# On-Chip 3D Printing of Polymer Waveguide-Coupled Single-Photon Emitter Based on Colloidal Quantum Dots

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## Abstract

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## 1. Introduction

## 2. Methods

#### 2.1. Experiment Setup

#### 2.2. Sample Preparation

#### 2.3. Numerical Calculation Method

## 3. Results and Discussion

#### 3.1. Numerical Results

#### 3.1.1. Guiding the Emission of a Single Dipole

#### 3.1.2. Guiding the Emission of Two Orthogonal Dipoles

#### 3.1.3. Laser Excitation Configuration

#### 3.2. Experimental Results

## 4. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) LOPA-DLW setup. (

**b**,

**c**) Illustrations of sample preparation of polymeric crossed-arc waveguide containing a single QD using the LOPA-DLW technique.

**Figure 2.**Numerical results for the propagation of the emission signal from a single electric dipole within the cross-arc waveguide structure. (

**a**) Scheme for a x-oriented dipole located on top of an arc waveguide. The emitted signal from the dipole source is routed down to four outputs. Due to the symmetry, two outputs of the same arc are equivalent; here, only output x and output y are denoted. (

**b**–

**d**) Calculated Poynting vector magnitude distributions for the case depicted in (

**a**) with the radius of the cross-section of the arc waveguide being 0.1, 0.2, and 0.4 $\mathsf{\mu}$m, respectively. Results obtained from three monitors located in the $xy$, $xz$, and $yz$ planes in the FDTD simulation region are combined for better visualization. (

**e**–

**h**) are similar to (

**a**–

**d**) but for a y-oriented dipole. (

**i**–

**l**) are similar to (

**a**–

**d**) but for a z-oriented dipole. (

**m**,

**n**) Normalized output power as a function of the cross-section radius for output x and output y, respectively. Normalized output power is calculated as the energy passing through the cross-section of the waveguide at the grass/air interface divided by the total energy emitted by the electric dipole throughout the space in all directions.

**Figure 3.**Numerical results for the propagation of the emission signal from two orthogonal electric dipoles within the crossed-arc waveguide structure. (

**a**) Scheme for a QD-based SPE represented by an incoherent sum of two orthogonal electric dipoles. (

**b**–

**d**) Calculated Poynting vector magnitude distributions for the case depicted in (

**e**) with three different orientations of the c-axis. In all three figures, $r=0.2$ $\mathsf{\mu}$m. (

**e**) Scheme for a QD-based SPE located on top of an arc waveguide. (

**f**,

**g**) Normalized output power as a function of the cross-section radius for output x and output y, respectively.

**Figure 4.**Numerical results for the propagation of the excitation laser within the crossed-arc waveguide structure. (

**a**) Scheme for the case of focusing a Gaussian beam to the leg of an arc waveguide. (

**b**–

**d**) Calculated Poynting vector magnitude distributions for the case depicted in (

**a**) with the radius of the cross-section of the arc waveguide being 0.1, 0.2, and 0.4 $\mathsf{\mu}$m, respectively. (

**e**) Normalized output power as a function of the cross-section radius. (

**f**) Calculated Poynting vector magnitude distributions along the center of the cross-section of the excited arc. $\theta $ is denoted in (

**a**).

**Figure 5.**Comparison between the fabrication of (

**a**) single-arc waveguide and (

**b**) cross-arc waveguide.

**Figure 6.**Experimental characterization results. SEM images (

**a**) side view and (

**b**) top view of the crossed-arc waveguide structure. Confocal scanning images in (

**c**) $xz$ plane and (

**d**) $xy$ plane of the crossed-arc waveguide structure containing a QD-based SPE on top. (

**e**) Antibunching curves of a QD in polymeric film before fabricating the structure (upper) and of the guided signals at the four outputs at the legs of fabricated crossed-arc structure (lower). This result is measured by the same confocal system used for fabrication (excitation and acquisition through one objective lens simultaneously).

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**MDPI and ACS Style**

Ngo, G.L.; Nguyen, L.; Hermier, J.-P.; Lai, N.D.
On-Chip 3D Printing of Polymer Waveguide-Coupled Single-Photon Emitter Based on Colloidal Quantum Dots. *Polymers* **2023**, *15*, 2201.
https://doi.org/10.3390/polym15092201

**AMA Style**

Ngo GL, Nguyen L, Hermier J-P, Lai ND.
On-Chip 3D Printing of Polymer Waveguide-Coupled Single-Photon Emitter Based on Colloidal Quantum Dots. *Polymers*. 2023; 15(9):2201.
https://doi.org/10.3390/polym15092201

**Chicago/Turabian Style**

Ngo, Gia Long, Long Nguyen, Jean-Pierre Hermier, and Ngoc Diep Lai.
2023. "On-Chip 3D Printing of Polymer Waveguide-Coupled Single-Photon Emitter Based on Colloidal Quantum Dots" *Polymers* 15, no. 9: 2201.
https://doi.org/10.3390/polym15092201