Integrated Imaging Fiber Optics with Multiple Grin Lenses

Design and fabrication of an integrated imaging fiber optic probe (IFOP) (comprising a monomode optical fiber which is fusion spliced to a short length of a graded index multimode fiber) for delivery of either a collimated beam or a focused spot to a remote location, has been reported earlier.1 A short section of a multimode graded index fiber (GFL) with quadratic index profile has focusing properties similar to those of spherical lenses and Sclfoc2 graded index lenses manufactured by NSG2. Advantages of GFL over Selfoc lenses include miniaturization, narrower beam delivery for a certain distance and alignment-free lens system since the GFL is fused to the monomode fiber. Applications in areas such as photon correlation spectroscopy3 and fiber optic connectors4 have been evaluated. Variations in the image distance and magnification can be obtained by controlling the length of the GFL and is limited by the properties (namely the refractive index profile) of the GFL under use.