::Technological process and methods of hologram manufacturing of various types

Scheme of hologram recording PFG photoplates Laser Spatial filter (pinhole) Beam polarization Object Exposure Hologram recording Preparation of chemical solutions Hologram development Hologram drying
Introduction History of holography Physical laws Holography and artist Holography and photo Types of holograms Holography applications Holographic scenes Glossary Main
  ::Main

::Laser

A special light source is used for recording holograms. It is a laser. There are two main features, which distinguish the laser light, and radiation of other light sources. These are monochromatic radiation and coherency. Monochromatic radiation is a radiation, which spectrum is very narrow and it is visually perceived as a pure color - red, green, etc. Coherency is a more complicated concept. It is defined by constancy of the wave-front phase in the space as well as in the time. All the lasers are monochromatic (to different extent), but coherency is inherent in only such lasers, which are used for holography or special measurements. We aren't going to consider details of complicated theory of coherency, we can say: the greater coherency of the laser radiation, the greater depth of a scene is possible to be recorded on a hologram. There are various types of lasers. The following lasers are mostly involved in holography:

Helium-Neon (He-Ne) laser
The main instrument of holographers. It is very reliable, simple, economical and has good holographic characteristics. LG-38, LGN-215, LGN-220 models are widely used in Russia (see photo).
- Radiating wavelength is 633nm (red color).
- Radiating power: up to 60 mW.
- Coherency length: 15-20 cm.

Argon laser
The powerful ionic laser radiating in blue&green region of spectrum. It has great electric power (5 - 10kW) and demands water-cooling. This laser is irreplaceable for recording holograms of big sizes.
- Main radiating wavelengths
514 nm (yellow and green color): 2-5 W,
488 nm (green color): 1-3 W
- Lines with small power
455 nm, 458 nm, 466 nm, 473 nm, 476 nm, 487 nm, 502 nm.
- Coherency length
Without Fabry-Perot interferometer: 5 cm
With Fabry-Perot interferometer: 2-3 m

Krypton laser
The powerful ionic laser radiating in red region of spectrum. It has great electric power (5- 10kW) and demands water-cooling. This laser is irreplaceable for recording holograms of big sizes.
- Radiating wavelength: 647 nm (red color).
- Radiating power: 1-3W
- Coherency length
Without Fabry-Perot interferometer: 5 cm
With Fabry-Perot interferometer: 2-3 m.

Cadmium laser
Radiation in blue region of spectrum. It is suitable for recording dichromate gelatin holograms and exposing photoresist to record relief rainbow holograms.
- Radiating wavelength: 440 nm (violet and blue color).
- Radiating power: up to 50mW
- Coherency length: 15 - 20 cm.