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

[Terry Morris W5TDM]

I was under the impression that most DPSS green lasers use pump lasers at 
808nm which then pump a downconverter crystal of ND.Vanadate (ND:YV04) which 
outputs 1.064 um beam, this is then used to pump a crystal frequency doubler 
of KTP which outputs 532nm. I may be wrong, but last time I looked there 
were no laser diodes at 1.064 with enough power to directly pump KTP to this 
output level, but technology does move along.


>From: Art <KY1K at verizon.net>
>Reply-To: Free Space LASER Communications <laser at mailman.qth.net>
>To: Free Space LASER Communications <laser at mailman.qth.net>
>Subject: Re: [Laser] Wicked Lasers Fusion (125mW 532nm) Modulation
>Date: Sat, 22 Sep 2007 00:49:01 -0400
>
>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
>>_______________________________________________
>>Laser mailing list
>>Laser at mailman.qth.net
>>http://mailman.qth.net/mailman/listinfo/laser
>>
>>
>>--
>>No virus found in this incoming message.
>>Checked by AVG Free Edition.
>>Version: 7.5.487 / Virus Database: 269.13.22/1015 - Release Date: 
>>9/18/2007 11:53 AM
>
>_______________________________________________
>Laser mailing list
>Laser at mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/laser

_________________________________________________________________
Share your special parenting moments! 
http://www.reallivemoms.com?ocid=TXT_TAGHM&loc=us