Po-Kuan Shen

Optical interconnect transmitter based on guided-wave silicon optical bench

An optical interconnect transmitter based on guided-wave silicon optical bench is demonstrated. The guided-wave silicon optical bench (GW-SiOB) is developed on a silicon-on-insulator (SOI) substrate. The three-dimensional guided-wave optical paths on the silicon optical bench are realized using trapezoidal waveguides monolithically integrated with 45° micro-reflectors. Such three-dimensional guided-w ave optical paths of SiOB would simplify and shrink the intra-chip optical interconnects located on a SOI substrate. The clearly open eye patterns operated at a data rate of 5 Gbps verifies the proposed GW-SiOB is suitable for intra-chip optical interconnects.

SOI-based trapezoidal waveguide with 45-degree microreflector for non-coplanar light bending

SOI-based trapezoidal waveguide with 45° reflector for non-coplanar light bending is proposed and demonstrated. The proposed structures include 45° micro-reflector and silicon trapezoidal waveguide. Due to the SOI-based trapezoidal waveguide with 45° reflector, light wave can be coupled into silicon waveguide easily and have higher coupling efficiency. All of structures are fabricated using a single-step wet etching process. The RMS roughness of waveguide sidewall and 45° micro-reflector is about 30 nm. The coupling efficiency of proposed structure is -4.51 dB, and misalignment tolerance are 42 μm at horizontal direction and 41 μm at vertical direction. The multi-channel trapezoidal waveguide is also demonstrated. This device can transfer the light wave at the same time, and its cross talk is about -50 dB.

Chip-Level Optical Interconnects Using Polymer Waveguide Integrated With Laser/PD on Silicon

In this letter, we demonstrate a chip-level high-speed optical interconnect, where the optical transmitter/receiver, the polymer waveguides, and the silicon-trench 45° microreflectors are integrated on a single silicon platform. The silicon platform with a silicon trench can provide independent photonic and electrical layers, respectively, for high-speed and low-speed (except high-frequency transmission lines) data transmissions. In order to demonstrate the technical capability of chip-level optical interconnects, the vertical-cavity surface-emitting laser (VCSEL)/photodetector (PD) and the driver/amplifier IC as well as the polymer waveguides combined with the 45° microreflectors are integrated on the electrical and photonic layers of the silicon platform, respectively. The total optical transmission (VCSEL-to-waveguide-to-PD via two 45° microreflectors) is -4.7 dB. The high-speed transmission experiment shows the clear eye opening up to 20-Gbit/s data rate. The bit error rate better than 10-12 for the proposed architecture is also successfully demonstrated. It reveals such chip-level optical interconnects based on the proposed silicon platform with the polymer waveguides is suitable for high-speed data transmission.

SOI-based trapezoidal waveguide with 45° microreflector for noncoplanar optical interconnect

A silicon on insulator (SOI)-based trapezoidal waveguide with a 45° reflector for noncoplanar optical interconnect is demonstrated. The proposed waveguide is fabricated on an orientation-defined (100) SOI substrate by using a single-step anisotropic wet-etching process. The optical performances of proposed waveguides are numerically and experimentally studied. Transmittance of -4.51 dB, alignment tolerance of ±20 μm, cross talk of -53 dB, and propagation loss of -0.404 dB/cm are achieved The proposed waveguide would be a basic element and suitable for the future intrachip optical interconnects.

45

The 45°-mirror terminated polymer waveguides fabricated on a silicon substrate are demonstrated for on-chip out-of-plane optical interconnects. The silicon 45^° microreflectors are fabricated on an orientation-defined (100) silicon substrate by using anisotropic chemical wet etching. On using a photolithography process, we observe two vertically bending paths at the input and output ports of polymer waveguide on a silicon substrate with 45^° microreflectors. The transmission efficiency of -3.77 dB is measured for a 0.5-cm polymer waveguide combined with the 45^° microreflectors. The optical loss occurring at the 45^°-mirror is -0.27 dB. The channel-to-channel crosstalk for the 250-μm pitch is less than -40 dB. The wider alignment tolerance up to ±15 μm would facilitate the active-device assembly on a silicon substrate.

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The chip-level 1 × 2 optical interconnects using the polymer vertical splitter developed on a silicon substrate are demonstrated. The 1 × 2 vertical-splitting configuration is realized using a polymer waveguide terminated at three silicon 45 ° reflectors. The high-frequency transmission lines combined with the indium solder bumps are developed to flip-chip assemble a vertical-cavity surface-emitting laser chip at the input port and two photodetector chips at two output ports. Total transmission loss of -3.26 dB with a splitting ratio of 1 : 1 for the proposed splitter is experimentally obtained. A 10-Gbit/s data transmission with bit error rates better than 10-12 for two output ports is achieved. It reveals that such chip-level 1 × 2 optical interconnects using the polymer vertical splitter are suitable for high-speed data transmission with multiple output ports.

-Mirror Terminated Polymer Waveguides on Silicon Substrates

A polymer-waveguide-based optical circuit with two vertical-transition output ports for the optical interconnects is demonstrated on a silicon substrate. Such a 1 × 2 vertical splitter is realized using a polymer waveguide monolithically integrated with three silicon 45° microreflectors. The vertical-cavity surface-emitting laser chip assembled at the input port and two multimode fibers located at two output ports are arranged to demonstrate a two-port optical proximity coupling of the off-chip optical interconnects based on the proposed splitter. The optical insertion loss of -6.6 dB is experimentally obtained for the proposed 1 × 2 vertical splitter with a splitting ratio of 1.3 : 1. The clearly 10-Gb/s optical eye patterns at both output ports verify that the 1 × 2 vertical splitter is suitable for the optical interconnects with multiple output ports.

Chip-Level 1

A chip-level optical interconnect module combined with a vertical-cavity surface-emitting laser (VCSEL) chip, a photodetector (PD) chip, a driver integrated circuit (IC), and an amplifier IC on a silicon-on-insulator (SOI) substrate with 3-D guided-wave paths is experimentally demonstrated. Such an optical interconnect is developed for the signal connection in multicore processors or memory-to-processor interfaces. The 3-D guided-wave path, consisting of silicon-based 45° microreflectors and trapezoidal waveguides, is used to connect the optical signal between transmitter and receiver. In this paper, the VCSEL and PIN PD chips are flip-chip integrated on a SOI substrate to achieve complete chip-level optical interconnects. Due to the unique 3-D guided-wave path design, a higher laser-to-PD optical coupling efficiency of -2.19 dB and a larger alignment tolerance of ±10μm for the VCSEL/PD assembly are achieved. The measured laser-to-PD optical transmission efficiency can reach -2.19 dB, and the maximum optical power and threshold current of VCSEL is 3.27 mW and 1 mA, respectively. To verify the data transmission, the commercial driver IC and amplifier IC are assembled upon the silicon chip, and the error-free data transmission of 10 Gbps can be achieved when the VCSEL is operated at the driving current of 9 mA.

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The chip-level 10-Gbit/s optical interconnects with the BER better than 10^-12 using the 1 × 2 polymer vertical splitter, which is composed of a polymer waveguide and three silicon 45° reflectors is demonstrated.

2 Optical Interconnects Using Polymer Vertical Splitter on Silicon Substrate

A whole on-chip optical interconnects integrated with laser, photodetectors, driver IC, and amplifier IC is experimentally demonstrated. A 10-Gbps error-free data transmission is achieved as driving current of laser is 10 mA.