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The effect of superadditivity on ascorbic acid in the reversal bleached transmission hologram
ARTICLE IN PRESS
Optics & Laser Technology 37 (2005) 449–453 www.elsevier.com/locate/optlastec
The effect of superadditivity on ascorbic acid in the reversal bleached transmission hologram Chun Woo Lim, Dae Wook Choi, Sang Ho Sohn Department of Physics, Kyungpook National University, 1370 Sankyuck-Dong, Puk-Gu Taegu 702-701, South Korea Received 18 July 2003; accepted 28 July 2004 Available online 15 September 2004
Abstract This paper shows that the diffraction efficiency is influenced by superadditivity for the combination of the different developing agent and concentrations in the reversal bleach applied to the Slavich PFG-01 plate to be used for recording transmission holograms. The four developers based on ascorbic acid in combination with metol, phenidone, hydroquinone respectively, were studied. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC in the reversal bleach. r 2004 Elsevier Ltd. All rights reserved. Keywords: Holography; Holography recording materials; Superadditivity
1. Introduction Generally, Silver halide photographic emulsions are known as the most convenient for phase holographic recording due to the high sensitivity and ease of handling. They are largely used for recording holograms, mainly in display holography, numerous scientific applications, and in the fabrication of holographic optical elements [1,2]. Holograms recorded on silver halide emulsions are commonly bleached to increase the diffraction efficiency. Bleaching is one of the most popular techniques, used to obtain the phase holograms with high diffraction efficiencies from silver halide emulsions. The reversal bleaching technique is, the developed silver image is converted into a soluble silver complex which removes the emulsion during bleaching, leaving the original, unexposed silver halide grains in the emulsion. The reversal bleaching can minimize scatterCorresponding author. Tel.: +82-53-950-5892; fax: +82-53-9506893. E-mail addresses: [email protected] (C.W. Lim), [email protected] (S.H. Sohn).
0030-3992/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2004.07.009
ing due to the halide of unexposed zones but it has little influence on the type of bleach solutions. In particularly, conventional and fixation-free rehalogenating bleaching techniques have been studied during the past decades. However, we have a few studies of the reversal bleaching techniques, based mainly on the Agfa and Kodak plates. Development is a processing technique by which the latent image recorded during the exposure of the material is converted into a silver image. The developing agent reduces the silver ions in the exposed silver halide to metallic silver to make the latent image on the plate visible is most important component. The most popular developing agent used as developers for holography are metol, hydroquinone, l-ascorbic acid, and phenidone. Each agents has own specific characteristics. It is well known that the combination of different developing agents can produce an outstanding increase in the developing rate. This effect, called superadditivity, is important in photographic processing [3]. That means: the reducing power of the mixture is greater than the sum of the reducing powers of the components. Most of the earlier studies of superadditivity were concerned with Metol-hydroquinone combinations in the conventional bleach. Levenson proposed a
ARTICLE IN PRESS 450
C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
regeneration reaction to account for superadditivity development. The regeneration mechanism could account for a superadditivity effect that if an oxidation product of the first developing agent inhibits development, regeneration may effectively remove this inhibiting product from the grain by converting it to the active developer [4]. Van Veelen showed that superadditivity can occur for the physical as well as the chemical development [5]. The superadditivity does not depend uniquely on the presence of a silver halide surface at the reaction site. The effects of superadditivity in developers based on ascorbic acid with different organic redox systems is introduced by Madrigal, Blaya, Carretero, Ulibarrena and Fimia [6]. They studied the real time variation of the optical density at the development process by using Agfa 8E56HD without the bleach process. When two developing agents are used in the same solution and all other variables are fixed, the developing rate in the mixture can depend on the concentration of the agents. This paper presents the results of experiments on the reversal bleached transmission hologram records Slavich PFG-01 plates which show that the diffraction efficiencies are affected by both the combination of the different developing agent and their concentrations.
2. Experiments Holographic transmission diffraction gratings were recorded on the Slavich PFG-01 plates by using two collimated beams from He–Ne laser, l ¼ 632:8 nm: The beam ratio was 1:1 and impinged on the emulsion forming an angle of 45 : The spatial frequency of the gratings was calculated as 1200 lines/mm. The exposed plates were processed according to the processing schedule shown in Table 1. Because the gelatin of the PFG-01 is softer than other emulsions, a high temperature bleach bath could remove the gelatin from the layer, resulting in the low diffraction efficiency. All process were carried out at a constant temperature of 20 1C. Table 1 Processing Schedule for reversal bleach 1. 2. 3. 4. 5. 6. 7.
Develop Rinse in distilled water Bleach for 1 min after the plate has cleared Rinse in distilled water Dehydrate in 50% isopropanol Dehydrate in 100% isopropanol Dry at room temperature
All solutions are at 201C
4 min 5 min 5 min 4 min 5 min 24 h
Table 2 Developer composition (g/L) Formula
AAC
MAA
PAAC
HAAC
L-ascorbic acid Metol Phenidone Hydroquinone Sodium carbonate
20
20 1:0
20
20
0:2 60
60
60 (120)
6 60
The quantity changes (Variable quantity).
Table 3 Reversal bleach composition Potassium dichromate Sulfuric acid Distilled water
0.8 g 1.0 mL 1.0 L
The formulas of all the developers used in the experiments are given in Table 2. Experiments were carried out with four types of developers based on lascorbic acid. One was AAC with one developing agent, ascorbic acid. The other type of developers: MAA, PAAC, HAAC was the mixtures of different developing agents, metol (methylaminophenol sulfate), phenidone, and hydroquinone with l-ascorbic acid. Amounts of l-ascorbic acid, metol, phenidone, and hydroquinone change in order to study the superadditivity effect of the developing agents. L-ascorbic acid is slowly oxidized in an acidic or neutral environment, but in alkaline solutions it reacts rapidly with oxygen or silver halide. Since the developing agent acts slowly, practical developers must also contain the activator that accelerates the development by keeping the developer to be alkaline. Most reducing agents perform efficiently only if they are in an alkaline solution [7]. This means we must add an alkali to the developing solution to activate the reducer. So the alkaline compound that acts like an accelerator in a developer are sodium carbonate. The alkali, in addition to promoting ionization of the reducing agent, also softens the gelatin of the emulsion. The stronger the alkali means a greater this softening effect. Table 3 shows the compositions of the reversal bleach, which are used in this experiment. The diffraction efficiency was defined as the ratio between the beam intensity in the first diffraction order and the incident beam intensity at Bragg angle. The efficiency of the zero order or of transmission was similarly calculated as the ratio of the directly transmitted beam intensity to the incident power and was corrected by the same factor.
ARTICLE IN PRESS C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
3. Results and discussion
451
100 1.0g 2.0g 4.0g 6.0g 10.0g
Diffraction efficiency (%)
90 80 70 60 50 40 30 20 10 0 102
103 2
Exposure energy (µJ/cm ) Fig. 2. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with MAA containing different amounts of metol (l-ascorbic acid 20 g, sodium carbonate 60 g).
100 90 Diffraction efficiency (%)
Fig. 1 presents a diffraction efficiency as a function of exposure energy curves for the reversal bleach processed with AAC containing different amounts of l-ascorbic acid. The maximum diffraction efficiency of 89% was obtained with an AAC developer containing 20 g of lascorbic acid. We also tried to increase the amounts of lascorbic acid to 100 g, but the resulting maximum diffraction efficiency has tendency to decrease, as seen in Fig. 1. The results indicate that the action development of AAC can reach the limit for the amount of l-ascorbic acid. The increase of l-ascorbic acid brings overreduction, and as a result, an increase in the diffusion transfer effect. The diffusion transfer effect is that silver halide of the exposed zone and silver halide of the unexposed zone transfer from the unexposed zones to the exposed zone during developing is converted into metallic silver. The developing agent displays a tendency to reduce some of the unexposed silver halides as well as the exposed one. This behavior leads to be a good result in the conventional bleach. Contrary to this, in case of the reversal bleach, there is a decrease in the diffraction efficiency because of the reduction of silver halides remaining in the unexposed zone. Fig. 2 presents diffraction efficiency and exposure energy curves for the reversal bleach processed with MAA containing different amounts of metol. The maximum diffraction efficiency of 80.3% was obtained with 1.0 g/L of metol. The increase in the concentration of metol resulted in a decrease of diffraction efficiency. It is thought that a decrease in diffraction efficiency is due to a low contrast of grating with an increase in the concentration of metol. The metol is a powerful developing agent that works rapidly and it will go to work even on those silver halides that received a
80 70 60 50 40 30
A B C D
20 10 0 102
103 Exposure energy
Fig. 3. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with PAAC containing different amounts of phenidone (l-ascorbic acid 20 g, A: Phenidone 0.2 g, sodium carbonate 120 g, B: Phenidone 0.4 g, sodium carbonate 120 g, C: Phenidone 0.8 g, sodium carbonate 120 g, D: Phenidone 0.2 g, sodium carbonate 60 g).
100 90
Diffraction efficiency (%)
(µJ/cm2)
80 70 60 50 40
4g 10g 20g 40g 60g 100g
30 20 10 0 102
103
Exposure energy
(µJ/cm2)
Fig. 1. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with AAC containing different amounts of l-ascorbic acid (sodium carbonate 60 g).
minimum of light. So the metol-ascorbic acid developing agents that increase the rate of development. It appears that reduces some of the unexposed silver halides as well as the exposed ones. The silver halides remaining in unexposed area is decreased, since some of the unexposed silver halides as well as the exposed ones are converted into metallic silver. This effect resulted in a decrease of the refractive-index modulation and the diffraction efficiency. Fig. 3 shows variation diffraction efficiency and exposure energy curves for the reversal bleach processed with PAAC containing different amounts of phenidone.
ARTICLE IN PRESS C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
452
developing agents with a higher redox potential such as metol, developers containing l-ascorbic acid do not require sodium sulfite as an antioxidant [8]. Table 4 shows the maximum diffraction efficiency and the exposure energy obtained in the four different developers. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC. And the maximum diffraction efficiency of mixture of two developing agents could be obtained at a lower exposure energy. The superadditivity effect of MQ developer had a good effect in the conventional bleach [9]. However, in the reversal bleach, a higher diffraction efficiency could not be obtained when combined with the two agents. In the case of MQ developer, the reducing rate of the mixture of two developing agents is greater than the sum of the reducing rate of the components. These effects bring out the developing of silver halides in unexposed zone, and result in a decrease of the refractive-index modulation, since the silver halides remained at unexposed zones reduce. The diffraction efficiency is related to the activity of the developing agent, so that pH of developer solution may be an important parameter. The pH of developer fixed with concentration of develop accelerate, sodium carbonate. However, in future, we think that it is needed to study influence of superadditivity on pH of developer due to rate of development depend on pH.
With the addition of phenidone, the maximum efficiency was 57.3% when PAAC developer contained phenidone 0.2 g/L and sodium carbonate 60 g/L. And the maximum efficiency was 66.3% when PAAC developer contained phenidone 0.2 g/L and sodium carbonate 120 g/L. It is implied that phenidone-ascorbic acid developing agents works actively at a higher pH. Adding more phenidone to PAAC developer leads to lower values of diffraction efficiency. Phenidone is a developing agent similar to metol, and the increase in diffraction efficiency obtained in the reduction concentration of phenidoe as metol in MAA developer. Fig. 4 shows diffraction efficiency and exposed energy curves processed with HAAC containing different amount of hydroquinone to AAC. Hydroquinone used alone is slow in its action and requires strong alkali. It is almost always applied together with metol or phenidone for holographic work in the conventional bleach. The maximum diffraction efficiency was obtained 76.2% when contained hydroquinone 10 g/L. It, like hydroquinone, exhibits superadditivity with other developing agents but that its oxidation products do interfere with development. Since it also inhibits the oxidation of 100 6g 8g 10g 12g
Diffraction efficiency (%)
90 80 70 60 50
4. Conclusion
40
These experiments show that in diffraction efficiency aspect, the effect superadditivity of developer composition on reversal bleach applied to the Slavich PFG-01 plate to be used for recording transmission holograms. The four developers based on ascorbic acid in combination with metol, phenidone, hydroquinone respectively, were studied. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC in the reversal bleach. With the conventional bleach, the
30 20 10 0 102
103 Exposure energy
(µJ/cm2)
Fig. 4. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with HAAC containing different amounts of hydroquinone (l-ascorbic acid 20 g, sodium carbonate 60 g). Table 4 Results for various developers Developer
Developing agent A (g)
Diffraction efficiency (%)
Exposure energy (mJ=cm2 )
AAC MAA PAAC HAAC
Metol (1.0) Phenidone (0.2) Hydroquinone (10)
89.0 80.3 57.3 76.2
463 355 232 385
& Developer composition: Ascorbic acid 20 g+Sodium carbonate 60 g+A
ARTICLE IN PRESS C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
superadditivity effect of MQ developer achieved a good result. The reversal bleach, however, could not obtain a good result. This fact suggests that over-reducing and diffusion transfer effect is increased in develop process. The reduction of silver halides in the unexposed zone by diffusion transfer effect resulted in lower refractiveindex modulation and a drop in the diffraction efficiency. It is demonstrated that the diffraction efficiency is affected by the type and the concentration of the mixture of the developing agents. The results reveal that the superadditivity effect developing agent on based ascorbic acid play an important role in obtaining high diffraction efficiency of reversal bleach hologram. References [1] Domingo M, Arias I, Garcia A. Achromatic Fourier processor with holographic optical lenses. Appl Opt 2001;40:2267–74.
453
[2] Kim JM, Choi BS, Kim SI, Kim JM, Bjelkhagen HJ, Phillips NJ. Holographic optical elements recorded in silver halide sensitized gelatin emulsions. Part 1: transmission holographic optical elements. Appl Opt 2001;40:622–32. [3] Walls HJ, Attridge GG. Basic photo science. London: Focal Press; 1977. p. 195–6. [4] James TH. The theory of the photographic process. New York: Macmillan; 1977. p. 433. [5] Van Veelen GF. Photographic science. New York: Focal Press; 1963. p. 179. [6] Madrigal RF, Blaya S, Carretero L, Ulibarrena M, Fimia A. Real time study of the response of ascorbic as developer agent in holographic emulsions: superadditivity effects. Opt Commun 2001;199:317–24. [7] Bjelkhagen HI. Silver-halide recording materials for holography and their processing. Berlin: Springer; 1995. [8] Hariharan P, Chidley CM. Photographic phase holograms: the influence of developer composition on scattering and diffraction efficiency. Appl Opt 1987;26:1230–4. [9] Hariharan P, Chidley CM. Rehalogenating bleaches for photographic phase holograms: the influence of halide type and concentration on diffraction efficiency and scattering. Appl Opt 1987;26:3895–8.
Optics & Laser Technology 37 (2005) 449–453 www.elsevier.com/locate/optlastec
The effect of superadditivity on ascorbic acid in the reversal bleached transmission hologram Chun Woo Lim, Dae Wook Choi, Sang Ho Sohn Department of Physics, Kyungpook National University, 1370 Sankyuck-Dong, Puk-Gu Taegu 702-701, South Korea Received 18 July 2003; accepted 28 July 2004 Available online 15 September 2004
Abstract This paper shows that the diffraction efficiency is influenced by superadditivity for the combination of the different developing agent and concentrations in the reversal bleach applied to the Slavich PFG-01 plate to be used for recording transmission holograms. The four developers based on ascorbic acid in combination with metol, phenidone, hydroquinone respectively, were studied. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC in the reversal bleach. r 2004 Elsevier Ltd. All rights reserved. Keywords: Holography; Holography recording materials; Superadditivity
1. Introduction Generally, Silver halide photographic emulsions are known as the most convenient for phase holographic recording due to the high sensitivity and ease of handling. They are largely used for recording holograms, mainly in display holography, numerous scientific applications, and in the fabrication of holographic optical elements [1,2]. Holograms recorded on silver halide emulsions are commonly bleached to increase the diffraction efficiency. Bleaching is one of the most popular techniques, used to obtain the phase holograms with high diffraction efficiencies from silver halide emulsions. The reversal bleaching technique is, the developed silver image is converted into a soluble silver complex which removes the emulsion during bleaching, leaving the original, unexposed silver halide grains in the emulsion. The reversal bleaching can minimize scatterCorresponding author. Tel.: +82-53-950-5892; fax: +82-53-9506893. E-mail addresses: [email protected] (C.W. Lim), [email protected] (S.H. Sohn).
0030-3992/$ - see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.optlastec.2004.07.009
ing due to the halide of unexposed zones but it has little influence on the type of bleach solutions. In particularly, conventional and fixation-free rehalogenating bleaching techniques have been studied during the past decades. However, we have a few studies of the reversal bleaching techniques, based mainly on the Agfa and Kodak plates. Development is a processing technique by which the latent image recorded during the exposure of the material is converted into a silver image. The developing agent reduces the silver ions in the exposed silver halide to metallic silver to make the latent image on the plate visible is most important component. The most popular developing agent used as developers for holography are metol, hydroquinone, l-ascorbic acid, and phenidone. Each agents has own specific characteristics. It is well known that the combination of different developing agents can produce an outstanding increase in the developing rate. This effect, called superadditivity, is important in photographic processing [3]. That means: the reducing power of the mixture is greater than the sum of the reducing powers of the components. Most of the earlier studies of superadditivity were concerned with Metol-hydroquinone combinations in the conventional bleach. Levenson proposed a
ARTICLE IN PRESS 450
C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
regeneration reaction to account for superadditivity development. The regeneration mechanism could account for a superadditivity effect that if an oxidation product of the first developing agent inhibits development, regeneration may effectively remove this inhibiting product from the grain by converting it to the active developer [4]. Van Veelen showed that superadditivity can occur for the physical as well as the chemical development [5]. The superadditivity does not depend uniquely on the presence of a silver halide surface at the reaction site. The effects of superadditivity in developers based on ascorbic acid with different organic redox systems is introduced by Madrigal, Blaya, Carretero, Ulibarrena and Fimia [6]. They studied the real time variation of the optical density at the development process by using Agfa 8E56HD without the bleach process. When two developing agents are used in the same solution and all other variables are fixed, the developing rate in the mixture can depend on the concentration of the agents. This paper presents the results of experiments on the reversal bleached transmission hologram records Slavich PFG-01 plates which show that the diffraction efficiencies are affected by both the combination of the different developing agent and their concentrations.
2. Experiments Holographic transmission diffraction gratings were recorded on the Slavich PFG-01 plates by using two collimated beams from He–Ne laser, l ¼ 632:8 nm: The beam ratio was 1:1 and impinged on the emulsion forming an angle of 45 : The spatial frequency of the gratings was calculated as 1200 lines/mm. The exposed plates were processed according to the processing schedule shown in Table 1. Because the gelatin of the PFG-01 is softer than other emulsions, a high temperature bleach bath could remove the gelatin from the layer, resulting in the low diffraction efficiency. All process were carried out at a constant temperature of 20 1C. Table 1 Processing Schedule for reversal bleach 1. 2. 3. 4. 5. 6. 7.
Develop Rinse in distilled water Bleach for 1 min after the plate has cleared Rinse in distilled water Dehydrate in 50% isopropanol Dehydrate in 100% isopropanol Dry at room temperature
All solutions are at 201C
4 min 5 min 5 min 4 min 5 min 24 h
Table 2 Developer composition (g/L) Formula
AAC
MAA
PAAC
HAAC
L-ascorbic acid Metol Phenidone Hydroquinone Sodium carbonate
20
20 1:0
20
20
0:2 60
60
60 (120)
6 60
The quantity changes (Variable quantity).
Table 3 Reversal bleach composition Potassium dichromate Sulfuric acid Distilled water
0.8 g 1.0 mL 1.0 L
The formulas of all the developers used in the experiments are given in Table 2. Experiments were carried out with four types of developers based on lascorbic acid. One was AAC with one developing agent, ascorbic acid. The other type of developers: MAA, PAAC, HAAC was the mixtures of different developing agents, metol (methylaminophenol sulfate), phenidone, and hydroquinone with l-ascorbic acid. Amounts of l-ascorbic acid, metol, phenidone, and hydroquinone change in order to study the superadditivity effect of the developing agents. L-ascorbic acid is slowly oxidized in an acidic or neutral environment, but in alkaline solutions it reacts rapidly with oxygen or silver halide. Since the developing agent acts slowly, practical developers must also contain the activator that accelerates the development by keeping the developer to be alkaline. Most reducing agents perform efficiently only if they are in an alkaline solution [7]. This means we must add an alkali to the developing solution to activate the reducer. So the alkaline compound that acts like an accelerator in a developer are sodium carbonate. The alkali, in addition to promoting ionization of the reducing agent, also softens the gelatin of the emulsion. The stronger the alkali means a greater this softening effect. Table 3 shows the compositions of the reversal bleach, which are used in this experiment. The diffraction efficiency was defined as the ratio between the beam intensity in the first diffraction order and the incident beam intensity at Bragg angle. The efficiency of the zero order or of transmission was similarly calculated as the ratio of the directly transmitted beam intensity to the incident power and was corrected by the same factor.
ARTICLE IN PRESS C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
3. Results and discussion
451
100 1.0g 2.0g 4.0g 6.0g 10.0g
Diffraction efficiency (%)
90 80 70 60 50 40 30 20 10 0 102
103 2
Exposure energy (µJ/cm ) Fig. 2. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with MAA containing different amounts of metol (l-ascorbic acid 20 g, sodium carbonate 60 g).
100 90 Diffraction efficiency (%)
Fig. 1 presents a diffraction efficiency as a function of exposure energy curves for the reversal bleach processed with AAC containing different amounts of l-ascorbic acid. The maximum diffraction efficiency of 89% was obtained with an AAC developer containing 20 g of lascorbic acid. We also tried to increase the amounts of lascorbic acid to 100 g, but the resulting maximum diffraction efficiency has tendency to decrease, as seen in Fig. 1. The results indicate that the action development of AAC can reach the limit for the amount of l-ascorbic acid. The increase of l-ascorbic acid brings overreduction, and as a result, an increase in the diffusion transfer effect. The diffusion transfer effect is that silver halide of the exposed zone and silver halide of the unexposed zone transfer from the unexposed zones to the exposed zone during developing is converted into metallic silver. The developing agent displays a tendency to reduce some of the unexposed silver halides as well as the exposed one. This behavior leads to be a good result in the conventional bleach. Contrary to this, in case of the reversal bleach, there is a decrease in the diffraction efficiency because of the reduction of silver halides remaining in the unexposed zone. Fig. 2 presents diffraction efficiency and exposure energy curves for the reversal bleach processed with MAA containing different amounts of metol. The maximum diffraction efficiency of 80.3% was obtained with 1.0 g/L of metol. The increase in the concentration of metol resulted in a decrease of diffraction efficiency. It is thought that a decrease in diffraction efficiency is due to a low contrast of grating with an increase in the concentration of metol. The metol is a powerful developing agent that works rapidly and it will go to work even on those silver halides that received a
80 70 60 50 40 30
A B C D
20 10 0 102
103 Exposure energy
Fig. 3. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with PAAC containing different amounts of phenidone (l-ascorbic acid 20 g, A: Phenidone 0.2 g, sodium carbonate 120 g, B: Phenidone 0.4 g, sodium carbonate 120 g, C: Phenidone 0.8 g, sodium carbonate 120 g, D: Phenidone 0.2 g, sodium carbonate 60 g).
100 90
Diffraction efficiency (%)
(µJ/cm2)
80 70 60 50 40
4g 10g 20g 40g 60g 100g
30 20 10 0 102
103
Exposure energy
(µJ/cm2)
Fig. 1. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with AAC containing different amounts of l-ascorbic acid (sodium carbonate 60 g).
minimum of light. So the metol-ascorbic acid developing agents that increase the rate of development. It appears that reduces some of the unexposed silver halides as well as the exposed ones. The silver halides remaining in unexposed area is decreased, since some of the unexposed silver halides as well as the exposed ones are converted into metallic silver. This effect resulted in a decrease of the refractive-index modulation and the diffraction efficiency. Fig. 3 shows variation diffraction efficiency and exposure energy curves for the reversal bleach processed with PAAC containing different amounts of phenidone.
ARTICLE IN PRESS C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
452
developing agents with a higher redox potential such as metol, developers containing l-ascorbic acid do not require sodium sulfite as an antioxidant [8]. Table 4 shows the maximum diffraction efficiency and the exposure energy obtained in the four different developers. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC. And the maximum diffraction efficiency of mixture of two developing agents could be obtained at a lower exposure energy. The superadditivity effect of MQ developer had a good effect in the conventional bleach [9]. However, in the reversal bleach, a higher diffraction efficiency could not be obtained when combined with the two agents. In the case of MQ developer, the reducing rate of the mixture of two developing agents is greater than the sum of the reducing rate of the components. These effects bring out the developing of silver halides in unexposed zone, and result in a decrease of the refractive-index modulation, since the silver halides remained at unexposed zones reduce. The diffraction efficiency is related to the activity of the developing agent, so that pH of developer solution may be an important parameter. The pH of developer fixed with concentration of develop accelerate, sodium carbonate. However, in future, we think that it is needed to study influence of superadditivity on pH of developer due to rate of development depend on pH.
With the addition of phenidone, the maximum efficiency was 57.3% when PAAC developer contained phenidone 0.2 g/L and sodium carbonate 60 g/L. And the maximum efficiency was 66.3% when PAAC developer contained phenidone 0.2 g/L and sodium carbonate 120 g/L. It is implied that phenidone-ascorbic acid developing agents works actively at a higher pH. Adding more phenidone to PAAC developer leads to lower values of diffraction efficiency. Phenidone is a developing agent similar to metol, and the increase in diffraction efficiency obtained in the reduction concentration of phenidoe as metol in MAA developer. Fig. 4 shows diffraction efficiency and exposed energy curves processed with HAAC containing different amount of hydroquinone to AAC. Hydroquinone used alone is slow in its action and requires strong alkali. It is almost always applied together with metol or phenidone for holographic work in the conventional bleach. The maximum diffraction efficiency was obtained 76.2% when contained hydroquinone 10 g/L. It, like hydroquinone, exhibits superadditivity with other developing agents but that its oxidation products do interfere with development. Since it also inhibits the oxidation of 100 6g 8g 10g 12g
Diffraction efficiency (%)
90 80 70 60 50
4. Conclusion
40
These experiments show that in diffraction efficiency aspect, the effect superadditivity of developer composition on reversal bleach applied to the Slavich PFG-01 plate to be used for recording transmission holograms. The four developers based on ascorbic acid in combination with metol, phenidone, hydroquinone respectively, were studied. In diffraction efficiency aspect, the superadditivity effect of mixture of two developing agents is lower than one developing agent developer, AAC in the reversal bleach. With the conventional bleach, the
30 20 10 0 102
103 Exposure energy
(µJ/cm2)
Fig. 4. Diffraction efficiency and exposure energy curves for the reversal bleach on PFG-01 plates processed with HAAC containing different amounts of hydroquinone (l-ascorbic acid 20 g, sodium carbonate 60 g). Table 4 Results for various developers Developer
Developing agent A (g)
Diffraction efficiency (%)
Exposure energy (mJ=cm2 )
AAC MAA PAAC HAAC
Metol (1.0) Phenidone (0.2) Hydroquinone (10)
89.0 80.3 57.3 76.2
463 355 232 385
& Developer composition: Ascorbic acid 20 g+Sodium carbonate 60 g+A
ARTICLE IN PRESS C.W. Lim et al. / Optics & Laser Technology 37 (2005) 449–453
superadditivity effect of MQ developer achieved a good result. The reversal bleach, however, could not obtain a good result. This fact suggests that over-reducing and diffusion transfer effect is increased in develop process. The reduction of silver halides in the unexposed zone by diffusion transfer effect resulted in lower refractiveindex modulation and a drop in the diffraction efficiency. It is demonstrated that the diffraction efficiency is affected by the type and the concentration of the mixture of the developing agents. The results reveal that the superadditivity effect developing agent on based ascorbic acid play an important role in obtaining high diffraction efficiency of reversal bleach hologram. References [1] Domingo M, Arias I, Garcia A. Achromatic Fourier processor with holographic optical lenses. Appl Opt 2001;40:2267–74.
453
[2] Kim JM, Choi BS, Kim SI, Kim JM, Bjelkhagen HJ, Phillips NJ. Holographic optical elements recorded in silver halide sensitized gelatin emulsions. Part 1: transmission holographic optical elements. Appl Opt 2001;40:622–32. [3] Walls HJ, Attridge GG. Basic photo science. London: Focal Press; 1977. p. 195–6. [4] James TH. The theory of the photographic process. New York: Macmillan; 1977. p. 433. [5] Van Veelen GF. Photographic science. New York: Focal Press; 1963. p. 179. [6] Madrigal RF, Blaya S, Carretero L, Ulibarrena M, Fimia A. Real time study of the response of ascorbic as developer agent in holographic emulsions: superadditivity effects. Opt Commun 2001;199:317–24. [7] Bjelkhagen HI. Silver-halide recording materials for holography and their processing. Berlin: Springer; 1995. [8] Hariharan P, Chidley CM. Photographic phase holograms: the influence of developer composition on scattering and diffraction efficiency. Appl Opt 1987;26:1230–4. [9] Hariharan P, Chidley CM. Rehalogenating bleaches for photographic phase holograms: the influence of halide type and concentration on diffraction efficiency and scattering. Appl Opt 1987;26:3895–8.