Optical Waveguides in Photonic Crystals

KeelSpawn sent in a short article talking about creating the equivalent of etched silicon for light, using a method intended to be cheap enough for commercial applications.

Comments

Re:costs $$$

[jejones]

Braun's referring to the other guys' method, not his. Braun's method is cheaper.

Other Technology

[Anonymous Coward]

How 'about this instead!

Re:Other Technology

[Pooua]

How 'about this [opticalcrosslinks.com] instead!

The site to which you linked refers to a completely different subject, that of interconnecting between discrete devices. The subject of the original article is interconnection within a single, monolithic chip. One of the points of the original article is that the new technology can also make tighter turns than regular optical fibers.

Re:The equivalent, or the same as

[Zelet]

No, in this case the laser process is cheaper and more reliable. One reason for this, as stated in the article, is that there is only one pass of the laser to make the pathways. The difference is that the current "complex multistep photochemical etching process" is just that complex and multistep.

Re:What about applications?

[Drakula]

Probably the biggest application for this technology will be optoelectronic integrated circuits. One of the things that makes optical communications so expense and limits there speed is the need to convert from a light signal to an electronic signal and vice versa. Not only are electronic cictuits slower than there optical counter parts, all the separate modules are expensive. This technology would reduce the need for conversion, at least part of the time, by allowing one to make optical circuits instead. Once that can be done, integrating the wave guides, pump lasers, and amplifiers would be not too far down the road. This could make fiber to the home a reality.

Re:I have a DLP projector.

[CrystalFalcon]

Digital Light Processing. A lame abbreviation if there ever was one. :-) A Texas Instruments technology, anyway.

Re:Trek

[tsa]

For a good photonic crystal, with or without incorporated waveguide, you need three things:
1) Two substances with an as high as possible difference in refractive index. Normally air and a semiconductor are used.
2) The substances that are used must not absorb light, so semiconductors with a high bandgap are necessary (depending on wavelength of courase)
3) A VERY regular crystal structure. This is very hard to achieve. Most research groups in the world use the trick with the spheres as shown in the article. The problem is that these spheres form fcc lattices and what you really want is a diamond lattice, which can not be obtained as easily.
So the five years you mention may be a little optimistic!

Re:Typical Academic Babble

[Pooua]

Scanning a laser across a 12 inch wafer will never be cheaper than doing it by lithography.

The laser doesn't have to scan across the wafer; one may use the same masking process used in lithography. The difference between conventional lithography and the new technique is that the new technique can complete the entire waveguide in one step, simply by exposing the polymer to laser light. The old lithographic technique required a step to build the waveguide and several more steps to build the reflectors, besides any other components (such as lenses) that might be in the waveguide.

a brief intro to photonic crystals

[stevenj]

Since I actually do research in this area and there is some confusion here, let me give a very brief introduction to photonic crystals (which can be studied using free software).

Photonic crystals are periodically-structured optical media that, with the right structure, completely forbid the propagation of light in a certain range of wavelengths (analogous to electronic band gaps). They form a sort of "optical insulator" that you can use to trap, guide, and control light. The work at essentially any wavelength (in contrast to metallic waveguides) provided that you can fabricate a periodic structure with periodicity on the order of half a wavelength, and have a number of potential applications, including:

• Integrated optics: optimally miniaturized networks of optical devices to offload some analog signal-processing or telecommunications tasks, circumventing e.g. bandwidth limitations of electronic circuits. (Few these days are predicting all-optical computers.)
• Optical fibers (from 2d or 1d patterns) that circumvent fundamental loss/nonlinearity/PMD limits of silica fiber, and for other novel applications (e.g. high-power or highly-nonlinear fiber devices).
• More-efficient LEDs and lasers, both by enhancing the optical density of states and by making the light go where you want it to go.
• Slow-light devices for time-delays, nonlinear interactions...
• Super-lenses (that can focus beyond the diffraction limit via negative effective indices of refraction).
• Super-prisms (very wavelength-sensitive refraction, e.g. for wavelength demultiplexing).
• ...

1d photonic crystals (multilayer films) have been known since Rayleigh in 1887 (although there are new twists) but 2d and 3d crystals weren't conceived until 1987, via a marriage of solid-state physics and electromagnetism.

The paper Slashdot linked to is considering photonic-crystals made by self-assembly of microspheres into close-packed lattices. A perfect crystal has limited use; you need to make defects to carve devices out of it, and that is what they are doing here. (There are many problems of precision, etcetera, that still need to be overcome for practical integrated devices, I think.)

Note that one can also make photonic crystals with traditional lithography, but that poses its own set of challenges (especially for full 3d-periodic crystals).