# Waveguided Approach for Difference Frequency Generation of Broadly-Tunable Continuous-Wave Terahertz Radiation

^{1}

^{2}

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## Abstract

**:**

## Featured Application

**Trace gas sensing, local oscillator for astronomical heterodyne systems, high-accuracy spectroscopy.**

## Abstract

^{7}W/cm

^{2}), on the basis of a three-wave-mixing theoretical model.

## 1. Introduction

## 2. Theory

## 3. Experimental Results and Discussion

#### 3.1. Waveguide Characterization and Power Handling

#### 3.2. THz Generation Efficiency and Spectral Coverage

## 4. Conclusions

## Author Contributions

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Polar coordinates reference system with respect to the waveguide input facet. (

**b**) Accessible THz bandwidth for a continuous wave (CW) waveguided difference frequency generation (DFG) process in MgO-doped Lithium Niobate (LN). Different lines correspond to different guided mode radii between $4\text{}\mathsf{\mu}$m and $10\text{}\mathsf{\mu}$m.

**Figure 3.**(

**a**) Representation of the crystal plate containing the channel waveguides. (

**b**,

**c**) Transmission profiles in the z and y directions, respectively, measured for different waist displacement $\Delta x$. (

**d**,

**e**) Mode Radii at the 1/e level as a function of $\Delta x$.

**Figure 4.**(

**a**) Infrared power coupled to the guided mode as a function of the incoming power for a channel waveguide (blue) and a planar waveguide (red). (

**b**) The red curves represent the calculated nonlinear efficiency $\eta $, with (solid) and without (dashed) the contribution of the transverse-optical phonon resonance at 7.5 THz. The blue curve is an example of the experimental nonlinear efficiency obtained with two different frequency scans. The low- and the high-frequency parts of the blue trace have been obtained by scanning the A1 amplifier from 1541 to 1563.5 nm and fixing the A2 wavelength at 1575 nm and 1605 nm, respectively.

$\text{}{\mathit{r}}_{0\mathit{y}}\text{}$ | $\text{}{\mathit{r}}_{0\mathit{z}}\text{}$ | $\text{}{\mathit{n}}_{\mathit{p}\mathit{u}\mathit{m}\mathit{p}}\text{}$ | $\mathbf{\Delta}\mathit{n}\text{}$ |
---|---|---|---|

$\left(8.3\pm 0.2\right)\text{}\mathsf{\mu}\mathrm{m}$ | $\left(2.95\pm 0.27\right)\text{}\mathsf{\mu}\mathrm{m}$ | $2.13$ | $\left(4\pm 1\right)\times {10}^{-3}$ |

**Table 2.**Characteristic parameters of LN crystal [52].

$\text{}\mathit{d}\mathit{n}/\mathit{d}\mathit{T}\text{}$ | $\text{}\mathit{\alpha}$ | $\text{}\mathit{k}$ | $\text{}{\mathit{r}}_{33}\text{}$ |
---|---|---|---|

$3\times {10}^{-5}{\mathrm{K}}^{-1}$ | ${10}^{-4}{\mathrm{cm}}^{-1}$ | $5{\text{}\mathrm{Wm}}^{-1}{\mathrm{K}}^{-1}$ | $30\text{}\mathrm{pm}/\mathrm{V}$ |

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**MDPI and ACS Style**

De Regis, M.; Consolino, L.; Bartalini, S.; De Natale, P. Waveguided Approach for Difference Frequency Generation of Broadly-Tunable Continuous-Wave Terahertz Radiation. *Appl. Sci.* **2018**, *8*, 2374.
https://doi.org/10.3390/app8122374

**AMA Style**

De Regis M, Consolino L, Bartalini S, De Natale P. Waveguided Approach for Difference Frequency Generation of Broadly-Tunable Continuous-Wave Terahertz Radiation. *Applied Sciences*. 2018; 8(12):2374.
https://doi.org/10.3390/app8122374

**Chicago/Turabian Style**

De Regis, Michele, Luigi Consolino, Saverio Bartalini, and Paolo De Natale. 2018. "Waveguided Approach for Difference Frequency Generation of Broadly-Tunable Continuous-Wave Terahertz Radiation" *Applied Sciences* 8, no. 12: 2374.
https://doi.org/10.3390/app8122374