IV-VI semiconductor multiple quantum well (MQW) structures (PbSe/PbSrSe) were grown on Si(111) and BaF2(111) substrates by molecular beam epitaxy. Structural and optical properties of the MQW structures have been studied using reflection high-energy electron diffraction, high resolution x-ray diffraction (HRXRD), Fourier-transform infrared (FTIR) transmission, and midinfrared photoluminescence (PL). Numerous satellite diffraction peaks and narrow linewidths of the HRXRD rocking curves indicate the high crystalline quality of the structures grown on both Si and BaF2. Longitudinal and oblique valley subband transitions without superposed interference fringes were observed in FTIR differential transmission spectra. Continuous wave midinfrared photoluminescence was also observed from both sets of samples. Comparison of FTIR and PL spectra allows determination of localized epilayer heating in the MQW samples due to optical pumping. For a typical laser pumping power of 9.1 W/cm(2) the heating in a MQW layer on Si(111) was 70 degreesC, while the amount of heating for a MQW layer on lower thermal conductivity BaF2 was 83 degreesC.