We report on the performance and stability of distributed feedback lasers based on the solution-processed methylammonium lead iodide perovskite (CH3NH3PbI3). The CH3NH3PbI3 layers are processed via solution-casting in ambient atmosphere onto nanoimprinted second order Bragg gratings. This way, we achieve highly polarized surface-emitted lasing at room temperature with a linewidth of less than 0.2 nm and a laser threshold of 120 kW/cm2. The lasing is stable; no change in the laser emission within 15 h of pulsed excitation with a repetition rate of 1 kHz (corresponding to >5 × 107 pulses) is observed, exceeding the stability achieved for solution processed organic semiconductor lasers. Furthermore, adjustment of the grating period allowed the lasing wavelength to be varied over the entire bandwidth of the amplified spontaneous emission (between 781 and 794 nm). The fabrication process of nanoimprinting followed by solution-casting of the gain material demonstrates that stable CH3NH3PbI3 lasers are compatible with scalable production technologies and offers a route towards electrically pumped diode architectures.

Recently it was found that x-ray interference phenomena could be observed in the nonspecularly scattered radiation from thin metallic films. In the present investigation, the interference phenomena which manifested themselves in both the specularly and the nonspecularly scattered x rays from multilayer barium stearate films were examined. Several new features were observed in the scattered radiation, and analysis of the interference patterns yielded values of the total multilayer film thickness and the double-layer spacing. The value obtained for the double-layer spacing is 50.3 A and this value is consistent with values found by other investigators.

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