690nm LD + flickering beam
On: Sun, Jan 27, 02 06:00:02 AM
Thilo K. wrote:
a relatively long time ago, I bought a 690nm LD and a driver
for that. But I could not modify the driver to work in cw.
Addidtionally, I could not lower the current of it to achieve
about 640-660nm. Do you know any driver manufacturer - or
reseller, whose drivers can do both ? At best in germany ?
Thank you in advance
Tom B. - Sun, Jan 27, 02 07:26:02 AM You will not get the change in wavelength that you
want by changing the driver. Wavelength changes by
only a few nm with drive current, and is mostly
determined by the LD construction. You want a new LD
and driver, and there are MANY low-cost LDs and
modules available in the 640-660 nm range.
For German sources, try http://www.roithner.de/
regards, tom 220.127.116.11
Thilo K. - Mon, Jan 28, 02 09:09:50 AM why do all people think that Roithner would be a good choice ?
Please, do not recommend roithner any more ! I do not tell
you because I could be a competitor. I claim that because I
ordered drivers there, and none worked the way it should.
So I sent all drivers back and told them to repair. But
there was no response at all - though the address the
delivery was sent to was rightly written. So I lost very
much german marks.
So please, ask as much people as you know not to order at
Tom Naiser - Mon, Jan 28, 02 02:29:33 PM I have recently bought an iC-WK laser diode driver chip from
lasercomponents (www.lasercomponents.de). You can either get
the SMD-chip alone ( 6 or 7 Euro) and and build the driver
circuit by yourself (very easy - see the specification file
available from lasercomponents - you only need a handfull of
resistors and capacitors) or you can buy the readybuilt
driver-module (which allows diode power adjustment) iCSYWK1D
(or iCSYWK2D if you have a p-type diode) which costs around
15 Euro. The driver works fine - the fringes are rocksteady
(at least over a time range of about 10 Minutes).
A problem that I still have using this driver with my 35 mW
Mitsubishi-diode is that of the "sliced bread-syndrome"
described elsewhere (the problem is probably caused by the
diode itself and not by the driver). As Tom B. said, varying
the diode current can change the wavelength only by a few
Has anybody experienced that the the "sliced-bread-syndrome"
gets reduced by increasing the diode current.
I have read that if the laser power is increased the mode in
the centre of the amplification profile is growing stronger
than the modes adjacent to it. So the single mode property
of a diode, that we all want, should improve as the diode
current is increased. 18.104.22.168
Tom B. - Tue, Jan 29, 02 03:55:12 AM Re sliced bread: A while ago, I mentioned looking
at fringes from an ML1016 in an simple interferometer
setup. I noticed that as I varied the mirror spacing,
the fringes would vary from high contrast to low contrast
evey inch or so of spacing. I guessed that this was due
to multiple lines in the spectrum. One big unknown is
whether reflections back into the diode from
the interferometer setup were destabilizing it.
When I set the mirrors to a low contrast spacing and reduced
the drive current from 25 to 15 mW, the fringe contrast
seemed to improve, but was never as good as the best
contrast position. There were a couple of "zones of
instability" in the 15-25 mW range in which fringes were
completely washed out. Listening to the amplified photodiode
fringe washouts were accompanied by lots of noise, which
I assume was due to frantic mode hopping. One thing I
did not try, and will have to try soon, is to look at
ML1016 behaviour in the 25-35 mW range - maybe it
DOES gets better at higher current.
Thilo - Tue, Jan 29, 02 06:52:45 AM Tom N.,
you mentioned: "[...]and build the driver circuit by yourself (very easy - see the specification file available from lasercomponents - you only need a handfull of resistors and capacitors)[...]"
Occasionally, I have already bought the driver ic. Though it might be simple for advanced users, I prefer having a simple tutorial for it - could you describe what to do using simple words ? 22.214.171.124
Thilo - Tue, Jan 29, 02 06:52:56 AM Tom N.,
you mentioned: "[...]and build the driver circuit by yourself
(very easy - see the specification file available from
lasercomponents - you only need a handfull of resistors and
Occasionally, I have already bought the driver ic. Though it
might be simple for advanced users, I prefer having a simple
tutorial for it - could you describe what to do using simple
words ? 126.96.36.199
Jonathan - Tue, Jan 29, 02 01:40:52 PM Tom B., it's interesting what you've found in regard to
mirror spacing with your interferometer. When I've set one
up I've encountered similar periods of high and low
contrast, as well as complete wash-outs but I've never
played around with the mirror spacing. Always attributed
the fringe behaviour to temperature fluctuations within the
In pursuit of a solution I've talked to various people, and
learned that there are various approaches to frequency
stabilization of these laser diodes, some already
implemented successfully such as Yves Gentet's Samourai
Others have only been worked out on paper. One firm that
specializes in TEC's and the like has used a software
algorithm and control system that basically optimizes the
relationship between temperature, power, current, and mode
hop zones. It works well with DPSS lasers and they say it
can be scaled down for certain diode lasers to eliminate
mode hopping altogether.
I'm sure there's an inexpensive and practical solution out
there somewhere, or at least coming soon. I hope so because
I would like to get on with doing holography. There are
enough challenges without worrying about the laser.
Tom, if you are interested in exchanging some details
please feel free to email me at firstname.lastname@example.org 188.8.131.52
Jim McPherson - Thu, Jan 31, 02 11:37:40 PM Do you think there might be some conflict with the TEC
trying to keep the laser lasing the same and the photodiode
trying to keep the laser lasing the same? It seems that APC
is best when passive heat control is used and TEC's are
best when a constant current driver is used. This makes
sense if you think about it. If you keep the temperature
exactly the same then your current should stay exactly the
same, thus making a stable diode.... what do you think?
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