Artificially anisotropic core fiber with ultra-flat high birefringence profile

Stepniewski, G.; Kujawa, I.; Klimczak, M.; Martynkien, T.; Kasztelanic, R.; Borzycki, K.; Pysz, D.; Waddie, A.; Salski, B.; Stepien, R.; Taghizadeh, MR.; Buczynski, R.

Optical Materials Express

6 (5), 2016, 1464-1479, 10.1364/OME.6.001464

We present a highly birefringent fiber with a core made of artificial anisotropic glass material. The fiber core is composed of interleaved subwavelength layers of two types of soft glasses ordered in a rectangular structure. A pair of thermally matched glasses, a low refractive index borosilicate glass and a high refractive index lead oxide glass, are used. The fiber has a unique flat profile of birefringence over one octave, weakly dependent on wavelength. The group birefringence and effective mode area were measured in a broadband range across the visible and the near infrared for the fundamental mode and were found to be equal 1.8 × 10−3 and 20 μm2, respectively. The group birefringence is uniquely flat over the wavelength range of 0.8-1.7 μm and the relative difference of birefringence is below 0.2 × 10−3. The measured dispersion shows also relatively flat characteristics varying from −60 ps/(nm × km) at 1150 nm to 20 ps/(nm × km) at 1690 nm with Zero Dispersion Wavelength at 1520 nm. We demonstrated an application of the fiber for polarization maintaining broadband supercontinuum generation in the range of 1210-1830 nm when pumped with a subpicosecond fiber-based laser at 1560 nm.