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233. Using Distributed Bragg Reflectors to Improve Photon Collection from Quantum Dots

Ariel Eden Weltner, Dr. Christopher F. Schuck, Kevin D. Vallejo, Kathryn E. Sautter, Trent A. Garrett, Dr. Kevin Silverman, Dr. Galan Moody, Dr. Paul Simmonds

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Distributed Bragg reflectors (DBRs) designed to improve photon collection from GaAs quantum dots

graph, contact presenter for specific data set
Percent Reflectivity vs Wavelength. Structure 1 Peak: 1015 nm. Structure 2 Peak: 1140 nm


Quantum dots (QDs) are small islands of material that emit light (Fig. 1). When made from GaAs, these QDs are useful for devices such as LEDs and lasers. Our goal is to improve the collection efficiency of QD light, to optimize it for these devices.

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Figure 1. Emission spectra for GaAs QDs [1]. A DBR that reflects wavelengths of ~1000 nm is ideal for the majority of these QDs.


  • Synthesize DBR test structures
  • Perform optical reflectivity measurements
  • Optimize DBR for GaAs QDs


CategoryStructure 1Structure 2
InAlAs Thickness74.6383.11 nm
InGaAs Thickness68.19 nm75.63 nm
Target Peak1000 nm1100 nm
Experimental Peak1015 nm1140 nm

Two test structures were made (see Figure 2), each reflecting different light wavelengths. We need to choose the structure that best reflects the light from our QDs.

Fig. 2. A DBR is a mirror designed to reflect light of specific wavelengths. Reflected wavelength changes as a function of bilayer (BL) thickness (tA + tG).
  • Test structures contained only 6 BLs
  • The DBR will improve collection efficiency by reflecting photons that have been emitted down towards the substrate up and into a detector.


The central figure shows the peak wavelength of Structure 1 is best aligned with our QD emission wavelengths (Figure 1). Next steps include growing a full DBR structure with GaAs QDs.


  • [1] C. F. Schuck et al., J Vac Sci Technol B 36, 031803 (2018). doi: 10.1116/1.5018002

Additional Information

For questions or comments about this research, contact Ariel Weltner at