How to Build a practical LASER source?

Buy a cheap laser pointer and put a couple of polarized filters in front to vary the intensity...

As for varying the wavelength, as the light is coherant that will be difficult over a reasonable range...

For very small changes of wavelength varying the drive voltage works to a small extent...

As its a cheap project try it and see.

John.

thanks John.

laser pointer is not enough to me. the laser source should be capable of evaporating things like metal . the project is a laser based lathe that produces precious dimension objects.

What exactly are precious deminsion objects????

Can't tell if the OP is reading these posts and will eventually reply, but I suspect he is speaking here of precision machining using lasers.

Thanks to all for your kind reply.

Hi vermin , my project is to replace the existing tool shaping lathe with the laser equipped lathe. so i want it to be used for the purpose of turning , mining , etc process in a clean and neat manner...

OK, to do full-blown metal machining, realistically, you are looking at either a large YAG (Yttrium Aluminum Garnet) or CO₂ laser. And you're looking at about 500+Watts of IR radiation at either 1064nm or 24(hundred something?)nm, and that's just for starters; also big bucks!!!

There are a few, very expensive diode lasers on the market (made of piles of laser diodes), but, currently, they're most powerful at 808nm (near infrared). I'm bringing on-line a 50 Watt 808nm diode laser that's capable of doing some damage to metal, but if you're doing true machining, you're going to need a lot more power than that. Also, diode lasers do not give off coherent light, so collimating these things are an art in itself. As far as any other laser that isn't DOD, no ion laser, excimer laser, dye laser, chemical laser, UV, Ti sapphire, or anything else has the power you're looking for.

I'd check out some of the large Laser welding and machining equipment on eBay before I'd ever try to make a laser lathe or mill myself!!! The facts: minimum of 220 Volt, 3 phase power; a lot of really intense, sophisticated cooling (ever try to keep DI water clean?); and a strong background in laser physics and mechanical engineering.

Question: Why are you machining with light? Aren't conventional metal lathes accurate enough or is there some special reason for not making physical contact with the machined material?

thanks vermin, i am do my final year academic project. and we want to do some thing differently. thats the main reason and the mechanical lathe are already existing so we cant do the same one.

is the laser sources are readily available . where can i buy it?

Just check eBay (no advert intended). Make sure you know what you're looking for, and try to get an idea (possibly from a student in the physics department) of the power and type of laser you need for your project.

Also, Buyer beware! You can find some fair to good buys on eBay. You can also run into people selling total crap. Make sure that it's in working condition and you get what you need with it to make it work. Watch out for "I don't have the ability to test it" line. While it may be true, you could also be buying a dead laser for a pretty price.

Good Luck!

I hope you're not planning to direct the beam straight into the material chucked in your lathe and hoping to cut it to some precise depth. Unless, of course, you're simply heat-treating the workpiece. Lasers tend to work better when cutting through the workpiece, not into it. You could cut tangentially, I suppose, but that has its own problems, like at what point should the focus be? And should your beam be focused or should it be collimated?

At least you're no longer talking about building your own tunable laser system! Yikes!

If Mo comes up with a really high powered, tunable laser (UV to IR), I want first chance to buy his stock!

Hey, The light from a diode laser is nicely coherent. Only a bit asymetric divergent, resulting in a seriously deformed spot after collimating and oblectif.

To be able to read a CD or DVD you need as little WFA as possible (Wave Front Abberation)

Mo: if you start with lasers you should start to dig into the optics too, It is not just pointing with a laser to an object.

A trick to have more output from a laser is to go in the pulse: you can easely overload a diode Laser to a tenfold of its continuous capacity as long as you keep the pulse short (nano seconds)

It is not directly the absolute power that does the job but the intensity of the moment.

When I left optical storage at Philips we did not really knew how a CD-R and DVD+R worked (RW is designed for its task) The substrate just changes reflection rate as soon as you pass a certain level of light intensity, Thus you can write a disk with the same laser power from 1 to 42x, your driver must be able to follow the data rate.

It took some time before we really got this.

...It took some time before we really got this...

Does the writing beam double as a tracking beam?

If so, does it reiterate, to change wavelengths during the process?

Indeed the writing beam is also used to track, and read.

To write he needs to go in higher power.

The wavelength does not change, as the angle and spot size/chape would change with the wavelength. The effect of a diode laser to change it's wavelength while heating up is nog well appreciated.

I remember in physics you can measure a pure light with its interference phenomina. Thus, you can buy a raster, say 1um interval, or less, let your laser go through it and measure wave length by its interference graphic on the wall. the raster will not be melt.

sorry I make a mistake at first post.

if you need laser source I can offer you one, I dont know how much power do you want? there are lots of large power laser for choose. co2, nd:yag etc. for industrial cutting.

contact me if you are interested in.

Hi Cnpower! Wassup? (slang for "what's up?" = Ni hao?) Hey, do you have any sources for 900 nm (or longer-wavelength) high-power-but-inexpensive infrared LEDs? "Luxeon" style? Engineering samples? Osram makes one that I like, but it's still too expensive. I am not looking for IR lasers. Definitely not. Just LEDs.

Wen hao,
-e

aha, is that you, europman? seek for led, large power? no problem.

yes osram can produce as large as up to 1A power. but I can only offer you 1/3, at 350mA and 940nm wavelength. Its led not laser. dont worry.

when time will your large led be on market? you live at a such luxeon place, dont care about money for a little led

how much cost osram offer you? mines may be not so expensive at same power.

when did you study chinese? by searcher like google, I remeber you dont like some yahoo, even hate it very much with wonderful your american slang english, which cannt be found in our dictionary.

what's up =\= nihao; it means: Za La? (in the most pure chinese)

nihao == how are you

you dian'er.

hi cnpower, i want a laser source that will be able to produce 500 degree of heat ...

can you suggest me which is the best one......

how to build a laser source of our own....

i have a semiconductor type source and is it possible to amplify it..

..

I hope you have deep pockets. You're wanting some of the most expensive kinds of lasers around. Some types of tunable lasers:

• A few solid state bulk lasers, in particular titanium-sapphire lasers and Cr:ZnSe and Cr:ZnS lasers allow tuning over hundreds of nanometers in the near and mid infrared. (In general, transition-metal doped gain media offer larger tuning ranges than rare-earth doped gain media, since their relevant electronic levels interact more strongly with the host lattice.) Output powers can be hundreds or even thousands of milliwatts. $$ to $$$
  
• Dye lasers also allow for broadband tunability. By using different dyes, one can cover very broad wavelength ranges, e.g. throughout the visible region. $$$ to $$$$
  
• Some free electron lasers can cover enormously broad wavelength ranges. $$$$$+
  

In some areas, tunable lasers compete with optical parametric oscillators, which can offer extremely wide tuning ranges but tend to be more complex.

Other types of lasers offer tuning ranges spanning a few nanometers to some tens of nanometers:

• Rare-earth doped fiber lasers, e.g. based on ytterbium, often can be tuned over tens of nanometers, sometimes even more than 100 nm. Most Raman fiber lasers also have the potential for wideband tuning. Relatively low power.
  
• Some rare-earth doped laser crystals, often doped with ytterbium, also allow for substantial tuning ranges. Examples are tungstates, vanadates, Yb:BOYS, and Yb:CALGO.
• Most laser diodes can be tuned over a few nanometers (often by varying the junction temperature), but some special types such as e.g. external cavity diode lasers and distributed Bragg reflector lasers can be tuned over 40 nm and more.

Some fine tuning, often continuously without mode hops, is possible for other lasers:

• Some compact solid state bulk lasers such as e.g. nonplanar ring oscillators (NPROs, MISERs) allow continuous tuning within their free spectral range of several gigahertz. Tuning may be accomplished by applying stress to the laser crystal via a piezo, or by varying the crystal temperature.
• Similar fine tuning is possible with some single-frequency laser diodes, e.g. by varying the drive current.

(excerpt courtesy of Encylopedia of Laser Physics and Technology)

Tunable lasers can be very expensive and complex, depending on technology used, tuning bandwidth and output power. Unless you have very deep pockets you may wish opt for a cheaper but less optimal solution: Identify a few laser wavelengths that will meet most of your needs and buy a small number of fixed-wavelength lasers having these wavelengths and desired power levels.

-e

That's quite a wash-list, ya got there, E-Man!!!

So many lasers, so little time...

-e

can any one suggest me any websites that demonstrates on how to construct a laser source. and other details regarding the lasers like calculating power, wave length, etc.

Did you google LASER?

http://en.wikipedia.org/wiki/Laser

I assume that you want to create a production system for nano parts.

With an electron beam you can peel atoms.

In fact you need to have an electron microscope to be able to see the result. Most modern types have the possibility to start peeling, and to look under the first layers.

...have an electron microscope...

The tunneling type, allows you both: seeing and manipulating the top layer of the lattice

YES I TRIED THE google but i didn't get the details that i needed to build a on.

thanks for this link..

This is a real nice answer, nothing to add.

Just: tuning is a standard procedure for lasers used in fiber optic communication.

there are complete packages available which contain different lasers each with their own tuning system, designed to use the same fiber. As these things are standard it might be possible that you can have the wavelengths you are looking for and with a reasonable price.

Making a laser yourself in the backyard shed is somehow impossible (or you have a nice shed and I want to be your friend)

Gwen

ps. in case you have this kind of shed you are going to make lots of friends here.

My apartment looks like Lawrence Livermore Labs pucked in it!

Next time im in Redwood I will stop by and help you to get rid of the stuff.

Gwen

My place is a mess, so you might want to drop by my work instead...

-e

I'm coming to your work...

I tought that we were going to do that experiment on all the women you knew?

In the starlight it might bring some fresh ideas.

My lab:

Far above the world.

Gwen

Hawaii or Chile?

Eu and Vermin, this is the remote Lab I run from my Desk, which is in the green lowlands.

The lab is located on the Roof of the UFS, Germany.

If you have an environmental study to do you can also put your stuff there.

Check it: www.schneefernerhaus.de

It is only 2650m from the standpoint of the picture.

Sorry, in weekend I'm running a family.

Gwen

Looks like a ski lodge from the web site! Anyone ever thought of making it double-duty?

This used to be a hotel. In the 80's it became to expensive to modrnise it and the route down was much more easy.

So gornment (Bavaria) took over the building and installed the UFS in it.

Great place, you can sleep there (have to make your own food) and enjoy the alpine evening and morning.

Great site! Any skiing nearby? I don't ski; I snowboard and spend much of my time on my ass. That is, when I'm not falling down the hill.

So are you there during the week and see your family only on weekends?

Bet it's one fabulous scenic commute; smell of pines and all that. How nice!

Wish our site was at a higher altitude. We get snow, but it's nothing to write home about. We do have the Astronomer's Lodge where our visiting astronomers stay. The Lodge is also open to the public, and the rooms can be had for a nominal fee. The rooms are nice (but no TV, thankfully), but you have to book way in advance. The 2.7 m (107") Harlan J. Smith scope is just across the drive and about 30 m up the hill. The 2.1 m (82") Otto Struve scope is just beyond it. Here's a link to our "live" webcam. And here's a link to our home page. The webcam is mounted on the Hobby-Eberly Telescope (HET), looking west. You can see the Lodge in the forground. And below is an aerial shot taken just east of the HET (which now has a silver dome for better thermal management), looking west:

-e

To be honest: I drive the system from my desk, 80m above sea.

When you look good you can see my two webcams mounted on the fence.

Last time I was there was end October. I plan a visit end of the month.

Skiing can be done just below, the zone that you don't see.

We use the site to evaluate harsh conditions on our equipment and their fuctionality.

Can you post links to those webcams? That would be sooo cool!

Uh, guys? Sorry to interrupt, but what ever happened to mohammadthalif ?

sorry guys , i was out of the city and went in a journey for few days so no internet connection thats why i was not able to participate in your conversation...

Sorry to all. and thanks once again for your reply...................

.....

Nice, you ask a question and then you leave.

Wow. Glabbeek, Belgium is more desolate than I thought.

thats your lab? I would like to visit if it would be possible.

its a pity I know only a little a b c english and a little electronics, otherwise, I should set on applying a position there. I shall experience again what desolation is.

let me study more english now. btw Gwen, could you find me a job in advance there? I can fix some problem of transmitter some times. if good luck.

now I understand why you ask me for solar heater and so on. no problem It can suit to your place and lower price.

Cnpower writes: "now I understand why you ask me for solar heater and so on. no problem It can suit to your place and lower price."

-----

The place is the site's Port-A-Potty. Ain't it, Gwen? The reason is for that solar heater is heat...as in heated seat. Have you ever sat on a Port-A-Potty seat at 18,000 ft? Have you? It sure'd solve the mystery of why those high-altitude models come with a pry bar. And here you thought this had something to do with a transmitter!

I wish the air in the cr4 room would be not polluted by some dirty words again and again. if someone want to show his wonderful english. he can go out to other forum which can well quarrel and play game in their drivel.

that chinese man can comprehend some litttle English. he likes peace and he dont like fight any more. but, he remembers the story of north latitude 38 as well.

Huh?!

sorry, not too severity

forget it.

So star wars comes to life! I though they had given up on shooting down ICBMs by laser. Or do you know something we don't about the big space rock some say is going to collide with planet Earth in a few years. I hope you find the right laser unit in time or we may all be toast.

These lasers don't hold a candle to Star Wars' lasers. You do know what that bright, shiny thing is in one of picks, yes?

-e

thanks europium , the links you provided in the post no 5 its very useful...

i will go through it completely.

...Some free electron lasers can cover... as in plasma free electrons?

- If so, how would they contain the temp and pressure?

- Is it merely an excited conductive gas ("neon" type) plasma?

- What's the "light" source (input to the pump) for this device?

It says there, the device can output up to x-ray range... wow

This must be a true "Flash Gordon" device come alive.

Not a plasma, which is (usually) an electrically-neutral mix of electrons and ions. This here thingie uses an electron beam very much like the kind of electron beam you'd find in a CRT, but one having a much higher current. The beam consists exclusively of electrons and no ions, and is shaped using some combination of electric and/or magnetic fields and is accelerated to highly relativistic velocities using electric fields. One arrangement which accelerates such a beam in a very compact space is called an RF Quadrapole - a technology very deserving of considerable study in its own right. In some FEL designs, the beam passes a series of magnets called "wigglers" which induce slight changes in the direction of the electrons, inducing them to emit electromagnetic radiation. There are other variations, as well. But none of them use plasmas. Ions take much more energy to accelerate and wiggle because of their far greater mass. As it is the electric charge, and not the mass, that is foundational to the operation of these devices, electrons are the lightest practical charge carriers to use.

So, like in a CRT, you use a magnetic tunnel to redirect or accelerate the beam. Right?

- How do you end up creating photons, by accelerating the electrons?

- How do you make the newly created photons into a coherent beam? Don't the resulted photons have an assortment of wavelengths?

- How do you pump the initial beam into coherency in the x-ray range? They just might penetrate the front of the pump around the aperture, won't they? - Am I missing something?

The xrays are generated by the undulating electron beam directly. They do not arrive from an external source, also FELs have been constructed in this way to function as a sort of parametric amplifier.

A Free Electron Laser is essentially composed of three parts: an electron accelerator, a magnetic undulator and an optical resonator. The electrons are forced by the magnetic field on an oscillating trajectory, thus emitting synchrotron radiation. In the electron frame of reference the process can also be seen as a scattering between the electron beam and the virtual photons of the undulator. If an external field is present, the radiation is emitted in phase with this external field. The interaction between the laser field, the static magnetic field of the undulator and the electron beam has as a final effect the spatial bunching of the electrons on the scale of the radiation wavelength, and the transfer of energy from the electron beam to the laser field. The undulator can be considered as the equivalent of the "active medium" of a conventional laser system, while the electron beam is the equivalent of the "pumping system"

Due to their peculiar characteristics Free Electron Lasers can, in principle, cover most of the electromagnetic spectrum from the microwave region to the vacuum ultraviolet: the wavelength of the emitted radiation depends on the electron energy and on the magnitude and periodicity of the undulator magnet field according to the following relation:

where λ_u is the undulator period, γ is the relativistic factor of the electrons γ= ( 1-c²)^-1/2 and K is the so-called undulator parameter, proportional to the magnetic field inside the undulator.

It is important to notice that λ_u and K have some limitations in their practical ranges; they are used to tune the FEL around a central frequency, mainly determined by the energy parameter g of the electrons, that depends on the choice of the electron accelerator. It is thus clear that, in order to achieve emission at short wavelength it is necessary to use high energy electron accelerators, that imply high costs and large size of the facility. (excerpt courtesy of ENEA center of Frascati, Rome, Italy). To get some idea of the scale of high-power, short-wavelength FELs, consider the size of the instrument cart left of center in the image below, as compared against the size of the FEL against the wall:

-e

...limitations in their practical ranges; they are used to tune the FEL around a central frequency, mainly determined by the energy parameter g of the electrons...

It sounds like a two stage wavelength tunning system

I get that Synchrotron Radiation is the excitement of electrons in angular acceleration, like at the perimeter of a galaxy, or a vast massive stellar object. - Is it?

- Is the mirror in the drawing, an effective filter for particles other than electrons?

...the electron beam has as a final effect the spatial bunching of the electrons on the scale of the radiation wavelength...

This is a hard to visualise concept: - what is spatial bouncing on the scale of wavelength?

Yes, synchrotron radiation is emitted by charged particles when they are accelerated. As acceleration is a vector, it has two components. In this case a speed and a direction. Any change in either or both constitutes "acceleration." In an FEL, it is the direction of this vector that is undulating, not necessarily the speed. And so yes, it's like what you see on a large scale in galaxies and stars, but you don't even have to leave Earth to see it in action. Charged particles from the Sun, the Van Allen belts, etc., emit synchrotron radiation as they spiral around Earth's magnetic field lines. And as these particles are of relatively low-energy compared to the electrons in an FEL, they emit at characteristically longer wavelengths. So low, in fact, that you can hear them on the radio bands down to VLF (it's pretty amazing what you can hear on the VLF band at 10 kHz and below: "Whistlers," "dawn chorus," "tweaks," and a whole bunch of other stuff that occurs naturally. Ask me about it sometime.)

I suspect the mirror in the drawing is geared specifically for reflecting light while transmitting high-energy electrons. Not the most ideal arrangement overall. It's better to stick with strictly optical mirrors (in the broader sense of being specular at the wavelengths of interest) and deflect the electron beam off to one side to a "sink" electrode.

"Bunching" happens if, for instance, you shoot an electron beam down a waveguide containing, say, microwaves which are constrained by the geometry of the waveguide to move at a speed close to the average speed of the electrons. There's a kind of amplified tube ("valve"), a so-called "travelling-wave tube" or TWT, which depends on its operation on electron bunching. As the electrons and the microwaves move down the waveguide, parts of the EM wave pull the faster electrons back, and pull the slower electrons forward, for each cycle of the wave that's in the guide. Like ball bearings rolled on an undulating surface (whose peaks and valleys run perpendicular to the motion) which is moving in the same direction but at a slightly different speed. The balls will tend to collect in the troughs and away from the ridges. Hope this helps. I can make things as clear as mud if I put my mind to it.

-e

...pretty amazing what you can hear on the VLF band at 10 kHz and below...

It's only pure sine that's inaudible. If it's a spike or a special shaped sawtooth, you can ever hear 0.1 Hz.

It's up to our definition of what is a tone, and what is a noise.

...tend to collect in the troughs and away from the ridges...

This is more into the helpful, but can you describe the rough geometry of the progressing wave?

You have to get away from those accursed power lines and their even more accursed harmonics. There are a couple of sites in Texas that are reasonably quiet, but Texas is not at the best latitude for listening to this stuff. Higher latitudes, like between 35-45 degrees (both north and south, btw, like the temperate zones), are the best for hearing "whistlers" and such. Btw, whistlers are produced by the RF energy from lightning strikes in the opposite hemisphere (at a so-called magnetic conjugate point) being both guided dispersed by the high refractive index of the Earth's magnetosphere, a plasma. By the time the impulse reaches the other hemisphere, it is spread out in frequency, much like white light is dispersed into its constituent colors by a diamond. The higher frequencies arrive first, followed by successively lower ones, resulting in a descending, whistling kind of note. Optically a diamond has an index of refraction somewhere around 2.5, I think. The magnetosphere's IOR at RF frequencies is more like 1000! Sometimes you can even hear whistler "trains," where the energy bounces back and forth multiple times, becoming even more dispersed with each hop. But you've got to get far away from power lines to hear them. The U.S. power grid radiates so much 60 Hz energy that my friends in Finland can hear it sometimes. It's a curse for anyone interested in "natural radio."

Gotta go pick up my fiance. Cheers!

This must be amazing. - Did you ever make an attempt to record it?

- Even supersonics and subsonics can be artificially treated into the audible

In the street next to mine, I can sometimes "Feel" the 50 Hz of the power line at night, barely audible, more of a tactile sensation

Or you can go to SLAC in Palo Alto and get a tour of their Synchrotron while it's running. They's gots these little windows on the side of the doughnut for letting the light out.

hi europium , yes i am not going to beam it directly into the workpiece instead i need a guided medium like fiber optic cable . is it possible to send the laser through the fiber optics?

.

Absolutely! Not only that, but some specially-treated fiber optics can act as the laser itself. If you're planning to "roll-your-own" industrial-strength cutting laser, or fit it with a fiber (or fiber bundle for really high power applications) PLEASE BE CAREFUL!!! Even stray light and reflections from the laser source can blind and maim. IR laser radiation, especially, can travel deep into the body and damage organs which are better absorbers of IR than skin and muscle tissue. You might find yourself needing a new liver, for example, after taking a stray pulse and dicovering that a piece of your liver had exploded after its temp was raised in a few milliseconds above the boiling point of water. Skin and muscle are very transparent to IR radiation and it is not uncommon to find such radiation penetrating to depths of 8 cm or more. Your experiments should be completely enclosed. Not even a crack for light to escape. If you need to see what's going on inside the enclosure, then put some CCTV cameras in there and watch it over a TV monitor.

-e

What would this device be used for?

And also obey Fermi-Dirac statistics, which makes their quantum behavior well suited to the production of laser light.^{Use that eye protection!}

Exactly what are you going to be doing with the laser? Machining? Etching? What?

When you tell us the what, we can then provide you with a succinct answer regarding the type and power laser you need. So, let me know.^{eye-protection}

Also check out "quantum cascade" diode lasers. These generate multiple discrete wavelengths at fairly high power levels.

-e