Improvement of optical sensing performances of a double-slot-waveguide-based ring resonator sensor on silicon-on-insulator platform

We demonstrate a label-free photonic biosensor with double slots based on micro-ring resonator. The footprint is less than 25 μm × 15 μm. Finite-difference time-domain (FDTD) method is used to analyze the influence of several key parameters on the performance of the double-slots micro-ring resonators. An asymmetric structure is considered for the ring waveguide in order to improve the sensor's bending efficiency. Our numerical analysis shows that the sensitivity of double-slot micro-ring resonator sensor with the radius of 5 μm reaches a value of 708 nm/RIU. The quality factor of 580 and the free spectral range (FSR) of 33 nm are achieved.     

Vertical input optical ring resonator with differential operation for optical sensor

A novel waveguide ring resonator optical sensor with two resonant wavelength channels is proposed for a refractive index measurement of a test sample placed on the sensor substrate and its performance characteristics are investigated analytically and numerically. The waveguide device consists of a ring resonator, a split-ring-shaped loop waveguide, and a vertical input/output grating coupler, in which the loop waveguide acts as an additional resonator and provides another output wavelength channel of the sensor. The differential detection between the two wavelength channels enables the highly sensitive detection with temperature compensation. A numerical simulation based on a finite difference time domain (FDTD) method shows that a precise index change detection with a resolution of 10⁻⁶ can be achieved using of the proposed device.     

Fiber ring laser for intracavity sensing using a whispering-gallery-mode resonator

Whispering-gallery-mode (WGM) microresonators are used as optical transducers for sensing applications. The typical detection scheme is based on tracking the WGM resonance shift, by scanning with a tunable laser, when a change of the refractive index in the region probed by the WGM takes place. We propose a sensing approach based instead on monitoring the position of the laser line of a fiber ring laser having a WGM microsphere in its loop. We have demonstrated that the induced shift is the same for the ring laser line and for the microsphere resonance. The proposed method requires simpler, cheaper equipment and may also improve the sensor resolution because the ring laser line is much narrower than the microsphere WGM resonance.     

Chaotic dynamics of active optical fiber ring resonator with optical injection

We experimentally obtain the route from period doubling to chaos in an active optical fiber ring resonator （AOFRR） with optical injection. The results show that the AOFRR is sensitive to external optical injection and demonstrate various dynamic characteristics. Meanwhile, the change of the injection strength can cause the output of the AOFRR to become periodic or chaotic. It can be confirmed that all the dynamic characteristics of the system are due to the interaction of the semiconductor laser with the erbium-doped fiber amplifier （EDFA）.     

Investigation and applications of all-fiber brillouin ring resonator lasers

We examine the theoretical and experimental behavior of Brillouin ring resonator lasers (BRRL), highlighting differences between Brillouin scattering in ring resonators and long fiber lengths. The theory, which assumes that the nonlinear interaction is welldescribed by two coupled equations for the optical waves, agrees well with measured data. We examine the single and multimode behavior of BRRL and show how this may be usefully implemented in microwave signal generation, in Stimulated Brillouin Scattering gain studies, and to realize a new form of all-fiber frequency shifter.     

A spectacles-shaped optical fibre ring resonator with two couplers

A theoretical study of a novel spectacles-shaped optical fibre ring resonator with double couplers has been carried out. The circulating, transmitted and reflected output fields and intensities have been computed and presented as graphs. The characteristics, advantages and possible applications of this ring resonator are discussed.     

Optical fiber ring resonator characterization by optical time-domain reflectometry

A novel method for characterization of optical fiber resonators by an optical time-domain reflectometry (OTDR) technique is reported. This easy-to-use technique yields accurate results for cavity lengths ranging from a few meters to several kilometers. A simple relationship is established between the round-trip cavity loss and the position where the OTDR signal is maximum. The value obtained for the round-trip cavity loss turns out to be quite insensitive to uncertainties in the determination of the OTDR maximum position.     

Resonance asymmetry phenomenon in waveguide-type optical ring resonator gyro

The intensity output of a silica waveguide ring resonator (WRR) was found to show an asymmetric resonance characteristic. To further analyze and better design the resonator micro optic gyro (RMOG) with a waveguide-type ring resonator, in-depth research of the characteristics of the resonance asymmetry is fully developed for the first time, to the best of our knowledge. Four possible sources of the resonance asymmetry are analyzed and their respective contributions are compared. These four error sources are differential normal mode losses in the coupler, the backscattering induced noises, the polarization fluctuations and the optical Kerr effect. The differential normal mode loss is suspected to be the major contributor to the observed resonance asymmetry in the fabricated silica WRR. Asymmetric resonance curve produces a large output bias error in the RMOG based on the phase modulation technique, which is related to the modulation frequency differences between the CW and CCW lightwaves. Theoretical analysis shows that replacing the reflector WRR with a transmitter one is helpful to eliminate the effect of the different normal mode losses in the coupler on the resonance asymmetry.     

Slotted microcavity ring resonators for optical storage applications

In this paper, slotted microcavity ring resonators based optical storage devices are proposed and analyzed by means of multiresolution time domain technique. The effect of the structure geometrical parameters on the coupling efficiency, normalized transmission spectra and quality factor has been thoroughly investigated and compared to that of the conventional no-slot microring resonator. The suggested slotted configurations increase the quality factor at a fixed gap size between the central ring and input/output waveguides. In addition, the desired compromise between the coupling efficiency and resonance effect inside the ring can be achieved by mere optimization of the slot geometrical characteristics.     

Analysis of resonance characteristics of solidly mounted resonator for mass sensing applications

Solidly mounted resonators (SMRs) have recently been adopted as alternatives to quartz crystal microbalance in bio-molecular and chemical detection field. In this study, the resonance characteristics of highly c-axis-textured AlN film-based SMR were investigated to obtain better sensitivity for mass sensing applications. The resonant frequencies and quality factors of SMR with different sizes and shapes of active resonant configuration were characterized. The results show that the effect of active resonant area on the resonance frequency is insignificant. However, the quality factor is strongly dependent on the size and shape of active resonant area. Optimized resonant patterns were applied to a 2.0 GHz SMR and mass sensor. Experimental results indicate that the sensitivity of the device achieved can be as high as 6,544 Hz cm²/ng, which shows the promising application in bio-molecular and industrial detecting application.     

Tunable optical filter based on Sagnac phase-shift using single optical ring resonator

In this paper, a single optical ring resonator connected to a Sagnac loop is used to demonstrate theoretically a novel narrow band optical filter response that is based on Sagnac phase-shift Δφ. The given filter structure permits the Sagnac rotation to control the filter response. It is shown that by changing the Sagnac rotation rate, we can tune the filter response for desired bandwidths. To increase the wavelength selectivity of the filter, the Sagnac phase-shift should be as small as possible that is limited by the loop length. For Δφ=0.1 rad, the obtained FWHM is 2.63 MHz for tuning loop length of 2 m. The simulation response agrees fairly with the recently reported experimental result.     

Nonlinear planar asymmetrical optical waveguides for sensing applications

This paper provides a theoretical analysis for TE polarized waves guided by a linear film surrounded by two asymmetrical nonlinear media for sensing applications. The sensitivity of the proposed sensor is derived. The conditions required for the sensor to exhibit its maximum sensitivity are presented. This analysis covers the case when the measurand is homogeneously distributed in the covering medium. We show that nonlinear sensors have sensitivities higher than those of linear sensors. The authors believe that optical sensing can be improved by introducing nonlinear waveguides.     

Dynamic behavior and complexity of modulated optical micro ring resonator

The dynamic behavior of an optical micro ring resonator (OMRR) with an amplitude modulator positioned in the micro ring is investigated quantitatively by adopting a recently introduced quantifier, the permutation entropy (PE). The effects of modulation depth are focused on, and the roles of input power are considered. The two-dimensional (2D) maps of PE showing dependence on both modulation depth and input power are presented as well. PE values nearly increase with modulation depth. On the other hand, the optimal value of input power is achieved when the PE reaches its maximum. Thus, PE can successfully quantify the dynamics of modulated OMRR. Selecting the parameters in the region with high PE values would contribute to the complexity-enhanced OMRR-based chaotic communication systems.     

Antiresonant guiding microstructured optical fibers for sensing applications

A novel refractometric sensor utilizing unique spectral properties of antiresonant-guiding microstructured optical fibers is proposed. The sensor operation is based on the wavelength shift of the transmission spectrum in response to the refractive index change of a sample loaded in the air-holes of the microstructured optical fiber. Refractive index changes on the order of 0.1% can be detected using less than a nanoliter of a sample.     

Entangled photon generation in a nonlinear microring resonator for birefringence-based sensing applications

This paper proposes a new concept of birefringence-based sensor using the entangled photon timing walk-off compensation. The superposition of nonlinear light known as four-wave mixing is introduced by the Kerr nonlinear effects type within the ring device. The possible two entangled photon pairs are randomly generated using the polarization control unit. Results obtained have shown that the entangled state walk-off of light traveling within the ring device can be compensated. This means the changes in walk-off parameters can be relatively measured to the changes in the applied physical parameters. The potential of using such a proposed system for birefringence-based sensor applications is plausible and discussed.     

Generalized optical filters using a nonlinear micro ring resonator system

We present the interesting results of nonlinear behaviors of a soliton pulse within a nonlinear micro ring resonator system, where the optical filter characteristics in terms of frequency, wavelength and time can be functioned by using the chaotic filter within the micro ring resonator system. There are three forms of applications using the chaotic soliton behaviors and optical filter characteristics presented. Firstly, the simultaneous up-link and down-link frequency bands can be filtered and the required frequency bands obtained. Secondly, we propose the simple system of an extremely narrow light pulse generation over the spectrum range, where the required wavelengths can be filtered and obtained. Finally, a simple system of fast light generation by using a soliton pulse circulating in the integrated micro ring devices is proposed. Using such a system, an attosecond pulse and beyond can be easily filtered and obtained.     

Bifurcation structures into chaos of delay-differential equations for a passive optical ring resonator

The delay-differential equation system describing the passive optical ring cavity is investigated. A survey of different bifurcation scenarios into chaos of the solutions on one branch and specific transitions between different branches of the multistable system are discussed. Precipitation via a heteroclinic cycle and crisis induced intermittency are found.     

A nano-scale transducer using a PANDA type ring resonator for gas sensor applications

We present a new system of nano-scale gas sensor using PANDA type ring resonator, whereas the sensing unit is a splitting ring resonator with two and four gaps. The method of finite difference time domain (FDTD) via the computer programming called Opti-wave was used to analyze and simulated all the parameters. The two systems were compared and the simulation result shown that the system of four splitting gaps is better resolution and more linear relationship than two splitting gaps unit. Finally, we found that this system can be used to be a high-precision self-calibration nano-scale gas sensor with in the of resolution of 1 nm.     

Design theory of high-Q optical ring resonator with asymmetric three-layered dielectrics

An optical ring resonator with asymmetric three-layered dielectrics is shown to have an anomalously highQ-factor compared with the conventional symmetric three-layered ring resonator by several orders of magnitude for suitably chosen parameters. A new leaky mode which can propagate on the asymmetric structure is found having an extremely small attenuation loss near the cut-off frequency of the guided mode, but which does not exist in the symmetric structure. Optimum values of the normalized frequency for a single-mode operation to suppress the undesired leaky modes are discussed. It is also shown that the size of the ring resonator using the asymmetric structure can be reduced considerably from that of the ordinary symmetric resonator.     

Transmission of high-data-rate optical signals through a micrometer-scale silicon ring resonator

The effects of a micrometer-scale silicon ring resonator with a FWHM of 0.078 nm (9.6 GHz) on a nonreturn to zero amplitude-modulated optical signal with a modulation rate of 10 Gbps are experimentally investigated. By transmitting the optical signal through the device, significant spectral distortion and side band attenuation is introduced, as characterized by amplitude Bode plots, and a power penalty of 0.8 dB is observed. Carrier wavelengths within the transmission resonance, but detuned from the center wavelength, are investigated as well. Numerical simulations further support the experimental results.