Application of Photonics

By: meera

Optical interconnect systems
As data rates inside digital electronic systems are increasing, the bandwidth of traditional copper interconnects is increasingly limited by signal distortion, power consumption, cross-talk and pin-out capacity. Optical interconnects are viable alternatives as they offer higher bandwidth, lower cost and lower power dissipation compared to traditional copper interconnects.
To fully exploit the advantages of optical interconnects over their electrical counterparts at the inter-chip level, it is necessary to introduce the optical access directly on the digital CMOS chip. This requires tight integration of optics with the digital CMOS chip. A consortium of 10 companies has built a system demonstrator, in which two-dimensional laser and detector arrays are integrated on the CMOS chip using flip-chip technology. Data between chips is transported over a two-dimensional optical fiber ferrule, which interfaces to the packaged chips with optical access.
Also for future generation electronic circuits, optical interconnect at the intra-chip level is very promising. But to be acceptable to the microelectronics industry, severe constraints are imposed on the design of the optical interconnect layer. All fabrication steps should be compatible with future generations of electronic circuits and the total additional cost incurred should remain affordable. This means that as many fabrication steps as possible should be wafer-scale processes. Therefore, investigating in the feasibility of adding a photonic interconnect layer on top of silicon ICs is done. This interconnect layer is fabricated by a combination of wafer bonding and wafer-scale processing steps. It is planar and will be built from a high-density passive optical wiring circuit integrated with InP-based sources and detectors using a wafer bonding approach.

SOI-waveguides allowing for very high-density wiring are being developed and fabricated using standard CMOS-processing techniques. The III-V epi-material for the active photonic devices is
Telecommunication systems
In the area of optical communications, work has been continued on tunable laser diodes and optical regenerators, two components which are considered keys for future all-optical networks. In the past new types of widely tunable laser diodes has been successfully designed and characterized. This year, attention has focused on the further optimization of those laser diodes and on their direct modulation behavior C11818, RP107
Optical performance monitoring using asynchronous signal histograms has proven to be very useful in numerous experimental setups. In research a signal independent asynchronous histogram construction method using only a 2R regenerator and an adjustable attenuator, thereby avoiding complex sampling systems and high-frequency electronics, is developed. A theoretical study was performed, defining the minimal requirements to the 2R regenerator used, and several case studies using experimental data were investigated. A simulation platform was developed making the extension to other regenerator configurations possible. It shows that if an appropriate regenerator is available, signal monitoring of any optical data signal should be possible.
Sensor applications
Optical sensors are immune to electromagnetic interference and can be used in harsh environments. They also provide good sensitivity, linearity and stability. Commercial applications include physical sensing (e.g. strain) and chemical or biological sensing. Currently, most optical sensors are based on fiber optics or free space optics, but INTEC's research deals with integrating the sensor functions on photonic ICs.
A micro-fluidic flow cell is constructed so that biological samples can be flown over the sensor in a controlled manner. The first tests for the sensing of an avidin-biotin binding are accomplished. In collaboration with the Molecular Biology Group (UGent, VIB) and the Polymer Research Group (UGent) a design for SOI multi-array sensors and their surface treatment is made.

PHOTONICS
Photonics is the science of generating, controlling, and detecting photons, particularly in the visible and near infra-red spectrum, but also extending to the ultraviolet (0.2 - 0.35 ?m wavelength), long-wave infrared (8 - 12 ?m wavelength), and far-infrared/THz portion of the spectrum (e.g., 2-4 THz corresponding to 75-150 ?m wavelength) where today quantum cascade lasers are being actively developed. Photonics is an outgrowth of the first practical semiconductor light emitters invented in the early 1960s at General Electric, MIT Lincoln Laboratory, IBM, and RCA and made practical by Zhores Alferov and Dmitri Z. Garbuzov and collaborators working at the Ioffe Physico-Technical Institute and almost simultaneously by Izuo Hayashi and Mort Panish working at Bell Telephone Laboratories. Photonics most typically operates at frequencies on the order of hundreds of terahertz.
Just as applications of electronics have expanded dramatically since the first transistor was invented in 1948, the unique applications of photonics continue to emerge. Those which are established as economically important applications for semiconductor photonic devices include optical data recording, fiber optic telecommunications, laser printing (based on xerography), displays, and optical pumping of high-power lasers. The potential applications of photonics are virtually unlimited and include chemical synthesis, medical diagnostics, on-chip data communication, laser defense, and fusion energy to name several interesting additional examples.
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