ABSTRACT
In 1947 Bell Labs created the world’s first transistor, which resulted in a technological.revolution..It.would.be.hard.to.imagine.the.world.today.without.the. invention.of. the. transistor..The.electronics. in. the. car,. radio,. television,.computer,.microwave-everything.is.based.on.the.transistor..The.size.of.transistors.has.reduced.dramatically.over.the.years,.thereby.enabling.more.transistors.per.chip.and.faster.processor.speeds..The.number.of. transistors. per. chip. doubles. every. two. years. following.Moore’s. law.. In.1971.the.Intel.4004.processor.had.2300.transistors.and.processor.speeds.of.92,000.operations.per.second..The.modern.transistor.can.be.as.small.as.tens.of.nanometers,.with.~2.billion. transistors.per. chip,. resulting. in.processor.speeds.of.~2.GHz,.or.billions.of.operations.per.second..The.rapid.reduction.in. the. size. of. electronic. components. has. pushed. ahead. the. technology.
revolution,. resulting. in.smaller.computing.devices.with.greater.processing.speeds..However,.the.size.of.the.transistor.is.approaching.a.fundamental.limit.[1]..As.the.transistor.size.approaches.that.of.several.nanometers,.the.interactions.of.individual.atoms.must.be.taken.into.account..These.are.known.as.quantum. effects. To overcome this fundamental limit and continue reducing the size and.increasing.the.speed.of.technology,.alternatives.to.electronics.would.be.advantageous..Since.light.photons.can.travel.faster.than.electrons,.optics.is.a.possible.alternative..However,. there. is.a.major.drawback.in.using.optical. devices. Conventional devices like optical fibres are generally diffraction limited..This.limits.the.useful.minimum.size.of.a.conventional.optical.device.to.~λ/2n,.where.λ.is.the.wavelength.of.light.and.n.is.the.refractive.index.of.the.medium.[2,.3]..Conventional.waveguides.can.be.created.with.dimensions. smaller than are allowed by the diffraction limit, but the light will be poorly confined. For example, take a glass cylinder of index 1.5 and diameter 150 nm..The.diameter.of.this.cylinder. is.smaller.than.210.nm.for.an.excitation.wavelength. of. 633.nm. (λ/2n),. so. the. device. is. smaller. than. is. allowed.by. the diffraction limit. As can be seen from the field distribution (Fig. 1.1a), a cylinder.of.these.dimensions.for.this.wavelength.cannot.guide.the.light,.and.the.light.leaks.out.of.the.cylinder.and.into.the.surrounding.environment.
