20-04-2013, 03:17 PM
OPTICAL COMPUTING
OPTICAL COMPUTING.pptm (Size: 1.97 MB / Downloads: 24)
INTRODUCTION
With the growth of computing technology the need of high performance computers (HPC) has significantly increased.
Hot research area in 1980’s. Tapered off due to materials limitations.
Optical computing technology is, in general, developing in two directions.
One is Electro optical hybrids. Another is to generate a computer which perform all operations in optical mode.
In recent years, a number of devices that can ultimately lead us to real optical computers have already been manufactured. These include optical logic gates, optical switches, optical interconnections and optical memory.
NEED FOR OPTICAL COMPUTING
Uses the PHOTONS in visible light or infrared ( IR ) beams,
Immune to electromagnetic interference.
Free from electrical short circuits.
Low-loss transmission and provide large bandwidth.
Compact, lightweight, and inexpensive to manufacture, and more facile with stored information than magnetic materials.
Data processing can be done much easier and less expensive in parallel.
A calculation that takes a conventional electronic computer more than 11 years to complete could be performed by an optical computer in a single hour
SOME KEY OPTICAL COMPONENTS FOR COMPUTING1.VCSEL (VERTICAL CAVITY SURFACE EMITTING LASER)
VCSEL is a diode that emits light in a cylindrical beam vertically from the surface of a fabricated wafer.
Offers significant advantages when compared to the edge-emitting lasers
It have two special semiconductor materials sandwiching an active layer where all the action takes place.
Several layers of partially reflective mirrors above and below the active layer.
It emit light at just one wavelength.
WDM (WAVELENGTH DIVISION MULTIPLEXING)
It is a method of sending many different wavelengths down the same optical fiber.
It can transmit up to 32 wavelengths through a single fiber.
Nowadays DWDM (Dense wavelength division multiplexing) is used. This can transmit up to 1000 wavelengths through a single fiber
ROLE OF NLO IN OPTICAL COMPUTING
NLO are those, which interact with light and modulate its properties.
Organic materials have High nonlinearities, Flexibility of molecular design, Damage resistance to optical radiations.
Some organic materials belonging to the classes of phthalocyanines and polydiacetylenes are used for optical thin films and wave guides.
OPTICAL NAND GATE WORKING
In an optical NAND gate the phthalocyanine film is replaced by a hollow fiber filled with polydiacetylene.
Nd:YAG green picosecond laser pulse was sent collinearly with red cw He-Ne laser onto one end of the fiber.
At the other end of the fiber a lens was focusing the output on to the narrow slit of a monochrometer with its grating set for the red He-Ne laser.
When both He-Ne laser and Nd:YAG laser are present there will be no output at the oscilloscope. If either one or none of the laser beams are present we get the output at the oscilloscope showing NAND function.
WORKING
The 780nm light emitted from AlGaAs/GaAs laser diodes is collimated by a lens and focused to a diameter of about 1micrometer on the disk.
If there is no pit where the light is incident, it is reflected at the Al mirror of the disk and returns to the lens.
If there is a pit where light is incident, the amount of reflected light decreases tremendously because the reflected lights are almost cancelled by interference.
The reflected light is allowed to pass through a quarter wave plate and beam splitter.
Polarization takes place at the beam splitter. This optical signal is converted into electrical form using a photodiode.
OPTICAL PROCESSOR
There are no all-optical processors available commercially, there are opto-electronic hybrid optical processors available.
Intel has already designed and created a photonic processor, which is an opto-electronic hybrid processor. The processor is an entirely solid-state photonic processor assembly - a chip which processes data as light waves
Another company named Lenslet Ltd has created the world's first commercial optical digital signal processor. The processor is specified to run at a speed of 8 Tera (8,000 Giga) operations per second, one thousand times faster than any known DSP.
OPTICAL COMPUTING.pptm (Size: 1.97 MB / Downloads: 24)
INTRODUCTION
With the growth of computing technology the need of high performance computers (HPC) has significantly increased.
Hot research area in 1980’s. Tapered off due to materials limitations.
Optical computing technology is, in general, developing in two directions.
One is Electro optical hybrids. Another is to generate a computer which perform all operations in optical mode.
In recent years, a number of devices that can ultimately lead us to real optical computers have already been manufactured. These include optical logic gates, optical switches, optical interconnections and optical memory.
NEED FOR OPTICAL COMPUTING
Uses the PHOTONS in visible light or infrared ( IR ) beams,
Immune to electromagnetic interference.
Free from electrical short circuits.
Low-loss transmission and provide large bandwidth.
Compact, lightweight, and inexpensive to manufacture, and more facile with stored information than magnetic materials.
Data processing can be done much easier and less expensive in parallel.
A calculation that takes a conventional electronic computer more than 11 years to complete could be performed by an optical computer in a single hour
SOME KEY OPTICAL COMPONENTS FOR COMPUTING1.VCSEL (VERTICAL CAVITY SURFACE EMITTING LASER)
VCSEL is a diode that emits light in a cylindrical beam vertically from the surface of a fabricated wafer.
Offers significant advantages when compared to the edge-emitting lasers
It have two special semiconductor materials sandwiching an active layer where all the action takes place.
Several layers of partially reflective mirrors above and below the active layer.
It emit light at just one wavelength.
WDM (WAVELENGTH DIVISION MULTIPLEXING)
It is a method of sending many different wavelengths down the same optical fiber.
It can transmit up to 32 wavelengths through a single fiber.
Nowadays DWDM (Dense wavelength division multiplexing) is used. This can transmit up to 1000 wavelengths through a single fiber
ROLE OF NLO IN OPTICAL COMPUTING
NLO are those, which interact with light and modulate its properties.
Organic materials have High nonlinearities, Flexibility of molecular design, Damage resistance to optical radiations.
Some organic materials belonging to the classes of phthalocyanines and polydiacetylenes are used for optical thin films and wave guides.
OPTICAL NAND GATE WORKING
In an optical NAND gate the phthalocyanine film is replaced by a hollow fiber filled with polydiacetylene.
Nd:YAG green picosecond laser pulse was sent collinearly with red cw He-Ne laser onto one end of the fiber.
At the other end of the fiber a lens was focusing the output on to the narrow slit of a monochrometer with its grating set for the red He-Ne laser.
When both He-Ne laser and Nd:YAG laser are present there will be no output at the oscilloscope. If either one or none of the laser beams are present we get the output at the oscilloscope showing NAND function.
WORKING
The 780nm light emitted from AlGaAs/GaAs laser diodes is collimated by a lens and focused to a diameter of about 1micrometer on the disk.
If there is no pit where the light is incident, it is reflected at the Al mirror of the disk and returns to the lens.
If there is a pit where light is incident, the amount of reflected light decreases tremendously because the reflected lights are almost cancelled by interference.
The reflected light is allowed to pass through a quarter wave plate and beam splitter.
Polarization takes place at the beam splitter. This optical signal is converted into electrical form using a photodiode.
OPTICAL PROCESSOR
There are no all-optical processors available commercially, there are opto-electronic hybrid optical processors available.
Intel has already designed and created a photonic processor, which is an opto-electronic hybrid processor. The processor is an entirely solid-state photonic processor assembly - a chip which processes data as light waves
Another company named Lenslet Ltd has created the world's first commercial optical digital signal processor. The processor is specified to run at a speed of 8 Tera (8,000 Giga) operations per second, one thousand times faster than any known DSP.