Lensed fiber with high refractive index lens

Lensed fiber is an optical fiber with the tip shaped like a lens. Lensed fibers are used in integrated optics, optical trapping, and fiber sensors. Lens fiber creates a tight focal spot at some distance away from the fiber edge. This tight focal spot can be used to couple light into an optical chip, or collect light from a laser diode or even trap a microparticle. Conventional lensed fibers are made using polishing, laser cutting or plasma arc. All these techniques restrict the shape and material of the lens, which limits the performance and potential applications. Using our fiber nanoimprint technology we were able to remove these constraints. Our lensed fibers have free-form lenses that are made out of high refractive index materials.

Lensed fiber SEM
SEM image of a lensed fiber with nanoimprinted lens out of high refractive index material
High refractive index lens on a fiber
SEM image of the high refractive index Fresnel lens on a fiber

 

Free-form lenses create a great flexibility in the optical design. As a result, not only our lensed fiber have a near diffraction-limited performance, but we can engineer the focal spot to be any shape, rather than just circular. For example, an elliptical shape of the focal spot can be used to increase light collection efficiency from laser diodes with an elliptical mode. The material of the lens is of significant importance as well. It is the first commercial fiber lens that can be effectively used for immersion applications. This became possible through the use of our patented (US20160109799A1) custom high refractive index material. While regular lensed fiber loses it’s focusing ability inside adhesive due to the insufficient refractive index contrast, the imprinted lens can still focus light into the spot with ~800 nm in diameter. In fact, using immersion with our lenses even decreases the focal spot diameter while at the same time reducing light reflection!

Optical measurements of a lensed fiber inside immersion
Measurements of the lens focusing ability inside immersion liquid with the refractive index of 1.51. Focal spot diameter is 810 nm @1/e² for 660 nm wavelength. To our knowledge, our lenses are the only fiber lenses in the world that can focus light in the liquids or adhesives.

Applications:

  • Immersion applications
  • Laser-to-fiber coupling
  • Integrated optics
  • Optical trapping
  • Biosensors
  • Material processing

Advantages of our lensed fiber:

  • Near diffraction-limited focal spot
  • Elliptical or circular focal spot options
  • High refractive index
  • Immersion compatible
  • Highly reproducible

Download fiber lens specification

Download our paper on high refractive index fiber Fresnel lens

Contact us to purchase lensed fibers or to customize them for your application!