We propose a novel way of radiation wavelength stabilisation in atomic clocks based on coherent population trapping (CPT). It uses quadrature-phase component of the CPT signal within the CPT resonance feedback loop and automatic wavelength locking of radiation from a VCSEL to the atomic absorption line. We demonstrate advantages and limitations of the new method applied to vapour cells with buffer gas or anti-relaxation coating. Also provided are measurements of short- and long-term stability of a CPT-based atomic clock using the proposed method with various optical cells. Discussed are the prospects of this method in chip-scale atomic clocks.
The present work for the first time presents the study of a laser system delivering into the fibre up to 250 mW of CW radiation tuneable across the 275–310-nm range with the output line width less than 5 GHz and stability of UV output power within 1%. This system can automatically set the output radiation wavelength within the range of 275–310 nm to the precision of 2 pm. UV output power stabilisation is provided by a newly proposed by the authors noise eating technology. This paper discusses details of the developed technology and the results of its application.
The present work presents a new method for enhancement of contrast of coherent population trapping resonance in Rb vapour based on feedback and fast digital processing of the error signal in the feedback loop. In the proposed method, when the frequency difference between the pump field components is detuned from the resonance of coherent population trapping, a linear combination of two measured values, — pump field power prior and after passing through the cell, — is stabilised. This parameter combination is stabilised through adjustment of the pump radiation power with an electrooptical amplitude modulator. The studied method is shown to improve CPT resonance contrast by more than two orders of magnitude, while also improving the signal-to-noise ratio more than two-fold. The possibilities and limitations of the proposed method for enhancement of CPT resonance contrast are analysed.