Interferometer Configuration Research Articles

Optical-fiber ring cavity with saturable rare-earth-doped fiber

Resonance properties of the all-fiber ring cavity filled with nonlinear material - saturable rare-earth-doped fiber are analyzed and experimentally investigated. Unlike the earlier investigated erbium-doped fiber at 1550nm where the optical absorption photo-induced change (saturation) is observed only, the ytterbium-doped fiber at 1064nm demonstrates the saturation of the refractive index mainly. For this configuration we report experimental observation of the optical bistability and hysteresis in the transmitted output light at the 10mW-scale incident light power. The experimental results are in qualitative agreement with the theoretical analysis that takes into account the saturation of both parameters: the optical absorption and the refractive index of the doped fiber. The reported results seem promising for applications in high-sensitivity interferometric configurations at 1064nm operation wavelength.

Demonstration of a dual-pass differential Fabry–Perot interferometer for future interferometric space gravitational wave antennas

A dual-pass differential Fabry–Perot interferometer (DPDFPI) is one candidate of the interferometer configurations utilized in future Fabry–Perot type space gravitational wave antennas, such as Deci-hertz Interferometer Gravitational wave Observatory. In this paper, the working principle of the DPDFPI has been investigated and necessity to adjust the absolute length of the cavity for the operation of the DPDFPI has been found. In addition, using the 55 cm-long prototype, the operation of the DPDFPI has been demonstrated for the first time and it has been confirmed that the adjustment of the absolute arm length reduces the cavity detuning as expected. This work provides the proof of concept of the DPDFPI for application to the future Fabry–Perot type space gravitational wave antennas.

Design and analysis of all optical frequency encoded X-OR and X-NOR gate using quantum dot semiconductor optical amplifier-Mach Zehnder Interferometer

All optical frequency encoded logic gates XOR and XNOR are designed and simulated using quantum dot semiconductor optical amplifiers (QDSOA) at 1 Tb/s for the first time as far as our knowledge goes. The logic gates use Mach Zehnder Interferometer (MZI) configuration. Simulation of gain and phase dynamics of QDSOA is presented. The present paper investigates output bit patterns using MATLAB. Amplitude Modulation (AM) is calculated and found to be as low as 0.007 dB for unsaturated gain of 10 dB of the QDSOA. A maximum Quality factor 27 dB is calculated for 5mW control power. The paper also investigates the effect of QDSOA length on quality factor. In this paper, I have modified the definitions of AM and Quality Factor (Qfe) to apply in case of frequency encoded logic.

Visible Fourier transform absorption spectrum measurement method based on dual interferometer configuration

We introduce an absorption spectrum measurement method in the visible regime based on dual interferometer configuration. The proposed method can realize the measurement of the absorption spectrum by addition and calculation of the alternating current (AC) components of interferograms from dual symmetrical interferometers in one measurement, with no need to subtract twice-measured spectrum data with or without samples in the traditional single interferometer method, thus expanding the dynamic range of measurement, especially suitable for weak absorption. The absorption spectra of FB570-10 bandpass filter and NF533-17 notch filter measured by this method conform to the official data.

Simulation framework for activity recognition and benchmarking in different radar geometries

Radar micro-Doppler signatures have been proposed for human monitoring and activity classification for surveillance and outdoor security, as well as for ambient assisted living in healthcare-related applications. A known issue is the performance reduction when the target is moving tangentially to the line of sight of the radar. Multiple techniques have been proposed to address this, such as multistatic radar and to some extent, interferometric (IF) radar. A simulator is presented to generate synthetic data representative of eight radar systems (monostatic, circular multistatic and in-line multistatic [IM] and IF) to quantify classification performances as a function of aspect angles and deployment geometries. This simulator allows an unbiased performance evaluation of different radar systems. Six human activities are considered with signatures originating from motion-captured data of 14 different subjects. The classification performances are analysed as a function of aspect angles ranging from 0° to 90° per activity and overall. It demonstrates that IF configurations are more robust than IM configurations. However, IM performs better at angles below 55° before IF configurations take over.

Управляемый рефрактивный интерферометр Майкельсона

In some applications of a Michelson interferometer, in particular, when it is used in a laser resonator, the high stability of its phases is necessary. The proposed paper contains the comparison of two interferometer configurations. The first of them uses a classical schematic interferometer, the second one is designed with the use of a refractive schematic one, which is typical of enhanced stability against misalignments and occasional fluctuations of surrounding air. The possibility is discussed of applying the controllable refractive interferometer inside the resonator for generation of ultra short laser pulses.

All-optical ripple carry adder based on SOA-MZI configuration at 100 Gb/s

Ripple carry adders are broadly used for the addition of n-bit input sequences in arithmetic and logic units and for performing packet-header processing in all optical packet switched networks. In this paper, we have proposed the novel design of 2-bit ripple carry adder based on semi-conductor optical amplifier- Mach Zehnder Interferometer (SOA-MZI) configuration at 100Gb/s. The XOR, OR and AND gates have been employed as basic gates in the design of ripple carry adder. The four input signals of the adder circuit and the resultant outputs attained are at the same wavelength. The performance of the proposed device has been analyzed in terms of extinction ratio(ER), contrast ratio(CR), quality factor(QF) and amplitude modulation(AM) at the output.

Novel in situ sensing surface forces apparatus for measuring gold versus gold, hydrophobic, and biophysical interactions

The surface forces apparatus (SFA) was developed in the late 1960s as a powerful tool for investigating molecular interactions across apposing surfaces including the first measurement of van der Waals forces and interactions in biologic and liquid media. However, the SFA has two major disadvantages. First, it traditionally uses white light interference between back-silvered muscovite mica surfaces to measure distances and to infer forces from distance shifts during interaction of two surfaces. Hence, distance shifts and force measurement are not decoupled. Second, productive SFA interferometers are so far limited to measuring across mica versus mica or mica versus metal. Direct gold-gold configurations were suggested in the late 1990s but not experimentally achieved as proof-of-principle until recently using a templating technique. In this work, we show how we solve these two disadvantages. First, we present a new SFA design that decouples force and distance measurements with similar resolution. The presented SFA design is inexpensive and can be home-built with mostly commercially available parts. Second, we present an alternative physical vapor deposition approach to construct a stable gold-gold interferometer and demonstrate its performance showing hydrophobic interactions, bubble formation, hemifusion of bilayers, and friction experiments. The presented system is easy to use. The obtained results show excellent reproducibility, indicating that the designed SFA and the three-mirror gold-gold interferometer functions as well as or even better than the traditional interferometer configurations used in SFA. This opens SFA to a wide range of options for various possible applications. Specifically, the gold-gold configuration allows a broad range of surface modifications for studying biophysical interactions as demonstrated in this work.

Design and performance analysis of SOA-MZI-based Tbps all-optical gray converters with M-ary DPSK coded binary, gray, and octal inputs

We propose three different types of all-optical code converters with high data rates of 1 Tbps based on a semiconductor optical amplifier in Mach–Zehnder interferometer configuration. The gray code is a cyclic code, which is more suitable for accurate representation of numbers, error detection, correction, and rounding of decimal quantities. The OR and XOR logic gates are the key structures in the proposed design to convert binary inputs to gray (BITG), binary coded decimal (BCD) inputs to gray (BCDTG) and octal inputs to binary (OCTB) outputs. The output of proposed all-optical gray code converters is verified for all three types of input representations. The bit error rate is negligible for all the input combinations. The obtained average extinction ratio for all-optical code converters are 87, 84, and 78 dB. The optimum value of quality factor up to 59 is achieved at 0.1 A, ±5, and 0.3, respectively, for the injection current, linewidth enhancement factor, and optical confinement factor. For the first time to the authors’ knowledge, all-optical gray code converters yield high data rates of 1 Tbps for the semiconductor optical amplifier-Mach–Zehnder interferometer configurations using the M-ary differential phase-shift keying modulation scheme.

Deriving Digital Surface Models from Geocoded SAR Images and Back-Projection Tomography

Digital surface models (DSMs) are sets of elevation data of the Earth's surface, useful for applications such as urban studies and height estimation of buildings. They can be derived from a set of synthetic aperture radar (SAR) images acquired in an interferometric or tomographic configuration. Each image acquisition is usually focused in radar geometry. In this work, we present steps required to derive DSMs from SAR single-look complex (SLC) products focused in map geometry (geocoded). We modified existing tomographic reconstruction techniques to be able to operate with geocoded SLCs and extended methods to operate with 3-D geocoded SLCs. The performance analysis showed that methods using 3-D geocoded SLC products yielded DSMs with fewer outliers and retained more information of the illuminated area, with a cost of higher computational complexity. Compressive sensing methods using 2-D geocoded SLCs can be a good alternative due to their comparatively moderate computational complexity.

Design of All-Optical Half Adder and Half Subtractor based on SOA-MI

An all-optical half adder and half subtractor is proposed using Semiconductor Optical Amplifier assisted Michelson Interferometer (SOA-MI) configuration along with two similar Fiber Bragg Grating (FBG) at the end of the interferometric arms to satisfy the truth table of half adder and half subtractor. SOA acts as an amplifier without the need for conversion to electrical signals. The proposed model is designed using all-optical NOR gates with cross-gain modulation (XGM) of SOA at bit rate of 10Gbps. Analysis of performance factors which includes Bit Error Rate (BER), OSNR and Q-factor have been discussed.

Novel defocus hologram aberration compensation method in digital holography integrated pathology microscope for label free 3-D imaging

In this paper we report successful integration of digital holography in off- axis transmission configuration into a commercially available pathology microscope (PathologyDHM), where Mach-Zehnder interferometric configuration was achieved in pathology microscope using 1 × 2 single mode fiber coupler and custom built optical modules. A smartphone/webcam positioned at the image plane of the finite conjugate microscope captures the interference pattern generated by the system. Using PathologyDHM, we have demonstrated a novel and simple method for compensation of aberration due to microscope objective (MO). The proposed method is called defocus hologram method and it is particularly useful in cases, where samples do not have specimen free or background flat region. Proper validation of the method was done by imaging a transmissive grating (commercial compact disc, CD-R), which doesn't have a flat background region and comparing phase profile of CD-R computed by our proposed method with self-reference conjugated hologram method. For reiterating its biological applications, phase profile of a biological sample, red blood cell smear (RBC smear), was computed with our defocus hologram method and compared with already established reference conjugated hologram method. Phase profiles of CD-R and RBC smear computed with defocus hologram method agree with self-reference and reference conjugated hologram methods respectively, within the phase error limits of the system. Integration of digital holography in to commercial pathology microscope enables 3D imaging, which coupled with artificial intelligence may prove useful in disease diagnostics and monitoring response of cells to treatment.

Higher-order Hermite-Gauss modes as a robust flat beam in interferometric gravitational wave detectors

Higher-order Laguerre-Gauss (LG) modes have previously been investigated as a candidate for reducing test-mass thermal noise in ground-based gravitational-wave detectors like Advanced LIGO. It has been shown however that LG modes' fragility against mirror surface figure imperfections limits their compatibility with the current state-of-the-art test masses. In this paper we explore the alternative of using higher-order Hermite-Gauss (HG) modes for thermal noise reduction, and show that with the deliberate addition of astigmatism they are orders of magnitude more robust against mirror surface distortions than LG modes of equivalent order. We present simulations of Advanced LIGO-like arm cavities with realistic mirror figures which can support HG$_{33}$ modes with average arm losses and contrast defects in a Fabry-Perot Michelson interferometer configuration which are well below the typical measured values in Advanced LIGO. This demonstrates that the mirror surface flatness errors will not be a limiting factor for the use of these modes in future gravitational-wave detectors.

SOA-MZI based 4 × 4 interconnected crossbar photonic wavelength switching for datacenter load balancing

Our paper is focused on an extremely efficient structure for photonic crossbar switch using a fundamental building element, a semiconductor optical amplifier (SOA) in a Mach–Zehnder interferometer configuration. The switch is designed with a 10 Gbps rate and a high Q-factor of 30; a bit error rate ranging between ∼e − 122 and ∼e − 184 is achieved. In addition, the designed photonic switch model is reliable in terms of having an extinction ratio of 16 dB on average. High optical signal-to-noise ratio values, ranging between 101 and 104 dB, provide the low interference of noise in the required signals. It is observed that the proposed configuration is fast enough to provide a switching time ranging between 0.146 and 0.227 ns and is feasible in scaling the ports with an increase in the number of users to maintain a good quality factor. Hence, the proposed architecture can be taken as a solution for challenges in future datacenter network switching.

High-performance fiber-integrated multifunctional graphene-optoelectronic device with photoelectric detection and optic-phase modulation

In graphene-based optoelectronic devices, the ultraweak interaction between a light and monolayer graphene leads to low optical absorption and low responsivity for the photodetectors and relative high half-wave voltage for the phase modulator. Here, an integration of the monolayer graphene onto the side-polished optical fiber is demonstrated, which is capable of providing a cost-effective strategy to enhance the light–graphene interaction, allowing us to obtain a highly efficient optical absorption in graphene and achieve multifunctions: photodetection and optical phase modulation. As a photodetector, the device has ultrahigh responsivity ( 1.5 × 10 7 A / W ) and high external quantum efficiency ( > 1.2 × 10 9 % ). Additionally, the polybutadiene/polymethyl methacrylate (PMMA) film on the graphene can render the device an optical phase modulator through the large thermo-optic effect of the PMMA. As a phase modulator, the device has a relatively low half-wave voltage of 3 V with a 16 dB extinction ratio in Mach–Zehnder interferometer configuration.

Hybrid Silicon and Lithium Niobate Modulator

Hybrid Lithium Niobate (LN) and Silicon photonic (SiPh) integration platform has emerged as a promising candidate to combine the scalability of silicon photonics with the excellent modulation performance of LN. Mach-Zehnder modulators (MZMs) based on this platform exhibit outstanding performance with low insertion loss, low drive voltage, and large bandwidth. In this paper, we discuss the technologies for realizing hybrid LN/SiPh platform. The configuration and key metrics of LN/SiPh MZM are analyzed in detail. Furthermore, various functional devices derived from the Mach-Zehnder interferometer (MZI) configuration are also reviewed.

Flexible gauge length intrinsic fiber-optic strain sensor using broadband interferometry [Invited

Monitoring strain is important in precision engineering applications that require maintaining the precise alignments of structures over time, such as those found in machine tools and metrology frames. We present a fiber-optic strain measurement technique based upon broadband interferometry that is variously configurable in terms of gauge length and sensitivity. This is achieved by the use of an unbalanced interrogation interferometer configuration that alleviates the cavity length limit imposed by the temporal coherence of the system. We also demonstrate that dispersion in fiber sensors based on intrinsic Fabry-Perot interferometers must be considered to optimize performance. The possibility of multisensor interrogation using the same optical system is also reported.

Development of X-ray phase CT with a hybrid configuration of Lau and Talbot-Lau interferometers.

X-ray phase computed tomography (CT) is used to observe the inside of light materials. In this paper, we report a new study to develop and test a laboratory assembled X-ray phase CT system that comprises an X-ray Lau interferometer, a rotating Mo anode X-ray tube, and a detector with high spatial resolution. The system has a high spatial resolution lower than 10 μm, which is evaluated by differentiating neighbouring carbon fibres in a polymer composite material. The density resolution is approximately 0.035 g/cm3, which enables to successfully distinguish the high-density polyethylene (HDPE, 0.93 g/cm3) from the ultra-low-density polyethylene (ULDPE, 0.88 g/cm3) in the sample. Moreover, the system can be switched to operate on another mode based on a Talbot-Lau interferometer that provides a wider field of view with a moderate spatial resolution (approximately 100 μm). By analyzing sample images of the biological, this study demonstrates the feasibility and advantages of using hybrid configuration of this X-ray phase CT system.

Quantum Backaction on kg-Scale Mirrors: Observation of Radiation Pressure Noise in the Advanced Virgo Detector.

The quantum radiation pressure and the quantum shot noise in laser-interferometric gravitational wave detectors constitute a macroscopic manifestation of the Heisenberg inequality. If quantum shot noise can be easily observed, the observation of quantum radiation pressure noise has been elusive, so far, due to the technical noise competing with quantum effects. Here, we discuss the evidence of quantum radiation pressure noise in the Advanced Virgo gravitational wave detector. In our experiment, we inject squeezed vacuum states of light into the interferometer in order to manipulate the quantum backaction on the 42kg mirrors and observe the corresponding quantum noise driven displacement at frequencies between 30 and 70Hz. The experimental data, obtained in various interferometer configurations, is tested against the Advanced Virgo detector quantum noise model which confirmed the measured magnitude of quantum radiation pressure noise.

Nanophotonics for bacterial detection and antimicrobial susceptibility testing

Abstract Photonic biosensors are a major topic of research that continues to make exciting advances. Technology has now improved sufficiently for photonics to enter the realm of microbiology and to allow for the detection of individual bacteria. Here, we discuss the different nanophotonic modalities used in this context and highlight the opportunities they offer for studying bacteria. We critically review examples from the recent literature, starting with an overview of photonic devices for the detection of bacteria, followed by a specific analysis of photonic antimicrobial susceptibility tests. We show that the intrinsic advantage of matching the optical probed volume to that of a single, or a few, bacterial cell, affords improved sensitivity while providing additional insight into single-cell properties. We illustrate our argument by comparing traditional culture-based methods, which we term macroscopic, to microscopic free-space optics and nanoscopic guided-wave optics techniques. Particular attention is devoted to this last class by discussing structures such as photonic crystal cavities, plasmonic nanostructures and interferometric configurations. These structures and associated measurement modalities are assessed in terms of limit of detection, response time and ease of implementation. Existing challenges and issues yet to be addressed will be examined and critically discussed.