What laser(s) do you use?

First posting: Tue, Feb 20, 01 09:41:27 PM

Colin Kaminski

I am using a laser diode module from integraf. I find it is very asymeteric and the optics generate fringe paterns on their own. It has been fun for single beam setups but I would like to try some multi-beam setups. I have a D&S Laser power supply kit on order but I have not recieved it yet. Today I ordered an Infiniter 200 650 nm laser pointer. Cheap enough. Hopfully it will be colliminated well enough to get through my beam splitters. What laser(s) are you using? How well do they work?

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Jonathan - Wed, Feb 21, 01 12:53:48 AM
Colin, the Mitsubishi 35 mW diode works quite well in split beam setups. There are two things I found that were somewhat unexpected that you may find useful. One is that the collimating optics are actually quite variable in their effect on the beam. The fringes you mentioned, and other distortions, are greater or lesser depending on the luck of the draw from what I can see. I tried three (all the same type) before I got an acceptable beam. The other thing is to avoid the temptation to try to collimate the beam too narrowly. It worsens the distortion, and wastes more power. It can have a divergence a bit greater than a He-Ne laser and as long as it goes through a spatial filter it should be OK. If you can get it to behave in split beam setups you'll find it works beautifully - and you can forget measuring path lengths entirely. Hope this helps. 142.194.47.73

Colin - Wed, Mar 07, 01 12:19:56 PM
Thank you, Johnathan. I can't wait to try my 35mw laser. I recieved my Infiniters and found I like them better for split beam than the Integraf diode module (low on power though). But I like the Integraf module better for single beam work. Since it has no optics it produces a very clean beam. 64.167.148.4

Colin - Wed, Apr 18, 01 10:59:50 AM
Last week I recieved a MDL-BRK-660-35 laser from Laser Max ($290). It is reported to have a coherence length of about 1 meter and an output of 27mw after the optics. I ordered just the laser modual and not any accessories. I have to make a mount/heatsink before I can use it. I have drawings if anyone would like them. It involves a slitting saw so I had to ask my local machinist for help. I am using 3 d-cell batteries for the power supply. They were very helpful. I'll post more when I have some experience with it. Right now I am out of distilled water and have to wait till payday. 64.167.149.200

Colin - Wed, Apr 18, 01 11:01:53 AM
Here is the information about Laser Max. "Our recommendations for a holographic grade diode laser would take the following form: 1. The MDL 660-35 is the best available diode source for this application. We find that the higher power diodes tend to run single mode and this diode laser has about two meters coherence length. We have found that a short wavelength diode laser such as a 635nm-15 mW tends to be broader in line width as the current density is higher and will allow other spectral lines to compete. The price on this unit is $290 and we have several choice units in stock. 2. Any diode laser will mode hop and we have found that the diode must be on for about 10 minutes to stabilize. Use an external shutter for timed exposure, do not just switch the diode on and off as an electronic shutter. We would recommend that the laser be thermally stabilized to prevent mode hops. The laser would be set up in the BTC-2000, a compact peltier based temperature controller here at the factory and the temperature adjusted until the peak spectral line of the diode is in-between mode hops. This is a technique used in our own DMI laser interferometer product and with most telecom diode lasers. The price on this unit is $1590 and units are in stock 3. The last consideration is that the diode laser beam is elliptical and is one is seeking an illumination source to expose a holographic emulsion, you must overfill the area to be exposed or attempt to shape the beam. You can use cylindrical optics and prisms for beam shaping or we can set up a circularizer at the time of laser manufacture. The laser power will be reduced by about 40% with this option. This option is known as LS-90 for $395 and units are in stock. Please contact Kathleen Fox or myself if you have any further questions. Best Regards, Will Houde-Walter" 64.167.149.200

blueeyedpop - Fri, Apr 20, 01 09:11:12 AM
Does anyone here have any experience with the diodes from blue-sky?http://www.blueskyresearch.com/products/p_circulaser.html the ps-104 in particular. They use a micro-lens that shapes the beam at the face of the laser. I'm ordering a module from power technology (the PMP(658-35B)G3 -$330.00) that incorporates this laser. http://www.powertechnology.com/pti/index.asp 64.63.88.51

Ronny - Fri, Apr 20, 01 12:51:17 PM
blueeyedpop, that's the same type that I'm using. It's a very good One. Warm up time=0, with a loooooong coherencelength. Right now I'm using this laser on my PFG-03M plates to make good reflection masters and transfers. So far It's perfect! I'll ask Vidar Hegdal to introduce a report on this on "Vidar Hegdal's webpage" when I'm ready? Gooood Luuck 62.66.239.37

Colin - Fri, Apr 20, 01 05:54:17 PM
Ronny, Do you have any problem with the fan causing air movement? Does the fan stay on or cycle? This laser looks like a great deal. Circular beam, 35mw, temperature controlled and $330? 64.167.149.200

blueeyedpop - Fri, Apr 20, 01 10:17:56 PM
I don't think this one is temp controlled http://www.powertechnology.com/PRODUCTS/PMP.ASP it's defined as constant optical output, although I am prepared to build a temp control if I have to. Hey Colin, how's your new toy? I just pulled the collimating optics off of my 35mw 658nm diode ( this one's 660) and found a beautiful spread beam. I just might give a single beam reflection a shot this weekend . 64.63.88.51

Ronny - Sat, Apr 21, 01 03:19:46 AM
blueeyedpop, I have One from Powertechnology w/out fan # PMP27(658-35B). If you ask Glenn Sullivan/Sales Engineer at PT hi knows that this one is the same as I'v purchased. It's the same that Frank (webmaster)have too. Price in 1999 was $525. The only cooling I'v made for it is a Aluminium house, please take a look at Vidar Hegdals's homepage. I have heard from another holographer in the US that he have a PPM laser with a little blower in the back. "An interferometer showes mode hops and unstability" he told me, and he was not able to use it. Hope it's not the same with yours. If so please contact Glenn Sullivan and return it. I'v never had problems with mode hops after changing my ac/dc converter to battery supply. After the object/plate relation has stabilized for some few minutes I turn On my laser, wait for two minuttes and make my exposure. Then I'm turning my laser OFF again. It works for me as U can see on my results. 62.66.239.55

blueeyedpop - Sat, Apr 21, 01 12:39:26 PM
I wonder what the 27 in your laser's part number represents. I have dozens of 12v 1 amp lead acid gel cells which I plan to use for power, so I'm not the least bit concerned over my power supply. as for the fellow in the states with the mode hopping laser, I have to wonder if there was something wrong with his unit. His should have been ultra stable. 64.63.88.51

Ronny - Sat, Apr 21, 01 01:23:59 PM
27=27mW..Have a nice Weekend 62.66.239.25

blueeyedpop - Sat, Apr 21, 01 03:09:40 PM
Your news is very exciting! Thanks! 64.63.88.51

Colin - Sun, Apr 22, 01 01:49:12 AM
I powered up the new laser (MDL-BRK-660-35) but I only as a short test. I am still making the heatsink (and still no water till friday). The beam is very bright and appears as advertised. I have extensive experience with peltier design and thermal assemblies if you need any help... (I use about 250 Melcore chips a year. www.melcore.com). If you can't make their minimum order I can place it with one of mine. What I don't have is a simple "do it your self" PID controller. All of the commercial ones are very expensive and offer features we don't need. 64.167.150.39

blueeyedpop - Sun, Apr 22, 01 02:46:59 AM
Does the control circuitry for the peltier need to be a PID? With the thermal constant of the aluminum, couldn't a more simple thermostat be used? Optionally, I have some analog drives for motors. I wonder if they could be used in velocity mode to control the TE cooler in conjunction with a temp. sensor for the "velocity". Do te coolers handle pwm very well? How many P/N junctions do you recommend? I use a large one as a soft drink chiller for my office, I keep a Diet Coke at about 40 F. , but this is the extent of my experience. Congrats on the new laser. 64.63.88.51

Colin - Sun, Apr 22, 01 12:34:01 PM
I calculated the load to be about 4 watts for the Mitsubishi 35 mw diode. Lasermax uses 10 watts. Seems like a good margin. I am pretty sure what is needed is a proportional control. The hysterisis in a simple on and off thermostat would overshoot our .1 degree requirement. It is possible to make a TE assembly without a fan and it is what I would try first. Otherwise you need to relocate the laser off the table. One junction has the ability to cool to 70C below the hot side. I would expect the hot side to run about 15-20C above ambient in a no fan design and less in a design with a fan. So if your question is "how many junctions is series?" Then the answer is 1. If your question is "How many junctions in parallel?" Then the answer is enough to provide 10 watts of cooling (which is one small chip with 30 junctions if I remember my melcor part number system). I would start with the PT4-7-30. The PT series is cheap and reliable. It would require a temperature controlled variable voltage supply from -3 to 3 volts and 4 amps. (The minus voltage would heat up the laser for shorter warm up times) Should be easy for an EE type. And the address is really www.melcor.com. If anyone can design the circuit let me know and I will make a prototype. 64.167.150.39

blueeyedpop - Sun, Apr 22, 01 08:16:58 PM
I'm going to crack the books, and ask some guys at work. I'm pretty sure I can figure something out. The .1 degree thing is the tough part. Do you have any pt4-7-30's available? I found an informitive site ( http://www.tellurex.com/resource/txfaq.htm ) than answered a lot of questions, but I know Melcor is the leader. Thanks, I'll keep you posted. 64.63.88.51

Colin - Wed, Apr 25, 01 02:40:32 AM
No, I only stock the biggest chips. I place an order every 3 months and usually they take 8 to 10 weeks to ship. I just recieved my latest order yesterday. The thermocouple melcor provides a hole for is very small and has very little mass. It should respond very quickly. Remember we don't care what the temperature is only that it is adjustable and very stable. 64.167.149.76

blueeyedpop - Wed, Apr 25, 01 11:45:55 AM
Do you find that a small thermal mass on the cold side is better or worse for stable operation? I'm looking into two options right now. A linear analog approach, with current proportional to the difference in temp. , and a digital approach, with pwm output under microcontroller operation. 12.127.138.174

Colin - Thu, Apr 26, 01 03:32:01 AM
I'll e-mail to save bandwidth. 64.167.150.45

Colin - Sun, Jun 10, 01 11:02:43 PM
I finally finished the heat sink and mount for my MDL-BRK-660-35 from Laser Max. I set up an interferometer today and checked it out for about 10 hours. It takes about 15 minutes to stabilize. After about 1/2 hour I saw one more mode hop. I expect my shop was gaining temperature as it was when the sun was on the wall closest to my bench. I could only make a path length difference of 4.5 feet. I work on a small table and only have two relay mirrors mounted at present. It is coherent to at least that distance. I will try to make some holograms in a couple of weeks. Unless I find time tomorrow. :-) 63.193.192.35

Tuba - Wed, Aug 29, 01 11:38:11 AM
Hi Colin, I have read that you have extensive experience with peltier devices. I need an expert help to be sure that the heatsink that I designed would be sufficient to dissipate the active+passive heat. If you could answer to this message approving further communication with me, I would be much glad... Thanks in advance! All the best! 141.99.129.32


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