Transmittance Measurements Research Articles

Effects of Solution pH on Chemical Bath Deposited Iron-Sulfide-Oxide with Tartaric Acid Presence

A chemical bath deposition (CBD) contained sodium thiosulfate (Na2S2O3), iron (II) sulfate heptahydrate (FeSO4.7H2O), and L(+)-tartaric acid (C4H6O6) as the complexing agent has been used to deposit the iron-sulfide-oxide (FeSxOy) films. The effects of different solution pH (5.0-9.0) on film properties were investigated. The thicknesses of the film analysed from the cross-sectional images of Scanning Electron Microscopy (SEM) showed the thickness of the film is increasing with increasing pH. The X-Ray Diffraction (XRD) pattern and the hot probe method revealed that all the deposited films are crystalline, and possess n-type semiconductor behaviour due to high oxygen content (around 72-82%). Larger crystallite sizes with extra peaks of goethite and hematite were present for the films with pH > 7.0, while, better film uniformity and grains distribution, as well as clear absorption edge in transmittance measurement, were obtained for the film with pH 5.0.

355 nm Nanosecond Ultraviolet Pulsed Laser Annealing Effects on Amorphous In-Ga-ZnO Thin Film Transistors.

Bottom-gate thin-film transistors (TFTs) with n-type amorphous indium-gallium-zinc oxide (a-IGZO) active channels and indium-tin oxide (ITO) source/drain electrodes were fabricated. Then, an ultraviolet (UV) nanosecond pulsed laser with a wavelength of 355 nm was scanned to locally anneal the active channel at various laser powers. After laser annealing, negative shifts in the threshold voltages and enhanced on-currents were observed at laser powers ranging from 54 to 120 mW. The energy band gap and work function of a-IGZO extracted from the transmittance and ultraviolet photoelectron spectroscopy (UPS) measurement data confirm that different energy band structures for the ITO electrode/a-IGZO channel were established depending on the laser annealing conditions. Based on these observations, the electron injection mechanism from ITO electrodes to a-IGZO channels was analyzed. The results show that the selective laser annealing process can improve the electrical performance of the a-IGZO TFTs without any thermal damage to the substrate.

Light transmittance measurement method of solid rocket motor plume based on laser modulation spectrum analysis

AbstractThe light transmittance measurement method, which is used to characterize smoke characteristic signal of solid rocket motor plume, can provide important reference for development and design of low smoke characteristic signal solid propellants and motors. The light transmittance measurement method of solid rocket motor plume based on laser modulation spectrum analysis is proposed in this paper. By using a 405 nm laser as the light source and a narrow‐band filter detection method, the influence of plume radiation on the measurement of light transmittance of solid rocket motor plume smoke can be minimized. Additionally, combined with the laser modulation spectrum analysis technology, the signal amplitude is selected by the laser modulation frequency to improve the signal‐to‐noise ratio of the signal. Compared with the laser constant current measuring mode, laser high‐frequency modulation measuring mode with spectrum analysis effectively improves the optical transmittance measurement accuracy. Based on this, a solid rocket motor plume smoke transmittance test system is developed to measure the plume smoke of standard test motors with different propellants and combustion chamber pressures. The results demonstrate that the system can effectively measure the light transmittance of the plume smoke. The light transmittance of solid rocket motor plume can be increased by reducing the aluminum content of solid propellant or increasing the pressure of the combustion chamber. Thus, this research provides an effective measuring tool for evaluating smoke concentration of solid rocket motor plume, which is beneficial to develop low smoke characteristic signal solid propellants and motors.

Ultrafast magnetisation dynamics in a chromium-based Prussian blue analogue

An experimental framework comprising transient transmittance and time-resolved magneto-optical measurements was used to observe ultrafast photophysics and demagnetisation dynamics in thin films of mixed-valence Cr–Cr Prussian blue analogue.

Дисперсии оптических констант тонких пленок селенидов меди, полученных методом вакуумно-термического испарения

Thin films of Cu/Se system were obtained by vacuum-thermal evaporation of Se and Cu. The influence of the mass of Cu deposited on the phase and optical characteristics of the synthesized films after their thermal annealing was investigated at a fixed mass of Se deposited. Thin films containing trigonal selenium, various phases of copper selenides, and embedded Cu nanoparticles were obtained by varying the mass of Cu. Transmittance and reflectance spectra, as well as ellipsometric parameters characterizing amplitude and phase changes of reflected light, of the obtained films in a wide range of wavelengths, including UV, visible and near-IR ranges at various angles of light incidence on the film were measured using a spectroscopic ellipsometer SER 850. Using modeling , the dispersions of refractive index, extinction coefficient, absorption coefficient, as well as the spectra of real and imaginary parts of dielectric permittivity were found from the recorded spectra. The spectra of extinction coefficient and absorption coefficient have also been determined from the direct measurements of transmittance and reflectance spectra recorded with the ellipsometer. The findings obtained with the two methods are in good agreement. The presented results show that the synthesized films have unique optical properties suitable for photonics and optoelectronics applications.

Novel Time-Saving Technique to Measure the 2D Complex Profile of Spectral Transmittance of Linearly Variable Filters and Assessing Homogeneity of Optically Transparent Materials

Emerging technologies for coating new types of filters, such as linearly variable bandpass filters, urges new kind of measurement systems requiring accurate and time-saving spatially resolved transmittance measurements. On the other hand, one of the main uses of coated filters is standardization use; e.g., as certified reference materials (CRMs) for transmittance and absorbance standards. In this case, the homogeneity assessment is of great interest. To do such measurements with low uncertainty, spatial scanning methods using reference double-beam spectrophotometers are routinely used. High time consumption and relatively high-cost are disadvantages of this traditional method. In this work, we propose a new system based on an imaging technique. The newly developed system comprises a quartz tungsten halogen (QTH)-based illuminator, with collimator and coupling optics, a double-grating monochromator, customized integrating sphere, and scientific highly digitized, high-resolution and dynamic range Si-based CCD (monochrome) camera. The system is time-saving: in one-shot we may measure the spatial transmittance distribution of the samples (e.g. filters) without separately measuring the reference (air), which has many instability issues. Validation measurements using standard filters are presented. Systematic errors may be studied and corrected for. Many types of filters and liquids, for instance chemical reference materials (RMs), may be measured and reported. Uncertainty of spatial, spectral and radiometric components are studied carefully and estimated. The combined uncertainty evaluation has shown that relatively low uncertainty levels may be achieved, specially in the visible range (U < 1 %, k=2 ). Spatially-resolved data with different curves at different positions (spatial points) are shown in the spectral range of 380 nm through 950 nm. The combined uncertainties at some spectral points are presented and proved to be sample- and wavelength-dependent at all the points in the field-of-view (FOV) of the CCD camera.

Cation effects and charge inversion contribute to the electrostatic stabilisation of protein bioconjugates in neat ionic liquids.

Dispersing and stabilising proteins in ionic liquids (ILs) provides significant opportunities for green solvent-based biocatalysis, especially in industrial processes at elevated temperatures. While unmodified proteins undergo denaturation, their polymer-conjugated counterparts have been stabilised in neat ILs. However, the nature of interactions and the generality of protein-bioconjugate stabilisation in neat ILs require further understanding. Using a combination of different physio-chemical experimental tools and molecular dynamics (MD) simulations, here we investigate the dispersion and driving force for the stabilisation of bioconjugates in neat ILs. Solvent-free bioconjugates of different proteins, viz. myoglobin, α-chymotrypsin, and regenerated silk fibroin having predominant α-helical, β-sheet, and random coiled secondary structures, respectively, were prepared by electrostatic coupling with polyethylene-glycol (PEG)-based polymer-surfactant (PS). Protic IL (PIL, N-methyl-2-pyrolidonium trifluoromethane sulfonate; [NMP][OTF]) and aprotic ionic liquid (AIL, 1-methyl-3-(4-sulfobutyl)-1H-imidazol-3-ium trifluoromethane sulfonate; [MEZ][OTF]) were synthesized to study the bioconjugate dispersion. Interestingly, time-dependent polarised optical microscopy combined with transmittance measurements showed complete dispersion of all bioconjugates only in AIL. MD simulations of the PS-cCT bioconjugate were carried out in the same ILs as the experiments. The surface electrostatic potential of PS-cCT reversed from positive in PIL to negative in AIL due to overcharging by the AIL anion and lower mobility of the AIL cation. Strong screening of electrostatic potentials between two PS-cCT complexes in PIL resulted in reduced dispersion stability. Lower diffusivity of long alkyl chain [MEZ] cations of AIL leads to a depletion zone of IL ions between the two PS-cCT complexes (separation <70 Å), thus resulting in a significant negative potential between the complexes. Hence, protein bioconjugates in AIL were stabilised by a combination of surface overcharging and steric exclusion of [MEZ] cations from the space between the approaching bioconjugate complexes.

Energy Spectrum and Properties of SiC: Using Two-Photon Absorption for Different Harmonics

This paper describes a methodology for studying the energy spectrum and characteristics of Silicon Carbide (SiC) semiconductor materials, utilizing various harmonics for two-photon absorption (TPA). The approach involves developing theoretical models to simulate the energy levels and transitions of SiC, based on the TPA process. By analyzing the resulting spectra obtained by varying the harmonic order, the energy spectrum, and properties of SiC are explored. In this work also includes a comparison of the energy spectrum and properties of SiC for single and two-photon absorption, providing insights into the distinctive features of SiC under these conditions. In particularly absorption co-efficient of the material was calculated from optical transmittance and reflectance measurements at room temperature (300 K) in the wavelength range of 200 -900 nm. In addition, Gaussian functions centered at different energies were modeled using TPA in SiC materials and their contribution to the Harmonic Generation (HG) signal was calculated.

Estimation of Oak Leaf Functional Traits for California Woodland Savannas and Mixed Forests: Comparison between Statistical, Physical, and Hybrid Methods Using Spectroscopy

Key leaf functional traits, such as chlorophyll and carotenoids content (Cab and Cxc), equivalent water thickness (EWT), and leaf mass per area (LMA), are essential to the characterization and monitoring of ecosystem function. Spectroscopy provides access to these four leaf traits by relying on their specific spectral absorptions over the 0.4–2.5 µm domain. In this study, we compare the performance of three categories of estimation methods to retrieve these four leaf traits from laboratory directional-hemispherical leaf reflectance and transmittance measurements: statistical, physical, and hybrid methods. To this aim, a dataset pooling samples from 114 deciduous and evergreen oak trees was collected on four sites in California (woodland savannas and mixed forests) over three seasons (spring, summer and fall) and was used to assess the performance of each method. Physical and hybrid methods were based on the PROSPECT leaf radiative transfer model. Physical methods included inversion of PROSPECT from iterative algorithms and look-up table (LUT)-based inversion. For LUT-based methods, two distance functions and two sampling schemes were tested. For statistical and hybrid methods, four distinct machine learning regression algorithms were compared: ridge, partial least squares regression (PLSR), Gaussian process regression (GPR), and random forest regression (RFR). In addition, we evaluated the transferability of statistical methods using an independent dataset (ANGERS Leaf optical properties database) to train the regression algorithms. Thus, a total of 17 estimations were compared. Firstly, we studied the PROSPECT leaf structural parameter N retrieved by iterative inversions and its distribution over our oak-specific dataset. N showed a more pronounced seasonal dependency for the deciduous species than for the evergreen species. For the four traits, the statistical methods trained on our dataset outperformed the PROSPECT-based methods. More particularly, statistical methods using GPR yielded the most accurate estimates (RMSE = 5.0 µg·cm−2; 1.3 µg·cm−2; 0.0009 cm; and 0.0009 g·cm−2 for Cab, Cxc, EWT, and LMA, respectively). Among the PROSPECT-based methods, the iterative inversion of this model led to the most accurate results for Cab, Cxc, and EWT (RMSE = 7.8 µg·cm−2; 2.0 µg·cm−2; and 0.0035 cm, respectively), while for LMA, a hybrid method with RFR (RMSE = 0.0030 g·cm−2) was the most accurate. These results showed that estimation accuracy is independent of the season. Considering the transferability of statistical methods, for the four leaf traits, estimation performance was inferior for estimators built on the ANGERS database compared to estimators built exclusively on our dataset. However, for EWT and LMA, we demonstrated that these types of statistical methods lead to better estimation accuracy than PROSPECT-based methods (RMSE = 0.0016 cm and 0.0013 g·cm−2 respectively). Finally, our results showed that more differences were observed between plant functional types than between species or seasons.

Rain Attenuations Based on Drop Size Distribution (DSD) Model and Empirical Model at Low THz Frequencies

Rain attenuation based on the drop size distribution (DSD) with different rainfall rates (R) at low THz frequencies is investigated in this paper. The rain attenuation is calculated using the DSD measured for one year and the extinction cross-section (ECS) by the Mie scattering theory. Moreover, the obtained specific rain attenuation is verified by the empirical model using the measurement system consisting of a transmitter, a receiver, and weather measurement units. We measured the received power against the uniform transmitted power at 240, 270, and 300 GHz on the rooftop of the National Radio Research Agency (RRA) in Korea during the same period as the DSD measurement period. After curve fitting by regression analysis, we compared both rain attenuations obtained in two methods with the recommendation International Telecommunication Union Radiocommunication Sector (ITU-R) P.838-3. The root mean square errors (RMSEs) of the DSD model are 2.8977, 2.8646, and 2.8331 at 240, 270, and 300 GHz, respectively. The calculated result using the Mie scattering and the measured DSD methods shows the best fit to the data of the ITU-R recommendation for a rainfall rate of up to 5 mm/h. On the other hand, the empirical results using the T/Rx antenna system are slightly higher compared to the data of the ITU-R recommendation. As the rainfall rate increases, the difference between our results and ITU-R recommendation increases. This study will be useful for predicting rain attenuation for terrestrial wireless links operating at low THz frequencies.

Rapid Ascent of Hollow Particles in Water Induced by an Electric Field

A novel method has been proposed to induce rapid upward movement of colloidal particles with a density lower than water by applying an electric field of several V/mm in water. This phenomenon, known as the Electrically Induced Rapid Sedimentation (ERS) effect, marks the first occurrence of ‘rapid upward movement of colloidal particles’ within the scope of this phenomenon. Focusing on hollow particles, an investigation of the ERS effect was conducted through transmittance measurement. The hollow particles in water showed a drastic increase in ascending velocity through the application of an electric field. The ascending velocity raised when increasing the electric field strength. Utilizing a quasi-DC electric field (an extremely low-frequency AC electric field), aggregate structures were captured for the first time.

Influence of oxygen on the optical and electrical properties of magnetron-sputtered indium tin oxide thin films at ambient temperature

Indium Tin Oxide (ITO) thin films are commonly used as transparent conductive layers in the production of solar cells. ITO films are typically heat-treated at temperatures exceeding 200 °C after magnetron sputtering to optimize the physical, optical, and electrical characteristics for photovoltaic devices. This high temperature heating procedure greatly limits the use of potential substrates, particularly those comprised of low-temperature-rated polymers. Herein, we examine the physical, optical, and electrical transport effects of oxygen:argon plasmas during radio frequency magnetron sputtering of ITO on glass and flexible polymer surfaces without subsequent heat treatment. ITO thin films were characterized via sheet resistance testing, UV–Vis spectroscopy, X-ray diffraction, and scanning electron microscopy imaging. Sheet resistance measurements revealed an increase in surface resistance with increasing oxygen concentration during sputtering. UV–Vis optical transmittance measurements demonstrated an improvement in optical transmittance with an increase in oxygen concentration reaching a maximum transmittance at an oxygen concentration of 1-2%. Most importantly, it was discovered that producing bilayers of ITO with pure argon sputtered plasmas followed by oxygen:argon plasmas produced ITO thin films with suitable resistance and transmittance without the need for high temperature post annealing. These results highlight a methodology for the deposition of ITO thin films on temperature sensitive substrates for flexible photovoltaics and low-cost module production.

Polarization-dependent photoinduced metal–insulator transitions in manganites

In correlated oxides, collaborative manipulation on light intensity, wavelength, pulse duration and polarization has yielded many exotic discoveries, such as phase transitions and novel quantum states. In view of potential optoelectronic applications, tailoring long-lived static properties by light-induced effects is highly desirable. So far, the polarization state of light has rarely been reported as a control parameter for this purpose. Here, we report polarization-dependent metal-to-insulator transition (MIT) in phase-separated manganite thin films, introducing a new degree of freedom to control static MIT. Specifically, we observed giant photoinduced resistance jumps with striking features: (1) a single resistance jump occurs upon a linearly polarized light incident with a chosen polarization angle, and a second resistance jump occurs when the polarization angle changes; (2) the amplitude of the second resistance jump depends sensitively on the actual change of the polarization angles. Linear transmittance measurements reveal that the origin of the above phenomena is closely related to the coexistence of anisotropic micro-domains. Our results represent a first step to utilize light polarization as an active knob to manipulate static phase transitions, pointing towards new pathways for nonvolatile optoelectronic devices and sensors.

Enhanced thermo-electro-optical and dielectric properties of carbon nanoparticle-doped polymer dispersed liquid crystal based switchable windows

The effect of temperature as well as voltage on switchable smart windows was studied. These smart windows are composites of a polymer and a liquid crystal (LC) and collectively known as polymer dispersed liquid crystal (PDLC) films. In order to enhance the efficiency of the smart windows/PDLC films, the LC material was doped with carbon nano particles (CNP) in various concentrations ranging from 0 to 0.1%. To examine the efficacy and the temperature dependent performance of the CNP doped PDLC (CPDLC) film, firstly morphological and thermo-morphological studies were performed using polarizing optical microscopy (POM). POM in combination with temperature changes allows to record texture changes and the nematic-isotropic transition of the composite films for applied voltage. The complete electro-optical (EO) study comprising of voltage and temperature dependent transmittance, threshold voltage (Vth), saturation voltage (Vsat), contrast ratio (CR) and response time measurement was performed through an assembled EO set-up. To infer intermolecular cooperative processes between polymer and the dipoles of the LC, the relaxation mechanism of the composite films for various temperatures was studied by employing Debye and Cole-Cole models in dielectric spectroscopy. Parameters like dielectric strength and dissipation factor were determined to allow optimization of the CPDLC films.

Influence of fitting algorithms on thickness determination during monitoring of optical coatings

The monitoring of thickness evolution during the deposition of optical interference coatings is widely performed by transmittance measurements and continuous comparison with theoretical models. The fitted thickness of the actual layer is influenced by the quality of the signal. Effects from light path, substrate and spectrometers result in deviations because these are often not part of the models. We show an implementation of these unmodeled effects in the fitting algorithms. The outcome of different configurations while coating the same optical filter design is compared. Additionally, the time consumption of these strategies is investigated to verify their suitability for production.

Active Modulation of Er3+ Emission Lifetime by VO2 Phase‐Change Thin Films

The active modulation of optical response of quantum emitters at the nanoscale is of paramount importance to realize tunable light sources for nanophotonic devices. Herein, a thin film of phase‐change material (VO2) is coupled to a 20 nm‐thick silica layer embedding Er3+ ions, and it is demonstrated how the active tuning of the local density of optical states near the erbium emitters provided by the thermally induced semiconductor‐to‐metal transition of VO2 can be used to dynamically control the Er3+ emission lifetime at telecom wavelength (1.54 μm). A decay rate contrast of a factor 2 is obtained between high temperature (90 °C), when VO2 is metallic, and room temperature, when VO2 is semiconductor, in agreement with calculations performed with the classical dipole oscillator analytical model. A hysteretic behavior is observed by measuring the Er3+ lifetime as a function of the temperature, whose parameters are consistent with those of grazing incidence X‐ray diffraction and optical transmittance measurements. The fractions of Er3+ ions that couple with VO2 in each phase at the different temperatures are determined by the analysis of the temporal decays. The results make the investigated system an optimal candidate for the development of tunable photon sources at telecom wavelength.

Light transmittance in human atrial tissue and transthoracic illumination in rats support translatability of optogenetic cardioversion of AF

Abstract Background Optogenetics could offer a solution to the current lack of an ambulatory method for rapid automated cardioversion of AF, but key translational aspects remain to be studied. Objective To investigate whether optogenetic cardioversion of AF is effective in the aged heart and whether sufficient light penetrates the human atrial wall. Methods Atria of adult (7 weeks old) and aged (2 years old) rats were optogenetically modified to express light-gated ion channels (i.e. ReaChR), followed by AF induction and atrial illumination to determine effectivity of optogenetic cardioversion. The irradiance level was determined by light transmittance measurements on human atrial tissue. Results AF could be effectively terminated in remodelled atria of aged rats (97%, n=6). Next, in terms of ReaChR activation, it was shown that light pulses of 25mW/mm2 are expected to fully penetrate the human atrial wall (∼2 mm). Applying such irradiation onto the chest of adult rats resulted in full transthoracic illumination (also ∼2 mm) as evidenced by optogenetic cardioversion of AF (90%, n=4). Conclusion Optogenetic cardioversion of AF is effective in the aged rat heart and can also be realized with irradiation levels compatible with human atrial transmural light penetration.

Elaboration of CuS nanomaterials via hydrothermal route: Examining physical properties and photocatalytic potential

The stable and efficient CuS photocatalyst was elaborated by the facile hydrothermal route at 140 °C for various durations, from copper chloride (CuCl2) and thiourea (SC(NH2)2) aqueous solutions. Characterization techniques such as X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) coupled with energy-dispersive of X-ray system (EDX) analysis, showed the formation of pure CuS nanomaterial. Electrochemical impedance spectroscopy (EIS) revealed that synthesized CuS exhibited a quick charge transfer at high frequencies and a diffusion or transport of ions from the electrolyte to the electrode surface at medium and low frequencies. Hall effect measurement indicated that all prepared CuS are a p-type semiconductors with a hole concentration on the order of 1020 cm−3. A decrease in the hole concentration with increasing heat treatment duration was observed and related to the healing of Cu vacancies. Transmittance and absorbance measurements showed that all samples interacted with light, exhibiting a prominent peak around 600 nm. Tauc method revealed an increase of the optical band gap values from 1.56 to 1.75 eV with the increment of heat treatment duration. Photocatalytic activity of CuS prepared at 140 °C for 16 h was determined by measuring the degradation rate of methylene blue (MB) dye under UV light in the absence and presence of hydrogen peroxide (H2O2). The results demonstrate CuS as a stable and efficient photocatalyst and underscore its potential for application in wastewater purification processes.

Cigarette smoke and tobacco heating aerosol on the aging of clear aligners.

The treatments with clear aligners (CA) showed an exponential higher percentage in the last years being almost invisible with major patient acceptability and a resulting improvement in quality of life. CA are composed of thermoplastic polyurethane not inert but subjected to changes due to heating and humidity, chewing forces, and prolonged exposure to enzymes in saliva in the oral cavity and external factors. Cigarette smoke (CS) and the aerosol produced by tobacco products with reduced health risks may be considered among the external factors affecting CA. The purpose of this study was the assessment of optical properties (absorbance and transmittance) and roughness of CA after in vitro aging due to exposition to CS and THS2.2, compared to controls. The secondary objective will be the investigation of CS and THS2.2 effects on resin composite inside aligners used for attachments during treatment with CA. A total number of 60 CA units will be used and equally divided in three different groups (20 in each): CS group exposed to reference cigarettes smoking, THS2.2 group exposed to aerosol from 20 heat-not-burn sticks, and control group, CG to pure air only. The aligners will present ten introflection for the attachments on the anterior part. In accordance with ISO standard 3402, 3R4F cigarettes and THS2.2 tobacco sticks must undergo conditioning for a minimum of 48 hours and a maximum of 21 days at a temperature of 22±1 °C and a relative humidity of 60±3%. Using spectrophotometry, the optical characteristics (absorbance and transmittance) of each aligner will be evaluated after aging (Jasco UV-vis V630PC, Tokyo, Japan). Each aligner will be cut with a rotating saw from canine to canine prior to the measurements in order to lop off the lingual region and displaying the labial barrier. The absorbance and transmittance measurements will be collected and statistically analyzed with a significance of P<0.05. Surface roughness of the aligners and attachments inside them will be assessed by 3D scanning microscopy (Infinite Focus G4h). Color of resin composite will be assessed using the (CIE Lab) Commission Internationale de l'Eclairage L*a*b* color space by means of Olympus CrystalEyef dental spectrophotometer. Clinicians should advise patients to refrain from smoking and drinking coffee or tea while wearing aligners for two reasons: first, the color change is unacceptably noticeable when wearing aligners, and second, the material's chemical composition may be slightly altered, which could affect the intended dental movements.

Overcoming the congenitally disadvantageous mutation through adaptation to environmental UV exposure in land snails.

Congenital fitness-disadvantageous mutations are not maintained in the population; they are purged from the population through processes such as purifying selection. However, these mutations could persist in the population as polymorphisms when it is advantageous for the individuals carrying them in adapting to a specific external environment. We tested this hypothesis using the dimorphic land snail Euhadra peliomphala simodae in Japan; these snails have dark or bright coloured shells. The survival rate of dark snails at hatching was lower than that of the bright ones, as observed in the F1 progenies produced through crossing. Dark snails have a congenital fitness-disadvantageous mutation; however, they also have protection against ultraviolet radiation. They have a higher survival rate than the bright snails in a UV environment, as observed using the UV exposure experiments and UV transmittance measurements. This is a good example of a congenitally disadvantageous mutation that is advantageous for adapting to the external environment. These results explain the maintenance of polymorphism and highlight the genotypic and phenotypic diversity in the wild population.