Frequency stabilization system

Claim 2

Apparatus for obtaining a discriminant which is a measure of the difference between the frequency of the output of a laser and a frequency standard o comprising: a. signal processing means for processing a portion of the laser output, said signal processing means including in series a frequency shifter for shifting the frequency of said portion of the laser output by a predetermined shifting frequency s and a modulator for frequency modulating said portion of the laser output with a modulating signal; b. an absorbing medium for partially absorbing the output of said signal processing means, said absorbing medium having an absorption profile with a peak value at a frequency a, where a is substantially equal to the sum (o +s); c. means for detecting the amplitude of the unabsorbed output of said absorbed output of said absorbing medium; and d. means for comparing the output of said detecting means with said modulating signal

Claim 3

The apparatus as defined by claim 1 wherein said predetermined frequency standard o is within the emission frequency band of the active medium of said laser.

Claim 4

The apparatus as defined by claim 2 further comprising a phase shifter for shifting the phase of said modulating signal before comparing it with the output of said detecting means.

Claim 5

The apparatus as defined by claim 2 wherein said absorbing medium contains iodine vapor.

Claim 6

The apparatus as defined by claim 4 wherein the active medium of said laser contains a mixture of neon and helium.

Claim 7

Apparatus for stabilizing the output frequency of a laser at a predetermined frequency o lying within the emission frequency band of the laser active medium comprising: a. signal processing means for processing a portion of the laser output, said signal processing means including in series a frequency shifter for shifting the frequency of said portion of the laser output by a predetermined shifting frequency omega s and a modulator for frequency modulating said portion of the laser output with a modulating signal; b. an absorbing medium for partially absorbing the output of said signal processing means, said absorbing medium having an absorption profile with a peak value at a freQuency a, where a is substantially equal to the sum (o +s); c. means for detecting the amplitude of the unabsorbed output of said absorbing medium; d. means for generating a discriminant by comparing the output of said detecting means with said modulating signal; and e. means for varying the output frequency of said laser in accordance with said discriminant.

Claim 8

Apparatus for stabilizing the output frequency of a laser at a predetermined frequency o lying within the emission frequency band of the laser active medium comprising: a. signal processing means for processing a portion of the laser output, said signal processing means including in series a frequency shifter for shifting the frequency of said portion of the laser output by a predetermined shifting frequency omega s and a modulator for frequency modulating said portion of the laser output with a modulating signal; b. an absorbing medium for partially absorbing the output of said signal processing means, said absorbing medium having an absorption profile with a peak value at a freQuency a, where a is substantially equal to the sum (o +s); c. means for detecting the amplitude of the unabsorbed output of said absorbing medium; d. means for generating a discriminant by comparing the output of said detecting means with said modulating signal; and e. means for varying the output frequency of said laser in accordance with said discriminant.

Claim 9

The apparatus as defined by claim 6 wherein said absorbing medium contains iodine vapor.

Claim 10

The apparatus as defined by claim 7 wherein the active medium of said laser contains a mixture of neon and helium.

Claim 11

Apparatus for stabilizing the output frequency of a laser at a predetermined frequency o lying within the emission frequency band of the laser active medium comprising: a. means for splitting the output beam of said laser into first and second portions; b. signal processing means for processing said first portion of the laser output, said signal processing means including in series a frequency shifter for shifting the frequency of said first portion of the laser output by a predetermined shifting frequency s and a modulator for modulating said portion of the laser output with a modulating signal; c. an absorbing medium for partially absorbing the output of said signal processing means, said absorbing medium having an absorption profile with a peak value at a frequency a, where a is substantially equal to the sum (o +s); d. a photodetector for detecting the unabsorbed output of said modulating signal; e. a phase shifter for shifting the phase of said modulating signal; f. a comparator coupled to the output of said phase shifter and the output of said photodetector; and g. means for varying the output frequency of said laser in accordance with the output of said comparator.

Claim 12

Apparatus for stabilizing the output frequency of a laser at a predetermined frequency o lying within the emission frequency band of the laser active medium comprising: a. means for splitting the output beam of said laser into first and second portions; b. signal processing means for processing said first portion of the laser output, said signal processing means including in series a frequency shifter for shifting the frequency of said first portion of the laser output by a predetermined shifting frequency s and a modulator for modulating said portion of the laser output with a modulating signal; c. an absorbing medium for partially absorbing the output of said signal processing means, said absorbing medium having an absorption profile with a peak value at a frequency a, where a is substantially equal to the sum (o +s); d. a photodetector for detecting the unabsorbed output of said modulating signal; e. a phase shifter for shifting the phase of said modulating signal; f. a comparator coupled to the output of said phase shifter and the output of said photodetector; and g. means for varying the output frequency of said laser in accordance with the output of said comparator.

Claim 13

The apparatus as defined by claim 9 wherein said absorbing medium contains iodine vapor.

Claim 14

The apparatus as defined by claim 10 wherein the active medium of said laser contains a mixture of neon and helium.