Ultra-high stability brillouin fiber laser

A Brillouin laser comprising:

• a source of pump light having at least three different pump frequencies;
• and
• a nonlinear cavity configured to receive the pump light and to generate at least three frequency-downshifted Brillouin laser outputs, wherein two frequency-downshifted Brillouin laser outputs of the at least three frequency-downshifted Brillouin laser outputs have polarizations that are orthogonal to one another and two frequency-downshifted Brillouin laser outputs of the at least three frequency-downshifted Brillouin laser outputs have polarizations that are equal to one another,
• wherein the two frequency-downshifted Brillouin laser outputs having polarizations that are orthogonal to one another are configured to reduce temperature-induced frequency fluctuations of at least one Brillouin laser output of the at least three frequency-downshifted Brillouin laser outputs, and the two frequency-downshifted Brillouin laser outputs having equal polarizations are configured to reduce acceleration or acoustic noise-induced frequency fluctuations of at least one Brillouin laser output of the at least three frequency-downshifted Brillouin laser outputs.

An apparatus comprising:

• a bi-directional Brillouin fiber laser comprising polarization maintaining fiber and generating Brillouin oscillation along two propagation directions;
• an intra-cavity coupler configured to provide coupling of two laser signals having the two propagation directions;
• and
• at least one pump laser resonantly coupled to the bi-directional Brillouin fiber laser, wherein the bi-directional Brillouin fiber laser has a cavity length greater than 200 m, and wherein at least one output of the bi-directional Brillouin fiber laser is in a fundamental longitudinal mode with a power contrast ratio greater than 30 dB between a power of the fundamental longitudinal mode and any higher-order modes.

A Brillouin fiber laser comprising:

• a first loop of polarization maintaining fiber and having a first fiber length;
• a second loop of polarization maintaining fiber, the second loop having a second fiber length and nested within the first fiber length of the first loop, a ratio of the first fiber length to the second fiber length being at least 10;
• and
• at least one pump laser coupled to the first loop, wherein at least one output of the Brillouin fiber laser is in a fundamental longitudinal mode with a power contrast ratio greater than 30 dB between a power of the fundamental longitudinal mode and any higher-order modes.