A laser Diode (LD) driver with constant current and temperature control system is designed according to the LD working characteristics. We deeply researched the protection circuit and temperature control circuit based on thermos-electric cooler(TEC) cooling circuit and PID algorithm. The driver could realize constant current output and achieve stable temperature control of LD. Real-time feedback control method was adopted in the temperature control system to make LD work on its best temperature point. The output power variety and output wavelength shift of LD caused by current and temperature instability were decreased. Furthermore, the driving current and working temperature is adjustable according to specific requirements. The experiment result showed that the developed LD driver meets the characteristics of LD.
KEYWORDS: Magnetism, Chemical species, Gyroscopes, Polarization, Time metrology, Xenon, Rubidium, Signal to noise ratio, Signal detection, Signal processing
In a nuclear-magnetic-resonance gyroscope (NMRG), the polarization of nuclear spins and the detection of motional
information are usually achieved by utilizing the atomic spins of alkali atoms. The parameters of the atomic spins are
mainly evaluated by the relaxation time. Relaxation time is very important and can influence signal-to-noise ratio,
dynamic range, start time, and other gyroscope parameters. Therefore, its accurate measurement is critical in the study of
NMRG performance. In this study, we evaluate a variety of methods to measure the transverse and longitudinal
relaxation times. First we examine the free-induction-decay method, which is the industry standard for measuring spin
relaxation time. Second we investigate the improved free-induction-decay, fitting-ratio, and magnetic-resonance-broadening-
fitting methods for measuring the transverse relaxation time, and the flipped polarization method for
measuring the longitudinal relaxation time. By changing the experimental conditions, we obtain the longitudinal
relaxation time using the flipped polarization method under a variety of conditions. Finally, by comparing these
measurement methods, we propose the best measurement methods under different conditions.
A new method and its principle are presented for measuring the each component gas pressures in Rubidium (Rb) by the analysis of absorption spectral profile. The experiment system is set up to obtain Rb absorption spectra. And then each component gas pressures in atom vapor cell is estimated. First, the relationships between transmittance of probe light, atom density and absorption cross section are introduced, and the factors which influence the absorption spectral profile and methods to measure gas pressures are given. Second, the frequency-dependence curves of transmittance and the absorption spectra are obtained through tuning the laser frequency through the Rb D1 transition. Finally, the gas pressures of Rb, N2 and He are achieved, through fitting absorption spectral profile referring to half-width and minimum transmittance value of absorption spectra. The experiment results show that gas pressures in Rb atom vapor cell can be accurately measured by absorption spectrometric methods, which will be helpful for the following study of atom vapor cell. The gas pressures of N2 and He measured by the experiments are well matched with design values. The Rb gas pressure is 30%~50% less than the saturated vapor pressure and the suppression may be due to the adsorption of the cell surfaces coated with octadecyltrichlorosilane (OTS) film.
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