{"id":18855,"date":"2009-07-04T14:57:00","date_gmt":"2009-07-04T14:57:00","guid":{"rendered":"http:\/\/198.74.50.173\/2009\/07\/laser-swtiched-optical-transistor-could.html"},"modified":"2017-04-07T05:28:47","modified_gmt":"2017-04-07T05:28:47","slug":"laser-swtiched-optical-transistor-could","status":"publish","type":"post","link":"https:\/\/www.nextbigfuture.com\/2009\/07\/laser-swtiched-optical-transistor-could.html","title":{"rendered":"Laser Switched Optical Transistor Could Enable future generation of ultrafast light-based computers"},"content":{"rendered":"

\"\"id=\"BLOGGER_PHOTO_ID_5354620935073582546\"<\/a>
An artist’s impression of a molecule acting as a transistor that makes it possible to use one laser beam to tune the power of another (Image: Robert Lettow)<\/i><\/p>\n

An optical transistor that uses one laser beam to control another could form the heart of a future generation of ultrafast light-based computers, say Swiss researchers.<\/a><\/p>\n

Conventional computers are based on transistors, which allow one electrode to control the current moving through the device and are combined to form logic gates and processors. The new component achieves the same thing, but for laser beams, not electric currents.<\/p>\n

A green laser beam is used to control the power of an orange laser beam passing through the device.<\/p>\n

They suspended tetradecane, a hydrocarbon dye, in an organic liquid. They then froze the suspension to -272 \u00b0C using liquid helium \u2013 creating a crystalline matrix in which individual dye molecules could be targeted with lasers.<\/p>\n

When a finely tuned orange laser beam is trained on a dye molecule, it efficiently soaks up most of it up \u2013 leaving a much weaker “output” beam to continue beyond the dye.<\/p>\n

But when the molecule is also targeted with a green laser beam, it starts to produce strong orange light of its own and so boosts the power of the orange output beam.<\/p>\n

This effect is down to the hydrocarbon molecule absorbing the green light, only to lose the equivalent energy in the form of orange light.<\/p>\n

“That light constructively interferes with the incoming orange beam and makes it brighter,” says Sandoghar’s colleague Jaesuk Hwang.<\/p><\/blockquote>\n

Abstract at the journal Nature: A single-molecule optical transistor<\/b><\/a><\/p>\n

\"\"id=\"BLOGGER_PHOTO_ID_5354623203972256610\"<\/a>
a, Energy level scheme of a molecule with ground state (|1), and ground (|2) and first excited (|3) vibrational states of the first electronic excited state. Manifold |4 shows the vibronic levels of the electronic ground state, which decay rapidly to |1. Blue arrow, excitation by the gate beam; green double-headed arrow, coherent interaction of the CW source beam with the zero-phonon line (ZPL); red arrow, Stokes-shifted fluorescence; black dashed arrows, non-radiative internal conversion. b, Time-domain description of laser excitations and corresponding response of the molecule simulated by the Bloch equations with periodic boundary conditions. Blue spikes and red curve represent the pump laser pulses and the population of the excited state |2, respectively. Black curve shows the time trajectory of Im(21). Straight green line indicates the constant probe laser intensity that is on at all times. Inset, magnified view of curves during a laser pulse. c, Schematic diagram of the optical set-up. BS, beam splitter; LP, long-pass filter; BP, band-pass filter; HWP, half-wave plate; LPol, linear polarizer; S, sample; SIL, solid-immersion lens; PD1, PD2, avalanche photodiodes. Transmission of the probe beam (green) is monitored on PD1, and the Stokes-shifted fluorescence (red) is recorded on PD2.<\/i><\/p>

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