Novel Devices and Components Polarization-preserving teflon photonic crystal fiber waveguide for THz radiation

Abstract Using a highly flexible plastic material, Teflon, photonic crystal fiher (PCF) waveguide for THz radiation is constructed. It is found that such PCF possesses strongly polarizationpreserving property. With such feature, coupled with relatively low-loss coefficient, the possibility of preparing long PCF waveguide in the THZ region can be easily attained. Introduction The terahertz (THz) region that lies between the electronic and optical region in the electromagnetic spectrum, wit

All-solid-state tunable ultraviolet subnanosecond laser with direct pumping by the fifth harmonic of a Nd:YAG laser

We report what we believe is the first all-solid-state tunable ultraviolet laser pumped by the fifth harmonic of a Q-switched Nd:YAG laser. Our laser based on a Ce3+:LiLuF4 active medium stably generates a single, satellite-free, 0.88-ns pulse under 5-ns, 10-Hz repetition rate pumping conditions. A novel tilted-incident-angle side-pumping scheme resulted in a simple laser-cavity design. © 1998 Optical Society of America

Generation of ultra-short light pulses by a rapidly ionizing thin foil

A thin and dense plasma layer is created when a sufficiently strong laser pulse impinges on a solid target. The nonlinearity introduced by the time-dependent electron density leads to the generation of harmonics. The pulse duration of the harmonic radiation is related to the risetime of the electron density and thus can be affected by the shape of the incident pulse and its peak field strength. Results are presented from numerical particle-in-cell-simulations of an intense laser pulse interacting with a thin foil target. An analytical model which shows how the harmonics are created is introduced. The proposed scheme might be a promising way towards the generation of attosecond pulses. PACS number(s): 52.40.Nk, 52.50.Jm, 52.65.RrComment: Second Revised Version, 13 pages (REVTeX), 3 figures in ps-format, submitted for publication to Physical Review E, WWW: http://www.physik.tu-darmstadt.de/tqe

All-solid-state subnanosecond tunable ultraviolet laser sources based on Ce3+-activated fluoride crystals

Several practical all-solid-state tunable ultraviolet subnanosecond laser sources have been developed based on Ce3+:LiLuF4 (Ce:LLF) and Ce3+:LiCaAlF6 (Ce:LiCAF) active media pumped by the fifth and fourth harmonics of a regular Q-switched 10-ns Nd:YAG laser, respectively. The demonstrated tuning range of the Ce:LiCAF oscillator providing reproducibly-single-pulse output was 282 nm to 314 nm with the maximum output energy of 1 mJ. Tunable laser output from 223 nm to 232 nm was obtained by sum-frequency-mixing Ce:LiCAF laser output with fundamental output of a Q-sw Nd:YAG laser. The maximum subnanosecond Ce:LiCAF single-pulse output of 14 mJ was obtained in a "master oscillator-power amplifier" (MOPA) configuration

Ultrashort Pulse Generation in Ce:LiCAF Ultraviolet Laser

Transient cavity method used to generate ultrashort laser pulses in dye lasers is extended to a solid-state gain medium. Numerical simulations are performed to investigate the spectro-temporal evolution of broadband ultraviolet (UV) laser emission from Ce3+-doped LiCaAlF6 (Ce:LiCAF), which is represented as a system of two homogeneous broadened singlet states. By solving the rate equations extended to multiple wavelengths, the appropriate cavity length and Q-factor for optimal photon cavity decay time and pumping energy that will generate resonator transients is determined. Formation of resonator transients could generate picosecond UV laser pulses from a Ce:LiCAF crystal pumped by the fourth harmonics (266 nm) of a Nd:YAG laser. Numerical simulations indicate that a 1-mol% Ce3+-doped LiCAF crystal that is 1-mm long can generate a single picosecond pulse. This is accomplished by using a low Q (output coupler reflectivity of 10%), short cavity (cavity length of 2 mm) laser oscillator. Ultrashort pulses can also be generated using other rare earth-doped fluoride laser materials using this technique

Dietary zinc intake and its effects on zinc nutrition in healthy Japanese living in the central area of Japan

In the present study, we first examined the dietary zinc intake from food groups in 109 healthy Japanese (24-82 years old, 45 male and 64 female) by means of the 72-h recall method. We then used the ratio of apo/holo-activities of angiotensin converting enzyme (ACE ratio) that is a more sensitive index of zinc nutrition than zinc concentration in the serum and examined the correlation between their zinc intake and ACE ratio. Dietary zinc intake in healthy Japanese was maximal from rice and rice products. There were significant inverse correlations between the ACE ratio and dietary zinc intake from rice and rice products and shellfish, and a significant positive correlation between ACE ratio and dietary zinc intake from other beans and bean processed foods. On the other hand, there were no significant correlations between serum zinc concentrations and dietary zinc intake from any food group except processed fish. These findings suggested that rice is a major source of dietary zinc intake in healthy Japanese. It is also suggested that shellfish also has a major impact on zinc nutrition, although dietary zinc intake from this source is minimal. Since beans contain phytic acid, which inhibits the absorption of dietary zinc, it is suggested that intake of beans causes impairment of zinc nutrition

Direct and passive subnanosecond pulse-train generation from a self-injection-seeded ultraviolet solid-state laser

We propose a passive self-injection-seeding scheme for the generation of short-pulse trains from various pulsed lasers. In this scheme a single subnanosecond pulse is generated from a short-cavity seeding laser. The pulse is then returned to the same gain medium and amplified regeneratively until the gain is quenched completely. Cw operation capability or an external short-pulse seeding laser is not required for generation of short-pulse trains. Based on this simple scheme an ultraviolet subnanosecond pulse train is directly and passively generated from a solid-state laser medium (Ce3+:LuLiF 4) pumped by a standard 10-ns laser. © 1995 Optical Society of America

Study on the necessary survey days for energy intake in school children assessed by 7 day survey

Theoretically, the longer the period of a nutrition survey, the more reliable the results. However, a long survey can impose a burden on subjects and cause the results to become inaccurate. For adults, a 3 non-consecutive day survey is usually recommended ; however, for school children, at least in Japan, it has not been determined whether this is necessary. In this study we conducted a survey of 7 days and tried to find the minimum number of days necessary to determine the energy intake. The subjects were about 300 children aged from 6 to 7, 10 to 11 and 13 to 14 years old in a city in the western part of Japan. The weighing method was used for the school lunch and other meals were surveyed by 24-recalling method. For the 6-7 year-old school children, guardians were asked to keep dietary records. The final number of subjects who were able to complete the 7-day survey was 139. Energy intakes for each weekday were not statistically different (p>0.05) and those for each weekend did not differ (p>0.05). Average energy intakes on weekdays were higher than those on weekend days in 10-11 and 13-14 year-old children. The average intakes of energy in 10-11 and 13-14 year-old children were lower than Japanese estimated energy requirements (EER). However, body weight of more than 90% of subjects was within the normal range. The results suggest that a survey of one weekday is reliable for all weekdays and that of one week-end day is reliable for any weekend day and also indicate the necessity of further studies of EER in rapidly growing children