Compact Mach-Zehnder Interferometer Research Articles

Compact and fast-response optical switch based on complex refractive index engineering.

The optical switch is a crucial device in integrated photonic circuits. Among the various types of optical switches available, the on-off Mach-Zehnder interferometer is one of the most widely used structures. However, compared with other structures, such as a microring, the large footprint of a Mach-Zehnder interferometer significantly restricts the integration density. In this paper, we propose a compact Mach-Zehnder interferometer based on complex refractive index engineering. By manipulating the complex index of the material in the structure, the lateral size of the device can be compressed down to only 3.25 µm. Moreover, the reducing of the space between heaters and waveguides leads to a fast response of only 1.9 µs. Our work offers a new, to the best of our knowledge, approach of a compact integrated optical switch, and opens a new avenue for application of absorbing materials.

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.

Simultaneous measurement of temperature and relative humidity by compact Mach-Zehnder interferometer and Fabry-Perot interferometer

A novel and compact temperature and relative humidity (RH) simultaneously measurement sensor based on compact Mach-Zehnder interferometer (MZI) and Fabry-Perot interferometer (FPI) is proposed and experimental implemented. The sensing structure is made by splicing a 200 μm single mode fiber (SMF) between two 10 cm SMFs with large core-offset. The core-offset distance is 62.8 μm coated with RH sensitive material graphene quantum dots and polyvinyl alcohol (GQDs-PVA). The transmitted structure acts as MZI, and the reflected structure acts as FPI, then the simultaneous detection of temperature and RH can be achieved by monitoring the spectrums of FPI and MZI, respectively. The sensitivity to RH is −0.132 nm/%RH with resolution of 0.15 %RH, and the sensitivity to temperature is 0.37 nm/°C with the resolution of 0.05 °C. The proposed sensor is compact, high sensitivity, simple making and low cost.

Compact Mach–Zehnder interferometer based on processed hollow-core fiber for gas pressure sensing

A Mach–Zehnder interferometer based on processed hollow-core fiber (HCF) is proposed and experimentally demonstrated for gas pressure sensing. The fiber sensor is fabricated by splicing a segment of HCF between the two coreless fibers. One end of the HCF is processed into an open cavity, which allows gas pressure of the air-core to be equivalent to that of the external environment. Gas pressure change induces refractive index change of the air-core, thus the measurement of gas pressure can be achieved by monitoring wavelength shift of the interference pattern. The proposed fiber sensor exhibits a high gas pressure sensitivity of 9.35 nm / MPa in the range from 0.1 to 0.04 MPa and a temperature sensitivity of 30 pm / ° C in the range from 30°C to 90°C. Furthermore, the fiber sensor processes the advantages of compactness, low cost, and all-fiber configuration, which makes it suitable for gas pressure measurement.

A high sensitivity gas pressure sensor based on femtosecond laser micro/nano processing

A compact and novel Mach-Zehnder interferometer used for gas pressure sensing is proposed and demonstrated experimentally. The sensor is constructed by fusion splicing a short piece of dual side-hole fiber (DSHF) in between two sections of multimode fibers (MMF). Interference occurs as the optical path length difference (OPLD) between light beams along air holes and silica of the DSHF. With the opening drilled on one air hole by femtosecond laser micro/nano processing, the filled gas directly affects light beam along this air hole, which results in the interference spectrum shift. Experimental results show that the sensor exhibits a high sensitivity of −8.58 nm/MPa with the increasing gas pressure. The sensor has potential application in gas pressure sensing for its advantages of high sensitivity, low temperature crosstalk and easy fabrication.

Design of graphene-on-germanium waveguide electro-optic modulators at the 2μm wavelength

The spectral region around 2μm wavelengths is of special significance for applications in optical communications, which is facing a capacity crunch at the telecommunication band. Development of CMOS-compatible on-chip photonic and optoelectronic devices operating in this spectral region is highly demanded but still at its infancy. In this paper, we present a design of graphene-on-germanium slot waveguides at the wavelength of 2μm. Due to the optical-field enhancement and poor mode confinement, light-matter interactions are enhanced in the graphene-on-germanium slot waveguide. Moreover, the influence of the refractive index contrast and the number of integrated graphene layers on the optical absorption enhancement of the slot waveguide is studied. Based on the graphene-on-slot waveguide configuration, energy-efficient and compact Mach-Zehnder interferometer and microring resonator phase modulators are designed. Our study paves the way for the development of on-chip electro-optic modulators at 2μm wavelengths.

Electro-optic routing of photons from a single quantum dot in photonic integrated circuits

Recent breakthroughs in solid-state photonic quantum technologies enable generating and detecting single photons with near-unity efficiency as required for a range of photonic quantum technologies. The lack of methods to simultaneously generate and control photons within the same chip, however, has formed a main obstacle to achieving efficient multi-qubit gates and to harness the advantages of chip-scale quantum photonics. Here we propose and demonstrate an integrated voltage-controlled phase shifter based on the electro-optic effect in suspended photonic waveguides with embedded quantum emitters. The phase control allows building a compact Mach-Zehnder interferometer with two orthogonal arms, taking advantage of the anisotropic electro-optic response in gallium arsenide. Photons emitted by single self-assembled quantum dots can be actively routed into the two outputs of the interferometer. These results, together with the observed sub-microsecond response time, constitute a significant step towards chip-scale single-photon-source de-multiplexing, fiber-loop boson sampling, and linear optical quantum computing.

A Compact Mach–Zehnder Interferometer Using Composite Plasmonic Waveguide for Ethanol Vapor Sensing

The finite element method (FEM) has attracted a considerable interest in the past few decades for the analysis of a wide range of dielectric waveguides. This method can handle isotropic and anisotropic material properties and arbitrary-shaped complex dielectric discontinuities more efficiently and accurately than any other methods. A modified H-field based full-vectorial finite element method is used for a rigorous analysis of a composite plasmonic waveguide as an efficient ethanol vapor sensor where a porous ZnO (P-ZnO) layer is used as low index material in between high index silicon and silver metal layer. Enhanced field confined into low index slot is utilized for ethanol vapor sensing which has many potential applications in chemical industries. It is reported here that a high waveguide sensitivity over 0.7 per RIU could be realized with our proposed design depending on the porosity of the ZnO layer. For accurate detection of refractometric changes, a compact Mach–Zehnder interferometer is designed where maximum phase sensitivities of 0.30, 0.34, 0.38, and 0.40 are shown to be achieved for $ \sim $ 50% volume fraction of ethanol into porous ZnO layer with porosity, P = 30%, 40%, 50%, and 60%, respectively. The complete investigation has been carried out at the well-known telecommunication wavelength 1550 nm and with our in-house, accurate full-vectorial FEM code.

Compact Mach–Zehnder interferometer-based no-core fiber hollow-core fiber no-core fiber structure

We propose and experimentally demonstrate a compact Mach–Zehnder interferometer (MZI)-based no-core fiber hollow-core fiber no-core fiber (NHN) structure. Two segments of the no-core fiber embedded on two ends of the hollow-core fiber are employed as beam splitter and combiner, which realize an MZI to measure temperature and strain. With the variation of the temperature and strain, the measurement is achieved by monitoring the transmission spectrum shift of the MZI. The results show that the proposed sensor has a temperature sensitivity of 30.92 pm/°C in the range from 30°C to 90°C, and strain sensitivity of 0.652 pm/μϵ in the range from 0 to 700 μϵ, respectively. The NHN structure exhibits the advantages of compactness, easy fabrication, and low cost, which shows the potential sensing applications of the proposed fiber structure.

Optically monitoring and controlling nanoscale topography during semiconductor etching

We present epi-diffraction phase microscopy (epi-DPM) as a non-destructive optical method for monitoring semiconductor fabrication processes in real time and with nanometer level sensitivity. The method uses a compact Mach–Zehnder interferometer to recover quantitative amplitude and phase maps of the field reflected by the sample. The low temporal noise of 0.6 nm per pixel at 8.93 frames per second enabled us to collect a three-dimensional movie showing the dynamics of wet etching and thereby accurately quantify non-uniformities in the etch rate both across the sample and over time. By displaying a gray-scale digital image on the sample with a computer projector, we performed photochemical etching to define arrays of microlenses while simultaneously monitoring their etch profiles with epi-DPM. Semiconductor etching can now be monitored in real time at nanoscale resolution using a non-destructive optical imaging technique that combines a conventional microscope with a compact Mach–Zehnder interferometer. Developed by Chris Edwards, Amir Arbabi, Gabriel Popescu, and Lynford Goddard at the University of Illinois at Urbana-Champaign in the United States, epi-diffraction phase microscopy makes it possible to collect three-dimensional videos of semiconductor fabrication processes using a CCD camera. The approach is able to measure etch rates at each location across the sample with a resolution of 0.085 nm s−1 per pixel. Such an in situ monitoring capability could be useful for improving the manufacturing quality of a wide variety of semiconductor devices.

In-Fiber Fabry–Perot and Mach–Zehnder interferometers based on hollow optical fiber fabricated by arc fusion splicing with small lateral offsets

Two kinds of in-line all-fiber interferometers, including tip Fabry–Perot interferometer and compact Mach–Zehnder interferometer, are proposed and demonstrated by fusion splicing a short section of hollow optical fiber (HOF) to the end of single-mode fiber (SMF) and sandwiching a section of HOF in between two sections of SMF, respectively. In both interferometers, a small lateral offset is introduced to induce the optical path difference required to form the interferometer. Temperature responses of both types of interferometers are studied experimentally. It is anticipated that such easy making, compact and low-cost fiber-optic interferometers could find important applications in practice.

A very compact Mach–Zehnder interferometer with left-handed material

A very compact Mach–Zehnder interferometer (MZI) composed of two parallel straight waveguides with left-handed material (LHM) layers is proposed. The operating principle and characteristics of the MZI with electro-optic material (EOM) core are analyzed by using the supermode theory and coupled mode theory. The result shows that regardless of material loss, a very compact MZI of only 0.87mm×0.022mm can be achieved by utilizing EOM with ultrahigh electro-optic coefficient, which means a new way to fulfill a very compact electro-optic modulator or optical switch. The absorption effect of the proposed MZI is also analyzed by perturbation method which is generated by lossy LHM layers.

Mach-Zehnder interferometer based on core-cladding mode coupling in single mode fibers

In this paper, a novel simple but effective method is presented to construct compact all-fiber Mach-Zehnder (M-Z) interferometer based on CO2-lasermachined micro-notches in single mode fibers. Interference fringes are obtained, and temperature, force, and bending characteristics of the interferometer have been experimentally investigated. Such a compact fiber component with acceptable sensing performances makes it a good candidate for the measurement of numerous physical parameters.

Compact Mach-Zehnder interferometer based on self-collimation of light in a silicon photonic crystal

We demonstrate a compact silicon photonic crystal Mach-Zehnder interferometer operating in the self-collimation regime. By tailoring the photonic band structure such as to produce self-collimated beams, it is possible to design beam splitters and mirrors and combine these to a 20 x 20 microm(2) format. With transmission spectroscopy we find a pronounced unidirectional optical output, the output ratio being as high as 25 at the self-collimation wavelength. Furthermore, the self-collimated beams and the unidirectionality are clearly observed in real space using near-field and far-field optical microscopy. Interpretation of the optical data is strongly supported by different types of simulations.

Compact and low insertion loss (~10 dB) Mach-Zehnder interferometer-synchronized arrayed-waveguide grating multiplexer with flat-top frequency response

We have developed a compact Mach-Zehnder interferometer (MZI)-synchronized arrayed-waveguide grating (AWG) multiplexer with 40 100-GHz-spaced channels using 1.5-% Delta waveguides. This MZI-synchronized AWG has a chip size of only 35 x 28 mm(2), and a low insertion loss of 1.0 - 1.2 dB with a flat-top frequency response. This low insertion loss is achieved by i) installing spot-size converters at the ends of optical input and output waveguides, and ii) employing a narrow gap in a directional coupler at the junction of the MZI and AWG. This device exhibited other excellent characteristics including a wide 0.5-dB passband of more than 45 GHz and a low adjacent crosstalk of less than -35 dB.

F2-laser micromachining of fibre-tipped Mach-Zehnder interferometer

A compact Mach-Zehnder interferometer (MZI) with high 27 dB modulation ratio was fabricated on the end facet of a singlemode optical fibre by F2-laser micromachining. The deep ultraviolet (157 nm) laser excised a shallow phase-shift channel across one-half of the fibre core to generate sinusoidal interference spectra controllable by the laser-etch depth.

Silicon-based integrated interferometer with phase modulation driven by surface acoustic waves

As a novel application of silicon-based integrated optics, results from a proposed compact Mach-Zehnder interferometer are presented. The deposition of a ZnO thin-film transducer upon the reference arm of the interferometer transforms this optically passive device into a device with active sinusoidal phase modulation.

Compact all-fibre Mach-Zehnder devices

A single-mode optical-fibre switch which is electrically activated has been fabricated. This device is achieved by forming two couplers in series on a pair of single-mode optical fibres to provide a compact Mach-Zehnder interferometer (MZI). Power switching in the output arms is achieved by introducing a phase shift or path difference in the MZI by various means. The application of the device as a wavelength-selective switch is also considered.

Efficient single mode operation of a CW ring dye laser with a Mach-Zehnder interferometer

Stable single mode operation of a ring dye laser is obtained with the combination of a Mach-Zehnder interferometer (MZI), three plate birefringent filter, a single thin etalon and a unidirectional diode. The MZI eliminates the fractional insertion loss due to beam walk-off and distortion which an intracavity etalon must introduce in order to select single frequency operation. We experimentally demonstrate the low insertion loss, single mode stability and frequency tuning of a ring dye laser using a specially designed, compact MZI. Finally, we propose MZIs with no coatings, which should permit extremely low loss broadband operation.