Photonic Integrated Circuits (PIC)
Photonics involves controlling light and use it for the transmission and processing of information. Photonic Integrated Circuits (PIC) is a major technology where the company is doing R&D. Photonics will become widely deployed in IIoT, computers and fiber optic telecommunications. An integrated circuit is chip containing electronic components that form a functional circuit, such as those embedded inside your smart phone, computer, and other electronic devices; a photonic integrated circuit (PIC) is a chip that contains photonic components, which are components that work with light (photons).
In an electronic chip, electron flux passes through electrical components such as resistors, inductors, transistors, and capacitors; in a photonic chip, photons pass through optical components such as waveguides (equivalent to a resistor or electrical wire), lasers (equivalent to transistors), polarizers, and phase shifters.
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PICs use a laser source to inject light that drives the components, similar to turning on a switch to inject electricity that drives electronic components. Using light instead of electricity, integrated photonic technology provides a solution to the limitations of electronics like integration and heat generation.
Current manufacture nanostructure devices and control the flow of light can be performed through technologies such as photolithography, molecular beam epitaxy, and chemical vapor deposition. The packets of light (photons) can provide an analogue of an electronic integrated chip that could perform all of the required computational processes using photons while being space and time efficient. This is known as a Photonic Integrated Circuit (PIC). The PIC devices can integrate different optical components on a single substrate. This chip should, in principle, be able to perform various optical operations, such as focusing, splitting, isolation, polarization, coupling, modulation, and detecting light.
The different optical components constituting a fully functioning PIC use light sources created by a laser. The laser can deliver a narrow-band light source to the integrated chip component. Optical fibers transport light from one end to the other for thousands of kilometers. The most common component in a PIC: is the optical waveguide that links different components on the substrate.
Input couplers efficiently couple the light from lasers or optical fibers to the optical waveguide placed on the substrate, while directional couplers control the coupling of light between two parallel optical waveguides. The ring resonator allows only a narrow band of frequency and couples two optical waveguides in opposite directions.
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Nnonlinear optical effects can be used to devise second-harmonic and third-harmonic waves. With these waves, it is be possible to perform operations between two optical beams, such as frequency doubling, differencing, and mixing. Optical modulators components can modify the light intensity based on the applied DC bias potential using the nonlinear electro-optic effects.
With the periodic arrangement of high- and low-refractive-index materials in 1D, 2D, and 3D, it is possible to reflect a certain band of frequency while allowing another band of frequency to pass. These materials known as a photonic crystal can act as both a filter and resonator in a certain periodic arrangement.
For creating optical waveguides to propagate light on chip-scale packages, high-refractive-index GaAs is used as the core and is surrounded by low-refractive-index AlGaAs. More advanced techniques have been developed to dope titanium in the lithium niobate substrate to increase its refractive index and form a core.
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Today, silica on silicon (Si-SiO2) or silicon on insulator (SOI) is used, where the silicon (high refractive index of ~3.5) was embedded within silica (lower refractive index of ~1.4). The fabrication techniques for silicon are well known and silicon was compatible with other CMOS techniques.
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The crux of the silicon waveguide lies with the high contrast of the refractive index, around a 50% difference. Prior work relied on total internal reflection to confine the energy. The total internal reflection confines the energy in the lower-refractive-index slot neighbored by the high-refractive-index slabs, inherently helping to lower losses.
Integrated Circuits
The company still designs integrated circuits for many applications. However, it expects that photonic integrated circuits will become a replacement for many new applications in robotics.
Over the years, we have observed how technology has managed to squeeze itself into a more compact and concise structure. For instance, the first computers that were made were the size of 1000 laptops which we use today. How has this been made possible? The integrated circuit is the answer to it.
Integrated Circuit (IC)
The circuits that were made previously were large and bulky, consisting of circuit components like resistor, capacitor, inductor, transistor, diodes, etc., which were connected with copper wires. This factor limited the use of the circuits to big machines. It was not possible to create small and compact appliances with these big circuits. Moreover, they were not entirely shockproof and reliable.
As it is said, necessity is the mother of all inventions. So there was a need to develop smaller size circuits with more power and safety to incorporate them into devices. Three American scientists invented transistors that simplified things to quite an extent, but the development of integrated circuits changed electronics technology’s face.
An integrated circuit or an IC is a small chip of a semiconductor material that mounts an entire circuit on itself. It is very small when compared to the standard circuits, which are made of independent circuit components. The most commonly used IC is the monolithic integrated circuit.
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Integrated Circuits or an IC is defined as a microchip on which thousands and hundreds of electrical components, such as resistors, capacitors and transistors, are fabricated. An IC functions as an oscillator, amplifier, microprocessor, timer or as computer memory.
Integrated Circuit Design
Certain logic techniques and circuit designs are used to design an integrated circuit. Following are the two categories of IC design:
- Analog Design
- Digital Design
- Mixed Design
Digital Design
ICs, when used as computer memories (such as RAM and ROM), microprocessors are designed by the digital design method. This design method ensures that the circuit density is maximum and the overall efficiency is maximum. The ICs designed using this method work with binary input data such as 0 and 1. The figure shows the steps involved in designing digital integrated circuits.
Analog Design
When ICs are used as oscillators, filters and regulators, analog design method is employed to design the integrated chip. This design method is used when the power dissipation, gain and resistance are required to be perfect.
Mixed Design
The mixed design integrates the analog and digital design principles. The mixed ICs function as Digital to Analog converters, Analog to Digital converters (D/A and A/D converters) and clock/timing ICs.
Integrated Circuit Construction
An integrated circuit is a complex layering of semiconductors, coppers, and other interconnected materials to form resistors, transistors and other components. The cut and formed combinations of these wafers are known as a die.
The semiconductor wafers that make up the ICs are fragile, and the connections between the layers very intricate. As an IC die is too small to solder and connect to, the ICs are packaged. The IC package turns the delicate and tiny die into a black chip we are familiar with.
The IC package encapsulates the integrated circuit and transforms it into a device that we can easily connect. There are many different types of packages, each having unique dimensions and mounting types as shown in the figure.
All ICs are polarized, and every pin in an IC is unique both in location and function. Integrated chips use a notch or a dot to indicate the first pin as shown in the figure below.
Once the first pin is identified, the remaining PINs increase sequentially counterclockwise direction around the chip.
Integrated Circuit Features
Construction & Packaging
An Integrated circuit is made of semiconducting materials such as silicon. The integrated chip is tiny and delicate to be handled; hence they are bonded into a set of tiny gold and aluminium wires and cast into a flat block of plastic or ceramic. The block has metal pins on the outside that leads to the wires inside. The solid block prevents overheating of the chip and keeps it cool.
Size of an IC
The size of the integrated chip varies between 1 square mm to more than 200 mm.
Integration of an IC
Integrated chips get their name because they combine different devices on the same chip. A microcontroller is an IC that incorporates a microprocessor, memory and interface all in the same device.
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Commonly Used ICs
Logic Gate ICs
Logic gate ICs are combinational circuits that provide a logical output based on different input signals. It can have two to three inputs but only one output.
Timer ICs
A Timer IC is produced with accurate timing cycles with a 100 per cent or 50 per cent duty cycle.
Operational Amplifiers
An OpAmp or an Operational Amplifier is a high gain voltage amplifier with a differential input and a single-ended output.
Voltage Regulators
A voltage regulator IC provides a constant DC output irrespective of the changes in DC input.
Frequently Asked Questions – FAQs
Monolithic IC?
What do integrated circuits do?
Why are integrated circuits important?
What is the difference between a semiconductor and an IC?
List the components of the IC.