Non-linear optical rectification at 10.6 mu m in compositionally asymmetrical GaAs/AlGaAs multi-quantum wells

Summary form only given. The authors present evidence of nonlinear optical rectification in compositionally asymmetrical GaAs/AlGaAs MQWs (multi-quantum wells). The structure consisted of 12 periods of 30-AA GaAs-65-AA Al_0.2Ga_0.8As wells separated by 500-AA Al_0.4Ga_0.6As barriers, epitaxially grown on a 3*10¹⁸ cm^-3 Si-doped GaAs wafer. The GaAs well is 3*10¹⁷ cm^-3 Si doped, while the rest of the wells and barriers are nonintentionally doped. A 3000-AA 10¹⁸-cm^-3 Si-doped GaAs contact layer is grown. The optical rectification is measured at 77 K as a bias appearing at the diode electrodes (with no photocurrent) when it is illuminated by a 10.6- mu m CO₂ laser. An optical rectification coefficient chi ( omicron = omega - omega ) of 5*10^-6 m/V for each well was determined that is an effective electrooptical coefficient of 4.5*10^-9 m/V in the whole structure. This value of chi ( omicron = omega - omega ) is more than three orders of magnitude higher than in a natural nonlinear medium such as GaAs or InP at 10.6 mu m. This structure can thus be used as a highly effective electrooptic medium in infrared waveguides.