Optical imaging of multimode interference patterns with a resolution below the diffraction limit

For the first time the optical interference pattern in multimode interference couplers operating at 1485 nm is made visible using an optical microscope. This is done by imaging the green light (519 and 545 nm) which is generated by upconversion at high pumping power levels in waveguides with a high erbium concentration. As the intensity of the green light is roughly proportional to the fourth power of the pump signal intensity it thus becomes possible to image the 1485 nm intensity distribution with a resolution limited by the diffraction limit for 519 and 545 nm ligh

Upconversion in Er-implanted Al2O3 waveguides

When pumped with a 1.48 mu m laser diode, Er-implanted Al/sub 2/O/sub 3/ ridge waveguides emit a broad spectrum consisting of several distinct peaks having wavelengths ranging from the midinfrared (1.53 mu m) to the visible (520 nm). In order to explain these observations, three different upconversion mechanisms are considered: cooperative upconversion, excited state absorption, and pair-induced quenching. It is found that for samples with a high Er concentration (1.4 at.%), cooperative upconversion completely dominates the deexcitation of the Er/sup 3+/ ions. For a much lower concentration (0.12 at.%), the influence of cooperative upconversion is strongly reduced, and another upconversion effect becomes apparent: excited state absorption. These conclusions are based on measurements of the luminescence emission versus pump intensity, and also on measured luminescence decay curves. The upconversion coefficient is found to be (4+or-1)*10/sup -18/ cm/sup 3//s; the excited state absorption cross section is (0.9+or-0.3)*10/sup -21/ cm/sup 2/. It is shown that in spite of these upconversion effects, a high fraction of the Er/sup 3+/ can be excited at low pump powers. For pump powers between 2 and 10 mW, the optimum Er concentration is calculated. The results show that for an Er concentration of 0.5 at.%, more than 2 dB/cm net optical gain is achievable at a pump power less than 10 m

What do IPAQ questions mean to older adults? Lessons from cognitive interviews

Most questionnaires used for physical activity (PA) surveillance have been developed for adults aged ≤65 years. Given the health benefits of PA for older adults and the aging of the population, it is important to include adults aged 65+ years in PA surveillance. However, few studies have examined how well older adults understand PA surveillance questionnaires. This study aimed to document older adults' understanding of questions from the International PA Questionnaire (IPAQ), which is used worldwide for PA surveillance

Physical activity and quality of life in older women with a history of depressive symptoms

Physical activity (PA) is positively associated with health-related quality of life (HRQL) in older adults. It is not evident whether this association applies to older adults with poor mental health. This study examined associations between PA and HRQL in older women with a history of depressive symptoms. Participants were 555 Australian women born in 1921–1926 who reported depressive symptoms in 1999 on a postal survey for the Australian Longitudinal Study on Women's Health. They completed additional surveys in 2002, 2005 and 2008 that assessed HRQL and weekly minutes walking, in moderate PA, and in vigorous PA. Random effects mixed models were used to examine concurrent and prospective associations between PA and each of 10 HRQL measures (eight SF-36 subscales; two composite scales). In concurrent models, higher levels of PA were associated with better HRQL (p\ua0\ua03 point differences) were evident for physical functioning, general health, vitality and social functioning. For women in their 70s–80s with a history of depressive symptoms, PA is positively associated with HRQL concurrently, and to a lesser extent prospectively. This study extends previous work by showing significant associations in older women with a history of depressive symptoms. Incorporating PA into depression management of older women may improve their HRQL

Erbium ion implantation doping of opto-electronic materials operating at 1.5 mu m

Soda-lime silicate and Al/sub 2/O/sub 3/ waveguide films, LiNbO/sub 3/ single crystal, as well as crystal Si are doped with erbium by ion implantation. All materials show luminescence at 1.5 mu m, characteristic for Er, with lifetimes up to 12 m