Lecture

Infrared Photodetectors: Quantum Well and Dot Technologies

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Description

This lecture discusses the design and functionality of Quantum Well Infrared Photodetectors (QWIPs) and Quantum Dot Infrared Photodetectors (QDIPs). The instructor explains the working principles of these devices, emphasizing the importance of electric field orientation for effective light absorption. The lecture covers the necessity of gratings for light deflection in QWIPs and the advantages of using silicon processors for readout in these systems. The instructor also highlights the ability to adjust the wavelength of maximum sensitivity by modifying the thickness of the quantum wells. Additionally, the lecture presents examples of responsivity and detectivity across various wavelengths, illustrating the commercial applications of these technologies. The discussion extends to thermal infrared detectors, comparing their performance with photonic infrared detectors, and concludes with a summary of the operational characteristics and applications of both types of infrared photodetectors, emphasizing their respective advantages and limitations in detecting infrared radiation.

Official source

Ontological neighbourhood

Electrical engineering

Photonics: Topics in photonics

Related concepts (32)

Infrared detector

An infrared detector is a detector that reacts to infrared (IR) radiation. The two main types of detectors are thermal and photonic (photodetectors). The thermal effects of the incident IR radiation can be followed through many temperature dependent phenomena. Bolometers and microbolometers are based on changes in resistance. Thermocouples and thermopiles use the thermoelectric effect. Golay cells follow thermal expansion. In IR spectrometers the pyroelectric detectors are the most widespread.

Quantum dot

Quantum dots (QDs) – also called semiconductor nanocrystals, are semiconductor particles a few nanometres in size, having optical and electronic properties that differ from those of larger particles as a result of quantum mechanics. They are a central topic in nanotechnology and materials science. When the quantum dots are illuminated by UV light, an electron in the quantum dot can be excited to a state of higher energy. In the case of a semiconducting quantum dot, this process corresponds to the transition of an electron from the valence band to the conductance band.

Thermography

Infrared thermography (IRT), thermal video and/or thermal imaging, is a process where a thermal camera captures and creates an image of an object by using infrared radiation emitted from the object in a process, which are examples of infrared imaging science. Thermographic cameras usually detect radiation in the long-infrared range of the electromagnetic spectrum (roughly 9,000–14,000 nanometers or 9–14 μm) and produce images of that radiation, called thermograms.

Photodetector

Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation. There is a wide variety of photodetectors which may be classified by mechanism of detection, such as photoelectric or photochemical effects, or by various performance metrics, such as spectral response. Semiconductor-based photodetectors typically photo detector have a p–n junction that converts light photons into current. The absorbed photons make electron–hole pairs in the depletion region.

Silicon photonics

Silicon photonics is the study and application of photonic systems which use silicon as an optical medium. The silicon is usually patterned with sub-micrometre precision, into microphotonic components. These operate in the infrared, most commonly at the 1.55 micrometre wavelength used by most fiber optic telecommunication systems. The silicon typically lies on top of a layer of silica in what (by analogy with a similar construction in microelectronics) is known as silicon on insulator (SOI).

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