Yin-Jung Chang

Chip-to-chip optoelectronics SOP on organic boards or packages

In this paper, we demonstrate compatibility of hybrid, large-scale integration of both active and passive devices and components onto standard printed wiring boards in order to address mixed signal system-on-package (SOP)-based systems and applications. Fabrication, integration and characterization of high density passive components are presented, which includes the first time fabrication on FR-4 boards of a polymer buffer layer with nano scale local smoothness, blazed polymer surface relief gratings recorded by incoherent illumination, arrays of polymer micro lenses, and embedded bare die commercial p-i-n photodetectors. These embedded optical components are the essential building blocks toward a highly integrated SOP technology. The effort in this research demonstrates the potential for merging high-performance optical functions with traditional digital and radio frequency (RF) electronics onto large area and low-cost manufacturing methodologies for multifunction applications.

Hybrid Integration of End-to-End Optical Interconnects on Printed Circuit Boards

This paper discusses the integration of an end-to-end optical interconnect testbed on printed circuit boards using inexpensive off-the-shelf, bare die, optoelectronic components. We developed a process for efficient and simultaneous in-plane optical coupling between edge emitting laser and waveguides, and between photodetector and waveguide. We demonstrated an optically smooth buffer layer separating the printed circuit layer from the optical transport layer. The demonstrated radically new optical interconnect technology, which we refer to as interface optical coupling, is able to efficiently and simultaneously form optical interfaces between waveguides, lasers and photodetectors by photolithographic technique, thereby eliminating the need for micro-lenses and manual alignment. The measured laser to waveguide coupling efficiency is 45% and measured waveguide to photodetector coupling is 35%. The optical link is demonstrated to operate at 10 Gbps.

Board-level optical-to-electrical signal distribution at 10 gb/s

An opto/electrical prototype for on-board optical-to-electrical signal broadcasting operating at 10 Gb/s per channel over an interconnect distance of 10 cm is demonstrated. An improved 1times4 multimode interference (MMI) splitter at 1550 nm with linearly tapered output facet is heterogeneously integrated with four p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself is hybrid integrated onto an FR-4 printed-circuit board with four receiver channels. A novel fabrication/integration approach demonstrates the simultaneous alignment between the four waveguides and the four PDs during the MMI fabrication process. The entire system is fully functional at 10 Gb/s

Ultra-high-speed transmission of polymer-based multimode interference devices for board-level high-throughput optical interconnects

Multimode interference (MMI) devices operating at high data rates are important for integrated optics and optical networks. Their 1×N splitting provides a basic functionality in these applications. Ultra-high speed data transmission at 40Gb/s per channel with a total bandwidth of 320Gb/s for all 8 output ports is demonstrated for the first time on a 1 × 8 photo-definable polymer-based MMI power splitter. The transmission integrity is confirmed by the bit-error-rate (BER) testing. To further determine the speed limitations of MMI devices, ultra-short pulse response of these devices is quantified. For example, for 20fs Gaussian input pulses into a 1×8 polymer-based MMI splitter, the output pulses are severely degraded in coupling efficiency (47%) and completely broken up in time and in space primarily due to inter-modal and intra-modal (waveguide) dispersions.

Design, fabrication, and reliability testing of embedded optical interconnects on package

Optical interconnections offer a potential solution to some of the bottlenecks that electrical interconnection systems face. Some of the challenges with optical interconnect design and development are the introduction of new optoelectronic materials and processes, the increasing bandwidth and decreasing loss requirements, and the need for reducing cost without compromising reliability. The goal of this paper is to report our ongoing work on optical interconnects and interfaces for very short-haul backplane, and board/package-level chip-to-chip interconnections. This research fits in with our future proposed integration technology of embedded optoelectronic active devices such as detector arrays, optical amplifiers and laser arrays coupled to the waveguide by alignment tolerant beam turning passive elements. Through testbed design, fabrication, and reliability testing, the waveguide polymer materials and integration process is evaluated, based on a number of factors which include: optical loss, roughness, optical aging, spectral absorption, refractive index and thermal stability.

System-on-a-package (SOP) module development for a digital, RF and optical mixed signal integrated system

One highly integrated mixed-signal testbed has been developed to demonstrate the concept and realization of advanced System-on-a-Package concept. This experimental system, called Intelligent Network Communicator (INC), deals with three different status of the signals, digital, RF and optical, in a single packaging platform. The INC transmits and receives the high-speed digital signal and wireless signal over the embedded optical waveguide channel. After three years of development efforts, the system has been fabricated by utilizing advanced packaging and assembly processes and full functionality has been demonstrated successfully. Before the final test, each of the sub-blocks has been separately developed and tested. The test results clearly show that the developed system performance meets the design goals. The digital block generated up to 3.2 Gbps of data stream, the RF block had less than -1.5dB of insertion loss up to 6 GHz and the optical block achieved 10Gbps throughput over the embedded optical waveguide built on the low-cost organic substrate.

High-density, end-to-end optoelectronic integration and packaging for digital-optical interconnect systems (Invited Paper)

Recent progress toward implementing high-density, optical-digital building blocks necessary to accomplish efficient, end-to-end optical interconnect architecture on low cost FR-4 boards has been demonstrated. The optical interconnect system consists of fabricating an optical buffer layer separating board metallurgy from the optical lightwave circuit layer, and implementing optical links between embedded lasers and detectors. We will show an example of 1310 nm light from an edge emitting distributed-feedback or Fabry-Perot laser operating at 10 Gb/s being guided to the photo-detector by a polymer waveguide. Both lasers and detector are embedded in the waveguide and all construction is built on a low-cost FR-4 board with 3 levels of metallurgy.

Optical Interconnects for Board-Level Signal Distribution at 10 Gb/s Using Hybrid Integration

A board-level optical-to-electrical prototype for 10 Gb/s signal distribution over each of four channels is demonstrated. An improved multimode interference (MMI) splitter and the simultaneous alignment between waveguides and photodetectors make the prototype fully functional

Hybrid interconnects using silicon/FR-4 substrates for board-level 10 Gb/s signal broadcasting

An opto/digital interconnect prototype for board-level 1times4 optical-to-digital signal broadcasting operating at 10 Gb/s per channel over an interconnect distance of 10 cm is demonstrated. An improved 1 times4 multimode interference (MMI) splitter at 1550 nm with linearly-tapered output facet is heterogeneously integrated with 4 p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself is hybrid integrated onto an FR-4 printed-circuit board (PCB) with 4 receiver channels. A novel fabrication/integration approach demonstrates the capability of simultaneously aligning multiple polymer waveguides with multiple optoelectronic (OE) devices during the waveguide fabrication process. The combined excess loss of the MMI splitter and the mirror loss per channel is less than 3.5 dB and the entire system is fully functional at 10 Gb/s

A digital-optical system-on-package module architecture for high performance multiprocessors

This paper reports on the progress toward implementing optical-digital building blocks necessary to accomplish a system-on-package module architecture for high-performance multiprocessors. In this architecture, the memory access delay (MAD) bottleneck is minimized by using a 3-D distributed shared memory field in which high speed optical interconnects deliver data to and from each processor in a cluster to each memory controller/MX-DMX in the field, each memory controller being connected to a small cluster of main memory via a short, high aggregate speed copper bus that essentially matches the intrinsic MAD of the DRAM chip.