Archive for the ‘Electronics’ Category

Arduino-shield high precision TEC controller for laser diode holography

December 10, 2016

Finally, after more than 1/2 year of work this project is completed; well, almost, I still need to tweak software, but I won’t have time for the rest of the year. Here is a quite exhaustive writeup, so nothing needs to be added for now in this blog.

The plan is to develop next another Arduino shield as a companion, very stable laser diode driver. This will be hard since noise and stability requirements will be harder, and not easy to reach given the noisy digital environment. As preparation I have set up an extremely sensitive low noise amplifier for measurements (see previous post).

Moreover, a miniature combo board of TEC and laser diode controller is planned, but only after having gained more experience with the present controllers.

I may sell some of the controllers at a later time once the complete package incl diode driver is done and turnkey useable.



Revitalizing the Coherent Sapphire 488-20

September 11, 2011

There was a moderately good ebay deal to be had and so I decided to bring a Coherent Sapphire 488-20 laser head plus driver board back from my trip to the US – along with 20kg of other laser goodies ;-). This is an interesting, though not too powerful optically pumped semiconductor laser (OPSL). The board looked new but the head was used and sold as “probably not up to specs”. Indeed so, I measured 9.6mW instead of 20mW, but I figured out, by some reverse engineering, how to bring it up back to specs, ie, 20mW with clean stable single longitudinal-mode operation. Adding a housing for the driver board and a few analog and digital controls, et voila… system ready for holography! For details see here.

… been a busy fall

December 5, 2010

Well the title says it all, I have spent the last couple of months in developing/building/testing a new series of driver boards, and complete ECDLs. While the boards and red ECDLs run very well, the 445nm ECDLs still make headache for stability reasons; 40-60mW can be done pretty well but everything beyond that is hard to keep stable over extended periods of time.

As soon as I have found a good way to have the die cast aluminum cases painted, I will sell off a few lasers, to make room for new projects. Here some eye candy:

PS: Drivers are sold put, most lasers too. I am not sure
whether I will build more, as the effort is barely worthwhile ;-( Just in case, keep an eye on my blog!

General Technical Discussions

October 24, 2010

The original post was about the closure of the holography forum, which has now been replaced by the holoforum created by Ahmet.

I changed the title and topic of the thread, as various general and interesting comments were made that had nothing to do with the closure of the forum. I think in this way the information will be easier accessible.

Lasers and driver boards for sale

September 4, 2009

Finally, after many weeks of extensive burn-in and long-term mode stability tests, I now have a few lasers ready to go, as well a couple of highly stable diode and TEC driver boards for DIY holography lasers; details are here. Some of the lasers were sent off today for testing in real-life holography. I will report when I know more. If you are interested, contact me.

The boards are 79€ each plus shipping, with suitable Peltier element and thermistor 4€ more. The 640nm lasers go for 275€ and the 658nm between 180€ and 200€ depending on the power.

Note added (Jan 10):
I got some more lasers, the new ones have a noise detection feature built in, which is supposed to help to detect instabilities due to backreflections etc. More details are here. The extra for each laser is 20€. I sell separately the ready-to-use boards for 20€ as well, you can use them with your own lasers (a glass plate beam splitter is needed in addition).

Note added (Feb 15):
All lasers are sold out, I am not sure whether I will build more of this kind anytime soon. Right now I am looking into ECDLs to see whether they have a substantial advantage over bare diodes such as to justify the higher costs. So far it seems that the achievable stable power is not much higher as compared to bare single mode diode lasers, and the main difference, a very small line width, is not relevant for ordinary holography purposes. Stay tuned.

Prototyping.. updated

April 24, 2009

Well the last few weeks were quite productive and not only I completed a series of measurements, but I also finalized the development of a stable laser diode driver and TEC controller. All went very smooth without major obstacles, apart from a surprise with trim pot noise.

I now have received the PCBs for the drivers, and in an evenings’ work eagerly completed the first prototype:

Next thing is to check that all still works properly and conduct extensive measurements. If all goes well, I would be able to produce 4-5 complete units plus a few drivers separately, and put them up for sale. Please contact me if you are interested.


February 7, 2009

.. I found time and will to put together laser diode driver, TEC controller, data conditioning circuitry and USB interface in one case. One of the DAC’s had been damaged when cleaning up the mess of circuits and loose wires, and the prospect of replacing that tiny SMD device (with the danger of making the whole PCB unusuable) had reduced my incentive to go on with this project since two years…well there were other reasons too. But it wasn’t that bad after all. So now everything works again and I go on developing a stable single mode red diode laser suitable for holography.

Next thing was to rebuild Colin’s laser head with extra emphasis on thermal stability. Just right now automated scans are performed for determining the best operating point (current and temperature). On the pic above you see the laser head in front of my universal diode controller incl digital measurement machinery.

I now also performed long term stability measurements, and posted the results on my revamped web site. After a few minutes warm-up time, the laser runs stable single mode without jumps for hours; the price is a moderate 32mW output compared to the 100mW+ the Rohm diode can do.