Precision measurement and suppression of low-frequency noise in a current source with double-resonance alignment magnetometers

Low-noise high-stability current sources have essential applications such as neutron electric dipole moment measurement and high-stability magnetometers. Previous studies mainly focused on frequency noise above 0.1 Hz while less on the low-frequency noise/drift. We use double resonance alignment magnetometers(DRAMs) to measure and suppress the low-frequency noise of a homemade current source(CS) board. The CS board noise level is suppressed by about 10 times in the range of 0.001-0.1 Hz and is reduced to 100 n A/√Hz at 0.001 Hz. The relative stability of CS board can reach2.2 × 10^(-8). In addition, the DRAM shows a better resolution and accuracy than a commercial 7.5-digit multimeter when measuring our homemade CS board. Further, by combining the DRAM with a double resonance orientation magnetometer,we may realize a low-noise CS in the 0.001-1000 Hz range.

Off-resonant double-resonance optical-pumping spectra and their application in a multiphoton cesium magneto-optical trap

We present an investigation of double-resonance optical pumping （DROP） spectra under the condition of single-photon frequency detuning based on a cesium 6S1/2-6P3/2-8S1/2 ladder-type system with a room-temperature vapor cell. Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a coprop-agating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.

Double-resonance optical-pumping effect and laddertype electromagnetically induced transparency signal without Doppler background in cesium atomic vapour cell

In a Doppler-broadened ladder-type cesium atomic system （6S1/2 6P3/2-8S1/2）, this paper characterizes electro- magnetically induced transparency （EIT） in two different experimental arrangements, and investigates the influence of the double-resonance optical-pumping （DROP） effect on EIT in both arrangements. When the probe laser is weak, DROP is explicitly suppressed. When the probe laser is moderate, population of the intermediate level （6P3/2 FI = 5） is remarkable, therefore DROP is mixed with EIT. An interesting bimodal spectrum with the broad component due to DROP and the narrow part due to EIT has been clearly observed in cesium 6S1/2 F = 4-6P3/2 F^1= 5-8S1/2 F^11 = 4 transitions.

Detection of Radiocarbon Dioxide with Double-Resonance Absorption Spectroscopy

Fast and accurate quantitative detection of ^(14)CO_(2) has impor-tant applications in many elds.The optical detection method based on the sensitive cavity ring-down spectroscopy technol-ogy has great potential.But currently it has diffculties of insuffcient sensitivity and susceptibility to absorption of other isotopes/impurity molecules.We propose a stepped double-resonance spectroscopy method to excite ^(14)CO_(2) molecules to an intermediate vibrationally excited state,and use cavity ring-down spectroscopy to probe them.The two-photon process signi cantly improves the selectivity of detection.We derive the quantitative measurement capability of double-resonance absorption spectroscopy.The simulation results show that the double-resonance spectroscopy measurement is Doppler-free,thereby reducing the e ect of other molecular absorption.It is expected that this method can achieve high-selectivity detection of ^(14)CO_(2) at the sub-ppt level.

Realization of double resonance for a bright frequencytunable source of narrowband entangled photons

In this paper, we report an interesting phenomenon when precisely adjust the tuning crystal for double-resonance of a type-II configured parametric amplifier cavity, which is later verified as a cavity-enhanced effect in optics alignment. The theoretical result indicates that an angle accuracy error within 0.09° is necessary to achieve a high contrast ratio of 100：1 for a cavity with a finesse of about 205, which is crucial but high-demanding to get a high-quality narrowband entanglement source. Meanwhile, we figure out a method to release such a high requirement and get high visibility in a moderate-accuracy alignment.

Jahn-Teller Distortion of the Zinc Vacancy in ZnGeP2

A symmetry analysis and a simple dangling bond model are presented for the VZn^- in ZnGeP2, identifying a possible Jahn-Teller distortion mechanism which could naturally explain the localization of the defect wavefunction on two of the nearest-neighbouring P atoms, as deduced for the electron nuclear double resonance experiments.