Experimental Investigation On Laser Diode Injection Locking System

In the experiment of laser cooling and trapping atoms or BEC, a high power, narrow linewidtn and frequency-stabilized laser is required. The injection locking technique is a effective method to obtain such laser. In order to realize a experiment of laser cooling and trapping atoms ,we have set up a laser diode injection locking system and achieved a laser with single mode, narrow linewidth and 60mW power output.In the thesis, firstly, we report the setting up of our laser diode injection locking system . Secondly, we analyzed the transient optical nonlinear response in four-level atomic medium induced by quantum interference effect.The main contents in my thesis are as follows:1.A grating feedback, tunable diode Laser (Toptica DC 100) is used as a seed source and injected into a high-power slave laser. Under the proper condition, the slave laser can be locked its frequency to the master laser's frequency. We obtained about 60mW laser output. The frequency tunable range near the D2 line of Rb atom is about 4.5 GHz.2.We studied the relationship between the locking bandwidth and the injected signal light intensity and verified that the locking bandwidth is asymmetric .The negative frequency detuning is larger than positive frequency detuning. The locking bandwidth, become larger as the injected signal light intensity is increased. Under the proper condition, the maximum locking bandwidth △ω of the slave laser is approximately 4.7GHz.3.In the experiment, we studied how can the polarization direction of the injected signal influence on the locked state of the slave laser. The frequency of the slave laser is not locked to the master laser when the polarization direction of the injected laser is perpendicular to the polarization direction of the slave laser which is free-running. The slave laser frequency shifts toward low frequency because of thermal effect in the slave laser cavity induced by the injected laser.4.Using semi-classical theory ,we studied a transient behavior in N-rype four-level atomswith coherent system. The theoretical analysis show that the nonlinear absorption for the probe light in the coherent atoms increases rapidly from zero to the steady state through a transient process when signal light is switched on. When the coupling Rabi frequency Ωc satisfies thecondition of Ωc>1/2Г3 ,the transient process is a relaxation oscillation behavior. As the coupling Rabi frequency Ωc decreases , the transient oscillation behavior slows up. When the coupling Rabi frequency Ωc satisfies the condition of Ωc ≤1/2Г3, The transient oscillation behavior dispears.