Performance and Limitations of Iodine Stabilized Lasers
The 127I2 stabilized laser has now reached the stage of development where a reproducibility of better than 20 kHz (∆v/v = 4x10−11) may consistently be achieved between lasers which operate at the same iodine temperature. The purpose of this paper is to report the present reproducibility and performance of the NPL lasers, to suggest the likely limitations of the present systems, and to indicate possibilities for further improvement. Both 127 and 129 iodine isotope lasers have been built using third harmonic (3f) servocontrols, which have high Q rejection filters for f and 2f signals and a low Q 3f band-pass filter between the photoamplifier detector and phase sensitive detector (psd). This arrangement avoids problems in the electronic servosystem due to the large fundamental and second harmonic components which are present in the amplifier signal and which might become rectified in the psd to give rise to a frequency offset (1). The 127 lasers operate with an iodine temperature of 18 ± 0.05 °C which results in maximum height saturated absorption features on the laser power output for these lasers. At temperatures both above and below this, the peak size either decreases or remains constant.
KeywordsBeat Frequency Laser Power Output Phase Sensitive Detector Power Shift Quantum Metrology
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