Gao Jiang-rui

The next detectors for gravitational wave astronomy

This paper focuses on the next detectors for gravitational wave astronomy which will be required after the current ground based detectors have completed their initial observations, and probably achieved the first direct detection of gravitational waves. The next detectors will need to have greater sensitivity, while also enabling the world array of detectors to have improved angular resolution to allow localisation of signal sources. Sect. 1 of this paper begins by reviewing proposals for the next ground based detectors, and presents an analysis of the sensitivity of an 8 km armlength detector, which is proposed as a safe and cost-effective means to attain a 4-fold improvement in sensitivity. The scientific benefits of creating a pair of such detectors in China and Australia is emphasised. Sect. 2 of this paper discusses the high performance suspension systems for test masses that will be an essential component for future detectors, while sect. 3 discusses solutions to the problem of Newtonian noise which arise from fluctuations in gravity gradient forces acting on test masses. Such gravitational perturbations cannot be shielded, and set limits to low frequency sensitivity unless measured and suppressed. Sects. 4 and 5 address critical operational technologies that will be ongoing issues in future detectors. Sect. 4 addresses the design of thermal compensation systems needed in all high optical power interferometers operating at room temperature. Parametric instability control is addressed in sect. 5. Only recently proven to occur in Advanced LIGO, parametric instability phenomenon brings both risks and opportunities for future detectors. The path to future enhancements of detectors will come from quantum measurement technologies. Sect. 6 focuses on the use of optomechanical devices for obtaining enhanced sensitivity, while sect. 7 reviews a range of quantum measurement options.

Intracavity frequency-doubled and stabilized cw ring Nd:YAG laser with a pair of KTP crystals

Generation of an up to 1.5-W single-frequency and a 650-mW frequency-stabilized second harmonic at 1.06 µm has been demonstrated in a cw ring Nd:YAG laser with a pair of properly oriented KTP crystals in which the walk off between the intracavity modes has been eliminated. The frequency stability is better than 5 MHz for the second-harmonic output level of 650 mW. The fluctuation of power is less than 4%. PACS: 42.60. By. 42.65 Ky.

Noise Suppression of a Single Frequency Fiber Laser

We present an experimental demonstration of fiber laser noise suppression by the mode cleaner. The intensity noise of a single frequency fiber laser is suppressed near the shot noise limit after a sideband frequency of 3 MHz. Two series mode cleaners are used to improve the noise suppression. The noise reduction is over 27 dB at 3 MHz.

Experimental Generation of Multimode Squeezing in an Optical Parametric Amplifier

We experimentally demonstrate that HG01 (Hermit—Gauss) and HG10 squeezed states can be generated simultaneously in an optical parametric amplifier. The HG01 mode is a bright squeezed state and the HG10 mode is a vacuum squeezed state. The squeezing of the HG01 mode is −2.8 dB, and the squeezing of the HG10 mode is −1.6 dB. We also demonstrate that the output field is also continuous-variable entanglement with orbital angular momentum.

Comparison of the Noise Properties of Squeezed Probe Light in Optically Thick and Thin Quantum Coherence Media for Weak and Strong Coupling Lights

The output amplitude noises of one squeezed probe light which is at resonance throughout different optical depths media in strong- and weak-coupling-field regimes are investigated theoretically. By comparing the output quantum noises for different Rabi frequencies of coupling field and also for different optical depths, it is found that the optimal squeezing preservation of the probe light occurs in an optically thin medium with strong-coupling-field, where we can obtain the output squeezing close to the input one at nonzero detection frequency.

Experimental Demonstration of a Displacement Measurement of an Optical Beam beyond the Quantum Noise Limit

We experimentally generate a spatially squeezed light beam and realize a small-displacement measurement beyond the quantum noise limit with this squeezed light. Moreover, we measure about −2.2±0.2 dB spatial squeezing and reduce the minimum measurable displacement from 1.17 A to 0.99 A with the signal-to-noise ratio normalized to 1.

Controllable optical mirror of cesium atoms with four-wave mixing

The controllable optical mirror is experimentally accomplished in a λ-type three-level atomic system coupled with standing wave. It is shown that the reflection of probe light results from electromagnetically-induced-transparency-based four-wave mixing, therefore the reflection efficiency is highly dependent on the angle for phase matching condition between the probe and coupling fields. The measured reflection spectra show good agreement with dispersion compensation theory.

Realization of stimulated emission-based detector and its application to antinormally ordered photodetection

Using a stimulated parametric down-conversion process combined with a conventional detector, we theoretically propose a scheme to realize the stimulated emission-based detector, and investigate the antinormally ordered correlation function and Fano factor for the coherent eld based on it. Such a detection has advantages over the normally ordered one especially when the intensity of the eld is weak.

Quantum coherent effects in multi-Zeeman-sublevel atomic systems

This paper reports the experimental results on electromagnetically induced absorption (EIA) spectra observed in the system which does not satisfy completely the conditions given by Lezama et al [1999 Phys. Rev. A 59 4732]. EIA signals on the transitions in the Cs D2 line are able to be observed, where Fg ↔ Fe = Fg — 1 as open systems. Theoretical model of Lezama et al is good for the case Fg ↔ Fe = Fg + 1, considering spontaneous transfer of atomic coherences or populations this model is not able to explain our experimental results obtained in the case Fg ↔ Fe = Fg — 1. This paper offers a theoretical model which is able to well explain the case Fg ↔ Fe = Fg — 1. It also uses this theoretical model to explain the split and shift of EIA peaks, which have been obtained in experiments.

Quantum noise property in coherent atomic system

The coherent superposition of atomic states leads to the characteristic change of interacting lights because of the coupling between the lights and atoms. In this paper, the noise spectrum of the quantified light interacting with the atoms is studied under the condition of electromagnetically induced transparency (EIT). It is shown that the noise spectrum displays a double M-shape noise profile resulted from the conversion of phase noise of probe beam. A squeezing of 0.3 dB can be observed at the detuning of probe light at the proper parameters of atoms and coupling beam.