SpectraSensors Inc., a manufacturer of advanced laser-based gas sensor technology, has expanded its operations and completed a move from Altadena, Calif., to an integrated 11,300-square-foot facility in San Dimas, where it now operates R&D, manufacturing, marketing and administrative operations. The company offers two base product lines to the aerospace instrumentation and natural gas industry process control markets, and is developing advanced sensing solutions for hospital equipment sterilization companies, as well as combustion process control for incineration facilities seeking to improve fuel efficiencies and better comply with updated Environmental Protection Agency regulations.   . . .   BAE SYSTEMS North America has named Walter P. Havenstein as its executive vice president.   . . .   Cynosure Inc., a Chelmsford, Mass., developer of laser technology for cosmetic medical applications, has named Michael R. Davin a former Altus Medical and Coherent Medical executive, as its new president and CEO. Davin will succeed Horace Furumoto, the company's founder, who is retiring.. . .EXFO Electro-Optical Engineering Inc. announced yesterday that its headquarters in Quebec City, Canada, as well as EXFO America in Texas, will each have a new address. As of September 15, all correspondence to EXFO's corporate headquarters should be sent to EXFO Electro-Optical Engineering Inc., 400 Godin Ave., Vanier (Quebec) G1M 2K2, Canada. The main telephone and fax numbers have not changed. As of September 16, all correspondence to EXFO America should be sent to EXFO America Inc., 4275 Kellway Circle, Suite 122, Addison, Texas 75001. The main telephone and fax numbers for EXFO America will now be the same as EXFO Gnubi's: 866-464-6824 (toll-free, Canada and the US), or 972-836-0100; fax: 972-836-0164.