[Laser] Wicked Lasers Fusion (125mW 532nm) Modulation

[Art]

Joe,

The 'slow ramp' time has little to do with the drive signal you apply.

It's all about the temperature of the IR diode that drive the optical 
doubler crystal. If you attach a temperature sensor to the IR laser, 
you will find that the output peaks when the temperature of that 
diode reaches a certain temperature. That's because the output 
frequency of the IR laser diode varies with temperature. Diode output 
at 1065 or 1063 nM does not produce any output at 532 nM.

If you apply heat from an external source-such that the ambient 
temperature is maintained at the 'sweet spot' whether the diode is 
turned on or not, the diode can be pulsed and will have full output 
very quickly.

Of course, you have to be able to turn off the heating element when 
the laser is operated at higher duty cycles-so active temperature 
sensing and a controller is necessary.

The bigger bench top green lasers have multiple temperature 
sensors-generally one for each of the multiple IR lasers. Sam's FAQ 
has some information about the methods of regulating the temperature 
in the vary large and high end green lasers. These high end power 
supplies often have 10 or 20 inputs and outputs, which mainly have to 
do with temperture sensors and the ability to regulate the 
temperature of the internal 1064 nM laser diodes.

To answer your questions:

1)      It is characteristic of the DPSS laser, mainly due to the 
fact that the IR laser doesn't run at 1064 nM immediately on powering 
up.If it did run at 1064 nM on power up, the output would decrease 
dramatically after some time in the on position.

2)      You can PWM the green laser just fine-provided you can sense 
the temperature of the IR laser and maintain it at that temperature 
as the duty cycle changes.

3)      No. The larger higher powered 1064 nM IR laser diodes can be 
run with a simple current limiting resistor just as the higher power 
red diodes can. That's because the range of input current (or margin) 
is much wider in a higher powered laser diode. For instance, you need 
optical feedback to control most small laser diodes because the 
difference between lasing and destructing is perhaps 10 mA. But, 
large laser diodes might start lasing at 1 amp and be able to 
continue lasing at 3 or 4 amps without self destructing-hence a 
simple current limiting resistor can be used on the larger diodes.

In general, the hand held battery powered green lasers are usable for 
star pointers. To have a continuously modulateable pulse green laser, 
you need an active temperature sensor and some means to apply heat to 
keep the internal 1064 nM laser diodes at temperature when no output 
is being called for.

Regards,

Art



>My questions are as follows:
>
>1) Is the "ramping" effect due to some internal regulating circuitry of the
>pointer, or is it a characteristic of DPSS lasers?
>
>2) Is there any way of pulse-modulating the beam by switching the 
>power supply
>of the laser, as I have done with the <5mW red diodes? If not, what is the
>best way of externally modulating the beam? Are the LCD shutters that have a
>fast enough response time (i.e., <1 microsecond)? Etc?
>
>3) Do pointers like this rely on the internal resistance of the alkaline
>batteries to limit current (as is the case with some LED flashlights)? I.e.,
>is it safe to use an external 3v supply with the pointer without burning out
>the diode?
>
>Thanks,
>
>~Joe
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