Stable Laser Prompts Lawsuit

Stephanie A. Weiss

Japanese photonics manufacturer Sumitomo Electric Industries has sued Furukawa Electric Co. Ltd., alleging that its semiconductor laser pump diode modules infringe a Sumitomo patent.

Sumitomo's lawsuit, filed on Feb. 13, alleges that Furukawa's Rainbow Pump modules infringe US Patent No. 5,845,030.

The patent covers semiconductor laser modules that comprise a packaged semiconductor laser and a fiber Bragg grating that stabilizes the laser wavelength -- at 1480 nm or other wavelengths -- and, therefore, the power. It also covers erbium-doped fiber amplifiers that employ the laser modules as excitation sources.

Osaka-based Sumitomo has commercialized its patented technology in its SLA5620, -5650, -5660 and -5670 series of pump diodes, which are available in the US through its American subsidiary, ExceLight Communications Inc. of Durham, N.C. The modules are pump sources around the 1480-nm band with 140 to 200 mW of power.

The device description in Furukawa's US Patent No. 5,812,716 is similar to Sumitomo's, but it lists an optical waveguide with a grating -- rather than a fiber Bragg grating -- for wavelength selection. It also states that the optical waveguide may comprise a fiber.

Furukawa, which claims to hold 70 percent of the market for 1480-nm pump lasers, also claims to have commercial Rainbow Lasers (14xx Series) at powers up to 300 mW. The technical specification sheets say that these devices employ fiber Bragg gratings for stabilization.

The lawsuit names Tokyo-based Furukawa plus two US subsidiaries, Furukawa Electric North America Inc. of Peachtree City, Ga., and Fitel Technologies Inc. of Clinton, N.J.