Computers That Run on Light

Sierra Kersten
October 27, 2017

Submitted as coursework for PH240, Stanford University, Fall 2017


Fig. 1: An image of a computer. (Source: Wikimedia Commons)

Traditionally, computers process information using copper wires. (Fig. 1 shows an artist's rendering of a traditional computer.) While scientists have been able to fine tune this to create the high-speed computers of today, they still remain inefficient. Recently, scientists have been working to find ways in order to decrease the size of the technology and increase the speed at which data is processed by using optics instead of electricity. While this has been impossible up until now, physicists have recently found ways to process information using photons, making optical computing seem like a possibility.

How It Works

Physicists have long been looking into processing information using light. (Fig. 2 shows a graphical depiction of a light wave.) In order use photons, scientists had to find a material that was capable of carrying the data from light in a computer. [1] To do this, physicists found that they could modify a type of glass called chalcogenide. Chalcogenide, already used in other technologies such as CDs and DVDs, has many useful properties that lend themselves to use in optical devices because they are able to conduct light across a wide range of bandwidths. In the past, scientists only knew how to conduct positive charges using glass, not allowing this to be used in computing. [1] Recently, researchers have found a way in which the glass can be manipulated to conduct both positive and negative charges. By doping the glass with a bismuth ion, scientists can create optical material with pn-juntions without using high temperatures. Because the glass can conduct both positive and negative charges, it can then act as a light detector and light source, allowing it to process and carry the optical information.

Fig. 2: A graphical interpretation of a lightwave. (Source: Wikimedia Commons)


The traditional use of copper wires for processing information within computers, while fast by todays standards, remains inefficient due to the reliance on electrons as the method of processing information. [2] Eighty percent of the power used in computers is lost in the copper wires due to this design, making energy consumption a limiting factor in the speed of computing. Using photons to process information solves this problem. [2] By using photons instead of electrons to process information, the speed of computing can be increased exponentially because light can carry more data at a lower energy cost than electrons. This would allow researchers to create computers that are not only smaller, but also much faster than those in use today.


The use of light in computing opens the door for faster and more efficient computing, previously not possible due to the restrictions of the copper wires used in computers. By using light as the source of energy, scientists will be able to create computers that are smaller and faster than ever before. However, it is still unlikely that these computers will come to fruition as scientists argue. [3] For starters, laptop computers typically require 15 watts to operate. This amount of energy cannot be produced solely from light. In addition, scientists have been unable to get around the use of transistors, which still require the use of the traditional electronics. In this sense, this makes the possibility of fully optical computers in the near future unlikely. The promise of optical computing is enticing, but it terms of practicality, it is still not feasible to implement. Great leaps in the application of optical computing technology must be made before such computers could even be deemed feasible.

© Sierra Kersten. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] Sawchuck, A. A., and T. C. Strand, "Digital Optical Computing," IEEE 1457204, Proc IEEE 72, 758 (1984).

[2] M. A. Karim and A. A. Awwal, Optical Computing: An Introduction, 1st Ed. (Wiley, 1992).

[3] P. Norton, Introduction to Computers (McGraw-Hill, 2004).