Generation Of Femtosecond Pulsed Squeezed Light Field With High-order Transverse Mode

Non-classical multimode light field due to its own complexity and quantum correlation plays an important role in the parallel transmission of quantum information,process and storage.Optical frequency combs,which are generated by the mode-locked femtosecond pulse lasers,possess thousands of frequency components.Based on the mode-locked laser and the synchronously pumped optical parametric oscillator,people can obtain nonclassical optical frequency combs.To further,after the introduction of the spatial freedom of the light field,people can achieve new type nonclassical multimode light field having multimode character of space and time.This nonclassical multimode light field can realize wavelength division multiplexing and space division multiplexing communication at the same time,thus enlarging the channel capacity of the quantum networks.In addition,non-classical multimode light field will be hopefully used in three-dimensional space-time quantum measurement of the physical quantity in the mean time.The main work is around the generation of optical frequency comb squeezed light field with high-order transverse mode character.We discuss the relative theoretical and experiment research,the main parts include the following contents:1)The theory of the synchronously pumped optical parametric oscillator theoretical below its threshold.Firstly,we make analysis about the theory of femtosecond pulsed squeezed light field with spatial fundamental mode and femtosecond pulsed squeezed light field with spatial high-order transverse mode,and we show the fomula of squeezed level.Then we compare the difference of two kinds of theory and demonstrate the relationship between optimal conditions and squeezed level.It is a theoretical guidance for preparing optical frequency combs squeezed light field with different spatial high-order transverse modes.2)The experimental generation of optical frequency combs squeezed light field with spatial high-order transverse mode.In the experiment,the fundamental frequency light,which is generated by the mode-locked laser,passes through the second harmonic generator and produces the frequency doubled light which pumps the type-I degenerate synchronously pumped optical parametric oscillator.When the seed beam is the TEM00 mode,we obtain the-1.5dB quadrature amplitude squeezing;when the seed beam is the TEM01 mode,we obtain the-0.7dB quadrature amplitude squeezing.