IRF-S Series Chalcogenide Mid-IR Fiber

IRF-S 100

IRflex's nonlinear mid-infrared fiber (IRF), made from extra high purity chalcogenide glass, is specially designed and manufactured to generate and/or guide mid-wave infrared (MWIR) wavelengths of 1.5 to 11µm.  They are commercially available.

A suite of patents relating to chalcogenide glass based fiber optics has been licensed to IRflex from the U.S. Naval Research Laboratory (NRL).  These patent, in conjunction with IRflex’s experienced team, enable IRflex to find cutting-edge solutions to nonlinear mid-infrared applications.

Chalcogenide glass is made from a mixture of the chalcogenide elements: sulfur, selenium and tellurium.  It offers promising properties such as transmission in mid and far infrared regions of spectra, lower values of phonon energies, high refractive indices and very large nonlinearities as compared to silica, chalcogenide glass fibers are the ideal candidates for mid-infrared applications that require high power laser delivery, chemical sensing, thermal imaging and temperature monitoring.

IRflex's IRF-S Series mid-infrared fiber, made from extra high purity chalcogenide glass As2S3, is specially designed, and manufactured to generate and/or guide mid-infrared wavelengths from 1.5 to 6.5µm with high transmission efficiency and nonlinearities about 100 times that of silica glass fiber.

IRF-S-100 and IRF-S-200 multimode fibers have typical optical loss of 0.05dB@2.8µm and 0.08dB@4.8µm wavelength, which are the lowest loss in the market. The IRF-S-100 fiber was initially designed to use in high-power infrared countermeasure (IRCM) lasers for missile defense.

IRF-S-5, IRF-S-6.5, IRF-S-7 and IRF-S-9 singlemode fibers have transmission range from 1.5-6.5µm and minimum transmission loss of approximately 0.1dB/m at 4.8µm.  Given their approximately 5, 6.5, 7 and 9µm core diameters and 0.3 numerical aperture, the step-index fibers are truly single-mode for wavelengths larger than their 1.988, 2.46, 2.930 and 3.560µm cutoffs.  For wavelengths shorter than the cutoffs and with proper coupling, the transmitted beam could remain single-mode (or slightly multimode) over short length of fiber (< 2 m) for their entire fiber transmission range.

IRF-S-50 multimode fiber is developed to use for the fabrication of mid-infrared fused combiners.  The 50/85 µm core/clad design is ideal for making 7x1 fiber combiners having our IRF-S-100 as the output fiber.

All the fibers are commercially available and can be sold as bare fiber or terminated with connectors except IRF-S-5 as there is no ferrule of its size available in the market.

The standard fiber cables are terminated with stainless steel ferrules, FC/UPC, FC/APC or SMA905 connectors.  IRflex's FC/B® connector - the FC connector at Brewster Angle enables perfect coupling without reflection with polarized laser beam, is also available upon request.

The protective jacket can be stainless steel, stainless steel with PVC sheathing, PVDF or PVC. 

Other different cable assembling configurations are offered upon request.


  • Extra low loss, 0.05dB/m @2.8µm
  • High power handling strength, tested at IRflex with IRF-S-9, 3.7W CW in a 9µm core diameter fiber for 30 minutes without damage or degradation
  • High mechanical flexibility


  • Mid-IR Laser beam delivery
  • IR spectroscopy
  • Chemical sensing
  • Scientific and medical diagnostics IR-imaging system
  • Nonlinear supercontinuum generation
  • Infrared countermeasure (IRCM)

IRF-S Series

Fiber Models


Diameter (μm)


Diameter (μm)


Wavelength (μm)*

IRF-S-5 5 100 1.5 - 3
IRF-S-6.5 6.5 125 1.5 - 4.2
IRF-S-7 7 140 1.5 - 4.4
IRF-S-9 9 170 1.5 - 5.3
IRF-S-50 50 85 1.5 – 6.5
IRF-S-100 100 170 1.5 – 6.5
IRF-S-200 200 250 1.5– 6.5

Note:  * All these fibers will transmit from 1.5 to 6.5µm.  Operation Wavelength (µm) here means 50% more light remaining inside of the core.

Technical Specifications: 

Transmission Range (µm) 1.5 to 6.5
Typical Optical Loss (dB/m) 0.05 @ 2.8µm
Core/Clad Glass composition As2S3
Core Refractive Index 2.4
Numerical Aperture (NA) 0.28 - 0.30
Core Non-Circularity (%) <1
Core/Clad Concentricity Error (µm) <3
Tensile Proof Test (kpsi) >15