Electrical engineers at UCLA have developed a light bending technique to convert the wavelengths of light. This way of converting light from one wavelength to another could boost the performance of optical technologies such as imaging, sensing and communication systems.
Converting wavelengths of light is crucial for many imaging and sensing technologies but the process has previously added complexity to various devices and requires intricate, bulky setups that are generally inefficient.
The team used the natural phenomenon of semiconductor surface states to augment wavelength efficiency. Surface states arise through a breakdown in atomic structure which occurs when there are not enough other atoms to which surface atoms can bind. This affects the performance of electric charges flowing through semiconductor devices as they are obstructed due to the incomplete chemical bonds.
Mona Jarrahi, professor of electrical and computer engineering at UCLA, said,
“There have been many efforts to suppress the effect of surface states in semiconductor devices without realizing they have unique electrochemical properties that could enable unprecedented device functionalities.”
Instead of trying to suppress the effect of surface states, the team explored the way the incomplete bonds created an electric field across the surface of the semiconductor and used the surface states to improve light wavelength conversion.
Electrons in a semiconductor lattice increase their state of energy when struck by incoming light, enabling them to jump around. Because the electric field created across the surface of the semiconductor accelerates the now hyperactive electrons even more, they then offload the extra energy through different optical wavelengths, thus converting them.
Because this energy offload is confined the surface of a semiconductor requiring it to be more efficient, the researchers developed a nanoantenna array that bends light which captures the photons inside the semiconductor’s shallow surface.
Deniz Turan, the study’s lead author said,
“Through this new framework, wavelength conversion happens easily and without any extra added source of energy as the incoming light crosses the field.”
When the process was integrated into an endoscopy probe, its efficiency was amplified 100-fold and the technology can be used to convert optical wavelengths from elsewhere in the electromagnetic spectrum from infrared to microwaves.
