Milles Grigot 475.5nm laser head revamp

This is me being dangerous and adding about 10 extra percent power, via Vf to the output.

But we like finished pics first.

This is a wonderful laser head. A very famous Milles Grigot 488nm cyan laser output head. It puts out a very high collimated beam at 487.5nm, basically a gorgeous turqouoise.

It's not a diode laser though. This is oldschool technology. We take an invisible 975nm IR laser pump diode, put it through a doped glass optical fiber, put it through some form of nonlinear crystal (I'm assuming Lithium triborate (LiB3O5) or LBO for short) to change the input colour from invisible, to visible.

Nonlinear crystals are super cool. LBO, for example, can combine 2 lower energy photons (say invisible red/975) and output a single higher, summed energy photon, at roughly 2x the energy.

[Nerd shit]

Check out the following 2 images to try and get a basic understanding of the relationship between photon wavelengths and the energy they contain.

[Nerd shit] So, the bluer/X-rayer/Gama-rayer the photon source, the "smaller" the wavelength, and the more energy it contains.

There's an inverse relationship between wavelength and energy. The smaller the wavelength the more energy the beam of light contains. And hey, remember, light is a concept. There are MILLIONS of types of light our human eyes cant see. Birds, for example, can see ultraviolet. And medical devices can see X rays, even if they go right through our skin.

The reason an X ray has enough energy to mess your DNA up, but a radio wave (or microwave, think 5g) doesn't, is due to this relationship between energy and wavelength.

[More nerd shit] This is the classical (non quantum) understanding of photonic energy.

E(energy) = h f

Or

h*c / wavelength.

These are all ratios.

But NONE of this is necessary to understand this project. Just fun for a dork like myself.

Step 1. Let's take the black cover off.

I bought 2 of these famous laser heads. This is the first iteration of this very famous laser, which I will be destroying to understand how it works.

We need to open up the copper "packet"

Carefully. There's a glass hair fiber inside it. 1/2 the width of a human hair.

Looking at the side of the device you can see some data, the top middle number you see 976-G14. This is important. The pump diode for this laser is about 975.5nm (aka 976)

976nm is invisible to the human eye. Sooooo, how do we get blue out of it?

We're going to use really cool linear crystals to double the frequency to make that extremely invisible infrared light bright blue, by doubling the frequency, at the expense of output power. It's basically alchemy.

The 975nm diode seems to draw around 700 max, at under 2.5 volts. That's a surprisingly difficult power supply to design. Let's design one that produces 600ma @ 2.3v, for buffer.

975nm diodes are like, violently expensive.

Here's the front output aperture of the laser that we are about to destroy to learn.

Let's open that copper box, that spiral of glass hair? That's a doped glass fiber. It takes the output of the 975nm diode, and pumps it into a magical crystal that we'll talk about later.

We slowly remove the important parts.

If you sever that human hair width piece of glass wire? It's game over.

What do we have here? This is the 975.6 mm pump diode.

Let's find the specifications. We need a pinout, and all the VF, IF, and maximum heat rating.

Here you can see my first attempt at pumping the diode. It works for about 35 seconds?

Why?

I didn't put a constant current driver to limit the input current to under 600ma. (I was planning on pumping the crystal @ 808nm for other reasons, not important).

But the whole point was to investigate how this shit works.

So let's open the newly broken laser Resonant cavity.

A resonant cavity is a hermetically sealed box, that takes the input pump diode, passes it through some suuuuper cool crystals, and optics.

You can clearly see the fiber optic going into a tiny (15 degree, pointing to the left) little crystal, about 1cm above the bottom of this hermetically sealed copper catacomb.

When I make my own resonant cavity, we'll be pumping this hermetically sealed copper optical train, with extremely dry argon or some other dry noble gas. I'm probably going to use extremely dry CO2.

The reason why? Is because that little crystal in the middle (1cm above the bottom, pointing 15 degrees to the left)is likely LBO. or some other similar nonlinear crystal.

Oxygen and humidity ruin all of these crystals.

I completely disassembled the optics, because I want to use them for a different project. And I wanted to remove that little crystal, and send it off to a laboratory to see exactly what the chemical comp was.

Anyways , broke the first one (for a reason)

onto the next real step.

All right round two. A newer reversion.

This one was QC/d perfectly with much higher quality standards. 975.56nm pump.

Should produce 487.78nm light. CLOSE enough to the most gorgeous blue, 488nm.

Same dealio. Let's remove the packet.

You can see the front output window of the 488nm ouput. That glass circle on the left is a dichroic mirror.

A dichroic mirror is a piece of glass that, has a VERY thin coating of specific molecules (topic for another post) that allow certain wavelengths of light to pass through, while others get reflected.

The goal is to make sure the blue color (488nm) that I want goes through but the invisible 975 NM infrared light bounces back.

Remember, this 975nm pump diode is rated at 600ma @ 2.2v. That's a total input power of 2.2w, and an output power of 1.1w. Even if 10% of the light leaks out, that's 110mw of invisible infrared light. If you looked right into it, without the dichro, you'd go blind before you ever NOTICE you turned the power on, aha.

So, let's buy good quality optics, and glasses. We were only given 2 eyes (kidneys etc etc) so let's keep them in good order.

View from the side. I don't know if you can see it, but that lower black connector, it kind of came out of the socket. That's why this extremely cool piece of equipment didn't work. EASY fix, but I want to reverse engineer it.

The goal is to power it from ESP32, or Arduino.

Using a knife, a very very low temperature heat gun, and a couple screws let's remove that copper fiber optic chamber.

Here you can see the fiber optic. I will power it up so you can see the difference in colors between the output and the input and everything in between.

Let's be so careful. That fiber optic is glass. Let's use Teflon tape to make sure nothing nothing gets too much pressure on it.

Here is the data sheet for the 975 Adam pump diode

Here's all the blah blah blah bullshit. If you know what this means that's cool, if not don't worry about it.

At the top left you can see that gold plated rectangle with about eight legs on every side.

We have to de-solder the legs or snap them off. I'll be pumping the diode directly with a CC driver, of my own design (fuck me, cross your fingers, I'm awful at this)

That white little box next to that gold rectangle is a relay and I do not want this to turn on and off based on all kinds of physics you don't care about.

I'm going to use Arduino to challenge and pump this system.

Let's remove the gold thingy.

Lasers are so so so sensitive. I have a extension cord wrapped around my left leg, with the hot and neutral cut off, only the ground is pushed into my 110v North American ground. This is called a grounding strap.

When you're messing with EXPENSIVE laser diodes, GROUND YOURSELF.

Even the smallest static shock could fuck this thing up.

There's like six left in the world, I'm not fucking another one up.

Cut it off, let's straighten the pins out.

Step two pins yeah. You can see it's no longer attached to the daughter board.

Now let's go into documentation and make sure all the pinouts are working, or at least figure out what the hell we're doing lol.

Bottom pins, I believe it's 10 and 11, would pull the voltage input from the controlling board...

10 is VCC, 11 is vdd.

And let's refer back to the data sheet to make sure exactly know what the fuck we're doing.

We want a VF of under 2.5v so I am using a constant current constant voltage lab psu to output <2.3V. At this voltage the maximum input current IF is about 600 mA, the maximum amperage for this pump diode is 700 mA. At this voltage level 1.62v and If (265ma) you get around 0.42w.