April 12, 2001, 4:20 PM — Start-up Optical Crosslinks, Inc. claims it has the ideal material for optical integration.
It's a polymer. But unlike other polymers, which are coated onto silicon wafers, Optical Crosslinks' material is manufactured as a flexible sheet. This gives it quite a few advantages, says director of sales and marketing Lynore Abbott.
A key benefit of the material is "almost no residual stress." That means it doesn't suffer from birefringence (preferred optical directions) and it can accommodate tight bend radii, down to just 3 millimeters. (Stress allows light to leak out of fiber bends, for example, because it lowers the refractive index on the outside of the bend.)
Wafer-coating polymers are usually a type called polyimides. In these materials, the molecules are tightly held together, so the polymer isn't very flexible, Abbott explains. Optical Crosslinks uses a polyacrylate, in which the bonds between molecules are much longer and looser. "People didn't look at polyacrylate originally, because it has a very large temperature dependence," Abbott says. "What we found is, though it expands and contracts, the waveguide properties magically stay the same."
Whats the big deal? Making chips more flexible and bendable means that they can be installed in a variety of applications. This makes the integration of certain parts and functions much easier to accomplish. More tightly integrated components reduce costs and compress functionality into smaller areas. Ultimately, this means service providers will be able to use smaller, more advanced equipment at lower cost. Hopefully, they will be able to pass along the benefits to end users.
The flexible polymer discovery was made by Bruce Booth while at Dupont. He spun off the company in 1998, licensed the technology from Dupont, and has never looked back. The start-up was originally called Polymer Photonics but changed its name to better reflect its market position.
It has seed funding from telecom executives Chad Paul and John Englesson, as well as Essex Investment Mgt. Co. LLC and a number of individuals.
Like most companies targeting optical integration, Optical Crosslinks is starting with something simple. It's already selling what it calls a "pitch transition device" to manufacturers of vertical cavity surface emitting lasers (VCSEL). This is a bunch of tapered waveguides that pipe light from a VCSEL array to a fiber ribbon.
"One of my customers is using a 4x12 VCSEL array," Abbott says. "The closer he can pack those VCSELs [on the wafer], the more money he can make. But he still needs to be compatible with the 250-micron pitch in the fiber ribbon." She figures this to be a huge-volume application.