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We propose dual microring-resonators coupled with a Mach-Zehnder interferometer for biosensing. With its simple design and low cost, the detection limit is enhanced as an 8.3×10-7 refractive-index unit through ring-down interferograms in the spatial domain.

The optical power divider flatness in wavelengths for chip based optical coherence tomography is crucial to higher signal-to-noise ratios. A Mach-Zehnder structure could be utilized to smoothly maximize the splitting ratio of 10:90 on a silicon platform with a 0.2 micrometer of decoupler optical path difference, which is insensitive to the process variation up to 40 nanometers. A point spread function applied on the Mach-Zehnder directional coupler shows at least a 20-dB signal-to-noise ratio improvement in optical coherence tomography applications.

A bidirectional 3-dB coupler in the interferometer based on-chip optical coherence tomography demonstrates a broad and flat 200-nm wavelength response through the particle swarm numerical optimization, which could maintain the axial resolution and sensitivity.

The fano-resonance biosensor is formed through the phase variation of microcavity- resonator-coupled Mach-Zehnder interferometers. After windowed Fourier transform, the biological phase sensitivity could be effectively enhanced and theoretically demonstrate the limit of detection as 10-7 refractive-index-units.

We simulated a linear wavenumber arrayed waveguide grating (AWG) as spectrometer in SD-OCT. With this configuration, we save computational cost for resampling wavelength spectrum. Linear wavenumber AWG can maintain the axial resolution for all depth response.

We design Mach-Zehnder directional coupler (MZDC) and tandem MZDC on a silicon chip by using particle swarm optimization algorithm. We obtained wavelength flatness of more than 100 nm and 180 nm, respectively, with ±20 nm process-width variation.

The beam formation can be treated as the diffraction pattern. A 1-D light detection and ranging beam steering could be derived through a phase shifter array using Rayleigh&ndash, Sommerfeld Diffraction, which is then utilized to demonstrate grating lobe-free beam steering from the optical phase array emitter with half-wavelength pitches. The half-wavelength pitch cannot demonstrate beam formation without any evanescent coupling blocking between emitters. Here, two index-mismatched silicon wires in the emitter array are proposed by the optical phase compensation through waveguide width adjustment, to avoid the complex and addressable thermal control on the phase shifters. Moreover, the same output optical waveguide mode needs to be further considered to demonstrate the grating lobe-free beam steering. In order to get the adiabatic connection between two different pitches between the phase shifter and emitter, an optical path equalization will also be applied.

We design and compare the splitting ratio wavelength flatness of directional coupler (DC), Mach-Zehnder directional coupler (MZDC), and tandem MZDC. All coupler responses are analyzed, and tandem MZDC performance is the best in the wavelength insensitivity compared with the other two. An MZDC with any coupling ratio could be utilized to match the maximum flatness in a 40-nm wavelength range. To extend a broad flatness range, the tandem MZDC is proposed and still follows the Mach Zehnder structure taking two MZDCs as couplers connected through a decoupled region. Unlike DC, MZDC with the flat wavelength response has a non-linear output phase. Hence, using two wavelength-insensitive MZDCs as the coupling function in a tandem MZDC could demonstrate a more extensive decoupled phase term to maximize the flat wavelength response. The tandem MZDC theoretically demonstrates the splitting ratio with 100-nm flatness in the wavelength range from 1250 nm to 1350 nm. Finally, a point spread function through the tandem MZDC shows a 24-dB signal-to-noise ratio improvement in optical coherence tomography applications.

A tandem Mach-Zehnder directional coupler (MZDC) demonstrates maximally flat wavelength-insensitive optical power divider compared with directional coupler and MZDC. Its 100-nm wavelength response could enhance the signal-to-noise ratio of optical coherence tomography up to 24-dB.

A tandem Mach-Zehnder directional coupler (MZDC) demonstrates maximally flat wavelength-insensitive optical power divider compared with directional coupler and MZDC. Its 100-nm wavelength response could enhance the signal-to-noise ratio of optical coherence tomography up to 24-dB.

The stabilized phase from polarization maintaining fibers constructs spectral interferometry based surface plasmon resonance on the microRNA. The sensitivity with probing is showing 0.14 rad/(µg/mL), which resolution is 20 times better than the wavelength modulation.

A SPR interferometric phases are typically manipulated with the analyte index change through the effective reaction length and operating wavelengths, respectively, from fiber based optical-low-coherence-interferometry (OLCI) and spectral interferometry for biosensing. The OLCI stepper motor stage built with 0.2-nm moving limit owns potential to achieve a 70-pM sensing resolution.

A broadband Mach-Zehnder directional coupler (MZDC) splitting ratios of 0.5, 0.29 and 0.08 form a cascaded 1×4 wavelength filter in a 1550-nm wavelength range. The coupled and uncoupled phases are compensated to maximize the insensitive wavelength response of MZDC on optical power and crosstalk.

A broadband Mach-Zehnder directional coupler (MZDC) splitting ratios of 0.5, 0.29 and 0.08 form a cascaded wavelength filter. The phases are compensated to maximize the insensitive wavelength response of MZDC on optical power and phase.

The MRR sensitivity on influenza DNA is enhanced by 1.5 times through round-trip ring-down waveforms interrogated with two-stage MZ interferometer and demonstrates 14.5 µm/µM and 9.7 µm/µM, respectively, for the first and second order interferograms.

The power divider flatness for a Mach-Zehnder directional coupler mainly depends on the uncoupled region. Our study shows that the maximally uncoupled delay length can be optimized for high process tolerance from several splitting ratio iterations.

We reported the progress of developing 400-Gb/s optical transceivers with 1.3-μm electro-absorption modulators for optical interconnect applications in data centers. The key technologies include high-speed light sources, silicon photonics based WDM multiplexers/de-multiplexers, driving and receiving circuits, signal processing and monitoring schemes.

The spatial phase sensitivity on the effective reaction length using optical fiber low coherence interferometry demonstrates 10.4-rad/μM, 34 times more enhancement than the polarized light phase characterization from spectral interferometry based surface plasmon resonance biosensors.

A real-time, high sensitivity and label-free spectral interferometry-based surface plasma resonator biosensor is demonstrated. We prove that the Mycobacterium tuberculosis (MTB)DNA can be captured by the immobilized IS 6110 DNA probe successfully and the system sensitivity is showing −0.162 $(\mathrm{rad}/(\mu \mathrm{g}/\text{mL}))$ from the non-resonant wavelengths.

The polarisation maintaining (PM) fibre constructed the spectral interferometry-based surface plasmon resonance to detect the very small molecule micro ribonucleic acid (miRNA) with a big biological impact on cancer diagnosis. Other than the linear polariser and birefringence crystal in the input of the traditional spectral interferometry, the polarisation controller was simply placed on the injected light to control the transverse electric and transverse magnetic polarised magnitudes through the stable polarisation state of PM fibres for distinct dynamic-range fringes on the optical spectrum analyser (OSA). Owing to the high precision and stability control of operating wavelengths in optical fibre communications, the low-coherence telecommunication source was utilised to detect 21-mer deoxyribonucleic acid which changed U to T according the miRNA-21 sequence. The sensitivity with probing was showing 0.065 nm/(μg/ml), which implied the resolution as 0.3 μg/ml under the 0.02 nm wavelength accuracy on OSA.

A Mach-Zehnder directional coupler (MZDC) is utilized to match the maximal flatness in wavelength and different coupling ratio for course wavelength division multiplexing. Here, the phase from MZDC bend structures on a 250-nm thick silicon-wire is analyzed and will significantly degrade the wavelength flatness and extinction ratio without appropriate compensation.

A s-bend multimode interference (MMI) on 5-μm thick silicon-on-insulator experimentally demonstrated the relative optical delay and coupling power coefficient as 18.3-μm and 0.95, respectively. This s-bend MMI based Mach-Zehnder interferometer wavelength filter could illustrate process-insensitive performance on the flat top response and isolation.

A s-bend multimode-interference (MMI) on 5-µm thick silicon-on-insulator experimentally demonstrated the relative optical delay and coupling-power coefficient as 18.3-µm and 0.95, respectively. This s-bend MMI based Mach-Zehnder interferometer wavelength filter could illustrate process-insensitive performance.

Various analytes can be verified by surface plasmon resonance, thus continuous improvement of this sensing technology is crucial for better sensing selection and higher sensitivity. The SPR sensitivity on the wavelength modulation is enhanced with increasing wavelengths. The telecommunication wavelength range was then utilized to detect Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) under two situations, without immobilization and with 5'-thiol end labeled IS6100 DNA probes, for SPR sensitivity comparison. The experimental data demonstrated that the SPR sensitivity increased more than 13 times with the wavelength modulation after immobilization. Since the operating wavelength accuracy of a tunable laser source can be controlled within 0.001 nm, the sensitivity and resolution on immobilized MTB DNA were determined as 1.04 nm/(μg/mL) and 0.9 ng/mL, respectively.

A surface plasmon resonance sensor for Mycobacterium tuberculosis (MTB) deoxyribonucleic acid (DNA) is developed using repeatable telecommunication wavelength modulation based on optical fiber communications laser wavelength and stability. MTB DNA concentrations of 1 μg/mL and 10 μg/mL were successfully demonstrated to have the same spectral half-width in the dip for optimum coupling. The sensitivity was shown to be −0.087 dB/(μg/mL) at all applied telecommunication wavelengths and the highest sensitivity achieved was 115 ng/mL without thiolated DNA immobilization onto a gold plate, which is better than the sensor limit of 400 ng/mL possible with commercial biosensor equipment.

The optical interconnection using polymer waveguides on the optical and electronic printed circuit board was designed and fabricated for low optical propagation loss and high speed data rate. The ray tracing simulation for the tolerance study of optical interconnection and fabrication was carried by the LightTools commercial software. In order for the easy fabrication and high position accuracy, the polymer waveguides were forming 45° reflective mirrors using dicing approach and followed by the e-beam deposition for silver coated 90° beam turning. The interface coupling loss was discussed in different polishing grit sizes and dicing approaches. Upto 12.5 Gb/s transmission rate and 0.1 dB/cm optical propagation loss were demonstrated in the board-embedded flexible polymer waveguide. The Q factor of 7.4 at 12.5 Gb/s and additional optical loss of 0.3 dB were experimentally shown on the 2-mm bending radius and 180° curvature angle. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1999–2003, 2013

Low-coherence interferometric sensing is typically used to detect phase changes without simultaneous optical ruler calibration in order to by-pass light intensity fluctuations and the periodic nature of the interferometric signal. An interferogram from a two-staged optical low-coherence Mach–Zehnder interferometer is proposed to double the sensitivity improvement for fiber strain sensing. A 1310-nm wavelength distributed feedback laser implemented in an optical ruler achieved 655-nm resolved characterization from its high-coherence interferogram, which could further be enhanced to an average of 18.9 nm using a stepper motor assisted optical ruler. A 2.7-ne high strain resolution was then demonstrated on a 3-m long fiber sensing arm in a Mach–Zehnder interferometer. The relative movement distances between the interferograms were utilized to experimentally show the strain and force sensitivity as 6.8 μm/μe and 8.5 μm/mN, respectively.