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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.

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.

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 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.

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.

The phase from quasi-decoupled hybrid plasmon and coupled bending regions of Mach-Zehnder directional couplers was characterized for broadband optical power dividers. The splitting ratios demonstrated within 8% variation across 200-nm bandwidth using 400-nm quasi-decoupler spacing.

Two FBG spectral convolution was characterized using a delayed self-homodyne method for strain sensing. The strain sensitivity demonstrated 165-MHz/j.e and sensing limitation could achieve 1-ns with 165 kHz bandwidth resolution in the electric spectrum analyzer.

This paper proposed a strain sensing system using two-stage optical low coherence Mach-Zehnder interferometry. A 1.3-μm wavelength distributed feedback laser for an optical ruler assisted stepper motor was implemented to achieve 19.3-nm resolved characterization. The interferogram calibrated by the stepper motor combined with optical ruler on a 3-meter long fiber then demonstrated a 2.78-ne high resolution strain sensing. It successfully demonstrated that a stable stepper motor can further improve the optical ruler encoder to establish a high sensitivity and high resolution interferometric strain sensor.

A fiber-optic strain sensor based on the two-staged optical low coherence Mach-Zehnder interferometry was proposed using 1.3-μm wavelength optical ruler assisted stepper motor. A 2.78-ne high resolution strain sensing was demonstrated.

The extinction ratio of a Mach-Zehnder interferometer, a cascade of two directional couplers, is a critical parameter for the bit error rate performance of differential quadrature phase shift keying (DQPSK) demodulation. The coupling length of a directional coupler is also strongly dependent on polarization and wavelength. A Mach-Zehnder directional coupler including the bending effects was then proposed on a 5-µm thick silicon-on-insulator waveguide. A 30-dB extinction ratio and 0.5-dB polarization dependent loss over C+L bands of the lightwave communication wavelengths were demonstrated for DQPSK demodulation applications.

An optical low-coherence interferome-try was utilized to characterize the birefringence on 5-µm thick silicon-on-insulator waveguides. The SMF-28 fiber was taken as a baseline to demonstrate 2.6×10−3 waveguide birefringence with 5-µm width and 2.5-µm etch depth.

The coupling length of directional couplers was polarization strongly dependent, especially for the waveguide tap. A 12-μm-thick silicon-on-insulator waveguide combined with the bending effect on directional couplers could minimize the polarization-dependent-loss to 0.15dB for monitoring.

A wavelength-insensitive tap waveguide using a relative phase shift between two directional couplers was demonstrated to get 3.7% coupling ratio and 0.25 dB chromaticity across the whole C-band via 12 μm thick silicon-on-insulator waveguide.

5 mum thick silicon-on-insulator waveguide was demonstrated to low birefringence of 4.6times10-5. Instead of complex processing from 3D mode size converter, the high numerical aperture fiber was utilized as the bridge between corresponding waveguide and SMF-28 fiber to get competitively coupling loss of 0.4 dB.

A photodetector can be applied onto the silicon-on-insulator waveguide tap to monitor light signals on waveguide for the surface mount detection. The reflective metal layer integrated with 54.7-degree angles from anisotropic silicon wet-etching demonstrated low polarization-dependent-loss of 0.2 dB.

The reflected light intensity from an extremely low thermal coefficient of zerodur etalon was utilized to stabilize laser frequency using Pound-Drever-Hall approach. The reflective signal-to-noise ratio of etalon is affected by coated mirror reflectivity and insertion loss. Over 6 dB signal-to-noise ratio and more than 100 etalon finesse were demonstrated.

We have demonstrated a silicon-on-insulator based photonic bus with integrated splitters and multi-channel optical wavelength selection. The integrated photonic bus has demonstrated a 33+ dB optical crosstalk and a 32+ dB extinction ratio with two-stage of Mach-Zehnder attenuators.

Wavelength division multiplexing (WDM) is rapidly becoming a mainstream technology for high capacity optical communications. One of the critical components needed in WDM systems is a multi-wavelength laser array. The external cavity laser array configuration, which exhibits accurate channel spacing control, is particularly appealing for many WDM systems. Up to now all integrated external laser array processes require one or more steps or semiconductor regrowth and/or alloy disordering to produce the passive elements. These greatly limit the materials and devices which can be used. In this paper we present an integrated WDM laser array based on an external glass cavity Rowland circle spectrometer which does not require a regrowth process. The laser array process is fully compatible with the conventional ridge laser process and, thus, can be implemented in all materials systems.

Summary form only given. Monolithic optoelectronic integrated circuits (OEICs) are of considerable interest for future optical communications systems in the 1.3-1.6 /spl mu/m wavelength range due to the significant reduction in interconnections and ease of assembly. For some OEIC applications, it is useful to use GaAs substrates instead of InP because of the mature fabrication technology for electronic components on GaAs. For high-speed device applications, air-bridge coplanar metal waveguides are an attractive means to interconnect high-speed photodiodes, which results in a reduction of the parasitic capacitance of the diodes. Of the various waveguide photodiode integration approaches, total internal-reflection (TIR) mirror vertical coupling is regrowth-free and applicable to single and double heterostructure waveguides. In the paper, we used a thin InP buffer layer, grown by solid source molecular beam epitaxy, to suppress the dislocations between In/sub 0.53/Ga/sub 0.47/As/InP photodiode and AlGaAs/GaAs waveguide layers. The GaAs-based optical waveguide couples light to the p-i-n InGaAs photodetector by an etched, vertically deflecting TIR mirror.

The first solid-source molecular beam epitaxial growth of In/sub 0.53/Ga/sub 0.47/As photodetector structure on top of an AlGaAs/GaAs waveguide for monolithic 1.55 /spl mu/m receiver applications has been demonstrated using a single, thin InP buffer layer to suppress dislocations. Mesa-type detector arrays were made by chemically assisted ion beam etching. Utilizing a novel dense array fabrication technique, we demonstrated the integration of InGaAs optoelectronic devices with AlGaAs/GaAs waveguide films grown on a GaAs substrate. These heterostructure photodiode arrays, which can be readily integrated with GaAs optoelectronic and electronic components, also show high photoresponsivity (0.7 A/W without any antireflection coating), and exhibit a bandwidth in excess of 7 GHz.