Multimode-based polarization independent WDM devices using different order modes for TE and TM polarizations.

Multimode based polarization independent (PI) wavelength division multiplexing (WDM) devices are proposed and experimentally demonstrated. The key concept is to utilize two different order modes for the orthogonal polarizations, ith-order mode for TE and jth-order mode for TM (i ≠ j) polarization respectively to extend the flexibility for designing devices. PI coupler composed of a multimode directional coupler and mode converters is introduced as a basic device. Then, we apply PI coupler to Mach Zehnder interferometer (MZI) and Bragg grating bandpass filters. PI MZI is achieved by optimizing the combination of two phase shifters in the interferometer arms. PI bandpass uses 3dB-PI coupler and polarization rotate Bragg gratings that induce mode coupling between the polarizations. Each device showed good matching in the spectrum between TE and TM polarizations in term of operation wavelength. The proposed concept can be a promising approach to realize PI WDM functions without introducing polarization diversity scheme in which a polarization beam splitter, two devices designed for each polarization and a polarization beam combiner are required.

Silicon optical filter with transmission peaks in wide stopband obtained by anti-symmetric photonic crystal with defect in multimode waveguides.

We experimentally demonstrate and characterize a wide optical stopband filter with transmission peaks constituted by two parallel rows of an anti-symmetric one-dimensional (1D) photonic crystal with defect in a multimode waveguide. The working principle is based on mode coupling for the wavelengths that meet the phase matching condition as the fundamental mode is coupled to a higher-order mode and then filtered out with linear tapers as they are reflected back. The defect in the photonic crystal works as a Fabry-Perot like cavity that allows for localized states in the stopband to quantify the effects of the design parameters and we show a Fabry-Perot filter that extends through the 200 nm stopband. A compact 7 µm2 device is demonstrated with standard fabrication techniques in Silicon-on-Insulator (SOI), and compared to Fabry-Perot filters in single mode waveguides, we obtain a larger bandwidth and lower back reflections. Applications include refractive index sensors, optical communications and on-chip spectroscopy.

Silicon wire waveguide TE0/TE1 mode conversion Bragg grating with resonant cavity section.

Silicon wire waveguide TE0/TE1 mode conversion Bragg grating can be used in wavelength add/drop and polarization rotation Bragg diffraction. The device can implement many filtering functionalities required in wavelength division multiplexing optical communications. In this paper we describe TE0/TE1 mode conversion Bragg grating device incorporating resonant cavity section to obtain narrow transmission wavelength peak. Theoretical calculation agreed with measured wavelength response.

Silicon waveguide polarization rotator sampled Bragg grating.

In this Letter, we demonstrate, to the best of our knowledge, the first experimental results of sampled Bragg grating with polarization rotator function. Silicon waveguide is used. Multiple polarization-independent reflection wavelength peaks were obtained.

Polarization rotation Bragg diffraction using Si wire waveguide grating and polarization rotator.

We report polarization independent Bragg grating wavelength filter with high diffraction efficiency. A rib waveguide polarization rotator and antisymmetric grating structure for fundamental to first order diffraction are used to generate the polarization rotation Bragg diffraction. The diffraction efficiencies and peak wavelengths become the same for two orthogonal input polarizations. Strong diffraction is attained easily. The concept was verified by simulation and experiment. Polarization independent band-pass filter consisting of polarization beam splitter and polarization rotation Bragg diffraction was experimentally demonstrated.

Polarization rotation Bragg grating using Si wire waveguide with non-vertical sidewall.

We report polarization independent Bragg grating wavelength filter using polarization rotation. A non-vertical waveguide sidewall and antisymmetric grating structure can be used to generate the polarization rotation of the fundamental modes. The diffraction efficiencies and peaks becomes the same for two orthogonal input polarizations. The concept was verified by simulation and experiment.

Demonstration of 12.5-Gbps optical interconnects integrated with lasers, optical splitters, optical modulators and photodetectors on a single silicon substrate.

One of the most serious issues in information industries is the bandwidth bottleneck in inter-chip interconnects. We propose a photonics-electronics convergence system to solve this issue. We fabricated a high density optical interposer to demonstrate the feasibility of the system by using silicon photonics integrated with an arrayed laser diode, an optical splitter, silicon optical modulators, germanium photodetectors, and silicon optical waveguides on a single silicon substrate. Error-free data transmission at 12.5 Gbps and a transmission density of 6.6 Tbps/cm2 were achieved with the optical interposer. We believe this technology will solve the bandwidth bottleneck problem in the future.

12.5-Gb/s operation with 0.29-V·cm V(π)L using silicon Mach-Zehnder modulator based-on forward-biased pin diode.

We present high-speed operation of pin-diode-based silicon Mach-Zehnder modulators that have side-wall gratings on both sides of the waveguide core. The use of pre-emphasis signals generated with a finite impulse response digital filter was examined in the frequency domain to show how the filter works for different filter parameter sets. In large signal modulation experiments, V(π)L as low as 0.29 V·cm was obtained at 12.5 Gb/s using a fabricated modulator and the pre-emphasis technique. Operation of up to 25-Gb/s is possible using basically the same driving configurations.

First demonstration of high density optical interconnects integrated with lasers, optical modulators, and photodetectors on single silicon substrate.

Engineers are currently facing some technical issues in support of the exponential performance growths in information industries. One of the most serious issues is a bottleneck of inter-chip interconnects. We propose a new "Photonics-Electronics Convergence System" concept. High density optical interconnects integrated with a 13-channel arrayed laser diode, silicon optical modulators, germanium photodetectors, and silicon optical waveguides on single silicon substrate were demonstrated for the first time using this system. A 5-Gbps error free data transmission and a 3.5-Tbps/cm(2) transmission density were achieved. We believe that this technology will solve the bandwidth bottleneck problem among LSI chips in the future.