**1. Introduction**

The method of holography has undergone enormous development since the discovery [1] (1948) up to the present time. The holography also has made great strides in the development of many scientific methods and many technological problems starting with the simplest holograms and ending by the digital holograms [2–4]. Especially it should be noted that already is reached the holographic recording and reconstruction of almost all parameters of the light wave—amplitude, phase, wavelength, and polarization characteristics [5–19]. Anyway the main stage of the holographic process is the creation of the diffractive structure corresponding to distribution of relative phase of the object and reference waves. On this basis, it was possible to say that holography has almost exhausted its potential for further development, but it turned out that there are certain prospects in terms of new nonstandard approaches.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

As it is known, conventional holograms including dynamic represent passive diffractive elements. This means that the reconstruction of the recorded holographic information requires existence of the external source of the light. The light from the external light source is incident on the holographic diffraction structure and diffracting and reconstructs the initial wave front of the light scattered by the object.

However, it is possible to create a structure in which its individual microareas corresponding to the holographic structure can themselves emit mutually coherent radiation. In this case, the reconstruction of the wave front which carries information about the object is possible by laser radiation of this structure but not due to diffraction of light incident from outside. According to the author's opinion, this approach, in addition to the initiation of interesting new research in the field of laser physics and holography, can support to develop optical information technologies and in particular in the technology of holographic 3D displays.

At present, all old and modern methods of obtaining stereoscopic effects are considered for the 3D display tasks. In particular, they are using the earliest approaches of the raster stereoscopic and polarization methods, which require using additional auxiliary equipment in the form of passive glasses or active polarized glasses. From the modern achievements, so-called voxel displays should be noted, when the image is formed by voxel-glowing dots within a certain volume the display. In all of these cases, 3D image represents pseudoimages of the perception which is subjective that is perceived by specific characteristics of human visual system, in particular, by the binocular vision and visual inertia. Holographic images do not require additional raster systems and specific glasses for perception. However, as it was mentioned above, the known holographic structures (holograms) are passive diffraction structures.

In difference of this, the holographic structures (holograms) that reconstruct the wave front of light scattered by the object by own laser radiation might be termed as active holograms.

Laser active holographic structures are fundamentally different because the reconstruction of optical information, in this case, takes place not as a result of diffraction of incident outside light wave, but it is carried out by laser radiation, generated by these structures. Usual holograms represent oneself certain distribution of microscopic optical heterogeneity and implement passive transformation (diffraction) of the light wave (**Figure 1**). The diffraction of the outside light wave on such a structure reconstructs wave front of the light scattered by an object.

**Figure 1.** General structure of the usual hologram.

Now let us assume that all of the microscopic heterogeneity of such a holographic structure represent oneself mutually coherent microlasers. In this case the summary lasing of such a structure will create the wave front analogous to the previous, i.e., will reconstruct of the image of the object but on the wavelength of own radiation. Thus, such a device might be termed as an active holographic structure, and such a method might be termed as an active holography.

As it is known, conventional holograms including dynamic represent passive diffractive elements. This means that the reconstruction of the recorded holographic information requires existence of the external source of the light. The light from the external light source is incident on the holographic diffraction structure and diffracting and reconstructs the initial wave front

However, it is possible to create a structure in which its individual microareas corresponding to the holographic structure can themselves emit mutually coherent radiation. In this case, the reconstruction of the wave front which carries information about the object is possible by laser radiation of this structure but not due to diffraction of light incident from outside. According to the author's opinion, this approach, in addition to the initiation of interesting new research in the field of laser physics and holography, can support to develop optical information tech-

At present, all old and modern methods of obtaining stereoscopic effects are considered for the 3D display tasks. In particular, they are using the earliest approaches of the raster stereoscopic and polarization methods, which require using additional auxiliary equipment in the form of passive glasses or active polarized glasses. From the modern achievements, so-called voxel displays should be noted, when the image is formed by voxel-glowing dots within a certain volume the display. In all of these cases, 3D image represents pseudoimages of the perception which is subjective that is perceived by specific characteristics of human visual system, in particular, by the binocular vision and visual inertia. Holographic images do not require additional raster systems and specific glasses for perception. However, as it was mentioned above, the known holographic structures (holograms) are passive diffraction structures.

In difference of this, the holographic structures (holograms) that reconstruct the wave front of light scattered by the object by own laser radiation might be termed as active holograms.

Laser active holographic structures are fundamentally different because the reconstruction of optical information, in this case, takes place not as a result of diffraction of incident outside light wave, but it is carried out by laser radiation, generated by these structures. Usual holograms represent oneself certain distribution of microscopic optical heterogeneity and implement passive transformation (diffraction) of the light wave (**Figure 1**). The diffraction of the outside light

wave on such a structure reconstructs wave front of the light scattered by an object.

nologies and in particular in the technology of holographic 3D displays.

of the light scattered by the object.

464 Holographic Materials and Optical Systems

**Figure 1.** General structure of the usual hologram.

The first results in this direction have been obtained in the layer of cholesteric liquid crystal (CLC) doped by the dye 4-Dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) and in the layer of polyvinyl alcohol (PVA) doped by dye Rhodamine 6G [20–28].
