Optical device module packages for subscriber incorporating passive alignment techniques

We propose 400-Gb/s (16 × 25 Gb/s) optical transmitter and receiver modules for on-board interconnects using polymer waveguide (PWG) arrays. Four four-channel vertical cavity surface emitting laser and PIN photodiode arrays are used in the optical transmitter and receiver modules. A 16-channel PWG array with a length of 140 mm and a pitch of 62.5 μm is used as a short-reach optical signal transmission medium in the module. The 25-Gb/s optical eye diagrams of the all output channels utilize PWG transmissions and exhibit good performance in the transmitter module, with a signal-to-noise ratio (SNR) of over 8.01, peak-to-peak time jitter below 11.70 ps, and mask margin of over 31.5%. In the best-performance channel of the receiver module, the peak-to-peak time jitter and SNR of the eye diagram are 10.34 ps and 10.76, respectively, and the receiver sensitivity is approximately −2.6-dBm under a bit error rate of 10−12. The optical transmitter and receiver modules utilizing PWG transmissions were designed and fabricated to realize 400-Gb/s on-board interconnects.

This paper describes optical transmitter and receiver modules for package-to-package interconnection in broadband switching networks such as an asynchronous transfer mode switch fabric. These modules, which include the multiplexer and demultiplexer, can reduce the number of connections and the problem of skew between links. Five-channel optical transmitter and receiver modules were fabricated and demonstrated at 2.8 Gbit/s with a power dissipation of 4.5 W per channel. Moreover, temperature-insensitive optical interconnection was successfully demonstrated by driving a laser with a constant bias current over the threshold and by deducting the optical signal offset. The output power of the transmitter module was -4.2 dBm. Nonuniformity of the transmitter output powers across the range of optical channels was <2.1 dB. Receiver sensitivity for a bit error rate of 10/sup -11/ was -9.3 dBm. Nonuniformity of the receiver sensitivities was <1.5 dB. The power penalty of the receiver sensitivity due to crosstalk was 1 dB. The connection distance was >250 m.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents and discusses experimental results which successfully demonstrate using flip-chip techniques, the bonding and operation of a GaAs edge emitting laser on a silicon substrate having recessed bonding pads. The flip chip alignment and bonding technique is discussed first, focusing on experimental results for both flux and flux-less forms of solder bump processing, the developed flux-less technique is shown to provide comparable solder bump integrity and yield. Subsequent to the newly developed solder bump fabrication methodology shown, a recessed bonding pad design is introduced and demonstrated experimentally to aid in the final coarse alignment and assembly of the GaAs laser device onto a silicon substrate. Together both the flux-less solder bump and bonding pad recess design and fabrication processes provide increased reliability for integration with MEMS and MOEMS based devices and systems over traditional methods for hybrid device attachment.

We developed transmitter and receiver modules with Ti:PPLN waveguide operated as difference frequency generator to convert a signal (lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> ~ 1550 nm) to the mid infrared (lambda <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">i</sub> ~ 3800 nm) and back again.

ABSTRACTIn order to examine the use of a compliant cantilever structure as a contact scheme for a Multi-chip Interconnection System (MIS), multi-layer (metals and SiO2) cantilever beams were fabricated utilizing standard silicon processing and micromachining technologies. The mechanical behavior and electrical characteristics of the beams were investigated in order to establish their optimum dimensions for use in the MIS. During the course of this study, a new mechanical testing method for thin films has also been developed, which makes use of the same cantilever beam structure and a “Nanoindenter.” The Young's modulus and yield strength of thermally grown SiO2 and Au were measured using this technique.

Current methods for the formation of pre-solder bumps for flip chip attachment use stencil printing techniques with an appropriate alloy solder paste. The continuing trend towards increased miniaturization and the associated decrease in size of solder resist opening, SRO is causing production difficulties with the stencil printing process. Practical experience of production yields has shown that stencil printing will not be able to meet future requirements for solder bump pitch production below 150μm for these applications. This paper describes latest developments in the electrolytic deposition of solder to replace the stencil printing process; results from production of 90μm bump pitch solder arrays with tin/copper alloy are given. The solder bump is produced with a specially developed electrolytic tin process which fills a photo resist defined structure on the SRO. The photoresist dimensions determine the volume of solder produced and the subsequent bump height after reflow. Investigations on the bump reliability after reflow are shown including copper alloy concentration at 0.7% and x-ray investigation to confirm uniform metal deposition. The self centering mechanism found in the bump production process during reflow is presented and the capability to correct photoresist registration issues. The solder bumps are shown as deposited onto an electroless nickel/gold or electroless nickel/palladium/gold final finish which serves also as a barrier layer to copper diffusion into the solder bump. Discussion of further development work in the production of alloys of tin/copper together with silver are given with first test results.

Modeling behavior of broadband (30-1000 MHz) frequency modulated near infrared photons through a multilayer phantom is of interest to optical bio-imaging research. Photon dynamics in phantom are predicted using three-dimension (3D) finite element numerical simulation and are related to the measured insertion loss and phase for a given human head geometry in this paper based on three layers of phantom each with distinct optical parameter properties. Simulation and experimental results are achieved for single, two, and three layers solid phantoms using COMSOL (COMSOL AB, Tegnérgatan 23, SE-111 40, Stockholm, Sweden) (for FEM) simulation and custom-designed broadband free space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 680, 795, and 850 nm. Standard error is used to compute error between two-dimension and 3D FE modeling along with experimental results by fitting experimental data to the functional form of afrequency+b. Error results are shown at narrowband and broadband frequency modulation. Confidence in numerical modeling of the photonic behavior using 3D FEM for human head has been established here by comparing the reflection mode's experimental results with the predictions made by COMSOL for known commercial solid brain phantoms.

This paper presents a novel method for early detection of hematomas using highly sensitive optical fNIR imaging methods based on broadband photon migration. The NIR experimental measurements of inhomogeneous multi-layer phantoms representing human head are compared to 3D numerical modeling over broadband frequencies of 30–1000 MHz. A finite element method (FEM) simulation of the head phantom are compared to measurements of insertion loss and phase using custom-designed broadband free space optical transmitter (Tx) and receiver (Rx) modules that are developed for photon migration at wavelengths of 670 nm, 795 nm, 850 nm, though results of 670 nm are discussed here. Standard error is used to compute error between 3D FEM modeling and experimental measurements by fitting experimental data to the asqrt {frequency} + b . Error results are shown at narrowband and broadband frequency modulation in order to have confidence in 3D numerical modeling. A novel method is established here to identify presence of hematoma based on first and second derivatives of changes in insertion loss and phase (∆IL and ∆IP), where frequency modulated photons sensitive to different sizes of hematoma is identified for wavelength of 670 nm. The high accuracy of this comparison provides confidence in optical bio-imaging and its eventual application to TBI detection.

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A micro-pump for medical applications is being developed using organometallic derived PZT thin films and silicon micromachining technology. Critical issues include the deposition of ‘thick’ PZT films (1 to 2 μm thickness), film processing compatibility with available Si/SixNy/Ta/Pt structures and the establishing of piezoelectric poling parameters. A processing technique for the preparation of thick PZT films is presented. Piezoelectric properties are characterized by both direct method using alternating compressional force and by converse method using laser interferometry. In poled films of approximately 1. 0 μm thickness, d33 values of about 130 pC/N were measured by both direct and converse methods. Maximum d33 constants of ≈ 200 pC/N were measured with 8 V bias voltage. Mechanical resonance was excited in a 1 cm by 1 cm silicon substrate by a 0.8 μm thick PZT film poled at 15 V.

This paper describes the 2.5-Gb/s optical receiver module using a one-chip receiver IC for an ultrabroadband optical access system. The IC provides reshaping, retiming and regenerating functions required for an optical receiver. The reshaping is performed by a preamplifier and a limiter amplifier using a reference voltage generator. Retiming and regenerating are accomplished by a clock-and-data recovery circuit using a phase comparator combined with a regenerator. The IC and an APD are packaged in a compact ceramic package using passive alignment technology. The module has a size of 14/spl times/19 mm, and a power consumption of 450 mW at a +3.3 V supply voltage.

Stacked solder bumping technology for improved solder joint reliability

We propose a new cost-effective structure for a future 100 Gbit/s-class optoelectronic integrated circuit (OEIC) with optical interconnection and a receiver module. This module is a flat compact package and achieves good optical and high-speed electrical performance. A polymeric optical waveguide and a curved micro-mirror are monolithically integrated on the OEIC as the optical interconnection. Furthermore, this OEIC chip is assembled using solder bumps and passively self-aligned technique. We confirmed the feasibility of applying this novel structure to future cost-effective 100-Gbit/s class receiver modules.

Silicon photonics is becoming a mainstream data-transmission solution for next-generation data centers, high-performance computers, and many emerging applications. The inefficiency of light emission in silicon still requires the integration of a III/V laser chip or optical gain materials onto a silicon substrate. A number of integration approaches, including flip-chip bonding, molecule or polymer wafer bonding, and monolithic III/V epitaxy, have been extensively explored in the past decade. Here, we demonstrate a novel photonic integration method of epitaxial regrowth of III/V on a III/V-on-SOI bonding template to realize heterogeneous lasers on silicon. This method decouples the correlated root causes, i.e., lattice, thermal, and domain mismatches, which are all responsible for a large number of detrimental dislocations in the heteroepitaxy process. The grown multi-quantum well vertical p–i–n diode laser structure shows a significantly low dislocation density of 9.5 × 104 cm−2, two orders of magnitude lower than the state-of-the-art conventional monolithic growth on Si. This low dislocation density would eliminate defect-induced laser lifetime concerns for practical applications. The fabricated lasers show room-temperature pulsed and continuous-wave lasing at 1.31 μm, with a minimal threshold current density of 813 A/cm2. This generic concept can be applied to other material systems to provide higher integration density, more functionalities and lower total cost for photonics as well as microelectronics, MEMS, and many other applications.

In this paper, we propose a high-speed optical receiver module with four channels. The optical receiver module was composed of a four-channel PIN photodiode array and a four-channel linear transimpedance amplifier on a six-layer printed circuit board (PCB). The top and bottom layers of the PCB were used as the high-speed layers. The grounded coplanar waveguide structure was designed on the PCB for high-speed data transmissions. The interface of the optical receiver module was designed as the QSFP28 pin definition. According to the eye diagram and bit-error rate measurements, the optical receiver module can be achieved 160 Gb/s NRZ and 200 Gb/s PAM4 transmissions over 1 km single mode fiber [1].