A Quick Explainer on Optical Detectors: Their Types and Applications

Optical detectors or photodetectors are electronic devices which are employed to detect light. In some cases, these photo detectors can also be used to sense and measure other types of electromagnetic radiation that is incident on a specific device or circuitry. Thus, in simpler terms, optical detector or photo detectors are electromagnetic sensors that convert electromagnetic radiation into electric signals that can be measured through an appropriate device. The output electric signal thus obtained is proportional to the incident light or electromagnetic radiation.

Photo detectors have been a primary component of fiber optic communication setups along with other sectors such as healthcare, ‘smart’ electronic gadgets manufacturing sector, food production performance evaluation sector, etc. Along with this, advanced technologies like Artificial Intelligence and Internet of Things (IoT) have increased the scope of applicability of photo sensors in the last few years.

Types of Optical Detectors

The sheer range of applicability of optical detectors or photo sensors has led to the development of a diverse set of photo sensors. Some of these types are mentioned here:

• Photodiode:

Photodiode is basically a type of semiconductor device with p-n junctions that straightaway converts light energy into electric energy. A traditional solar cell is an excellent example of photodiode as it converts incident solar energy into electricity. The area of the photodiode which absorbs the light energy is known as the depletion region. Though large area photodiodes are slow at converting light energy into electric signals, the overall quantum efficiency exhibited by photodiodes is pretty high.

An electric device that is related to photodiode which is more sensitive than its regular counterpart is an avalanche photodiode. Avalanche photodiodes operate on the principle of high reverse voltage which results in effective amplification of the photocurrent.

• Metal-Semiconductor-Metal Photodetector (MSM detector):

MSM detector is a type of optical detector wherein the photodetector contains two metallic electrodes on either side of the semiconductor. Thus, instead of the p-n junction which exists in case of a photodiode, MSM detector is supplied with an electric voltage through the electrodes; these electrodes are also known as Schottky junctions. MSM detectors are much faster than photodiodes as their detection bandwidth is much higher which makes them ideal for optical fiber communications.

• Photoconductive Detector:

A photoconductive detector is essentially made up of semiconductor material which possesses photoconductive capacity. Thus, the working principle of photoconductive detector is different from a regular photodiode in which the incident light energy itself creates a disturbance in the equilibrium of electric carriers in the semiconductor material which causes a reduction in the resistance, thus resulting in a current flow. Since, photoconductive detectors are much slower than photodiodes, these optical detectors are primarily used as infrared detectors.

Applications of Optical Detectors

• Ambient Light Sensors

One of the biggest users of photo sensors is the smartphone manufacturing industry. Ambient light sensors attached at the top of the smartphone screen help in the automatic adjustment of screen brightness depending upon the incident light on the screen. This helps in battery saving and better viewing of the screen. Growing demand for smartphones worldwide is boosting the optical detector market growth.

• “Smart” Biomedical Gadgets

In the last few years, various electronic manufacturing companies have come up with different types of “smart” gadgets such as heartbeat sensors, pulse oximeters, etc. These devices are built on the principle of photoplethysmography which help in real-time monitoring of bodily functions.

• LIDAR Technology

LIDAR technology which is used to create a 3D simulation of an environment runs on highly sensitive optical detectors. A typical light detection and ranging (LIDAR) sensor emits light waves into the environment which is to be surveyed and these light waves, upon bouncing off the nearby surfaces, are received by the sensor, thereby giving a complete picture of the surveyed area.

The Bottom Line

Different types of optical detectors have been manufactured such as phototransistors, photomultipliers, etc. which have been widely used along with new-age technologies like Internet of Things. Fast and efficient detection of different types of electromagnetic radiations have made optical detectors a vital part of the electronic manufacturing industry.

About the Author(s)

Princy A. J

Princy holds a bachelor’s degree in Civil Engineering from the prestigious Tamil Nadu Dr. M.G.R. University at Chennai, India. After a successful academic record, she pursued her passion for writing. A thorough professional and enthusiastic writer, she enjoys writing on various categories and advancements in the global industries. She plays an instrumental role in writing about current updates, news, blogs, and trends.