Frequency stabilization for two-mode laser

A frequency stabilization system for a laser having two modes oscillating in the same laser cavity with the beat frequency therebetween being dependent upon the frequency offset of the emission frequency of the oscillator from the center of the atomic gain curve, said system comprising:

• input means for receiving said beat frequency from said laser;
• timing means having an output related to said beat frequency;
• digital phase-sensitive integration means connected with said timing means and with said input means to receive said beat frequency therefrom, said digital integration means providing a digital output corresponding to the displacement of said emission frequency of said oscillator from the center of said atomic gain curve;
• transfer means connected with said timing means and with said digital integration means for controlling said digital output from said digital integration means;
• converter means connected with said transfer means to receive said digital output from said transfer means and responsive thereto providing an analog error-correction signal capable of causing adjustment of said emission frequency towards to the center of said atomic gain curve;
• and
• output means connected with said converter means to couple said error-correction signal from said system.

A stabilized two-mode laser, comprising:

• laser means having frequency adjusting means for adjusting the emission frequency of the output from said laser means, cavity means with two modes oscillating therein with the beat frequency between said two modes being dependent upon the frequency offset of said emission frequency from the center of the laser gain curve, and detector means for detecting said beat frequency;
• digital integration means for receiving said beat frequency from said detector means and providing therefrom a digital output indicative of the displacement of the emission frequency from the center of the laser gain curve;
• and
• converter means for receiving said digital output from said digital integration means and responsive thereto providing an analog error-correction signal, said converter means being connected with said frequency adjusting means for causing centering of said emission frequency with respect to the center of said laser gain curve.

A method for frequency stabilization of a laser providing an oscillator output frequency and having two modes oscillating in the same cavity, said method comprising:

• determining the beat frequency between said two modes oscillating in said cavity of said laser;
• digitally integrating said determined beat frequency with said digital integration result being indicative of the displacement of said oscilator frequency of said laser from the laser gain curve;
• converting said digital integration result to an analog error-correction signal;
• and
• utilizing said error-correction signal to adjust said oscillator output frequency.

A method for frequency stabilization of a laser providing an oscillator output frequency the adjustment of which is controlled by a piezoelectric element with said laser having two modes oscillating in the same cavity, said method comprising:

• determining the beat frequency between said two modes oscillating in said cavity of said laser, said beat frequency being dependent upon the frequency offset of said oscillator frequency from the center of the laser gain curve;
• applying the beat frequency to a reversible counter with the counter counting up during one-half cycle of the beat frequency counting down during the second half cycle of the beat frequency;
• strobing the count in said reversible counter into a latch at the end of each cycle of the beat frequency;
• converting the count in the latch to an analog error-correction signal;
• and
• applying the analog error-correction signal to said piezoelectric element of said laser to cause adjustment of the oscillator frequency towards the center of said laser gain curve.