Abstract
Torsional mode acousto-optic tunable filter (AOTF) is demonstrated using a metal-coated birefringent optical fiber for an improved robustness. The changes in acoustic and optical properties of a metal-coated birefringent optical fiber induced by the thin metal coating were analyzed experimentally and theoretically. The filter wavelength shift is successfully explained as a result of combined effect of acoustic wavelength change and optical birefringence change. We also demonstrated a small form-factor configuration by coiling the fiber with 6 cm diameter without performance degradation. The center wavelength of the filter can be tuned >35 nm by changing the applied frequency, and the coupling efficiency is higher than 92% with <5 nm 3-dB bandwidth.
Highlights
Acoustic wave is widely used to manipulate the properties of propagating light [1]
It should be noted that the thin metal coating would not be a sufficient protection against rough handling of the fiber compared to the conventional polymer coating
We present detailed experimental and theoretical analysis of the effect of silver coating in all-fiber acousto-optic tunable filter using torsional acoustic wave
Summary
Acoustic wave is widely used to manipulate the properties of propagating light [1]. In particular, the capability of coupling between spatial modes or orthogonal polarization modes in optical fiber has been utilized to demonstrate novel optical filters and lasers [2,3,4,5]. The use of highly birefringent, polarization maintaining fiber (PMF) makes this device insensitive to macro-bending because the optical birefringence induced by macro-bending is smaller than that of PMF by two to three orders of magnitude [7]. Exploiting these advantages, coiled version of torsional mode acousto-optic tunable filter (AOTF) was demonstrated to realize a small form factor [8]. We present detailed experimental and theoretical analysis of the effect of silver coating in all-fiber acousto-optic tunable filter using torsional acoustic wave. The successful demonstration of a small form factor AOTF by coiling the silver coated fiber is described as a potentially practical form of the device
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