Different in structure and principle. The red and blue laser flashlight is directly output by the light from LD (laser diode) after lens shaping, with simple structure and low cost. At present, the LD module in C-MOUNT package can realize red light of 2W, but the price is very expensive, and it is easy to buy 0.5~ 1W modules in the market. Blue light can be above 5W, but it is very expensive. 1~3.5W components are easily available in the market.

Green flashlight is a green laser produced by pumping Nd:YVO 4/KTP composite crystal with infrared LD. Its structure is much more complicated than red light and blue light, and the laser crystal has a conversion efficiency (generally up to 50%~60%), which means that its pumping power needs to be higher. For example, 1W red light only needs 1W red light LD for direct output, while 1W green light needs 2W infrared LD pump. In addition, the green crystal itself has a large thermal resistance and is not easy to conduct heat and dissipate heat, which limits its power.

Of course, this is only in the handheld field. If it is a fixed laser, it can use gas and liquid circulation for forced cooling, and the power it can achieve is much larger than that of a hand-held laser pen.