Medium wave infrared photodetectorMWIR is an infrared detector that operates in the 3-5 μ m wavelength range. Its core principle is based on the photoelectric effect and thermoelectric effect, which can convert the infrared radiation emitted by the target object into measurable electrical signals. It has high sensitivity, high resolution, and day night working ability, and is widely used in military, security, industrial, environmental monitoring and other fields.
Medium wave infrared photodetectorThe working principle of is mainly based on the photoelectric effect and thermoelectric effect:
Photoelectric effect: When MWIR photons (wavelength 3-5 μ m) emitted by the target object are irradiated onto the detector material (such as indium antimonide InSb, mercury cadmium telluride HgCdTe), the photon energy is absorbed by the material. If the photon energy is greater than the bandgap width of the material, electrons in the material transition from the valence band to the conduction band, forming electron hole pairs (carriers). These charge carriers move directionally under the action of the electric field inside the detector, forming a photocurrent. By measuring the magnitude of photocurrent, the number of emitted photons can be pushed back to obtain the infrared radiation intensity of the target object.
Thermoelectric effect: After the detector material absorbs infrared radiation, the molecular vibration intensifies and the material temperature rises. The resistance of thermosensitive materials (such as vanadium oxide VO ₓ, amorphous silicon) changes with temperature (such as VO ₓ resistance decreasing with increasing temperature), and the temperature change is converted into a voltage signal through a Wheatstone bridge circuit, which is amplified to generate a thermal image.
The commonly used materials for mid wave infrared photodetectors include:
Indium antimonide (InSb): With high quantum efficiency (up to 80% for high-quality detectors), it is suitable for high response speed and high sensitivity scenarios, such as military reconnaissance and autonomous driving.
HgCdTe: By adjusting the Cd composition, the bandgap width can be flexibly adjusted, covering the 3-5 μ m band. It has high sensitivity and wide band response characteristics, and supports snapshot mode, integration mode, and other functions.
Quantum Well Detector (QWIP): Infrared detection based on quantum effects, with specific band response advantages.
Medium wave infrared photodetectors have the following performance advantages:
High sensitivity: able to respond to weak infrared radiation and capture more detailed information.
High resolution: By optimizing device structure (such as reducing pixel size to below 10 μ m) and material selection, high-resolution imaging is achieved, providing a wide field of view and high field coverage.
Day and night working ability: Medium wave infrared radiation exists both day and night, and the detector can monitor around the clock without being limited by lighting conditions.
Strong anti-interference ability: able to penetrate obstacles such as smoke, dust, and fog, and maintain stable working performance in complex environments.
Strong environmental adaptability: It can work normally under various weather conditions and is not affected by factors such as light and haze.