Filtering Wavelengths Research Articles

Blue Light Filtration in Intraocular Lenses: Effects on Visual Function and Systemic Health.

Blue light-filtering (BLF) intraocular lenses (IOLs) are designed to mimic the healthy natural adult crystalline lens. Studies that evaluated the relative merit of ultraviolet-only IOL design (ie, blocking wavelengths <400 nm) versus BLF IOL design (ie, filtering wavelengths ~400-475 nm in addition to blocking wavelengths <400 nm) on protection and function of the visual system suggest that neither design had a deleterious impact on visual acuity or contrast sensitivity. A BLF design may reduce some aspects of glare, such as veiling and photostress. BLF has been shown in many contexts to improve visual performance under conditions that are stressed by blue light, such as distance vision impaired by short-wave dominant haze. Furthermore, some data (mostly inferential) support the notion that BLF IOLs reduce actinic stress. Biomimetic BLF IOLs represent a conservative approach to IOL design that provides no harm for visual acuity, contrast sensitivity, or color vision while improving vision under certain circumstances (eg, glare).

Estimating FRET Efficiency using Excitation-Scanning Hyperspectral Imaging

Forster Resonance Energy Transfer, or FRET, is an indispensable tool in the biological sciences for measuring intermolecular distances. Current tools that measure FRET suffer from limited signal strength, making it difficult to observe rapid cell-signaling events. We have developed a unique mode of hyperspectral imaging which filters the excitation wavelengths and collects total fluorescence emission. Our prior work has shown that excitation-scanning is an effective tool for detecting fluorophores in cell samples. The purpose of this study was to assess the feasibility of using this excitation-based technique for FRET measurements. In traditional spectral imaging FRET studies, the emission spectra of donor and acceptor are resolved from the emission spectrum of the sample using linear unmixing However, since excitation scanning collects the entire sample emission without filtering wavelengths, a new approach is needed to utilize our method. Here we present data indicating that excitation scanning can be successfully adapted for FRET studies. Fluorescence excitation-scanning hyperspectral images were acquired by sequentially exciting samples with an 18-20 nm bandwidth (FWHM) tunable excitation source, provided by a 300W Xe arc lamp coupled to a Sutter VF-5 tunable filter. Images were acquired from 380-490nm in 5nm increments. Donor and acceptor excitation signatures were then separated from the total signal using a spectral library. Two long-pass dichroic filters were employed, at 458nm and 495nm. FRET efficiencies were estimated by comparing donor excitation signal between scans with different dichroic filters. Results indicate that excitation-scanning techniques provided accurate estimates of FRET efficiency, and that this method could be a useful tool in FRET-based cell signaling studies. This work was supported by NIH grants P01HL066299, S10RR027535, and the Abraham Mitchell Cancer Research Fund.

Effects of Photon Energy Spectrum on the Photocurrent of Hydrogenated Amorphous Silicon Thin Film Transistor by Using Frequency Filters

Frequency filters with various filtering wavelengths were used in the photoelectric characterization of hydrogenated amorphous silicon thin film transistor (a-Si:H TFT) and the experimental results were described and analyzed in terms of the photon energy spectral characteristics calculated from the integration of the photon energy and the spectral intensity of transmitted backlight through the filters at each wavelength. From the comparison of the photocurrents and the calculated photon energy spectrums for the filtered ranges of wavelength, it was possible to conclude that the photocurrents are closely related to the photon energy spectrums of the backlight.

Spectral modulation attenuates molecular, endocrine, and neurobehavioral disruption induced by nocturnal light exposure

The human eye serves distinctly dual roles in image forming (IF) and non-image-forming (NIF) responses when exposed to light. Whereas IF responses mediate vision, the NIF responses affect various molecular, neuroendocrine, and neurobehavioral variables. NIF responses can have acute and circadian phase-shifting effects on physiological variables. Both the acute and phase-shifting effects induced by photic stimuli demonstrate short-wavelength sensitivity peaking ≈450-480 nm. In the current study, we examined the molecular, neuroendocrine, and neurobehavioral effects of completely filtering (0% transmission) all short wavelengths <480 nm and all short wavelengths <460 nm or partially filtering (~30% transmission) <480 nm from polychromatic white light exposure between 2000 and 0800 in healthy individuals. Filtering short wavelengths <480 nm prevented nocturnal light-induced suppression of melatonin secretion, increased cortisol secretion, and disrupted peripheral clock gene expression. Furthermore, subjective alertness, mood, and errors on an objective vigilance task were significantly less impaired at 0800 by filtering wavelengths <480 nm compared with unfiltered nocturnal light exposure. These changes were not associated with significantly increased sleepiness or fatigue compared with unfiltered light exposure. The changes in molecular, endocrine, and neurobehavioral processes were not significantly improved by completely filtering <460 nm or partially filtering <480 nm compared with unfiltered nocturnal light exposure. Repeated light-dark cycle alterations as in rotating nightshifts can disrupt circadian rhythms and induce health disorders. The current data suggest that spectral modulation may provide an effective method of regulating the effects of light on physiological processes.

Female mating preferences, lighting environment, and a test of the sensory bias hypothesis in the bluefin killifish

Sensory drive proposes that environmental conditions affect signalling dynamics and the evolution of signals and receivers. For visual systems, delineating the effects of lighting on mating preferences is difficult because lighting conditions can affect preferences via three mechanisms: (1) genetic differentiation in mating preferences can result from selection under different lighting conditions, (2) development under different lighting conditions can alter the visual system and presumably female mating preferences and (3) lighting conditions can immediately alter colour perception by filtering wavelengths and altering visual backgrounds. We teased apart these effects by crossing bluefin killifish within and between a spring population and a swamp population that differed in lighting environment. We divided offspring between clear and tea-stained rearing environments (developmental plasticity) and measured preference under tea and clear conditions (immediate effects). We found genetic differentiation: spring offspring showed a strong preference for red males. We also found a three-way interaction between genetics, developmental plasticity and immediate effects on preference for blue males: swamp offspring had the highest levels of preference for blue males when raised and tested under tea-stained conditions. Thus, the environment experienced during development and the immediate conditions during mate selection interact with genetics to determine preference. We also tested the sensory bias hypothesis, which predicts that mating preferences evolve as a correlated response to selection on nonmating behaviours such as foraging. The relationship between mating and foraging preferences was weak and provided little support for sensory bias.

Optical filters based in quasiperiodic photonic crystal

In this work we investigate theoretically the behavior of a light beam incident on a χ(2) nonlinear quasiperiodic photonic crystal (or quasiperiodic S˘olc filter), in which each building block containing a pair LiNbO3 layers with antiparallel poled domains, arranged in a quasiperiodical fashion which follows the Pell, Fibonacci, Thue–Morse, and double-period substitutional sequences. The transmittances at filtering wavelengths can be modulated from 0 to 1 by applying an external voltage but the filtering wavelengths are unchanged. We show that the filtering wavelengths tuned by varying voltage around 0.9kV, indicate that quasiperiodic S˘olc filter based in Pell and Thue–Morse sequences are so efficient as the Fibonacci S˘olc filter, while the double-period sequence have a low efficiency.

Electro- and thermo-optic effects on multi-wavelength Šolc filters based on χ^(2) nonlinear quasi-periodic photonic crystals

We investigate electro- and thermo-optic effects on multi-wavelength Solc filters based on chi(2) nonlinear quasi-periodic photonic crystals. The multi-wavelength Solc filters are composed of two building blocks A and B, in which each containing a pair of antiparallel poled domains, arranged as a Fibonacci sequence. The transmittances at filtering wavelengths can be modulated from 0 to 100% by applying an external voltage but the filtering wave-lengths are unchanged. The filtering wavelengths can be tuned by varying temperature. As temperature decreases, the filtering wavelengths increase (approximately -0.45 nm/degrees C).

Multiwavelength Sŏlc filters based on χ(2) nonlinear quasiperiodic photonic crystals with Fibonacci sequences

We demonstrate that a χ(2) nonlinear quasiperiodic photonic crystal can act as a multiwavelength Sŏlc filter. The χ(2) nonlinear quasiperiodic photonic crystal consists of two building blocks A and B, in which each containing a pair of antiparallel poled domains, arranged as a Fibonacci sequence. The filtering wavelengths are analyzed with the Fibonacci sequence parameters such as the quasiperiodic indices and the average lattice parameter. The filtering efficiency can be tuned by the lengths of poled domains.

Cube add/drop optical filter with low polarisation sensitivity using a metal island multilayer filter

An add/drop cube optical filter consisting of a metal island multilayer filter (IMF) sandwiched between two 45° glass prisms is proposed for wavelength division multiplexing applications. The light in a purposive wavelength region is reflected in a direction perpendicular to the incident light beam while other wavelengths are transmitted in a parallel direction. Filtering wavelengths, bandwidths, and device thicknesses can be controlled by the choice of structural parameters for the metal island films and the thickness of the glass layers. An IMF cube filter for 800 nm is designed. It is theoretically shown that the IMF cube filter is insensitive to polarisation in comparison with a conventional dielectric multilayer filter.