Photoelastic plasmonic metasurfaces with ultra-large near infrared spectral tuning

Metasurfaces, consisting of artificially fabricated sub-wavelength meta-atoms with pre-designable electromagnetic properties, provide novel opportunities to a variety of applications such as light detectors/sensors, local field imaging and optical displays. Currently,...

Optimising metameric spectra for integrative lighting to modulate the circadian system without affecting visual appearance

Smart integrative lighting systems aim to support human health and wellbeing by capitalising on the light-induced effects on circadian rhythms, sleep, and cognitive functions, while optimising the light’s visual aspects like colour fidelity, visual comfort, visual preference, and visibility. Metameric spectral tuning could be an instrument to solve potential conflicts between the visual preferences of users with respect to illuminance and chromaticity and the circadian consequences of the light exposure, as metamers can selectively modulate melanopsin-based photoreception without affecting visual properties such as chromaticity or illuminance. This work uses a 6-, 8- and 11-channel LED luminaire with fixed illuminance of 250 lx to systematically investigate the metameric tuning range in melanopic equivalent daylight illuminance (EDI) and melanopic daylight efficacy ratio (melanopic DER) for 561 chromaticity coordinates as optimisation targets (2700 K to 7443 K ± Duv 0 to 0.048), while applying colour fidelity index Rf criteria from the TM-30-20 Annex E recommendations (i.e. Rf$$\ge$$ ≥ 85, Rf,h1$$\ge$$ ≥ 85). Our results reveal that the melanopic tuning range increases with rising CCT to a maximum tuning range in melanopic DER of 0.24 (CCT: 6702 K, Duv: 0.003), 0.29 (CCT: 7443 K, Duv: 0) and 0.30 (CCT: 6702, Duv: 0.006), depending on the luminaire’s channel number of 6, 8 or 11, respectively. This allows to vary the melanopic EDI from 212.5–227.5 lx up to 275–300 lx without changes in the photopic illuminance (250 lx) or chromaticity ($$\Delta u'v'$$ Δ u ′ v ′ $$\le$$ ≤ 0.0014). The highest metameric melanopic Michelson contrast for the 6-, 8- and 11-channel luminaire is 0.16, 0.18 and 0.18, which is accomplished at a CCT of 3017 K (Duv: − 0.018), 3456 K (Duv: 0.009) and 3456 K (Duv: 0.009), respectively. By optimising ~ 490,000 multi-channel LED spectra, we identified chromaticity regions in the CIExy colour space that are of particular interest to control the melanopic efficacy with metameric spectral tuning.

Functional divergence and spectral tuning of microbial rhodopsins from an ancestral proton pump

For billions of years, life has continuously adapted to dynamic physical conditions near the Earth s surface. Fossils and other preserved biosignatures in the paleontological record are the most direct evidence for reconstructing the broad historical contours of this adaptive interplay. However, biosignatures dating to Earth s earliest history are exceedingly rare. Here, we combine phylogenetic inference of primordial rhodopsin proteins with modeled spectral features of the Precambrian Earth environment to reconstruct the paleobiological history of this essential family of photoactive transmembrane proteins. Our results suggest that ancestral microbial rhodopsins likely acted as light-driven proton pumps, and were spectrally tuned toward the absorption of green light, which would have enabled their hosts to occupy depths in a water column or biofilm where UV wavelengths were attenuated. Subsequent diversification of rhodopsin functions and peak absorption frequencies track the diversification of surface ecological niches induced by the accumulation of atmospheric oxygen. Inferred ancestors retain distinct associations between extant functions and peak absorption frequencies. Our findings suggest that novel information encoded by biomolecules can be used as paleosensors for conditions of ancient, inhabited niches of host organisms not represented elsewhere in the paleontological record. The coupling of functional diversification and spectral tuning of this pervasive protein family underscores the utility of rhodopsins as universal testbeds for inferring remotely detectable biosignatures on inhabited planetary bodies.

Whale shark rhodopsin adapted to its vertically wide-ranging lifestyle

Spectral tuning of visual pigments often facilitates adaptation to new environments, and it is intriguing to study the visual ecology of pelagic sharks with expanded habitats. The whale shark, which dives into the deep sea of nearly 2,000 meters besides near-surface filter-feeding, was previously shown to possesses the "blue-shifted" rhodopsin (RHO). In this study, our spectroscopy of recombinant whale shark RHO mutants revealed the dominant effect of the novel spectral tuning amino acid site 94, which is implicated in congenital stationary night blindness of humans, accounting for the blue shift. Thermal decay profiling revealed the reduction of the thermal stability of whale shark RHO, as typically observed for cone opsins, which was experimentally shown to be achieved by the site 178, as well as 94. The results suggest that these two sites cooperatively enhance the visual capacity in both the deep sea and the sea surface, enabling exceptionally wide vertical migration of this species.

Spectral Tuning In Quantum Rings By Magnetic Field: Detection From NIR To FIR Regime

In this work, we present a quantum ring structure based on semiconducting QWs for spectral tuning in a wide IR range (1.24- 103 µm) using an external magnetic field. We have used a tight binding method to investigate the optical properties of the structure. Using this method the effect of the external magnetic field on the absorption spectrum has been investigated as the post-processing method. Also, the effect of different geometrical parameters like the number of QWs, QR radius, and constructed material considered as processing methods for tuning absorption. The results show for GaAs based QR with the radius of 100/π consist of 4 QWs, absorption peak linearly increase from 100 meV (12.4 um) in LWIR regime and shift to 200 meV (6.2 um) in MIR regime with increasing external magnetic field. Also for a QR with a radius of 200/π, by changing the magnetic field different absorption peaks appear and disappear in an absorption spectrum and a multi-color detector converts to single-detector in the NIR regime. This results help experimentalist to select proper materials with optimized geometrical parameters to achieve desired wavelength for various detection applications.