In my world, electricity has not yet been discovered, and many advancements in society progress on a purely chemical or mechanical basis.

Lasers are incredibly useful and multifaceted tools, and I would like to be able to include this technology in my world.

I could imagine multiple sources of light (as a ridiculously underpowered example, hundreds of candles) having their light combined and focused through a series of mirrors and lenses to produce a laser-beam.

Is this feasible?

If so, where could this light come from and how powerful will my laser be?
What other problems might I encounter?

Edit: For clarification, the desired result would be a spatially coherent beam of light.

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    $\begingroup$ A collimated beam of light is not necessarily a laser. It is not hard to produce collimated light beams -- the technology and knowledge were available and used since the antiquity. $\endgroup$ – AlexP Sep 27 at 9:15
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    $\begingroup$ Chemical lasers exist. en.wikipedia.org/wiki/Chemical_laser $\endgroup$ – Klaus Æ. Mogensen Sep 27 at 10:10
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    $\begingroup$ You cannot at the same time say that a beam of natural solar light is an acceptable answer and request a coherent beam. $\endgroup$ – AlexP Sep 27 at 10:33
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    $\begingroup$ However, I cannot imagine a timeline in which physicists have come up with the Einstein Equations which describe how a laser & stimulated emission take place but somehow haven't noticed that electrons lead to electricity. That's like building a PCA machine without knowing about molecules. $\endgroup$ – Carl Witthoft Sep 27 at 15:00
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    $\begingroup$ @CarlWitthoft Ja. It is very hard to imagine how chemistry would have advanced to only 1850ies level without anyone inventing the battery. Volta did so in 1799. Without it, alkali and earth alkali metals remain inaccessible. $\endgroup$ – Karl Sep 27 at 17:20

It is not just feasible, it exists.

Quick explanation

A laser with a medium (such as a ruby) consists of a cylinder-shaped medium with a mirror on each end, one of which is fully reflective while the other one is partially reflective. The medium is given energy from the outside by a so-called pumping source. Usually electric light, emitted by flashtubes for example, is used as pumping source. But sunlight can do the trick as well. That kind of laser is called a Solar-pumped laser:


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    $\begingroup$ To save a click, note that the solar pumped lasers referenced in that article are infrared lasers and not visible light. Not sure if the question cares about that. $\endgroup$ – JPhi1618 Sep 27 at 17:36
  • $\begingroup$ @JPhi1618 I don't see why it would be a problem - OP only seems to care about using them as tools, and I guess IR lasers would work for that $\endgroup$ – pipe Sep 27 at 19:30
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    $\begingroup$ The NdCrYAG solar-pumped laser probably requires an understanding of electricity at some point, since Nd and Y are purified through electrolysis or ion exchange, both of which require an understanding of charge. Without it, you can't get Nd (and possibly Y) pure enough and would just contaminate the YAG. The iodide version involves drawing electrical power from waste heat to drive gas flow, but that might be doable mechanically, though I imagine it would be spectacularly inefficient. I'm not familiar with them in general, so perhaps someone has a design that doesn't require REM or electricity. $\endgroup$ – gormadoc Sep 27 at 20:28

When laser weapons were in early development, considerable effort was put into chemical lasers -- that is, using the energy of a chemical reaction to pump the reaction product in a laser resonant cavity. Hydrogen reacting with a halogen was studied extensively; all the halogens can be fed as a gas (with moderate heating, in the case of iodine -- astatine wasn't studied, as far as I know), react vigorously with hydrogen, and the products can lase.

Of course, this requires the ability to purify halogens, but that was done well before electricity was a practical energy source.

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    $\begingroup$ Astatine does, for any practical (except radiomedical) purpose, not exist. ;) Its chemistry is only known from tracer experiments. $\endgroup$ – Karl Sep 27 at 17:13
  • $\begingroup$ @Karl Yes, fascinating: it does exist as 1 gram in total on the whole earth crust. All isotopes of Astatine decay, it's created from decay of other elements. Up to now, I thought it's just something nobody really needs... $\endgroup$ – Volker Siegel Sep 29 at 13:47
  • $\begingroup$ Weren't there some designs of that type that were single use disposable (and meant to dispose of something else by single use)? $\endgroup$ – rackandboneman Sep 29 at 18:35

As others have said, lasers do exist which don't rely on electricity. The soviets apparently experimented with a laser pistol during their space program, to blind other astronauts or satellite cameras. There's a bit of a description of it here, along with some photos of the (very home-made looking) prototype. The Soviet Laser Pistol. In brief, this gun is a charge-pumped design using an yttrium aluminum garnet (other sources say ruby) gain medium, and a zirconium flash bulb, which burned the zirconium in an oxygen atmosphere to generate an intense, single use flash (similar to old single use camera flashes). While igniting the zirconium was done electrically in that pistol, presumably you could do this with other means: a flint-lock rifle with the flash tray filled with zirconium, and the barrel filled with ruby etc. would probably work in a sci-fi setting.

As a slight aside, you said:

Electricity has not been discovered.

This doesn't necessarily mean that it can't be an electrically-based design: historically electricity was very poorly understood in the early days. Ancient Greeks knew that amber could be rubbed with a cloth and attract small particles (this is a common high-school experiment) which lead to a lot of early 'friction machine' static generators which rotated a glass sphere against a woolen cloth. These were invented before electricity was understood, and were assumed to work on some form of magnetism Electrostatic generator.

Similarly, look up the Piezo-electric effect. When certain crystals are squeezed, they produce a voltage (cigarette lighters and gas stove/barbeque igniters use this principal, with a spring-loaded hammer striking a tiny crystal to produce a spark). It's possible your civilisation could have discovered this effect without actually understanding or discovering electricity. A water-wheel hooked up to a bunch of trip-hammers pounding on crystals, for example.

  • $\begingroup$ For a first answer, this is absolutely first class. +1 $\endgroup$ – mcRobusta Sep 28 at 3:30
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    $\begingroup$ "Ancient Greeks knew that amber could be rubbed with a cloth and attract small particles": the Greek word for amber is (in Latinate form) electrum. Etymologically, electricity means amberness. $\endgroup$ – AlexP Sep 28 at 11:01

There are also chemical powered laser. See https://en.wikipedia.org/wiki/Chemical_laser. they are very dangerous chemicals, but they can be very powerful.

Lasing is caused by electrons dropping for high energy states into low energy states and emitting a photon as they do so. By placing the lasing material between a mirror and partial mirror, the photons are reflect backing to the material causing more electrons to become high energy, generating more photons as the drop back into to low energy states. A certain number of the photons escape past the partial mirror. By careful sizing of the lasing chamber and by using specific lasing material to match the wavelengths of photon you get coherent waves of energy, the wavelengths are all the same and the peaks line up.

Early lasers used light energy to cause a ruby crystal to lase. With Chemical lasers you would use a chemical reaction between materials such as iodine and oxygen to provide both the energy and the lase material.

  • $\begingroup$ Could you please describe this technology in further detail? The idea of a Stack Exchange answer is that visitors may find answers to their questions quickly, without having to visit further sites or doing research themselves. By representing the information in your sources in your answer, you increase the quality (and therefore attractiveness for voting) of your post. I would be very interested in hearing of chemical lasers. $\endgroup$ – A Lambent Eye Sep 27 at 19:05

In antiquity people used devices called burning glasses and burning mirrors to concentrate solar light on a small point and burn stuff. Think of large scale, machinised magnifying glasses.

Burning glass

The focus can be arranged to different lengths. Legend has that Archimedes used such a device to burn ships at great distances. This feat has kinda been reproduced with limited success though (see the wiki).

You could use a prism to separate sunlight into a spectrum like Isaac Newton did, then use lenses and mirrors to focus a wavelength you like (say, red). Add a piece of viking sunstone (also known as calcite) to polarize the light edit: and a lasing medium such as a ruby and you've got a beam that is collimated and coherent in both frequency and phase - a laser!

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    $\begingroup$ Pretty certain you won't be getting coherent light out of a contraption like that. $\endgroup$ – Starfish Prime Sep 27 at 11:45
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    $\begingroup$ @StarfishPrime I would seriously try if I had the resources. $\endgroup$ – Renan Sep 27 at 11:46
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    $\begingroup$ Oh, I don't doubt it would be a) entertaining and b) hazardous, but it ain't no laser. I think you'd find you'd also lose an awful lot of power compared to plain old "burning glass", for very little improvement in beam quality. $\endgroup$ – Starfish Prime Sep 27 at 11:52
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    $\begingroup$ That's not a laser. $\endgroup$ – Mark Sep 27 at 20:37
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    $\begingroup$ @Renan, a laser produces light that is not merely collimated and monochromatic, but also coherent. You can't use linear optics (mirrors, lenses and the like) to convert incoherent light (such as sunlight) into coherent light. $\endgroup$ – Mark Sep 27 at 21:06

...hundreds of candles, having their light combined and focused through a series of mirrors and lenses to produce a laser-beam...

Nope! Sorry.

There's a couple of good answers here that show how you can power a laser with other energy sources besides electricity. But what you can not do is use geometric optics to "focus" light from any not-an-actual-laser light source into a powerful, laser-like beam.

If you want the detailed, mathematical explanation of why not, read about conservation of etendue.

  • $\begingroup$ Thank you! Yould you please provide a short, less-detailed explanation as to why this does not work? $\endgroup$ – A Lambent Eye Sep 29 at 18:23

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