Introduction: The pupillary light reflex (PLR) is the constriction of the pupil in response to light. The PLR in response to a pulse of light follows a complex waveform that can be characterized by several parameters. It is a sensitive marker of acute neurological deterioration, but is also sensitive to the background illumination in the environment in which it is measured. To detect a pathological change in the PLR, it is therefore necessary to separate the contributions of neuro-ophthalmic factors from ambient illumination. Illumination varies over several orders of magnitude and is difficult to control due to diurnal, seasonal, and location variations. Methods and results: We assessed the sensitivity of seven PLR parameters to differences in ambient light, using a smartphone-based pupillometer (AI Pupillometer, Solvemed Inc.). Nine subjects underwent 345 measurements in ambient conditions ranging from complete darkness (<5 lx) to bright lighting (â²10,000 lx). Lighting most strongly affected the initial pupil size, constriction amplitude, and velocity. Nonlinear models were fitted to find the correction function that maximally stabilized PLR parameters across different ambient light levels. Next, we demonstrated that the lighting-corrected parameters still discriminated reactive from unreactive pupils. Ten patients underwent PLR testing in an ophthalmology outpatient clinic setting following the administration of tropicamide eye drops, which rendered the pupils unreactive. The parameters corrected for lighting were combined as predictors in a machine learning model to produce a scalar value, the Pupil Reactivity (PuRe) score, which quantifies Pupil Reactivity on a scale 0-5 (0, non-reactive pupil; 0-3, abnormal/"sluggish" response; 3-5, normal/brisk response). The score discriminated unreactive pupils with 100% accuracy and was stable under changes in ambient illumination across four orders of magnitude. Discussion: This is the first time that a correction method has been proposed to effectively mitigate the confounding influence of ambient light on PLR measurements, which could improve the reliability of pupillometric parameters both in pre-hospital and inpatient care settings. In particular, the PuRe score offers a robust measure of Pupil Reactivity directly applicable to clinical practice. Importantly, the formulae behind the score are openly available for the benefit of the clinical research community.
In light science and applications, equally important roles are played by efficient light emitters/detectors and by the optical elements responsible for light extraction and delivery. The latter should be simple, cost effective, broadband, versatile and compatible with other components of widely desired micro-optical systems. Ideally, they should also operate without high-numerical-aperture optics. Here, we demonstrate that all these requirements can be met with elliptical microlenses 3D printed on top of light emitters. Importantly, the microlenses we propose readily form the collected light into an ultra-low divergence beam (half-angle divergence below 1°) perfectly suited for ultra-long-working-distance optical measurements (600 mm with a 1-inch collection lens), which are not accessible to date with other spectroscopic techniques. Our microlenses can be fabricated on a wide variety of samples, including semiconductor quantum dots and fragile van der Waals heterostructures made of novel two-dimensional materials, such as monolayer and few-layer transition metal dichalcogenides.
Monolayer transition-metal dichalcogenides (TMDs) manifest exceptional optical properties related to narrow excitonic resonances. However, these properties have been so far explored only for structures produced by techniques inducing considerable large-scale inhomogeneity. In contrast, techniques which are essentially free from this disadvantage, such as molecular beam epitaxy (MBE), have to date yielded only structures characterized by considerable spectral broadening, which hinders most of the interesting optical effects. Here, we report for the first time on the MBE-grown TMD exhibiting narrow and resolved spectral lines of neutral and charged exciton. Moreover, our material exhibits unprecedented high homogeneity of optical properties, with variation of the exciton energy as small as ±0.16 meV over a distance of tens of micrometers. Our recipe for MBE growth is presented for MoSe2 and includes the use of atomically flat hexagonal boron nitride substrate. This recipe opens a possibility of producing TMD heterostructures with optical quality, dimensions, and homogeneity required for optoelectronic applications.
Prototyping of fiber-coupled integrated photonic devices requires robust and reliable way of docking optical fibers to other structures, often with sub-micron accuracy. We have developed an optical fiber micro-connector 3D-printed with Direct Laser Writing on a planar substrate. The connector provides fiber core precision positioning better than 120 nm and sustains cryogenic cycling without any signs of degradation. It can be fabricated and used on glass and non-transparent substrates, including photonic integrated circuits, semiconductor samples, and microfluidic systems.
