Extension of Absolute Frequency Measurements to the cw He–Ne Laser at 88 THz (3.39 μ)

Abstract

The highest absolute frequency measurement yet reported is described. The frequency of the 3.39-μ line from a He–Ne laser oscillating at the methane absorption frequency was found to be 88.376245 (55) THz. The frequency was measured by beating the 88-THz radiation with the R(30) line from a cw CO2 laser and a 48-GHz klystron in a tungsten-on-nickel point-contact diode. The speed of light calculated from this frequency and previous wave-length measurements is in agreement with the accepted value and of comparable accuracy.