Metastatic tumors to the stomach: clinical and endoscopic features.

AIM: To evaluate the clinical and endoscopic patterns in a large series of patients with metastatic tumors in the stomach. METHODS: A total of 64 patients with gastric metastases from solid malignant tumors were retrospectively examined between 1990 and 2005. The clinicopathological findings were reviewed along with tumor characteristics such as endoscopic pattern, location, size and origin of the primary sites. RESULTS: Common indications for endoscopy were anemia, bleeding and epigastric pain. Metastases presented as solitary (62.5%) or multiple (37.5%) tumors were mainly located in the middle or upper third of stomach. The main primary metastatic tumors were from breast and lung cancer and malignant melanoma. CONCLUSION: As the prognosis of cancer patients has been improving gradually, gastrointestinal (GI) metastases will be encountered more often. Endoscopic examinations should be conducted carefully in patients with malignancies, and endoscopic biopsies and information on the patient's clinical history are useful for correct diagnosis of gastric metastases

Filtro sintonizzabile basato su microrisonatori sferici e cristalli liquidi

We design an integrated optics whispering gallery microsphere resonator integrating liquid crystals as tuning medium. Our device consists of a sapphire microsphere positioned over a diffused waveguide in glass substrate. At the base of the microsphere a small volume of liquid crystal is infiltrated. We numerically evaluate the performances of the device and demonstrate a voltage tuning of the narrow band resonances

Tunable integrated optical filter made of a glass ion-exchanged waveguide and an electro-optic composite holographic grating

We report the fabrication and the optical characterization of a hybrid tunable integrated optical filter. It consists of a diffused ionexchanged channel waveguide on a borosilicate glass substrate with a cover of the same glass to form a gap filled with a holographic grating. The grating morphology, called POLICRYPS (POlymer LIquid CRYstal Polymer Slices), is made of alternating stripes of polymer and liquid crystal acting as overlayer for the underneath waveguide. The filter structure includes aluminum coplanar electrodes to electrically control the grating properties, allowing the tunability of the filter. The electric driving power required to tune the filter obtained was in the range of submilliwatts due to the efficient liquid crystal electro-optic effect

Theoretical performance analysis of an integrated optic filter made of glass waveguides and POLICRYPS holographic gratings

We present the theoretical study and the simulation of the optical field propagation in a guided wave tuneable optical filter using a composite material grating. A numerical analysis of the optical propagation has been performed by using a 3D semivectorial BPM (Beam Propagation Method) based software and the results have been compared with a matrix-transfer approach based on the effective index method. The dependency of the filter response on the index modulation depth (Dn), the length and the thickness of the grating have been also analyzed. Performance of chirped and apodized gratings were also studied. The optical filter reflection and transmission spectral responses in terms of full width at half maximum(FWHM) have been calculated

Liquid-crystal tunable filter based on sapphire microspheres

We design an integrated optoelectronic device based on the whispering-gallery modes of a sapphire microsphere integrated with a liquid-crystal tuning medium to produce a narrowband, electrically tunable, channel-dropping filter. The sapphire microsphere is glued over a diffused waveguide in a glass substrate. At the base of the microsphere, a small volume of liquid crystal is infiltrated. We numerically evaluate the performance of the device and demonstrate a voltage tuning of the narrowband resonances

Integrated optics devices based on liquid crystals

We describe the technology behind a platform for integrated optics based on liquid crystals. Design and technological issues are addressed and effective technological solutions are presented. The physical implementation of optical waveguides characterized by a practical and reproducible process based on preferential etching of crystalline silicon substrates are presented. Devices are manufactured by wet etching a Si substrates first and then by thermally growing thick SiO2 cladding layer. A nematic liquid crystal is used as core of the waveguiding devices. Experimental results on polarizing properties and single mode propagation of infrared light are presented and discussed

Tunable filter based on sapphire microspheres

We present an integrated optoelectronic device based on the whispering gallery modes of a sapphire microsphere integrated and on a diffused waveguide in a glass substrate with a liquid crystal electrically tunable medium

Distributed feedback grating in liquid crystal waveguide: a novel approach

We design a distributed feedback guided-wave device in liquid crystals, utilizing a simple geometry based on electro-optic molecular reorientation in uniaxial nematics. We numerically test the structure and demonstrate an effective Bragg reflector with voltage-tunable resonance. (C) 2009 Optical Society of Americ

Polarization properties of near-infrared light confined in nematic liquid crystal channel waveguides embedded in SiO2/Si grooves

Linear and non-linear optical properties[1] of liquid crystals (LC) make them extremely appealing for use in a wide range of different optoelectronic applications other than displays. Their high optical anisotropy (in some cases higher than 0.2) implies large phase shifts in very short optical paths. Furthermore, their strong electro-optic effect allows rapid reorientation of their optical axis with indeed very low voltages in the range of only a few volt and hence compatible with current silicon technology. In particular, this last property makes them very attractive for low power consumption photonic applications. In this communication, light polarization dependence of channel waveguides made of SiO2/Si grooves filled with the commercial nematic liquid crystal E7 is shown. Grooves were obtained by initially wet etching phosphorous-doped (1 0 0) silicon substrates and then by thermally growing SiO2 up to a thickness of about 2 μm[2]. The cross section of the groove resulted with this method was of trapezoidal shape due to the preferential etching plane of silicon at 54.7° with respect to the wafer plane. The upper width of the groove as defined from the lithographic mask was 10 μm. The processed silicon substrate was subsequently assembled into a typical LC cell with a sodalime glass plate on the top. The inner surface of the glass had been previously spin-coated with Nylon 6, which was then rubbed for the alignment of the LC molecules approximately along the grooves. Propagation of infrared laser light (1550 nm) launched at one end of the waveguide by butt coupling was observed for a channel length of 2 cm. The signal at the output of the waveguide could be also coupled to a second optical fiber. The guided light showed a good optical confinement both in theory and the experiment. The simulated output profile by means of a typical beam propagation method was found to be very similar to the one grabbed at the output of the waveguide. Furthermore, the experimentally observed polarisation dependence of the light confinement into the waveguide was correctly predicted from our model. In particular, near infrared input light was controlled by using a fiber pigtailed sequence of 1/4wave-1/2wave-1/4wave plates. A measurement of light intensity versus the angle of input light polarization will be also reported. Such measurement shows that the orthogonal polarization state, for which the optical electric field “sees” only the lower LC refractive index (ordinary), was suppressed by more than 20 dB. This was justified by the observed pre-tilt angle of the molecules with respect to the propagation direction along the channel