Optical Computing Today

The traditional field of optical computing is no longer so active, it is not dead but it has evolved. Today, numerous research topics benefit from the results of the research in optical computing and therefore the field is perhaps no longer so well defined. Several signs show that the activity has changed. Applied Optics has no longer an issue per month on the subject, but in each issue there is a section “Information processing” with an average of only 4 papers per issue. There are no longer specialized large international conferences named “Optical Computing”. However, it should be noted that there are still two conferences organized by the SPIE on the subject: “Optical Pattern Recognition” since 20 years in Orlando in the frame of the SPIE conference “Defense, Security, Sensing”, and “Optics and Photonics for Information Processing” in San Diego in the frame of the SPIE conference “Optics and Photonics”. In August 2009, a special section on “Optical High-Performance Computing” was published in Applied Optics and JOSA A .

The research on optical correlators is continued by fewer research teams, however it should be noted that the Jet Propulsion Laboratory (JPL) is still working on optical correlators for real time automatic target recognition .

Some of the algorithms developed for pattern recognition initially for optical processing are now used successfully in digital computers. DOEs are now mature and are part of numerous industrial products. All the research on the fabrication of DOEs made possible the fabrication of nano structures and very exciting new fields of research such as nanophotonics , nanofluidics and optofluidics . The list of the papers presented in 2009 at the SPIE conference “Optics and Photonics” reflects the growing interest in all the research related to nanoscience and nanooptics.

Biophotonics is an exponentially growing field that is largely benefiting from the past research in optical processing. Typical examples are the optical tweezers and the optical trapping .

Thanks to the digital holography, where the holographic plate is replaced by a camera, holography is again finding industrial applications particularly for the quality control of manufactured products , for digital holographic microscopy  opening completely new fields of applications for optical microscopy.

For information processing, optics is also finding a place where it has a unique feature such as the polarimetric imaging , or multispectral imaging . Security applications is also a promising field for optical information processing . It is well known that optics is used commonly for the communication systems.

Just to Know

The history of the development of the research in the field of optical computing reveals an extraordinary scientific adventure. It started with the processing power of coherent light and particularly its Fourier transform capability. The history shows that considerable efforts were dedicated to the construction of optical processors that could process in real time a large amount of data. Today, we see that optics is very successful in information systems such as communications and memories compared to its relative failure in computing. This could have changed, if, in the seventies when the electronic computers were slow and with a limited power, today components such as efficient SLMs, laser diodes or high speed and high resolution detectors would have been available. However, all the research results in optical computing contribute strongly to the development of new research topics such as biophotonics, nanophotonics, optofluidics, and femtosecond nonlinear optics. But, the dream of an all optical computer overcoming the digital computer never became reality, and optical correlators for pattern recognition have almost disappeared. The reasons are multiple. The speed of the optical processor was always limited by the speed of the input and output devices. Digital computer have progressed very rapidly, the Moore's law is still valid, multi-core processors are more powerful, and it is clear that digital computer are easier to use and offers more flexibility. Digital computers have progressed faster than optical processors. Optical computing is mostly analogue when electronic computing is digital. The digital optical computers were not able to compete with the electronic due to the lack of appropriate optical components. It appears clearly that the solution is to associate optics and electronics and to use optics only when it can bring something that electronics cannot do. Optical processing is useful when the information is optical and that no electronics to optics transducers are needed.