ABSTRACT
Almost all animal eyes follow a few, relatively well-understood functional plans. Only rarely do researchers discover an eye that diverges fundamentally from known types. The principal eye E2 of sunburst diving beetle (Thermonectus marmoratus) larvae clearly falls into the rarer category. On the basis of two different tests, we here report that it has truly bifocal lenses, something that has been previously suggested only for certain trilobites. Our evidence comes from (1) the relative contrast in images of a square wave grating and (2) the refraction of a narrow laser beam projected through the lens. T. marmoratus larvae have two retinas at different depths behind the lens, and these are situated so that each can receive its own focused image. This is consistent with a novel eye organization that possibly comprises "two eyes in one." Moreover, we find that in contrast to most commercial bifocal lenses, the lens of E2 exhibits asymmetry, which results in separation of the images both dorsoventrally and rostrocaudally within the layered retina. Visual contrast might thus be improved over conventional bifocal lenses because the unfocused version of one image is shifted away from the focused version of the other, an organization which could potentially be exploited in optical engineering.
Subject(s)
Coleoptera/physiology , Lens, Crystalline/physiology , Vision, Ocular/physiology , Animals , Coleoptera/anatomy & histology , Coleoptera/growth & development , Larva/anatomy & histology , Larva/physiology , Retina/anatomy & histologyABSTRACT
We report on the temperature dependent spectroscopic properties of Yb(3+) and Er(3+) co-doped glass gain media in the eye-safe spectral region. Measurements suggest that judicious selection of the operating wavelength can lead to a laser output with minimal dependence on the temperature of the gain medium.
ABSTRACT
Dramatic spectral narrowing of two normally broadband lasers, Ti:sapphire and Cr:LiSAF, was achieved by simply replacing the output mirror with a reflective, volumetric Bragg grating recorded in photothermal refractive glass. The output power of each laser was unchanged from that obtained using dielectric coated output mirrors with the same output coupling as the Bragg grating while spectral brightness increased by 3 orders of magnitude.
ABSTRACT
The properties of Yb, Tm:KY3F1o, a cubic fluoride crystal, are described that make it attractive as the blue emitter in two-dimensional photonic displays. Its peak excitation wavelength for blue upconversion emission is 974.7 nm, where efficient diode laser pump sources are available. The maximum upconversion efficiency measured thus far is 4.4%.
ABSTRACT
Pump pulse duration is shown to determine the maximum efficiency of the up conversion process in ytterbium, thulium co-doped fluoride crystals through its role in determining the emitter temperature reached. We show that up-conversion efficiencies should only be measured when using the same pumping conditions as would be used in a proposed application and that thermal management of the up converting material is critical to optimized performance.
ABSTRACT
We report on the distribution of fluorescence that can be emitted through the surfaces of a ytterbium-doped yttrium aluminum garnet (Yb:YAG) slab-shaped high-power solid-state laser. Slab shapes considered include parallel or antiparallel Brewster endfaced slabs and rectangular parallelepiped slabs. We treat cases in which all the faces of these slabs are in air, or with water or another coating on the largest faces. The fraction of the fluorescence emitted through each face, its distribution over that face, and the directions in which it travels are shown to be important to the design of high-power slab lasers.
ABSTRACT
A linear temperature dependence between -70 degrees C and +70 degrees C is reported for the peak stimulated emission cross section of Nd3+ ions in both yttrium aluminum garnet (YAG) and gadolinium scandium gallium garnet (GSGG).
