Photonic Switching Devices Using Light Bullets

Link to Full Patent:
US5651079

US5963683

Objective

NASA Ames Research Center seeks to license an invention which describes devices using light bullets to perform ultra-fast, all-optical switching. This technology enables all-optical switching in a solid state device, such as a planar slab waveguide made of highly nonlinear optical materials including highly non-linear glasses, semiconductor crystals, and/or multiple quantum well semiconductor materials. It uses optical pulses in the planar waveguide, and these pulses are stable and self-supporting due to nonlinear effects that balance the effects of dispersion and diffraction, i.e. these pulses are light bullets. Major advantages are the potential for massive parallelism (in space) and pipelining (in time).

The figure shows the results of the computer simulation of two colliding light bullets that deflect each other through attraction. The figure plots the electric field at four different times. At the first instant of time, it shows the two pulses approaching, Then they are interfering destructively, (and the energy is now contained in the magnetic field, which is not shown, but which is also calculated). Next they are interfering constructively, and finally they are departing. Notice that they have regained their initial shapes. They have also deflected each other, although from the viewpoint of the figure, the deflection is not noticeable. An overhead viewpoint shows that after the collision, at the time of the fourth instant shown in the figure, the left moving pulse has been deflected down a distance about equal to the pulse width and the right moving pulse has been deflected up an equal distance. This deflection is the basis of the light switch, where light switches light. Notice also that the optical cycles are displayed in each pulse. This method of calculation resolves the motion of the optical carrier in each pulse so that the phase velocity of the optical carrier, as well as the group velocity of the pulse can be observed.

Product Profile

The rapid proliferation of information technology in commerce, finance, education, health, government, security, and entertainment, together with the ever-increasing power of computers and data storage devices, is beginning to fuel a potentially massive demand for network interconnection, especially broadband services. Switching is an essential operation of all communications networks and digital computers and signal processing systems. Switching is presently a limiting factor in the speed of operation of optical communications and computing as most commercial devices must use either electrical, acoustic, or magnetic forms of switching. Switching using asynchronous transfer mode (ATM) is expected to meet the short-term demand, but in the longer term electronic systems will become increasingly complex and costly. Network designers will turn increasingly to photonic transport and switching technologies. An all-optical switch would have the inherent advantages of higher speed and higher efficiency.

NASA researchers have performed computer simulations and developed designs for an all-optical switch made of highly nonlinear materials. In the NASA switch configuration, light bullets propagate through, and interact nonlinearly with each other within a planar slab waveguide to selectively change each others directions of propagation into predetermined output channels. The resulting performance should enable low power, high speed (100 femtosecond light bullets) switching in a small device, easily manufactured using current semiconductor manufacturing techniques.

Benefits

• Faster speed of operation
• No pulse degeneration
• Requires less energy
• Potential for massive parallelism (in space) and pipelining (in time)
• High reliability; solid state device with no moving parts
• Uses commercially available materials
  

Potential Applications

• High speed optical fiber communications
• All-optical communications networks
• Optical computing systems
• All-optical logic gates
  

Technical Basics

There are a number of all-optical switching devices, including some that use solitons. A special form of solitons, called light bullets, are essentially pulses of light which, when propagating in a non-linear medium, maintain their shape and are self-guided due to the balance of diffraction, the mediums group velocity dispersion, and nonlinear self-phase modulation. To date light bullets have been studied only theoretically, and some disagreement exists over the conditions which are necessary for them to exist and function.

NASA Ames researchers have performed computer simulations using the exact Maxwells equations without any approximation, and have shown that light bullets are in fact stable and that there is no need for saturation of the material to obtain stability. NASA innovators have described the necessary material parameters including negative group velocity dispersion, high non-linear index of refraction, and wavelength of light in order for the light bullets to interact and selectively change each others direction of propagation.

Based upon these simulations, NASA has described all-optical switching devices using light bullets in planar slab waveguides made from commercially available nonlinear glasses and semiconductor materials. Propagating light bullets interact in such a way that they are deflected in different output channels from the waveguide thus constituting an all-optical switch. The multiple quantum well semiconductors are of particular interest as they require far lower powers (below 1 Watt) of light intensity in order to support light bullet propagation.

Technology Commercialization Status

NASA Ames currently seeks to license the Photonic Switching Devices Using Light Bullets invention to U.S. companies for commercialization. NASA's expertise in this area is in the computer simulation of the behavior of light bullets in nonlinear materials. The commercial partner (or third-party research laboratory) will be expected to bring the necessary expertise to demonstrate the devices experimentally.

Contact

If your company is interested in this technology or would like licensing instructions, please contact:

David Lackner
NASA Ames Research Center
Moffett Field, CA 94035
Phone: (650) 604-5761
Fax: (650) 604-1592
E-mail: dlackner@mail.arc.nasa.gov