Planar Lightwave Integrated Circuits With Embedded Actives for Board and Substrate Level Optical Signal Distribution

Abstract

As the data rate of integrated circuits dramatically increases, interconnection speed at the backplane and board levels are beginning to limit system performance, which drives investigations into alternative interconnection technologies. Critical factors to consider when evaluating alternative interconnection approaches include interconnect speed, power consumption, area, and compatibility with current backplane and board integration technologies. Optical interconnections can achieve very high speed with a significant reduction in interconnect footprint compared to transmission lines, robust signal quality in high-density interconnection systems because of immunity to electromagnetic interference, and potentially simple to design (compared to transmission lines) lines with materials which can be postprocessed onto printed wiring boards or integrated into the board structure. This paper explores design options for planar optical interconnections integrated onto boards, discusses fabrication options for both beam turning and embedded interconnections to optoelectronic devices, describes integration processes for creating embedded planar optical interconnections, and discusses measurement results for a number of integration schemes that have been demonstrated by the authors. In the area of optical interconnections with beams coupled to and from the board, the topics covered include integrated metal-coated polymer mirrors and volume holographic gratings for optical beam turning perpendicular to the board. Optical interconnections that utilize active thin film (approximately 1-5 m thick) optoelectronic components embedded in the board are also discussed, using both Si and high temperature FR-4 substrates. Both direct and evanescent coupling of optical signals into and out of the waveguide are discussed using embedded optical lasers and photodetectors. I. INTRODUCTIONA S the data rate of integrated circuits dramatically increases, interconnection speed at the backplane and board levels are beginning to limit system performance, which drives investigations into alternative interconnection technologies. Critical factors to consider when evaluating alternative in-Manuscript

Chip scale integrated microresonator sensing systems

“…The lower row of photomicrographs shows individually integrated and reported components (from left to right): a thin film III-V edge emitting laser bonded to Si [12], a vertically coupled polymer microring resonator integrated onto silicon [13], and an InGaAs metal-semiconductor-metal (MSM) photodetector integrated onto silicon [14]. The planar integration of these optical components is an emerging technology that is being focused upon in the integration of portable optical sensing systems [15][16][17].…”

Challenges for the introduction of board-level optical interconnect technology into product development roadmaps

“…giving away much of the density advantage that the use of optics could provide. Several proposals have been made to embed the optoelectronics into a PCB with integrated optical layers [13,16]. The motivation is to 'hide' the use of board-level optics from the user and solve all the alignment questions during fabrication.…”

“…The term 'long' in this context describes basically everything that leaves a box or a rack, while 'short' includes links on a single card or on the chip level. For the implementation of an optical card-backplane-card link, there are almost as many propositions as there are research groups active in this field ( [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], to just mention a few recent publications; for more references see e.g. [22] or [3]).…”

Chip-to-Chip Optoelectronics SOP on Organic Boards or Packages

“…Prof. Jokerst, et al report on the progress they made in this area on Silicon, ceramic and on high temperature printed wiring boards [13]. A number of researchers around the world have made great strides in designing and fabricating chip-to-chip optoelectronics for high-speed digital data transport over wide areas at the board integration level.…”