Is advanced training necessary to construct a microchip laser?

[preWarp]

Hello. I have little experience with construction of my own lasers. I would like to build a microchip laser. It is a special type of solid state laser. I am wondering what training I would need to succeed in building a microchip laser. Let me give you some background on myself. I have taken basic courses in electronics. I have an Oscilloscope and DC Power Supply. A CNC machine is forthcoming. I am confident that I could build a xenon flashlamp pumped ND:YAG solid state laser. I have a book with designs by Iannnini.

However, it seems that the microchip laser differs drastically from the basic solid state laser concept. The best information is by professional organizations and is written for post graduate students. However, there are several such sources.

I am wondering if one really does need to take several courses in photonics just to understand the construction of the microchip laser.

What impacts the cost of a microchip laser? What might be an affordable Nd:YAG based diode pumped microchip laser, regardless of power in joules?

[mixedgas]

two things:

Lapidary Skills for making the microchip.
Dielectric coating application for the mirrors.

Home lapidary setups are pricey. Making laser grade flats is not easy. Coatings are done by expensive professionals.


if you mean buying a Green MCA dpss crystal assembly from Ebay,and gluing it to a heat sink, then diode pumping it, that is a easy,rewarding, project. You then just need brass and a drill press on the mechanical side.


Microchip laser has unique connotations, generally means making subnanosecond pulses by very thin precision crystals.



Steve

[preWarp]

The answer you've given helps me understand. I was wondering if you would be willing to see this microchip laser source from a project called "laser4diy".

https://github.com/Laser4DIY/LaserSource

I believe the microchip laser is "doable" by those lacking the theoretical knowledge, ie I believe it may have been set forth in the form of instruction steps.

Or are they assuming one has a background in applied lasers?

If I am way over thinking please forgive me. It's just I assume laser4diy, the project, is for people with experience only and not for beginners.

[mixedgas]

The project is currently not documented well enough for a beginner to build it.

Steve

[preWarp]

Ok. Components of the laser head can be manufactured with a CNC machine using the *.step files they provide on git hub. I still need to know more about the Nd:YAG microchip crystal. That's why I came here. I have the notion that somehow that crystal is going to be an unlikelihood for me. The GRIN lens is discussed and I believe I saw pricing for this part. But then I am missing information about the pumping diode laser LED. It's as if the project is meant for someone who needs variance so they can build to suit. Before I had not mentioned these details and I believe I would have gotten a more detailed reply from you if I had been more comprehensive. Now can you give me a better idea of what I am dealing with given the project I mentioned?

Thanks

[VDX]

... what is your aim with the Laser4DIY project?

If for PCB-prototyping, as targeted, or general laser-engraving, there are much easier and cheaper ways today - with or without a laser, capable of engraving copper ...

Viktor

[mixedgas]

It's not a microchip laser.
It uses a Cr:Yag q-switching material bonded to
a Nd:Yag lasing crystal, followed by an undoped
section of YAG fused together. Which is the better part of 20 mm long. That's a lasing rod, not a microchip.

Followed by an insane single pass amplifier, pumped by
60 Watt fiber coupled pump diode.

Anyways the bonded multi-section rod is a one off from China. It is easily a 3,000$ part.

If your calling the pump Laser Diode an LED, this not a project for you.

You get a laser box that you will spend a lot of time redesigning the water cooling to insure power stability. They admit their redone cooling is barely adequate.

For all that work copying that academic research project you would get a laser that at best restricts you to a 35 micron wide cut in the lightest weight of PCB copper. Their best speed was 40 mm a second with the expensive optional laser amplifier.

For what you would pay to build this very,very, undocumented project you could buy two fiber laser modules from China, or one used American OEM grade manufacturing laser.

They don't even have a heater on the frequency doubling crystal, so you'll suffer from constant power drift and short, very shirt, doubler lifetime.

Their step files are "theoretical ", they are missing some things that protect the laser rods from shear stress and enhance thermal conductivity.

That GRIN is not something you manually glue down.


For the cost of building that unit, and the time you will lose fiddling with it on a daily basis, you can order a huge amount of professionally made quick turn pcbs.

35 um cuts severely limits your ability to make a PCB handling even modest voltages. No vias, and not enough power to make the solder mask template.

Beautiful project, but not very practical.

Steve

[preWarp]

I am enlightened by the insights you shared with me. I realize that I have yet to discover what types of solid state lasers are as hot or hotter than a CO2, gas state, engraving laser? I know that the fiber laser is. Is that the only diode pumped solid state laser with thermal performance that rivals the CO2 laser? There is a xenon flash lamp pumped Nd:YAG in a book by Robert E. Iannini. How does it compare thermally to fiber lasers? In all of this my main interests are in the power supplies for diode pumped solid state lasers. I require the design files for the PCBs and other info needed to build the power supplies. It's just a consuming interest I have in building a power supply with the unique ability to be used for a laser, ideally a hot laser. Thanks.

[mixedgas]

Laser Diodes are driven by very precise current sources that have to have very carefully controlled startup characteristics and near zero current and voltage overshoot. They are incredibly sensitive to static charge , back reflections, and reverse bias.

Open source high power laser diode driver schematics are rare. Beware of using constant current bench power supplies, most designs surge the diode at startup, often storing enough energy in the last output stage filter cap to destroy the diode.

High Power pump diodes are usually arrays of smaller diodes, so much of the design is dependent on what you are actually using.

Usually we build a passive protection network around the LD , staring with a reverse protection diode, a shunt reverse protection diode, potentially a zener clamp diode and certainly have a Lasorb [www.lasorb.com] to protect against static and fast voltage transients.

A modern driver usually has a step down switching regulator set maybe a volt to two volts above Vforward of the LD with a shunt device across the LD and an analog pass regulator in series with the device. The shunt is gated on until the power supply is powered up snd stable. Either a depleation mosfet or a relay is used as a shunt protector. The idea is that a normally conducting device protects the diode until the voltage and current are stable after startup.

For large pump diodes I and others use a commercial "brick" switching power module with voltage drop compensation inputs. The voltage compensation inputs are traditionally used for correcting the I^2R losses in the output leads of the power supply. However driving them with a differential opamp and a current sensing means let's you modify their output to a soft start, highly accurate current source.

There are only a few bricks on the market with the proper design characteristics to allow you to do this.

Generally, beware of amature designs that use a pwm switching buck power supply to directly drive a high power diode. Unless chosen very carefully these chips usually promote startup and shutdown surges.


Steve

[preWarp]

I will be careful to be assured that the designer is knowledgeable of semiconductor lasers. I was surprised to find out that they are sensitive to static charge. I will write the diode rated specifics on my hand and put an oscilloscope ahead of my diode to look for problems. I can also try circuit simulation since this is a diode. Albeit, with a peculiar capability at it's P-N junction.