High-Efficiency Photonic Power Converters for Telecommunications

By Muhammad OsamaReviewed by Louis CastelJul 23 2025

A recent study published in the journal Cell Reports Physical Science introduced a multi-junction photonic power converter (PPC) that achieved an energy conversion efficiency of over 50% under 1.446 μm short-wavelength infrared (SWIR) laser light. Designed with indium gallium arsenide phosphide (InGaAsP) absorber layers, this device addressed key challenges in power-by-light systems designed for optical fiber transmission, representing a significant advancement for telecommunications.

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Functionality and Applications of PPCs

PPCs, also known as laser power converters, are photovoltaic devices that convert monochromatic laser light into electrical energy, enabling efficient transmission of electrical power through optical fibers. These devices are typically used in aerospace, remote sensing, battery charging, biomedical implants, and 5G telecommunications.

Leveraging III-V semiconductor multi-junction architectures, PPCs utilize stacked p-n junctions connected by tunnel diodes to achieve higher output voltages. They are tuned to the 1.3-1.6 μm range, which corresponds to the low-loss window of silica optical fibers. Achieving high efficiency and sufficient voltage output at room temperature remains a challenge. Single-junction PPCs made with InGaAsP have reached about 52.8% efficiency, but multi-junction designs face issues with current matching and material compatibility.

Modeling and Fabrication Techniques

Researchers developed a calibrated optoelectronic model to simulate the performance of PPC. This model incorporated key physical effects, including luminescent coupling, optical interference, and realistic charge transport. The optical behavior was simulated using rigorous coupled-wave analysis (RCWA), while electrical performance was modeled through a drift-diffusion approach. Together, these methods provided a comprehensive framework for accurately predicting current-voltage characteristics under monochromatic laser illumination.

To validate the model, two PPCs were built: a 10-junction device for 1.52 μm operation and a four-junction device with InGaAsP absorbers for 1.446 μm, both lattice-matched to indium phosphide substrates and grown using metal-organic vapor phase epitaxy (MOVPE). The 10-junction device was initially designed based on uniform absorption assumptions but needed adjustments due to growth-rate variations that affected layer thicknesses.

To determine layer thicknesses, the study used two methods: a non-destructive reverse-bias technique and cross-sectional scanning electron microscopy (XSEM). In the reverse-bias method, the device was tested with a mismatched wavelength, resulting in current steps that reflected the individual junction photocurrents. These values were used to estimate layer thicknesses with an error of less than 5% and were confirmed by XSEM measurements.

The devices featured tunnel diodes between junctions, optimized antireflection coatings, and metallic gridlines optimized to minimize shading and resistive losses. They were tested using calibrated lasers at specific wavelengths, with input power measured by thermopile sensors and neutral density filters while maintaining a temperature of 25°C. A four-wire setup was used to ensure accurate current-voltage measurements across different irradiance levels.

Achieving High Efficiency in SWIR

The 10-junction InGaAs PPC showed a peak efficiency of 46.4% ± 1.1% at an irradiance of 35 W/cm² under 1.52 μm laser light, with an output voltage of 5.01 V at maximum power and an open-circuit voltage of 5.78 V. The experimental findings closely aligned with the calibrated optoelectronic model, validating the design approach. Efficiency losses were linked to current mismatch and excess radiative recombination in thicker junctions.

To optimize performance, researchers adjusted absorber layer thicknesses, enhancing luminescent coupling and reducing photon escape. This resulted in a 0.25% relative increase in efficiency and a 0.2% boost in output voltage. Further simulations indicated that increasing the Shockley-Read-Hall lifetime from 0.11 μs to 3 μs could raise efficiency to 57% at 10 W/cm² irradiance. The study also explored PPC design across wavelengths from 1.0 to 1.6 μm, finding efficiency increases with absorber bandgap, reaching 67%. Devices with five or more junctions achieved flatter efficiency profiles and output voltages above 5 V.

A four-junction InGaAsP PPC optimized for 1.48 μm light achieved an average efficiency of 53.3% at 15.1 W/cm², with the best performance reaching 53.6% ± 1.3% and 2.18 V output at 1.446 μm. Overall, this device maintained high efficiency despite minor wavelength shifts, thereby confirming its robustness for practical applications.

Implications for Telecommunications and Power Transmission

These advancements in PPC efficiency and voltage output are valuable for integrating power-by-light systems into telecommunication infrastructure. Transmitting both power and data over a single optical fiber in the 1.3-1.6 μm range supports reliable remote powering of sensors and 5G components. Longer-wavelength PPCs demonstrated better performance over fiber distances exceeding 0.43 km, simplifying long-haul systems.

PPCs are suitable for industrial applications requiring galvanic isolation and immunity to electromagnetic interference. Their high-voltage output supports a wide range of devices, reducing the need for extra power conversion. The non-destructive layer thickness technique and predictive modeling framework facilitate scalable manufacturing and practical use.

Conclusion and Future Directions

This research demonstrated that PPCs can achieve over 50% efficiency at room temperature in the SWIR range. It established a framework for designing, modeling, and fabricating high-efficiency multi-junction PPCs, supported by a validated optoelectronic model, precise epitaxial growth, and a non-destructive thickness measurement technique.

Future work should focus on reducing shading losses through transparent front contacts, improving thermal management, and incorporating light-trapping structures to limit recombination and lower fabrication costs. Additionally, integrating machine learning (ML) with the predictive model could accelerate design optimization by balancing efficiency, complexity, and robustness. Overall, this research represents a key step toward commercially viable PPCs for power-by-light systems, enabling more compact, efficient, and reliable optical power transmission in telecommunications and beyond.

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