B&W TEK BWB-10-OEM 473nm blue Lab-Style DPSS Laser

This week, a new goodie for my laser collection arrived. I always wanted to own a 473nm laser because of the awesome, azure blue light. In comparison to this, the 445nm Nichia Diodes almost look violet.

Despite many of the units, which are apparently pulled from medical equipment, suffer from power and mode fluctuations, mine arrived lasing in a nice TEM00 mode out of the box.

The divergence is not that good, but I guess a bit of realignment should do the trick. As mine arrived without the power supply, I had a bit of fun figuring out the power supply lines on the D-SUB connector.

It turned out that pins 5&9 on the standard DB9-Pinout are connected to VDD, and pins 1,2&6 to GND. Pin 4 is the TTL modulation input, the laser will fire when this pin is pulled high. The driver board must be connected to a 5V supply with a nominal current rating of at least 4A.

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Opening the top cover reveals the guts of this neat CNI-made setup. It consists of (from right to left)

Pump Diode->Collimating Optics->Anamorphic Prism Pair->Focusing Optics->Crystal Assembly

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The crystal assembly is protected by a plastic cover. Removing this allows a look into the resonant cavity. Dominant is the big Lithium triborate (LiB3O5) crystal used for the generation of the second harmonic. The two aluminium parts hold the cavity optics (Output coupler and High reflector), the Nd:YVO4 crystal sits near the black focusing optic in the brazen plate.

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Using feedback from a photodiode, these units were stabilized for 10mW optical output. When I find some more spare time, I will try to realign the cavity and focusing optics and perhaps install a higher powered pump diode. Let’s see if I can push more than 50mW of stable powerΒ out ofΒ it. πŸ˜‰

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8 thoughts on “B&W TEK BWB-10-OEM 473nm blue Lab-Style DPSS Laser

  1. Hi, you mention the laser head is a CNI unit, do you happen to know if it’s one of their standard units?
    Did you ever mange to increase the power above 10mW?

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    • The laser head was OEM’d by CNI for B&W TEK. As this device is quite old, CNI has probably many updated versions for this wavelength in different power classes. Nevertheless, the head is well built. Either by driving the pump diode at a higher current, or realigning the laser cavity compromising the TEM00 mode may give a lot more power. Presumably, the modules were not aligned perfectly because the spectrometer requires only very low power. Currently, there are a few units circulating on ebay for 50-100 US-D, which is a very good price for such a laser.

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  2. Hello!! Great post!
    I managed to acquire one of this units myself and I intend to convert it to a handheld build.
    Do you happen to know at what temperature the crystal is set to?
    I’m trying to figure out the TEC circuit needed to keep the crystal cool.
    I only intend to use it as a laser pointer, so perhaps putting the TEC system is redundant.

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    • Hey, thanks for your comment!
      I’m intrigued about how exactly you want to convert it into a handheld build, as the assembly is quite large. Do you plan to remove the diode correction optics and cut off some of the unnecessary metal of the cavity frame? Or is it just going to be a huger handheld? πŸ˜›
      Running the TEC for the crystal is – depending on the power – probably not needed. However, I would definitely recommend having the pump diode TEC-cooled. This will not only increase its lifetime, but as the absorption band for the gain crystal is quite narrow, having the pump diode set to the right temperature (emission wavelength varies with temperature usually at ~0.3nm/K for laser diodes) can greatly increase the output power of the laser.
      I can’t tell you the set temperature because it depends on the specific diode (probably around 23C). I’d recommend the following procedure: Have a way to monitor the temperature at the pump diode by reading out the thermistor resistance using e.g. an Arduino microcontroller, and simultaneously measure the output power of the whole laser assembly (the blue light). Then hook up the TEC to a power supply, and the right temperature should be obtained when the output power is maximized.
      If you have further questions, don’t hesitate to ask.
      -Alex

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      • I do plan on removing all of the diode and diode optics! And that’s because I plan on running it off a different LD. An 808nm in a TO-18 like package, pressed in an Aixis module. At work I have access to a couple of things that let me see the IR quite well, so I’ll be able to focus the beam path right on the crystal using a three element glass lens. I only want to get 15mW max out of it since I want a pointer, so perhaps the crystal TEC isn’t necessary as you say! πŸ™‚
        I’ll follow your suggestions, I bought two TEC units (was planning on TECing both LD and crystal originally), and a couple thermistors. I’ll optimize current of LD and alignment of optics while reading out temperature and laser power output! I’ll initially use a microcontroller to optimize and then I will use a simple differential OP amp with the thermistor and a pot to set the temperature of the TEC.
        I was also reading that the LBO crystal is apparently hygroscopic, so I need to find some way to seal it off moisture…

        Do you think my approach is reasonable? I’m kinda worried that it’s not as simple as focusing the 808nm down to a very small dot (300um) and aiming it at the LBO crystal and boom 473nm out the other end….
        Hope it doesn’t end up being a huge handheld πŸ˜›

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      • I like that idea! The only thing is: All this pump correction optics isn’t just there because the manufacturer had them left over (of course). The exact dimensions and divergence angles of the pump beam on the back surface of the Nd:YVO4 gain crystal have to match the parameters of the laser cavity (mode matching). That’s what the correction optics are for. If you just use the bare diode and one lens, the lens should have a high numerical aperture and possibly a short enough focal length to achieve such a small beam waist. It depends on the exact parts used, but 15mW could be quite a challenge πŸ˜‰ Nevertheless, don’t let that put you down. As long as you keep the cavity together (not just the LBO crystal), it should be quite easy to achieve some blue light quite quickly. And keep care of the pump light polarization, the gain crystal is only gonna take a certain one πŸ˜‰

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      • Do you know if the properties that the beam must match before hitting the crystals are based on LBO itself or do they vary from crystal to crystal?
        Also do you know if the IR beam ends up collimated and with a parallel beam? or is it focused to a point? If it’s just focused to a point I have a couple lenses that can achieve that, I’ve measured the beam size at the focal point to be 100um before!

        And great! Thanks for all your advice! I purchased a few diodes, so I’m excited to try it! Hoping to make it work with the small lens, otherwise gonna have to take the whole cavity as you said! πŸ˜›

        Too bad things from china take forever to get to the Americas 😦

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      • This varies between different lasers, but this mostly depends on the cavity. And also, you should not confuse the different crystals. There are two of them inside the cavity. The “most important” one is the Nd:YVO4 crystal, into which the pump light is focused. This crystal provides the amplification and therefore sustains the laser oscillation. The LBO is the crystal which sits in the middle of the cavity, and this is only there to double the frequency (convert IR to blue). The beam properties are mostly determined by the Nd:YVO4 crystal and the cavity mirrors. The IR beam is focused down into the Nd:YVO4 crystal. It should in principle work with one small lens, especially if performance and good beam quality are not particularly important. In this case, I should be confident! πŸ™‚

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