Рубрика:
16
transistor heralded a new era in technology. Our world would not be the same without
it. Vahid Sandoghdar and his Nano-optics group of researchers at the Swiss Federal
Institute of Technology (ETH) in Zurich have now shown that a single molecule can
actually perform on photons all the operations that a standard transistor can perform
on electrons — a huge step forward towards all-optical computation.
Where does the advantage of using photons instead of electrons lie? Light is fast,
faster than anything else. Light is already the standard tool for telecommunications:
optical fibers have been steadily substituting old copper cables with overwhelming
advantages in terms of performance. Nonetheless, computation is still mainly
performed by electrons in electronic devices. The use of photons instead could speed
things up, and cutting-edge research is already exploring various optical alternatives
to electronics, including those based on metamaterials or excitons.
The transistor is the fundamental building block of almost all electronic
equipment today. Transistors are used to control the flow of electrons in electrical
signals. A low-intensity electrical power is able to make the transistor function as a
gate that controls another incoming electrical signal of greater intensity, in the same
way that a valve controls water flow from a tap. When the first signal reaches a
certain threshold, the gate opens and lets the incoming electrical flow from the larger
power supply go through. Below that threshold, the gate closes. The job of the
transistor is, therefore, to amplify or attenuate an incoming electrical signal
depending on a controlling, lower-intensity current. Another way of seeing transistors
is as a binary switch: for example, an open gate can be encoded as a digital 1 and a
closed gate as a digital 0. Transistors are a key component in electronic devices such
as computers because they can be arranged into networks and perform all kinds of
binary operations.
Nonetheless, "these basic operations... when performed with electrons, present
limitations, such as losses, heating, and cross-talks between electrons. It would be
interesting if the same operations could be performed using light," says Sandoghdar.
The main advantage of light is that it is faster than anything else, and using photons
instead of electrons could greatly speed things up. "This opens new difficulties,
though. Controlling light by using light is not possible, since photons do not interact
between themselves."
Sandoghdar and his team at ETH have overcome this challenge by using single
molecules to mediate interactions between photons. Molecules can thus emit light in
a process called stimulated emission: when bombarded with photons of the correct
energy, electrons within a molecule can reach an excitation state and then come back
to normal by releasing new, identical photons. However, "stimulated emission in
molecules is usually an inefficient process. By going to low temperature in order to
increase the molecular cross-section and by focusing light to diffraction limit, we
achieved the higher efficiency needed to perform our experiment," Sandoghdar says.
Notes:
• breakthrough - достижение, успех, открытие
• denominator - общий знаменатель
, сходные характеристики
• herald - возвещать; извещать, объявлять, предрекать, предсказывать
Страницы
- « первая
- ‹ предыдущая
- …
- 14
- 15
- 16
- 17
- 18
- …
- следующая ›
- последняя »
