Dichromated Gelatin Research Articles

Preparation of Panchromatic Silver Halide Emulsion to Fabricate High Efficiency Multiplexed Volume Phase Holograms for Solar Concentration Application

Volume Phase Gratings (VPG) are often recorded using holographic emulsions such as photopolymer, Dichromated Gelatin (DCG), and silver halide. We employed silver halide emulsion to record the VPG in monochromatic red wavelength for solar concentration purposes. According to the Braggs condition, the recorded VPG's diffraction efficiency reaches its peak at the recorded angle and wavelength. For solar applications, we needed high diffraction efficiency over a wide angle and wavelength range. So, we captured multiplexed single VPG in our own panchromatic silver halide emulsion. The procedure of making panchromatic silver halide emulsion is described in depth. This technique is unique in that it achieves peak diffraction efficiency at broad wavelength and wide angle in a single multiplexed VPG. The panchromatic multiplexed VPG produced a high diffraction efficiency in wide-angle response with overall visible wavelengths. This study describes the high diffraction efficiency multiplexed VPG in its own manufactured panchromatic silver halide emulsion for solar concentrating applications.

Distributed Feedback Lasers by Thermal Nanoimprint of Perovskites Using Gelatin Gratings.

To date, thermal nanoimprint lithography (NIL) for patterning hybrid perovskites has always involved an intricate etching step of a hard stamp material or its master. Here, we demonstrate for the first time the successful nanopatterning of a perovskite film by NIL with a low-cost polymeric stamp. The stamp consists of a dichromated gelatin grating structured by holographic lithography. The one-dimensional grating is imprinted into a perovskite film at 95 °C and 90 MPa for 10 min, resulting in a high quality second-order distributed feedback (DFB) laser. The laser exhibits an excellent performance with a threshold of 81 μJ/cm2, a line width of 0.32 nm, and a pronounced linear polarization. This novel approach enables cost-effective fabrication of high-quality DFB lasers compatible with different perovskite compositions and photonic nanostructures for a wide range of applications.

Design and analysis of holographic optical elements for their use as couplers with appreciable efficiency at different optical transmission windows

The diffraction efficiency of a recorded Holographic optical element changes with change in wavelength of reconstruction wave even for on-Bragg angle reconstruction. Diffraction efficiency also falls with change in angle of reconstruction with respect to Bragg angle for reconstruction wave of a given wavelength. Therefore, to achieve appreciable diffraction efficiency operation of Holographic Optical Elements at different operating wavelengths, processing parameters namely film-thickness (d), depth of refractive index modulation (Δn), and fringe spacing (ᴧ) must be optimized accordingly. In present work thickness (d) of the film of the recording medium, depth of refractive index modulation (Δn), and fringe spacing (ᴧ) have been optimized for holographic optical elements to be recorded in dichromated gelatin medium to achieve maximum efficiency operation for three different optical transmission windows 800–900 nm, 1250 – 1350 nm and 1500–1600 nm operating at wavelengths 850 nm, 1310 nm, and 1550 nm respectively. A pair of such designed holographic optical elements can advantageously be used for coupling laser light from one fiber end to another fiber end. It is further shown that a single coupler consisting of properly designed holographic optical elements may be used for optical transmission windows 1250–1350 nm and 1500–1600 nm operating at wavelengths 1310 nm, and 1550 nm respectively.

Surface Profile Studies of Photoinduced Gratings Made with DCG Films with Optional Papain Development.

The use of surface relief structures is increasing in the field of optics. A study of photoinduced relief using dichromated gelatin films with different thickness is described in this paper. Two light sources were used: a laser (λ = 468 nm) and an ultraviolet mercury-metal halide lamp. Gratings with low spatial frequencies were contact-copied on the DCG (dichromated gelatin) films. Two development processes were used, one included washing the plates with just water and the other with a mixture of water and papain. This enzyme is used to improve the gratings’ relief which was studied with a profilometer. For the development process with just water, it was found that when gratings were recorded using visible or UV light, the height profile inversely correlated to spatial frequencies. For short exposure times, the reliefs showed a sinusoidal profile. When visible light was used, the DCG areas where the Ronchi grating had transparent slits showed a flat relief and the areas where the Ronchi grating had opaque slits showed a round peak, with the peak being taller than the flat surface. In contrast, when UV light was used, the flat surfaces were taller than the peaks. The relief height increased up to seven times when papain was used.

Improvement of the technology for manufacturing relief holographic gratings on dichromated gelatin irradiated with short-wave UV radiation

A new variant of manufacturing high-frequency holographic gratings with a spatial frequency up to 1500 mm-1 on layers of dichromated gelatin (DCG), in the processing technology of which water procedures are completely excluded, is proposed. The method is based on the use of glacial acetic acid after the photodestruction of layers by exposure to short-wave UV radiation instead of the standard method of processing holographic structures registered by coherent He-Cd laser radiation. In the course of the experiments, relief-phase holographic gratings with high diffraction efficiency up to 64% were obtained, regardless of the thickness of the DCG layers. Keywords: holographic diffraction gratings, dichromated gelatin, short-wave UV radiation, surface relief, diffraction efficiency, glacial acetic acid, isopropanol.

Dichromated gelatin, an efficient material for the fabrication of wavelength selective holographic solar concentrators for high-efficiency operation

The use of holographic concentrators for photovoltaic solar concentration is a very attractive proposition as the hologram can be designed to be wavelength selective i.e. it can be designed to disperse, diffract and concentrate specific spectral regions of the solar spectrum with maximum efficiency in a spectrum splitting solar cell system. The practical application of highly efficient holographic solar concentrators requires intensive as well as extensive research work on the choice of the appropriate recording material. Among the available materials for recording holographic concentrators, Dichromated gelatin (DCG) is considered to be one of the best materials because maximum diffraction efficiency and high value of modulation in refractive index (reported value is up to 0.08) can be achievable in DCG film. Also, DCG has high resolution and shows low scattering noise.In present paper theoretical study on refractive index modulation capability of dichromated gelatin (DCG) for same and different thickness of DCG film have been performed to design a holographic concentrator for high-efficiency wavelength selective performance. To validate the theoretical results, holographic concentrators have been recorded in DCG film with different values of index modulation, and the typically recorded holographic concentrators were reconstructed with different wavelengths of the laser source, and corresponding diffracted power is measured. A comparison between experimental results and theoretical results are presented. Experimental and theoretical study reveals that for a constant film thickness low value of modulation in the refractive index gives maximum efficiency in lower wavelength regions and high values of index modulation are desired for maximum efficiency in higher wavelength regions. Further for a constant value of index modulation maximum efficiency gets shifted towards higher wavelength regions with an increase in film thickness. Theoretically simulated curves show that by appropriate selection of index modulation and film thickness, holographic concentrator may be fabricated to use almost entire useful portion of the solar radiation with reasonably high diffraction efficiency.

Real-time characterization of gelatin doped with potassium dichromate as a photosensitive material

Dichromated gelatins are commonly fabricated with ammonium dichromate as a sensitizer. A lesscommon alternative is to employ potassium dichromate, due to the unable characterization information of such process. This article aims to prove the efficiency of potassium dichromate as a sensitizer in dichromated gelatins without a development process. The study was performed measuring in real-time the diffraction efficiency of holographic gratings recorded in gelatin sensitized with potassium dichromate as a photosensitive material. The holographic gratings were recorded with an Ar laser with a 532 nm wavelength varying parameters in the photosensitive material such as cell thickness, concentration between gelatin and potassium dichromate as well as the angle of interference between the two light beams and the laser power. The optimum parameters combination yielded a 19% of diffraction efficiency at the first diffraction order and allowed to record Fourier holograms. The results obtained prove the good performance of potassium dichromate as a sensitizer. Furthermore, the recording of holograms in the dichromated gelatin proposed here could be a very efficient way to make diffractive elements for uncomplicated practices in university laboratories due to it can be massively produced in any laboratory with minimum requirements at low cost.

Blue and Deep‐Blue‐Emitting Organic Lasers with Top‐Layer Distributed Feedback Resonators

AbstractAll‐solution processed surface‐emitting organic distributed feedback lasers are attractive devices for low‐cost applications. Here, lasers emitting in the spectral region between 375 and 475 nm, in which both active material and resonator (1D relief gratings) are based on solution‐processable polymer films, are reported. Ten different organic compounds dispersed in polystyrene are used as active layers of the prepared devices. They include various carbon‐bridged oligo(p‐phenylenevinylene) (COPVn, with n = 1,2) derivatives and two terfluorene compounds. The synthesis and complete optical and amplified spontaneous emission properties of one of the COPV1 compounds, COPV1(Me)‐t‐Bu, designed for deep‐blue emission, are also included. The feasibility of the resonator fabrication, performed by holographic lithography with a dichromated gelatine photoresist over the active film, is successfully demonstrated for all devices. Remarkably, no resolution limitations are found even for the lowest grating period (235 nm) required for the fabrication of the laser based on COPV1(Me)‐t‐Bu. It is also demonstrated that the rectangular grating profile with duty cycle 0.75:0.25 (hill:valley) is very convenient to optimize the resonator efficacy.

The Application of Heat Treatment in the Formation of Relief-Phase Holographic Structures on Dichromed Gelatin

A new method of formation of relief-phase holographic structure on dichromated gelatin (DCG) layers has been proposed. The method is based on two types of alternative effects on gelatin: structuring by selective light tanning by coherent He–Cd laser radiation and destruction by short-wave UV radiation. A time-shortened water treatment of samples interrupted by an isopropanol bath was previously proposed to obtain highly effective holographic relief structures in the region of high spatial frequencies up to 1500 mm–1. In this paper, it has been proposed to abandon the water treatment of dichromated gelatin layers and replace it by heating the sample during its processing with short-wave UV radiation. In the course of experiments, a steady increase in the diffraction efficiency has been obtained regardless of the spatial frequency and dichromated gelatin layer thickness, which has been explained by the formation of a relief holographic structure because of the evaporation and shrinkage of gelatin areas degraded by UV radiation under the influence of high temperature.

Woodburytype: A historical process resurrected by modern methods


 
 
 One of the technological achievements of the 19th century was the mass reproduction of photographic images. Woodburytype was thefirst commercially successful photomechanical continuous tone printing method, of unsurpassed quality until today. Along with Collotype and Goupil gravure, it used the relief of dichromated gelatin exposed to light as the basis for the printing plates. In this article we will discuss the historical printing processes and present how a) modern embodiments of the printing plates can be made by either CNC milling or using photopolymer plates and b) how optimal contrast and grayscale can be achieved by ink formulations tuned to the relief depth of the printing plate.
 
 

Mechanisms of Generation of Relief High-Frequency Holographic Structures on Dichromated Gelatin Exposed to Shortwave UV Radiation

The application of two types of alternative action on gelatin in the layers of dichromated gelatin (DCG) was considered: structuring with the use of selective light tanning by the radiation of a He–Cd laser ( $$\lambda=440$$ nm) and destruction performed by exposure of layers to short-wave ultraviolet radiation ( $$\lambda<270$$ nm). The crucial role of UV exposure of samples in generating high-frequency relief-phase gratings with diffraction efficiency higher than 50 $$\%$$ on DCG layers thinner than 2 $$\mu$$ m is shown. It is noted that the application of traditional treatment methods of DCG layers leads to smoothened relief due to action of surface tension forces at high spatial frequencies. In addition, significant broadening of the domain of registered spatial frequencies (up to 1500 mm $${}^{-1}$$ ) for recording relief holographic gratings is achieved by applying the modified technique of gelatin treatment based on reduced time of water procedures and by using the isopropanol baths for quick layer dehydration.

Применение термообработки при формировании рельефно-фазовых голографических структур на бихромированном желатине

A new method is proposed for the formation of a relief phase holographic structure on layers of dichromated gelatin (DCG). The method is based on the application of two types of alternative effects on gelatin: structuring using selective light tanning with coherent radiation from a He-Cd laser and destruction by irradiating the layers with short-wave UV radiation. To obtain highly effective holographic relief structures in the region of high spatial frequencies, up to 1500 mm–1, a time-shortened water treatment of samples, interrupted by an isopropanol bath, was previously proposed. In this paper, it is proposed to abandon the water treatment of DCG layers and replace it with heating the sample during irradiation with short-wave UV radiation. In the course of experiments, a steady increase in the diffraction efficiency was obtained regardless of the spatial frequency and thickness of the DCG layer, which is explained by the formation of a relief holographic structure due to evaporation and shrinkage of gelatin areas destroyed by UV radiation under the influence of high temperature.

High-frequency relief holographic gratings created by exposing dichromated gelatin to short-wave UV radiation

The possibility of creating effective relief holographic gratings with a high spatial frequency of 1500 mm−1 on the layers of dichromated gelatin (DCG) using the destructive effect of short-wave UV radiation on gelatin is shown for the first time.

Высокочастотные рельефно-фазовые голографические решетки на обработанном коротковолновым УФ-излучением бихромированном желатине

For the first time, the possibility of creating relief-phase holographic gratings with a high spatial frequency of 1500 mm-1 on dichromate gelatin (DCG) layers using the destructive effect of short-wave UV radiation on gelatin is shown.

High-sensitivity humidity sensing of side-polished optical fiber with polymer nanostructure cladding.

This paper presented a high-sensitivity humidity sensor comprised of a side-polished fiber with polymer nanostructure cladding, which was constructed by dehydrating dichromate gelatin film on the polished surface. Due to the intermodal interference of the core mode and cladding mode, two main transmission dips were observed at 1184.4 nm and 1325.6 nm. These two transmission dips showed significant sensitivity to humidity. The position of transmission dip at 1325.6 nm shifted 22 nm while the relative humidity (RH) changed from 30% RH to 50% RH. The humidity sensitivity was up to 1.12 nm/% RH, and its linear correlation was 98.45%. The humidity sensing characteristic of nanostructure cladding fiber was successfully demonstrated. This novel sensor is compatible with optical fiber systems and has high potential in optical sensing applications.

Rediscovering Ducos du Hauron's Color Photography through a Review of His Three‐Color Printing Processes and Synchrotron Microanalysis of His Prints

AbstractLouis Ducos du Huron (1837–1920) dedicated his entire life to the elaboration of physical–chemical processes for color photography. This study aimed at highlighting his unique contribution to three‐color printing through 1) an in‐depth review of the many protocols he published and 2) the synchrotron‐based IR and X‐ray microanalysis of fragments sampled in three artworks. Ducos du Hauron's method relied on the preparation and assembly of three monochromes (red, blue, yellow). This study brings to light complex multistep recipes based on photochemistry (carbon print), organic, and inorganic chemistry. The various ingredients involved (e.g., pigments, dichromate gelatin, collodion, resin) were identified and localized through their spectroscopic signature, confirming the relevance of synchrotron spectromicroscopy for the characterization of historical photographs. The impressive correlation between texts and chemical analyses calls for a wider application to the history of photography.

Rediscovering Ducos du Hauron's Color Photography through a Review of His Three-Color Printing Processes and Synchrotron Microanalysis of His Prints.

Louis Ducos du Huron (1837-1920) dedicated his entire life to the elaboration of physical-chemical processes for color photography. This study aimed at highlighting his unique contribution to three-color printing through 1) an in-depth review of the many protocols he published and 2) the synchrotron-based IR and X-ray microanalysis of fragments sampled in three artworks. Ducos du Hauron's method relied on the preparation and assembly of three monochromes (red, blue, yellow). This study brings to light complex multistep recipes based on photochemistry (carbon print), organic, and inorganic chemistry. The various ingredients involved (e.g., pigments, dichromate gelatin, collodion, resin) were identified and localized through their spectroscopic signature, confirming the relevance of synchrotron spectromicroscopy for the characterization of historical photographs. The impressive correlation between texts and chemical analyses calls for a wider application to the history of photography.

The Transfer of a Holographic Structure from Dihromated Gelatin Layers on a Polymethylmethacrylate Substrate

The possibility of the transfer of a holographic structure that was originally registered on layers of dichromated gelatin (DCG) onto a substrate material of polymethylmethacrylate (PMMA) has been shown. The use of a selective destructive effect of short-wave UV radiation with a wavelength that is less than 270 nm is the basis of the mechanism of formation of secondary relief-phase holographic structure on the surface of PMMA. The optimization of processing modes and selection of developing compositions which are based on isopropanol and methylisobutylketone (MIBK) have been carried out, which made it possible to create reliefphase holographic gratings with high diffraction efficiency (DE) of about 25% and the maximum depth of the surface relief of the order of 1 μm on the substrates of PMMA.

Design and fabrication of cascaded dichromate gelatin holographic filters for spectrum-splitting PV systems

The technique of designing, optimizing, and fabricating broadband volume transmission holograms using dichromate gelatin (DCG) is summarized for solar spectrum-splitting applications. The spectrum-splitting photovoltaic (PV) system uses a series of single-bandgap PV cells that have different spectral conversion efficiency properties to more fully utilize the solar spectrum. In such a system, one or more high-performance optical filters are usually required to split the solar spectrum and efficiently send them to the corresponding PV cells. An ideal spectral filter should have a rectangular shape with sharp transition wavelengths. A methodology of designing and modeling a transmission DCG hologram using coupled wave analysis for different PV bandgap combinations is described. To achieve a broad diffraction bandwidth and sharp cutoff wavelength, a cascaded structure of multiple thick holograms is described. A search algorithm is then developed to optimize both single- and two-layer cascaded holographic spectrum-splitting elements for the best bandgap combinations of two- and three-junction spectrum-splitting photovoltaic (SSPV) systems illuminated under the AM1.5 solar spectrum. The power conversion efficiencies of the optimized systems are found to be 42.56% and 48.41%, respectively, using the detailed balance method, and show an improvement compared with a tandem multijunction system. A fabrication method for cascaded DCG holographic filters is also described and used to prototype the optimized filter for the three-junction SSPV system.

Properties of holographic structures on dichromated gelatin subjected to ultraviolet radiation

The results of experiments on the effect of ultraviolet (UV) radiation with a wavelength of less than 250–270 nm on holographic structures recorded on dichromated gelatin (DCG) layers are presented. A tenfold increase in the height of the surface relief and an increase in the diffraction efficiency of the gratings to approximately 30% over a wide range of thicknesses of DCG layers—1 to 80 μm—are obtained. The experiments show that the main cause of the formation of the surface relief is the variable tanning of the layer, which occurs when the interference pattern is recorded with coherent radiation at a wavelength of 0.44 μm and serves as a factor that modulates the impact of UV radiation.