Narrow Linewidth 1064 nm Laser Diode With External Distributed Feedback

We demonstrate a narrow linewidth 1064 nm DFB laser diode by employing a piece of Rayleigh scattering enhanced fiber to provide distributed feedback. Introducing local defects in the high numerical aperture fiber with femtosecond laser micromachining enhances Rayleigh scattering by 60.23 dB in comparison with standard single-mode fiber in common use. Based on the external distributed feedback from the Rayleigh scattering enhanced fiber with a length of 3 m, a 1064 nm laser diode with an intrinsic linewidth of 94 Hz, a frequency noise of 3.85 Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/Hz@1MHz, and a side-mode suppression ratio of 83.98 dB was experimentally demonstrated. More interesting is that such a narrow linewidth laser diode can operate at any wavelength within its tuning range due to the wavelength self-adaptivity of the Rayleigh scattering based distributed feedback. The work demonstrated here provides a method for miniaturized and integrated narrow linewidth lasers with continuous wavelength tunability.