High-temperature stable fiber Bragg gratings with ultrastrong cladding modes written using the phase mask technique and an infrared femtosecond laser

Abstract

Bragg gratings with ultrastrong cladding modes are inscribed in a standard telecom optical fiber (i.e., SMF-28) using the phase mask technique and an infrared femtosecond laser. 1000°C-resistant fiber Bragg gratings (FBGs) whose cladding modes exceed 30 dB in transmission and spectrally span more than 250 nm can be produced with only a few (i.e., less than five) laser pulses, provided that the light intensity in the fiber core is kept at the level of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>6</mml:mn> </mml:mrow> <mml:mo>×</mml:mo> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>13</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">W</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mo>/</mml:mo> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mn>2</mml:mn> </mml:msup> </mml:mrow> </mml:math> . The use of FBGs fabricated under the above conditions for refractometry is demonstrated.