Scientists have engineered a new type of light emitting diode (LED) which can function as versatile, manufacturing-friendly lasers.
Researchers at the Los Alamos National Laboratory reached a critical milestone by incorporating meticulously engineered colloidal quantum dots into a new type of LED containing an integrated optical resonator, which allows them to operate as optically pumped lasers.
The solution could lead to devices such as integrated photonic circuits, optical circuitry, lab-on-a-chip platforms, and wearable devices – benefiting a number of emerging fields. They can also be ‘size-tuned’ for lasing applications to produce colours not accessible with existing semiconductor laser diodes.
“Quantum dot displays and television sets are already available as commercial products. The colloidal quantum dot lasers seem to be next in line,” head of the quantum dot group at Los Alamos National Laboratory, Victor Klimov, said.
The colloidal quantum dot lasers can also be manufactured using cheaper, simpler methods than modern semiconductor laser diodes that require sophisticated, vacuum-based, layer-by-layer deposition techniques.
The Los Alamos researchers successfully resolved several challenges on the path to commercially viable colloidal quantum dot technology.
They incorporated an optical resonator directly into the LED architecture without obstructing charge-carrier flows into the quantum dot emitting layer.
Also, by carefully designing the structure of their multilayered device, they achieved good confinement of the emitted light within the ultrathin quantum dot medium on the order of 50 nanometers across. This is key to obtaining the lasing effect and, at the same time, allowing for efficient excitation of the quantum dots by the electrical current.
Presently, the Los Alamos scientists are tackling the remaining challenge, which is boosting the current density to levels sufficient for obtaining so-called ‘population inversion’ — the regime when the quantum dot active medium turns into a light