Using microscopic semiconductor wires positioned atop a silver surface, a team of physicists from Imperial College London and the Friedrich-Schiller-Universität Jena has produced an ultra-fast laser that dramatically accelerates the interaction between light and matter. This world record-breaking laser is exciting because one day, it could help improve data communication by boosting the speed that information can be transferred, among a variety of other potential applications. The work has been published in Nature Physics.
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The secret to this new super laser lies in the physicists’ use of silver surfaces, rather than the more traditional glass. Slim layers of metal are ideal because they provide surface plasmons, which are oscillations of excited electrons that propagate along the surface of the material. When the light interacts with these waves, it can be focused more tightly than normal. The plasmons therefore effectively squeeze the light into a much smaller space. In doing so, the interaction between the light and the nanowires, which are composed of zinc oxide, was greatly enhanced.
Surface Plasmons
HOW DOES SURFACE PLASMON RESONANCE WORK?
Surface Plasmon Resonance has been established as a powerful method to monitor label-free biomolecular interactions in liquids. However, today with MP-SPR, it can deliver well beyond kinetics and equilibrium constants.
Surface plasmons
Excitation of surface plasmons is based on total internal reflection when an incident beam of p-polarized light strikes an electrically conducting gold layer at the interface of a glass sensor with high RI (Refractive Index) and an external medium (gas or liquid) with low RI. At a given angle, the excitation of surface plasmons takes place resulting in a reduced intensity of the reflected light. A slight change at the interface (e.g. a change in refractive index or formation of a nanoscale film thickness) will lead to a change in SPR signal, allowing precise measurements of thin film properties as well as surface molecular interactions in real-time. 
SPR Navi measurement principle
At specific angle of moving laser, the energy transfer and excitation of the plasmons causes a decrease in the reflected light intensity. The surface plasmon phenomena occurs in the interface between the SPR metal and the adjacent layer, thus providing information about the sample. Total internal reflection (TIR) is part of the curve with maximum light reflection.
With MP-SPR wide angle range measured enables monitoring of whole SPR peak during measurement and this also widens application range to measurements with thicker layers, in gas and with different surfaces.
In SPR NaviTM sensor slide is inserted between the prism and flow-cell. Simplification of the sensor slide layers shows that on top of glass substrate is SPR metal (Au or other metal for plasmons) and on top of that functional coating.
Measure molecule interactions with MP-SPR:
MP-SPR real time and label free measurements makes it excellent method for interaction measurements. Not only affinity but also kinetic of the binding can be measured.
There are two measurement mode available in SPR NaviTM Angular Scan and Fixed Angle measurement.
Angular Scan
When molecules binds on the sensor surface plasmons forms with different angle of incidence and SPR curve shift is seen. With SPR Navi Angular Scan measurement whole SPR curve and sensograms with different parameters can be monitored during measurement. 
Effect of growing thickness:
When layer thickness on the sensor surface is changing SPR curve will shift. Even small changes in the deposited layer thickness will cause change in the measured SPR curve. New layers can be deposited in situ or ex situ. Both thickness and refractive index of deposited layer can be determined. 
SPR THEORY
A surface plasmon is an electro-magnetic wave propagating along the surface of a thin metal layer. Optical excitation of the surface plasmon can be achieved in the so-called Kretschmann configuration, where p-polarised, collimated light beam undergoes total internal reflection at a glass/thin-metal-film/dielectric interface. The angle at which the resonance occurs is extremely sensitive to any change in the refractive index (RI) of the medium adjacent to the metal surface, and such changes can be monitored by recording intensity of reflected light when the system goes out of resonance.
The concept of surface plasmons originates in the plasma approach of Maxwell’s theory: the free electrons of a metal are treated as an electron liquid of high density (plasma) and density fluctuations occurring on the surface of such a liquid are called plasmons, surface plasmons (SP), or surface polaritons. 
According to Maxswell’s theory, surface plasmons can propagate along a metallic surface and have a spectrum of eigen frequencies (ω) related to the wave-vector (k) by a dispersion relation:
ε2= ε 2’+i ε2” and ε1 are the dielectric constant of the metal and of the medium in contact with it, respectively. Wave vector k1 of light at frequency ω travelling through the medium ε1 is described by:
where c is the speed of light in vacuum, and for vacuum (or air to some approximation) its dispersion relation is a straight line k1=ω/c (line kc in figure above). Since the SP’s dispersion relation (curve SP in figure above) never intersects the dispersion relation of light in air, they cannot be excited directly by a freely propagating beam of light incident upon the metal surface. However, it is possible to “turn down” the light line to the point where both lines cross each other.
Principal Configurations to Achieve Plasmon Excitation by Light
There are three principal configurations to achieve plasmon excitation by light. All three are shown schematically in figures below.
![Kretschmann Configuration (SPR Navi⢠uses this!) In the third configuration (c), known as the Kretschmann geometry[iv], a thin metallic layer is formed on the substrate εo and acts itself as the spacer. For the correct film thickness, the evanescent field expanding through the metal may couple to the SP on the opposite (ε2/ε1) metal surface.](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_vOg7aXv6OeSIpYzql514dYb9RFhki-rvbRvTc8lR2Mj7Othmy2tV4bjqbpI1RLQo9Sn9PD6V7Uxkhsj3ycaWGzWbYQwqz7xj-pP9baLwuGOHYz8dnqvWmQZrysrWtwwfvo0ZPQSCkOh69WLcCZtm9aFNv7Aq0vmIxp8RJ1JjEUhtxD2Dxu=s0-d)
Grating Configuration:
In the arrangement (a), light excites plasmons via a grating coupler. If the grating constant is b, then light wave vector is increased by an additional term 2Î /b, and the SP´s dispersion relation can be matched by a component of light vector parallel to the surface. For an angle of incidence equaling Θo the resonance condition takes the form:
The resonance can be observed at angle Θo as an intensity minimum of the reflected light[ii]. The disadvantage of grating-based sensors is that the light beam is incident through the sample solution, which may give some inaccuracies if the sample is absorptive.
Otto Configuration:
The two other configurations presented in figure above are based on the fact, that the light line in in dispersion figure can be “lowered” by a factor √εo, if the beam is travelling through an optically denser medium (e.g. glass) whose dielectric constant is εo. If this is the case, then plasmons can be excited by p-polarised light undergoing total internal reflection (TIR) on the glass surface, or more precisely, they are excited by an evanescent wave associated with TIR and penetrating up to the metal/air interface. Exact matching of photons and plasmons happens for the resonance condition: 
In the configuration (b), introduced by Otto,[iii] the metal surface (ε2) is separated from the medium εo by an additional dielectric layer (e.g. an air slit) having the dielectric constant ε1
Kretschmann Configuration (SPR Naviâ„¢ uses this!)
In the third configuration (c), known as the Kretschmann geometry[iv], a thin metallic layer is formed on the substrate εo and acts itself as the spacer. For the correct film thickness, the evanescent field expanding through the metal may couple to the SP on the opposite (ε2/ε1) metal surface.
General
In all three cases, momentum matching between the plasmon and the incoming photon, i.e. excitation of plasmons is evidenced by a drop in intensity of reflected light when the angle of resonance is approached. Figure below shows an example of the SPR curve measured for silver with the aid of the Kretschmann configuration. Such resonant behavior gives an advantage in biosensor applications, because the value of the resonant angle ΘR is a sensitive function of the dielectric constants of the two contacting media. Due to this property, the surface plasmon resonance can be utilized in monitoring surface reactions, as every new ad-layer formed on the metal surface causes changes in dielectric function of medium ε1, establishing new resonance angle ΘR'. The shape of the whole resonance curve, i.e. its depth and width depends on optical absorption within the metal and on radiation losses resulting from surface roughness.
Traditional SPR
Surface reaction (e.g. immunological) monitoring can be arranged in one of two ways: the “fixed angle” or the “focused beam” SPR detection.
Goniometric Fixed Angle SPR 
In the fixed angle configuration, the angle of incidence of light is fixed and chosen to be in the middle of the slope of the reflectance dip. Any shift in resonance angle ΘR can be detected as a change in intensity of reflected light when the system goes out of resonance.
Typical angle range is 1 degree.
Focused Beam SPR
The “focused beam” arrangement utilizes an idea of forming simultaneously more than one angle of incidence (an obvious property of any focused beam), and thus being able to record the whole SPR curve without the necessity of rotating the prism. The SPR curve and possible changes of its shape can be followed in real-time by a CCD array, as shown in figure below. A commercial ![The "focused beam" arrangement utilizes an idea of forming simultaneously more than one angle of incidence (an obvious property of any focused beam), and thus being able to record the whole SPR curve without the necessity of rotating the prism. The SPR curve and possible changes of its shape can be followed in real-time by a CCD array, as shown in figure below. A commercial model of the focused SPR, combined with multi-channel flow cell system, and applied to immunological studies, has been presented on the market[vi]. Another possibility is to realize the "focused beam SPR" idea in the form of an integrated optics chip for disposable use[vii].](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_tqsV1XMieh5S4Bs_4A8Sa_WJkJCgoLWqseoe6eGTP676OrgfTtQ2zVabgE4n-Za_yumFJ253VJX-axPIffFwvMG66AwgU4ieCuLgnCoaKspo3WfQ0W2_G7mobJz2gw2hSA-nPam0Fe0soi28mQnYpNuCZ0yq0Yr2lTRntucecROuPoTjEf=s0-d)
model of the focused SPR, combined with multi-channel flow cell system, and applied to immunological studies, has been presented on the market[vi]. Another possibility is to realize the “focused beam SPR” idea in the form of an integrated optics chip for disposable use[vii].
Typical RI range is 1.30-1.40.
Typical angle range is 10 degrees.
SPR Naviâ„¢
allows the performance of two types of measurements:
Angular Scan: recording of the whole resonance curve by turning the prism against the laser beam, and 
Fixed Angle Scan: (same as above) fixed angle monitoring when the prism is stopped close to the resonance angle.
Our RI range is from 1.00-1.40.
Our angle range is 40 degrees (38-78°)
This is the only configuration that enables the measurements of Multi-Parametric SPR!
Typical optical path of an MP-SPR instrument
Lower figure shows an experimental apparatus based on the Kretschmann geometry (used by SPR Naviâ„¢)that allows the performance of two types of measurements: recording of the whole resonance curve by turning the prism against the laser beam, and fixed angle monitoring when the prism is stopped close to the resonance angle. In order to improve sensitivity and accuracy of measurements, noise suppressing equipment, a light fluctuation compensation procedure, and digital data acquisition has been incorporated into the system. Optical sensitivity of this apparatus depends on the metal used (“steepness” of the slope) and is in the range Δn=10-7 for samples exposed to air, and Δn=10-6 for liquid samples[v].
![Typical optical path of an MP-SPR instrument Lower figure shows an experimental apparatus based on the Kretschmann geometry (used by SPR Naviâ¢)that allows the performance of two types of measurements: recording of the whole resonance curve by turning the prism against the laser beam, and fixed angle monitoring when the prism is stopped close to the resonance angle. In order to improve sensitivity and accuracy of measurements, noise suppressing equipment, a light fluctuation compensation procedure, and digital data acquisition has been incorporated into the system. Optical sensitivity of this apparatus depends on the metal used ("steepness" of the slope) and is in the range În=10-7 for samples exposed to air, and În=10-6 for liquid samples[v].](https://lh3.googleusercontent.com/blogger_img_proxy/AEn0k_sCWN5fzWcCNeYXbwopyFRZv2_DCRVOb-rLcmQ3fm9anmny77xIYOkQrJyGUE2X55x0V9hS8NcBSQV8fcIwkdrNoOsQtNG0rmWC8H4rRnehR-MeMr2mqO37wD-LwKM-FJHXBUMXMeCwpWJIyB6ZDpBLOkCBjNuTHjrRbpHKJHpm46lst8acg1vmhGbn9Dc=s0-d)
Typical liquid path in a semi-automated SPR instrument:
Modelling of SPR
A shape of the SPR curve can be quantitatively described by Fresnel’s equations as the reflectivity of a multilayered system for p-polarised light[viii]. This possibility can be utilised for numerical simulation and prediction of sensor performance. For example, it has been found, that the SPR signal in liquids can be improved by introduction of an additional dielectric layer between substrate (εo) and metal (ε2)[ix], or background responses can be suppressed by adding an intermediate layer with high permittivity between metal (ε2) and analyte (ε1)[x].
Modelling of the SPR response by using a computer program which calculates reflection and transmission of polarised light in a stratified structure (stack of parallel layers) sandwiched between semi-infinite substrate (prism) and ambient (sample solution) media is also possible. All media have to be assumed to be linear, homogeneous and isotropic. For each medium the refractive index and for layers also the thicknesses have been used as input data. The calculation can be based e.g. on a 2×2 scattering matrix derived by using the Fresnel complex-amplitude reflection and transmission coefficients. The scattering matrix represents the overall optical properties and is expressed as a product of the interface and layer matrices of the entire structure[xi].
The opposite procedure, i.e. fitting of measured data into a theoretical model is also possible and may lead to identification of species adsorbed to the metal surface. Theoretically, only one set of s describing an adlayer (thickness and the real and imaginary parts of the dielectric constant) can fit the theoretical curve1, but the function describing minimum fitting error has a very shallow bottom[xii], so an unequivocal solution can be easily buried under instrumental noise and measurement errors. Proper fitting procedure should take into account also the roughness associated with every real surface. Fairly good agreement of data obtained from SPR fitting, as compared with those from direct surface observations by means of an atomic force microscope (AFM), have been reported in the literature[xiii].
By boosting this interaction, the team was able to speed up the rate at which the lasers could be switched on and off to ten times faster than that of a conventional nanowire laser that uses glass. Impressively, these lasers are the fastest on record so far. Furthermore, according to study co-author Robert Röder, they may have even achieved the upper limit in terms of speed at which semiconductor lasers such as this can be operated.
But speed is not the only remarkable feature of these new lasers: they are also stable at room temperature. This means that they can be used in a wider variety of applications, for example as a means to improve communication systems by speeding up data transfer. Another possibility is that the light inside the laser could be used in ultra-high resolution imaging systems or biomedical detectors that operate at single-molecule sensitivity.
“This work is so exciting because we are engineering the interaction of light and matter to drive light generation in materials much faster than it occurs naturally,†senior author Dr. Rupert Oulton from Imperial College London said in a news release. “When we first started working on this, I would have been happy to speed up switching speeds to a picosecond, which is one trillionth of a second. But we’ve managed to go even faster, to the point where the properties of the material itself set a speed limit.â€
New Record-Breaking Laser Could Speed Up The Internet
Surface Plasmon Resonance has been established as a powerful method to monitor label-free biomolecular interactions in liquids. However, today with MP-SPR, it can deliver well beyond kinetics and equilibrium constants.
Surface plasmons
Excitation of surface plasmons is based on total internal reflection when an incident beam of p-polarized light strikes an electrically conducting gold layer at the interface of a glass sensor with high RI (Refractive Index) and an external medium (gas or liquid) with low RI. At a given angle, the excitation of surface plasmons takes place resulting in a reduced intensity of the reflected light. A slight change at the interface (e.g. a change in refractive index or formation of a nanoscale film thickness) will lead to a change in SPR signal, allowing precise measurements of thin film properties as well as surface molecular interactions in real-time.
At specific angle of moving laser, the energy transfer and excitation of the plasmons causes a decrease in the reflected light intensity. The surface plasmon phenomena occurs in the interface between the SPR metal and the adjacent layer, thus providing information about the sample. Total internal reflection (TIR) is part of the curve with maximum light reflection.
With MP-SPR wide angle range measured enables monitoring of whole SPR peak during measurement and this also widens application range to measurements with thicker layers, in gas and with different surfaces.
In SPR NaviTM sensor slide is inserted between the prism and flow-cell. Simplification of the sensor slide layers shows that on top of glass substrate is SPR metal (Au or other metal for plasmons) and on top of that functional coating.
Measure molecule interactions with MP-SPR:
MP-SPR real time and label free measurements makes it excellent method for interaction measurements. Not only affinity but also kinetic of the binding can be measured.
There are two measurement mode available in SPR NaviTM Angular Scan and Fixed Angle measurement.
Angular Scan
When molecules binds on the sensor surface plasmons forms with different angle of incidence and SPR curve shift is seen. With SPR Navi Angular Scan measurement whole SPR curve and sensograms with different parameters can be monitored during measurement.
Effect of growing thickness:
When layer thickness on the sensor surface is changing SPR curve will shift. Even small changes in the deposited layer thickness will cause change in the measured SPR curve. New layers can be deposited in situ or ex situ. Both thickness and refractive index of deposited layer can be determined.
SPR THEORY
A surface plasmon is an electro-magnetic wave propagating along the surface of a thin metal layer. Optical excitation of the surface plasmon can be achieved in the so-called Kretschmann configuration, where p-polarised, collimated light beam undergoes total internal reflection at a glass/thin-metal-film/dielectric interface. The angle at which the resonance occurs is extremely sensitive to any change in the refractive index (RI) of the medium adjacent to the metal surface, and such changes can be monitored by recording intensity of reflected light when the system goes out of resonance.
The concept of surface plasmons originates in the plasma approach of Maxwell’s theory: the free electrons of a metal are treated as an electron liquid of high density (plasma) and density fluctuations occurring on the surface of such a liquid are called plasmons, surface plasmons (SP), or surface polaritons.
According to Maxswell’s theory, surface plasmons can propagate along a metallic surface and have a spectrum of eigen frequencies (ω) related to the wave-vector (k) by a dispersion relation:
ε2= ε 2’+i ε2” and ε1 are the dielectric constant of the metal and of the medium in contact with it, respectively. Wave vector k1 of light at frequency ω travelling through the medium ε1 is described by:
Principal Configurations to Achieve Plasmon Excitation by Light
There are three principal configurations to achieve plasmon excitation by light. All three are shown schematically in figures below.
![Kretschmann Configuration (SPR Navi⢠uses this!) In the third configuration (c), known as the Kretschmann geometry[iv], a thin metallic layer is formed on the substrate εo and acts itself as the spacer. For the correct film thickness, the evanescent field expanding through the metal may couple to the SP on the opposite (ε2/ε1) metal surface.](http://www.freedawn.co.uk/scientia/wp-content/uploads/2014/10/65214c5d7f5e59d499b5ea969e087268.png)
Grating Configuration:
In the arrangement (a), light excites plasmons via a grating coupler. If the grating constant is b, then light wave vector is increased by an additional term 2Î /b, and the SP´s dispersion relation can be matched by a component of light vector parallel to the surface. For an angle of incidence equaling Θo the resonance condition takes the form:
Otto Configuration:
The two other configurations presented in figure above are based on the fact, that the light line in in dispersion figure can be “lowered” by a factor √εo, if the beam is travelling through an optically denser medium (e.g. glass) whose dielectric constant is εo. If this is the case, then plasmons can be excited by p-polarised light undergoing total internal reflection (TIR) on the glass surface, or more precisely, they are excited by an evanescent wave associated with TIR and penetrating up to the metal/air interface. Exact matching of photons and plasmons happens for the resonance condition: 
Kretschmann Configuration (SPR Naviâ„¢ uses this!)
In the third configuration (c), known as the Kretschmann geometry[iv], a thin metallic layer is formed on the substrate εo and acts itself as the spacer. For the correct film thickness, the evanescent field expanding through the metal may couple to the SP on the opposite (ε2/ε1) metal surface.
General
In all three cases, momentum matching between the plasmon and the incoming photon, i.e. excitation of plasmons is evidenced by a drop in intensity of reflected light when the angle of resonance is approached. Figure below shows an example of the SPR curve measured for silver with the aid of the Kretschmann configuration. Such resonant behavior gives an advantage in biosensor applications, because the value of the resonant angle ΘR is a sensitive function of the dielectric constants of the two contacting media. Due to this property, the surface plasmon resonance can be utilized in monitoring surface reactions, as every new ad-layer formed on the metal surface causes changes in dielectric function of medium ε1, establishing new resonance angle ΘR'. The shape of the whole resonance curve, i.e. its depth and width depends on optical absorption within the metal and on radiation losses resulting from surface roughness.
Traditional SPR
Surface reaction (e.g. immunological) monitoring can be arranged in one of two ways: the “fixed angle” or the “focused beam” SPR detection.
Goniometric Fixed Angle SPR
In the fixed angle configuration, the angle of incidence of light is fixed and chosen to be in the middle of the slope of the reflectance dip. Any shift in resonance angle ΘR can be detected as a change in intensity of reflected light when the system goes out of resonance.
Typical angle range is 1 degree.
Focused Beam SPR
The “focused beam” arrangement utilizes an idea of forming simultaneously more than one angle of incidence (an obvious property of any focused beam), and thus being able to record the whole SPR curve without the necessity of rotating the prism. The SPR curve and possible changes of its shape can be followed in real-time by a CCD array, as shown in figure below. A commercial ![The "focused beam" arrangement utilizes an idea of forming simultaneously more than one angle of incidence (an obvious property of any focused beam), and thus being able to record the whole SPR curve without the necessity of rotating the prism. The SPR curve and possible changes of its shape can be followed in real-time by a CCD array, as shown in figure below. A commercial model of the focused SPR, combined with multi-channel flow cell system, and applied to immunological studies, has been presented on the market[vi]. Another possibility is to realize the "focused beam SPR" idea in the form of an integrated optics chip for disposable use[vii].](http://www.freedawn.co.uk/scientia/wp-content/uploads/2014/10/20c1a2aee486f458241ed27ce0b28442.png)
Typical RI range is 1.30-1.40.
Typical angle range is 10 degrees.
SPR Naviâ„¢
allows the performance of two types of measurements:
Angular Scan: recording of the whole resonance curve by turning the prism against the laser beam, and
Fixed Angle Scan: (same as above) fixed angle monitoring when the prism is stopped close to the resonance angle.
Our RI range is from 1.00-1.40.
Our angle range is 40 degrees (38-78°)
This is the only configuration that enables the measurements of Multi-Parametric SPR!
Typical optical path of an MP-SPR instrument
Lower figure shows an experimental apparatus based on the Kretschmann geometry (used by SPR Naviâ„¢)that allows the performance of two types of measurements: recording of the whole resonance curve by turning the prism against the laser beam, and fixed angle monitoring when the prism is stopped close to the resonance angle. In order to improve sensitivity and accuracy of measurements, noise suppressing equipment, a light fluctuation compensation procedure, and digital data acquisition has been incorporated into the system. Optical sensitivity of this apparatus depends on the metal used (“steepness” of the slope) and is in the range Δn=10-7 for samples exposed to air, and Δn=10-6 for liquid samples[v].
![Typical optical path of an MP-SPR instrument Lower figure shows an experimental apparatus based on the Kretschmann geometry (used by SPR Naviâ¢)that allows the performance of two types of measurements: recording of the whole resonance curve by turning the prism against the laser beam, and fixed angle monitoring when the prism is stopped close to the resonance angle. In order to improve sensitivity and accuracy of measurements, noise suppressing equipment, a light fluctuation compensation procedure, and digital data acquisition has been incorporated into the system. Optical sensitivity of this apparatus depends on the metal used ("steepness" of the slope) and is in the range În=10-7 for samples exposed to air, and În=10-6 for liquid samples[v].](http://www.freedawn.co.uk/scientia/wp-content/uploads/2014/10/4a01cc5b7afe264e20fa3d7d3a6710bf.png)
Typical liquid path in a semi-automated SPR instrument:
Modelling of SPR
A shape of the SPR curve can be quantitatively described by Fresnel’s equations as the reflectivity of a multilayered system for p-polarised light[viii]. This possibility can be utilised for numerical simulation and prediction of sensor performance. For example, it has been found, that the SPR signal in liquids can be improved by introduction of an additional dielectric layer between substrate (εo) and metal (ε2)[ix], or background responses can be suppressed by adding an intermediate layer with high permittivity between metal (ε2) and analyte (ε1)[x].
Modelling of the SPR response by using a computer program which calculates reflection and transmission of polarised light in a stratified structure (stack of parallel layers) sandwiched between semi-infinite substrate (prism) and ambient (sample solution) media is also possible. All media have to be assumed to be linear, homogeneous and isotropic. For each medium the refractive index and for layers also the thicknesses have been used as input data. The calculation can be based e.g. on a 2×2 scattering matrix derived by using the Fresnel complex-amplitude reflection and transmission coefficients. The scattering matrix represents the overall optical properties and is expressed as a product of the interface and layer matrices of the entire structure[xi].
The opposite procedure, i.e. fitting of measured data into a theoretical model is also possible and may lead to identification of species adsorbed to the metal surface. Theoretically, only one set of s describing an adlayer (thickness and the real and imaginary parts of the dielectric constant) can fit the theoretical curve1, but the function describing minimum fitting error has a very shallow bottom[xii], so an unequivocal solution can be easily buried under instrumental noise and measurement errors. Proper fitting procedure should take into account also the roughness associated with every real surface. Fairly good agreement of data obtained from SPR fitting, as compared with those from direct surface observations by means of an atomic force microscope (AFM), have been reported in the literature[xiii].
By boosting this interaction, the team was able to speed up the rate at which the lasers could be switched on and off to ten times faster than that of a conventional nanowire laser that uses glass. Impressively, these lasers are the fastest on record so far. Furthermore, according to study co-author Robert Röder, they may have even achieved the upper limit in terms of speed at which semiconductor lasers such as this can be operated.
But speed is not the only remarkable feature of these new lasers: they are also stable at room temperature. This means that they can be used in a wider variety of applications, for example as a means to improve communication systems by speeding up data transfer. Another possibility is that the light inside the laser could be used in ultra-high resolution imaging systems or biomedical detectors that operate at single-molecule sensitivity.
“This work is so exciting because we are engineering the interaction of light and matter to drive light generation in materials much faster than it occurs naturally,†senior author Dr. Rupert Oulton from Imperial College London said in a news release. “When we first started working on this, I would have been happy to speed up switching speeds to a picosecond, which is one trillionth of a second. But we’ve managed to go even faster, to the point where the properties of the material itself set a speed limit.â€
New Record-Breaking Laser Could Speed Up The Internet
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