Spectral broadening and shaping of nanosecond pulses: towards shaping of single photons from quantum emitters

We experimentally demonstrate spectral broadening and shaping of exponentially-decaying nanosecond pulses via nonlinear mixing with a phase-modulated pump in a periodically-poled lithium niobate (PPLN) waveguide. A strong, 1550~nm pulse is imprinted with a temporal phase and used to upconvert a weak 980 nm pulse to 600 nm while simultaneously broadening the spectrum to that of a Lorentzian pulse up to 10 times shorter. While the current experimental demonstration is for spectral shaping, we also provide a numerical study showing the feasibility of subsequent spectral phase correction to achieve temporal compression and re-shaping of a 1~ns mono-exponentially decaying pulse to a 250 ps Lorentzian, which would constitute a complete spectro-temporal waveform shaping protocol. This method, which uses quantum frequency conversion in PPLN with >100:1 signal-to-noise ratio, is compatible with single photon states of light.Comment: 4 pages, 4 figure

Production and Persistence of Self-Regenerating Annual Clovers in the Pacific Northwest

Self-regenerating annual legumes are commonly included in dryland pastures to increase the production of high-quality forages to meet the nutritional demands of growing and lactating animals. Balansa clover (Trifolium michelianum Savi), not as widely evaluated as subterranean clover (Trifolium subterraneum L.), has shown promise in Western Oregon. However, there is a paucity of information on the productivity and persistence of annual clover cultivars that have various flowering times. This study investigates the biomass production and persistence of early, mid and late flowering subterranean clover and balansa clover cultivars in Corvallis, Oregon. Averaged across the cultivars, the total annual dry matter yield (DMY) of subterranean clover was greater than balansa clover by 15% (3085 vs. 3612 kg DM ha-1) in the 2021/2022 growing season. Mintaro was the highest yielding subterranean clover cultivar with over 4465 kg DM ha-1 annual DMY. The biomass production of Campeda, Antas and Denmark was comparable to Mintaro. In contrast, the early flowering cultivar, Dalkeith was the lowest producing subterranean clover cultivar with less than 1500 kg DM ha-1. Herbage yield of balansa clover cultivars Border, Taipan and Viper ranged from 3446 to 3866 kg DM ha-1 and was comparable to the highest yielding subterranean cultivars. However, DMY of balansa clover cultivars Paradana, Fixation and VNS was lower than the other three highest-producing balansa cultivars. In the following fall, mean seedling number of subterranean clover (991 seedling per m2) was substantially greater than balansa clover (78 seedling per m2). Our preliminary findings indicated that mid to late maturing subterranean and balansa clover cultivars are well-suited to the agroecological conditions of the Pacific Northwest but regeneration of balansa clover cultivars was poor possibly due to hardseededness

Bright single photon emission from a quantum dot in a circular Bragg grating microcavity

Bright single photon emission from single quantum dots in suspended circular Bragg grating microcavities is demonstrated. This geometry has been designed to achieve efficient (> 50 %) single photon extraction into a near-Gaussian shaped far-field pattern, modest (~10x) Purcell enhancement of the radiative rate, and a spectral bandwidth of a few nanometers. Measurements of fabricated devices show progress towards these goals, with collection efficiencies as high as ~10% demonstrated with moderate spectral bandwidth and rate enhancement. Photon correlation measurements are performed under above-bandgap excitation (pump wavelength = 780 nm to 820 nm) and confirm the single photon character of the collected emission. While the measured sources are all antibunched and dominantly composed of single photons, the multi-photon probability varies significantly. Devices exhibiting tradeoffs between collection efficiency, Purcell enhancement, and multi-photon probability are explored and the results are interpreted with the help of finite-difference time-domain simulations. Below-bandgap excitation resonant with higher states of the quantum dot and/or cavity (pump wavelength = 860 nm to 900 nm) shows a near-complete suppression of multi-photon events and may circumvent some of the aforementioned tradeoffs.Comment: 11 pages, 12 figure

Multiple time scale blinking in InAs quantum dot single-photon sources

We use photon correlation measurements to study blinking in single, epitaxially-grown self-assembled InAs quantum dots situated in circular Bragg grating and microdisk cavities. The normalized second-order correlation function g(2)(\tau) is studied across eleven orders of magnitude in time, and shows signatures of blinking over timescales ranging from tens of nanoseconds to tens of milliseconds. The g(2)(\tau) data is fit to a multi-level system rate equation model that includes multiple non-radiating (dark) states, from which radiative quantum yields significantly less than 1 are obtained. This behavior is observed even in situations for which a direct histogramming analysis of the emission time-trace data produces inconclusive results

Re-Growth Yield and Nutritive Value of Winter Cereals

Cereal crops can be grazed in early winter or early spring when feed is scarce, or to utilize their high feeding value. In the early spring of 2011, the re-growth yield and nutritive value of barley (Hordeum vulgare L.), rye (Secale cereale L.), wheat (Triticum aestivum), oat (Avena sativa L.), and triticale (x Triticosecale Wittmack) grown in the Central Anatolian Region of Turkey, were evaluated after three successive weekly harvests (Cut 1, Cut 2, Cut 3) during the tillering to stem elongation stages. Plants were cut at a height of 5 cm then allowed to re-grow until when they were harvested again at the dough stage on 18 June. Dry matter (DM) production (kg/ha) and nutritive value of forage were compared to plots that were uncut (No Cut). Re-growth yield (DM t/ha) decreased (P \u3c 0.01) almost linearly with the delay in cutting time for each crop, but at different (P \u3c 0.01) rates. Re-growth was reduced by up to 72% in Cut 3 compared with No Cut. The cell-wall components of plant tissues decreased (P \u3c 0.001) in re-growth after Cut 2 and Cut 3 compared with No Cut. In-vitro DM digestibility was lowest (P \u3c 0.001) in cereals with No Cut at the dough stage. The results suggest that winter cereals can be grazed up to the stem elongation stage without causing large reductions in the overall forage yield. The fodder obtained from material re-grown after the initial grazing may also offer higher-quality feed for livestock than ungrazed crops

Does Producing Forages Improve Livelihoods in Dry Areas? The Case of Afghanistan (On-going Research)

Agriculture is the main livelihood and a major contributor to the Afghan economy. Livestock production contributes with almost 50% of agricultural GDP in Afghanistan where out of 75% Afghans who live in rural areas, 85% keep some livestock (AusAID and ACIAR, 2011). In particular, small ruminants (sheep and goats) provide small holder rural Afghan families with livelihoods, food and capital. However, insufficient feed is a key constraint that limits productivity, income growth and sustainability in the crop-livestock farming (GIRoA, 2009). The purpose of this research was to assess and identify which forage production technologies offers high productivity and resilience to farmers to maintain productive small ruminant flocks

Protection of Historical Heritage From The Point Of Sustainable Environment and The Sample of Caca Bey Madrasa In Kirşehir District

Caca Bey Madrassa in the heart of the city Kırşehir madrassa was situated in the central Anatolia region. That madrassa was built by Turkish scientists from West Turkistan. Caca Bey founded the science center. Built as a madrasa was used as an observatory the building, which has undergone several renovations. Observations were accured in the years 1271-1272 by the house (observatory), but now serves as a mosque. It was known Cıncıklı mosque among the people with the name because of the blue tiles covered. The madrassa built of cut stone was square in shape and was the type of madrassa-domed structure. Caca Bey Madrassa was separated mainly two parts, one was Caca Bey Complex and the other was Caca Bey Tomb. An artful madrassa in Seljuk period was built and decorated with mosaic tiles and with stone portal, with brick and was a high observation tower. This tower was taken back later the minaret of bonds. Caca Bey Tomb, north-east corner of the school building of the madrassa has seven (7) digit stairs. Kırşehir was in the first degree earthquake zone in terms of the potential for producing earthquakes. Kırşehir was formed in first geological time, and was known as "Kırşehir Massif" in the earthquake literature. Movement Speed of Kırşehir fault line was 2 mm in a year. Depending on the strike-slip faults generally occur the earthquakes in this area. This madrassa must be renovated and strengthened bounding original characteristics of madrassa including the earthquake circumstances in that area

Identifying the Qualities of an Ideal Teacher in line with the Opinions of Teacher Candidates

Teaching is a sacred profession performed by self-sacrificing individuals with high responsibilities who are aware of their roles, have undertaken the task of raising future generations, make easier individuals’ process of becoming citizen in a way to ensure the peace and welfare of the communities, and allow them to learn knowledge, skills, attitudes and behaviors. By Ataturk’s saying, "Teachers are the most devoted and respectable factors of human society all over the world". In hadiths, the sanctity of teaching is expressed as, "Only those two people are admired enviously: The person who uses up and consumes the goods bestowed by Allah on him in the right way, and the person who properly rules over by the wisdom to him by Allah and who also teaches it to others.” From early childhood to puberty, the person studying in public institutions establishes a spiritual association with his/her teacher. The psychical aspect of teaching is also quite predominant. The role of teaching is sometimes mixed up with the roles of mother, father, sister and brother. There are many students who keep fresh their relationships with teachers for many years although their education and training activities do not continue. Based on these, the starting point of the study is about which characteristics the teacher must have to become an ideal teacher. This study was carried out to determine the characteristics of an ideal teacher in line with the opinions of the participants of the faculty of education and pedagogical training program in a University in Istanbul. The research was carried out in the screening model. The research data were collected through semi-structured interview technique to find out student opinions in a clearer way. The study group of the research was established in accordance with the voluntary basis from among the students from the psychological counseling and guidance department, Turkish teaching department, gifted children teaching department and English teaching department and the students who are enrolled in the pedagogical training certificate program in a University, in Istanbul, in the 2015-2016 academic year. Face to face interviews were conducted with each participant in the researcher's working office for half an hour on an average. At the beginning of the interview, students were asked about their genders and the graduated university, department and faculty. Within the context of the interview, the question of "what are the characteristics of an ideal teacher for you" was posed to participants. The personal and professional characteristics that an ideal teacher should have were determined according to the opinions of teacher candidates. The discussion section was structured by the research findings in the literature, and the study was finalized with suggestions