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Oximeters measure blood oxygen using visible red LED (660 nm), near-infrared LED (940 nm), and photodiode.

An emitter converts an electrical signal into an optical signal, while a photodetector is a component that converts the received light into an electrical signal. Combining emitters and photodetectors enables optical sensing to measure various objects without touching them.
Optical sensing is used in our daily life, such as people detection at automatic doors, TV remote controllers, thermal imaging cameras which can measure body temperature without contact, and pulse oximeters which instantly measure blood oxygen levels that are indispensable for patients’ medical-condition check during home medical treatment, for which demand has rapidly increased due to the COVID-19 pandemic.
In addition, the technology is used for nondestructive testing, scratch inspection on crops, and regarding the semiconductor field, measurement through glass even in spaces that are difficult for people to enter including vacuum during the manufacturing process, as well as inspection of silicon wafers which are used as raw material for semiconductors.
The technology is also versatile and useful in a wide range of fields, such as in gas analyzers that measure the concentration of gases in the air.

Marktech’s photodiodes and LEDs can emit/receive light in wavelength band including UV, Visible, NIR, and SWIR.

Light has different characteristics for each wavelength, the optimum wavelength band must be selected according to its applications, such as the type of object to be measured. The application of short wavelength infrared (SWIR) is expected to continue to expand especially, as the technology has been applied in many fields, including optical communications, medical and healthcare fields.
Marktech’s emitters and photodetectors cover a wide range of wavelengths, including ultraviolet (UV), visible light, near-infrared (NIR), as well as SWIR, and InGaAs photodetectors (*1) have a very wide sensitivity wavelength range from 600 nm to 2,600 nm. Marktech provides light-receiving diameters from 0.1 mm to 3.0 mm, characterizing high speed and high sensitivity.

Marktech’s multi-tip product with LED emitter and InGaAs photodiode detector.

In addition, Marktech also can provide multi-emitters (*2), in which multiple dies (*3) are mounted in a single package, with our advanced packaging technology. A multi-emitter can mount multiple light-emitting and light-receiving elements, enabling light-emitting and light-receiving with a single package. Also, it can be customized to meet customers’ requirements, contributing to downsizing and space saving.

※1 InGaAs photodetector：A photodetector made from three elements: indium, gallium, and arsenic.　Wavelength bands that can be detected differs depends on the material used.　InGaAs-based photodetector are used in the wavelength band from 800 nm to 2,600 nm.
※2 Multi-emitter：Multiple dies are mounted in a single package. Photodiodes can also be combined depending on the wavelength of the emitters.
※3 Die：Chips that can be got in the manufacturing process of disc-shaped base semiconductor chip by baking a circuit pattern on a substrate and cutting it into dices. Semiconductor packages are made by attaching metal terminals and plastic covers to these chips.

A laser or LIDAR speed gun uses an infrared laser and a photodiode to determine the speed of a vehicle.

SWIR used in optical sensing has its applications in many fields including optical communications and the medical and healthcare fields. It is also used in LiDAR (*4) and is expected to be applied to autonomous driving. In addition, it is also used in wearable devices for measurements of blood oxygen saturation and blood glucose levels, expected to further increase of the demand in the future.

※4 LiDAR：Light Detection and Ranging. A technology used to determine the distance to and
shape of objects by irradiating radar. It is used in a wide range of fields, including accident prevention functions in automated driving technology, measurement of undersea topography and interplanetary distances that are difficult to physically survey, and weather observation based on the detection of water vapor and particles.