Optical Output Signal Research Articles

Increase of Recognizable Label Number with Optical Passive Waveguide Circuits for Recognition of Encoded 4- and 8-Bit BPSK Labels

Optical label processing is expected to reduce power consumption in label switching network nodes. Previously, we proposed passive waveguide circuits for the recognition of BPSK labels with a theoretically infinite contrast ratio. The recognizable label number was limited to four and eight for 4-bit and 8-bit BPSK labels, respectively. In this paper, we propose methods to increase the recognizable label number. The proposed circuits can recognize eight and sixteen labels of 4-bit BPSK codes with a contrast ratio of 4.00 and 2.78, respectively. As 8-bit BSPK codes, 64, 128, and 256 labels can be recognized with a contrast ratio of 4.00, 2.78, and 1.65, respectively. In recognition of all encoded labels, that is, 16 and 256 labels for 4-bit and 8-bit BPSK labels, a reference signal is employed to identify the sign of the optical output signals. The effect of phase deviation and loss along the optical waveguides of the devices is also discussed.

Viability assessment of bacteria using long-range surface plasmon waveguide biosensors

We demonstrate that long-range surface plasmon waveguide biosensors are useful to monitor the quiver of immobilized live bacteria in buffer and in human urine. First, the biosensor captures bacteria selectively, based on gram, using antibodies against gram adsorbed on the surface of the waveguide through Protein G coupling. Then, analysis of the noise present on the optical output signal reveals quiver of bacteria immobilized on the waveguide. Live bacteria produce a noisy signature compared to baseline levels. The standard deviation over time of the optical power output from the biosensor increased by factors of 3–60 over that of the baseline level for Staphylococcus epidermidis and Escherichia coli immobilized selectively on waveguides.

Anthraquinone-biimidazole based ruthenium(II) complexes as selective multichannel anion sensors and multi-readout molecular logic gates and memory devices: Combined experimental and DFT/TD-DFT study

In this work we will report anion sensing properties as well as multiple Boolean logic operations of recently reported Ru(II) complexes based on a biimidazole-anthraquinone ligand (Anq-BiimzH2). Covalent linking of electron accepting 9,10-anthraquinone moiety to the biimidazole unit followed by its coordination to Ru(II) center, leads to enhance the acidity of the imidazole NH protons in coordinated Anq-BiimzH2. Two NH protons which adopt a syn conformation in the complexes can be utilized for sensing of selective anions either via hydrogen bonding interaction or by complete proton transfer. The anion sensing studies of the complexes were thoroughly investigated in both organic and pure aqueous media through multiple channels viz. absorption, steady state and time-resolved emission, and 1H NMR spectroscopic techniques as well as by cyclic and square wave voltammetry. The complexes behave as highly sensitive sensors for F−, AcO−, CN−, and to some extent for H2PO4− in acetonitrile without much selectivity. In contrast to acetonitrile, the complexes posses high sensitivity and selectivity towards CN− even in presence of excess of other studied anions in water with detection limit lying in the range between 5.24×10−7 and 6.67×10−7M, making them useful for practical application. By utilizing the optical output signals upon interaction with a particular set of anions (F−, CN−, AcO− and OH−) and H+, the functions of two-inputs INHIBIT and IMPLICATION logic gates as well as three inputs NOR logic gate have been nicely demonstrated. More importantly, the complicated function of memory device was also mimicked by the complexes. Computational investigation with the help of density functional theory (DFT) and time-dependent density functional theory (TD-DFT) were performed to understand and interpret the experimentally observed optical properties of the complexes. Moreover, the experimental trend of the red-shifts of absorption and emission bands upon successive deprotonation of the complexes in presence of selective anions was nicely reproduced by calculations.

ChemInform Abstract: Selective Molecular Recognition on Calixarene‐Functionalized 3D Surfaces

AbstractReview: 68 refs.

Sensitivity Limit of Nanoparticle Biosensors in the Discrimination of Single Nucleotide Polymorphism

Detection of single nucleotide polymorphism (SNP) by selective aggregation of nanoparticles offers a rapid determination of cancer biomarkers, detectable by the naked eye. The main factor limiting the sensitivity of such colloidal sensors is the number of available target DNA molecules that can induce aggregation and thereby transduce an optical output signal. Although particle size is an obvious parameter of choice toward the modulation of the target-to-particle ratio at constant metal concentration, it is often omitted due to difficulties in the synthesis of particles with suitable size or to the limited colloidal stability of large particles stabilized with DNA. We present here a systematic study of SNP detection using gold nanoparticles of various sizes (13, 46, and 63 nm), using a conventional sandwich assay. We found that a 5-fold increase in particle size, at constant gold concentration, leads to an improvement in the limit of detection by 3 orders of magnitude, which is 5, 0.1, and 0.05 nM for 13,...

A simulated colorimetric INHIBIT logic gate based on 2-(2-thiazolylazo)-p-cresol

ABSTRACT2-(2-Thiazolylazo)-p-cresol system achieved distinct optical output signal by controlling pH and mercury-ion complexation. The 2-(2-thiazolylazo)-p-cresol with mercury ion existed as an equilibrium mixture of both an azo and hydrazone tautomeric forms at 372 and 425 nm, respectively, along with the appearance of a new absorption peak at 610 nm (visual color of green), which was attributed to the binding of mercury ion with 2-(2-thiazolylazo)-p-cresol. Furthermore, the addition of proton led to the perturbation of the conjugation between 2-(2-thiazolylazo)-p-cresol and mercury ion and absence of absorption at 610 nm (visual color of yellow). 2-(2-thiazolylazo)-p-cresol could thus be applied to develop an effective simulated colorimetric INHIBIT logic gate with mercury ion and proton as inputs. Consequently, green color with the absorption peak at 610 nm was outputted from yellow color of 2-(2-thiazolylazo)-p-cresol in the presence of mercury ion as an input signal at pH 7.0.

Magnetoplasmonic RF mixing and nonlinear frequency generation

We present the design of a magnetoplasmonic Mach-Zehnder interferometer (MZI) modulator facilitating radio-frequency (RF) mixing and nonlinear frequency generation. This is achieved by forming the MZI arms from long-range dielectric-loaded plasmonic waveguides containing bismuth-substituted yttrium iron garnet (Bi:YIG). The magnetization of the Bi:YIG can be driven in the nonlinear regime by RF magnetic fields produced around adjacent transmission lines. Correspondingly, the nonlinear temporal dynamics of the transverse magnetization component are mapped onto the nonreciprocal phase shift in the MZI arms, and onto the output optical intensity signal. We show that this tunable mechanism can generate harmonics, frequency splitting, and frequency down-conversion with a single RF excitation, as well as RF mixing when driven by two RF signals. This magnetoplasmonic component can reduce the number of electrical sources required to generate distinct optical modulation frequencies and is anticipated to satisfy important applications in integrated optics.

Design and optimization of novel two inputs optical logic gates (NOT, AND, OR and NOR) based on single commercial TW-SOA operating at 40 Gbit/s

This work demonstrates and optimizes novel simple design of two inputs all optical logic gates (NOT, AND, OR and NOR) using cross gain modulation technique at 40 Gbit/s. The proposed scheme differs from the previous conventional systems as utilizing only one commercial traveling wave-semiconductor optical amplifier (TW-SOA) and detuning optical band pass filter in order to select the appropriate output rather than using more than one SOA in addition to erbium-doped fiber amplifiers. This scheme overcomes the main problem appeared in the conventional schemes that suffer from the amplified spontaneous emission which considered as an additional noise that degrades output optical signal to noise ratio. Optimization process was done to achieve remarkable BER, Q-factor and acceptable extinction ratio at relatively low pumping powers while maintaining the simple design setup. A clear eye diagram for the all proposed optical logic gates is displayed. No obvious power penalty is observed for overall system.

Measuring absorption coefficient of scattering liquids using a tube inside an integrating sphere.

A method for measuring the absorption coefficient μa of absorbing and scattering liquid samples is presented. The sample is injected into a small transparent tube mounted through an integrating sphere. Two models for determining the absorption coefficient using the relative optical output signal are described and validated using aqueous ink absorbers of 0.5 vol.% (0.3 mm-1<μa<1.55 mm-1) and 1.0 vol.% (1.0 mm-1<μa<4.0 mm-1) concentrations with 1 vol.% (μs'≈1.4 mm-1) and 10 vol.% (μs'≈14 mm-1) Intralipid dilutions. The low concentrations give μa and μs values, which are comparable with those of biological tissues. One model assumes a uniform light distribution within the sample, which is valid for low absorption. Another model considers light attenuation that obeys Lambert-Beer's law, which may be used for relatively high absorption. Measurements with low and high scattering samples are done for the wavelength range of 400-900 nm. Measured spectra of purely absorbing samples are within 15% agreement with measurements using standard transmission spectrophotometry. For 0.5 vol.% ink absorbers and at wavelengths below 700 nm, measured μa values are higher for samples with low scattering and lower for those with high scattering. At wavelengths above 700 nm, measured μa values do not vary significantly with amount of scattering. For 1.0 vol.% ink absorbers, measured spectra do not change with low scattering. These results indicate that the method can be used for measuring absorption spectra of scattering liquid samples with optical properties similar to biological absorbers, particularly at wavelengths above 700 nm, which is difficult to accomplish with standard transmission spectrophotometry.

Selectable dual-wavelength erbium-doped fiber laser with stable single-longitudinal-mode utilizing eye-type compound-ring configuration

In this paper, a tunable dual-wavelength erbium-doped fiber (EDF) ring laser with stable single-longitudinal-mode (SLM) under a tuning range of 1530.0–1560.0nm is proposed and demonstrated. Here, the mode spacing of lasing dual-wavelength from 1.0 to 30.0nm can be selected arbitrarily in any wavelength position. To accomplish the SLM output, the eye-type compound-ring scheme is proposed inside ring cavity for suppressing the multi-longitudinal-mode (MLM) highly. The entire measured output power and optical signal to noise ratio (OSNR) of each dual-wavelength are larger than −13.3dBm and 60dB respectively. In addition, the output stability measurement of proposed EDF laser is also performed and analyzed.

Selective molecular recognition on calixarene-functionalized 3D surfaces.

Host-guest recognition plays an important role in biological analysis and biosensing. Accordingly, great efforts have been devoted to the development of sensors using versatile 3D surface materials. These functionalized nanomaterials possess the advantages of high selectivity and visual signals, enabling the selective detection of ions, amino acids, proteins, and other biological molecules. Therefore, in this feature article, we present some significant and representative examples of molecular recognition on calixarene functionalized 3D surface nanomaterials. By virtue of host-guest interactions, the functional interfaces displaying high selectivity and featuring a reversible switch response towards the environmental stimuli with various signal output (electrochemical and optical signals) are herein introduced. Furthermore, various 3D surface materials with unique signal amplification in molecular recognition are presented, including quantum dots (QDs), metal nanoparticles (NPs), nanotubes, and mesoporous silica. These excellent properties enable calixarene-functionalized 3D materials to become an outstanding platform for molecular recognition, offering convenient approaches for sensing and separation.

Sol–gel based fiber optic pH nanosensor: Structural and sensing properties

Evanescent wave absorption based PCS (plastic clad silica) fiber optic pH sensor is constructed by encapsulation of indicator dyes in the heterogeneous inorganic hybrid silica–titania nanomatrix in the presence of cetyl trimethyl ammonium bromide (CTAB) surfactant by sol–gel method. A nanoporous multilayers (triple layer and six layers) of silica–titania hybrid is deposited on 5cm uncladed middle portion of the fiber by dip-coating sol–gel technique. The CTAB surfactant expressively improved the host matrix structure and enhanced its porosity. Thermally stable, adhesive and smooth thin nanocladding has been examined using microscopic and thermal analysis. Indicators encapsulated nanomatrices are highly sensitive to pH and show optical output signals in terms of intensity. Therefore, it provides confirmation that interactions between the host matrix and pH-indicator molecules are in good assistance. Furthermore, experimental findings reveal that the sensing species are probably better encapsulated in the matrix and show no leaching of sensing molecules. The prepared nanosensors exhibit a much faster response time because of the material to be sensed diffuses faster into the triple-layer sensors <2s. These pH sensors are found to have 60 days (2 months) age stability and high reproducibility. A repeatable response over a wide range of pH values between 3 and 11 is obtained.

Lipidic Cubic Phases as a Versatile Platform for the Rapid Detection of Biomarkers, Viruses, Bacteria, and Parasites

Rapid and affordable detection of analytes is critical in diagnostic technologies, but current methods are typically expensive and unsuitable for field detection. Lipidic cubic phases are optically isotropic, transparent lyotropic liquid crystals (LC), containing highly confined water nanochannels in‐between percolating lipid bilayers following defined space groups. Due to this nanoconfinement, the water in these systems provides a unique environment for chemical and enzymatic reactions. Here, it is shown that during the in meso peroxidase enzymatic reaction, the converted product crystallizes within the mesophase domains, generating a detectable birefringence signal and a new general assay principle is presented for the detection of an unprecedented vast class of analytes using such birefringence as sole optical output signal. By exploiting bienzymatic cascade reactions or introducing an enzyme‐linked immunosorbent assay based on birefringence (Birefringent‐ELISA), this approach is used for real‐time detection of exemplary analytes, such as glucose and cholesterol, model pathogenic microorganisms, Escherichia coli, and viruses such as Ebola and HIV. It is also shown how the same technology enables the rapid, naked‐eye screening of malaria infection via in meso detection of hemozoin crystallites. This new technology is general and readily adaptable to the rapid detection of virtually any type of analyte, such as disease biomarkers, viruses, bacteria, and parasites.

Optical emission monitoring for defocusing laser percussion drilling

This paper presents a novel method for controlling the laser-drilling process for a hole by monitoring induced plasma emission. The variation of light brightness from laser-induced plasma is used as an indicator to control laser percussion drilling. Through on-line plasma emission acquisition and analysis, we obtain the positive association between the increased depth and the optical signal output. A coaxial photodiode is used to estimate the brightness levels of laser-induced plasma. The above constitute an inexpensive and practical on-line feedback system that can be easily implemented in the laser systems. All of the processing work is performed in air under standard atmospheric conditions without gas assist. The acquired signal for drilling could also be used as an input to a focus point process control scheme. Moreover, the technology demonstrates the feasibility to develop an automated laser micromachining system. Experimental results show that drilling efficiency was increased 47% by applying the proposed defocusing laser percussion drilling.

A wideband photonic microwave phase shifter using polarization-dependent intensity modulation

We present a tunable and wideband microwave photonic phase shifter based on polarization-dependence of the LiNbO3 Mach–Zehender modulator (MZM). In the proposed device, an orthogonal single sideband modulation is implemented by using a MZM and an optical band-pass filter. With the polarizer to synthesize the polarization orthogonal optical carrier and sideband, the phase of the optical microwave signal output from the polarizer can be tuned from 0 to 360° by simply adjusting the polarization direction of the lights whereas the amplitude keeps constant. A full range tunable phase shifting in the frequency range of 10–35GHz is achieved.

Micron scale directional coupler as a transducer for biochemical sensing.

A microfabricated directional coupler (DC) was used for the detection of DNA conjugated with quantum dots. Output optical signals from DCs of a wide range of device lengths correspond well to theoretical and simulation results. Even 20 µm-long DC devices could detect changes in the output optical intensity by monitoring the near-field pattern using a CCD camera. The signal was enhanced 60 × using a 1500 µm-long DC device. For large cladding refractive-index changes between air and water, the normalized signal changed cyclically several times between 0 and 1. The results suggest that the DC can be the basis for miniaturized two-dimensionally integrated biochemical sensors.

Noise Suppression Phenomenon in Fiber Raman Amplifier

Abstract The problem of small bit error rate is actual in fiber Raman amplifiers. Our experimental data on the amplified spontaneous emission (ASE) with backward pumping as a base of optical noise evaluation are presented in this paper. Raman gain spectrum for useful Stokes low-powered signal is calculated and compared with obtained spectrum of non-coherent ASE noise. It is shown that output optical signal has better gain than the amplified spontaneous emission that leads to appreciable growth of output optical signal-to-noise ratio.

Metamorphosis of the transistor into a laser

Based on the invention and operation of the transistor, the alloy diode laser, the quantum-well diode laser and the high-speed heterojunction bipolar transistor (HBT), we have invented and realized now a transistor laser (TL). The transistor laser is a three-terminal technology providing coupling and the coherent light emission in the transistor. The quantum-well (QW) heterojunction bipolar transistor laser, inherently a fast switching device, operates by transporting a small minority base charge density over a nanoscale base thickness in picoseconds. The TL, owing to its fast recombination speed, its unique three-terminal configuration, and complementary nature of its optical and electrical collector output signals, enables resonance-free base current and collector voltage modulation. It is a compact source of electro-optical applications such as nonlinear signal mixing, frequency multiplication, negative feedback, and optoelectronics logic gates.

G0500105 単一光ファイバープローブを用いた泡沫群中における膜間距離および膜厚の計測

Foam is encountered in many industrial fields and affects safety and efficiency of floatation, wastewater treatment, and so on. However, the conventional foam measurement techniques measure only an average foam diameter near a transparent wall. Hence, we propose a new technique to measure dense foam through a single-tip optical fiber probe (S-TOP). In past study, we analyzed optical output signals when the S-TOP pierced two parallel thin films via experiments and computations. In this study, we measured a small foam cluster using the S-TOP and visualized the experiment through a high speed video camera. Based on this, we established a new system to measure both foam sizes and thickness. The measurement error was ±10 %.

On-line depth measurement for laser-drilled holes based on the intensity of plasma emission

The direct time-resolved depth measurement of blind holes is extremely difficult due to the short time interval and the limited space inside the hole. This work presents a method that involves on-line plasma emission acquisition and analysis to obtain correlations between the machining processes and the optical signal output. Given that the depths of laser-machined holes can be estimated on-line using a coaxial photodiode, this was employed in our inspection system. Our experiments were conducted in air under normal atmospheric conditions without gas assist. The intensity of radiation emitted from the vaporized material was found to correlate with the depth of the hole. The results indicate that the estimated depths of the laser-drilled holes were inversely proportional to the maximum plasma light emission measured for a given laser pulse number.