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The future of semiconductor manufacturing

Through photonic integration

Recently the researchers from the University of Sydney developed a compact photonic semiconductor chip by heterogeneous material integration methods which integrates an active electro-optic (E-O) modulator and photodetectors in a single chip. The chip functions as a photonic circuit (PIC) offering a 15 gigahertz of tunable frequencies with a spectral resolution of only 37 MHz and is able to expand the radio frequency bandwidth (RF) to precisely control the information flowing within the chip with the help of advanced photonic filter controls.

The application of this technology extends to various fields:

• Advanced Radar: The chip's expanded radio-frequency bandwidth could significantly enhance the precision and capabilities of radar systems.

• Satellite Systems: Improved radio-frequency performance would contribute to more efficient communication and data transmission in satellite systems.

• Wireless Networks: The chip has the potential to advance the speed and efficiency of wireless communication networks.

• 6G and 7G Telecommunications: This technology may play a crucial role in the development of future generations of telecommunications networks.

Microwave Photonics (MWP) is a field that combines microwave and optical technologies to provide enhanced functionalities and capabilities. It involves the generation, processing, and distribution of microwave signals using photonic techniques.

An MWP filter is a component used in microwave photonics systems to selectively filter or manipulate certain microwave frequencies using photonic methods (see Figure 1). These filters leverage the unique properties of light and its interaction with different materials to achieve filtering effects in the microwave domain. They can be crucial in applications where precise control and manipulation of microwave signals are required.

MWP filters can take various forms, including fiber-based filters, photonic crystal filters and integrated optical filters. These filters are designed to perform functions such as wavelength filtering, frequency selection and signal conditioning in the microwave frequency range. They play a key role in improving the performance and efficiency of microwave photonics systems.

The MWP filter operates through a sophisticated integration of optical and microwave technologies as depicted in the diagram. Beginning with a laser as the optical carrier, the photonic signal is then directed to a modulator where it interacts with an input Radio-Frequency (RF) signal. The modulator dynamically influences the optical carrier's intensity, phase or frequency based on the RF input. Subsequently, the modulated signal undergoes processing to shape its spectral characteristics in a manner dictated by a dedicated processor. This shaping is pivotal for achieving the desired filtering effect. The processed optical signal is then fed into a photodiode for conversion back into an electrical signal. This conversion is based on the variations induced by the modulator on the optical carrier. The final output which is represented by the electrical signal reflects the filtered and manipulated RF signal which demonstrates the MWP's ability in leveraging both optical and microwave domains for precise and high-performance signal processing applications.

Extensive research has been conducted in the field of MWP chips, as evidenced by a thorough examination in Table 1. This table compares recent studies based on chip material type, filter type, on-chip component integration, and working bandwidth. Notably, previous studies demonstrated noteworthy advancements in chip research despite the dependence on external components. What distinguishes the new chip is its revolutionary integration of all components into a singular chip which is a significant breakthrough that sets it apart from previous attempts in the field.

Here the term "On-chip E-O" involve the integration of electro-optical components directly onto a semiconductor chip or substrate. This integration facilitates the interaction between electrical signals (electronic) and optical signals (light) within the same chip. The purpose is to enable the manipulation, modulation or processing of optical signals using electrical signals typically in the form of voltage or current control. Key components of on-chip electro-optical capabilities include:

1. Modulators which alter the characteristics of an optical signal in response to electrical input which is crucial for encoding information onto optical signals.

2. Photonic detectors convert optical signals back into electrical signals extracting information for electronic processing.

3. Waveguides guide and manipulate the propagation of light waves within the chip, routing optical signals to various components.

4. Switches routes or redirects the optical signals based on electrical control signals.

This integration enhances compactness, energy efficiency, and performance in applications such as communication systems and optical signal processing.

"FSR-free operation" refers to Free Spectral Range (FSR) which is a characteristic of optical filters and resonators. FSR is the separation in frequency between two consecutive resonant frequencies or transmission peaks. The column "FSR-free operation" indicates whether the optical processing platform operates without relying on a specific or fixed Free Spectral Range. It means that its operation is not bound or dependent on a particular FSR. This could be advantageous in scenarios where flexibility in the spectral range or the ability to operate over a range of frequencies without being constrained by a specific FSR is desired.

"On-chip MWP link improvement" refers to enhancements made directly on a semiconductor chip to optimize the performance of MWP links. These improvements aim to enhance the integration and efficiency of communication or signal processing links that involve both microwave and optical signals. The term implies advancements in key aspects such as data transfer rates, signal fidelity and overall link performance. On-chip integration brings advantages such as compactness and reduced power consumption.

The manufacturing of the photonic integrated circuit (PIC) involves partnering with semiconductor foundries overseas to produce the foundational chip wafer. This new chip technology will play a crucial role in advancing independent manufacturing capabilities. Embracing this type of chip architecture enables a nation to nurture the growth of its autonomous chip manufacturing sector by mitigating reliance on international foundries. The extensive chip delays witnessed during the 2020 COVID pandemic underscored the global realization of the chip market's significance and its potential impact on electronic manufacturing.

Written by Arun Sreeraj

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