Holographic interferometry is a well-established field of science and optical engineering. It has a half-century history of successful implementation as the solution to numerous technical tasks and problems. However, fast progress in digital and computer holography has promoted it to a new level of possibilities and has opened brand new fields of its application. In this review paper, we consider some such new techniques and applications.

The comparison of the influence of intra-cavity spectral selectors: static Bragg gratings and dynamic gain gratings, has been presented. It has been shown that their effect on the spectral properties of the laser radiation with a loop resonator is similar. The performed statistical study of the mode composition of the groups of the generation pulses at the Q-factor modulation mode allows us to conclude that the rewriting of the grating by the subsequent group pulse does not prevent radiation at the same frequency. This opens up the possibility of frequency stabilization of the radiation. The presence of an intra-cavity Bragg grating causes an increase in the probability of preserving the radiation frequency in neighboring pulses of the radiation group. It has been shown that there is a narrowing of the pulse generation spectrum in the group, despite the fact that the spectral width of the grating exceeds the spectral width of the generation pulse. The combined operation of static and dynamic intra-cavity gratings makes it possible to create a line of lasers with high pulse energy, radiation quality close to the diffraction limit, high peak power, and a narrow radiation spectrum.

Subject of study. The lasing spectra of a pulsed laser based on a Cr:LiSrAlF₆ active medium are studied. Method. An intracavity transmission volume Bragg grating was used as the lasing mode on two aliquant wavelengths and wavelength tuning. The grating was recorded in a photo-thermo-refractive glass. Main results. For the first time in Russia, simultaneous narrowband lasing was demonstrated at two aliquant wavelengths in the band of 795–895 nm in a Cr:LiSrAlF₆ crystal. The use of a volume transmission Bragg grating for continuous tuning of the central wavelength of the generated laser emission was demonstrated using additional feedback through a mirror with a high reflection coefficient positioned in the first diffraction order. Practical significance. Pulsed lasers with tunable wavelengths are applied in various scientific and practical applications including ecological monitoring of atmosphere conditions. The lasing at two aliquant wavelengths investigated in this study enables the design of high-power pulsed sources of terahertz radiation in the range of 15.5–27.1 THz.

We report the results of a study of laser-induced transparency under the conditions of the optical Stark effect in CdSe nanoplatelets. The induced absorpti

Non-contact, non-destructive testing of surface microgeometry plays a key role in such industries as microelectronics, additive manufacturing, and precision engineering. This paper presents the development and experimental testing of a digital holographic system based on a low-coherence laser diode operating at two close wavelengths, designed to measure height differences in the micrometer range. The method is based on a Michelson interferometer and reconstruction of the complex amplitude of the object wave, which allows phase measurements with subsequent phase conversion into heights. The tests were carried out on micrometer roughness standards with a trapezoidal profile with a groove depth from 24.5 μm to 100 μm and a profile width from 65 μm to 150 μm, as well as on reference strokes with a width from 25 to 200 μm. The obtained data demonstrate the possibility of three-dimensional and two-dimensional visualization of the objects under study with a relative error in height from 5.3% to 11.6% and in width up to 18.6%. It is shown that the system allows reliable measurement of defects of metal surfaces in the range from 25 to 100 μm both vertically and horizontally. Thus, the developed method can be used for high-precision, non-destructive testing in a wide range of technological tasks.

Приведено сопоставление влияния внутрирезонаторных спектральных селекторов: статических решeток Брэгга и динамических решeток коэффициента усиления. Показано, что их влияние на спектральные свойства излучения лазера с петлевым резонатором аналогично. Проведенное статистическое исследование модового состава цугов импульсов генерации в режиме модуляции добротности позволяет сделать заключение о том, что перезапись решeтки последующим импульсом цуга не препятствует излучению на той же частоте. Это открывает возможность частотной стабилизации излучения. Наличие внутрирезонаторной решeтки Брэгга приводит к повышению вероятности сохранения частоты излучения в соседних импульсах цуга излучения. Показано, что наблюдается сужение спектра генерации импульса в цуге несмотря на то, что спектральная ширина решeтки превышает спектральную ширину импульса генерации. Совместная работа статических и динамических внутрирезонаторных решeток позволяет создать линейку лазеров с высокой энергией в импульсе, качеством излучения, близким к дифракционному пределу, высокой пиковой мощностью и узким спектром излучения. Ключевые слова: стационарная решeтка, динамическая решeтка, дифракционная эффективность, самонакачивающийся резонатор, обращение волнового фронта.