as the reference arm and the sensing arm of the Mach-Zehnder interferometer. And research the transmission characteristics of the designed structure. Improve the accuracy and sensitivity of the designed structure by reducing the transmission loss. Compared with two identical silver nanowires as the reference arm and the sensing arm. After the reference arm and the sensing arm are changed to silver nanochains, the transmission characteristics are significantly improved, and the loss per unit length is obviously reduced. This is because the long-range or coulomb interaction between the unit structures of the silver nano-chains enhances the electromagnetic field in the structure, thereby reducing the transmission loss. We set the lattice constants of the two silver nanochains to different situations. The study found that under the wider width of silicon-coated silver nanowires and certain duty ratios. The unit transmission loss of a structure containing asymmetric silver nanochains is smaller than that of a structure containing symmetric silver nanochains. It can be known that silver nanoparticle chains with small loss can compensate for the transmission loss of silver nanoparticle chains with large loss. Using this feature, we further optimized the design structure and changed one side of the silver nano-chain to nano-wire. Change the lattice constant and duty cycle of the silver nanochain on the other side. We have found that in most cases, this type of structure has better transmission characteristics than a structure containing two silver nanochains and a structure containing two silver nanowires. Our design structure can greatly reduce the transmission loss of the traditional Mach-Zehnder interferometer. Moreover, the fault tolerance rate is high in the preparation process of the structure. It has huge potential application value in practical application.

Double Phase Matching in MZI With Antiresonant Effect for Optical Fiber Sensor Application

In the traditional Mach–Zehnder interferometer, only one phase matching condition needs to be satisfied for destructive interference. Here, we propose and demonstrate a Mach–Zehnder interferometer with double phase matching condition, which satisfies both the destructive condition of double beam interference and the resonant condition of anti-resonant effect. Different from the traditional method, the interference is construed as a coherent superposition between anti-resonant beam and cladding one. The effect of the multimode fiber length on the energy distribution and transmission spectrum is analyzed precisely. The experimental results show that the intensity of the wavelength meeting double phase matching condition is extremely sensitive to both strain and temperature. The maximum intensity sensitivity to strain and temperature are up to 16.1 dB/mv and 0.181 dB/°C, respectively. Compared with the previous work, the sensitivities have been improved several times or even tens of times. The proposed Mach–Zehnder interferometer with double phase matching condition can improve the dip depth, which has a great potential value in sensing application.

Enhanced phase sensitivity with a nonconventional interferometer and nonlinear phase shifter

We propose a theoretical scheme of an enhanced phase sensitivity by introducing a nonlinear phase shifter to the nonconventional interferometer consisting of a balanced beam splitter (BBS) and an optical parameter amplifier (OPA), a modified nonlinear interferometer (MNI). Then we use coherent state and even coherent state as inputs and homodyne detection at one output port of the MNI for phase sensitivity, both without and with photon losses. We find that the nonlinear phase shifter can not only improve phase sensitivity, but also significantly resist the decoherence from photon losses. In comparison to both the BBS+OPA scheme with linear phase shifter and the traditional Mach–Zehnder interferometer with nonlinear one, the phase sensitivity of the MNI scheme shows the best performance. It is interesting that the nonlinear phase shifter can stimulate potential of the OPA, although there is no improvement in signal-to-noise ratio beyond standard quantum limit for the BBS+OPA scheme with a linear phase shifter.

A Novel Mach–Zehnder Interferometric Temperature Sensor Based on a Symmetrical Double-Grooved Structure

In this paper, a novel temperature sensor based on the Mach-Zehnder interferometer (MZI) has been proposed and experimentally investigated. The sensor consists of a symmetrical double-grooved structure fabricated by a high-frequency pulsed CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> laser. Some key factors affecting the transmission spectrum, such as the writing depth and interference length, have been analyzed in detail. In addition, the temperature sensitivity of the sensor is obtained in theory, by analyzing the influences of the effective refractive index and the interference length on it. The experimental results demonstrate that the wavelength shifts linearly toward longer wavelength, which agrees with the theoretical analysis. The temperature sensitivity of 230 pm/°C with a linear correlation coefficient of 0.99 can be achieved in the temperature ranging from 20 °C to 90 °C. The repeatability of the sensor also is studied. Compared with traditional MZI sensors, the proposed sensor has a high temperature sensitivity. And it is suitable for temperature measurement applications.

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.

Phase estimation of phase shifts in two arms for an SU(1,1) interferometer with coherent and squeezed vacuum states**Project supported by the National Natural Science Foundation of China (Grant Nos. 11474095, 11654005, and 11234003) and the National Key Research and Development Program of China (Grant No. 2016YFA0302000).

We theoretically study the quantum Fisher information (QFI) of the SU(1,1) interferometer with phase shifts in two arms by coherent ⊗ squeezed vacuum state input, and give the comparison with the result of phase shift only in one arm. Different from the traditional Mach–Zehnder interferometer, the QFI of single-arm case for an SU(1,1) interferometer can be slightly higher or lower than that of two-arm case, which depends on the intensities of the two arms of the interferometer. For coherent ⊗ squeezed vacuum state input with a fixed mean photon number, the optimal sensitivity is achieved with a squeezed vacuum input in one mode and the vacuum input in the other.

Investigation of a low-voltage polymeric 2 × 2 Mach-Zehnder interferometer optical switch using five-serial-coupled electro-optic microrings

Structure and design scheme of a Mach-Zehnder interferometer (MZI) EO switch, whose one arm is assisted by five serial-coupled microrings, is proposed and optimized. Using the derived formulas and expressions of output power, insertion loss and crosstalk, detailed design and optimization are performed. Under 1550-nm wavelength, analysis results indicate that the device can perform normal switching function and the low switching voltage is as low as 0.99V. The insertion loss is 1.15dB at bar state, whereas that is 1.97dB at cross state; the crosstalk is −17.8dB at bar state, whereas that is −12.3dB at cross state. The voltage-length product of the proposed switching device is about 0.21V·mm, which is 32 times smaller than that of the traditional MZI EO switch (6.69V·mm) with the same waveguide and electrode parameters. Therefore, due to small footprint size and extremely low switching voltage, this switching configuration can be densely integrated onto optoelectronic chips.

Tunable fiber laser based on a cascaded structure consisting of in-line MZI and traditional MZI

A tunable erbium-doped fiber (EDF) laser with a cascaded structure consisting of in-line Mach-Zehnder interferometer (MZI) and traditional MZI is proposed. The transmission spectrum of the in-line MZI is modulated by the traditional MZI, which determines the period of the cascaded structure, while the in-line MZI’s transmission spectrum is the outer envelope curve of the cascaded structure’s transmission spectrum. A stable single-wavelength lasing operation is obtained at 1 527.14 nm. The linewidth is less than 0.07 nm with a side-mode suppression ratio (SMSR) over 48 dB. Fixing the in-line MZI structure on a furnace, when the temperature changes from 30 °C to 230 °C, the central wavelength can be tuned within the range of 12.4 nm.

A Novel Electronically-Controlled Optical Switch

In this paper, we consider a novel approach to an electronically controlled optical switch, which would be able to switch digital optical signals from one waveguide into other, suitable for subsequent optical communication. The switch operates based on the two TE mode interference, and the free-carrier injection from the published driver circuit. The switch designs with 1% refractive index decrease and the driver circuit are both consistent with the existing unmodified 45 nm SOI-CMOS foundry process. Our switch designs with 1% refractive index decrease of Si, have a few hundred times smaller area footprint on the chip, a switching time that is several times shorter, and also several times smaller energy consumption, than the optical switch based on a traditional Mach–Zehnder interferometer. Also, our switch shows reasonably good simulated performance. We derived the analytical model from Maxwell's equations for our switch design, and showed the match with the simulated results and also mode solver calculation results.

Slow light Mach-Zehnder interferometer as label-free biosensor with scalable sensitivity.

The design, fabrication, and characterization of a label-free Mach-Zehnder interferometer (MZI) optical biosensor that incorporates a highly dispersive one-dimensional (1D) photonic crystal in one arm are presented. The sensitivity of this slow light MZI-based sensor scales with the length of the slow light photonic crystal region. The numerically simulated sensitivity of a MZI sensor with a 16 μm long slow light region is 115,000 rad/RIU-cm, which is sevenfold higher than traditional MZI biosensors with millimeter-length sensing regions. An experimental bulk refractive index detection sensitivity of 84,000 rad/RIU-cm is realized and nucleic acid detection is also demonstrated.

Design and Analysis of an all-fiber MZI Interleaver Based on Fiber Ring Resonator

An all-fiber Mach-Zehnder interferometer (MZI) interleaver using one planar 3×3 fiber coupler, one 2×2 fiber coupler and one 8-shaped fiber ring resonator is developed by the new configuration. Based on its structure, the output spectrum expression is established and described by using the principle of fiber transmission and the matrix transfer function. The results of numerical simulation indicate that when the length difference of interference arms and the coupling coefficients of the couplers are some certain values, it obtains a uniform flat-top passband and similar to rectangular output spectrum. Compared with the traditional MZI interleaver, the isolation in stopband and the rolloff in transition band are strengthen, the 25dB stopband bandwidth and 0.5dB passband bandwidth are simultaneously remarkably improved. Compared with the asymmetrical ring resonator MZI interleaver, the influence of transmission loss on extinction ratio can be effectively reduced. The device has a certain ability to resist the deviation, which reduces the difficulties in fabricating it. The experiment results agree with the theoretical analysis well. The interleaver designed by the proposed approach has favorable performance, which has the potential application value in optical fiber communication system.

The phase sensitivity of an SU(1,1) interferometer with coherent and squeezed-vacuum light

We theoretically study the phase sensitivity of an SU(1,1) interferometer with a coherent state in one input port and a squeezed-vacuum state in the other input port using the method of homodyne detection. In this interferometer, beam splitting and recombination are generated by the parametric amplifiers instead of the beam splitters. Compared with the traditional Mach–Zehnder interferometer, the phase sensitivity of this interferometer can be improved due to the amplification process of the parametric amplifiers. Combined with the squeezed state input, the sensitivity can be improved further due to the noise reduction. The phase sensitivity of our scheme can approach the Heisenberg limit and the associated optimal condition is analyzed. The scheme can be implemented with current experimental technology.

Linear photonic frequency discriminator on As_2S_3-ring-on-Ti:LiNbO_3 hybrid platform

We report a photonic frequency discriminator built on the vertically integrated As₂S₃-ring-on-Ti:LiNbO₃ hybrid platform. The discriminator consists of a Mach Zehnder interferometer (MZI) formed by the optical path length difference (OPD) between polarization modes of Ti-diffused waveguide on LiNbO₃ substrate and a vertically integrated As₂S₃ race-track ring resonator on top of the substrate. The figures of merit of the device, enhancement of the signal-to-3rd order intermodulation distortion (IMD3) power ratio and corresponding 3rd order intercept point (IP3) over a traditional MZI, are demonstrated through device characterization.

Design of a spectrum-expanded polymer Mach–Zehnder interferometer electro-optic switch using two-phase generating couplers

A novel structure, thorough analysis and design technique are presented for a kind of polymer Mach–Zehnder Interferometer (MZI) electro-optic (EO) switch consisting of two-phase generating couplers (PGCs). By optimizing the PGCs structure, the output spectrum of the two PGCs based MZI EO switch is greatly expanded to almost six times of that of the traditional MZI EO switch with two 3 dB directional couplers. Under a central wavelength of 1550 nm, the driving voltages of the designed switch are as low as about 0 (ON state) and ±0.925 V (OFF state) with an EO region length of 5000 μm. A wide spectrum more than 350 nm (1380∼1730 nm) is achieved, and within this wavelength range, the crosstalk is less than −30 dB, and the insertion loss is less than 5.91 dB which is larger than that of the traditional MZI EO switch due to the longer waveguide length by introducing two PGCs. The design technique on the two PGCs based MZI EO switch is supported to be reasonable compared with the beam propagation method (BPM). The proposed structure shows potential wide applications especially in optical cross-connect (OXC) and optical add-drop multiplexing (OADM) systems.

Large Signal Analysis of the Michelson Interferometer with Gires-Tournois Interferometers in its Arms

A mathematical model for the transfer function of the Michelson interferometer with Gires-Tournois interferometers in its arms is presented. The model, basically a sine-series function, can easily yield closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output when the input is formed of large-amplitude multisinusoidal voltage. The special case of two-tone equal-amplitude input voltage is considered in detail. The results show that the third-order intermodulation component is always higher than the third-harmonic component. The results also show that the linearity of the Michelson interferometer with Gires-Tournois interferometers in its arms improves with the increase of the front mirror reflectivity. Moreover, the results show that the third-order intermodulation exhibits a minimum for relatively large values of the front mirror reflectivity. Furthermore, compared with the traditional Mach-Zehnder interferometer, the results show that a reduction of 15 dB in the third-order intermodulation can be achieved even for relatively small values of the front mirror reflectivity.