All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators

We review our recent work on tunable, ultrahigh quality factor whispering-gallery-mode bottle microresonators and highlight their applications in nonlinear optics and in quantum optics experiments. Our resonators combine ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume, and near-lossless fiber coupling, with a simple and customizable mode structure enabling full tunability. We study, theoretically and experimentally, nonlinear all-optical switching via the Kerr effect when the resonator is operated in an add-drop configuration. This allows us to optically route a single-wavelength cw optical signal between two fiber ports with high efficiency. Finally, we report on progress towards strong coupling of single rubidium atoms to an ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B. Changes according to referee suggestions: minor corrections to some figures and captions, clarification of some points in the text, added references, added new paragraph with results on atom-resonator interactio

Establishing a scale of directional-hemispherical reflectance factor I: The Van den Akker method

A thorough study and error analysis was made of the Van den Akker or “auxiliary sphere” method of determining a scale of directional-hemispherical reflectance factor. The effects of a non-Lambertian distribution of the reflected radiation, including retroreflection, were included in this study. Three working standards were measured to an uncertainty in reflectance of less than ±0.0015 and these will be used as a basis for a new, more accurate NBS scale of 6°-hemispherical reflectance factor. The new scale and the NBS scale established in 1965 are in agreement to within the uncertainty of ±0.005 assigned to the 1965 scale

Substituição do feno de coastcross por casca de soja na alimentação de cabras em lactação Replacement of coastcross hay by soybean hulls in diets for lactating goats

Objetivou-se com este trabalho verificar a resposta de cabras em lactação alimentadas com dietas contendo casca de soja em substituição ao feno de coastcross. Trinta e seis cabras (38±5 dias em lactação; 2,1±0,4 kg/dia) foram distribuídas em delineamento experimental de blocos completos casualizados e confinadas por oito semanas. As dietas foram compostas de 50% de volumoso e 50% de concentrado e com o mesmo teor de fibra em detergente neutro. A casca de soja substituiu o feno de coastcross em 0, 33, 67 ou 100% da matéria seca (MS). O consumo de matéria seca e a eficiência alimentar apresentaram resposta quadrática aos teores de casca de soja na dieta. A produção de leite e a variação do peso corporal não foram alteradas, porém a concentração de gordura e lactose do leite aumentou e os tempos gastos com ruminação e mastigação decresceram com a inclusão da casca de soja na dieta. A casca de soja pode substituir totalmente o feno de coastcross em dietas para cabras em lactação, pois essa substituição não prejudica a produção de leite e aumenta o teor de gordura e lactose do leite. Em comparação ao feno picado de coastcross, a casca de soja apresenta menor efetividade em estimular a ruminação e a mastigação.<br>The objective of this experiment was to verify the response of lactating goats fed diets with different levels (content) of soybean hulls replacing coastcross hay (Cynodon sp.) on performance. Thirty-six lactating Saanen goats (38±5 days of lactation; 2.1±0.4 kg/day) were assigned to a randomized complete blocks design and housed for 8 weeks. Goats were fed diets of 50% roughage and 50% concentrate, but with the same amount of neutral detergent fiber. Soybean hulls replaced hay by 0, 33, 67 or 100% of the dry matter (DM). Dry matter and NDF intake and feed efficiency showed a quadratic response to the levels of soybean hulls in the diet. Milk yield and body weight variations did not change; however, milk fat, lactose and total solids concentration increased while time spent with rumination and chewing decreased, when soybean hulls were added to the diet. Soybean hulls can replace entirely coastcross hay in diets for lactating goats, with no detrimental effect on milk yield or with an increase on milk fat and lactose concentration. Compared with chopped coastcross hay, soybean hulls show less effectiveness to stimulate rumination and chewing