Tunable narrowband external-cavity diode laser with an embedded fiber grating reflector

With the continuing development of coherent and multiplexed fiber systems, there is a need for compact, narrowline and efficient external cavity diode lasers that are broadly tunable. To this end, we have developed a new narrowline tunable laser in which the external cavity is formed by a fiber which contains an embedded Bragg grating reflector. This grating is formed holographically in the fiber core by a noninvasive technique. Relative to similar approaches that use a grating formed photolithographically on a polished fiber, this approach provides a grating with high environmental robustness, ease of fabrication and ease of tunability. Initial devices have utilized a multi-mode laser and achieved linewidths of 200 kHz and tunability over 2nm.