Low-power green laser pointer are easy to find in many places. But it is not necessarily easy to remove it. Laser pointers or laser pointers are probably the easiest to modify. It should be noted that the laser pointer is not a simple series connection of a laser and a battery, and usually has a simple current limiting circuit. This circuit usually includes several transistors, but some of the cheapest laser pointers have only a simple current-limiting resistor. Interestingly, expensive laser pointers are not necessarily suitable here. They have complex protection constant current circuits. These circuits will seriously affect the response speed of the laser, so please find a cheap enough red laser pointer as much as possible.
It is a pity that it is not easy to remove the laser module from my laser pointer. So I plan to put a "fake battery" in it and then pull out the power cord. I find a log stick with the same diameter as the AAA battery originally used by the laser pointer, then cut a section according to the length, cut a shallow groove along the length direction and embed the wire, make electrodes at both ends, and finally install the fake battery into the laser pointer Here, the button of the laser pointer is fixed in the open position with tape, and the power cord from the fake battery is connected to a plastic box with a drive-modulation circuit next to it.
If you are just starting to play with this, it is recommended to start with short-range communication, such as your own yard, or a range of several hundred meters. Pay attention to the whereabouts of the laser when experimenting, even very low power lasers that look "harmless". If the laser pointer shines on a distant road or airport. A moment of distraction is still in serious danger.