Laser oscillation frequency stabilizer

A laser oscillation frequency stabilizer comprising:

• a laser light source portion including a laser light source configured to have a controlled oscillation frequency and to emit a laser beam;
• a polarized beam splitter portion configured to split the laser beam from said laser light source portion into two laser beams, each of said two laser beams having linearly polarized components orthogonal to each other;
• a quarter wavelength plate configured to form from the two laser beams, split by way of said polarized beam splitter portion, circularly polarized first and second laser beams, the circularly polarized first and second laser beams being polarized in an opposite direction to each other;
• an absorption cell disposed in an optical path of the circularly polarized first and second laser beams, sealed therein with gaseous atoms or molecules having a certain absorption spectrum, and configured to have a uniform magnetic field applied thereto;
• a half mirror disposed in the optical path of the circularly polarized first and second laser beams after the absorption cell, configured to reflect partially the circularly polarized first and second laser beams back in an opposite direction through said absorption cell and onto said quarter wavelength plate to form linearly polarized third and fourth laser beams, and configured to transmit partially the circularly polarized first and second laser beams;
• a first light-receiving portion configured to receive the partially transmitted circularly polarized first laser beam;
• a second light-receiving portion configured to receive the partially transmitted circularly polarized second laser beam;
• a third light-receiving portion configured to receive the linearly polarized third laser beam;
• a fourth light-receiving portion configured to receive the linearly polarized fourth laser beam;
• and
• a control portion configured to controllably lock the oscillation frequency of said laser light source to said absorption spectrum in accordance with transmitted light reception levels provided by said first to fourth light-receiving portions,
• said control portion including,
• a first divider configured to produce a ratio between a light reception level of said first light-receiving portion and a light reception level of said third light-receiving portion,
• a second divider configured to produce a ratio between a light reception level of said second light-receiving portion and a light reception level of said fourth light-receiving portion,
• a subtracter configured to accept outputs of said first and second dividers and to output a difference therebetween as an error signal, and
• a current control circuit configured to control current to the laser light source in accordance with the error signal of said subtracter so that an oscillation frequency of said laser light source coincides with said absorption spectrum.