Precise Wavelength Measurement of 543-nm Frequency Stabilized He-Ne Laser Using Optical Frequency Comb
Objective The precise wavelength measurement of a 543-nm He-Ne laser traditionally relies on iodine-stabilized 543-nm He-Ne laser as the wavelength reference source,which is used to measure the thermally stabilized 543-nm He-Ne laser wavelength via beat frequency beating method.Usually,thermally stabilized 543-nm He-Ne laser employs as a secondary laser wavelength standard,which is widely used in precise measurement.Furthermore,iodine-stabilized 543-nm He-Ne laser is the internationally recommended standard laser frequency reference with its relative standard uncertainty of 4.5×10-11.The iodine-stabilized 543-nm He-Ne laser utilizes the intracavity saturation absorption frequency stabilization method,requiring the insertion of the iodine cell into the laser resonant cavity.However,the gain of the Ne atom at 543 nm is notably low,approximately 1％of that at 633 nm.Consequently,the output power of the single longitudinal mode is limited,reaching only approximately 50 μW.Influences,such as mechanical drift,device aging,and other factors,can lead to detuning of the laser resonator cavity,and mismatches with the iodine cell.Hence,prolonged absence in light might be experienced by the 543-nm iodine-stabilized laser,compromising its utility as a laser wavelength reference.Thus,the development of a new wavelength measurement method for the 543-nm He-Ne laser is deemed essential.Methods In this study,a new method for accurately measuring the wavelength of the 543-nm He-Ne laser with an optical frequency comb is reported.This method employs offset locking technology to lock the 1086-nm distributed feedback single frequency fiber laser to the optical frequency comb.A frequency-stabilized 543-nm laser is generated by the nonlinear crystal PPLN via a frequency doubling process.The beat notes,detected via the generated CW 543 nm laser and measured 543-nm thermally stabilized He-Ne laser,can achieve accurate wavelength measurement of the measured laser.Results and Discussions The innovative approach for accurately measuring the wavelength of the 543-nm He-Ne laser using an optical frequency comb addresses the challenges of low output power and low signal-to-noise ratio typically observed in beat frequency measurements at 543 nm.Experimental data indicates a signal-to-noise ratio of 41 dB between the 1086-nm single-frequency fiber laser and optical frequency comb.After locking the 1086-nm laser,a frequency fluctuation range of 0.2 MHz is observed over 3 h,with a standard deviation of 0.03 MHz.A frequency jitter range of 1.3 MHz is noted between the 543-nm laser,produced by frequency doubling,and tested He-Ne laser,with a standard deviation of 0.2 MHz.The short-term(1 s)frequency stability and long-term(1000 s)frequency stability of the assessed 543-nm He-Ne laser outperform with values better than 2.1 × 10 10 and 1.1 × 10-10,respectively.These findings closely match the direct measurement outcomes of the iodine-stabilized laser,which exhibits a frequency difference of 2.9 MHz.Conclusions In this study,the method for precise wavelength measurement of 543-nm He-Ne laser via optical frequency comb is reported.This method utilizes offset locking technology to lock the 1086-nm single frequency fiber laser to the optical frequency comb.Furthermore,a frequency-stabilized 543 nm laser,generated via frequency doubling with a PPLN crystal,serves as the reference for gauging the wavelength of the thermally frequency-stabilized He-Ne laser.Within 3 h after offset locking,the beat frequency fluctuation range between the single-frequency fiber laser and optical frequency comb is 0.2 MHz,and the standard deviation is 0.03 MHz.The frequency jitter difference between the 543-nm laser,generated by frequency doubling,and measured thermally stabilized He-Ne laser is 1.3 MHz,standard deviation is 0.2 MHz,short-term(1 s)frequency stability is better than 2.1× 10-10,and long-term(1000 s)frequency stability is better than 1.1 ×10-10.This method measuring the wavelength of 543 nm is equivalent to the direct beat frequency measurement of iodine stabilized laser.In this method,the low-power 543-nm He-Ne frequency stabilized laser wavelength measurement is realized via frequency doubling.The link between continuous laser and optical frequency combs is established and the laser wavelength measurement is directly traced to the time and frequency reference,which effectively ensures the accuracy of the measurement results.
measurementmetrologylaser frequency stabilizationoptical frequency comb543 nm He-Ne frequency-stabilized laserlaser wavelength measurementoffset locking
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