Gap plasmon mode distributed feedback lasers

Unlike conventional dielectric photonic structures, metal coated or plasmonic structures can confine light on a sub-wavelength scale. It has been shown that despite high internal losses, lasing is possible in plasmonic cavities, with dimensions well below the diffraction limit of light. Due to the small size and high current density, it is possible that future metallic nano-lasers will have switching speeds in the terahertz range. Until now, integration of these lasers with other optical components was difficult since they are fully enclosed by a metal layer of several hundreds of nanometers thick. This thesis discusses the possibility of incorporating distributed feedback in plasmonic waveguides to control the wavelength of operation, to control the emissive properties of the devices and to enable coupling to waveguides. The research which was carried out can be divided in three major parts. The first part involves the analysis and design of plasmonic waveguide lasers. The optical properties of plasmonic waveguides were determined using FDTD and FEM techniques. The FDTD simulations were carried out in 2D and 3D and included the presence of gain, absorption, material dispersion and imperfections in shape. The dependence on structural and material properties was studied. After studying the behavior of basic plasmonic waveguides, the incorporation of distributed feedback through vertical groove gratings was investigated. The wavelength dependence and feedback strength were determined. Also the behavior of resonant cavities, in which this distributed feedback was incorporated, was investigated. Finally, the threshold gain requirements and spontaneous emission enhancement were determined. The second part of the project consisted of developing a fabrication process for the plasmonic waveguide lasers. Existing processing techniques, used for wafer-scale fabrication of photonic integrated circuits, have been modified to make them suitable for the fabrication of plasmonic devices. A novel, high-resolution electron beam lithography process was developed capable of defining structures with 50 nm feature sizes in the III-V material system. The effect of various processing steps on surface and material quality was studied. A full fabrication run of the devices was carried out and the devices have been mounted afterwards. Some of the devices went through additional processing steps in order to open their end-facets (using focused ion beam milling). The final part of the project involved the characterization of the fabricated devices. A new measurement setup was built, in which the devices could be imaged and measured at the same time. The measurement setup is suitable for characterization through the substrate and through an open end-facet of the device. Measurements can be carried out at temperatures ranging from 4K to room temperature, in a continuous flow cryostat. Electrically pumped, surface plasmonic lasers have been realized, with core waveguide widths well below the diffraction limit of light (min. 100 nm). The lasers have been characterized though the substrate as well as via an open end-facet. Threshold currents as low as 400 µA for 100 µm long devices have been observed. The distributed feedback lasers show line-widths below 0.5 nm (limited by the resolution of the spectrometer) and have a side-mode suppression ratio of over 20 dB. Their emission wavelength could be tuned over a 100 nm range by changing the period of the distributed feedback by 60 nm. The devices have initially been characterized at cryogenic temperatures (80K), using continuous current injection, and in a later stage also at room temperature (> 295K), using pulsed current injection

Progress in metal-insulator-metal waveguide lasers at near-infrared wavelengths

Strong light con¯nement can be achieved in metallic cavities which can con¯ne light to volumes with dimensions considerably smaller than the wavelength of light. It was commonly believed, however, that the high losses in metals are prohibitive for laser peration in metallic nano-cavities. Recently we have reported lasing in a metallic nano-cavity ¯lled with an electrically pumped semiconductor. Importantly, the manufacturing approach employed for these devices permits even greater miniaturization of semiconductor lasers. Furthermore, the approach allows for complex device shapes and the guiding of light between devices. Of particular interest are the metal-insulator-metal (MIM) waveguides. These MIM waveguides can propagate a transverse magnetic (TM0) mode which permits true deep sub-wavelength guiding of light in two dimensions. The manufacturing process is adapted to produce a variant of MIM waveguides. The presentation will look at the modeling, fabrication and operation of these devices. An overview will also be given of latest results from devices. Previously reported devices observed light that leaked out of the metallic nano cavity through the device base. This is not optimal as the lasing light travels transversally between the metal sidewalls of the pillar structure. Ideally, the transverse propagating mode needs to be coupled directly out to either a conventional dielectric waveguide or free space. We will discuss our progress in making metallic cavity nano lasers with coupling of the transverse propagating mode directly to free space, and present results from our latest attempts

Distributed Bragg grating frequency control in metallic nano lasers

We show that Bragg gratings can be readily incorporated into metallic nano-lasers which exploit waveguides with semiconductor cores, via modulation of the waveguide width. This provides a simple way to implement laser wavelength control

Metal coated DBR/DFB lasers

Metallic nano-cavities can be used to fabricate lasers of sub-wavelength dimensions. Currently, these lasers emit their light through the substrate. This complicates measurements of these devices and their integration in optical systems. Side-emission offers a way to circumvent these problems. We plan to implement side-emission via distributed feedback; this allows accurate tuning of a cavity’s resonant wavelength and its emissive properties. In this paper we will give an update of the work that has been done

Metal coated DBR/DFB lasers

Metallic nano-cavities can be used to fabricate lasers of sub-wavelength dimensions. Currently, these lasers emit their light through the substrate. This complicates measurements of these devices and their integration in optical systems. Side-emission offers a way to circumvent these problems. We plan to implement side-emission via distributed feedback; this allows accurate tuning of a cavity’s resonant wavelength and its emissive properties. In this paper we will give an update of the work that has been done

Nukuteater küberkiusamisest: õppevara põhikooli II kooliastme kunstitunniks

https://www.ester.ee/record=b5534369*es

PEMANFAATAN LIMBAH PLASTIK MENJADI KARBON AKTIF SEBAGAI ADSORBEN

Plastik memiliki banyak kegunaan dalam kehidupan manusia serta membuat segala sesuatu menjadi lebih mudah, mulai dari menjadi kemasan botol air mineral dan menjaga makanan tetap segar hingga menjadi bagian dari peralatan perlengkapan sehari-hari. Produksi plastik massal dan penanganan limbah yang tidak memadai mengancam keberlanjutan biosfer dan kehidupan laut. Untuk mengurangi akumulasi sampah plastik bisa dilakukan dengan cara karbonasi yang hasilnya berupa karbon aktif yang bisa dimanfaatkan sebagai adsorben. Ada beberapa faktor yang mempengaruhi kualitas karbon aktif salah satu contohnya adalah aktivator kimia. Penelitian ini bertujuan untuk menganalisis pengaruh jenis aktivator kimia terhadap karbon aktif yang dihasilkan dari limbah plastik sebagai adsorben dengan standar SNI 06-3730-1995. Metode konversi limbah plastik menjadi karbon aktif adalah karbonasi. Uji yang dilakukan adalah daya serap Iodin dan uji kadar air. Sedangkan aktivator kimia yang digunakan adalah KOH dan K2CO3 masing-masing dengan konsentrasi 1 M dan 3 M. Hasil Penelitian menunjukkan bahwa jenis aktivator kimia dan variasi konsentrasi berpengaruh terhadap daya serap Iodin dan kadar air. Jenis aktivator kimia yang mempunyai daya serap iodin dan kadar air yang paling bagus yaitu KOH 3 M dengan nilai 852,48 mg/g dan 8 %. Penggunaan KOH menghasilkan porositas yang lebih baik karena interaksi kalium dan perenggangan lapisan-lapisan karbon. Semakin tinggi konsentrasi aktivator semakin tinggi nilai daya serap Iodin serta semakin turun nilai kadar airnya sehingga daya adsorbsi karbon aktif semakin besar

Desigualdades en las granjas industriales con el nuevo eslogan “la máxima producción al menor coste posible”

Necesitamos ver las realidades brutales que se viven en las granjas. Hace mucho dejaron de ser pacificas y hermosas, como nos muestran en las publicidades. Con la industrialización de la agricultura, la vida en las granjas ya no es de pastizales verdes con felices animales pastando en la luz del sol: hoy los campos están llenos de establos metálicos sin ventanas, jaulas de alambre, silos y piscinas de desechos, todo para conformar las que hoy conocemos como "granjas industriales". Visto de manera sencilla, el sistema de granja industrial de agricultura moderna apunta a producir la mayor cantidad de carne, leche y huevos, de la forma más rápida y barata posible, y en la menor cantidad de espacio. Produciendo en las vacas, terneros, cerdos, gallinas, pavos, patos, gansos, conejos y otros animales, alto nivel de estrés, enfermedades, privación de espacios la cual causan grandes dolores en sus extremidades, y métodos de alimentación con grandes cantidades de antibióticos, funguicidas y otros compuestos medicamentosos que permanecen en sus cuerpos y que se transmiten al ser humano cuando se alimenta de sus ellos.Facultad de Ciencias Jurídicas y Sociale