Holography materials
Dichromated gelatine emulsion (blue & green)
This material is designed for the recording of reflection Denisyuk-type holograms using CW laser radiation (488nm, 514nm -Argon laser). The material spectral sensitivity curve is shown in figure1. The sensitivity reaches 100mJ/cm2 in the blue spectrum range and 250mJ/cm2 in the green. Due to its grainless structure, this material has very high resolving power and a diffraction efficiency of >75% (figure2), but has the lowest sensitivity from all holography emulsions offered by Geola's distribution network.
The recommended processing technique of the exposed hologram consists of the following operations:
1) Thermal Hardening after exposure (100OC) - Depending on the layer freshness. See figure3.
2) Cooling to Room temperature.
3) Bathing in running filtered water - 3mins.
4) Bathing in 50% Isopropyl Alcohol solution for 2 - 3 mins.
5) Bathing in 75% Isopropyl Alcohol solution for 2 - 3 mins.
6) Bathing in 100% Isopropyl Alcohol solution for 2 - 3 mins.
7) Drying in a desiccator. (100oC) for 60 mins.
8) Emulsion layer preservation using optical anhydrous adhesive and protective glass.
Note that the processing solution temperatures must not exceed 20oC for fresh layers. If holograms appear "milky" in colour then the processing solution temperature should be decreased or the thermal hardening period should be prolonged. The material shelf life is 12 months (average observed period).
Figure 1-3
