Developing nanocavities for enhancing nanoscale lasers and LEDs

As humanity enters a new era of computing, new small tools are needed to enhance the interaction between photons and electrons, and integrate electrical and photon functions at the nanoscale. Researchers have created a novel III-V semiconductor nanocavity that can limit light below the so-called diffraction limit, which is an important step towards achieving this goal.

In the journal Optical Materials Letters, researchers have demonstrated that the modal volume of their new nanocavity is one order of magnitude lower than previously shown in III-V group materials. III-V group semiconductors have unique characteristics that make them suitable for optoelectronic devices.

The significant spatial limitation of light demonstrated in this work improves the interaction between light and matter, allowing for greater LED power, lower laser threshold, and higher single photon efficiency.

The study was conducted by scientists from the Nanophotonics Center at the Technical University of Denmark. Their goal is to study a new type of dielectric optical cavity that allows for deep subwavelength optical confinement by using the concept they call extreme dielectric confinement.

EDC cavities may generate extremely efficient computers, where deep subwavelength lasers and photodetectors are integrated into transistors to reduce energy consumption by improving the interaction between light and matter.

In current research, the EDC cavity in III-V semiconductor indium phosphide was initially constructed by researchers using an orderly mathematical technique that relaxed geometric constraints and optimized the topology. Then, they used dry etching and electron beam lithography to construct the structure.

"The characteristic size of EDC nanocavities is as small as a few nanometers, which is crucial for achieving extreme light concentrations, but they also have significant sensitivity to manufacturing changes. We attribute the successful implementation of cavities to the improved accuracy of the InP manufacturing platform, which is based on electron beam lithography followed by dry etching," Xiong added.

The second stage of topology optimization is based on the relatively small dielectric feature size achieved by researchers through improved manufacturing methods. After the last optimization cycle, the mode volume of the nanocavity is only 0.26 ³， Among them λ  Is the wavelength of light, and n is its refractive index.

This achievement is four times smaller than the diffraction limit volume of the commonly referred to nanocavity, which is equivalent to a lightbox with a side length of half the wavelength.

Researchers have pointed out that although silicon has recently produced cavities with similar characteristics, III-V group semiconductors have direct band to band transitions, while silicon does not. These transformations are necessary for utilizing Purcell enhancement provided by nanocavities.

Xiong concluded, "Prior to our work, it was uncertain whether III-V group semiconductors would achieve similar results as they did not benefit from advanced manufacturing technologies developed for the silicon electronics industry.".

Currently, researchers are attempting to further reduce pattern volume by improving manufacturing accuracy. In order to manufacture useful nanolasers or nanoLEDs, they also hope to use EDC cavities.

Source: Laser Net