Region Specific Enhancement of Quantum Dot Emission Using Interleaved Two-Dimensional Photonic Crystals

March 08,2016

There are a broad range of application-specific needs for lighting and display technologies, given their prevalence in our homes, workplaces and pockets. Precisely engineered control of the output spectrum of lighting products is desired to match the requirements for color temperature and output directionality, while at the same time optimizing power efficiency and manufacturing cost.

As the effects of polarization, wavelength and directionality within periodic dielectric structures are characterized, various applications continue to emerge for optical resonators using photonic crystal structures. By varying the duty cycle, period and refractive index, the resonant characteristics of a photonic crystal can be tuned to interact with wavelengths extending from the ultraviolet to the infrared. These properties have been used for a variety of applications including polarizers, filters, biosensors, optical communication components, displays and lighting.

There are a broad range of application-specific needs for lighting and display technologies, given their prevalence in our homes, workplaces and pockets. Precisely engineered control of the output spectrum of lighting products is desired to match the requirements for color temperature and output directionality, while at the same time optimizing power efficiency and manufacturing cost.

As the effects of polarization, wavelength and directionality within periodic dielectric structures are characterized, various applications continue to emerge for optical resonators using photonic crystal structures. By varying the duty cycle, period and refractive index, the resonant characteristics of a photonic crystal can be tuned to interact with wavelengths extending from the ultraviolet to the infrared. These properties have been used for a variety of applications including polarizers, filters, biosensors, optical communication components, displays and lighting.

With an appropriate choice of dielectric materials and dimensions, the resonant modes of a photonic crystal can be engineered to occur at specific combinations of angle and wavelength. This allows light of the selected wavelength and incident direction to couple to the photonic crystal and excite a highly localized electromagnetic standing wave with an amplitude that is substantially greater than the original illumination source.

Quantum dots, semiconductor nanocrystals that down-convert light from a broad band of excitation wavelengths to a very specific emission wavelength, have been successfully incorporated into photonic crystals with specific resonances designed to couple to the relevant excitation and/or emission wavelengths of the quantum dots.

In the paper, we demonstrate an approach that incorporates one or more types of quantum dots into a replica-molded flexible polymer-based photonic crystal structure that is excited by a UV backlight LED. We designed and fabricated an interleaved surface in a checkerboard pattern, containing two photonic crystal designs. While both regions are designed to produce resonances for the same UV excitation wavelength, each region is optimized for a different quantum dot emission wavelength. This is a novel device structure that allows multiple types of quantum dots to experience simultaneous enhancement in a single device structure. Such a structure can enable a customized output spectrum through control of the enhancement wavelengths and the relative surface area of each photonic crystal region.

Taken from permission from Region specific enhancement of quantum dot emission using interleaved two-dimensional photonic crystals.