# International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors

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## Abstract

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## 1. Introduction

## 2. Theoretical Model for the NEP and Responsivity of PCAs

## 3. Experimental Setup

## 4. Results

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A. Measured Power and Currents

**Figure A2.**Comparison between the experimentally obtained and the calculated rectified current of PCA A and B.

## References

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**Figure 1.**Geometric layout of the finger electrode (black) structure on the photoconductive material (blue) with geometric variables as defined in the text: (

**a**) Top view (

**b**) Cross-sectional view (red lines depict the field lines across the gap).

**Figure 2.**Equivalent circuit of the receiving antenna including the incoming THz wave with power ${P}_{THz}\left(f\right)$, the antenna and the photoconductor. The value of ${U}_{THz}\left(f\right)$ is the Thevenin equivalent open-circuit voltage source, as defined in [16].

**Figure 3.**Experimental setup for the measurements. For THz power measurement, the detector was a pyroelectric device, calibrated by the PTB. For the THz current measurements, it was replaced by the PCAs.

**Figure 4.**Squared detected THz current versus measured THz power for PCA B. The fitted responsivity $S\left(f\right)$ (shown in dashed lines) was equated to Equation (10) in order to obtain the effective THz effiency ${\eta}_{THz}^{eff}$. The minimum THz power that could be measured was limited by the sensitivity of the PTB calibrated detector (1 $\mu $W).

**Figure 5.**Comparison between the calculated and experimentally obtained responsivities of (

**a**) PCA A (

**b**) PCA B. ${\eta}_{THz}^{eff}$ is assumed frequency-independent.

**Figure 6.**Comparison between the calculated (${\eta}_{THz}^{eff}$ = 0.012, ${I}_{noise}={I}_{therm}$), the ideal (with ${\eta}_{THz}^{eff}$ = 1, ${I}_{noise}={I}_{therm}$), and the experimentally obtained NEPs for PCA A and B. The figure also shows the ideal performance of PCA C.

**Table 1.**PCA parameters for calculation of responsivity and noise-equivalent power (NEP). ${I}_{noise}$ is the measured current noise of the detectors while ${I}_{therm}$ is the ideal thermal noise floor.

PCA | ${\mathit{Z}}_{\mathit{A}}\phantom{\rule{3.33333pt}{0ex}}\left(\mathsf{\Omega}\right)$ | C (fF) | ${\mathit{\eta}}_{\mathit{THz}}^{\mathit{eff}}$ | ${\mathit{\tau}}_{\mathit{rec}}$ (fs) | ${\mathit{R}}_{\mathit{PC}}$ (kΩ) | ${\mathit{P}}_{\mathit{L}}$ (mW) | ${\mathit{I}}_{\mathit{therm}}$ (pA/$\sqrt{\mathbf{Hz}}$) | ${\mathit{I}}_{\mathit{noise}}$ (pA/$\sqrt{\mathbf{Hz}}$) |
---|---|---|---|---|---|---|---|---|

A | 47.3-5i – | 3.6 | 0.012 | 530 | 16.66 | 25.3 | 0.993 | 2.59 |

119.3+30.4i | ||||||||

B | 47.3-5.0i – | 3.6 | 0.012 | 530 | 12.8 | 24.7 | 1.13 | 7.03 |

119.3+30.4i | ||||||||

C | 60.8+5.0i – | 3.6 | NA | 520 | 5.6 | 26 | 1.72 | 8.48 |

95.5+17.5i |

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## Share and Cite

**MDPI and ACS Style**

Fernandez Olvera, A.d.J.; Roggenbuck, A.; Dutzi, K.; Vieweg, N.; Lu, H.; Gossard, A.C.; Preu, S.
International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors. *Photonics* **2019**, *6*, 15.
https://doi.org/10.3390/photonics6010015

**AMA Style**

Fernandez Olvera AdJ, Roggenbuck A, Dutzi K, Vieweg N, Lu H, Gossard AC, Preu S.
International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors. *Photonics*. 2019; 6(1):15.
https://doi.org/10.3390/photonics6010015

**Chicago/Turabian Style**

Fernandez Olvera, Anuar de Jesus, Axel Roggenbuck, Katja Dutzi, Nico Vieweg, Hong Lu, Arthur C. Gossard, and Sascha Preu.
2019. "International System of Units (SI) Traceable Noise-Equivalent Power and Responsivity Characterization of Continuous Wave ErAs:InGaAs Photoconductive Terahertz Detectors" *Photonics* 6, no. 1: 15.
https://doi.org/10.3390/photonics6010015