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Thread: pulsed blue laser

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    Default pulsed blue laser

    hello,

    I want to get nanosecond(0.5ns--100ns) pulse from a blue laser diode(405nm/445nm), high power around watt level is preferred.


    if someone work on pulsed laser diode, can you give some advices on both laser diode module and laser driver.

    I have found Nichia NDB7875, however the modulation rising time should be longer than 2 ns.

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    Quote Originally Posted by Zhao40802 View Post
    hello,

    I want to get nanosecond(0.5ns--100ns) pulse from a blue laser diode(405nm/445nm), high power around watt level is preferred.


    if someone work on pulsed laser diode, can you give some advices on both laser diode module and laser driver.

    I have found Nichia NDB7875, however the modulation rising time should be longer than 2 ns.

    I have not yet tried with a blue LD, howeer I have used a IR VECSEL and IR and Blue LEDs.

    You perhaps have Two ways to start:

    One, Build a avalanche transistor driver with the assistance of a skilled technician or Electrical Engineer and experiment.
    Two, Contact Avtech or a similar pulser company and ask about their experience with blue diodes.

    www.avtechpulse.com Avtech is very friendly to researchers, I'm sure they will share their experience with you.

    The pulser will stretch out the rise time if needed, so will adding less then a picofarad or similar small capacitor across the diode. A series inductor is used by some to slow the pulse as well. You need to watch the dI/dT through the diode. Most LDs are remarkably fast, it is the lead length of the package that matters a great deal.

    If you must do it the experimental way:

    The page at:

    http://www.elexp.com/t_SpeedofLight.htm has a self triggering LD Avalanche laser driver circuit, which can be modified for external trigger per the Jim Williams publication. However building it on the breadboard module shown with the huge lead lengths is slowing it down. It should be built as compact as possible with low loop area in the leads. This is to reduce inductance. It should be built by hand on a very small piece of printed circuit board.

    http://www.google.com/url?sa=t&rct=j...,d.eWU&cad=rja

    See page 93 of the above Linear Technology application note 47 for the pulser. I get 750 picoseconds full half width maximum from mine driving a led. My collegue obtained 550 picoseconds with a surface mount IR laser removed from a fiber optic networking board.

    2N2369 is a good transistor for this. Diodes Inc makes Zetex 415 and 418 transistors for this as well.

    Rev. Sci. Instrum. 68, 2253 (1997) is a good paper.



    Avtech can tell you which blue LDs they have had success with.

    The Nichia Blue LDs harvested by laser hobbyists from video projectors have large dies, but seem to take high dI/dT with little problems. I'm sure some one here can chime in and offer you one or two pieces for trials.

    Good Luck,

    Steve
    Last edited by mixedgas; 02-08-2013 at 06:54.

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    steve, thanks a lot for your kind advices!

    I will contact AVTECH for informations in details.

    If someone can provide one Nichia laser module to me, it would be very nice.

    Thanks again!
    zhuang



    Quote Originally Posted by mixedgas View Post
    I have not yet tried with a blue LD, howeer I have used a IR VECSEL and IR and Blue LEDs.

    You perhaps have Two ways to start:

    One, Build a avalanche transistor driver with the assistance of a skilled technician or Electrical Engineer and experiment.
    Two, Contact Avtech or a similar pulser company and ask about their experience with blue diodes.

    www.avtechpulse.com Avtech is very friendly to researchers, I'm sure they will share their experience with you.

    The pulser will stretch out the rise time if needed, so will adding less then a picofarad or similar small capacitor across the diode. A series inductor is used by some to slow the pulse as well. You need to watch the dI/dT through the diode. Most LDs are remarkably fast, it is the lead length of the package that matters a great deal.

    If you must do it the experimental way:

    The page at:

    http://www.elexp.com/t_SpeedofLight.htm has a self triggering LD Avalanche laser driver circuit, which can be modified for external trigger per the Jim Williams publication. However building it on the breadboard module shown with the huge lead lengths is slowing it down. It should be built as compact as possible with low loop area in the leads. This is to reduce inductance. It should be built by hand on a very small piece of printed circuit board.

    http://www.google.com/url?sa=t&rct=j...,d.eWU&cad=rja

    See page 93 of the above Linear Technology application note 47 for the pulser. I get 750 picoseconds full half width maximum from mine driving a led. My collegue obtained 550 picoseconds with a surface mount IR laser removed from a fiber optic networking board.

    2N2369 is a good transistor for this. Diodes Inc makes Zetex 415 and 418 transistors for this as well.

    Rev. Sci. Instrum. 68, 2253 (1997) is a good paper.



    Avtech can tell you which blue LDs they have had success with.

    The Nichia Blue LDs harvested by laser hobbyists from video projectors have large dies, but seem to take high dI/dT with little problems. I'm sure some one here can chime in and offer you one or two pieces for trials.

    Good Luck,

    Steve

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    The triggered pulser version is in a Linear Technology Applications note, entitled, "The Taming of the Slew". Aka APP Note 94.
    A pun on Shakesphere's "The Taming of the Shrew".

    I would also buy more then 1 LD. HV pulses of this nature can be very distructive. Until you get the attenuator circuit values correct, you do tend to destroy them. IR LDs are 3$ a piece or so on Ebay, often less. IR leds are cheap as well. Blow up a bunch of both first as practice.

    Good Luck,

    Steve
    Last edited by mixedgas; 02-08-2013 at 08:19.

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    hi, Steve,

    I have contacted AVtech Enginneer.
    ¨For a pulse drving, optical peak power of 50 W. This would require ~ 50 Amps of current.¨

    For example, Nichia NDB7875(1.6 W, the maximum forwards current is 1.7 A), does it means that the forwards currnt is limitted to 1.7 A in the pulse driving condition?
    And if this current also vary with different pulse duration(from ns to us)?

    I am not familliar with the pulsing condition.

    Thank you for your kind assisstance!

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    For very short pulses, picoseconds to a few nsec you may be able to exceed the maximum current rating by a relatively small percentage. Just like we do for CW operation with an understanding that this will shorten the diode's lifetime. Why are you discussing such high currents? 2A is a reasonable upper limit. Even at 1MHz and 100nsec you will still only see 0.1 W. What is your application?

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    Thank you for your response.
    I want to mount a laser diode pump system for a solid state laser.
    In a journal paper, someone operated a commerical 1W laser diode driven at high peak current levels of up to 20 A.(a pulsewidth of 20 ns at a repetition rate of 100 Hz.)

    Do you think it is possible regardless of shorten the diode's lifetime? few 1000 or 100 hours?





    Quote Originally Posted by planters View Post
    For very short pulses, picoseconds to a few nsec you may be able to exceed the maximum current rating by a relatively small percentage. Just like we do for CW operation with an understanding that this will shorten the diode's lifetime. Why are you discussing such high currents? 2A is a reasonable upper limit. Even at 1MHz and 100nsec you will still only see 0.1 W. What is your application?

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    I remember, but can not cite, an article about a special blue diode that had been fabricated to operate @ up to 100 A for a short pulse width. I cannot remember if the pulse width was on the order of msec and so this was QCW or if it was on the time frame you are talking about. This was within the last 2 years.

    Because these diodes are so small the facet and the leads that feed the chip are tiny. As the current is raised, the fact that these diodes will go LED before they short out means the intensity of the laser on the facet is so high that this is probably the weak link. Nevertheless, the V drop across the lead wires at 10 times the normal operating current will also be significant and in view of the manufacturer's decision to add an additional wire (3 to 4) when moving to the newer higher current (2A) M diodes makes me think these too will blow if you go that high.

    If you have some time and some extra money, you might try setting up a test rig to measure the destruction point in a series of diodes. Try cw, 1msec, 1usec and 1nsec and measure the maximum current at the point of failure. The trend may give you the confidence to proceed.
    Last edited by planters; 02-19-2013 at 10:10.

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    Lasers are distinguished from other light sources by their coherence. Spatial coherence is typically expressed through the output being a narrow beam which is diffraction-limited, often a so-called "pencil beam." Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can be launched into beams of very low divergence in order to concentrate their power at a large distance.

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    Did anyone ever do these tests.?

    The Cern Guys built some avalanche drivers for the blue LEDs (Cree) they generated 1uJ in a 2-4 ns pulse. That is some awesome peak watts (500 watts).

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