Low loss silica hollow core fibers for 3–4 μm spectral region

Abstract

We describe a silica hollow-core fiber for mid-infrared transmission with a minimum attenuation of 34 dB/km at 3050 nm wavelength. The design is based on the use of a negative curvature core wall. Similar fiber designed for longer wavelengths has a transmission band extending beyond 4 µm.

Revolver Hollow Core Optical Fibers

“…At longer wavelengths of around 5.8 and 7.7 μm the losses were measured to be 30 and 50 dB/m, respectively. Transmission bands at 3.3 and 4.3 μm have a number of absorption peaks, which are related to the absorption lines of HCl (similar to work [3]) and atmospheric CO2, respectively. Optical absorption of fused silica glass is also shown for comparison ( Figure 5, black curve).…”

“…In doing so, the capillaries can either touch each other (Figure 7a), or between the capillaries can be inserted additional elements at the beginning and at the end of the preform (Figure 7b). In the first case, a RF with touched capillaries [1] or an "ice-cream-cone" structure [3] is obtained. In the second case, it is possible to obtain a RF with non-touching capillaries [4].…”

“…Later, the abbreviation "NC HCF" became also to be applied to other fiber designs, such as Kagome HCFs with hypocycloid core-cladding boundary [2], and HCFs with "ice-cream-cone" shaped cladding [3]. However, RFs should be distinguished among other types of NC HCFs, because (1) the RFs provide an extremely low overlap of the optical mode with the cladding material and (2) RFs have very simple design of the cladding, which is based on a single layer of cylindrical or elliptical capillaries, and this fact enables new possibilities to optimize the fiber performance [4].…”

Exploring the Effect of the Core Boundary Curvature in Hollow Antiresonant Fibers

“…OLLOW antiresonant fibers (ARF) are emerging as attractive candidates for low-loss light guidance at near and mid-infrared wavelengths [1,2]. Their low optical nonlinearity and ultralow fraction of power carried in the glass result in a high damage threshold for ultrashort pulse delivery applications, while also placing less stringent demands on the transparency of the materials employed [3].…”

“…In Kagome-type hollow core fibers with a hypocycloid core surround, several studies have shown a dependency between the leakage loss of the fiber and its cladding structure [4,5], and recent works have already established that leakage loss can be significantly reduced when the curvature of the arcs forming the core boundary is increased [6][7][8], although no clear physical explanation has been provided for this behavior. A more recent family of hollow antiresonant fibers, already highlighted for its low loss in the infrared [2] and for its relatively low bending loss at large mode field diameters [5], consists of a simpler design in which the air-core is surrounded by a number of touching or non-touching circular capillaries [1,9]. These fiber types offer a better platform to try to understand the effect that the curvature of the membranes surrounding the core has on the overall loss, since different curvatures can be obtained while keeping unchanged key geometrical parameters [5,10].…”