How does one slow down the travel path of light?

[Unown (WILD)]

If you saw the thread title explaining how the Bose Einstein condensate stops light, though not useful to the OP, is pertinent. Why is everything I say ridiculous? I guess I'll start calling your statements out.

Yeah that ain't gonna happen outside of the politics thread

Not only was your posting useless for the OP, but it was already mentioned as a related point of interest by someone else, you wasted a post just to draw attention to yourself without adding any useful content what so ever.

You were basically saying " Look at me, I have nothing of value to add but I could have said that too. " .

If you had added anything of interest what so ever I wouldn't have said anything.......but basically all you said was " Look at me and how smart I think I am. " and now you vow to be confrontational out of spite.

I'm going to start handing timeouts if you guys keep attacking each other outside the politics thread. I don't want to see it again. Alright?

If you want to point out mistakes that are valid then you can do so in a respectful adult manner without a personal attack. Much appreciated.

 

[wouterjesse]

The speed of light is an obvious factor to consider when making holograms with pulsed lasers. Usually when making holograms, the laser beam is split for reference beam and object beam paths. The length of the two paths are often equalized to the accuracy of the coherence length of the laser's light. Pulsed lasers for holography typically include an etalon which gives huge coherence length to the light, and usually have a pulse length of about 35ns. That's about a meter long pulse of light. The beams need to be equalized to ensure that both arrive at the recording plate at the same time. The path lengths for the master hologram for a portrait like the one below (from 1994) is typically many meters long. The 32x43cm master for "Sherry" was shot by Positive Light Holographics with a frequency doubled pulsed Nd:YLF laser with an output of about 750mJ at 527nm. The 32x43cm transfer was done by me with a 35mW Spectra-Physics model 907 He-Ne at 633nm.

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Thank you for bringing this technique to my attention. I think this is not really the direction I want to go, although I will invest some time exploring the technique behind holographics. I have seen many of them years ago and it feels like the method is disappearing or am I maybe not noticing them around me anymore?

 

[Eidetical]

Apparently the speed of light can be slowed in air by passing it through a mask that gives it spatial structure!

Scientists slow down the speed of light travelling in free space

Scientists have managed to slow photons in free space for the first time. They have demonstrated that applying a mask to an optical beam to give photons a spatial structure can reduce their speed.

www.sciencedaily.com

 

[paul1598419]

I remember the Bose Einstein condensate before the beginning of the 21st century when CU Boulder was working on it. I had been to that campus during the efforts to bring this forth when I was at CU Denver. IIRC, they were using Na to effect the condensate.

 

[kecked]

Thinking about it, you can and do measure time delay in a light pulse in an interferometer.

 

[Eidetical]

Thank you for bringing this technique to my attention. I think this is not really the direction I want to go, although I will invest some time exploring the technique behind holographics. I have seen many of them years ago and it feels like the method is disappearing or am I maybe not noticing them around me anymore?

Pictorial holography peaked around 1990, but never made it to "fad" status. It's generally an analog technique in a digital world. Few want to spend a half an hour or more shaking trays in the dark to process a piece of silver halide film or plate. While holograms can be made with the cheapest lasers, interesting complex imagery requires stable single mode lasers with a large optical table and big optics. All are more available now, but who wants to spend time on anything that doesn't include an app for pocket computers? Plus, holograms are generally a pain in the ass to install and light, or integrate into a product. But the imagery can be really cool. And holography is a great reason to play with laser light. Lots of components to move around and align to perfection.

Despite all that, the public has yet to experience laser-lit transmission holograms on a grand scale. Those images can be really deep, interact with real world imagery, and have a uniquely magical "presence" in a way that no other "lightfield" display or technology can even approach. That's why so many have usurped the words "holographic" and "hologram" to describe their obviously non-holographic technology.