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    Photos of Coherent Diode Pumped Solid State Lasers

    Since some of these descriptions are quite long, this page has a Table of Contents:


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    Coherent, Inc. Compass 315M Green DPSS Laser (Gallery)

    Here are some sets of photos of a very high quality single frequency 100 mW green DPSS laser manufactured by Coherent, Inc.. Go to "Products", "Commercial Lasers", "Solid State Lasers".

    This is a compact laser head (about 4 inches long, the holes on the optical table are spaced on 1 inch centers as a handy reference), manufactured with robotic assistance.

    The first set of four photos show the overall laser head and details of the interior. The photo collections that follow include some complete dissections which may be too gory for the faint of heart. :)

    There is more information on this laser in the chapter: Solid State Lasers of Sam's Laser FAQ.


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    Coherent, Inc. Compass 315M Green DPSS Laser - Photo Collection 1 (Gallery)

    The first set of photos shows the laser head mostly intact along with its power supply. These are for general audiences. The second set of photos shows the start of a dissection - not for the faint of heart. :)

    (The following photos and portions of description provided courtesy of: Bob.)

    The laser head is/was hermetically sealed. Even the output window was soldered. Unfortunately, all the interesting cavity components are hidden inside the ceramic box. We thought at first that this uses Coherent's ring cavity laser design but from close examination, it would appear to be a conventional Fabry-Perot cavity.

    There are two 45 degree turning mirrors on the left of the the laser cavity. These look like right angle prisms, but are actually front surface dielectric mirrors. I presume they are right angle prisms so that they have a nice square mounting face. The sliver of glass between the turning mirrors is the pick-off for the photosensor. The next optical element (lower middle) is a spherical lens (even though it is shaped in a rectangle, again for ease in mounting) for collimating the beam, and finally, a sliver of metal (stainless steel, I think) that serves as an aperture to block any stray light.

    The only other structures you can see in the photo are the laser diode. (the gold box in the upper right hand corner), and the laser cavity - the ceramic box with the gold zigzags. Too bad I can't open the box without destroying the goodies inside. :)

    The gold serpentine pattern on top of the ceramic box is not a heater, because it isn't electrically connected to anything. I checked already. My only guess is that it is for structural attachment - perhaps the side and bottom panels of the ceramic box have similar zigzags. The component in the diagonal gap of the ceramic box is an intracavity aperture. The gray piece at the left is an extra-cavity aperture.

    It appears as though the IR light from the pump diode and 1,064 nm leakage is prevented from exiting the laser not by a filter, but by the selective coatings (reflect green, pass IR) on the two turning prisms. There is an IR filter (the green thing visible between the prisms) to block IR light from the photosensor but it isn't in the main beam path.

    Now for the gory part. Some of these views are quite graphic. You should send the kids to bed or to the aunt or something. :)

    Unfortunately at this point the laser is non-functional. When I took the baseplate of the unit off by milling it out from the bottom, the vibrations caused the YAG rod assembly and HR to break free of their mounts. (Hey, maybe that's covered by the warranty! :) --- Sam). The only way this thing will lase again is if the parts were reassembled. Nothing got dinged though. The diode still works.

    I don't know how realistic it would be to get this lasing again. These things are soldered together, not just glued. If you were to grind down the remaining solder, the optics could then be glued in place, but that would require very accurate positioning in 6 axes, not to mention getting REALLY lucky replacing the diode in exactly the right spot. The temperature sensor for the case is also broken free and that would have to be replaced somehow, and the TECs are broken free from the case. They would have to be resoldered somehow too. All in all, a lot of work unfortunately.

    (From: Sam.)

    Well, it would be sufficient to get it lasing. It doesn't need to meet original factory specs. :) After all, you weren't using any of the TECs or sensors when you tested it!

    I have since reattached the YAG rod assembly and remounted the pump diode (though it still needs to be aligned), as well as gluing the broken sensor back in place. To go further, I will need to set up an alignment jig with a HeNe laser shooting through the output stop and KTP to center the pump diode and then mount the HR mirror on a multi-axis micrometer positioner to attempt to get it lasing again. And, a heatsink for the LD and cavity TECs will be needed to run for any length of time.

    More to come. We still don't know if the patient will live.

    There is some more info on this laser in the chapter: Solid State Lasers of Sam's Laser FAQ.


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    Coherent, Inc. Compass 315M Green DPSS Laser - Photo Collection 2 (Gallery)

    (The following description provided courtesy of: Dave (Ws407c@aol.com).)

    Here are photos of another C315 laser and an exploratory - you can call the kids back in now. :) It turns out that no hot plate is needed to remove the lid - gentle persuasion with an Xacto knife at one corner enabled the lid to be popped off easily. And, note the corrosion under the lid - that shouldn't have happened even under severe conditions.

    This unit was made in December of 1997 and shows a reaction between the solder and the metal of the case. I am sure that complaints of the output window falling off will be heard as more of these units fall into the hands of the common experimenter. Looking into the window of a newer unit (March 2001) shows a cold solder type of joint. The older unit looks a lot worse, almost a crystalized look to the solder.

    (From: Sam.)

    In fact, examining the carcass I have of the other C315M (above), it appears that many of the solder mountings really aren't done well - and this was a brand new unit just out of its original antistatic bag. The quality would be ranked below poor by the standards of electronic soldering. I know that the HR and YAG came cleanly off during the disassembly of the case. One wall of the cavity looks like it was broken off just by applying sideways pressure. Few of the soldered surfaces look properly wetted and I suspect that many would break between the optic and solder (as did the HR and YAG) rather than within the solder itself as expected of any respectable soldered joint. Perhaps they can't use normal flux because its vapors would coat the optics but there must be a way around this. Solder is good and stable if used properly but it can't be applied like glue!

    (The following photos provided courtesy of: Dave (Ws407c@aol.com).)

    More information on the C315M laser, including connector pinouts, is available in the chapter: Solid State Lasers of Sam's Laser FAQ.


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    Controller for Coherent, Inc. Compass 315M Green DPSS Laser (Gallery)

    Here are some photos of the controller used to power the C315M laser. This unit includes the laser diode driver, three (3) TE controllers, and probably other circuitry to stabilize the laser. The last photo is of the PCB on the side of the laser. The settings of the pots on this PCB program the controller for the characteristics of the particular laser so nothing needs to be adjusted when swapping lasers.

    (The following photos provided courtesy of: Dave (Ws407c@aol.com).)

    More information on the C315M laser, including connector pinouts, is available in the chapter: Solid State Lasers of Sam's Laser FAQ.


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    Coherent, Inc. Compass 415M Green DPSS Laser (Gallery)

    This is the larger cousin of the C315M with available output power of 200 mW or more.

    There is more information on this laser in the chapter: Solid State Lasers of Sam's Laser FAQ.


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    Coherent, Inc. Compass 532-200 Green DPSS Laser (Gallery)

    This is another Coherent DPSS laser also called a "Compass" but of somewhat higher power and much more wide open construction than the 315M. This one is definitely a ring cavity design.

    (The following 28 photos provided courtesy of: Curt Graber (cgraber@fwi.com).)

    There is a more detailed summary of what can be seen in View 29 in the chapter: Solid State Lasers of Sam's Laser FAQ.



    Coherent, Inc. Compass 315M Green DPSS Laser

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    Coherent, Inc. Compass 315M Green DPSS Laser

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    Coherent, Inc. Compass 315M Green DPSS Laser - Photo Collection 2

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    Controller for Compass 315M Green DPSS Laser

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    Coherent, Inc. Compass 415M Green DPSS Laser

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    Coherent, Inc. Compass 532-200 Green DPSS Laser

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    View 28

    View 29


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    Sam's Laser FAQ, Copyright © 1994-2013, Samuel M. Goldwasser, All Rights Reserved.
    I may be contacted via the
    Sci.Electronics.Repair FAQ Email Links Page.