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How to create many frequencies ?

Psyrex

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Newbie here but looking to learn.
I see there are many frequencies available but is it possible to have one laser and many frequencies through adapters?
How can you multiply or divide the frequency and create many nm variations from a single light source ?
I’ve got to do some research into a wide spectrum of lasers and with no experience in this field I’m not sure if I have to buy one of everything or is there a variable system that would either cover all frequencies or hit major steps ?
Thank you.
 



bostjan

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Do you mean getting different wavelengths from a gas laser or using crystals to drive an overtone? I guess I don't really understand the question.

What is the end goal?
 

julianthedragon

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To manipulate wavelength/frequency the way you described in the question (custom adapters that can bend a frequency to hit any/all frequencies?) isn't yet possible. As of now, lasers work by exciting a specific material (could be gas, solid, or liquid) and using the frequency generated therein. It's the gain medium that determines frequency, not the other way around. Which is why there are few yellow/orange lasers for example.

With DPSS technology it is possible to change the wavelength but not to anything you want, using a certain combination of crystals. Look into the technology needed to make 532nm DPSS green. It generates that 532nm with an 808nm diode. 473nm, 589nm, and 1064nm are other common DPSS wavelengths to look into.

Gas lasers can generate multiple frequencies that can be split, and they can often be tuned slightly. There are also diffraction gradients that may be able to tune the output slightly as well.

Some solid state diodes are also tunable under certain conditions. 2 examples I've seen: The sharp GH04850B2G diode can reach from 488 to ~492nm if it's overdriven with current, and some red diodes can be tuned to orange or yellow by cooling the diode down using a TEC or liquid nitrogen.

If you are looking for a theoretical laser with a variable system that could easily hit any wavelength, you should look into quantum dot lasers and free-electron lasers. They use electrons and quantum dots as their respective gain mediums as the names suggest, and in theory either one could hit any wavelength in the visible spectrum by manipulating the gain medium. But it could be a very very long time before lasers like this are widely produced let alone available for cheap consumer purchase.
 

Anthony P

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A dye laser can cover pretty much the entire spectrum depending on the dyes used and grating adjustment.
 

Psyrex

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Thanks for all your replies folks. Im researching what frequencies are able to penetrate a limb and could particular frequencies be more sensitive to vascular structures or bone, metal implants, and what else could be uncovered by working through the frequencies and their variables.
So casting a wide net and then narrowing it down.
I think I’m looking at Dye lasers initially if Various dyes will cover a wide spectrum.
 

julianthedragon

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Thanks for all your replies folks. Im researching what frequencies are able to penetrate a limb and could particular frequencies be more sensitive to vascular structures or bone, metal implants, and what else could be uncovered by working through the frequencies and their variables.
So casting a wide net and then narrowing it down.
I think I’m looking at Dye lasers initially if Various dyes will cover a wide spectrum.
What are you planning on doing with the lasers?
 

bostjan

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Skin is more opaque to bluer light than it is to redder (or more infrared) light. There would for sure be some resonant frequencies along the way.

High intensity light can damage tissues, though. Short wavelength light can damage DNA and cause cancer.
 

Psyrex

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I’ve worked in operating theatres for +20 years and the most time consuming, confusing, problematic, expensive, dangerous, resource wasteful process is X-ray. And the results aren’t that terrific.
During Surgery, everything has to stop while we assemble the radiographer, everyone dons lead gowns or already labour’s under lead for hours all day, machines are brought in or are already taking up valuable real estate in the theatre and then when it’s all perfect, they take the shot or screen and then there’s the worry that spending a lifetime being xrayed isn’t going to help me in the long run.
Here’s a pic of a Hand in NIR beam. Diodes at the bottom Centre. And from this image I imagine.
I Imagine that we can use a ‘box’ where a patient who comes into Triage at a hospital and we can scan their hand or foot to instantly see if there’s a fracture or a vascular blockage or whatever. No waiting, no specialist radiographer, no transferring of the patient, no exposure.
Imagine we could use a similar portable ‘box’in theatre, no protective screens or lead gowns or risk of glowing in the dark, less cost time equipment.
Imagine this ‘box’ could be portable for EMS /Ambulance so at an accident they can instantly identify fractures in or out so that appropriate resources are deployed.
Despite the basic implementation of a beam, hopefully it could be refined to highlight different structures within the limb, combined with photographic means to record the scanning result thats instantly available to surgeons.
 

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julianthedragon

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So if I'm following correctly the goal is to use lasers to image a body part by selecting laser frequencies that pass through certain parts of the body? So you want to use visible or NIR light to image instead of X-rays, but using lasers?

If so I personally don't have the expert experience to help you much further unless there's a laser question I happen to know the answer to. But that sounds like it could be a cool project
 

Psyrex

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Yes Julianthedragon, that’s it.
The volume of fractures every hospital does just on hands and feet is phenomenal, we can tie up 8 permanent staff in a theatre doing hand fractures all day. Probably 100 man hours if you add in the specialists and it’s mainly on broken fingers, lacerations or foreign bodies.
Now speed that up from the Front door at Triage sorting the fractures from the just swollen and sore,and then reduce the time to process patients waiting for X-rays and transferring them from ED to X-ray and back again. Then free up space time and man hours in the operating theatre and you’ve got yourself a quicker, cheaper, less dangerous way to do surgery. I’m quite sure the accepted average hourly cost of an operating theatre in Australia is $350 a minute.

What would you guess would be the wavelength of the light in the picture ? All I have is that it’s NIR. But considering that it’s highlighting the veins in his hand..?
And considering that it looks white but probably due to the IR camera and the brightness flaring our the camera sensor.
Any guesses or direction would be most welcome.
 

julianthedragon

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What would you guess would be the wavelength of the light in the picture ?
That's a screenshot from a styropyro video

He extracted the diode from a 532nm dpss pointer so it has to be 808nm

Good luck with this idea, I can see how convenient it would make things if it works out!
 

Psyrex

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I take it that the higher the nm the greater the penetration ?
Or maybe not ?
 
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ZRaffleticket

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Unlikely the case for everything, but I'm not going to do this research to confirm. Look into absorption spectrums for skin, blood, muscle, fat, bones, tendons, etc. Overlay the graphs.... Find some points where you can see through (low points on graphs) only what you want to ignore
 




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