A team of scientists has developed a miniature optical device that allows independent control of the intensity and phase of light using an applied voltage. This device operates with second harmonic generation.

What is second harmonic light?

Second harmonic light is produced when photons interact with a nonlinear optical medium. As a result of this process, radiation is generated at twice the frequency of the original light, while some of the initial photons pass through the medium unchanged. The second harmonic plays a crucial role in areas of physics where light is used as an energy carrier, since the frequency of the radiation becomes critically important. Additionally, second harmonic generation is associated with the creation and application of entangled photons.

Features of the new optical component

Physicists have created an optical element controlled by an electrical signal, capable of fully and independently modulating the phase and intensity of second harmonic light. Unlike traditional passive optical components, which only store, scatter, or consume energy, the new element is active and extremely compact—measuring just 4.5 by 2 micrometers. Control is achieved by varying the applied voltage, allowing precise tuning of both the phase and amplitude of the emitted light. The research results have been published in the journal Science Advances.

Experimental results and tuning capabilities

Experimental data showed that the device’s brightness can be adjusted from its maximum value down to zero, and any phase between 0 and 360 degrees is accessible. The researchers were also able to tune the device’s nonlinear response in a range of approximately 0–30 nanometers per volt, enabling control over its sensitivity. This makes it possible to achieve both complete independence of the emission phase from the voltage and significant influence of the voltage on the phase.

Dynamic light control

With this new development, scientists have created phase and amplitude gratings that provide dynamic control over the diffraction pattern of the outgoing light. Easy switching between different modes makes the device a versatile tool for light manipulation.

Key innovation — nanostructured surface

The main achievement was the creation of a special device surface: it is covered with nanostructures featuring quantum wells and metallic nanostrips, arranged in pairs with opposite phases.

Significance for quantum optics

“For the first time, we have managed to overcome the physical limitations of existing nonlinear optical devices and offer a miniature platform that enables high-speed and high-precision optical control using only electrical signals. This technology could become a fundamental platform for active quantum optical systems, such as sources of entangled photons and quantum interference control systems,” noted Professor Jongwon Lee, the lead researcher.