Seminar on Optical Isolator: Application to Photonic Integrated Circuits

Optical active devices fail to operate in a desired manner, when unwanted reflections are launched into them. An optical isolator plays an essential role in protecting optical devices from unwanted reflections. Commercially available optical isolators based on a magneto-optic Faraday effect, which are provided with optical fiber and optical beam interfaces, are hard to be integrated with other optical devices. In case of waveguide isolators, it is quite unrealizable to use a rotation of polarization, because the precise control of waveguide birefringence is needed. Several approaches have been developed to avoid the precise control of waveguide geometry, like a nonreciprocal radiation and a nonreciprocal loss isolator. An interferometric waveguide isolator, which uses a nonreciprocal phase shift provided by the first-order magneto-optic effect, has the advantages of a single polarization operation and a wide operational wavelength range. Also, the interferometric isolator is realizable in several waveguide platforms by using a magneto-optic material in a cladding layer. To achieve this, we developed a direct bonding technique of magneto-optic garnet on III-V compound semiconductors and silicon waveguides. In this talk, the integration of optical isolators will be addressed, which includes a non-magneto-optic approach. 

reference :http://www.eng.monash.edu.au

OpenRAN

Cellular telephony networks depend on an extensive wired network to provide access to the radio link. The wired network, called a radio access network, provides such functions as power control and, in CDMA networks, combination of soft handoff legs (also known as macro diversity resolution) that require coordination between multiple radio base stations and multiple mobile terminals. Existing RAN architectures for cellular systems are based on a centralized radio network controller connected by point-to-point links with the radio base transceiver stations. The existing architecture is subject to a single point of failure if the RNC fails, and is difficult to expand because adding an RNC is expensive. Also, although a network operator may have multiple radio link protocols available, most RAN architectures treat each protocol separately and require a separate RAN control protocol for each. In this article we describe a new architecture, the OpenRAN architecture, based on distributed processing model with a routed IP network as the underlying transport fabric. OpenRAN was developed by the Mobile Wireless Internet Forum IP in the RAN working group. The OpenRAN architecture applies principles to the radio access network that have been successful in reducing cost and increasing reliability in data communications networks. The result is an architecture that can serve as the basis for an integrated next-generation cellular radio access network. Access to the radio link between multiple radio base stations and between mobile terminals. In this article we discuss a new architecture for mobile wireless RANs. The architecture, called the OpenRAN, is based on a distributed processing model with a routed IP network as the underlying transport fabric

OVONIC UNIFIED MEMORY

Ovonic unified memory (OUM) is an advanced memory technology that uses a chalcogenide alloy (GeSbTe).The alloy has two states: a high resistance amorphous state and a low resistance polycrystalline state. These states are used for the representation of reset and set states respectively. The performance and attributes of the memory make it an attractive alternative to flash memory and potentially competitive with the existing non volatile memory technology. OUM, offers significantly faster write and erase speeds and higher cycling endurance than conventional Flash memory. OUM also has the advantage of a simple fabrication process that permits the design of semiconductor chips with embedded nonvolatile memory using only a few additional mask steps. In this review, the physics and operation of phase change memory will first be presented, followed by discussion of current status of development. Finally, the scaling capability of the technology will be presented. The scaling projection shows that there is no physical limit to scaling down to the 22 nm node with a number of technical challenges being identified.



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OFDMA

Orthogonal Frequency Division Multiple Access (OFDMA) is a multiple access scheme for OFDM systems. It works by assigning a subset of subcarriers to individual users.
OFDMA features
OFDMA is the 'multi-user' version of OFDM
Functions by partitioning the resources in the time-frequency space, by assigning units along the OFDM signal index and OFDM sub-carrier index
Each OFDMA user transmits symbols using sub-carriers that remain orthogonal to those of other users
More than one sub-carrier can be assigned to one user to support high rate applications
Allows simultaneous transmission from several users ⇒ better spectral efficiency
Multiuser interference is introduced if there is frequency synchronization error
The term 'OFDMA' is claimed to be a registered trademark by Runcom Technologies Ltd., with various other claimants to the underlying technologies through patents. It is used in the mobility mode of IEEE 802.16 WirelessMAN Air Interface standard, commonly referred to as WiMAX.

Organic LED

Organic LED

Scientific research in the area of semiconducting organic materials as the active substance in light emitting diodes (LEDs) has increased immensely during the last four decades. Organic semiconductors was first reported in the 60:s and then the materials where only considered to be merely a scientific curiosity. (They are named organic because they consist primarily of carbon, hydrogen and oxygen.). However when it was recognized in the eighties that many of them are photoconductive under visible light, industrial interests were attracted. Many major electronic companies, such as Philips and Pioneer, are today investing a considerable amount of money in the science of organic electronic and optoelectronic devices. The major reason for the big attention to these devices is that they possibly could be much more efficient than todays components when it comes to power consumption and produced light. Common light emitters today, Light Emitting Diodes (LEDs) and ordinary light bulbs consume more power than organic diodes do. And the strive to decrease power consumption is always something of matter. Other reasons for the industrial attention are i.e. that eventually organic full color displays will replace todays liquid crystal displays (LCDs) used in laptop computers and may even one day replace our ordinary CRT-screens. Organic light-emitting devices (OLEDs) operate on the principle of converting electrical energy into light, a phenomenon known as electroluminescence. They exploit the properties of certain organic materials which emit light when an electric current passes through them. In its simplest form, an OLED consists of a layer of this luminescent material sandwiched between two electrodes. When an electric current is passed between the electrodes, through the organic layer, light is emitted with a color that depends on the particular material used. In order to observe the light emitted by an OLED, at least one of the electrodes must be transparent. When OLEDs are used as pixels in flat panel displays they have some advantages over backlit active-matrix LCD displays - greater viewing angle, lighter weight, and quicker response. Since only the part of the display that is actually lit up consumes power, the most efficient OLEDs available today use less power. Based on these advantages, OLEDs have been proposed for a wide range of display applications including magnified microdisplays, wearable, head-mounted computers, digital cameras, personal digital assistants, smart pagers, virtual reality games, and mobile phones as well as medical, automotive, and other industrial applications.


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