OT Flat lens.. (meta material)

Potentially pretty cool. However, the article doesn't say what happens off axis--it's easy to make a nice focused spot on axis.

And I don't believe that a good high-NA lens is 40% over the diffraction limit on axis.

Cheers

Phil Hobbs

Yeah, one thumbs down for Science (the magazine), the cover story is still behind the pay wall.

George H.

Potentially pretty cool. However, the article doesn't say what happens off axis--it's easy to make a nice focused spot on axis.

And I don't believe that a good high-NA lens is 40% over the diffraction limit on axis.

Cheers

Phil Hobbs ===============================================================================

Also didn't say anything about chromatic aberrations. Wonder how wavelength dependent the "interaction" is, compared to the pillar size?

----- Regards, Carl Ijames

OK, that's the world-changing scientific breakthrough of the day. Or hour.

Would be nice if it works, except for Nikon and Zeiss.

Yeah, but it's OLD technology, Nanomaterial lenses, gratings, and other items are familiar holograph items, and very early color photography used a similar trick, to make color images without any colored dyes.

Lippmann published about 1.2 centuries ago...

Metamaterials aren't the same thing. A metamaterial effectively has a negat ive refractive index, which leads to a lot of remarkable properties.

The idea that IC processes are cheap compared with lensmaking is pretty fun ny though--it's the high precision mechanics, coatings, alignment,and low v olume that makes fancy lenses expensive, not generating the curved surfaces .

Full points for comedy.

Cheers

Phil Hobbs

hy

ative refractive index, which leads to a lot of remarkable properties.

The article described, though, doesn't show any such properties; it looks e quivalent to a zone-plate or hologram lens. Embossed holograms are MUCH cheaper to mass-produce: recall the National Geographic cover with the hologram skull. ..

I've seen holograms before--Fourier optics is part of my gig, y'know?

Metamaterials are different--phase propagates backwards, for one thing.

Cheers

Phil Hobbs

Not to change the subject (never!) but this is amazing:

It's an optical diode! Way better than the microwave equivalents.

You have to use those a lot in fibre systems, because optical amplifiers are symmetric. A microwave amp might have an isolation of 30 dB or so, whereas an optical amp with 20 dB gain has an isolation of -20 dB (i.e.

They're also useful for keeping diode lasers stable, but you have to deal with the front facet reflection somehow. I usually use two-stage free-space isolators unless the laser is already pigtailed.

Diodes are liable to mode-hop if the backreflection is more than about

-60 dB optical.

The polarization-insensitive trick is fairly neat. See

Cheers

Phil Hobbs

Are the things JL linked to based on the Faraday effect too?

George H.

huh.. never mind. I just learned that microwave circulators are based on Faraday rotation too.

George H.

We ordered some (cheap, $70 range) and plan to see if they reduce noise in a fiber link. Back reflections certainly cause mode jumps in our lasers.

Right. The cheap VCSELS seem especially sensitive to back reflections. Turn-on is interesting if old stuff is coming back, sort of like a super-regen receiver.

There seem to be a lot of clever people in optical design.

I assume so. All other passive, time invariant elements are reciprocal (apart from loss).

Cheers

Phil Hobbs

Coupling a diode laser into fiber is a pain... (I only have to do it ~once a year so I'm far from an expert.) As Phil said, I think my biggest issue is reflection from the front surface of the fiber. (which the isolater thing won't fix.) I make a "poor man's" isolator that reduces the reflection, with a linear polarizer and 1/4 waveplate. For best results the polarization optics should be right before the reflection. (I've put it a mirror bounce away without any difference that I could notice.) There are various "angle" tunings involved so you need a way to monitor the reflection... For my gizmo* there are side reflections that I look at with a video camera. George H.