U.S. Patent No. 8,121,449, issued on February 21, 2012 to Redfern Integrated Optics, Inc. (RIO) of Santa Clara, CA, discloses a planar photonic waveguide with a Bragg grating having an asymmetric reflectance spectrum.

The ’449 patent explains that a Bragg grating formed in a planar waveguide generally has a reflectance versus wavelength with a central peak at the Bragg wavelength and multiple side lobes with lower reflectances located on either side of the peak.  For some applications (e.g., filtering), these side lobes are desirably as small as possible, so that the Bragg grating reflects only light having the Bragg wavelength.  For other applications (e.g., external-cavity lasers), suppression of the side lobes on the longer-wavelength side of the peak are more important than those on the shorter-wavelength side.  The ’449 patent discloses a structure of the planar waveguide’s Bragg grating that has a cross-sectional dimension that varies symmetrically in both directions along the grating from a center of the grating such that the longer-wavelength side lobes are suppressed relative to the shorter-wavelength side lobes.

According to its website, RIO “develops and manufactures optical sources and subsystems based on its proprietary planar external cavity laser technology.”  RIO’s PLANEX™ series of narrow linewidth single frequency external cavity laser diodes is described as consisting of “a gain chip and a planar lightwave circuit (PLC) that includes a Bragg grating.”  There’s no indication on its website whether RIO’s products utilize the type of Bragg grating described in the ’449 patent.

The ’449 patent almost was never issued because of a missed deadline.  The USPTO mailed an office action to RIO’s representative in April 2008 in which most of the claims were rejected, but some claims were deemed to include allowable subject matter.  Applicants are given a maximum of six months to respond to such office actions, however, RIO never filed a response within this time period, so the application was deemed abandoned by the USPTO.  Nearly three years to the day after the office action was mailed, in April 2011, RIO filed its response to the office action, along with a petition and fee to the USPTO to revive the patent application on the basis that the entire delay in responding was unintentional.  The petition was granted soon afterwards, and the ’449 patent eventually issued. 

Under its rules, the USPTO does not require evidence be submitted in support of the statement that the entire delay was unintentional.  The USPTO can request additional information if there is a question that the entire delay was unintentional, but basically, the USPTO merely checks to see that the required forms and fees have been submitted.  However, even when the petition is granted and the patent is issued, there can be a black mark on the patent that can give a competitor an opening to get away with infringement.

For example, if RIO ever sues an accused infringer of the ’449 patent, the accused infringer will likely challenge the validity of the ’449 patent on the basis that RIO’s entire delay in responding actually was not unintentional (e.g., by proving that RIO knew of the abandonment for a period of time before preparing and filing the petition to revive).  If the accused infringer is successful, the patent would be deemed invalid, so there would be no infringement.  Thus, by being abandoned and then revived, the ’449 patent has a shadow on it that could affect its ability to exclude others from making, using, and selling the claimed invention.