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Amazon sells really cheap laser modules (with the beam receiver included) for a couple bucks. You can audio modulate the laser and receive it by connecting the photo sensor to an audio amp. It is reasonably linear if you get the laser drive levels right. Here I had my scope connected to the photosensor and the laser connected to my sig gen with a 500Hz sine wave at .9v pk-pk with a 4.3v DC offset.
[ATTACH=full]67893[/ATTACH]
[ATTACH=full]67892[/ATTACH]
Edit: you will need a decoupling cap between the photo sensor and amp to block the DC from the laser bias (its always on, just to a different degree) and have the laser and receiver fairly stable because the change in DC offset from changes in the laser alignment will also be amplified. Since the laser will have a DC bias too, the audio input will also need a DC blocking cap.

[QUOTE="brandon7861, post: 835066, member: 53724"] Amazon sells really cheap laser modules (with the beam receiver included) for a couple bucks. You can audio modulate the laser and receive it by connecting the photo sensor to an audio amp. It is reasonably linear if you get the laser drive levels right. Here I had my scope connected to the photosensor and the laser connected to my sig gen with a 500Hz sine wave at .9v pk-pk with a 4.3v DC offset. [ATTACH type="full" alt="IMG_20240309_144206859.jpg"]67893[/ATTACH] [ATTACH type="full" alt="laser.png"]67892[/ATTACH] Edit: you will need a decoupling cap between the photo sensor and amp to block the DC from the laser bias (its always on, just to a different degree) and have the laser and receiver fairly stable because the change in DC offset from changes in the laser alignment will also be amplified. Since the laser will have a DC bias too, the audio input will also need a DC blocking cap. [/QUOTE]

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