Waveguide Mach-Zehnder Interferometer Research Articles

Femtosecond laser inscribed fiber Bragg grating and Mach-Zehnder interferometer cascade sensing structure for temperature and relative humidity simultaneous measurement

A femtosecond (fs) laser inscribed cascade structure of a fiber Bragg grating (FBG) and a gap-coupled cladding waveguide Mach-Zehnder interferometer (CWMZI) is proposed and demonstrated, which can be used to simultaneously measure temperature and relative humidity. The structure can also be used as a breathing sensor. Transmission dip wavelength of the FBG is used for the temperature monitoring based on its temperature response. Meanwhile, gap-coupled CWMZI is used for relative humidity monitoring because the gap part of the CWMZI is very close to the cladding surface, it is very sensitive to refractive changes caused by ambient humidity variations. Experiments show a temperature sensitivity of 0.01104 nm/°C in a temperature range of 20 °C to 125 °C, and a high relative humidity sensitivity response of −0.0793 nm/%RH in a relative humidity range of 50 % to 80 %. Breathing signal monitoring is also successfully demonstrated using the FBG-CWMZI cascading structure.

Optofluidic chip with directly printed polymer optical waveguide Mach-Zehnder interferometer sensors for label-free biodetection

Optofluidic devices hold great promise in biomedical diagnostics and testing because of their advantages of miniaturization, high sensitivity, high throughput, and high scalability. However, conventional silicon-based photonic chips suffer from complicated fabrication processes and less flexibility in functionalization, thus hindering their development of cost-effective biomedical diagnostic devices for daily tests and massive applications in responding to public health crises. In this paper, we present an optofluidic chip based on directly printed polymer optical waveguide Mach-Zehnder interferometer (MZI) sensors for label-free biomarker detection. With digital ultraviolet lithography technology, high-sensitivity asymmetric MZI microsensors based on a width-tailored optical waveguide are directly printed and vertically integrated with a microfluidic layer to make an optofluidic chip. Experimental results show that the sensitivity of the directly printed polymer optical waveguide MZI sensor is about 1695.95 nm/RIU. After being modified with capture molecules, i.e., goat anti-human immunoglobulin G (IgG), the polymer optical waveguide MZI sensors can on-chip detect human IgG at the concentration level of 1.78 pM. Such a polymer optical waveguide-based optofluidic chip has the advantages of miniaturization, cost-effectiveness, high sensitivity, and ease in functionalization and thus has great potential in the development of daily available point-of-care diagnostic and testing devices.

Terahertz on-chip sensor based on Mach-Zehnder waveguide interferometer for selective recognition of reducing drug

The selective detection of biochemical substances with high sensitivity in the terahertz (THz) band has emerged as a prominent research area, attracting significant attention. Waveguide-on-chip detection of biochemical substances can effectively enhance the interaction between samples and waves, but there is a lack of reports in the THz band. In this work, a dual-channel metallic parallel-plate waveguide (PPWG) is applied to creatively construct a THz Mach-Zehnder interferometer (MZI) sensor for highly sensitive and selective detection of reducing drug on a chip. This sensor exhibits a strong numerical response of 0.75 THz/RIU, allowing for dynamic sensitivity adjustment through mechanically tuning structural parameters, and it is modified through in-situ growth of Prussian blue (PB) to achieve the selective detection of reducing drug. The experiments confirm that the designed sensor-on-chip possesses exceptional detection sensitivity for cysteamine, reaching an impressive maximum sensitivity of 0.09 GHz/nmol and a low limit of detection of 88 nmol. The modified chip exhibits selective detection of cysteamine, demonstrating a maximum response difference of 4.2 times compared to other configurations. Collectively, a pioneer validates the feasibility of the highly sensitive MZI chip in the THz regime and opens up new possibilities for advancing THz biochemical sensing.

Lowering The Bit‐Energy of Electro‐Optic Modulators Via Polarization‐Phase Modulation in Thin‐Film BaTiO3 Ferroelectric Crystal Waveguide

AbstractThe electro‐optic (EO) modulator is a crucial device for achieving high‐speed optical communication and optical interconnection by loading the high‐frequency electrical signals onto the optical carrier. To date, modern communication technique demands for a low energy consumption for green data center establishment. In this work, a thin‐film BaTiO3 crystal waveguide Mach–Zehnder interferometer (MZI) type EO intensity modulator is experimentally implemented and its dynamic‐polarization interference process involving a phase‐polarization modulation (PPM) scheme other than conventional optical phase modulation (OPM) is carefully analyzed. Its findings show that the PPM scheme can efficiently reduce the half‐wave voltage () and the equivalent half‐wave voltage () of the modulator. Then, a new theory of deriving the bit energy (BE) from is put forward, which has proven that the BE value under PPM is lower than the OPM counterpart. The EO modulator prototype featuring a length of 1.4 mm, = 3.0 V and BE = 1.2 pJ/bit match well with the numerical calculations, thus validating the feasibility to achieve a BE<0.2 pJ/bit for an EO modulator through optimization of the electrode gap and state‐of‐the‐art fabrication techniques in the near future.

Miniature fiber-optic near-surface gap-coupled cladding waveguide Mach-Zehnder interferometric refractive index sensor inscribed by femtosecond laser

A miniature fiber-optic gap-coupled cladding waveguide Mach-Zehnder interferometer (MZI) is proposed and demonstrated for high-sensitive refractive index measurement. Two straight cladding waveguides respectively coupled with the fiber core are inscribed by a femtosecond laser (fs) to form the MZI structure. At their far ends, the two cladding waveguides are very close to the cladding surface, and a short separation was intentionally designed for the coupling of light between them and generating light field with evanescent wave expanded outside the cladding surface, which makes the MZI structure very sensitive to ambient refractive variations. In a refractive index range of 1.34–1.42, a high sensitivity of −59.90238 nm/RIU is achieved simultaneously with good linearity. The sensing structure also shows good characteristic of temperature insensitivity, which may find practical applications in chemical or biological sensing.

Waveguide Mach-Zehnder interferometer to enhance the sensitivity of quantum parameter estimation.

The waveguide Fabry-Perot interferometer (FPI) (see, e.g., in Phys. Rev. Lett.113, 243601 (2015)10.1103/PhysRevLett.115.243601 and Nature569, 692 (2019)10.1038/s41586-019-1196-1), instead of the free space's one, have been demonstrated for the sensitive quantum parameter estimations. Here, we propose a waveguide Mach-Zehnder interferometer (MZI) to further enhance the sensitivity of the relevant parameter estimations. The configuration is formed by two one-dimensional waveguides coupled sequentially to two atomic mirrors, which are served as the beam splitters of the waveguide photons to control the probabilities of the photons being transferred from one waveguide to another. Due to the quantum interference of the waveguide photons, the acquired phase of the photons when they pass through a phase shifter can be sensitively estimated by measuring either the transmitted or reflected probabilities of the transporting photons. Interestingly, we show that, with the proposed waveguide MZI the sensitivity of the quantum parameter estimation could be further optimized, compared with the waveguide FPI, in the same condition. The feasibility of the proposal, with the current atom-waveguide integrated technique, is also discussed.

Sensitive Evanescence-Field Waveguide Interferometer for Aqueous Nitro-Explosive Sensing

The development of novel chemical nitro-explosive sensors with high sensitivity, low cost and a compact size is essential for homeland security, environmental protection and addressing military challenges. Polymeric optical waveguides based on refractive index sensing are widely used in biochemical detection due to their advantages of large-scale integration, low cost, high sensitivity and anti-electromagnetic interference. In this study, we designed and fabricated a polymer waveguide Mach–Zehnder interferometer (MZI) sensor to detect 2,4-dinitrotoluene (DNT) in water. One phase shifter of the MZI waveguide was functionalized by coating a thin cladding layer of polycarbonate with dipolar chromophores and used as the sensing arm; the other arm was coated with passive epoxy resin cladding and used as the reference arm. The phase difference between the two arms of the MZI was modulated using the refractive index (RI) change in the polycarbonate cladding when dipolar chromophores interacted with electro-deficient DNT. The theoretical sensitivity of the designed MZI can reach up to 24,696 nm/RIU. When used for explosive detection, our fabricated sensor had a maximum wavelength shift of 4.465 nm and good linear relation, with an R2 of 0.96 between the wavelength shift and a concentration ranging from 3.5 × 10−5 to 6.3 × 10−4 mol/L. The sensitivity of our device was 6821.6 nm/(mol/L). The design of an unbalanced MZI sensor, together with the sensing material, provides a new approach to using low-cost, compact and highly sensitive devices for in-field explosive detection.

Low-power all-optical switch based on a graphene-buried polymer waveguide Mach-Zehnder interferometer.

We propose a low-power all-optical switch based on the structure of a graphene-buried balanced Mach-Zehnder interferometer (MZI), where the signal light is switched between the two output ports of the MZI by the heat generated from graphene's absorption of the pump light. We use orthogonal polarizations for the pump and the signal light to maximize pump absorption and minimize graphene-induced signal loss. Our experimental device fabricated with polymer waveguides buried with 5-mm long graphene shows a pump absorption of 10.6 dB (at 980 nm) and a graphene-induced signal loss of 1.1 dB (at 1550 nm) and can switch the signal light with a pump power of 6.0 mW at an extinction ratio of 36 dB. The actual pump power absorbed by graphene for activating switching is estimated to be 2.2 mW. The rise and fall times of the switch are 1.0 and 2.7 ms, respectively. The switching characteristics are weakly sensitive to ambient temperature variations. Our device can be butt-coupled to single-mode fibers and could find applications in fiber-based and on-chip all-optical signal processing.

A 100 Gbaud On-off-Keying Silicon-Polymer Hybrid Modulator Operating at up to 110°C

We demonstrate 100-Gbaud on-off-keying (OOK) transmission driven at a low voltage using an electro-optic (EO) polymer modulator combined with a silicon Mach-Zehnder interferometer waveguide. Various types of organic- and polymer-based modulators have been reported to perform efficient EO modulation and high-speed data transmission at over 100 Gbaud. However, there are critical concerns regarding the practical application of polymer devices in terms of environmental stability. In particular, long-term thermal storage and stability during operation require improvements before EO polymer modulators can be applied in practical systems. We have developed an EO polymer with enhanced thermophysical stability and used it to fabricate an efficient EO polymer modulator. In this study we extend our earlier work on high-speed EO polymer modulators by performing fiber-link 100-Gbaud OOK transmission at various operating temperatures. A thermal stability test revealed that the EO polymer modulator can survive high-temperature exposure up to 110°C. Error-free signal transmissions over a distance of 2.0 km was successfully demonstrated with a driving voltage of 1.9 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> and a bit error rate below the 7% overhead forward error correction threshold. The driving voltage, bandwidth, bit error rate, and fiber-link performance of the device are presented.

Waveguide Mach-Zehnder biosensor with laser diode pumped integrated single-mode silicon nitride organic hybrid solid-state laser

Single-mode organic solid-state lasers with direct emission into an optical waveguide are attractive candidates for cost-efficient coherent light sources employed in photonic lab-on-a-chip biosensors. Here, we present a combination of a dye-doped organic solid-state distributed feedback laser with a highly sensitive optical waveguide Mach-Zehnder interferometer on a silicon nitride photonic platform. This organic-hybrid laser allows for optical pumping with a laser diode in an alignment tolerant manner, which facilitates applications in point-of-care diagnostics. The sensitivity to bulk refractive index changes and the concentration dependent binding of streptavidin on a polyethyleneimine-biotin functionalized surface was studied to demonstrate the practicability of this cost-efficient coherent light source for optical waveguide biosensors.

Terahertz Spoof Surface Plasmonic Logic Gates.

SummaryLogic gates are important components in integrated photonic circuitry. Here, a series of logic gates to achieve fundamental logic operations based on linear interference in spoof surface plasmon polariton waveguides are demonstrated at terahertz frequencies. A metasurface-based plasmonic source is adopted to couple free-space terahertz radiation into surface waves, followed by a funnel-shaped metasurface to efficiently couple the surface waves to the waveguides built on a domino structure. A single Mach-Zehnder waveguide interferometer can work as logic gates for four logic functions: AND, NOT, OR, and XOR. By cascading two such interferometers, NAND and NOR operations can also be achieved. Experimental investigations are supported by numerical simulations, and good agreement is obtained. The logic gates have compact sizes and high intensity contrasts for the output “1” and “0” states. More complicated functions can be envisioned and will be of great value for future terahertz integrated computing.

All-in-fiber multiscan Mach-Zehnder interferometer assisted by core FBG for simultaneous multi-parameter sensing

In this work, a hybrid cladding waveguide (CWG) Mach-Zehnder interferometer (MZI) sensor inscribed by femtosecond laser is demonstrated. The CWG has been inscribed using adaptive optics and multiscan technique. It has been discovered that these waveguides exhibit a phase change dependent of the number of scans performed, allowing free spectral range (FSR) control. Temperature characterization reveals a refractive index change (RIC) proportional and lower than previously reported CWG MZIs, indicating a lower degradation with high temperatures. The CWG proximity to the cladding/air boundary allows good refractive index (RI) sensitivity. Thanks to the FBG inscribed in the reference arm with the point-by-point (PbP) technique, the interferometer can measure curvature and strain simultaneously without being affected by cross-sensitivity.

Study of an integrated optical waveguide sensor with a tapered antenna for measurement of intense pulsed electric field

A lithium niobate (LiNbO3, LN) integrated optical electric field sensor fused with an optical waveguide Mach-Zehnder interferometer (MZI), a tapered antenna and a parallel electrode is analysed, fabricated and experimentally demonstrated. Theoretical calculation reveal that the half-wave electric field is extensively (≈123%) influenced by the electrode gap but is slightly (≈2%) influenced by the electrode length. Experiment results demonstrate that the linear dynamic range of sensor1 (Lel=5 mm) and sensor2 (Lel= 1 mm) are 29 dB (5 −140 kV/m) and 20 dB (15−150 kV/m) respectively. Both the theoretical calculations and experiment results investigate that it is possible to improve the sensitivity while keep the maximum detectable electric field remains almost the same by deigning the sensor with longer electrode, which results a larger linear measureable dynamic range.

Design of an on-chip Fourier transform spectrometer based on waveguide Mach–Zehnder Interferometer and fluidics

An on-chip Fourier transform spectrometer based on the semiconductor waveguide Mach–Zehnder Interferometer (MZI) is proposed. The MZI is constructed by rectangular silicon-on-insulate waveguides. With the help of digital microfluidics, the sensing arm of MZI can be covered by liquid step-by-step, and as a result, the output of the MZI can be modulated accordingly. The length of the MZI arm is 3 mm for a theoretical demonstration. This spectrometer works well in the wavelength range of 1.5 μm to 1.7 μm with the spectral resolution reaching up to 3.1 nm. The performance can be further improved by extending the MZI arms along with the liquid channel.

Refractive index sensing based on Mach–Zehnder interferometer with a hybrid silica/polymer waveguide

Abstract We propose a refractive index sensing structure based on Mach–Zehnder interferometer (MZI) with a hybrid silica/polymer waveguide. Due to the thermo-optic (TO) effects of polymer and silica, the refractive index of sample can be measure by an integrated circuit. We discuss the design principle of the refractive index sensing waveguide and give its equivalent circuit to explain the sensing process. The sensitivity of MZI waveguide achieves 5556 °C/RIU which has a compact size of 10 μm × 6 mm. The sensing structure can be applied in a highly compact biosensing system and possess a great potential in point-of-care diagnostics and healthcare applications.

Synthesis and characterization of electro-optic waveguide material polyurethane-imides

The electro-optic (EO) polymers of Y-type polyurethane-imides (PUI-1 and PUI-2) were synthesized by reaction of monomer azo-based chromophores, phenyl diisocyanate and aromatic dianhydride, based on polycondensation mechanism. Molecular structure characteristics for the polymers were evidenced by 1HNMR, FTIR, elemental analysis and gel permeation chromatography. The polymers exhibited a glass transition temperature (Tg) of 185 °C and 192 °C and a temperature of 5% weight loss at 256 °C and 325 °C and showed EO coefficient, γ33, of 43 pm/V and 51 pm/V at 1550 nm wavelength. A type of single-mode embedded PUI polymeric inverted rib waveguide Mach-Zehnder (MZ) interferometer electro-optic modulators was fabricated and measured, and exhibiting favorable electro-optical modulation response and the average propagation loss of the waveguide was less than 2.0 dB/cm at 1550 nm. The experimental results indicated that the PUI were promising candidates for the preparation of comprehensive performance excellent EO polymer waveguide materials, due to their large nonlinear optic effects, thermal stability, good processability and low optical propagation loss.

Design and fabrication of reconfigurable laser-written waveguide circuits

Reconfigurability is an important requirement for implementing quantum photonic processing using waveguide circuits in which both high fidelity and the ability to change the optical transformation dynamically are necessary. This work aims to address the issue of scalability in reconfigurable waveguide circuits fabricated using the femtosecond laser direct-write (FLDW) technique. A set of reconfigurable waveguide Mach-Zehnder interferometers were designed and fabricated using a combination of femtosecond laser waveguide inscription and picosecond laser ablation. Thermal cross-talk between adjacent phase-shifters was managed by machining microchannels into the chip surface to isolate individual waveguides from the rest of the substrate. The tuning efficiency as defined by the dissipated power per unit of induced phase shift was improved by a factor of two in this way while maintaining a smaller device footprint than previous demonstrations of phase tuning in laser-written waveguides. The phase response of the waveguide interferometers to the heaters was thoroughly characterised and was well predicted by simulation. A characterization of the time-dependent response of the reconfigurable interferometers was also performed. A rise time measurement revealed that the circuit can be reconfigured within seconds. No long-term phase drifts away from a set point were observed over a period of more than 12 hours, and the short term phase stability was better than 6 mrad.

Broadband mode switch based on a three-dimensional waveguide Mach-Zehnder interferometer.

We propose a mode switch that operates on modulating the optical phases of a three-dimensional balanced four-arm waveguide Mach-Zehnder interferometer. We design and fabricate the device with polymer material to achieve thermo-optic switching between any two of the E11, E21, E12, and E22 modes of the waveguide. Our experimental device shows an extinction ratio higher than 14dB and a switching time shorter than 3.7ms, measured with the E11 mode switched to any of the other modes at 1550nm. This mode switch can operate over a wide range of wavelengths with weak polarization dependence and could be used in reconfigurable fiber-based mode-division-multiplexing systems where mode routing is required.

An integrated electro-optic magnetic field sensor based on reflected Mach-Zehnder interferometer

An optical magnetic field sensor using reflective Lithium niobate (LiNbO3) integrated optical waveguide Mach-Zehnder interferometer (MZI) has been proposed, designed and fabricated. The bare chip size of the sensor is microminiaturized as small as 20×5×0.5mm3. Experiment results reveal that the sensor has wide frequency response from 10MHz to 2GHz with variation less than ±3.3dB. Besides, the input/output of the sensor exhibit linear relationship as the magnetic field varied from 69.4 dBμA/m to 129.4 dBμA/m. The minimum detectable magnetic field is 65.4 dBμA/m and the dynamic range of the sensor is more than 60dB.

All polymer asymmetric Mach–Zehnder interferometer waveguide sensor by imprinting bonding and laser polishing**Project supported by the National Natural Science Foundation of China (Grant Nos. 61605057, 61475061, and 61575076), the Science and Technology Development Plan of Jilin Province, China (Grant No. 20140519006JH), and the Excellent Youth Foundation of Jilin Province, China (Grant No. 20170520158JH).

We present an all polymer asymmetric Mach–Zehnder interferometer (AMZI) waveguide sensor based on imprinting bonding and laser polishing method. The fabrication methods are compatible with high accuracy waveguide sensing structure. The rectangle waveguide structure of this sensor has three sensing surfaces contacting the test media, and its sensing accuracy can be increased 5 times compared with that of one surface sensing structure. An AMZI device structure is designed. The single mode condition, the length of the sensing arm, and the length deviation between the sensing arm and the reference arm are optimized. The length deviation is optimized to be in a refractive index range between 1.470 and 1.545. We fabricate the AMZI waveguide by lithography and wet etching method. The imprinting bonding and laser polishing method is proposed and investigated. The insertion loss is between −80.36 dB and −10.63 dB. The average and linear sensitivity are 768.1 dB/RIU and 548.95 dB/RIU, respectively. And the average and linear detection resolution of the sensor are 1.30 × 10−6 RIU (RIU: refractive index unit) and 1.82 × 10−5 RIU, respectively. This sensor has a fast and cost-effective fabrication process which can be used in the cases of requiring portability and disposability.