Photonic Integrated Circuit Characterization

June 27, 2023

Cadence PCB Solutions

Key Takeaways

Photonic integrated circuit characterization analyzes the optical performance of the photonic integrated circuit components inside the chip.
Amplified Spontaneous Emission (ASE) can be employed for the characterization of photonic integrated circuits.
Thermal imaging is the diagnostic tool for thermally investigating photonic integrated circuits.

After fabrication, photonic integrated circuit characterization is very important to ensure the chip is working as intended and meets the specifications

Progress in the field of photonics has led to the extensive use of photonic integrated circuits. The photonic integrated circuits are fabricated on semiconductor materials to form various components such as amplifiers, polarizers, photodetectors, modulators, etc. After fabrication, photonic integrated circuit characterization is very important to ensure the chip is working as intended and meets the specifications. Let’s read more to understand the fabrication of photonic integrated circuits and their characterization.

Developments in Photonic Integrated Circuits

There is a plethora of work going on in the area of photonics, as their applications are booming. The research, design, and manufacturing of photonic integrated circuits are ever-increasing both in their complexity as well as technology.

Photonic integrated circuits are based on the ‘more than Moore’s’ law, and the complexity of fabrication and manufacturing poses many challenges – both optical and electrical. It is important to test and characterize photonic integrated circuits to solve issues in fabrication.

The testing and characterization of the photonic integrated circuits use cutting-edge tool sets and methods. The accuracy of the tools and characterization is essential, as the reliability delivered by the photonic integrated circuit is dependent on it. The efficiency of the photonic integrated circuit development and manufacturing is based partly on testing and characterization.

Photonic Integrated Circuit Advantages

Analyze	Failure analysis Analyzes the optical performance of the photonic integrated circuit components inside the chip
Improve	Helps improve thermal management of photonic integrated circuits by identifying steps
Extract	Extracts the optical parameters of the photonic integrated circuit component Extracts the physical parameters of the wafer material of the photonic integrated circuits
Map	Maps the optical power distribution of the photonic integrated circuits
Quantify	Quantifies the losses and efficiencies related to the photonic integrated circuit components, such as waveguide splitters and couplers Quantifies the optical fiber-coupling losses in the photonic integrated circuits at the input and output
Identify	Identifies the defects or failures of the PIC or PIC wafer
Measure	Measures the optical gain, optical coupling losses, optical absorption, optical splitting loss, optical efficiency, optical interference ratios, polarization-dependent gain, optical feedback, internal optical power distributions, differential efficiency, performance non-linearities of the photonic integrated circuit and its components
Check	Checks the compatibility of the mixed combination of photonic and electronic integrated circuits

Photonic Integrated Circuit Characterization Using Spontaneous Emission

Amplified Spontaneous Emission (ASE) can be employed for the characterization of photonic integrated circuits. In this method, the photonic integrated circuit can utilize one element (first element) in the chip to characterize another component or second element in the same chip.

The optical signal from the first element is applied to the second element, which in turn modifies the temperature profile of the latter. The spontaneous radiation generated by the first element serves as the optical signal for characterizing the second element.

The temperature profile of the second element can be varied by modulating the optical signal to it. Thermo reflectance imaging can be employed for obtaining the temperature profile of the second element. From the temperature profile obtained, the second element can be characterized.

Characterization Parameters

The characterization of the second element may include determining the performance metrics, identifying the defects or failures, quantifying the thermal and optical properties or parameters, identifying hot spots, mapping the optical power distribution within the element, determining the optical cooling effects, etc.

An Example of Photonic Integrated Circuit Thermal Characterization

Thermal imaging is the diagnostic tool for thermally investigating photonic integrated circuits. Let's see an example of photonic integrated circuits characterization.

In photonic integrated circuits, cascaded semiconductor amplifiers can be characterized using amplified spontaneous emission. Thermal modulation input is given to one amplifier using the spontaneous emission from another amplifier.

The flaws present in the cascaded amplifier can be achieved by thermal imaging of the amplifier where thermal modulation input was given. Usually, thermoreflectance microscopy is employed for high-resolution thermal images of the PIC under test.

For mapping the optical power distribution throughout the various photonic integrated circuit components or to characterize the same components optically, thermal imaging can be used along with a total energy balance model.

Advantages

ASE-based photonic integrated circuit characterization can help designers investigate the chip at the wafer level. If the photonic integrated circuit is characterized at the wafer level using thermal imaging before packaging and fiber-coupling, there is a huge reduction in the manufacturing cost.

Cadence software offers you an integrated electronic/photonic design automation (EPDA) environment where you can design and characterize your photonic integrated circuits. The EPDA environment offers design, simulation, and analysis tools that help to manage complex designs and improve productivity with efficient photonics design workflows.

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