Re: [SI-LIST] : Interesting theoretical questions

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From: Douglas McKean (
Date: Tue Nov 02 1999 - 13:00:30 PST

Hi Subas,

Here's my 2 cents worth ...

At 08:24 AM 11/2/99 +0800, subas wrote:
>Hi all,
>I have some theoretical questions regarding high frequency signals:
>1) What is the maximum frequency you can generate electronically by our
> current technology (GaAs???)?

Are gamma rays for food irradiation high enough?

? Can we have an oscillator that can oscillate
> in the frequency of the visible light, for example?

Well, in a sense lasers are optical oscillators.

>2) The way light gets reflected from a metal (silver in a mirror) is that it
>first induces current (as a receiving antenna) and again radiates (as a
>transmitting antenna) the EM wave instantly so that we get the impression
>that the light is being reflected by the metal surface. Then how come
>different metals can have different colors (gold - yellow) when we expect
>them all to reflect light of all colors?

Light reflection from metal can be interpreted
as a demonstration of the plasma frequency of
the metal. Also, the atoms of the metal either
absorb or do not absorb various frequencies.
Thus, they in sense filter various high freqs.

>3) Has there been any computer made without any clocks (asynchronous)? How
>fast is this computer?

In the mid-eighties I wanted to make a simple
4-bit async microprocessor as a senior project.
I was told to think of something. I was also
told there was one at the time, but I do not
remember the mfr or name.

>4) Why is optical computing getting no where? Is this because lasers are
>expensive? Or because of the lack of fast optical switch ( any non-linear
>optical device)?

Bell labs a while back did experiment with a
truly optical computer at the 4 bit level if
I remember correctly. I believe with the
barriers that had to be overcome with the recent
advances of the single double and triple damascene
processes for the new copper based chips, there
might be some similar technical barriers involved
with putting optics down on a chip.
Simply a wild guess.
Haven't a clue ...

Regards, Doug

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