Fibre-grating-stabilized diode laser

A pigtailed diode laser for producing multiple longitudinal modes, comprising:

• a diode laser that emits light in substantially a single spatial mode and which includes a diode lasing cavity and an output facet defining an end of the diode lasing cavity, and which lases in multiple longitudinal modes within the lasing cavity in the absence of external optical feedback;
• an optical fibre including a guided wave portion of the fibre which is capable of sustaining at least one mode at the wavelength of the diode laser;
• means for directing the emitted light from the diode laser into the optical fibre;
• a fibre Bragg grating in the guided wave portion of the fibre and having a reflection bandwidth;
• and,
• said output facet having a reflectivity approximately equal to or greater than that of the fibre Bragg grating,
• wherein the reflected light from the fibre Bragg grating into the diode lasing cavity limits the bandwidth of lasing to a value less than or equal to the reflection bandwidth of the grating and induces lasing in multiple longitudinal modes of the external cavity formed by the fibre Bragg grating and the output facet of the diode laser whereby to enhance the stability of the optical spectrum and intensity of the diode laser relative to the operation of said laser in the absence of optical feedback from said grating.

Apparatus for generating a stable laser source having single longitudinal mode linewidth operation, comprising:

• a diode laser that emits light in substantially a single spatial mode and which includes a diode lasing cavity and an output facet defining an end of the diode lasing cavity, and which lases in multiple longitudinal modes within the lasing cavity in the absence of external optical feedback;
• an optical fibre including a guided wave portion of the fibre which is capable of sustaining at least one mode at the wavelength of the diode laser;
• means for directing the emitted light from the diode laser into the optical fibre;
• a fibre Bragg grating in the guided wave portion of the fibre and having a reflection bandwidth;
• and,
• said output facet having a reflectivity approximately equal to or greater than that of the fibre Bragg grating, and wherein the optical distance between the exit facet of the diode laser and the fibre Bragg grating is less than the coherence length of the optical output of the diode laser,
• wherein the reflected light from the fibre Bragg grating into the diode lasing cavity limits the bandwidth of lasing to single longitudinal mode linewidth operation.