The process of obtaining a modified structure for quantum cascade lasers is studied; this process includes growth using molecular-beam epitaxy, plasma etching, photolithography with the use of liquid etching, and the formation of special contacts for decreasing losses in the waveguide. The use of a special type of structure makes it possible, even without postgrowth overgrowth with a high-resistivity material, to attain parameters satisfying requirements to heterostructures in high-quality quantum cascade lasers at maximal simplification of the entire preparation process.
The studies of the emission linewidth for single-mode near-IR vertical-cavity surface-emitting lasers with an active region based on InGaAs/AlGaAs quantum wells and different optical microcavity design. For low mirror loss, lasers with a 1λ cavity and carrier injection through distributed Bragg reflectors demonstrate a linewidth of 70 MHz and its growth to 110 MHz with increasing mirror loss (corresponding differential of efficiency ∼0.65 W/A). The design of the optical cavity with carrier injection through intracavity contacts and low-Q composition Bragg lattices reduces the linewidth to 40 MHz in spite of high mirror loss (corresponding differential efficiency of ∼0.6 W/A).
С помощью Mo/Be и Si/Mo интерференционных зеркал выполнены измерения интенсивности излучения лазерной плазмы с Xe газоструйной мишенью в полосе длин волн 11−14 nm со спектральным разрешением 3−6 ¦. Полученные результаты сравниваются со спектром, измеренным ранее с помощью спектрографа. Найдено, что в исследованном режиме возбуждения плазмы отношение интенсивностей на длинах волн 11.2 и 13.5 nm составило примерно 10 раз.
A method for generation of droplet quasi-Bessel beams using a conical lens with a rounded tip is demonstrated. The study of the longitudinal distribution of the intensity of the obtained quasi-Bessel beam showed that, due to the interference of two wavefronts that occurred as the generating beam passed through the rounded axicon, periodical intensity pulsations that looked like “drops” of light occurred in the resulting beam. These light beams can be used for micromanipulation of biological objects and in super-resolution microscopy. The application of an axicon with a rounded tip for generation of a droplet beam allows considerable simplification and miniaturization of the experimental setup, which paves the way for multiple practical applications.
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