# Power and Spectral Range Characteristics for Optical Power Converters

^{1}

^{2}

^{3}

^{*}

## Abstract

**:**

## 1. Introduction

_{in}< 6 W) and ‘high-power’ (P

_{in}< 50 W). Given the clear benefits of the multijunction OPC devices, they are quickly taking over their single junction predecessors in field applications requiring total galvanic and EMI isolation for power transmission. The key advancements achieved with the above OPC devices are expected to expand the deployment of power-over-fiber applications. Global research activities in the field of OPC and related photovoltaic devices continue to flourish and pave the way for further device improvements [8,9,10,11,12,13,14,15,16].

## 2. Materials and Methods

## 3. Results

_{mpp}value (the OPC’s maximum power point of the current-voltage response). Here, we classify the OPCs in three groups according to their form-factor and their related output power capabilities: regular-power, medium-power, and high-power. In this study, for regular-power we consider OPCs with P

_{mpp}< 1 W. For medium-power, we consider OPCs with P

_{mpp}up to ~ 3 W. For high-power, we consider OPCs with P

_{mpp}> 20 W.

_{in}) and the response at different temperatures (T). The results show the output voltage characteristics at the maximum power operating point (V

_{mpp}), the open circuit voltage (V

_{oc}), the output current characteristics at the maximum power operating point (I

_{mpp}), the short circuit current (I

_{sc}), and the OPCs conversion efficiency (Eff = P

_{mpp}/P

_{in}). The optimal load R

_{mpp}can also be determined using the relation R

_{mpp}= V

_{mpp}/I

_{mpp}, and corresponds to the external load for which the OPC device will operate at its maximum power point and highest efficiency. The experimental values for these parameters are extracted from the current–voltage curves measured using a Keithley 2601B sourcemeter instrument operated with a four-wire probing method. The laser power values, P

_{in}, are measured using a calibrated commercial thermopile power meter.

#### 3.1. Regular-Power, 800–830 nm Spectral Range

_{sc}and I

_{mpp}. The small current drop around a voltage of 3 V is ascribed to a small residual current mismatch at 808 nm, and similarly at 828nm as in Figure 1. For this lot, the peak response is at about 815 nm, and at the optimal wavelength, the current drop between I

_{sc}and I

_{mpp}becomes minimal. A normal distribution is observed with an average OPC conversion efficiency value of Eff ~ 61%. Other key parameters measured at the maximum power point include the current, I

_{mpp}= 115 mA, and the voltage, V

_{mpp}= 6.43 V. The open circuit voltage is V

_{oc}= 7.23 V.

_{in}~ 1.2 W, we find that the performance of the aged devices is indistinguishable from the one of the control devices. No measureable performance deviations have been observed, thus confirming the high-reliability of the OPCs devices. The robustness of the devices stems from the single semiconductor epitaxy growth which eliminates the need for added complexity in the subsequent wafer fabrication process.

#### 3.2. Medium-Power, 800–830 nm Spectral Range

_{mpp}= 4.54 W. Other key parameters measured include I

_{mpp}= 0.68 A, V

_{mpp}= 6.695 V, and V

_{oc}= 7.435 V. This gives a remarkable output voltage per subcell of 1.239 V. In other words, a very small bandgap voltage offset value of W

_{oc}= (E

_{g}/q) − V

_{oc}= 0.181 V is obtained, where E

_{g}is here the bandgap of GaAs and q is the electronic charge.

_{in}between 0.5 W and 5 W. At P

_{in}= 0.5 W, the 1J gives an efficiency of ~ 58.8% with a high fill-factor (FF) of ~ 84% at a reasonable optimal load of R

_{mpp}~ 3.4 Ohms. For input optical powers giving rise to photocurrent densities comparable to the PT6 operated at P

_{in}= 7 W, the V

_{oc}of the 1J device measured to be; V

_{oc}= 1.18 V. Therefore, the bandgap voltage offset value is ~60 mV lower for the PT6 than the 1J operated under comparable current generating conditions. More importantly, as can be seen on Figure 2, the maximum power point quickly recedes to lower voltages when the optical input power is increased on the 1J. This is due to resistive losses associated with the large current densities for the case of the 1J. At P

_{in}= 5 W the efficiency of the 1J has degraded to Eff = 31.8% at the small external optimal load of only 0.4 Ohm.

_{in}= 6 W, with a slope efficiency of 59.4%. As is also shown in Figure 3, very similar results are obtained with the PT12 at 808 nm (Broadcom’s AFBR-POC312A1). It is also clear from Figure 3 that the medium-power PT6 and the medium-power PT12 smoothly extend the power range of the regular-power PT6 (AFBR-POC206A1). Figure 3 also shows the results for the 980 nm optical input: the medium-power AFBR-POC306A5 is also reaching an output power of P

_{mpp}> 3 W, and is extending the power range of the regular-power AFBR-POC206A5 beyond P

_{in}~ 1.5 W.

#### 3.3. Stability and Reliability Properties

_{oc}, I

_{sc}, V

_{mpp}, I

_{mpp}, and Eff) remained the same for all the conditions and durations tested. Figure 4 shows examples of six different OPC configurations: 960–980 nm 5 V OPCs for high-powers and medium-power (curve ii and v); 808 nm OPCs for medium-power 6 V (curve iii) and 12 V (curve iv), and regular-power 6 V (curve vi). Figure 4 also shows that the medium-power OPCs can deliver ~3 W of stable electrical power when the case temperature is intentionally raised and kept at a temperature of 85 °C, as might be the case in harsh environments. Curve (iii), (iv), and (v) show the results for the options of an optical input at ~808 nm with output voltages of ~6 & 12 V and for an input at ~975 nm with ~6 V output. In addition, a practical optimal load R

_{mpp}of ~47 Ω is obtained for both the regular-power PT6 and the medium-power PT12 of Figure 4.

_{series}*I

^{2}(where R

_{series}is the parasitic series resistance from connecting wires, etc). In addition, as demonstrated above, the single junction approach reduces the optimal load to a few hundreds of mΩ for applications where high power is required. Such low load resistances are often unpractical. The latter will also be further demonstrated below in Section 3.6 for the high-power OPCs.

#### 3.4. Temperature and Output Voltage Properties

_{in}= 3 W and P

_{in}= 6 W in (a) and P

_{in}= 3 W and P

_{in}= 7 W in (b).

_{in}< 6 W, efficiencies greater than 50% are obtained for T < 90 °C. These results illustrate that, for typical operating conditions, the photon recycling effect, inherent in VEHSA based devices, contributes significantly to overall favorable spectral and temperature behaviors [20,21,22,23].

#### 3.5. Benefits of Multijunctions and Optical-to-Electrical Conversion at Higher Output Voltages

_{in}= 6 W. Results for a PT12, a PT6, and a single junction device are shown. The solid lines are obtained from the measured or projected I-V curves, as indicated in the figure caption. The small black crosses are obtained from fixed load steady-state testing, similar to the measurements described above in Figure 4 and Figure 6. For an optical input power of 6 W at 808 nm, the PT12 and PT6 both reach Eff ~ 60% at a practical optimal load values of 47.0 and 11.8 ohms, respectively. By contrast, the high-current and low-voltage outputs of the single junction device lead to an optimal impedance load of only a few hundreds of milliohms. Most electronic circuits are not designed to operate at such low values of voltage and load, resulting in high I

^{2}R

_{s}losses. In practice, it is particularly of concern with single-junction devices when considering the typical series resistance from wires and inter-connections, which can become a significant fraction of such a low optimal load value. Simply put, multijunction OPCs are more advantageous as power sources for practical applications and are clearly more advantageous to yield good efficiencies as the input power becomes larger.

^{2}). It is by far the highest output voltage reported for an optical-to-electrical conversion using a single device and with such a high output power. The previous record value for the highest output voltage was reported for a PT20 structure with a V

_{oc}> 23 V [7].

_{mpp}) for an input power of 5.5 W. Consequently, as expected the output voltage increases smoothly with increasing optical input powers, up to a maximum value of V

_{mpp}~ 35 V when the input power reaches 5.5 W. For that fixed load of 802 Ω the maximum output power reaches P

_{mpp}~ 1.5 W, yielding a conversion efficiency of 27%. Increasing the input power to values higher than 5.5 W (not shown) results in a saturation of the output voltage and a decrease in efficiency, as expected. The efficiency is relatively low for this implementation of the PT30 because it is not yet optimized and it was designed for an input wavelength near the GaAs band-edge, significantly away from the optical input of 808 nm used in the measurements of Figure 8.

_{mpp}> 0.5 W with a conversion efficiency of Eff ~ 36% at 1550 nm with an optimal load of ~ 0.3 Ohm [5]. Similar to the example shown above, we expect that devices based on the multijunction InGaAs VEHSA design would exhibit increased optimal loads and improved operating characteristics. Given the importance of the ~1550 nm wavelength range for optical communication applications, it suggests such further developments will be of key interest.

#### 3.6. High-Power Capabilites and OPCs for the 960–980 nm Spectral Range

_{mpp}vs. P

_{in}relationship is found to have negligible deviations from a linear regression (the output power is taken as P

_{mpp}). The output voltage (V

_{mpp}) remains over 4.5 V for the entire range, while the output current (I

_{mpp}) increases linearly to 5 A at slightly below P

_{in}= 50 W. The resulting optimal load decreases with the regression R

_{mpp}= 50.7/P

_{in}

^{1.026}, with P

_{in}in Watts and R

_{mpp}in Ohms.

^{2}. In addition, we observed that at these intensities there are significant margins of operation. For example, the optical input (optical spot) can be set to be under-filling the OPC’s active area by a factor of 2 without significantly affecting the measured performance. Furthermore, the optical spot has been measured to have a flat-top/Gaussian profile with peak intensity that can be 2× higher than the average beam intensity. Therefore, it confirms that the tunnel junctions in these InGaAs mutlijunction OPCs can sustain optical intensities up to 200 W/cm

^{2}[26].

## 4. Discussion

^{2}). The maturity of the GaAs material system and the multijunction design enables record conversion efficiencies (Eff = 64.9%) at record output powers (P

_{mpp}= 4.54 W) for room temperature operation (Figure 2).

_{mpp}< 1 W) and medium-power (P

_{mpp}< 3 W) power-over-fiber or optical wireless power transmission applications. In additional developments, the thickest base of the multijunction OPCs could be made even thinner by incorporating Bragg reflectors below the absorber region. Such additional developments could notch up the conversion efficiency of multijunction OPCs in the future. Clearly, additional optical measurements (e.g., detailed investigations of the index of refractions and absorption coefficients) and additional modeling (e.g., to accurately account for the impact of photon coupling and recycling) can continue to improve the understanding of the multijunction OPC devices and could further increase the champion device efficiencies.

_{in}< 6 W), the PT6 and the PT12 have very similar performance over the entire operating range, with a temperature coefficient of only ΔEff/ΔT ~ −0.14abs%/°C. The main difference between the two OPCs is that the PT12 has the advantage of offering an optimal load R

_{mpp}about 4× larger because it runs at about ½ the output current and 2x the output voltage (as seen in Figure 5, Figure 6 and Figure 7). For the chosen design, the performance peaks at a device operating temperature of T

_{case}~ −20 °C, but we expect this could be shifted to higher temperatures by adjusting the details of the design parameters.

_{mpp}> 0.5 W support that the future multijunction 1550 nm OPCs can have very attractive performance and a much improved optimal load compared to the R

_{mpp}~ 0.3 Ohm obtained with the single junction devices.

## 5. Conclusions

_{mpp}= 40 W. We have shown the various options currently available and the ongoing device developments for the 800–830 nm, 960–990 nm, and 1500–1600 nm spectral ranges. These high-efficiency multi-junction designs enable practical optimal loads and tailored output voltages.

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

- Matsuura, M.; Nomoto, H.; Mamiya, H.; Higuchi, T.; Masson, D.; Fafard, S. Over 40-W Electric Power and Optical Data Transmission Using an Optical Fiber. IEEE Trans. Power Electron.
**2020**, 36, 4532. [Google Scholar] [CrossRef] - Helmers, H.; Armbruster, C.; von Ravenstein, M.; Derix, D.; Schöner, C. 6-W Optical Power Link with Integrated Optical Data Transmission. IEEE Trans. Power Electron.
**2020**, 35, 7904. [Google Scholar] [CrossRef] - Jaffe, P.; Jenkins, P.; Nugent, T. Energy Transmitted by Laser in ‘Historic’ Power-Beaming Demonstration. Available online: https://youtu.be/Xb9THqrXd4I (accessed on 22 October 2019).
- Wilkins, M.; Ishigaki, M.; Provost, P.-O.; Masson, D.; Fafard, S.; Valdivia, C.E.; Dede, E.M.; Hinzer, K. Ripple-free boost-mode power supply using photonic power conversion. IEEE Trans. Power Electron.
**2018**, 34, 1054. [Google Scholar] [CrossRef] - Fafard, S.; Masson, D.; Werthen, J.G.; Ono, M.; Liu, J.; Wu, T.C.; Hundsberger, C.; Schwarzfischer, M.; Steinle, G.; Gaertner, C.; et al. Photovoltaic power converters and application to optical power transmission. In Proceedings of the 2nd Optical Wireless and Fiber Power Transmission Conference (OWPT2021), Yokohama, Japan, 21–23 April 2021. [Google Scholar]
- Fafard, S.; York, M.C.; Proulx, F.; Valdivia, C.E.; Wilkins, M.M.; Arès, R.; Aimez, V.; Hinzer, K.; Masson, D.P. Ultrahigh efficiencies in vertical epitaxial heterostructure architectures. Appl. Phys. Lett.
**2016**, 108, 071101. [Google Scholar] [CrossRef] - Fafard, S.; Proulx, F.; York, M.C.; Richard, L.S.; Provost, P.O.; Arès, R.; Aimez, V.; Masson, D.P. High-photovoltage GaAs vertical epitaxial monolithic heterostructures with 20 thin p/n junctions and a conversion efficiency of 60%. Appl. Phys. Lett.
**2016**, 109, 131107. [Google Scholar] [CrossRef] - Helmers, H.; Lopez, E.; Höhn, O.; Lackner, D.; Schön, J.; Schauerte, M.; Schachtner, M.; Dimroth, F.; Bett, A.W. 68.9% Efficient GaAs-Based Photonic Power Conversion Enabled by Photon Recycling and Optical Resonance. Phys. Status Solidi (RRL) Rapid Res. Lett.
**2021**, 15, 2100113. [Google Scholar] [CrossRef] - France, R.M.; Buencuerpo, J.; Bradsby, M.; Geisz, J.F.; Sun, Y.; Dhingra, P.; Lee, M.L.; Steiner, M.A. Graded buffer Bragg reflectors with high reflectivity and transparency for metamorphic optoelectronics. J. Appl. Phys.
**2021**, 129, 173102. [Google Scholar] [CrossRef] - Beattie, M.N.; Valdivia, C.E.; Wilkins, M.M.; Zamiri, M.; Kaller, K.L.C.; Tam, M.C.; Kim, H.S.; Krich, J.J.; Wasilewski, Z.R.; Hinzer, K. High current density tunnel diodes for multi-junction photovoltaic devices on InP substrates. Appl. Phys. Lett.
**2021**, 118, 062101. [Google Scholar] [CrossRef] - Wagner, L.; Reichmuth, S.K.; Philipps, S.P.; Oliva, E.; Bett, A.W.; Helmers, H. Integrated series/parallel connection for photovoltaic laser power converters with optimized current matching. Prog. Photovolt. Res. Appl.
**2020**, 29, 172. [Google Scholar] [CrossRef] - Panchak, A.; Khvostikov, V.; Pokrovskiy, P. AlGaAs gradient waveguides for vertical p/n junction GaAs laser power converters. Opt. Laser Technol.
**2021**, 136, 106735. [Google Scholar] [CrossRef] - Lin, M.; Sha, W.E.I.; Zhong, W.; Xu, D. Intrinsic losses in photovoltaic laser power converters. Appl. Phys. Lett.
**2021**, 118, 104103. [Google Scholar] [CrossRef] - Zhao, Y.; Li, S.; Ren, H.; Li, S.; Han, P. Energy band adjustment of 808 nm GaAs laser power converters via gradient doping. J. Semicond.
**2021**, 42, 032701. [Google Scholar] [CrossRef] - Nouri, N.; Valdivia, C.E.; Beattie, M.N.; Zamiri, M.S.; Krich, J.J.; Hinzer, K. Ultrathin monochromatic photonic power converters with nanostructured back mirror for light trapping of 1310-nm laser illumination. In Physics, Simulation, and Photonic Engineering of Photovoltaic Devices X; International Society for Optics and Photonics: Bellingham, WA, USA; Volume 116810X.
- Komuro, Y.; Honda, S.; Kurooka, K.; Warigaya, R.; Tanaka, F.; Uchida, S. A 43.0% efficient GaInP photonic power converter with a distributed Bragg reflector under high-power 638 nm laser irradiation of 17 W cm
^{−2}. Appl. Phys. Express**2021**, 14, 052002. [Google Scholar] [CrossRef] - Masson, D.; Proulx, F.; Fafard, S. Pushing the limits of concentrated photovoltaic solar cell tunnel junctions in novel high-efficiency GaAs phototransducers based on a vertical epitaxial heterostructure architecture. Prog. Photovolt. Res. Appl.
**2015**, 23, 1687. [Google Scholar] [CrossRef] [Green Version] - Fafard, S.; Masson, D.P. Transducer to Convert Optical Energy to Electrical Energy. U.S. Patent 9,673,343, 6 June 2017. [Google Scholar]
- Fafard, S.; York, M.C.A.; Proulx, F.; Wilkins, M.; Valdivia, C.E.; Bajcsy, M.; Ban, D.; Arès, R.; Aimez, V.; Hinzer, K.; et al. Ultra-efficient N-junction photovoltaic cells with Voc > 14 V at high optical input powers, PVSC 2016. In Proceedings of the IEEE 43rd Photovoltaic Specialists Conference, Portland, OR, USA, 5–10 June 2016; p. 2374. [Google Scholar]
- Proulx, F.; York, M.C.A.; Provost, P.O.; Arès, R.; Aimez, V.; Masson, D.P.; Fafard, S. Measurement of strong photon recycling in ultra-thin GaAs n/p junctions monolithically integrated in high-photovoltage vertical epitaxial heterostructure architectures with conversion efficiencies exceeding 60%. Phys. Status Solidi RRL
**2017**, 11, 1600385. [Google Scholar] [CrossRef] - Wilkins, M.; Valdivia, C.E.; Gabr, A.M.; Masson, D.; Fafard, S.; Hinzer, K. Luminescent coupling in planar opto-electronic devices. J. Appl. Phys.
**2015**, 118, 143102. [Google Scholar] [CrossRef] [Green Version] - Lopez, E.; Höhn, O.; Schauerte, M.; Lackner, D.; Schachtner, M.; Reichmuth, S.K.; Helmers, H. Experimental coupling process efficiency and benefits of back surface reflectors in photovoltaic multi-junction photonic power converters. Prog. Photovolt. Res. Appl.
**2021**, 29, 461. [Google Scholar] [CrossRef] - Xia, D.; Krich, J.J. Efficiency increase in multijunction monochromatic photovoltaic devices due to luminescent coupling. J. Appl. Phys.
**2020**, 128, 013101. [Google Scholar] [CrossRef] - Kimovec, R.; Helmers, H.; Bett, A.W.; Topič, M. Comprehensive electrical loss analysis of monolithic interconnected multi-segment laser power converters. Prog. Photovolt. Res. Appl.
**2019**, 27, 199. [Google Scholar] [CrossRef] - Kimovec, R.; Helmers, H.; Bett, A.W.; Topič, M. On the Influence of the Photo-Induced Leakage Current in Monolithically Interconnected Modules. IEEE J. Photovolt.
**2018**, 8, 541–546. [Google Scholar] [CrossRef] - Fafard, S.; Masson, D.P. Transducer to Convert Optical Energy to Electrical Energy. U.S. Patent 10,158,037, 18 December 2018. [Google Scholar]
- Yamagata, Y.; Yamada, Y.; Kaifuchi, Y.; Nogawa, R.; Morohashi, R.; Yamaguchi, M. Performance and reliability of high power, high brightness 8xx-9xx nm semiconductor laser diodes. In Proceedings of the 2015 IEEE High Power Diode Lasers and Systems Conference (HPD), Coventry, UK, 14–15 October 2015; pp. 7–8. [Google Scholar] [CrossRef]

**Figure 1.**Performance of regular-power PT6 from a group of over 3000 devices (Broadcom’s AFBR-POC206A1). Measured at room temperature (T ~ 23 °C) with an input power of 1.2 W at 828 nm. The chip area is 0.03 cm

^{2}, giving an average optical input intensity of 37 W/cm

^{2}at 1.2 W. Histogram and statistics are shown in the insets. The density plot of all the current-voltage (I-V) curves is traced using a rainbow color scheme (cold colors correspond to lower occurrence points and hot colors correspond to higher occurrence points).

**Figure 2.**Power–voltage results of Broadcom’s medium-power PT6 chips measured at an optical input power of P

_{in}= 7 W at 808 nm (blue curve). The chip area is 0.14 cm

^{2}, giving an average optical intensity of 48 W/cm

^{2}at 7 W. The multiple curves near 1 V are obtained with a single junction GaAs OPC measured with an optical input power between 0.5 W (black curve with Eff = 58.8%) and 5.0 W (red curve with Eff = 31.8%).

**Figure 3.**OPCs’ output power vs. optical input power curves for the regular-power (AFBR-POC206A1 and AFBR-POC206A5) and medium-power (AFBR-POC306A1, AFBR-POC312A1, and AFBR-POC306A5). The “A1” and “A5” devices are designed for, and measured at, an optical input wavelength of ~808 nm and ~975 nm respectively.

**Figure 4.**Stability measurement, in DC steady-state operation, of Broadcom’s photovoltaic OPCs covering various power, voltage, and spectral range options. The test conditions are indicated on the plot, where T

_{case}is the measured case temperature and R

_{load}is the fixed output resistor used. The high-power AFBR-POC506A5 OPCs have an area of 1 cm

^{2}, giving an average optical input intensity of 45 W/cm

^{2}at 45 W.

**Figure 5.**Temperature dependence of the output power for the medium-power OPCs for spectral range option of 800–830 nm in (

**a**), and for 960–990 nm in (

**b**). Test details are indicated on the plot. The average optical intensities are 20.8, 41.6, and 48.5 W/cm

^{2}for the P

_{in}of 3 W, 6 W, and 7 W respectively.

**Figure 6.**Measured temperature behavior for medium-power PT6 and PT12 OPC devices at λ

_{in}~ 808 nm. At P

_{in}= 6 W (average optical intensity of 41.6 W/cm

^{2}), output powers greater than 3 W are obtained for T < 90 °C. The temperature coefficients are extracted from a linear fit to the measured data. The test conditions and linear regression results are indicated on the plot. Inset: picture of the medium-power OPCs.

**Figure 7.**Performance vs. output load resistance for medium-power OPCs for P

_{in}= 6 W (average optical intensity of 41.6 W/cm

^{2}) for a PT12, a PT6, and a single junction device. Solid lines from I-V curves and crosses are from fixed-load testing.

**Figure 8.**Regular-power PT30 (Broadcom’s AFBR-POC230A1) in pulsed mode at 808 nm with duty-factor of DF = 5% in a fixed external load of 802 Ohms. The device area is 0.03 cm

^{2}, giving an averaged optical intensity of 170 W/cm

^{2}at 5.5 W.

**Figure 9.**Input power dependence of the key performance parameters of the high-power PT6 OPC (Broadcom’s AFBR-POC506A5) at an input laser wavelength of ~ 977 nm at T = 23 °C. The results for a 1J InGaAs OPC measured at 977 nm are also shown for comparison (orange curves). The OPCs’ active areas are 1 cm

^{2}in all cases.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. |

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Fafard, S.; Masson, D.; Werthen, J.-G.; Liu, J.; Wu, T.-C.; Hundsberger, C.; Schwarzfischer, M.; Steinle, G.; Gaertner, C.; Piemonte, C.;
et al. Power and Spectral Range Characteristics for Optical Power Converters. *Energies* **2021**, *14*, 4395.
https://doi.org/10.3390/en14154395

**AMA Style**

Fafard S, Masson D, Werthen J-G, Liu J, Wu T-C, Hundsberger C, Schwarzfischer M, Steinle G, Gaertner C, Piemonte C,
et al. Power and Spectral Range Characteristics for Optical Power Converters. *Energies*. 2021; 14(15):4395.
https://doi.org/10.3390/en14154395

**Chicago/Turabian Style**

Fafard, Simon, Denis Masson, Jan-Gustav Werthen, James Liu, Ta-Chung Wu, Christian Hundsberger, Markus Schwarzfischer, Gunther Steinle, Christian Gaertner, Claudio Piemonte,
and et al. 2021. "Power and Spectral Range Characteristics for Optical Power Converters" *Energies* 14, no. 15: 4395.
https://doi.org/10.3390/en14154395