Research On Cascaded Four-wave Mixing And Mode-locked Laser Based On SOA

Optical frequency comb and mode-locked laser source based on semiconductor technology have advantages such as good stability,large gain,easy integration and large-scale application,compared with traditional optical fiber technology.The mode-locked laser source with high repetition rate and narrow pulse width has much applications in all optical information processing,optical fiber communication system and optical sampling system.The cavity-free mode-locked lasers based on semiconductor technology are more stable than traditional mode-locked laser with optical fiber ring,which pulse quality is easily affected by environment.And the pulse repetition of cavity-free mode-locked lasers is not controlled by the frequency of ring cavity.In this paper,the four-wave mixing effect(FWM)and cascaded four-wave mixing effect of semiconductor optical amplifier(SOA)and the cavity-free mode-locked laser source based on semiconductor optical amplifier are studied.The theory of semiconductor optical amplifier and four-wave mixing effect are analyzed.The influence factors of the cascaded four-wave mixing effect are studied.The cascaded four-wave mixing experiment scheme based on cascaded semiconductor optical amplifiers is proposed.The good four-wave mixing optical frequency comb is acquired.The comparison experiment of cascaded four wave mixing between semiconductor optical amplifier and high nonlinear fiber is made.And the difference between the cascaded four-wave mixing effects of the two methods is obtained.Based on the cascaded four wave mixing effect of semiconductor optical amplifier,an experimental method of cavity-free semiconductor mode-locked laser is proposed.And a high quality picosecond pulsed light source with widely tunable repetition frequency is obtained.The main research work of this paper is as follows:1.The theory of cascaded four wave mixing effect in semiconductor optical amplifier is studied.And the influence factors of cascaded four wave mixing effect are experimentally analyzed.The effects of the wavelength interval of two lasers,which is also called the frequency detuning,the polarization state of two lasers and the pumping current of SOA,on the cascade four-wave mixing effect are investigated in detail.The cascaded four-wave mixing experiment scheme based on cascaded semiconductor optical amplifier is proposed.The pumping currents of two SOA are adjusted in order to obtain better four-wave mixing optical frequency comb.2.The cascaded four-wave mixing effects in semiconductor optical amplifiers and high nonlinear optical fibers are compared experimentally.The fundamental difference between the cascaded four-wave mixing effects of the two methods is analyzed.And the experimental scheme of cavity-free semiconductor mode-locked laser is proposed.By filtering the nonlinear phase regime of the optical frequency comb,mode-locked pulse with high quality is obtained.The pulse repetition rates are 9~10GHz and can be tuned continuously.The best side-mode suppression ratio we measured is 23 dB in ESA when the repetition rate of generated pulses is 8.9GHz.