Well, one possibility is using something known as Fabry-Perot filter. It allows an extremely narrow frequency to pass, due to multiple reflections and interferences inside the material. Put the light source material within this filter, and you get a laser. That’s essentially the main difference between a led and a semiconductor laser. The filter makes only a narrow band of the emission be “stuck” there, creating a feedback effect that eventually tends to infinity, and a good chunk of that power passes through the filter reflectors, which are intentionally not perfect.

Other than that, I don’t think there is a filter that could be as narrow as the line emission from vapor lamps. Maybe using metamaterials, but a laser would be so much cheaper and easier. A vapor laser would certainly get the job done, but they are large and hard to maintain.

A laser, maybe, but definitely not LEDs. Vapor/gas lamps produce the narrowest frequency bands possible, because it comes from very well defined atomic transitions (Hz range). LEDs produce frequency bands with widths in the GHz/THz range, while semiconductor lasers can maybe reach KHz if they are really good. So, unfortunately, for this type of applications, vapor lamps would probably still be needed.

Source: I work with lasers and spectroscopy.

Edit: very good idea about using non-visible light!

It takes some fiddling, but it works, and is fantastic!

Your description got my attention, so I opened the steam link to consider buying it and… Hey, it was already in my library!

My story is kinda cool. TLDR: she stole my cat.

We lived in the same street, but other than the occasional nod when passing by each other, never really talked. I always thought she was cute, though. Oh, and she was married to a typical abusive guy.

One day my cat escaped, and after a week of searching, I almost gave up. Then one day she knocked on my door and asked if that cat was mine, because she thought she was a stray, and took her in. She gave her back, apologized, and that was it. But that cat would always find a way to go back to her place, and we kind of agreed to let her have 2 homes. Still didn’t talk too much or anything.

Years passed, and she finally had enough of her husband, got a divorce, and moved out. Came to ask if she could take the cat with her, and I said that’s ok, she barely came to my place anymore anyway.

More time passed, we kept a little in touch, but still didn’t really talk to each other. And then I decided to have a barbecue at home for my birthday… I invited mostly people from work, but then thought: “it would be cool to invite her”. And so I did. We talked, and talked, and when we realized, it was already 10 pm (barbecue was supposed to be from noon to sunset). She went home, the next day I invited her out, and long story short, we’ve been together for almost 5 years, living together for 3 and a half years, have 6 cats, and our first son is about to be born.

Very common in Brazil, but without the ‘h’. I was surprised when I learned about “that” Ghislaine.

I am sorry about this student and what happened to them, but that’s not true. The crime though (mostly mugging and pickpocketing), especially in Rio and São Paulo cities, is something to be concerned about.

Source: I am brazilian.