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Failed? DMD with 760nm light source

Jinyang Liang10035
Intellectual 295 points

Hey Fizix,

We are currently using a 760nm Super-luminescent Light Emitting Diode (SLED) as a input light source to do spatial light modulation. But the experimental result was totally out of my expectation. After reflected by DMD with all pixels being turned on ("ONE"), the output beam can't maintain its shape. It is stretched out at one diagonal direction and converging in the other diagonal direction.

I am wondering if you have seen this before in your experiment using 760nm wavelength light as the input. What advices do you have? I appreciate it.

Jinyang

  • 0
    TI__Guru 54685 points

    Hello Jinyang,

    It is good to hear from you again.

    Let me ask a couple of questions, so that I can understand better:

    1.  What are the characteristics of the beam without a DMD in the path?  In other words if you simply replace the DMD with a mirror what is the shape of the beam at the same distances from a flat mirror?
    2. What is the incident and exit angle relative to the DMD for the beam when the DMD is "on"?

    I have not personally observed this in my experimentation with lasers.  I have not personally experimented with SLEDs.

    Fizix

  • 0 in reply to Fizix
    Intellectual 295 points

    Hey Fizix,

     

    Sorry for not replying your message. After several experiments and discussion with my supervisor, I got the answer:

     

    What I saw was basically the rainbow effect after you shine a broad-bandwidth light into the grating.Since our SLED has the bandwidth of about 20nm with the central wavelength of 760nm, all different wavelength is diffracted with slightly different angles. Therefore, lots of diffraction beams are overlapped with each other and couldn't be distinguished.

     

    Now we decided to replace SLED with laser diode and hopefully this will solve our problem.

     

    Thanks,

    Jinyang