Old 06-28-2011, 06:05 PM #1
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Default Where to buy true continuous wave lasers?

I recently bought a laser advertised as 'continous wave' operation but when I checked with a photodetector & oscilloscope I can measure that it is really a pseudo continuous wave with nanosecond pulse emissions.

Where do you buy true continuous wave lasers? And where will be the cheapest place to buy them?


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Old 06-28-2011, 07:33 PM #2
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Default Re: Where to buy true continuous wave lasers?

How can you be sure it wasn't a flaw in your setup? Which laser did you buy?
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Old 06-28-2011, 07:37 PM #3
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Default Re: Where to buy true continuous wave lasers?

What are you using the laser for?

If you're looking for a "cheap" CW laser, your application is obviously not sensitive enough to use this "nanosecond pulse" laser...

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Old 06-28-2011, 09:11 PM #4
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Default Re: Where to buy true continuous wave lasers?

I have a photodetector (photomultiplier with voltage amplifier) and an agilent oscilloscope with single ns temporal resolution measurement.

The laser is just a commercial <20mW green laser (IR diode pumped crystal with IR filter at output aperture). They claim it is continuous wave laser (in the specs). I can measure it is really 20ns pulse emissions.

Short of building one from scratch myself, do people know a source for truely continuous emission commercial lasers and where one can find them the cheapest? (Obviously newport and thorlabs have them but they are more expensive).

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Old 06-28-2011, 09:19 PM #5
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Default Re: Where to buy true continuous wave lasers?

50MHz...

I'd like to see images of the laser and of its driver. Green lasers just don't do 50MHz...

Quote:
I have a photodetector (photomultiplier with voltage amplifier) and an agilent oscilloscope with single ns temporal resolution measurement.
Not even the most expensive equipment in the world will give you correct results without a correct method...

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Old 06-28-2011, 10:14 PM #6
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Default Re: Where to buy true continuous wave lasers?

Why must most forum discussions always go through this? Only judgements but the original question of any importance to the OP is not answered.

So, where can one find commercial continuous wave lasers the cheapest?

Quote:
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50MHz...

I'd like to see images of the laser and of its driver. Green lasers just don't do 50MHz...



Not even the most expensive equipment in the world will give you correct results without a correct method...

-Trevor
OK. I will play the role of the inquisitive novice here.

Please explain why 'green' lasers cant do 10^8s pulses.

Since you seem to be very familar with my setup, please explain to me what is wrong, and then explain what is the correct method to do the experiment.
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Old 06-28-2011, 10:22 PM #7
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Default Re: Where to buy true continuous wave lasers?

It is impossible for the lasing medium to be pulsed that fast. It takes much longer than 20ns for the Nd to depopulate.

I bet your setup would say the sun was pulsed at the same rate. Try it.
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Old 06-28-2011, 10:27 PM #8
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Default Re: Where to buy true continuous wave lasers?

I mean, it just seems a little superfluous to replace a laser that doesn't give any indication that it really is misbehaving, given the properties of the lasing medium that Cyparagon mentioned.

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Old 06-28-2011, 10:32 PM #9
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Default Re: Where to buy true continuous wave lasers?

Quote:
Originally Posted by obiti View Post
Why must most forum discussions always go through this? Only judgements but the original question of any importance to the OP is not answered.

Since you seem to be very familar with my setup, please explain to me what is wrong, and then explain what is the correct method to do the experiment.
Maybe it's your approach...
A little snooty for a new "expert" member... me thinks...
They seem to be coming out of the woodwork this week...

Perhaps you should ask your question over at PL... since the
members here can't seem to give you the answer that you want
to hear...


Jerry
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Old 06-28-2011, 11:06 PM #10
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Default Re: Where to buy true continuous wave lasers?

Quote:
Originally Posted by obiti View Post
I recently bought a laser advertised as 'continous wave' operation but when I checked with a photodetector & oscilloscope I can measure that it is really a pseudo continuous wave with nanosecond pulse emissions.

Where do you buy true continuous wave lasers? And where will be the cheapest place to buy them?
There are many probable causes.
First answer a few questions for me and I'll take a look at your test setup and try to help you

1. What is the exact model number of the O-scope? ( I need this to verify both its bandwidth and sample rate)
2. Same goes for any test scope probe. Also tell me how the scope is setup as far as the selected Mega samples or Giga samples per second. This can also vary depending on how many channels are in use.

3. Model of the photodetector so I can make sure it's capable of this bandwidth.

These will help me get to the bottom of this and eliminate any aliasing of the signal that may be showing up on the scope.

4. Model of the laser head and driver (system), so I can take a llok at it's specs.

I know your interested in a very cheap (as far as cost goes) laser system, but with that you can't expect miracles of performance either.

My guess without knowing any of the details of your test setup is that what you're seeing is high frequency noise and that it probably is a continuous wave laser like they advertised, but does have high frequency noise as well.
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Old 06-28-2011, 11:10 PM #11
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Default Re: Where to buy true continuous wave lasers?

^Great post! All DPSS lasers are subject to noise, some worse than others. There are advanced scientific/industrial lasers with compensation for the noise, so that it is all but eliminated, but pretty much every inexpensive, simple-cavity DPSS laser you'll see will have high-frequency noise in the output. You could do better with a singlemode diode laser if stability is what you're after, but you won't find those in green, at least not affordably priced yet,
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