Need help to create a 200mW+ 405nm laser source for a mask writing application

[Mttremblay]

Hello, All! I am new to this forum. I am a service and support engineer for a manufacturer of laser based masked writers. I am trying to find a replacement for a 413nm, 150mW KrI tube laser source by combining the output of two 405nm, 100mW laser diodes. My only problem is that I am not an optical engineer by training - I am actually a chemist. A silver halide chemist, to be specific. Yes, it was a strange, twisted path that brought me to where I am. In any case, I have been told that it would be possible to combine the output from two diode lasers using a PBS cube. The problem I can see is with stability and noise, beam power distribution, beam divergence, and polarization. Since our tools use accousto optic devices for beam control, polarization is a significant issue. Thank you for your help and patience with a noob!

[swamidog]

you can easily get well over 200mW from a single 405nm diode (500mW is common).

typical 405nm diodes are single mode have reasonable polarization and beam specs.

a sf-aw210 diode will give you 200mW+ and run you 15-20$
a BDR-SO6J (12x) will do 500mW+ and run you about 50-60$

one potential supply is here: http://www.modwerx.com/shop/index.ph...uevogtu7ikj0j4

i recommend you pick up a flexmod driver to power the diode: http://hacylon.case.edu/ebay/laser_diode/FlexModP3.php

you will also need a heatsink/mount and lens assembly. i'm sure someone else will chime in on those.

Hello, All! I am new to this forum. I am a service and support engineer for a manufacturer of laser based masked writers. I am trying to find a replacement for a 413nm, 150mW KrI tube laser source by combining the output of two 405nm, 100mW laser diodes. My only problem is that I am not an optical engineer by training - I am actually a chemist. A silver halide chemist, to be specific. Yes, it was a strange, twisted path that brought me to where I am. In any case, I have been told that it would be possible to combine the output from two diode lasers using a PBS cube. The problem I can see is with stability and noise, beam power distribution, beam divergence, and polarization. Since our tools use accousto optic devices for beam control, polarization is a significant issue. Thank you for your help and patience with a noob!

[allthatwhichis]

Hey... welcome to PL. I am NOT an expert at this type of thing but I suspect the 405nm diode output is infinitly noisier and less stable than the gas laser you are trying to replace. There are more powerful 405nm diodes out there; to combine two diodes with a PBS you will take two diodes with opposite polarizations and end up with a beam with random polarization. By using one, say 200mW 405nm, diode it would only be polarized in one direction. The other issues can probably compensated for with optics if you are using only one diode.

Have you thought about a HeCd gas lasers? I think they are around 420nm.

We might need a lil more info on what you are trying to accomplish and more info on the specs of the laser you are trying to replace (sounds like something most of us have not seen before, pictures would be awesome).

[andythemechanic]

Hi,

sorry swami, but at the stability/lifetime levels you need for a mask writer you will not get that much power out of a single mode emitter. The lasers I know for such devices are all very precisely temperature regulated, low current noise, external feedback stabilized and wavelength narrowed.
You also need precision optics to correct for astigmatism and elliptic beam profile. Acousto optic modulators don't work with unpolarized beams.
One option would be to correct and stabilize two diodes separatly, modulate them with two AOMs and combine them afterwards with a half wave plate and a Polcombiner.
A very good start to look for diode stabilization is here: http://redlum.xohp.pagesperso-orange.fr/argonlaser.html

Andreas

[swamidog]

no problem always happy to learn something new.

Hi,

sorry swami, but at the stability/lifetime levels you need for a mask writer you will not get that much power out of a single mode emitter. The lasers I know for such devices are all very precisely temperature regulated, low current noise, external feedback stabilized and wavelength narrowed.
You also need precision optics to correct for astigmatism and elliptic beam profile. Acousto optic modulators don't work with unpolarized beams.
One option would be to correct and stabilize two diodes separatly, modulate them with two AOMs and combine them afterwards with a half wave plate and a Polcombiner.
A very good start to look for diode stabilization is here: http://redlum.xohp.pagesperso-orange.fr/argonlaser.html

Andreas

[mixedgas]

Some 700 mW 405s exist*. They are multimode at higher powers, and by the time you clean them up, they will be down to about what your getting now from the KR ion, but it will be a journey, probably have to run them through anamorphic prisms, some form of Bragg Gratting, Littrow Grating, or external cavity feedback and run them at 1/3rd power. Or ram them into a spatial filter or fiber to clean them up.

I'll drop you a Private Message. I'll tell you whom and where, but you will not be happy with what you have to do to fix them, beam quality and focus stability wise. Redlums site is pretty state of the art, except he does not have PPLN or Bragg feedback covered, because he could not write the poled gratings or fiber gratings at home. I'm sure he will figure out how to do that, some day. He's really good.

If you place a sharply resonant device in front of the diode, you can steer and lock its wavelength to a certain extent. That is what the PPLN or Bragg fiber grating devices do, to a certain extent. There are other tricks with iodine cells, etc, but they are beyond the scope of this forum.

Have you considered getting the ion lasers refurbed by Evergreen or Cambridge Lasers? Talk to Brian Bohen at Cambridge or Phil Fostini at Evergreen. Brian makes new tubes from scratch, he does not just refurb. I'm guessing you just got hit by the SP ion production line shutdown?

Given the current state of UV diodes, you may be happier staying with ION for a few more years, or going to 288/354 nm dpss. 354 and 288 nm is troublesome and expensive, just as complex and expensive as Ion. Not to mention the need for quartz optics and possible chemistry changes. There are just some things ion does well that modern stuff can't.

*Guys, I cant disclose this 405 maker in a open forum. NDA
I'm openly saying that, because I know the pointer doods from the other forum would drool over a watt of tight UV and I will get PMs. So would the home 3D printing folks. Some things from work have to stay at work, but that manufacturer did me a serious favor. I'm going to try to return it by sending them a potential customer.
That is the rules of the game. Nor am I thrilled with the idea of a watt of UV going into commercial pointers, and we all know who "wickedly" reads the open source lit.

Steve

[andythemechanic]

Mask writer have typical spot diameters of 500-800nm. No Multimode diode will get you there. I have seen several lasers used in mask writers. Typically they are stabilized with VHGs and very well isolated with faraday rotators to prevent external feedback to the diode. Actually the ones I know have far lower powers than 200mW and replaced HeCd's. Some German Companys are makeing these.

Andreas

[andyf97]

what is he meaning by mask writer.

[andythemechanic]

Mask writers are devices to write structures in photoresist, usually for lithography masks. You have a photoresist on a chromium layer on a glass substrate the structure is written to the resist, than developed and etched into the chromium. These devices usally write the mask directly with a laser, which is focused onto the resist and scanned over the surface to be written. Resolution is in the 500nm range, a perfect diffraction limited beam is needed, which is focussed with a high NA Objective. These devices are quite impressive in their high precision.