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Natural Science Forum / Physics / Optics / January 2008DIY red burning laser (DVD diode)
Just completed my second DIY laser. These really are easy and fun to build. I'm using a Sony 16x DVD burner LD. These can be reliably pushed to between 200-300 mW output (how long they will last is another story, they are rated at 80mW CW, this is using about 140 mA of current. Most people are driving these with between 200-300 mA of current. You can get the diodes here for about $20.00/each: http://sales.stonetek.org/index.htm They also sell inexpensive driver kits and housing for these diodes. Assuming you've got some basic electronic skills, know how to solder and use a multimeter, you can build one of these for $35-40 in parts. See this thread for more info on a simple DIY driver circuit: http://www.laserpointerforums.com/forums/YaBB.pl?num=1185701612 I built the driver using radioshack parts- the parts came to about $20.00. I'm using a Meredith LDC1 collimator and mounting block for the optics and heatsink. I'm using the acrylic lens which makes for a tight focus. These parts cams to about $30.00 see: http://www.mi-lasers.com/cgi-bin/shopper.cgi?search=action&keywords=diode_optics Finally the diode was another $20.00. So the parts came to $70.00, plus the work of throwing it together. The Meredith housing is meant for 9mm diode cans (the Sony is 5mm) so it's necessary to press fit the sony diode into a little brass adapter. However I found that while focusing the Meredith assembly the diode would squirm and rotate, not staying centered in the optical path. So I ordered some thermal epoxy to fix this: http://www.arcticsilver.com/arctic_silver_thermal_adhesive.htm After getting the diode snug and flush in the adapter I applied a few dabs of the thermal epoxy to get assure good heat flow from the diode the the adapter. The adapter in turn I then thermal glued to the back of the case housing, centered. This worked perfectly, I can now focus the diode and it stays put. The Meredith lens will focus from infinity to less than 8 inches with about 180 degrees of turning. I metered this one up to 240mA. The consensus at LPF is to keep the current at or below 250 mA unless you've active cooling or a large heatsink. 240 mA of current will likely put the optical power over 150 mW. The pointer will pop balloons out to over 40 feet and light wooden safety matches out to 7-8 feet. With the focus adjusted up close you can burn a lot of things. Very impressively bright at night. Some pictures... Testing the regulator circuit in the breadboard. I pushed the diode up to spec (~140 mA of current) which puts it around 80 mW output. http://www.fractalfreak.com/wx/DIY_red2.jpg Completed laser brick: http://www.fractalfreak.com/wx/DIY_red2_5.jpg Metering the current while adjusting the rheostat after getting things working. Unfortunately I was only able to meter up to 200mA of current before the pot maxed out. Another 10 ohm resistor allowed me to get to 240mA. I stopped here. I'm interested to see how long the laser will last 100mA over spec. http://www.fractalfreak.com/wx/DIY_red2_1.jpg Closeup of the innards. Radioshack parts + box, 4 AA nimh batteries, diode in Meredith housing+ optics. http://www.fractalfreak.com/wx/DIY_red2_4.jpg First task, burning a hole through the top of the case from 8 inches., http://www.fractalfreak.com/wx/DIY_red2_3.jpg Projecting the spot onto the ceiling of the bathroom. It's that bright. http://www.fractalfreak.com/wx/DIY_red2_6.jpg Overall I'm quite happy with the pointer. Curious to see how long it hold up before the diode pops. -Eric boo@fractalfreak.com wrote in news:28a46d90-4168-4ae0-93dc- 62058afb6df0@q39g2000hsf.googlegroups.com: > Overall I'm quite happy with the pointer. Curious > to see how long it hold up before the diode pops. Not long, if you're seriously trying for between 200 and 300 mW out of a diode rated for 80 mW CW. People have tried for months and failed. I've watched their discussions, and tried some diodes myself. Unless the diode is rated for at least 120 mW CW, you won't reliably get over 220 mW and you'd be lucky if it lasted a week. No-one's going to buy on the strength of an overinflated claim, no matter how well it appears to be backed up with apparent research. After all, they need ask just ONE question: If you can really do this, why didn't the makers of DVD drives also notice and start selling 24 speed DVD writers? They haven't, and there's a damn good reason why not. They can't do it. And if they and the diode makers can't push this performance, no-one else can, certainly not with the same diodes, anyway. Unless you have some totally unique supply, the likes of which the big industries would pay millions to access, you can't do it, and there's no reason for anyone to believe that you can. > If you can really do this, why didn't the > makers of DVD drives also notice and start selling 24 speed DVD writers? Actually, I just checked, they have, just... HP have one now. But if you can reliably get 200 to 300 mW CW, you could be punting out 32x, maybe even 40x write speed drives. The current 20x drive diodes can barely reach 300 mW in their pulse ratings, so CW is obviously out of the question. Here's a datasheet for the diode (sony sld1236vl): http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/197026/ETC/SLD1236VL.html On Jan 9, 7:02 pm, b...@fractalfreak.com wrote: > Here's a datasheet for the diode (sony sld1236vl):http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/197026/ETC/SLD1236V... The markings on the diode (JL) lead me to beleive that is may be this one: http://www.zet.biz/Laser/data/SLD1239JL.pdf > On Jan 9, 7:02 pm, b...@fractalfreak.com wrote: > > > Here's a datasheet for the diode (sony sld1236vl):http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/197026/ETC/SLD1236V... > > The markings on the diode (JL) lead me to beleive that is may be this > one:http://www.zet.biz/Laser/data/SLD1239JL.pdf Thanks for the heads up. Where'd you get the diodes from? These 5mm cans are tiny, but looking at the side of my two spares I see, two lines, "5HJL" "0058" So you may be right. Eric >> On Jan 9, 7:02 pm, b...@fractalfreak.com wrote: >> [quoted text clipped - 14 lines] > > Eric Neither of those diodes will do what you claim. They're both exceeded by the Rohm diodes that overwhelmed eBay for a while, and the Rohm's are exceeded by the newer Opnext diodes. And none of these can do what you claimed. Ignore all this if you like, but it won't go away. On Jan 10, 11:15 am, b...@fractalfreak.com wrote: > > On Jan 9, 7:02 pm, b...@fractalfreak.com wrote: > [quoted text clipped - 12 lines] > > Eric Ooops, however now that I look at the product code it's listed as "xxKL".. not "xxJL" > Ooops, however now that I look at the product code > it's listed as "xxKL".. not "xxJL" Yes, I have seen this, but you you think the 'VL' diode would have marking 'JL' and the JL diode have marking 'KL'? They do make a KL diode and it's possible that figure was simply copied from that datasheet, but not changed to JL. Either way, lostgallifreyan is right. I still have about 90 Rohms that are trickling away on ebay and once they are gone I won't lament their passage into the hands of experimenters that burn the diodes as much as their electrical tape and matches. It's even possible some may end up seeing real service.. one can only hope. > > Ooops, however now that I look at the product code > > it's listed as "xxKL".. not "xxJL" [quoted text clipped - 9 lines] > much as their electrical tape and matches. It's even possible some > may end up seeing real service.. one can only hope. real service" lol Don't see what the problem is. Adjust the rheostat accordingly. Sounds like at about 150mA these diodes would last. That's still a 80-100mW laser - not bad for $30-40. It's amazing they can be pushed so far overspec and survive at all. Eric boo@fractalfreak.com wrote in news:2940ef06-82d4-46c3-b00c- 08b9581b11cf@f10g2000hsf.googlegroups.com: > It's even possible some >> may end up seeing real service.. one can only hope. [quoted text clipped - 5 lines] > would last. That's still a 80-100mW laser - not bad > for $30-40. Try 125 mW for the Rohm's (in a clean supply, and perhaps some TEC if you really want the long haul and a slight wavelength shortening, useful as apparently they're already around 655 (most makes tend to be longer than 658 rather than shorter)). But you're right, that's by far the best way to go. Most people will want them adjustable anyway, and won't want the full brightness all the time. I'm thinking of using a simple external switch, to allow a very tiny module to be built. Too small for fancy drive, but still with very good protection added. > It's amazing they can be pushed so far overspec and > survive at all. True but you enter the chaotic realm the moment you push beyond around 125 mW CW, on ANY of the current DVD diodes, no exceptions. Even the Rohm's might do 300 mW for a short time but most won't, and I could burn the rest so fast I'd have no meaningful plot of the expected performance even after getting through 200 of them. The later Opnext diodes seem to be cleaner in their modes at mid to high power, but even those will be chaotic at above 150 mW. That's why Marconi (on PL, with the MaxYZ modules) can keep a good position by using narrow stripe multimode diodes. I don't know where else those diodes will start to appear from wherever he gets them from, but that's the place to look for brighter diodes for show gear. He won't give up the detail, I can't compete with that, so it's like a chess game in which I can't get out of check, even though it's not checkmate. If I was limited to a chessboard the only thing to do would be resign, but being real life, there's always the hope of turning resources some other way. I decided to turn my diodes into parts for drivers, and tooling to design and make PCB's. Much harder to be caught on a new stalemate that way. > which I can't get out of check, even though it's not checkmate. That looks daft, not what I meant. You know, the kind of end game where you can GET out but never STAY out... > True but you enter the chaotic realm the moment you push beyond around 125 > mW CW, on ANY of the current DVD diodes, no exceptions. Even the Rohm's [quoted text clipped - 3 lines] > their modes at mid to high power, but even those will be chaotic at above > 150 mW. (...) How about DVD burner LDs harvested from 20x drives .. would it possible to get reliable operation at 200mW? (by reliable I mean at 100+ hours for use in a pointer) I wish I knew more about how these LDs are constructed, and what the limiting factors are to getting higher power single mode LDs. You are right that it's very hard to find any single mode LDs above about 150mW. I believe much of the early work and trade secrets to getting reliable higher power LDs revolved around preventing COD to the end facets. Is the limiting factor a fundamental one, that is the optical power density at the facets inevitably causes it to degrade, or is it more a manufacturing problem - reliably creating the die with very few crystal defects ?? Eric boo@fractalfreak.com wrote in news:70c5d43e-a2bb-4605-b095- 4aa138297994@k39g2000hsf.googlegroups.com: > How about DVD burner LDs harvested from 20x drives .. > would it possible to get reliable operation at 200mW? > (by reliable I mean at 100+ hours for use in a pointer) Doubtful, because it's so hard to get the small extra power beyond current levels, that makers have resorted to leaving out the cans and the windows to prevent losses (and presumably save money. The loss of physical protection for the die means there's just more that can go wrong. With drives people will likely update within weeks or months, they don't care much. > I wish I knew more about how these LDs are constructed, > and what the limiting factors are to getting higher power > single mode LDs. You are right that it's very hard to find > any single mode LDs above about 150mW. I believe much > of the early work and trade secrets to getting reliable higher > power LDs revolved around preventing COD to the end facets. The facets are cleaved and polished. There's no coating, it's difficult to put one there, so the surface of the crystal is the weak point. It's not very durable, and the lack of a can and window on the 20x writer diodes doesn't help at all... Increased purity of materials is about all they can do, and even then, dopants don't make precise crystal lattice fills, there's always some flaw there. To change that there would have to be some way to precisely build it up like a lego model, atom by atom. That is doable, but not feasible. Not really doable either, it would take too long, some better way to mass produce them will be found before one diode could be built that way. > Is the limiting factor a fundamental one, that is the optical > power density at the facets inevitably causes it to degrade, > or is it more a manufacturing problem - reliably creating the > die with very few crystal defects ?? That will take more knowledge than mine to asnwer well. I tried, but it's not a very useful answer. > Doubtful, because it's so hard to get the small extra power beyond current > levels, that makers have resorted to leaving out the cans and the windows > to prevent losses (and presumably save money. The loss of physical > protection for the die means there's just more that can go wrong. With > drives people will likely update within weeks or months, they don't care > much. Yes I imagine with the 'open can' design dust might be a problem if it were to accumulate. > The facets are cleaved and polished. There's no coating, it's difficult to > put one there, so the surface of the crystal is the weak point. It's not > very durable, and the lack of a can and window on the 20x writer diodes > doesn't help at all... Increased purity of materials is about all they can Quite certain you're wrong on this. Facet passivation is done to all high power LDs to slow/prevent COD. It's likely one of the many proprietary manufacturing steps we know nothing about You wrote earlier: (...) >but you enter the chaotic realm the moment you push beyond around 125 >mW CW, on ANY of the current DVD diodes, no exceptions. Even the Rohm's [quoted text clipped - 3 lines] >their modes at mid to high power, but even those will be chaotic at above >150 mW. You talk here about entering chaotic modes/realm once the power gets above about 150mW. Can you explain what you mean by this and how you're evaluating this? Eric >> The facets are cleaved and polished. There's no coating, it's >> difficult to put one there, so the surface of the crystal is the weak [quoted text clipped - 5 lines] > high power LDs to slow/prevent COD. It's likely one of the many > proprietary manufacturing steps we know nothing about Didn't know about that. Last I heard, there was no way to prevent COD with a coating, only to prevent oxidisation. Google does show COD related results for Facet passivation though. http://www.freepatentsonline.com/4337443.html I tried reading some of that but it goes beyond my grasp quickly. It looks like there's a way to set the thickness and the refractive index to prevent an AR coating forming, in turn preventing a rise in threshold current. That allows effeciency and higher maximum output. Probably what Opnext have been doing. > You wrote earlier: > (...) [quoted text clipped - 9 lines] > power gets above about 150mW. Can you explain what you > mean by this and how you're evaluating this? Rohm diodes visibly mode hop at anything above 125 mW, some samples lower. If you google for holography and DVD diodes, you'll find a few pages discussing this and other diodes. Rohm's were ok below around 50 mW, though still noisy. Other diodes were better, but I didn't see any report of a diode doing well beyond about 150 mW, so I think it's safe to assume that you can't predict performace above those levels for CW in single mode diodes, especially given that few if any are rated beyond 120 mW CW. > b...@fractalfreak.com wrote innews:8648a425-9fcd-4a75-8d60-facb022f68d3@e23g2000prf.googlegroups.com: > [quoted text clipped - 41 lines] > you can't predict performace above those levels for CW in single mode > diodes, especially given that few if any are rated beyond 120 mW CW. I'm running a Mitsubishi 636 mM at 250mA (They're rated at 300 max) and it seems quite happy. (It's 150 mW output) I did pop one though due to an electrical error (dangling wires) and at 295 USD ea I about crapped .. but I'm still at it now..(tho more carefully).. stevebraddock@swva.net wrote in news:343af5a3-08c8-461c-9c81- 606148d63a4b@e10g2000prf.googlegroups.com: > I'm running a Mitsubishi 636 mM at 250mA (They're rated at 300 max) > and it seems quite happy. (It's 150 mW output) I did pop one though > due to an electrical error (dangling wires) and at 295 USD ea I about > crapped .. but I'm still at it now..(tho more carefully).. Special diode? No DVD type for sure, maybe for other purposes needing high visibility. Is it single mode? The price is bearable, just, but I won't try for one till I have something worth getting them for. Well beyond my budget for general experiment.. > Here's a datasheet for the diode (sony sld1236vl): > http://pdf1.alldatasheet.co.kr/datasheet-pdf/view/197026/ETC/SLD1236VL. > html You still don't get it. Pulse mode! http://www.sony.net/Products/SC-HP/cx_news/vol37/lsd1236vl.html Look there if you still refuse to believe, that's Sony's own. > b...@fractalfreak.com wrote in news:28a46d90-4168-4ae0-93dc- > 62058afb6...@q39g2000hsf.googlegroups.com: [quoted text clipped - 7 lines] > is rated for at least 120 mW CW, you won't reliably get over 220 mW and > you'd be lucky if it lasted a week. lol. We'll see. The reason these diodes can be pushed to 200-300 mW w/out getting COD is they're designed to be good up to 250 mW, but only pulsed, not CW. Apparently if well heatsinked and not pushed with more than 250 mA of current (which should give an output of at least 180mW). they have a reasonable life as a pointer. Look at the discussion over at LPF. People are reliably driving these diodes with 300mA of current and using them for pointers and they are not dropping like flies. Getting about 200mW while consuming 300mA of current is not unusual for the Sony 16x diodes. I'm not going for 200+ mW, I'm hoping for 150+ mW and using 240mA it should be at least that. I was hoping by using thermal glue to enhance the thermal path for heat to exit the diode I might enhance its life a bit. I don't usually leave it on for more than a couple of minutes. I'll be keeping track.. even if it lasts a few 10's of hours that a lot of use from a pointer. Fun while it lasts. boo@fractalfreak.com wrote in news:cc899bcc-0dde-4694-a1a8- 21f6125654b2@k39g2000hsf.googlegroups.com: > Look at the discussion over at LPF. People are reliably > driving these diodes with 300mA of current and using > them for pointers and they are not dropping like flies. When people want to boast about their successes, they're not going to shout about their failures. I don't care about a forum of people playing, if this were a real claim, it would be made my the industry that makes diodes and drives! They don't leave the big stuff for newbies to find. All we get are crumbs from the great table, and don't ever think otherwise. An analogy: amateur astronomers sometimes find things the big scope operators don't. But they do it by a lot of persistence, and probably a great deal of experience at using their limited stuff. NO-ONE who just comes to it with a few parts scrounged off some related optics is going to do it just because it seems new to them. They wouldn't even understand enough about what they saw to know it in the extremely unlikely event that they did discover something new. When something is new to us, we can enjoy its newness, but it takes serious folly to assume that no-one else has seen it, or that we have something truly new. All this playing with diodes is meaningless except to establish the best conditions for prolonged life at high power, and all that wouyld ultimately do is sharpen the accuracy of the manufacturer's MTTF data, which VERY few people even get to see. And even that depends on rigorous recording and controlling of conditions, none of which is happening in these kinds of tests. It's like a fantasy world where people come back from the edges of the oceam screaming about the wonderful new monsters they've found, while not realising that that world has already been thoroughly mapped. > b...@fractalfreak.com wrote in news:cc899bcc-0dde-4694-a1a8- > 21f612565...@k39g2000hsf.googlegroups.com: [quoted text clipped - 8 lines] > drives! They don't leave the big stuff for newbies to find. All we get are > crumbs from the great table, and don't ever think otherwise. (...) Good grief what's your problem? You clearly have some sort of chip on your shoulder. Look, NOBODY is saying these parts are going to last anywhere close to their MTTF driven the way they are. Who cares, it's a *pointer*. Generally, as a pointer, it's not on for more than a minute of two at a time, if that. Even if the part only lasts 10 hours that's hundreds of "uses". If I had purchased one of the new Hitachi diodes (640nm @ 150mW)... http://www.photonic-products.com/products/laserdiodes_visible/hitachi_visible_ds /hl6385dg.pdf (for example) I would make every effort to make certain the part was driven at spec. But then for the price of one of these cans I could literally order dozens of the Sony diodes at $20.00 each. The parts for my pointer cost more than the diode. If the diode pops.. <shrug> I can just put another one in the Meredith assembly. Where else are you going to find a visble single mode diode that can be pushed this hard for $20.00?? For the average experimenter, nowhere. I'd love one of the new high powered 640nm Hitachi cans, but there's no way I'm going to drop hundreds to thousands on a single diode. Guess my point is, lighten up. It's a $20.00 diode, even if it lasts 10 hours I think you get at least $20.00 worth of value, YMMV. Eric >> b...@fractalfreak.com wrote in news:cc899bcc-0dde-4694-a1a8- >> 21f612565...@k39g2000hsf.googlegroups.com: [quoted text clipped - 14 lines] > Good grief what's your problem? You clearly have some sort > of chip on your shoulder. Just urging a bit of reality. The net is already full of unjustifiable claims without me standing by and letting people fall into traps made by wishful thinking. The only 'chip on my shoulder' that exists is the annoyance of having been there already, seeing people making again, and again, the same mistakes. If people beleive that crap the only way I can compete to sell stuff is to start lying! As I have NO intention of going there, I will defend what I know of the truth. I think with all of your extra bits needed that your $10 laser is going to add up to about $6,500 Go back to launch pad my freind >http://www.mi-lasers.com/cgi-bin/shopper.cgi?search=action&keywords=diode_optics > [quoted text clipped - 6 lines] >assembly the diode would squirm and rotate, not staying centered >in the optical path. Thanks for your post, Eric. I've been accumulating a few parts, thinking that I'd eventually put together a small red or IR laser for some experiments (not for burning, but high power if possible). Sounds like Meredith has some useful mounts and lenses. The diodes that I found are -supposed- to be 150mw, but I haven't been able to find any data on them. Part number is J8Y4M4C. Anyone know anything about it? The diodes are packaged with a lens that says "Achromatic Lens, 12mm x 6mm, AR Coated." If this gets to be a pain, I'd just buy a completed assembly somewhere, if they exist. Looking for something compact with about 150mw or more. Ideas? > If this gets to be a pain, I'd just buy a completed assembly > somewhere, if they exist. Looking for something compact with about > 150mw or more. Ideas? eBay. Cheap too. So cheap it's not worth trying to build any to compete with the low cost, unless you want the fast lane to a miserable life. Far better sense to sell diodes in small quantity from bulk stock to hobbyists. I know, I've tried both, and the raw diode selling was a better ride, by an order of maginitude at least, once I'd had all the fun I wanted from trying to build modules. I'll still try, I have a couple of ideas whose cost to build is so low it could be viable, but it's not that likely. Unless you're aiming for top spec performamnce, to supply a market willing to pay $$$ for it, forgot it. That cuts both ways, just as it's not economical to make modules for cheap sales unless you have access to a large scale Chinese manufacturing base, it's becoming harder to find any because makers are realising this. It's easier to find raw diodes. People are waking upo to this too. The only thing I have, is I woke up to it a few months sooner than most. > >http://www.mi-lasers.com/cgi-bin/shopper.cgi?search=action&keywords=d... > [quoted text clipped - 22 lines] > somewhere, if they exist. Looking for something compact with about > 150mw or more. Ideas? I've had good luck with the Meredith assemblies. I've got some pointers I made a couple of years ago (15-20 mW, 635nm) that are still going after hundreds of hours of use, using the Meredith assemblies. Other than that I'm not familiar with your part. "lostgallifreyan" does have a good point -- if you expect to get a reasonable life out of the diode you need to take care not to drive it over spec. Eric > Other than that I'm not familiar with your part. "lostgallifreyan" > does have a good point -- if you expect to get a reasonable life > out of the diode you need to take care not to drive it over > spec. This is an area I recently had a dabble in. Some diodes are analogue and will keep increasing output depending on how much voltage/current is shoved up them to the point when they will of course die. Others have a quasi digital flavour and after a certain amount of current is put through them they refuse to take any more. There is a definite 'point' when this happens and easily recognised as the (Rohm) diode dims slightly. The former I have seen in Optnext and the later in Rohm. I am NOT experienced in any way with diodes. Just my observations after blowing a few up. To this end I'd have thought that a dabbler would be better off playing with Rohms as they are so much harder to kill. > This is an area I recently had a dabble in. Some diodes are > analogue and will keep increasing output depending on how [quoted text clipped - 11 lines] > after blowing a few up. To this end I'd have thought that a dabbler > would be better off playing with Rohms as they are so much harder to kill. do you mean like this: http://hacylon.case.edu/laser/SLD1239JL.jpg this is one of the diodes from the OP's link. >> Other than that I'm not familiar with your part. "lostgallifreyan" >> does have a good point -- if you expect to get a reasonable life [quoted text clipped - 17 lines] > would be better off playing with Rohms as they are so much harder to > kill. True that Rohm's are harder to kill outright. Several buyers commented favourably on it, to the point where I might be able to slightly extend a claim for them. I won't though. They mode hop frantically at over 125 mW CW, starting anywhere on the scale, That's what accounts for the discontinuous output scaling. The best we can get is a fit between the application and the edge of the chaos. This is difficult, and is probably the main reason why the Rohm diodes flooded the market. They are good, but just too unpredictable to base any mass marketed device on. And Rohm have plenty of other diodes in their arsenal too. At the top end of the scale you won't see then dim, they'll just die. :) And they won't always do it at times and in ways you can predict. One might die hard, another will wimp out during a long and modest uptime. Opnexts around 2 years ago could be pushed more consistently to max, probably still true. The telltale was a loss of speckle, a gentle breakdown of coherence even at close range. You could see it by eye, if projected across a matt black surface. I'm not sure that newer ones reveal that same clue though. If so, you can back off on the drive on seeing that effect, and be sure you're at peak CW drive. I don't know why that effect existed though, I only know it did exist, having pushed a few to destruction carefully to verify it. Might have gone on with them but they were EXPENSIVE to me at the time, £50 a go, and I discovered retroreflection damage the hard way. Thought it was static, eleiminated everything by careful design and construction, before proving that even low level reflections could kill them during overdrive. No-one was talking about that, not the seller, not the maker, and I don't know if there was even anything in the LaserFAQ about it then. I think that put a lot of people off making modules, especially those that combined beams. Either diodes were consistent and too costly, or cheap and too inconsistent. Not sure if anyone's really cracked that yet. I blew up two Optnext in the space of 2 weeks at £20 a go and almost chucked the whole lot in. Got a set of 5 Rohms from LG three months ago expecting to blow a few more up but still haven't managed to kill one yet despite severe abuse and runs of up to 4 hours CW. > I blew up two Optnext in the space of 2 weeks > at £20 a go and almost chucked the whole lot in. [quoted text clipped - 3 lines] > managed to kill one yet despite severe abuse and > runs of up to 4 hours CW. Nice. I nearly gave up, when I spent £500 (which was very hard to get for me, let alone risk spending on 10 Opnext 80 mW diodes, only to learn the hard way about the retroreflection, which cost me 4 of them before I'd proven it wasn't some other cause). Fortunately I could get enough for just TWO modules built at that time, to recover all my losses. Next big diode spend was >£500 on 200 Rohm diodes. Luck break, last the guy had, I just missed an offer of 500, a German guy bought 2000. I suspect he realises he might have bought a few too many by now. By the time he shifts them, no matter how he does it, their value will fall low enough to be a problem for him. I expect them to hold their value for another year, at most, and he's certainly not punting out lasers or diodes at a rate that will sell out in that time. If you or anyone else want some more Rohm's, I'll sell a few more. Got my sights on some deep-cycle batteries, I want to add them to some solar panels I just bought... I also have some polarised beam splitter cubes, 5 mm, AR coated for red wavelengths, not as efficient as Edmund Optic's cubes, but they won't cost a couple of hundred quid, either. I also have several small efficient TEC's with metallised pre-tinned surfaces, to run off 3.3V and pump up to about 3.5 watts. > I just bought... I also have some polarised beam splitter cubes, 5 > mm, AR coated for red wavelengths, Tell me. What makes the cubes frequency specific? >> I just bought... I also have some polarised beam splitter cubes, 5 >> mm, AR coated for red wavelengths, > > Tell me. What makes the cubes frequency specific? Nothing. That's why you optimise the transmission for one wavelength, at the expense of others. At least this way, red light gets through cheaply, with little loss. Without the coating, other clours might get through better, but all will lose more that red would on these. These PBS cubes were made specifically for combining red diodes. |
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