Lasers and driver boards for sale

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).

Opnext HL6385DG….

I just got a few of those 150mW/642nm diodes, which are characterized by “single longitudinal mode” in their data sheet. There was a special price for them during this months; and also a group buy at photonexicon.com.
Obviously of potential interest to holographers…the warm color would be well suited for color holography, and it would work well with optics intended for HeNe lasers such as waveplates.

I immediately ran tests on one of them, with disappointing results at first, but subsequent more careful tests revealed single mode regions at high power and low temperatures, see here. This now seems very promising and I will test more of those diodes, also in ECDL setups – stay tuned.

PS 09.09.09: I found, not unexpectedly, that the HL6385 does fine in an ECDL setup, for details see here.

ECDL reloaded

My first attempt at an external cavity diode laser (ECDL) didn’t work nicely at all, it didn’t run single longitudinal mode and thus was completely useless for holography purposes. Recently I just put in other types of diodes, notably a high power “open can” DVD burner diode, and immediately things worked out perfectly! See for details here. I wonder about the great difference – perhaps it is just the missing output window of the diode?

I also used another sample of those diodes in an commercial ECDL laser that was originally designed for 780nm. And voila, it worked again very well. Some info on this (quite simple) conversion of this laser is here.

Finally, I wanted to see how a “blu-ray” 406nm diode works in an ECDL setup; before I had found that the bare diode by itself is totally unsuitable. I found that in my ECDL configuration the diode can run single longitudinal mode but only to powers of approx 15mW. See for details here.

PS. Aug 28: I was playing with a Mitsubishi ML101J27 in an ECDL and it worked fine .. until I changed polarization and the stronger feedback killed the diode despite I thought was careful. Good that I learned this lesson with that diode and not with an Opnext HL6285… one lesson is to determine the diffraction efficiency of the grating, for both polarizations, and then estimate the maximal drive beforehand. But there is no really safe way to find out what the maximal power of an ECDL is. At any rate, I plan to try an Opnext soon.

Prototyping.. updated

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.

Open can and blu-ray DVD diodes…

I have acquired some more laser diodes for testing their suitability for holography.

The first thing to try out was to measure the mode spectrum of one of those high power “open can” DVD burner diodes, which can do several hundered milliwatts when tortured. Well, the news is –not unexpected– that those diodes are totally unsuitable for holography. see here. Moreover I found the the familiar Sony SLD1236VL and SLD1239JL-54 diodes a little bit better, but not too much.

Summarizing, for all DVD diodes I tested the rule seems to be that they can run single mode at up to 70-90mA, which yields approx 20-30mW. There may be exceptional stable spots higher up, eg. I got approx 50mW with one Rohm diode, for example. The best diode so far was the Mitsubishi ML101J27 which got up to approx 80mW (with some weak other modes; true single mode up to approx 50 mW). Thorlabs sells it as single mode diode, probably for good reason, however there is no mention of this in the data sheet.

There is a number of declared single longitudinal mode diodes, esp from Opnext/Hitachi, some with powers exceeding 100mW. Most likely they would be the way to go, I will try to get a handle on them and do some measurements; unfortunately the more powerful ones are quite pricey. But it seems there is no easy way around that if one aims for more than 30-50mW.

Note added: I now checked a GH04P21A2GE/PHR-803T “blu-ray” diode and the results are here. In a nutshell: totally unsuitable for holopgrapy!

Finally…

.. 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.

Welcome

This is a test to see whether it works… everybody has a blog now and why not me. I get lots of technical questions by email, and it might be easier to have discussions in a blog rather then by mail. So please feel free to drop by, english and german spoken here.

So what happened here during the last two years? Almost nothing, I didn’t have much time for my hobby but plan to be more active again. There is a major incomplete project, namely of stabilized 650nm diode laser modules suitable for holography. I had made a prototype which works well (stable single longitudinal mode at approx 50mW), and next I would build some more of them; but this requires some PCB and mechanical work for which I don’t have time right now.

Moreover I’d be eager to do some holography again, but this requires setting up my optical table which is completely blocked right now by the spectrum measurement apparatus I need for the diode lasers… to bad that I don’t have space for more than one concurrent project.

On the long run, I will try a single mode high power DPSS laser; I have already collected lots of parts like Yag rods and disks, KTP’s, diodes from 2 to 60W, 100A power supplies. All sorts of cooling, temperature stabilization, pump optics design, thermal lensing, green noise, etc, issues will come up and this will be a huge effort as far as I can see. But as a fellow holographer has said…. adversary builds character