Broadband single-mode operation of standard optical fibers by using a sub-wavelength optical wire filter

Abstract

Abstract:We report the use of a sub-wavelength optical wire (SOW) with a specifically designed transition region as an efficient tool to filter higherorder modes in multimode waveguides. Higher-order modes are effectively suppressed by controlling the transition taper profile and the diameter of the sub-wavelength optical wire. As a practical example, single-mode operation of a standard telecom optical fiber over a broad spectral window (400~1700 nm) was demonstrated with a 1μm SOW. The ability to obtain robust and stable single-mode operation over a very broad range of wavelengths offers new possibilities for mode control within fiber devices and is relevant to a range of application sectors including high performance fiber lasers, sensors, photolithography, and optical coherence tomography systems.

Comparative study of the effective single mode operational bandwidth in sub-wavelength optical wires and conventional single-mode fibers

“…As described in reference 7, the higher-order modes present at the input fiber can be effectively suppressed by controlling the biconical taper transition profile (by ensuring an adiabatic transition for LP 01 but non-adiabatic transition for higher-order modes) and the diameter of the SOW in the waist region. This suppresses the propagation of higherorder modes along the entire length of the SOW and constrains the number of guided modes [7]. As shown in Fig.…”

“…Furthermore, the reduced core diameter and numerical aperture dictate the need for high-precision core alignment processes when splicing and can result in both fiber handling and power penalty problems within many practical applications. The authors have recently proposed and successfully demonstrated the use of extremely thin sub-wavelength optical wires (SOWs) [4][5][6] as an efficient way to provide higher-order mode filtering in multimode waveguides [7,8] and have shown that this can be used to obtain broadband single-mode operation of a fiber at short wavelengths, or over a wide range of wavelengths. The approach relies simply on filtering higher order modes in a multimode waveguide by integrating a single-mode SOW section within the fiber which incorporates specific taper transitions (adiabatic for fundamental mode but non-adiabatic for higher-order modes) that minimize re-excitation of the filtered modes.…”

Efficient sub-wavelength light confinement using surface plasmon polaritons in tapered fibers

“…Coupling optimization was achieved using a xyz stage. A micro-wire modal filter [17] was inserted before the sample: although the fiber second mode cut-off was at 730 nm, the filter ensured that no power was propagating in the second mode at any wavelength. In fact high order modes have different effective indices, thus SPP excitation occurs at different resonance conditions (Eq.…”

A microfiber coupler tip thermometer

“…1(b)) is presented. Since a seminal paper was published in 2003 [13], optical microfibers and their related devices have attracted increasing attention because of their wide range of applications which include, amongst others sensors [14,15], particle manipulation [16] and modal filters [17]. In 2009, Jung et al [18] demonstrated a broadband singlemode bi-conical 2×2 microfiber coupler (MFC, Fig.…”