Help purchasing a BRD laser

So for a quick experiment for my PhD research my advisor suggested me to purchase a BRD burner/reader, disassemble it, and take out the 405 nm laser diode with the optical head.

We want to do this because the diode + laser head are already adjusted to focus the beam down to the size that we need, I am assuming, something like 300-500 nm in diameter, which is the BR spot size, and we were looking at powers between 200-300 mW.

I have a few questions.

1) Can I buy a diode + optical head assembly individually, as opposed to buying the whole BR burner set up and taking it apart, figuring out the electronics, etc..?
2) How can I power it? I can probably make my own driver, but could I use just a DC power supply? I would like to be able to control the output power, but it is not necessary.
3) What recommendations do you guys have for the power/optical characteristics that I need (smallest spot size possible, I think the NA of the lenses in the BRD burners is something in the order of 0.85)

I am sort of a rookie when it comes to diode lasers, but I do work with other types of lasers (excimer, nitrogen, argon ion, Nd:YAG, fiber, dye, HeNe, Ti:Sapphire, etc). However, finding a laser source in the violet region is hard to do, at least at the powers that we need, which is why my boss suggested this approach.

A little of what I will do with the laser: I will deposit a photosensitive resist material on a Silicon substrate, expose it with the diode laser and then develop to have the features on the Si. I have been using a 488 nm argon ion laser, but the sensitivity of the photoresist to this wavelength is small, which leads to high exposure times. I would like the beam to be as small as possible to achieve small features, I am trying for something like 400 nm - 1 um features.

1) Can I buy a diode + optical head assembly individually, as opposed to buying the whole BR burner set up and taking it apart, figuring out the electronics, etc..?

Yes. Look at shops like modwerx.com or hightechdealz.com

2) How can I power it? I can probably make my own driver, but could I use just a DC power supply? I would like to be able to control the output power, but it is not necessary.

You cannot connect it straight to a battery as the voltage spike would kill the sensitive diode. Prebuilt drivers can be found at the sites I mentioned above.

3) What recommendations do you guys have for the power/optical characteristics that I need (smallest spot size possible, I think the NA of the lenses in the BRD burners is something in the order of 0.85)

The easiest way would be to install the diode in aixiz modules, which is a prebuilt diode container/lens assembly that will have adjustable focus, down to a pinpoint dot size. Again, it can be found in the sites mentioned above.

The diodes needed to get the powers you talked about is either a 6x (GGW-H20L) diode with a high-efficiency lense, or an 8x (BDR-203) with a cheap lense. The 8x is mostly only harvested from complete blu-ray drives as of now.

Thanks for your quick reply!

However, what do you mean by "adjustable focus, down to a pinpoint dot size"? I do not need to change the focus, nor to make it parallel. I just want it with the best lens possible to get the smallest beam possible. I guess I can contact the companies you suggested and ask them what spot size I can expect. Otherwise, I would want to conserve the lens that would come with the BRD burner complete assembly.

alanbrito said:

Thanks for your quick reply!

However, what do you mean by "adjustable focus, down to a pinpoint dot size"? I do not need to change the focus, nor to make it parallel. I just want it with the best lens possible to get the smallest beam possible. I guess I can contact the companies you suggested and ask them what spot size I can expect. Otherwise, I would want to conserve the lens that would come with the BRD burner complete assembly.

Click to expand...

It would be difficult to use that lense in such a way. Diodes lase is a very divergent way, like a flashlight. Hobbyist DIY'ers at this forum has always used modules, such as the aixiz module to house and focus laser diodes. If you just want the smallest dot size possible the easiest way would be to use one of those modules and then adjust the focus until you have the smallest dot possible.
Or are you talking about the thinnest continuous beam? Most diodes cannot get a thinner beam diameter than 3-4 mm, thicker than most of the laser types you have experience with.

This is the highest quality lense available for blu-ray diodes. It installs right into an aixiz module: http://laserpointerforums.com/f64/fs-405-g-1-glass-lens-mod-31-increase-vs-aixiz-22497.html

I see what you mean, but this is my understanding of how the BR disc burner / reader setup works.

You have the 405 nm diode, which is focused using an optical head (some sort of objective lens of 0.85 numerical aperture NA) that gets the beam down to the dimensions of the slots on a BR disc, which are in the range of 300-500 nm. This would be the only way the laser could read the data. This has to be the case, otherwise writing or reading could not be possible.

This makes me think that my best bet would be for now purchasing a whole burner/reader setup and taking the components apart.... including the drivers and such. That way I would ensure that I have the correct diode and optical head combination that would let me focus the beam down to that size.

A simple calculation that can be done is the following:

smallest spot size = 1.22 * wavelength / (2*NA) = 1.22 * 405 nm / (2*0.85) = 290.6 nm

So the smallest spot size with what I assume is a typical optical head assembly for the reader would be 290 nm, ideally of course. That is with values of 0.85 for NA and a wavelength of 405 nm.

I might be answering my own questions but talking to experts in the field is helping me think this through.

Another question: how hard is it to disassemble a brd reader/writer and steal the components and then make them work...?

alanbrito said:

I see what you mean, but this is my understanding of how the BR disc burner / reader setup works.

You have the 405 nm diode, which is focused using an optical head (some sort of objective lens of 0.85 numerical aperture NA) that gets the beam down to the dimensions of the slots on a BR disc, which are in the range of 300-500 nm. This would be the only way the laser could read the data. This has to be the case, otherwise writing or reading could not be possible.

This makes me think that my best bet would be for now purchasing a whole burner/reader setup and taking the components apart.... including the drivers and such. That way I would ensure that I have the correct diode and optical head combination that would let me focus the beam down to that size.

A simple calculation that can be done is the following:

smallest spot size = 1.22 * wavelength / (2*NA) = 1.22 * 405 nm / (2*0.85) = 290.6 nm

So the smallest spot size with what I assume is a typical optical head assembly for the reader would be 290 nm, ideally of course. That is with values of 0.85 for NA and a wavelength of 405 nm.

I might be answering my own questions but talking to experts in the field is helping me think this through.

Another question: how hard is it to disassemble a brd reader/writer and steal the components and then make them work...?

Click to expand...

It is MUCH easier than you would expect. A few screws and you will see that most of it is "modular." You only need the driver/control board and the sled. Your bigger challenge is going to be figuring out what (electronically) goes to what. You will have violet, red, and IR in the sled.

Maybe, with a request coming from a university, the manufacturer will be willing to provide you with a schematic. Otherwise it will be trial and error (supplemented by your knowledge).

If you need the focus required at the driver level, you are really pretty much stuck with the optics in the sled. Keep in mind the focal distances needed in a burner are very close.

Here's a couple of links so you can get an idea of how "open" they are inside

http://laserpointerforums.com/f51/pioneer-12x-blu-ray-bdr-205-a-44607.html
http://laserpointerforums.com/f51/pioneer-8x-blu-ray-bdr-203-a-36790.html

Peace,
dave

Loads of great advice already posted, But I would like to add a little.

THe Aixiz module used by many here on the forum would be the best bet for focusing the laser. I may be wrong, but as the wqvelength of the light is 405nm, I'm guessing the smallest diamiter 'spot' you can focus to is 405nm. (correct me if I'm wrong.)

Look up about harvesting the PHR. it wil give you an idea of whats inside the drive. and how to go about removing the diode. Im thinking it will be difficult to remove and effectively use the lens in the drive 'sled' Hence the reccomendations for the Aixiz module.

Si

Does it have to be focused to the absolute smallest spot size? Sounds to me like "pretty good" focus would be good enough in this case. Can't you just kind of shot gun it?

The reason I ask is, even using the sled and optics "as is", you won't get perfect focus. The optical head in a sled is undergoing constant adjustment; perfection can't be maintained at these scales and speeds for long, so the head is constantly being moved up and down to compensate. I would think (and this is a non-professional opinion, mind you,) that unless you can write some sort of software to control the sled in its entirety, you can't hope to succeed in this fashion.

daguin said:

It is MUCH easier than you would expect. A few screws and you will see that most of it is "modular." You only need the driver/control board and the sled. Your bigger challenge is going to be figuring out what (electronically) goes to what. You will have violet, red, and IR in the sled.

Maybe, with a request coming from a university, the manufacturer will be willing to provide you with a schematic. Otherwise it will be trial and error (supplemented by your knowledge).

If you need the focus required at the driver level, you are really pretty much stuck with the optics in the sled. Keep in mind the focal distances needed in a burner are very close.

Here's a couple of links so you can get an idea of how "open" they are inside

http://laserpointerforums.com/f51/pioneer-12x-blu-ray-bdr-205-a-44607.html
http://laserpointerforums.com/f51/pioneer-8x-blu-ray-bdr-203-a-36790.html

Peace,
dave

Click to expand...

Awesome, thank you so much for the diagrams, dave. I actually forgot to read the replies and went ahead and took apart an old CD player to see how it works, and for practice purposes, and I found a similar type of sled configuration. The diode is different, but for the most part, the optics and focusing system is the same. Also, the detector is different. The only reason we have BD systems now is because the 405 nm laser hadn't been invented until 3-4 years ago, recent developments in the semiconductor industry made this possible. The diode is actually made out of InGaN, which is one of the materials we are doing research on.

IceNoise said:

Loads of great advice already posted, But I would like to add a little.

THe Aixiz module used by many here on the forum would be the best bet for focusing the laser. I may be wrong, but as the wqvelength of the light is 405nm, I'm guessing the smallest diamiter 'spot' you can focus to is 405nm. (correct me if I'm wrong.)

Look up about harvesting the PHR. it wil give you an idea of whats inside the drive. and how to go about removing the diode. Im thinking it will be difficult to remove and effectively use the lens in the drive 'sled' Hence the reccomendations for the Aixiz module.

Si

Click to expand...

The ideal spot size you can get comes from that resolution formula I posted above, but that is just a formula that tells you what can you resolve with a certain wavelength and a certain lens, meaning, it is the ideal case situation. For practical purposes, 500-1000 nm should be easily achievable with the existing optics in the system.

Also, thank you for the recommendations to use the Aixiz module, that should work. Below I will explain what I am planning to do and if it is feasible.

proud2deviate said:

Does it have to be focused to the absolute smallest spot size? Sounds to me like "pretty good" focus would be good enough in this case. Can't you just kind of shot gun it?

The reason I ask is, even using the sled and optics "as is", you won't get perfect focus. The optical head in a sled is undergoing constant adjustment; perfection can't be maintained at these scales and speeds for long, so the head is constantly being moved up and down to compensate. I would think (and this is a non-professional opinion, mind you,) that unless you can write some sort of software to control the sled in its entirety, you can't hope to succeed in this fashion.

Click to expand...

Pretty good focus is all I need. You are correct about the focusing system, it is an actuator system that is controlled by the actual photo receiver, and making a program to control it would be, in nice terms, a total bitch.

I will be posting an additional thread, with more questions and what I am planning to do. I will post the link in a second, you guys have given me awesome advice. Much appreciated!

-Alan


EDIT: err, I am actually posting it on the same thread. Screw clogging up the forums.

So far these are my two options:

a) Get an Aixiz module, heatsink, drivers, etc and put my own lens, diode and then make it work. Very useful type of setup, probably has been done before and I could have a modular system that is easy to setup. The drawback, the optical system has to be adjusted, and that means more parameters I have to work with. Doable, but this leads me to option b;

b) Get a whole sled type system, like this one from Modwerx. I then have two options. I could tap into the electronics and use the integrated driver circuits (which I am assuming are there) and make the laser work. This is hard to do unless I have diagrams of what the circuits are and what each component does, and even like that, it would be a bitch. However, I could just keep the whole sled setup because what I am interested in is the actual lens/diode housing assembly because it has already been optimized to give you the smallest possible size. I would then just keep the housing/sled as is, hack into the laser diode by removing all connections and using an external driver/power supply to just give power to the laser, which is very doable. I might also have to remove the diffraction grating (usually the "lens" that is right next to the diode, used to split the beams and for tracking purposes and multi track reading). This way, I would have the optics already setup, and all I would need to worry about is the drivers. This is where you guys come in, let me know of some links where I would be able to find a suitable driver for that type of laser I posted above in the link the PHR-803T. My only other question is would I need a heatsink, or is the actual sled setup be optimized already for that?

Tell me your thoughts. I <3 the internet, btw.

Cheers,

Alan

Hey Alan,


If 200-300 mw is what you're looking for, then the PHR-803T isn't a good choice. That diode would die too soon at that power range. If I were you, I'd go with either the GGW-H20L for 200-250 mw, and if you need to go higher, then a 8x diode.

Just my 2 cents.

Thank you Tim; you are right but at least for starters I plan to use the PHR-803T.

Also, my question is if I use the sled that already contains the PHr-803T diode in it, do I need an additional heatsink? I would assume it already is protected against heat. Furthermore, if I were to get an Aixiz module, will I need to get a separate heatsink? I will probably purchase a few items from modwerx.

Is this photoresist a regular commercial resist, or is it something exotic? Because exposing regular commercial resists in such a manner is likely a waste of time.

Also, why spot size do you really need? Is your spot size the determining factor for your feature size in your PR pattern? If tiny spot size is truly important to you, then you need to skip the Aixiz lens and go to better optical components.

I'm kindof lost on your application here. If this is trying to pattern a wafer using commercial resist, you're reinventing the wheel in a difficult way. If this is something more exotic than typical wafer patterning, or you're using some sort of a photoresist that is in some way decidedly different than common, commercial resists, then it might make some sense. You're definitely right that there is a shortage of light sources in the violet range. For high resolution patterning, another common method is laser holography using a 325nm HeCd laser.

Can you tell any more about your application? I work in the semiconductor field, and have experience with photolithography, feel free to pm, I can be discrete.

pullbangdead said:

Is this photoresist a regular commercial resist, or is it something exotic?

Because exposing regular commercial resists in such a manner is likely a waste of time.

Click to expand...

It is more of an enhanced commercial resist. It is called SU-8 and it is enhanced with photoinitiators and coinitiators that allow for absorption in the 400-500 nm range, in which the resist would normally be transparent. The process that I need to do cannot be done with regular masks, otherwise, I would be doing regular photolithography. The other method I was using to fabricate my structures was using an electron beam lithography system, but it was just too costly and time consuming.

Gotcha. Figured there was something exotic going on.

Sorry for editing so majorly, I should fully think-out my posts before posting, instead of editing so much.

By "regular masks", do you mean it can't be done with contact aligners? Or can't be done with projection as well? (By projection, I mean like a stepper, non-contact, focusing, still using conventional lithography light sources).

And with the laser, are you planning on scanning the laser to form the pattern, or projecting through a mask?

Uhm, from your posts, i suppose you're speaking about making very thin elements in photolitography field, like interference masks and similars, and that you are going to use or build some sort of precision plotter (i can be wrong, thinking this, if so, my apologies)

But you have also to considerate that, using a so precise focusing system, you also need a feedback system and an active focusing system, cause any variation of distance between the laser assembly and the plate, change your focus .....

Basically, the same exact problem that the ones that have invented the CD / DVD readers had to manage at the start ..... any oscillation from the disk had to be detected in real time from the reading sensor, and compensated in real-time ..... (for this the lens of the readers/burners is mounted on a mobile system) .....

So, basically, you can adapt an already mounted sled, for this ..... think about this: a sled from a burner is an already assembled focusing / beamshaping unit, including diffraction and separation gratings, prisms, focusing lenses, splitters, and a reading / quadrature photoelement, already aligned and matched (I mean ..... the sled is not just a focusing lens ..... the beam become partially FAC-corrected, diffracted for purify and eliminate interference franges, shaped, prefocused, reflected on the disk, then the reflex from the disk become reflected again through another focusing element collimated with an optical chip that not only read the data, but also detect any defocusing or distance variation, and send signals to the driver for correct it in realtime ..... if you have to build, and overall align, all this alone, it's an almost impossible challenge, where instead in the sled is already done )

So, why don't use it, just making brand-new just the driver / focusing driver / feedback circuit ? ..... not a small or easy work, but muuuuuch more easy than the alignment part