Microfiber-assisted gigahertz harmonic mode-locking in ultrafast fiber laser
Lin Huang, Yusheng Zhang, Yudong Cui, Jiangrong Qiu, Xueming Liu
Abstract
Optoacoustic interaction can be strongly enhanced in tiny core fibers, and it holds significant potential for stable harmonic mode-locking at gigahertz (GHz) and higher repetition rate. In this Letter, we propose and demonstrate a microfiber-assisted GHz harmonic mode-locking fiber laser, which is achieved by the enhanced optomechanical coupling between cavity modes in microfiber with the waist length 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>16</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">c</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> and the waist diameter 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>1.56</mml:mn> </mml:mrow> <mml:mspace width="thickmathspace"/> <mml:mtext>µ</mml:mtext> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> . The repetition rates can be stably locked at 2.3828 GHz and predominately locked at 1.7852 GHz, corresponding to the frequencies of radial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">R</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>01</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> and torsional-radial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msub> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi mathvariant="normal">T</mml:mi> <mml:mi mathvariant="normal">R</mml:mi> </mml:mrow> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mn>21</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> acoustic modes, respectively. Our results provide novel insight into the design of a high-repetition-rate laser source and the application of microfibers in the optomechanical field.