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Femtosecond laser writing of Bragg grating waveguide bundles in bulk glass

: Thiel, M.; Flachenecker, G.; Schade, W.


Optics Letters 40 (2015), Nr.7, S.1266-1269
ISSN: 0146-9592
Fraunhofer HHI ()

Waveguide bundles in bulk glass materials, consisting of several parallel scans of refractive index modifications, have been generated with a low-repetition femtosecond laser. Additionally, Bragg grating (BG) structures for 840 and 1550 nm have been introduced by segmentation of the central scan. A spectral loss in the transmission signal of >36 dB was achieved at 1550 nm with a second-order Bragg grating waveguide (BGW) in fused silica, which corresponds to an intrinsic grating efficiency of >16 dB/cm. This is to our knowledge the strongest BG structure realized in glass with a femtosecond laser. The BGW were proven to be stable up to a temperature of 250 degrees C in fused silica. The diameter of the waveguide bundles can be adapted very easily for a broad range of wavelengths and have been demonstrated for diameters between 1 and 50 mu m. The transmission properties of the waveguide bundles are affected minorly by the insertion of BG structures, which opens the ability for adjusting the BGW for a broad range of wavelength in single-mode or multimode optical circuits. BGW have been realized successfully in fused silica, borosilicate glass (BOROFLOAT 33), and AF 32 eco Thin Glass from Schott.