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DLP6500FLQ: DLPLCR6500EVM freezes upon fs laser illumination

Thej Tumkur
Prodigy 20 points
Part Number: DLP6500FLQ

Hello,

I understand that you don't rate your DLP products for femtosecond lasers, but I wanted to know if the combination of exposure times and laser parameters are within a ballpark damage threshold. 

The laser pulses are 800 nm, 1 Khz rep rate, pulse duration ~ 40 fs and ~ 50 mW average power on the DMD. 

The problem is that the DMD freezes after only a few seconds of laser illumination. After this happens, the only thing that seems to help is to wait for a few minutes before restarting the DMD (to cool it down, I imagine). The exposure times are ~ 200 ms. Would it help to isolate the DMD from mechanical vibrations/movement during laser illumination? Based on the laser parameters given, is the peak energy high enough to lead to surface ablation and thus damage of the DMD surface? How to tell if the DMD needs to be replaced?

Thank you!

Thej

  • 0
    TI__Expert 3020 points

    Hi Thej,

    We are looking at your query. We will get back on this.

    Thanks,
    Shivakumar

  • 0 in reply to SHIVAKUMAR R
    TI__Mastermind 43090 points

    Hello Thej,

    We have little experience with fs lasers on DMDs.  The concern is that at this duration ablation might be possible.  We have not done any fs laser testing.

    The natural frequencies of the micromirrors is very much higher than terrestrial vibrations, so we do not believe that it will change anything to isolate it from vibrations, but you could try it.

    If the array is heating to the point that it stops responding, then it is very likely that some kind of damage is happening to the DMD.

    If a DMD no longer properly displays images after "recovering" or inspection with an optical microscope (compensated for ~1 mm glass) shows damage, you would likely need to replace the device.

    In terms of power, if your repetition rate is 1 kHz and the average power is 50 mW, then that would be 50 uJ per pulse.  This makes the power during each pulse 1.25 GW!!  This is uncharted territory in terms of damage.  We also do not know if multi-photon events can happen during these very high fluence levels.

    Fizix

  • 0 in reply to Fizix
    TI__Mastermind 43090 points

    Hello again Thej,

    We also want to point out that the mirrors are composed primarily of Aluminum and the reflectivity takes a dip near 830 nm.  It is already reduced a bit at 800 nm, so this is not helping your thermal absorption.

    Fizix

  • 0 in reply to Fizix
    Prodigy 20 points

    Thank you, Shivakumar and Fizix. This was very helpful.