	US 7,532,791 B2
	Ultrafast laser machining system and method for forming diffractive structures in optical fibers
Jimmy Yi-Jie Jia, Cambridge, Mass. (US); Ming Li, Cambridge, Mass. (US); Rajminder Singh, Cambridge, Mass. (US); Xinbing Liu, Cambridge, Mass. (US); and Tetsuo Ohara, Cambridge, Mass. (US)
Assigned to Panasonic Corporation, Osaka (Japan)
Filed on Mar. 07, 2008, as Appl. No. 12/44,387.
Application 12/044387 is a division of application No. 11/213412, filed on Aug. 26, 2005, granted, now 7,366,378, filed on Apr. 29, 2008.
Claims priority of provisional application 60/623285, filed on Oct. 29, 2004.
Claims priority of provisional application 60/623286, filed on Oct. 29, 2004.
Prior Publication US 2008/0273836 A1, Nov. 06, 2008
Int. Cl. G02B 6/34 (2006.01)

U.S. Cl. 385—37

40 Claims

1. A method to form a diffractive structure in an optical fiber using an ultrafast laser machining system, the method comprising the steps of:

a) mounting the optical fiber in a fiber mount of the ultrafast laser machining system with a longitudinal axis of the optical fiber perpendicular to a beam path of a plurality of pulses of laser light of the ultrafast laser machining system;

b) illuminating a target region of the optical fiber with illumination light;

c) imaging the target region of the optical fiber with two digital cameras aligned in substantially orthogonal directions to produce pairs of substantially orthogonal alignment images of the target region of the optical fiber;

d) determining an initial position of a beam spot of the plurality of pulses of laser light formed by a focusing mechanism of the ultrafast laser machining system within the target region of the optical fiber;

e) aligning the beam spot to a starting position within the target region of the optical fiber, the starting position being within a portion of the optical fiber to be machined to form the diffractive structure for which the beam path of the plurality of pulses of laser light passes through a greatest length of material of the optical fiber to reach the beam spot;

f) scanning the beam spot along a machining path within the target region of the optical fiber, the machining path designed to pass the beam spot through all of the portion of the optical fiber to be machined to form the diffractive structure such that the beam path of the plurality of pulses of laser light does not pass through previously machined material of the optical fiber; and

g) generating the plurality of pulses of laser light having a duration of less than about 1 ns to machine material of the optical fiber as the beam spot is scanned in step (f), thereby forming the diffractive structure within the optical fiber.