Strategija proračuna složenih optičkih višeslojeva

The demand for very special optical coatings, having unusual optical characteristics that have no similarities with the traditional coatings, steadily increases. Typical examples are colour temperature converters, some types of narrow band reflectors, etc. A thin-film designer often encounters the very well known problem of the starting design. In this paper, a strategy of multilayer design is described. Taking an example, the target function is defined and then the complete design procedure is illustrated. The use of only two popular optical multilayer materials, namely SiO2 and TiO2 is assumed. BK7 glass and air are assumed as surrounding media. In all analysed cases, only a certain number of alternating layers can be assumed as the starting point of the design procedure. The method of global multilayer design is used in the first step, it is followed by the Tikhonravov\u27s design method, and finally by the gradient refinement. Other possible ways and methods are discussed, and some hints are given.Zahtjevi za višeslojnim optičkim prekrivima posebnih, netradicionalnih značajki u stalnom je porastu. Primjeri su pretvarači temperature boje, uskopojasni reflektori, itd. Često smo suočeni s problemom početne strukture višesloja. Ovdje se opisuje strategija proračuna višesloja. Izabrana je proizvoljna ciljna funkcija i opisan cijeli postupak oblikovanja višesloja uz pretpostavku dvaju optičkih materijala, SiO2 i TiO2. Podloga je BK7 staklo a upadno sredstvo zrak. U prvom koraku primijenjena je metoda globalnog oblikovanja, zatim je upotrebljena Tikhonravova metoda i na kraju fina gradijentna metoda

Electric field assisted dissolution of metal clusters in metal island films for photonic heterostructures

The dissolution of metal clusters in metal island films by the simultaneous application of electric field and temperature is reported. The consequent fading of surface plasmon resonance greatly modifies the optical properties of the samples. The dissolution process is verified in island films of different metals, obtained under different conditions and covered by different dielectric materials, as well as on multilayer dielectric stacks showing interferential properties. The tailoring possibilities of the optical behavior of metal island films combined with the inexpensive technical requirements of this approach open up the possibility to produce low-cost photonic heterostructures

Fractionated Illumination Improves the Outcome in the Treatment of Precancerous Lesions with Photodynamic Therapy

Photodynamic therapy (PDT) is a noninvasive therapy for non-melanoma skin cancer. The aim of this study was comparison of efficacy between fractioned versus single dose illumination in photodynamic therapy (PDT) of actinic keratosis (AK) and Bowen’s disease (BD). Fifty-one patients (36 AK and 15 BD) were treated with PDT. They were randomly arranged in two treatment groups. Group one included 26 patients (20 AK and 6 BD) that, after five hours of incubation with 20% 5-ALA, were treated with a single illumination of 100 Jcm–2 at fluence rate of 30 mWcm–2. Group two included 25 patients (16 AK and 9 BD) that, after 16 hours of incubation with 20% 5-ALA, were treated with two light fractions (50 plus 50 Jcm–2) at same fluence rate with dark interval of two hours between fractions. Twenty-four weeks later, a treated area was incubated for four hours again with 5-ALA in order to detect occult areas of abnormal skin with possible remaining tumor tissue. In case of fluorescence, histological examination was performed. In the group one, fluorescence at the end of the session was absent in 19 (73%) or very weak in 7 (27%). Residual tumor was found in 15 (75%) AK and in 4 (66.6%) BD. In the group two, fluorescence at the end of second session was more intense; in one patient (4%) was absent, very weak in 5 (20%) and weak in 19 (76%) of patients. In this group histology revealed remaining tumor tissue in only 2 (12.5%) AK and 2 (22.2%) BD. Among the patients in the first group, the remaining tumor tissue was significantly bigger (p=0.005). The treatment response with clearing of tumor tissue was significantly higher in fractionated illumination than in a single dose illumination group. Fractionated illumination scheme with 16 hours of incubation separated by two hours dark interval significantly improves the therapeutic outcome in tumor eradication