Generation Of Qudrature Squeezing Resonant On The Cesium D1 Line

Non-classical light corresponding to alkali metal atoms absorption lines are important resources for many applications,such as ultra-precise measurement,light-atom interaction,atomic entanglement generation,and quantum memory.Specially,it's a major ingredient part of quantum network.Such a network consists of atoms as the quantum nodes and non-classical light as the interconnecting channels for transmitting information between spatially remote notes.Hence,non-classical light that can be precisely tuned to match the atomic transition is the key part of quantum network.One of the methods to generate non-classical light corresponding to alkali atoms absorption line is by parametric down conversion.So far,generation of non-classical light by parametric down conversion are mainly focus on cesium(Cs)D2 line and rubidium D1 line.Particularly,the Cs D1 line at 894.6 nm has the advantage of simplified hyperfine structure for experimentally realization of an light-atom interface,and it also lies well within the wavelength regime of excitonic transition in InAs quantum dot for integrated quantum interface between light and solid-state system.Even we obtained-2.5 dB of relative intensity squeezing at 894.6 nm,however,the squeezing level is not high due to a large energy level splitting,which limits the applications of squeezed light.It's a key part of atom-light interface in quantum networks for large-scale quantum information process.So far,there is no report on generation of squeezing light at this wavelength.This paper mainly introduce the generation of squeezed light at 894.6nm during the period of study for my doctorate.This article mainly consists of the following four parts: 1.We simply review the development of quantum optics,and give the five basic assumptions of quantum mechaincs,and then we introduces the definition and the classification of squeezed light.2.We developed a continuous-wave single-frequency tunable laser at 447.3 nm by frequency doubling of a tapered amplifier-boosted continuous-wave diode laser at 864.6 nm(cesium D1 line).We obtained 178 mW blue laser and the corresponding conversion efficiency is 50.8%.The blue laser can be continuously tuned 1.6 GHz as the frequency of diode laser is scanned 0.8 GHz.3.We generate the vacuum squeezed light at 894.6 nm with a continuous-wave degenerate optical parametric oscillator,which is pumped by 447.3 nm laser generated by frequency doubling of 894.6 nm infrared laser.The SHG cavity consists of a PPKTP crystal and a two-mirror standing-wave cavity,and we obtained 45 mW blue laser when the incident laser is 150 mW.The OPO consists of a two-mirrors standing-wave cavity and a PPKTP crystal.The threshold of the optical parametric oscillator is 39 mW.We obtained 2.8 dB vacuum squeezing when the incident pump power is 30 mW.The actual squeezing is 4.4 dB when taking into account the overall detection efficiency.4.We report the experimental generation of-4.1 dB quadrature vacuum squeezing resonant on the cesium D1 line(894.6 nm)by using a subthreshold continuous-wave pumped half-monolithic degenerate squeezing resonator with a type-I PPKTP crystal as the nonlinear optical medium.When the resonator is run as an OPA,the generated bright squeezed light can be continuously tuned around 50 MHz.The generated squeezed light source has potential applications in constructing quantum light-atom interface in quantum networks.The creative works are as follows: 1.We use the diode laser system as the light source,so the cost is low and the output power is high.The frequency doubling cavity is a two-mirror standing wave cavity,which has less mirrors than the ring cavity,leading to a low intra-cavity loss and relatively high conversion efficiency of 50.8%.The system is compact and stable,the RMS fluctuation is 2.3% in 2 hours at the mode-matched incident power of 350 mW.The generated blue laser can be continuously tuned about 1.6 GHz without losing the lock of the cavity when the infrared laser is tuned 0.8 GHz.2.One of the methods to generate non-classical light corresponding to Cesium D1 line is atomic ensemble-based four-wave mixing process,however,the squeezing level is not high due to a large energy level splitting.Another effective way to prepare non-classical light is by parametric down conversion.We first prepare the vacuum squeezed light at cesium D1 line with continuous-wave quasi-phase-matching degenerate optical parametric oscillator and obtain 2.8 dB vacuum squeezing.3.We obtained 4.1 dB vacuum squeezing at cesium D1 line by using a subthreshold continuous-wave(cw)pumped half-monolithic OPO.When the resonator is run as an OPA,the generated bright squeezed light can be tuned continuously more than 50 MHz.