Slow-light Sensor Research Articles

Ultra-slow light with high normalized delay–bandwidth product and refractive-index sensing in photonic crystal coupled-cavity waveguide

Ultra-slow light can enhance light–matter interactions and effectively realize all-optical buffering and modulation. In this paper, we present an efficient design for a two-dimensional square-lattice photonic crystal coupled-cavity waveguide , which can realize multi-frequency band slow-light transmission in the near-infrared band (1500–1640 nm).Through adjusting intercavity spacing N and structural parameters of elliptical air holes, high group index n g (202.46) within the bandwidth of 5.04 nm and improved normalized delay–bandwidth​ product of 0.6583 can be obtained at the wavelength of 1550.05 nm. Moreover, the designed devices can effectively function as a slow light sensor with the wavelength sensitivity of 585 nm/RIU. Multiple functions can be achieved synchronously in only one structure, which is essential in complex optical integrated circuits. • Multi-frequency band slow-light transmission is achieved in the near-infrared band (1500–1640 nm). • Both high group index (ultra-slow light) and high NDBP values can be obtained at the wavelength of 1550.05 nm. • The designed devices can effectively function as a slow light sensor with the wavelength sensitivity of 585 nm/RIU.

Portable Automatic Microring Resonator System Using a Subwavelength Grating Metamaterial Waveguide for High-Sensitivity Real-Time Optical-Biosensing Applications

The slow light sensor techniques have been applied to bio-related detection in the past decades. However, similar testing-systems are too large to carry to a remote area for diagnosis or point-of-care testing. This study demonstrated a fully automatic portable biosensing system based on the microring resonator. An optical-fiber array mounted on a controller based micro-positioning system, which can be interfaced with MATLAB to locate a tentative position for light source and waveguide coupling alignment. Chip adapter and microfluidic channel could be packaged as a product such that it is cheap to be manufactured and can be disposed of after every test conducted. Thus, the platform can be more easily operated via an ordinary user without expertise in photonics. It is designed based on conventional optical communication wavelength range. The C-band superluminescent-light-emitting-diode light source couples in/out the microring sensor to obtain quasi-TE mode by grating coupler techniques. For keeping a stable chemical binding reaction, the cost-effective microfluidic pump was developed to offer a specific flow rate of 20 μL/min by using a servo-motor, an Arduino board, and a motor driver. The subwavelength grating metamaterial ring resonator shows highly sensitive sensing performance via surface index changes due to biomarker adhered on the sensor. The real-time peak-shift monitoring shows 10μg/mL streptavidin detection of limit based on the biotin-streptavidin binding reaction. Through the different specific receptors immobilized on the sensor surface, the system can be utilized on the open applications such as heavy metal detection, gas sensing, virus examination, and cancer marker diagnosis.

Coupled Mode Demonstration of Slow-Light Plasmonic Sensor Based on Metasurface at Near-Infrared Region

In this paper, we theoretically and numerically reported a dual plasmon-induced transparency and the relevant sensing property in a multi-cross metasurface by the coupled mode analysis. A phase coupling model was established to characterize the optical response of this plasmonic sensor. It was found that the transparency windows were sensitive to the resonance mode of each metal strip, which was well demonstrated by the theoretical model. Both the sensing property and the slow light in this structure were discussed. A high figure of merit of 223 and sensitivity of 850 nm/RIU were achieved. In addition, the 1170-nm near-infrared light can be slowed down by nearly two order of magnitude with group delay of 0.45 ps in this sensor. These results may provide guidance for light-matter interaction-enhanced slow-light sensor and integrated optical circuit design.

High sensitivity magnetic field sensing method based on magneto-photonic crystal slow light Sagnac interferometers

Abstract The magnetic field sensing properties based on the slow light effect of magneto-photonic crystals are studied. The nonreciprocal slow light effect of the magneto-photonic crystal immersed into an applied magnetic field is deduced by the scattering matrix method. A Sagnac interferometer is designed to enhance the sensitivity coefficient to the magnetic field and suppress the influences of reciprocal disturbances. Numerical results show that the sensitivity coefficient of a MPC slow light sensor is about 50 times that of the sensor made of bulk magneto-optic material with the same thickness. The influences of structural parameters of the magneto-photonic crystal, such as the number of periods, the duty ratio and the chirp, on the sensitivity coefficient are discussed.

MODELING AND DESIGN OF REALISTIC Si3N4-BASED INTEGRATED OPTICAL PROGRAMMABLE POWER SPLITTER

Controllable splitting of optical power with a large splitting ratio range is often required in an integrated optical chip, e.g. for the readout of phase-shift in a slow-light sensor. In this work, we report the modeling and design of an integrated optical programmable power splitter consisting of a Y-junction with a programmable phase-shifter cascaded to a directional coupler. We used a vectorial mode solver, and a combination of a transfer matrix method with a 3D vectorial coupled-mode theory (CMT) to compute the power transfer ratio of a realistic device structure made of Si 3 N 4, TEOS, and SiO 2 grown on a Si substrate. In the simulations, waveguide attenuation values derived from the measured attenuation of a prefabricated test wafer, have been taken into account. Vectorial modal fields of individual waveguides, as computed by a mode solver, were used as the basis for the CMT computation. In the simulation, an operational wavelength around 632.8 nm was assumed. Our simulations reveal that maximum power splitting ratio can be achieved when the directional coupler is operated as a 3-dB coupler with the phase-shifter set to produce a 90° phase-shift. The required coupler length for such desired operating condition is highly-dependent on the gap size. On the other hand, the inclusion of the waveguide loss and the non-parallel section of the directional coupler into the model only slightly affect the results.