3,184 research outputs found
Fiber optic pigtailing and packaging of photonic integrated circuits
Abstract. This work studies a coupling method and resulting coupling losses of a photonics module composed of a silicon-on-insulator (SOI) photonic integrated circuit, a 16-channel single mode fiber array and a spot size converter chip. The converter chip is used to optimize the coupling efficiency between the fiber array and the SOI circuit by matching the mode field diameter of the fiber array to that of the SOI circuit. The SOI circuit has multiple 180° loop waveguides to facilitate active alignment by optical loss measurements through edge coupling during assembly. The SOI circuit is attached to a copper plate with a printed circuit board.
The input and output couplings of the converter chip were made up using the active alignment method, a 1536 nm super luminescent light emitting diode (SLED) as a light source, an ultraviolet light curable adhesive and a computer controlled high precision alignment and assembly station. As a result, light travels through the fiber array and the spot size converter to the 180° optical loops on the SOI circuit and after that back to the fiber array through the spot size converter. The goal of this work was coupling loss of less than 4.5 decibels measured through a loop of the finished module. The coupling losses of the best and worst loops of the module were measured to be 4.4 dB and 7.9 dB, respectively. Possible reasons for the high coupling loss difference between the loops were concluded to be the inaccuracy in the waveguide facet polishing angles on the spot size converter chip, worn-out fiber connector and misalignment caused by the shrinking of the adhesive during curing.Kuituhännöitys ja integroidun fotoniikan paketointi. Tiivistelmä. Tässä työssä tutkitaan kytkentämenetelmää ja siitä aiheutuvia kytkentähäviöitä fotoniikkamoduulissa, joka koostuu integroidusta silicon-on-insulator (SOI) piiristä, 16-kanavaisesta yksimuotokuiturivistä ja spottikoon muunninsirusta. Muunninsirua käytetään optimoimaan kuiturivin ja SOI-piirin välinen kytkentätehokkuus sovittamalla kuiturivin kuiduissa ja SOI-piirissä etenevät muotokentät toisiinsa. SOI-piirissä on useita 180 asteen silmukkavalokanavia, jotka helpottavat aktiivista kohdistusta optisen häviömittauksen avulla kokoonpanon aikana. SOI-piiri on kiinnitetty kuparilevyyn piirilevyn kanssa.
Muunninsirun tulo- ja lähtökytkennät tehtiin käyttämällä aktiivista kohdistusmenetelmää, valonlähteenä 1536 nm:n superluminesenssi lediä (SLED), ultraviolettivalolla kovettuvaa liimaa sekä tietokoneohjattua erittäin tarkkaa kohdistus- ja kokoonpanoasemaa. Tämän seurauksena valo kulkee kuiturivin ja muunninsirun läpi SOI-piirin 180° optisiin silmukoihin ja sen jälkeen takaisin kuituriviin muunninsirun kautta. Tämän työn tavoitteena oli alle 4,5 desibelin kytkentähäviö mitattuna valmiin moduulin silmukasta. Moduulin parhaan ja huonoimman silmukan kytkentähäviöiksi mitattiin 4,4 dB ja 7,9 dB. Mahdollisia syitä silmukoiden väliseen suureen kytkentähäviöeroon pääteltiin olevan epätarkkuudet muunninsirun valokanavien päiden kiillotuskulmissa, kulunut kuituliitin ja liiman kutistumisesta kovettumisen aikana aiheutunut kohdistusvirhe
Space-resolved dynamics of a tracer in a disordered solid
The dynamics of a tracer particle in a glassy matrix of obstacles displays
slow complex transport as the free volume approaches a critical value and the
void space falls apart. We investigate the emerging subdiffusive motion of the
test particle by extensive molecular dynamics simulations and characterize the
spatio-temporal transport in terms of two-time correlation functions, including
the time-dependent diffusion coefficient as well as the wavenumber-dependent
intermediate scattering function. We rationalize our findings within the
framework of critical phenomena and compare our data to a dynamic scaling
theory.Comment: 10 pages, 7 figures, submitted to Journal of Non-Crystalline Solid
Deep Linking Desktop Resources
Deep Linking is the process of referring to a specific piece of web content.
Although users can browse their files in desktop environments, they are unable
to directly traverse deeper into their content using deep links. In order to
solve this issue, we demonstrate "DeepLinker", a tool which generates and
interprets deep links to desktop resources, thus enabling the reference to a
certain location within a file using a simple hyperlink. By default, the
service responds with an HTML representation of the resource along with further
links to follow. Additionally, we allow the use of RDF to interlink our deep
links with other resources.Comment: 5 pages, 2 figures, ESWC 2018 demo pape
Compact sum-of-products form of the molecular electronic Hamiltonian based on canonical polyadic decomposition
We propose an approach to represent the second-quantized electronic
Hamiltonian in a compact sum-of-products (SOP) form. The approach is based on
the canonical polyadic decomposition (CPD) of the original Hamiltonian
projected onto the sub-Fock spaces formed by groups of spin orbitals. The
algorithm for obtaining the canonical polyadic form starts from an exact
sum-of-products, which is then optimally compactified using an alternating
least-squares procedure. We discuss the relation of this specific SOP with
related forms, namely the Tucker format and the matrix product operator often
used in conjunction with matrix product states. We benchmark the method on the
electronic dynamics of an excited water molecule, trans-polyenes, and the
charge migration in glycine upon inner-valence ionization. The quantum dynamics
are performed with the multilayer multi-configuration time-dependent Hartree
method in second quantization representation (MCTDH-SQR). Other methods based
on tree-tensor Ans\"atze may profit from this general approach.Comment: 19 pages, 15 figure
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