New miniaturized exhaled nitric oxide sensor based on a high Q/V mid-infrared 1D photonic crystal cavity.

A high Q/V mid-infrared 1D photonic crystal cavity in chalcogenide glass AMTIR-1 (Ge33As12Se55) resonating at λR=5.26 µm has been proposed as a key element of a sensor able to evaluate the nitric oxide (NO) concentration in the exhaled breath, namely fraction exhaled NO. The cavity design has been carried out through 3D finite-element method simulations. A Q-factor of 1.1×104 and a mode volume V=0.8 (λ/n)3, corresponding to a Q/V ratio of 1.4×104(λ/n)-3, have been obtained with a resonance transmission coefficient T=15%. A sensitivity of 10 ppb has been calculated with reference to the photothermal physical property of the material. Such a result is lower than the state-of-the-art of NO sensors proposed in literature, where hundreds of parts per trillion-level detection seem to have been achieved, but comparable with the performance obtained by commercial devices. The main advantages of the new device are in terms of footprint (=150 µm2), smaller at least 1 order of magnitude than those in literature, fast response time (only few seconds), and potential low cost. Such properties make possible in a handheld device the sensor integration in a multi-analysis system for detecting the presence of several trace gases, improving prevention, and reducing the duration of drug treatment for asthma and viral infections.

Fast light generation through velocity manipulation in two vertically-stacked ring resonators.

Speed manipulation of optical pulses is a very attractive research challenge enabling next-generation high-capacity all-optical communication networks. Pulses can be effectively slowed by using different integrated optical structures such as coupled-resonator waveguiding structures or photonic crystal cavities. Fast light generation by means of integrated photonic devices is currently a quite unexplored research field in spite of its crucial importance for all-optical pulse processing. In this paper, we report on the first theoretical demonstration of fast light generation in an ultra-compact double vertical stacked ring resonator coupled to a bus waveguide. Periodic coupling between the two rings leads to splitting and recombining of symmetric and anti-symmetric resonant modes. Re-established degenerate modes can form when a symmetric and an anti-symmetric mode having different resonance order exhibit the same resonance wavelength. Under degenerate mode conditions, wide wavelength ranges where the group velocity is negative or larger than the speed of light in vacuum are generated. The paper proves how this physical effect can be exploited to design fast light resonant devices. Moreover, conditions are also derived to obtain slow light operation regime.

Parametric analysis of 2D guided-wave photonic band gap structures.

The parametric analysis of the electromagnetic properties of 2D guided wave photonic band gap structures is reported with the aim of providing a valid tool for the optimal design. The modelling approach is based on the Bloch-Floquet method. Different lattice configurations and geometrical parameters are considered. An optimum value for the ratio between the hole (or rod) radius and the lattice constant does exist and the calculation demonstrated that it is almost independent from the etching depth, only depending on the lattice type. The results are suitable for the design optimisation of photonic crystal reflectors to be used in integrated optical devices.

Simulation of the photodynamics of azobenzene on its first excited state: comparison of full multiple spawning and surface hopping treatments.

We have studied the cis-->trans and trans-->cis photoisomerization of azobenzene after n-->pi* excitation using the full multiple spawning (FMS) method for nonadiabatic wave-packet dynamics with potential-energy surfaces and couplings determined "on the fly" from a reparametrized multiconfigurational semiempirical method. We compare the FMS results with a previous direct dynamics treatment using the same potential-energy surfaces and couplings, but with the nonadiabatic dynamics modeled using a semiclassical surface hopping (SH) method. We concentrate on the dynamical effects that determine the photoisomerization quantum yields, namely, the rate of radiationless electronic relaxation and the character of motion along the reaction coordinate. The quantal and semiclassical results are in good general agreement, confirming our previous analysis of the photodynamics. The SH method slightly overestimates the rate of excited state decay, leading in this case to lower quantum yields.

Effects of thermal annealing on the optical characteristics of k(+)-na(+) waveguides.

We present a systematic study of the changes induced in the refractive-index profile of different sets of K(+)-Na(+) ion-exchanged waveguides on soda-lime and BK7 substrates because of thermal annealing in the presence or absence of salt vapors. The concentration of potassium is recovered by secondary ion mass spectrometry, and the propagation losses are measured by means of the three-prism configuration.

Effects of thermal annealing on the optical characteristics of k -na + waveguides.

We present a systematic study of the changes induced in the refractive-index profile of different sets of K -Na + ion-exchanged waveguides on soda-lime and BK7 substrates because of thermal annealing in the presence or absence of salt vapors. The concentration of potassium is recovered by secondary ion mass spectrometry, and the propagation losses are measured by means of the three-prism configuration.

[Echography and hysteroscopy. 2 diagnostic technics compared in the identification of endometrial lesions in the postmenopause]. / Ecografia e isteroscopia. Due tecniche diagnostiche a confronto nell'identificazione delle lesioni endometriali in postmenopausa.

METHODS: In this study we compared ultrasonographic scanning of the endometrium and the hysteroscopic view with histology obtained by endometrial biopsy. RESULTS: Forty six postmenopausal women were studied, 25 symptomatic and 21 asymptomatic. In 24 cases endometrial thickness was > 5 mm, it was considered abnormal, and in 12 cases was < 5 mm. Hysteroscopy detects the presence of 7 atrophic endometrium, 19 polyps, 8 myomas, 4 cancer, 5 synechiae. Echography had a sensitivity of 90.9%, specificity of 72% and positive predictive value of 90.9%. Hysteroscopy showed a sensitivity of 96.7%, a specificity of 92.8% and a positive predictive value of 96.8%. CONCLUSIONS: In conclusion we may suggest that TV scanning allows detection of endometrial pathology with a high sensitivity so it may be used as the first diagnostic step in the screening of postmenopausal women, but it should be completed by hysteroscopic evaluation when endometrial thickness is > 5 mm also in asymptomatic women in order to detect cancer in a early stage.