Design of an optical nanoantenna with focusing subwavelength grating couplers and metallic reflector

In the development of integrated large-scale optical phase array, compact optical nanoantennas are needed. For high resolution arrays, the nanoantenna footprint and the separation between them should be as small as possible to reduce the number of interference orders in the far field [1]. In the development of this nanoantennas in our InP membrane on Silicon (IMOS) platform [2], we use deeply etch focusing grating to reduce the size [3]. In order to increase the optical power emitting up, we add a metal reflector of Silver underneath the semiconductor with a small buffer of 50 nm of 푆푖푂2. This metal layer will also works as a thermal heater, which will change the optical properties of the semiconductor changing the direction of the upcoming light. The last element to be add is a subwavelength ridge which reduces the unwanted Fresnel reflections by reducing the refractive index contrast [3]

Fabrication technology of a slot waveguide modulator in InP Membranes on Silicon (IMOS)

For the InP Membranes On Silicon (IMOS) platform [1], we developed an electrooptic modulator based on a slot-waveguide with a high nonlinear polymer. A variety of fabrication techniques are used, including electron beam lithography (EBL), optical lithography (OL), dry etching and metallization. The fabrication of such modulator requires a complex fabrication process. In this work we present and discuss the most important fabrication steps

Design of an optical nanoantenna with focusing subwavelength grating couplers and metallic reflector

In the development of integrated large-scale optical phase array, compact optical nanoantennas are needed. For high resolution arrays, the nanoantenna footprint and the separation between them should be as small as possible to reduce the number of interference orders in the far field [1]. In the development of this nanoantennas in our InP membrane on Silicon (IMOS) platform [2], we use deeply etch focusing grating to reduce the size [3]. In order to increase the optical power emitting up, we add a metal reflector of Silver underneath the semiconductor with a small buffer of 50 nm of 푆푖푂2. This metal layer will also works as a thermal heater, which will change the optical properties of the semiconductor changing the direction of the upcoming light. The last element to be add is a subwavelength ridge which reduces the unwanted Fresnel reflections by reducing the refractive index contrast [3]

Low-optical-loss, low-resistance Ag/Ge based ohmic contacts to n-type InP for membrane based waveguide devices

We present the development of Ag/Ge based ohmic contacts to n-type InP with both low contact resistances and relatively low optical losses. A specific contact resistance as low as 1.5×10-6 O cm2 is achieved by optimizing the Ge layer thickness and annealing conditions. The use of Ge instead of metal as the first deposited layer results in a low optical absorption loss in the telecommunication wavelength range. Compared to Au based contacts, the Ag based metallization also shows considerably reduced spiking effects after annealing. Contacts with different lengths are deposited on top of InP membrane waveguides to characterize the optical loss before and after annealing. A factor of 5 reduction of the propagation loss compared to the conventional Au/Ge/Ni contact is demonstrated. This allows for much more optimized designs for membrane photonic devices

Física, cuentos y poemas

A didactic strategy is designed and implements across the stories and poems, as representations of the language, for the teaching of the physics. The expression across the word facilitates the comprehension and interpretation of the concepts by the students, since these try to provoke his feelings, sensations of beauty, creativity, imagination and influence, using concepts and definitions in the field of the physics. These stories and poems are presented of individual form with the concepts and theories studied during the course, then there is done a correction of these concepts, from that the student wants to express, appearing this way a projection and introjection dynamics between the student and the teacher. Being like that an investigation of exploratory and comprehensive character, of this way the study of case is the appropriate tool.Se diseña e implementa una estrategia didáctica a través de los cuentos y poemas, como representaciones del lenguaje, para la enseñanza de la física. La expresión a través de la palabra facilita la comprensión e interpretación de los conceptos, los estudiantes pueden plasmar sus sentimientos, sensaciones de belleza, creatividad, imaginación e influencia, haciendo uso de conceptos y definiciones del campo de la física. Estos cuentos y poemas se presentan de forma individual con los conceptos y teorías estudiadas durante el curso, luego se hace una corrección de estos conceptos, a partir de lo que el estudiante desea expresar, presentándose así una dinámica de proyecciones e introyecciones entre el estudiante y el docente. Siendo así una investigación de carácter exploratorio y comprensivo, de esta forma el estudio de caso es la herramienta apropiada

Fullerene-assisted electron-beam lithography for pattern improvement and loss reduction in InP membrane waveguide devices

In this Letter, we present a method to prepare a mixed electron-beam resist composed of a positive resist (ZEP520A) and C 60 fullerene. The addition of C 60 to the ZEP resist changes the material properties under electron beam exposure significantly. An improvement in the thermal resistance of the mixed material has been demonstrated by fabricating multimode interference couplers and coupling regions of microring resonators. The fabrication of distributed Bragg reflector structures has shown improvement in terms of pattern definition accuracy with respect to the same structures fabricated with normal ZEP resist. Straight InP membrane waveguides with different lengths have been fabricated using this mixed resist. A decrease of the propagation loss from 6.6 to 3.3¿¿dB/cm has been demonstrated

Close binary companions of the HAeBe stars LkHa 198, Elias 1, HK Ori and V380 Ori

We present diffraction-limited bispectrum speckle interferometry observations of four well-known Herbig Ae/Be (HAeBe) stars, LkHa 198, Elias 1, HK Ori and V380 Ori. For two of these, LkHa 198 and Elias 1, we present the first unambiguous detection of close companions. The plane of the orbit of the new LkHa 198 companion appears to be significantly inclined to the plane of the circumprimary disk, as inferred from the orientation of the outflow. We show that the Elias 1 companion may be a convective star, and suggest that it could therefore be the true origin of the X-ray emission from this object. In the cases of HK Ori and V380 Ori, we present new measurements of the relative positions of already-known companions, indicating orbital motion. For HK Ori, photometric measurements of the brightness of the individual components in four bands allowed us to decompose the system spectral energy distribution (SED) into the two separate component SEDs. The primary exhibits a strong infrared excess which suggests the presence of circumstellar material, whereas the companion can be modelled as a naked photosphere. The infrared excess of HK Ori A was found to contribute around two thirds of the total emission from this component, suggesting that accretion power contributes significantly to the flux. Submillimetre constraints mean that the circumstellar disk cannot be particularly massive, whilst the near-infrared data indicates a high accretion rate. Either the disk lifetime is very short, or the disk must be seen in an outburst phase.Comment: 14 pages, 10 figures, 22 separate figure file

Chromatin jets define the properties of cohesin-driven in vivo loop extrusion

Complex genomes show intricate organization in three-dimensional (3D) nuclear space. Current models posit that cohesin extrudes loops to form self-interacting domains delimited by the DNA binding protein CTCF. Here, we describe and quantitatively characterize cohesin-propelled, jet-like chromatin contacts as landmarks of loop extrusion in quiescent mammalian lymphocytes. Experimental observations and polymer simulations indicate that narrow origins of loop extrusion favor jet formation. Unless constrained by CTCF, jets propagate symmetrically for 1-2 Mb, providing an estimate for the range of in vivo loop extrusion. Asymmetric CTCF binding deflects the angle of jet propagation as experimental evidence that cohesin-mediated loop extrusion can switch from bi- to unidirectional and is controlled independently in both directions. These data offer new insights into the physiological behavior of in vivo cohesin-mediated loop extrusion and further our understanding of the principles that underlie genome organization