Stochastic light concentration from 3D to 2D reveals ultraweak chemi- and bioluminescence

For countless applications in science and technology, light must be concentrated, and concentration is classically achieved with reflective and refractive elements. However, there is so far no efficient way, with a 2D detector, to detect photons produced inside an extended volume with a broad or isotropic angular distribution. Here, with theory and experiment, we propose to stochastically transform and concentrate a volume into a smaller surface, using a high-albedo Ulbricht cavity and a small exit orifice through cavity walls. A 3D gas of photons produced inside the cavity is transformed with a 50% number efficiency into a 2D Lambertian emitting orifice with maximal radiance and a much smaller size. With high-albedo quartz-powder cavity walls ($$\rho =99.94\%$$ ρ = 99.94 % ), the orifice area is $$1/(1-\rho )\approx 1600$$ 1 / ( 1 - ρ ) ≈ 1600 times smaller than the walls’ area. When coupled to a detectivity-optimized photon-counter ($$\mathcal{D}=0.015\,{\text{photon}}^{-1}\,{\text{s}}^{1/2}\text{ cm}$$ D = 0.015 photon - 1 s 1 / 2 cm ) the detection limit is $$110\;{\text{photon}}\;{\text{s}}^{ - 1} \;{\text{L}}^{ - 1}$$ 110 photon s - 1 L - 1 . Thanks to this unprecedented sensitivity, we could detect the luminescence produced by the non-catalytic disproportionation of hydrogen peroxide in pure water, which has not been observed so far. We could also detect the ultraweak bioluminescence produced by yeast cells at the onset of their growth. Our work opens new perspectives for studying ultraweak luminescence, and the concept of stochastic 3D/2D conjugation should help design novel light detection methods for large samples or diluted emitters.

Ultraweak luminescence from germinating resting spores of Entomophthora virulenta Hall et Dunn

Germinating resting spores of <i>Entomophthora virulenta</i> Hall et Dunn emit ultraweak luminescence with the intensity of the order 100 photons • s^-1 • cm^-2 in the spectral region 200-750 nm. The emission kinetics and intensity depend on vitality and incubation temperature of the spores. The higher the ability of resting spores to germinate, the more intense the luminescence. Elevation of the incubation temperature to 50°C enhances ultraweak luminescence. The activation energy was found to be about 15 kJ • mol^-1 and 5 kJ • mol^-1 for nongerminating and germinating in 50% spores, respectively. The possibility of applying ultraweak luminescence as a simple assay for the spores vitality is discussed.

Oscillatory character of changes in ultraweak luminescence from Nitella cells

Characteristics of changes in ultraweak luminescence of <em>Nitella</em> internodal cells under physiological conditions and after exposure to the action of biologically active substances are determined. The results presented here supplement the picture of oscillatory behaviour of <em>Nitella</em> cells worked out by us regarding changes in the electrical and transport properties.