Low noise solid state laser

A low-noise laser comprising:

• a laser cavity;
• a birefringent gain crystal comprising Nd:YVO4 situated within said laser cavity, said gain crystal configured to have an approximately quarter-wave polarization retardance at said lasing wavelength;
• a nonlinear doubling crystal configured in a Type II arrangement to have approximately quarter-wave polarization retardance that, in conjunction with the birefringent gain crystal, provides a total single-pass retardance at said lasing wavelength that is substantially an odd multiple of one-half wave;
• and
• means for restricting the longitudinal lasing modes to substantially two lasing modes, including at least one of short cavity length, narrow gain curve, or an etalon;
• wherein said gain crystal and said doubling crystal are arranged so that the lasing state of said laser comprises two longitudinal modes each of which follows a different polarization pattern within said laser cavity.

A low-noise frequency-converted laser that outputs at least two longitudinal modes of low-noise frequency-converted laser light, comprising:

• a laser cavity;
• a birefringent gain crystal situated in said laser cavity;
• a frequency-conversion crystal situated within said laser cavity;
• a mode-selection system that substantially limits the number of longitudinal modes allowed to oscillate in said laser cavity;
• wherein said gain crystal and said frequency conversion crystal each have a nonzero polarization retardance at the fundamental emission wavelength, the sum of said polarization retardances selected to provide substantially two rotating longitudinal modes of fundamental laser emission within said gain crystal and thereby reduce spatial hole burning;
• and
• wherein said frequency-conversion crystal is arranged to frequency-convert said two fundamental longitudinal modes to create a low-noise frequency-doubled laser output that has substantially two longitudinal frequency-converted modes.

A method of generating a stable dual longitudinal mode laser emission in a solid state laser that includes a birefringent gain crystal within a laser cavity, comprising:

• generating a first longitudinal mode of fundamental laser emission that propagates along a first rotating polarization pattern within the gain crystal;
• generating a second longitudinal mode of fundamental laser emission that propogates along a second rotating polarization pattern within the gain crystal, said first and second polarization patterns limiting interaction between said first and second modes within the gain crystal, thereby reducing spatial hole burning;
• and
• frequency converting said first and second longitudinal modes of laser emission in a nonlinear crystal within the laser cavity to provide a stable, dual longitudinal mode freguency-converted output laser beam.