We all know that red laser diodes are generally concentrated at 635nm and 650nm. Let's introduce the gap between them. I hope you will have a clear understanding after reading it.

The brightness difference is obvious.

Under the same optical output power, the visible brightness of 635 nm is about 2~3 times that of 650 nm.

The reason is simple: the sensitivity of human eyes to 630~640 nm is much higher than that to 650 nm.

If you want to make a 1mW red dot, 635 nm looks particularly obvious, even outdoors.

And 650 nm looks much weaker, and sometimes it is even less conspicuous during the day.

There are differences in chip technology, threshold and efficiency.

Although both belong to AlGaInP system, 635 nm needs a larger energy band because of its shorter wavelength, which is difficult to manufacture and low in yield.

In fact, there is a clear division of labor in use.

635 nm (bright) is commonly used in: guiding light of medical equipment, highlighting laser module, laser indicator (high-end), outdoor positioning, alignment, visual positioning system, stage lighting and effect light.

Especially in the medical industry, some doctors insist on 635 nm, because it is bright and can be seen under strong surgical lights.

650 nm (cheap and stable) is commonly used in: scanning module indication, optical experiment teaching, low-power laser module for general positioning, and auxiliary red dot for bar code scanning.

Wavelength stability

The temperature drift at 650 nm is more stable, while the temperature drift at 635 nm is more sensitive to temperature and driving, and the wavelength drift is larger, and it is easier to drift to long wavelength (635 → 640 → 645) with temperature rise.

Therefore, the application of 635 nm high frequency and continuous operation should pay more attention to heat dissipation and driving current stability.

These are the differences between 635nm laser diode and 650nm laser diode. I hope you will have a clear understanding after reading them.