Click to Enlarge
Image of an FEC5-1064 Ø5 mm end cap with tapered lead-in prepared for splicing in the GLZ4001EC CO₂ End Cap Splicer.

Features

• Ø1 mm, Ø1.5 mm, Ø5 mm, and Ø8 mm UV Fused Silica Coreless End Caps
• Tapered Lead-in Simplifies Splicing Fiber onto Large Diameter Caps
• Versions with 1064 nm VAR-Coated Face to Reduce Back Reflections
• >80% Clear Aperture with ≤5 arcsec Parallelism Between End Faces
• Protect Fiber End Face by Reducing Energy Density at Air-to-Glass Interface
• Ideal for High-Power Fiber Lasers and Amplifiers, Biomedical Imaging, and Protecting Photonic Crystal Fiber
• Splice onto Optical Fiber Using Our Vytran^® CO₂ End Cap Splicer

Thorlabs' UV fused silica end caps range in size from Ø1 mm to Ø8 mm. End caps with a 5 mm or 8 mm cap diameter have either a stem or tapered lead-in on one end to simplify splicing them onto a fiber; they also include a 1064 nm antireflection coating on the side opposite the taper to reduce back reflections. Complete specifications along with profiles and dimensions are in the table below.

Each end cap is coreless (no waveguide) to allow the incoming light to expand evenly in the homogeneous material. When spliced onto a fiber, the end cap reduces the intensity at the air-to-glass interface of the fiber face to prevent potential damage from high-power sources, such as Q-switched lasers or fiber amplifiers. End caps can also be used to seal off the air holes in photonic crystal fiber to prevent water from entering.

Application Note
These caps can be spliced onto optical fiber using our Vytran^® CO₂ End Cap Splicer. The GLZ4001EC Splicer is an advanced splicer that is designed for splicing numerous types of fiber directly onto a large-diameter end cap. Utilizing a tapered lead-in allows end caps up to Ø9.5 mm to be spliced, as shown in the image to the right. Without a lead-in the maximum end cap diameter is 5 mm.

Click to Enlarge
Coupling Light into and Out of Standard Fiber vs. End-Capped Fiber

Specifications
Item #	Profile (Click for Details)	AR Coatinga	Clear Aperture (Both Ends)	Surface Flatness (Both Ends)	Parallelism	Substrate	Dimensions (See Profile)
							DCap	LCap	LStem	θTaper
FEC1		N/A	>80%	≤λ/4 (633 nm)	≤5 arcsec	UV Fused Silica	1.0 mm	2.5 mm	N/A
FEC15							1.5 mm	3.8 mm
FEC5-1064		1064 nm V Coat (R < 0.25%, 0° ± 5° AOI)	>80%	≤λ/4 (633 nm)	≤5 arcsec		5.0 mm	12.5 mm	N/A	60°
FEC8S-1064							8.0 mm	20.0 mm	4.0 mm

• The antireflection coating is deposited on the side opposite the taper.