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There is an exponential increase in internet traffic. In time there may be a demand for all optical switches to process/route data at Terabit/sec speeds. All-optical switches require a strong optical nonlinearity, and in semiconductors the strongest nonlinearities are induced by the creation of real carriers. However, whilst carriers can be created on a sub-pico second timescale, the potential repetition rate is limited by the slow 100-ps relaxation times of the carriers. In this theoretical project, report will explore a proposal for a new class of Opto-electronic device based on quantum interference effects in semiconductor quantum dots.
An optical switch coupled between the communication lines where the wave length is utilization to carry the traffic or the communication links. The optical fiber is the back bone for high speed internet. This increases the access speed for the internet. Optical fiber has a good gain property, which helps to amplify the data signal. Optical switching technology is the emerging gigabit optical networks. Optical switching technology will change the history of Tele-communication and also show greater impact on fast internet access at lower cost in future. This experiment is done for a single quantum dot not for many quantum dots because if many million quantum dots is taken it is difficult to do, utilizing many quantum dots have a very broad sample theorem and have spatial narrow band. If a single quantum dot is taken it has well defined frequency and good pulse area.
Quantum outcome is real. Devices that are now extremely recognizable, for instance transistors and lasers, depend on them. But our increasing aptitude to control substance at especially at low temperatures and in extremely small proportions (comparable to the wavelength of light, or less) continues to open up new areas where we can make things whose behavior depends crucially on the quirks of quantum mechanics.
The dots that confined to a special class of semi conductors and too small with a range below 10 Nanometers are quantum dots. These size is small so they behave differently and enabling applications that are utilized for upcoming technology. Quantum dots are sensitivity in their dot's size because they are controlled by some engineering techniques. Quantum dots were discovered by Bell labs. The main utilization of quantum dots is in high level of control because it will control the properties of any material. Both thermodynamics and kinetics involved in formation of self assembled quantum dots. Quantum dots are generally grown on GaAs and InAs elements.
This innovation narrates to the area of optoelectronic devices. More predominantly, this invention sustain to the area of optoelectronic devices include semiconductor quantum dots whose ground state emission occurs at wavelengths greater than 1350 nm at a temperature of substantially 293 K.( Paul L. Gourley,1998).
Semiconductor materials are utilized in many optoelectronic devices. The semiconductor structure is generally agreed in order that the device is optically active at a wavelength desired for that meticulous device. In many applications, particularly in telecommunications, there is a requirement to utilization wavelengths between 1250 and 1650 nm. These wavelengths are well suited to fiber optic transmission and to other fiber optic devices.( Paul L. Gourley,1998).
The optical communication systems are different from microwave communication systems in many aspects. In the case of optical systems, the carrier frequency is about 100 THz and the bit rate is about 1T bit/s. Further the spreading of optical beams is always in the forward direction due to the short wavelengths. Even though it is not suitable for broadcasting applications, it may be suitable for free space communications above the earth's atmosphere like inter satellite communications. For the terrestrial applications, unguided optical communications are not suitable because of the scattering within the atmosphere, atmospheric turbulence, fog and rain. The unguided optical communication systems played an important role in the research between 1960 and 1970. For longer range unguided optical communication systems the neodymium laser (1.06 mm) and the carbon dioxide laser (10.6 mm) were the most favorable sources. Utilizing narrow band gap compound semiconductors like indium sulphide (for neodymium laser) and cadmium mercury telluride (for CO2 laser) one can have better detection utilizing heterodyne detection techniques.
Today terabit fiber communication links have been demonstrated by the combined utilization of WDM and TDM techniques and are going to serve as the backbone of information networks for the 21st century. Highly sensitive fiber-sensing systems are also being incorporated into smart engineering systems. In order to develop new technologies that are related to different aspects of fiber communication and fiber-sensing at the optical fiber communication and sensor technology lab, we explore the research directions of fiber communication and sensing systems in the devices, the modules, and the systems.
Quantum Dots are small particles of a semiconductor material, consisting of a few hundreds to thousands of atoms. Their small size, ranging for most of the systems from 1 nm to 10 nm, is mostly responsible for their unique optical, electrical and chemical properties.
The main procedures, by which QDs can be fabricated, attaining 3D confinement of the charge carriers, include diffusion controlled growth, lithography.
More recently, techniques exploring self-assembly mechanisms are being successfully explored . Nevertheless they rely on expensive MBE or MOCVD systems. In all physical deposition approaches the resulting QDs are embedded in a solid matrix and are, therefore, more adapted to integrated optoelectronic devices (QD lasers and detectors).
TO ACCOMODATE the coming broadband network (B-ISDN), very high-speed signal processing technologies must be developed not only for transmission lines, but also transmission nodes. The goal is to handle signal rates of more than several terabit/s, so that vast amounts of information, including data and pictures, can be provided to many subscribers through optical fiber cables. To this end, novel all-optical signal processing technologies capable of superseding conventional electron-based technologies have extensively been studied. The key technologies include ultra short optical pulse generation/modulation, all-optical multiplexing/demultiplexing, optical timing extraction, optical linear or nonlinear transmission, all-optical repeating, all-optical regenerating, optical sampling, all-optical demultiplexing, etc.
Most of the present-day research effort in optical communication is directed towards achieving extremely high data transmission rate of terabits/s. With the present-day technology available, it has reached data transmission of gigabits/s. Ultrafast pulse shaping holds the promise to achieve the data transmission capacity of a terabit/s. The very high transmission capacity of a terabit can perhaps be appreciated from the fact that about million movies can be transmitted simultaneously.
This can be achieved by taking advantage of the various light modulation techniques available, like time-division multiplexing (TDM), wavelength division multiplexing (WDM), and code-division multiple accessing (CDMA).
Communication through optical fibers allows one to utilization the extremely large bandwidth of about 20 THz sustainable in the fiber, for transmitting data. With the currently available encoding and decoding schemes, one has not been able to exploit this bandwidth fully. Ultrafast pulse shaping technology can help form ultra-short bit of data streams to be transmitted as short burst of light, thereby allowing an increase in the data transfer rate. This is essentially TDM. It does not demand any ultrafast electronic devices to be operated at this fast speed, nor does it demand many changes in the present day infrastructure available for optical communication.
Another technique commonly utilized is the WDM, where the broad spectral contents of the ultrafast pulses are wavelength-encoded with an optical pulse-shaper. Generally, to encode the data at various wavelengths, we would require multiple light sources at different wavelengths.
Moreover, it also requires all these different sources to be stabilized, which is very difficult. Mode-locked laser can be utilized as a self-stabilizing source for multiple optical wavelengths. A modulator array placed within the optical pulse-shaper can be utilized to place independent data on the individual wavelength channels. This avoids the utilization of stabilized multiple laser sources at different wavelengths, since the entire wavelengths are derived from a single mode-locked laser.
Finally, in the technique of CDMA10-13, which essentially utilizes a combination of TDM and WDM techniques, an ultrafast pulse shaper helps to encode and decode signals. Encoding of ultrafast pulses can be achieved by utilizing pseudorandom phase patterns to scramble (encode) the spectral phases. This can be achieved by, say, utilizing a fixed pseudorandom phase mask. To reconstitute the original fem to second pulse, a second, phase conjugate mask is utilized to unscramble (decode) the spectral phases, thus restoring the initial pulse. If the encoding mask matches the decoding phase conjugate mask, like a key to a lock, then any phase changes introduced by the first mask are undone by the second and the original ultrafast pulse emerges unaffected.
And since utilization is made of both packing the information in time domain as well as in the frequency domain, larger rate of data transmission is achieved.
We also note that pulse shaping can be utilized to achieve the dispersion compensation necessary for ultra short pulse CDMA. One can compensate for a constant (wavelength-independent) dispersion simply by adjusting the grating separation in the pulse encoding or pulse shaping masks, in order to compensate for cubic or even higher order dispersion.
Also for high-speed communications over a long distance, data are being transmitted in the form of 'soliton' packets, which travel through the optical fiber without changing their shape much. In the subsection that follows, we will see how pulse shaping has helped to produce various kinds of 'solitons' exploiting the nonlinear optical technique, helping to undertake various experiments as well as for different applications.
Where as in optical communication these semiconductor quantum dots are nano-sized; quantum structures that allows electronic properties to be tailored through quantum confinement. These nano-structures are known to have atom-like spectra with discrete and sharp spectral lines. The similarities between atoms and quantum dots suggest the possibility of utilizing coherent optical interactions for wave function engineering. In contrast to higher dimensional semiconductor systems, quantum dots suggest the possibility of utilizing coherent optical interactions for wave function engineering in a similar way to that achieved in atoms, but with the technological advantages of a solid-state system. Thus, the results of coherent control in atoms can well be applied to localized quantum states of quantum dots, to enable wave function engineering of specific target states. In an experiment on similar lines, Steel and coworkers52 utilized picoseconds optical excitation to coherently control the excitation in a single quantum dot on a timescale that is shorter compared to the decoherence timescale. Two pulse sequences were applied to manipulate the excitonic wave function by utilizing the polarization of laser and by controlling the optical phase through time delay between the pulses. Such experiments promise the future possibility to implement various schemes for quantum computation and coherent information processing and transfer, where it is important to address and coherently control individual quantum units.
Novel optoelectronic devices like optical switches based on un-doped quantum-well structures utilizing pulse shaping techniques have been predicted. Neogi et al. in 1999 have demonstrated that besides the relaxation time of the system, tailoring the properties of the coupling pulsed laser fields via pulse shape, delay or peak power can also be utilized to manipulate the inter-band transitions of the un-doped semiconductor quantum well to enhance the switching performance, which depends on the optical nonlinearity. They have also shown how the optical nonlinearities of the inter-band transitions of semiconductor quantum well are controlled by the induced optical inter sub-band transitions with the coupling laser fields, which results in sharp resonances and ultrafast inter-band nonlinear response.
All-optical switches have much higher operating speeds compared to the electronic or optoelectronic devices. And as the technology for all-optical communication is being pursued aggressively, all-optical switches become very essential, as they would be an integral part of this technology.
Pulse shaping can also play a role in studies of all optical switching devices, which potentially can operate at speeds much higher than those, obtainable with current devices. A number of all-optical fiber switching geometries have been reported utilizing glass optical fibres23 and switching times as short as 100 fs has been demonstrated.
Nevertheless, one universal problem arises with nearly every all-optical switching device. Because it is controlled by the instantaneous optical intensity, switching can occur within a pulse, so that the high and low intensity portions of the same pulse are directed to different output ports. Such pulse break-up can degrade switching performance in a variety of all-optical switching geometries. Through the utilization of pulse shaping, problems associated with pulse break-up in all-optical switching can be largely avoided. (Friberg, 1987)
Development of quantum dot surface-emitting lasers:
A surface-emitting laser emits light perpendicular to its substrate. This laser is seen as a promising next-generation light source that will facilitate miniaturization, reduce power consumption, increase speed, allow for mass production, and permit higher packaging density relative to conventional semiconductor lasers (which emit light horizontally). In addition, the utilization of a GaAs substrate will allow for low-cost implementation of a larger light-emitting area. However, it has proven very difficult to form a surface emitting laser element on this substrate that can operate in the optical communications wavelength band. With the development of antimonide-based quantum dots, we were able to master this challenge.
Figure2 is a schematic diagram of the newly developed antimonide-based quantum dot surface-emitting laser. This laser mainly consists of an antimonide-based quantum dot active layer and two distributed Bragg reflectors (DBRs). The lower DBR mirror, just above the substrate, has a periodic structure of gallium arsenide (GaAs) and aluminum arsenide (AlAs). The active layer is made of laminated GaAs, in which the antimonide-based quantum dots are embedded. The upper DBR mirror is composed of a periodic structure of GaAs and AlAs for current injection pumping, or a similar structure of two types of dielectric thin films for optically pumping. For this surface-emitting laser, these DBR mirrors need to offer reflectivity of nearly 100%. The active layer, sandwiched between these two mirrors, acts as a micro cavity to confine the light.
Figure 3 shows an electron microscope image of the surface-emitting laser. The striped patterns in this cross-sectional view show the periodic structures of the DBR mirrors. The layer between these two mirrors is the active layer containing the quantum dots, although the dots are too small (several nanometers in diameter) to be observed directly by the microscope. When an electric current is passed through an electrode on the substrate, as shown in the upper left of Figure 3, carriers (electrons and holes) will be generated within the quantum dots to emit light. Carriers can also be generated by a method known as optical pumping. In our research we utilized both methods to evaluate laser emission.
Successful laser emissions in optical communications wavelength band:
Figure 4 shows the emission characteristics of the newly developed antimonide-based quantum dot surface-emitting lasers. We were able to observe the continuous emission of each surface-emitting laser structures at room temperature by either optical pumping or current injection, within the entire optical communications wavelength band of 1.3µm to 1.55µm. In particular, the obtained wavelength of 1.55µm represents the world's longest emission wavelength of existent surface-emitting laser structures based on GaAs substrates; this is also the most suitable wavelength for fiber-optic communications.
The construction of large-capacity flexible optical networks, utilizing both OTDM and WDM technologies, will be of vital importance. In these networks, broadband low-noise optical sources, such as the SC pulse sources, are expected to play a major role. In 1996, the first OTDM/WDM transmission experiment with a 400-Gb/s total capacity was demonstrated utilizing 100-Gb/s * 4WDMchannels generated from a single SC pulse source . This experiment utilized the striking feature of the SC source: it could generate short pulses less than 0.3 ps over the continuous spectral range (200 nm), and multi wavelength transform-limited short pulses could easily be selected by filtering with passive optical filters. Because the optical frequency characteristics, including frequency separation and stability, are determined by the filtering devices, it is easy to generate dense WDM pulses from a single SC pulse. Utilizing an AWG filter as a WDM DEMUX/MUX, 100-Gb/s * 10 WDM channels (total capacity of 1 Tb/s) OTDM/WDM transmission has successfully been demonstrated. More recently, 1.4-Tb/s transmission by 200-Gb/s OTDM * 7 channel WDM and 3-Tb/s transmission by 160-Gb/s OTDM * 19 channel WDM have also been demonstrated.( T. Morioka, H. Takara,1996).
Fig. 1. 100 Gb/s, 200 km OTDM transmission experiment. (PI-FWM: polarization-independent four-wave mixing, ML-EDFL: mode-locked Er-doped fiber laser, PM fiber: polarization maintaining fiber).
Fig. 3 illustrates the experimental set-up of 1-Tb/s OTDM/WDM transmission. The SC pulse generator consists of a stabilized actively mode-locked EDF laser that outputs 10-GHz, 1572-nm, 3.5-ps pump pulses, EDFA to amplify the pump pulses to a peak power of 1.5 W, and a 3-km single-mode DS fiber (SC fiber) for SC generation. The WDM SC spectra filtered with the AWG DEMUX/MUX have more than 80-nm bandwidth, as shown in Fig. 3. The DEMUX/MUX consists of two AWGs directly connected, having a 140-GHz channel bandwidth and 400-GHz (3.2-nm) channel spacing.( S. Kawanishi, H. Takara,,1997)
The adjacent channel crosstalk was less than 25 dB for all 10 channels ranging from 1533.6 to 1562.0 nm. The 10-WDM channels are modulated by a common LiNbO3 intensity modulator and time-division multiplexed to produce 100-Gb/s 10 channels OTDM/WDM signals by a tenfold PLC OTDM multiplexer. The OTDM/WDM signals are then amplified to 5 dBm per channel on average by a fluoride-based broadband EDFA. They are transmitted over 40-km dispersion-shifted fiber of zero-dispersion wavelength of 1561.3 nm. The output signals are filtered by three 3-nm optical band-pass filters in series to reduce the channel crosstalk.
Dispersion-compensation fibers were utilized to compensate for the transmission fiber dispersion up to 74ps/nm. The 3.5-ps, 100-Gb/s pulse waveforms before transmission at channel 5 are also shown in Fig. 3. With dispersion compensation, the output pulse waveform recovered its original pulse shape and the 100-Gb/s signals were fed into a pre-scaled PLL timing-extraction circuit and an all-optical FWM-based DEMUX. The de-multiplexed 10-Gb/s signal was directed to an optical receiver and the BER performance was measured.
With this set-up, 1-Tb/s error-free transmission over 40 km has successfully been demonstrated utilizing the 100-Gb/s 10 channel OTDM/WDM technique. In order to increase the total transmission capacity, it is essential to increase the speed of the OTDM signal itself. By employing 200-Gb/s OTDM signals together with 7-channel WDM, 1.4-Tb/s signals have successfully been transmitted within the same optical bandwidth . The main differences between the 1.4-Tb/s and 1-Tb/s experimental set-ups are as follows. The AWG filters have a 300-GHz bandwidth and 600-GHz channel spacing in order to increase the ratio of bit rate versus channel spacing. The shorter pulse-width of 2.1ps is utilized to apply twentyfold all-optical multiplexing.
All the transmitter components such as AWG-WDM filters, PLC TDM-MUXs, and booster EDFAs are PM in order to stabilize the 1.4-Tb/s signal. All the channels are in the normal dispersion region of the transmission fiber to suppress spectral broadening caused by anomalous dispersion, and common dispersion compensation with a 1.3- m zero-dispersion fiber and common WDM-DEMUX with an AWG filter are utilized. With this set-up, 1.4-Tb/s OTDM/WDM signals have been transmitted over 50 km without any bit errors.
More recently, 3-Tb/s (160 GB/s * 19 channels) OTDM/WDM transmission through 40 km of DS fiber has been reported, employing two sets of low-noise, flatly broadened SC WDM pulse sources and ultra-broadband EDFAs . The 3-Tb/s signal generator consisted of two OTDM/WDM signal generators; one for the shorter wavelength region (1540-1566 nm) and one for the longer wavelength region (1570-1609 nm). Each generator was composed of a 3-ps, 10-GHz ML-EDF laser, optical modulator, optical amplifier, and SC fiber, all of which were PM so as to stabilize the SC output spectrum. The generated 10-Gb/s SC signal pulses were time-division multiplexed by 16 times and were spectrally sliced and recombined by two sets of AWG filters with 450-GHz spacing to generate the 3-Tb/s signal. The 3-Tb/s OTDM/WDM signal was amplified by a 70-nm bandwidth telluride-based EDFA consisting of two-stage EDFAs and an intermediate gain equalizer to yield flat-gain characteristics. The zero-dispersion wavelength of the transmission DSF was 1530 nm; thus, all WDM channels were in the anomalous dispersion region. At the receiver, each channel was optically pre-amplified, de-multiplexed with an AWG filter followed by a dispersion-compensating fiber, and then de-multiplexed into a 10-Gb/s signal by an all-optical DEMUX driven by a 10-GHz clock extracted from the 160-Gb/s OTDM signal. With this set-up, 3-Tb/s error-free transmission through a 40-km DS fiber has successfully been demonstrated utilizing both sixteen folds OTDM and nineteen fold WDM techniques.( M. Nakazawa, E. Yoshida,1998).
Brief Literature Review:
Optical fibers can provide a much more reliable and versatile optical channel than the atmosphere, Kao and Hockham published a paper about the optical fiber communication system in 1966. But the fibers produced an enormous loss of 1000 dB/km. But in the atmosphere, there is a loss of few dB/km. Immediately Kao and his fellow workers realized that these high losses were a result of impurities in the fiber material. Utilizing a pure silica fiber these losses were reduced to 20dB/km in 1970 by Kapron, Keck and Maurer. At this attenuation loss, repeater spacing for optical fiber links become comparable to those of copper cable systems. Thus the optical fiber communication system became an engineering reality.
Growing attention has been focused in recent years on optical communications technologies that will allow us to flexibly handle large volumes of contents with various communications tools. To realize the so-called "ubiquitous communications society," in which people and machines, etc. will communicate utilizing multiple laser sources, we need techniques to mass-produce small, high performance optical communications lasers at low cost and with minimal energy requirements. The desirable operating wavelength band of those laser devices will be 1.3 - 1.55µm, suitable for fiber-optic communications, while lasers for wavelengths of 1.4µm or longer will be required taking free-space communications into account.
The Internet is expected to be inundated in the future with billions of gigabytes (or hexabytes) of data as high-definition video and other bandwidth-busting downloads become the norm. The cost of upgrading the Internet for this so-called "exaflood" could make Web connections too expensive for most consumers. Internet service providers may be able to keep prices down by opening up an express-lane for large data hauls.
It is estimated that 99 percent of the traffic volume of the Internet is devoted to large downloads-like movies, medical scans and financial data- that are only 1 percent of all data transfer sessions. These huge bundles are currently handled in the same way all data is handled by the Internet: the files are chopped up into little packets and then shuffled through traffic. Although this works fine for e-mail and Web pages, says MIT researcher Vincent Chan, it is very inefficient for large streams of data. An alternative, called optical flow switching (OFS), essentially opens a direct line between users that they can utilization for a few seconds all to themselves
Combine high-speed telecommunications networks with the flexible techniques for sending data over the Internet, and you get IPTV, or Internet Protocol Television, a newly emerging method for delivering digital video to homes. Rather than broadcasting hundreds of channels at a time to every subscriber's home, IPTV provides individual content on demand, by efficiently storing both live broadcasts and stored video on a provider-wide network. IPTV can also blend in voice, Internet, and other services onto a single TV screen, while offering portability to subscribers to access the television channels to which they subscribe, on different user devices and/or locations (e.g., on their laptops and even in their friend's homes). Researchers at the meeting will describe techniques for implementing IPTV at affordable costs while leveraging existing infrastructure.
Continuing strong interest in semiconductor quantum dots (QDs) is not just due to their unique physical properties, but also due to the growing number of devices which utilize these properties. QDs are a key element in a wide variety of electronic and optoelectronic devices, including single electron transistors, quantum bits, memory cells, and lasers. The properties of these devices rely on the QD electronic subsystem relaxation efficiency; therefore, the study of carrier relaxation mechanisms in QDs is of central importance. Knowledge of these relaxation phenomena is particularly important since it is intended that many nano-electronic devices will be incorporated into integrated circuits (IC). The characteristic distance between the structural elements in these ICs is expected to be several tens of nanometers.
Strong interaction of QDs with other circuit elements, viz. doped substrates, buffer and wetting layers, semiconductor quantum wells and wires, is expected over these distances.
This interaction would be expected to strongly influence the performance of the circuit, at both device and system level. A careful analysis of energy relaxation processes in QDs, induced by interactions occurring over characteristic distances of several tens of nanometers, is required.
To date, the influence of a variety of elementary excitations, either localized inside a QD or at its interface, on the relaxation processes of QD-based devices has been considered in a number of studies. The effects of confined acoustical and optical phonons (including interface ones), Plasmon's, polar on like states in QDs and the Auger-like process have been analyzed.
More realistic, multi component, QD hetero structures have also been investigated. Several studies on the influence of the QD environment on the electronic dynamics have been performed.
The effects of optical and acoustical phonons, within the barrier and the matrix, on the QD electronic subsystem have also been demonstrated. Elastic Coulomb collisions of carriers in the wetting layer with those in the dots and charge fluctuations in the impurity state due to recharging through the free electron reservoir were also shown to affect the dynamics of QD optical transitions. Evidently, QD carriers will strongly interact not only with free charges in their environs but also with any nearby excitations which are accompanied by electric fields. It has been demonstrated on an InAs/GaAs QD hetero structure, that Plasmon's and Plasmon phonons which reside in doped hetero-structure components, are strongly coupled to the QD electronic subsystem.
As a result, QD intraband carrier relaxation with a combination of emission from the substrate bulk and surface Plasmon-LO-phonon modes will dominate relaxation processes at a distance of ca. 20 nm between the QD and the doped substrate.
Optical signal processing gets organized:
Processing optical signals at terahertz rates requires both the development of basic optical logic capabilities and minimization of device dimensions down to the scale of the wavelength of light. Heinz Jaeckel of the Swiss Institute of Technology (ETH; Zurich, Switzerland) and his group have demonstrated a heterojunction bipolar transistor that operates at 70 Gb/s; their long-term goal is 160Gb/s. Jaeckel hopes to enable all-optical signal processing by developing real devices that could be incorporated into all-optical systems.
New materials and processing capabilities are fundamental to the development of such devices. Carrier lifetimes are too long in current materials to achieve the high speeds required for all-optical signal processing. Getting devices into sub millimeter dimensions requires new photonic band-gap technology development, and extending performance to terabit rates will drive the fabrication techniques for advanced integrated devices.
Jaeckel's group is pursuing the technology, design, and characterization of advanced ultrafast transistors and electronic circuits as well as optoelectronic devices based on indium-phosphate (InP) technology (see figure). These devices require fabrication capabilities in the deep submicron to sub nanometer range and advanced processing techniques.
All of this requires state-of-the-art semiconductor fabrication facilities and participation from a broadly based group of technologists and industrial partners. The ETH recently opened such a facility, called the Frontiers in Research: Space and Time (FIRST) lab. Six professors and about 40 researchers make up the core team to open the lab, which is a technology and fabrication facility focusing on micro- and nanotechnologies in the areas of III-IV semiconductors and silicon. Common research focuses include compound semiconductors and new materials; silicon for micro- and nanomechanics and micro sensors; nanostructuring of materials and surfaces; electronic and photonic devices, circuits, ICs, and advanced packaging. Specific projects focus on areas such as vertical-cavity surface-emitting lasers, nanoscale devices, silicon micro machines, quantum transport devices, quantum dots, mode-locked lasers, and all-optical switching.
The basis of next-generation high technology industries will be novel devices capable of faster operation and higher densities. Objects will be measured in fractions of microns with processes taking place on fem to second time scales. Professors involved in the lab have industrial partners, and the focus is on early-phase device developments that are difficult to achieve in most industrial laboratories. Jaeckel's group has developed a 70 Gb/s PIN photodiode photo receiver with such a partner. Going to the extremes of small size and high speeds in development labs such as FIRST today leads to the new discoveries that drive industry tomorrow. (Michael Brownell, 2002).
The concept of Towards Terabit/second all-optical switches for high-speed internet is one of the most intriguing and challenging research fields to emerge in the 21st Century. In less than a decade, this previously hidden section of the electromagnetic spectrum has caught the imagination of scientists around the world. From a research perspective, relatively little is known about how this concept manifests itself in current technology.
Both quantitative and qualitative research approaches are going to be followed. A questionnaire and qualitative report was prepared by me through the details gathered in survey of professional's publications and reports working research on Terabit/second all-optical switches for high-speed internet.
Samples for our current research:
- Internet research data gathered for Towards Terabit/second all-optical switches for high-speed internet
- The National Science Foundation NSF, is granting $3 million to a program of research and education on the Ultra-High-Capacity Optical Communications.
- This program includes, in part, novel concepts in photonic devices, advanced fiber communication systems, component technologies for broadband optical access.
- The objective is to enable the continued growth of broadband optical access and high-capacity optical communications into the next decade.
Secondary research Source:
The main source which I found is internet through which different journals, reports, and e-books downloaded and referred for understanding basics and to gain more knowledge.
And I have gone through different publications and books on different optical communication and features of opto-switches.
Recent progress in very high-speed optical signal processing and its applications to ultrafast single-channel OTDM transmission systems, as well as multi wavelength channel OTDM/WDM transmission systems, have been reviewed.
The single-channel transmission capacity has now reached to 400-640 Gb/s by utilizing newly developed OTDM technique and to 1.28 Tb/s by combining with twofold PDM. Furthermore, with the utilization of WDM technique together with the OTDM, terabit/s transmission up to 3-Tb/s capacity has been successfully demonstrated utilizing the small number of DWM channels (19-wavelength * 160 Gb/s OTDM). It has been pointed out that the successful ultrahigh speed transmission is attributed to the newly developed all-optical signal processing techniques. Although the technologies introduced here are still premature to be applicable to real systems, they are expected to play important roles in constructing future all-optical photonic networks in the up coming year.