Optical frequency stabilizer and optical frequency selector

An optical frequency stabilizer comprising:

• a signal light source for outputting signal light of a frequency f.sub.s ;
• a frequency shifter having a pumping light source to emit pumping light of a frequency f.sub.p and producing converted signal light of a frequency 2f.sub.p -f.sub.s from said signal light supplied thereto;
• a frequency discriminator having such input/output characteristics that a peak frequency for giving a maximum or minimum of the output intensity is included, and converting a frequency change of said converted signal light into an intensity change and outputting the same therefrom;
• an optical detector supplied with the output light of said frequency discriminator and producing a detection signal of a level corresponding to the intensity of said output light;
• an oscillator for outputting a low-frequency signal of a frequency f.sub.m ;
• a modulation means for frequency-modulating said signal light source in accordance with said low-frequency signal;
• a frequency doubler for doubling the frequency of said low-frequency signal supplied thereto and outputting the double-frequency signal;
• a synchronous detection means connected operatively to both of said frequency doubler and said optical detector, and having specific output characteristic corresponding to the frequency differential of the input/output characteristics of said frequency discriminator;
• and
• a control means for controlling said pumping light source in such a manner as to maintain constant the output of said synchronous detection means.

An optical frequency selector comprising:

• a signal light source for outputting signal light of a frequency f.sub.s ;
• a frequency shifter having a pumping light source to emit pumping light of a frequency f.sub.p and producing converted signal light of a frequency 2f.sub.p -f.sub.s from said signal light supplied thereto;
• an optical filter supplied with said converted signal light and having specific band pass characteristic where a peak frequency for giving a maximum transmissivity is included, said band pass characteristic being variable on the frequency axis;
• a light branch means supplied with the output light of said optical filter and serving to branch the same into at least two;
• an optical detector supplied with one of the branched light and producing a detection signal of a level corresponding to the intensity of the supplied light;
• an oscillator for outputting a low-frequency signal of a frequency f.sub.m ;
• a modulation means for frequency-modulating said signal light source in accordance with said low-frequency signal;
• a synchronous detection means connected operatively to both of said oscillator and said optical detector, and having specific output characteristic corresponding to the frequency differential of the band pass characteristic of said optical filter;
• a scan means for scanning the band pass characteristic of said optical filter and halting its scanning operation in response to the output signal from said synchronous detection means;
• an inversion means for inverting the output characteristic of said synchronous detection means;
• and
• a control means for controlling the band pass characteristic of said optical filter in such a manner as to maintain constant the output of said synchronous detection means.