A novel optical fiber current sensor for low-current measurements is proposed and tested. By winding a commonly used low-birefringence single-mode optical fiber in a special geometry, one can circumvent the bend-induced birefringence problem. Smaller sensors can now be built with a sensitivity that linearly increases with the number of fiber windings.

As discussed in the previous chapter, the so-called single-mode fibers in fact support two modes simultaneously, which are orthogonally polarized. In an ideal circular-core fiber, these two modes will propagate with the same phase velocity; however, practical fibers are not perfectly circularly symmetric. As a result, the two modes propagate with slightly different phase and group velocities. F...

We present detailed considerations on the achievable sensitivity in the measurement of birefringence using a high finesse optical cavity, emphasizing techniques based on frequency metrology. Alternative approaches of laser locking and cavity measurement techniques are discussed and demonstrated. High-precision measurements of the cavity mirror birefringence have led to the interesting observati...

A broadly tunable terahertz Solc-type birefringence filter is demonstrated. The first central passband frequency of the filter can be continuously tuned from 0.176 to 0.793 THz using magnetically controlled birefringence in nematic liquid crystals. The insertion loss of the present device is about 5 dB.

We demonstrate a universal cavity stabilization scheme that exploits the intrinsic birefringence of dielectric multilayer mirrors. Homodyne locking using weak mirror birefringence of even an empty Fabry-Perot-type cavity requires neither frequency modulation nor mixing and allows us to generate an error signal that is comparable to more widely used heterodyne stabilization schemes.

Birefringence phenomena stemming from vacuum polarization are revisited in the framework of coherent scattering. Based on photon-photon scattering, our analysis brings out the direct connection between this process and vacuum birefringence. We show how this procedure can be extended to the Kerr and the Cotton-Mouton birefringences in vacuum, thus providing a unified treatment of various polariz...

We reported an ultrahigh birefringence PCF with a germanium-doped elliptical core, which is fabricated in our lab using the stack-and-draw method, and an ultrahigh birefringence of 1.1×10 is obtained experimentally via FBG and Sagnac loop. OCIS codes: (060.2280) Fiber design and fabrication; (060.5295) Photonic crystal fibers; (060.3735) Fiber Bragg gratings