From Lab to Fab: AIM Photonics Drives Innovation in Silicon Photonic Integrated Chip Testing

Abstract

Photonic integrated circuits (PICs) enable applications in communications, sensing, and computing using light. However, testing PICs poses unique challenges compared to traditional integrated circuits. This article examines the importance of PIC testing, key technical challenges, and advanced solutions offered by AIM Photonics to accelerate photonic integration from lab to manufacturing.

Introduction

Integrated photonics is a rapidly growing field with applications across telecommunications, LiDAR, biomedical devices, quantum computing, and more. Photonic integrated circuits (PICs) integrate multiple optical components onto a single chip to manipulate light instead of electricity. While integrated photonics promises compact, scalable devices, testing PICs during development and manufacturing presents distinct challenges. This article explores the critical need for PIC testing, technical barriers, and how AIM Photonics’ testing services address these challenges to progress integrated photonics technology from research to fabrication.

Importance of PIC Testing

Testing is imperative during PIC research, development, and manufacturing stages. Precise measurements validate component performance and manufacturability. However, testing photonic devices differs significantly from traditional integrated circuit testing. PICs interface with optical fibers and operate with limited power budgets. Manufacturing variations impact optical performance. Accounting for packaging and polarization effects is essential. These factors make PIC testing complex, yet crucial for technology maturation.

AIM Photonics, established as a Manufacturing Innovation Institute by the US Department of Defense, aims to enable affordable and rapid transition of integrated photonics into commercial products through design, fabrication, and testing capabilities. Its opto-electronic testing services provide researchers and developers access to advanced tools to accelerate PIC advancement from lab to manufacturing.

Technical Challenges for PIC Testing

Several key aspects make testing PICs challenging compared to electronic integrated circuits.

• Fiber Alignment: PICs require accurate alignment with optical fibers to couple light on and off chips. The small component size makes achieving sub-micron precision difficult. Automated alignment processes are needed.

• Power Limitations: Photonic circuits have stringent power budgets. Testing must avoid signal losses while providing sufficient optical power.

• Packaging Effects: Coupling PICs with external optical fibers relies heavily on packaging techniques. Testing needs to account for packaging impacts.

• Polarization Control: PIC components are optimized for certain polarization states. Testing needs precise polarization manipulation along the optical path.

• RF Signal Integrity: High frequency RF measurement requires careful calibration and de-embedding. Layout significantly impacts RF performance.

• Manufacturing Variations: Photonic circuits are subject to process variations that affect performance. Testing multiple dies provides vital statistical data.

• These factors make PIC testing substantially more complex than electronic integrated circuit testing. Developing advanced tools and techniques is necessary to enable PIC commercialization.

Figure 1. The large automated prober in AIM Photonics’ test lab enables programmable optical, DC and RF interrogation of wafer substrates as large as 300 mm, with additional flexibility for die-level testing. (Source: AIM Photonics)

AIM Photonics’ Testing Solutions

To address these challenges, AIM Photonics has invested in state-of-the-art testing infrastructure for rapid PIC prototyping and characterization.

Automated Probing: The large automated optical and RF prober enables precise wafer-scale and die-level measurements. Automated alignment enables high-throughput testing.

Tunable Lasers: Swept wavelength lasers allow testing PIC spectral performance and sensitivity.

RF Tools: Equipment for RF signal generation, analysis, and calibration supports high-frequency PIC characterization.

Passive/Active Testing: Suite of tools provides comprehensive passive optical and active optoelectronic testing capabilities.

Fiber Management: Flexible fiber couplers and precise positioners enable optimized optical coupling for testing.

In addition to tools, AIM Photonics’ technical expertise facilitates complex PIC testing from prototype evaluation to process optimization to quality assurance. By providing access to these capabilities, AIM Photonics alleviates the needs for companies to invest heavily in their own testing infrastructure. Both small and large organizations leverage these resources to accelerate PIC development.

Figure 2. This die-level edge coupler has six degrees of optimization for vertical and edge-coupler based measurements. (Source: AIM Photonics)

Conclusion

As integrated photonics progresses from lab to fabrication, comprehensive testing solutions are essential to the technology’s advancement. AIM Photonics' investment in cutting-edge photonic testing tools and expertise helps address the unique challenges of evaluating and validating integrated photonic devices. By making these capabilities accessible, AIM Photonics enables rapid PIC testing to realize integrated photonics' immense potential across communications, computing, sensing, and beyond.