Water acts as an 'optical switch' on light quantum circuits.

By using water to ' burn ' light, scientists designed a light quantum circuit inside a photonic crystal that incorporates many optical elements. Due to the optical equivalent of an electronic circuit, this design marks another way on understanding all optical devices used in communications and information technology applications.

'All optical devices use light instead of electrons to transmit information' co-author Francesca Intonti explained to PhysOrg.com. 'Light has many advantages over electrons. It can move in a dielectric material at a very high rate compared to an electron transported in a metal wire. Light can also transmit a large amount of information every second. Bandwidth of materials

Francesca Intonti and her colleagues created this curvilinear pathway by filling the pores of photonic crystals with water solution, creating a " leak " in the gap. amount and allow light flow. (Photo: Intonti and colleagues)

dielectric is much larger than metal. Moreover, light quanta does not interact as strongly as electrons, which helps to reduce energy consumption. '

In his research, Intonti and his colleagues turned light quantum crystal holes into light quantum circuits with fluid permeability with a specific refractive index. For years, scientists have been exploiting photonic crystals because of the cyclic arrangement of the refractive index that causes light to be reduced at some frequency. This structure leads to an energy gap, or a frequency range where light cannot travel through the crystal.

By selecting a liquid with a large refractive index, Intonti and his colleagues can provide a permissible state within the energy gap. In their experiments, the scientists used aqueous solution and a colored organic dye, Rhodamine 6G (used for fluorescence observation).

Intonti said that 'In light quantum crystals, you can give a permissive state in the gap of energy by deliberately giving a defect in another perfect crystal.' 'So to create a permissive state in the energy gap, we physically propose a solution of Rhodamine in a single crystal hole: this hole acts as a defect. decide the appearance of a permissive state in the energy gap. '

The amount of liquid in a single light quantum crystal hole is only about 1/1000 the volume of 1 droplet that is used in inkjet printers. To work on this ratio, scientists used a micro-permeability system - the first to be developed for the transport of fluids in biological cells - to achieve position accuracy. 0.1 micrometers. This micro-permeability system is equipped with an integrated optical microscope lens, allowing scientists to locally adjust the refractive index of crystals, creating an optical version of an electronic circuit.

The micro-permeability (micrometer) system allows liquids to enter pores in photonic crystals with droplets smaller than 1fm (1 fm = 10-15m).Penetration (penetration) is observed by the same focal laser scanning microscope (CLSM) mounted on top of a standard microscope lens.(Photo: Intonti, and colleagues).

Since writing on each pixel is made by adding liquid into the pores, Intonti and colleagues can also erase and record pixels by moving and replacing liquids, and / or choosing holes Different to put liquid into. To help liquids enter narrow holes, scientists coated the thin 1-layer SiO ₂ walls (a water-repellent compound). Then, by adding a chemical to the liquid, the scientists can dissolve SiO ₂ , creating an impermeable hole, and allowing for easy removal of the liquid.

Using their technology for pores of 200 to 600 nm in diameter, scientists can create different designs with different colors, such as corrected waveguides.

Intonti said that 'an optical circuit needs more or less similar components than an electronic circuit: for example, wave paths, filters, amplifiers, switches, .' ' 'With this technique, you can recognize a large number of devices: the simplest word - for example, a point failure can act as a micro-hole (1 micrometer = 10-6 m). , or a sugar failure that acts as a wave path - to complex devices such as drip filters, optical switches, and low-threshold lasers. Indeed, besides liquids with large refractive indexes, with this technique you can absorb a local light source - for example, a mixture of quantum spots of colloids or liquid crystals to regulate adjust outside the refractive index. '

The scientists also suggested that, in addition to optics, this permeability technique could be applied to sensor chips by using a liquid that changes its optical properties according to the biological or gas morphology. .

Quote: Intonti, Francesca, with colleagues. 'Light quantum circuits can be recorded.' Applied Physics articles 89, 211117 (2006).

Thanh Van