Generation Of 420 Nm Coherent Blue Light Based On Four Wave Mixing

The development of laser technology has made a great contribution to the progress of human industrial civilization.The short wavelength laser in blue ultraviolet band has been widely used in high-density optical storage,lithography,underwater communication,marine resources exploration,laser biomedicine and basic physics research because of its wavelength particularity.At present,the mature laser source is mainly in the near-infrared band.The traditional method to obtain the short wavelength coherent light source is to use nonlinear crystal for frequency conversion.Nonlinear crystal will be affected by many defects such as thermal effect,so the research of laser pumping alkali metal vapor to generate short wavelength laser is booming.With the development of narrow linewidth tunable semiconductor laser technology,the interaction between light and atomic medium shows many excellent quantum properties,such as electromagnetically induced transparency,coherent population trapping,orbital angular momentum transfer and so on.Based on these properties,it can be applied to quantum storage,quantum memory,single photon source generation and quantum storage There are many research fields in information processing.In this paper,the experimental study of 420 nm coherent blue light generated by fourwave mixing in rubidium atom is studied.The specific research content is divided into the following three partsFirstly,the development history and current situation of laser pumping alkali metal to obtain short wavelength laser are summarized.At the same time,the four-wave mixing process in alkali metal atoms is analyzed theoretically,and the coupled wave equation describing the four-wave mixing process is obtained.Secondly,a 778 nm high power narrow linewidth diode laser is used to pump rubidium atoms directly,and a 19 ? w coherent blue light at 420 nm is produced by four-wave mixing.During the experiment,the high signal-to-noise ratio two-photon fluorescence spectrum is obtained by using the modulation and demodulation method,which is used as the frequency standard of the pump laser.Finally,the dependences of the output power of coherent blue light on the pump laser power,detuning frequency and rubidium atom density are studied.Thirdly,a four-mirrors ring enhanced cavity for four-wave mixing(FWM)to produce coherent blue light is designed based on the principle of cavity enhancement.At the same time,the process of cavity enhanced four wave mixing is realized experimentally,and a 3.3m W 420 nm coherent blue light output is produced,which is two orders of magnitude higher than that of single laser pumping process.Finally,the velocity transfer spectra of the coherent blue light are studied experimentally.