# Ultra Fast Oscillator

#### ben sorenson

Joined Feb 28, 2022
106
Hypothetically, if it was possible would there be any benefit to have an oscillator that could oscillate at a frequency of 99% the speed of light?

What applications would it be applied to and how could we use it?

#### WBahn

Joined Mar 31, 2012
27,939
Hypothetically, if it was possible would there be any benefit to have an oscillator that could oscillate at a frequency of 99% the speed of light?

What applications would it be applied to and how could we use it?
That's a meaningless question. What does it mean for a frequency to be equal to a speed? That's like saying that the oscillator in your cell phone operates at 100 miles per hour. Totally devoid of meaning.

#### Ian0

Joined Aug 7, 2020
6,735
What do you mean by "a frequency of 99% the speed of light?"
The speed of light is 299792500 metres per second. How can a frequency by 99% of a speed?

#### Papabravo

Joined Feb 24, 2006
19,617
Remember, the product of frequency and wavelength is equal to a constant. That constant is approximately:

$$3 \times 10^8\text{ meters/sec}$$

The implications are that as frequency approaches a very large value the wavelength will approach zero asymptotically. Trying to build something with a size approaching zero would be an interesting challenge. Let us know if you have any insight on this.

FYI. This distance record for the highest frequency RF signal is 1.42 kilometers @ 403 GHz. That would seem to be a practical limit on the highest possible frequency for an oscillator that can be built easily.

#### Ya’akov

Joined Jan 27, 2019
6,858
As many have pointed out, your two units are incommensurate, but if you mean producing radio waves that are almost light waves, there is a lot of promise in that.

The “terahertz gap” the frequencies that fit in the space between what we call radio and what we call light is a current topic of a lot of research. The strict truth is that both radio and light are electromagnetic radiation so the division is somewhat arbitrary. As an example, it is possible to use nano-dipoles to “receive” infrared light. This is very different from typical sensors, but it works by treating “light” as “radio”.

The gap is from .3 to 3THz, which is also arbitrary, but based on the ITU (International Telecommunications Union) designated band. The frequencies in this range offer a lot of interesting properties which could enable new applications. They penetrate better than IR because they have a longer wavelength, while they can act like x-rays in some applications, the lower energy photons make the radiation non-ionizing, so much safer. They are much shorter than microwaves so in applications like radar they offer the possibility of much higher resolution.

There is an article here on AAC that has some information about terahertz radiation, you might find it interesting.

[EDIT: no change in content, autocorrect error(s) manually corrected]

Last edited:

#### drjohsmith

Joined Dec 13, 2021
549
As many have pointed out, your two units are incommensurate, but if you mean producing radio waves that are almost light waves, there is a lot of promise in that.

The “terahertz gap” the frequencies that fit in the space between what we call radio and what we call light is a current topic of a lot of research. The strict truth is that both radio and light are electromagnetic radiation so the division is somewhat arbitrary. As an example, it is possible to use nano-dipoles to “receive” infrared light. This is very different from typical sensors, but it works by treating “light” as “radio”.

The gap is from .3 to 3THz, which is also arbitrary, but based on the ITU (International Telecommunications Union) designated band. The frequencies in this range offer a lot of interesting properties which could enable new applications. They penetrate better than IR because they have a longer wavelength, while they can act like x-rays in some applications, the lower energy photons make the radiation non-ionizing, so much safer. They are much shorter than microwaves so in applications like radar they offer the possibility of much higher resolution.

There is an article here on AAC that has some information about terahertz radiation, you might find it interesting.

[EDIT: no change in content, autocorrect error(s) manually corrected]
Just a thought
is a laser, not an optical oscillator ?
QED .its at the speed of light .

#### ben sorenson

Joined Feb 28, 2022
106
As many have pointed out, your two units are incommensurate, but if you mean producing radio waves that are almost light waves, there is a lot of promise in that.

The “terahertz gap” the frequencies that fit in the space between what we call radio and what we call light is a current topic of a lot of research. The strict truth is that both radio and light are electromagnetic radiation so the division is somewhat arbitrary. As an example, it is possible to use nano-dipoles to “receive” infrared light. This is very different from typical sensors, but it works by treating “light” as “radio”.

The gap is from .3 to 3THz, which is also arbitrary, but based on the ITU (International Telecommunications Union) designated band. The frequencies in this range offer a lot of interesting properties which could enable new applications. They penetrate better than IR because they have a longer wavelength, while they can act like x-rays in some applications, the lower energy photons make the radiation non-ionizing, so much safer. They are much shorter than microwaves so in applications like radar they offer the possibility of much higher resolution.

There is an article here on AAC that has some information about terahertz radiation, you might find it interesting.

[EDIT: no change in content, autocorrect error(s) manually corrected]
Thank you so much for your time!

#### Ya’akov

Joined Jan 27, 2019
6,858
Just a thought
is a laser, not an optical oscillator ?
QED .its at the speed of light .
Interesting way to look at it, and maybe even more apt based on the way the question was asked.

I didn’t think of a laser, but probably because the oscillation of the beam in the cavity doesn’t change the frequency of the emitted light, it just amplifies it. Though that does make an oscillator at light speed, and so it is “useful”. But it isn’t really in the same vein as what I think the TS was asking about.

#### Ian0

Joined Aug 7, 2020
6,735
Just a thought
is a laser, not an optical oscillator ?
Yes, it should be a LOSER.

#### drjohsmith

Joined Dec 13, 2021
549

#### Ian0

Joined Aug 7, 2020
6,735
sorry @Ian0 , dont get that , can you expand please
Light Oscillation by Stimulated Emission of Radiation?

#### WBahn

Joined Mar 31, 2012
27,939
Interesting way to look at it, and maybe even more apt based on the way the question was asked.

I didn’t think of a laser, but probably because the oscillation of the beam in the cavity doesn’t change the frequency of the emitted light, it just amplifies it. Though that does make an oscillator at light speed, and so it is “useful”. But it isn’t really in the same vein as what I think the TS was asking about.
I still don't see how that makes it an oscillator at light speed (or what that phrase even means). The electromagnetic waves coming out of a laser travel at the same speed as the electromagnetic waves coming off a 1 MHz radio tower (barring slight differences due to wavelength-dependent index of refractions, be we can always move to a vacuum environment). So how is the first somehow oscillating at light speed and the second isn't?

#### Ya’akov

Joined Jan 27, 2019
6,858
I still don't see how that makes it an oscillator at light speed (or what that phrase even means). The electromagnetic waves coming out of a laser travel at the same speed as the electromagnetic waves coming off a 1 MHz radio tower (barring slight differences due to wavelength-dependent index of refractions, be we can always move to a vacuum environment). So how is the first somehow oscillating at light speed and the second isn't?
The light bouncing back and forth in the laser cavity would be moving at the speed of light (minus velocity factor considerations). That light could be said to be oscillating. So, then any laser that uses a Fabry-Pérot cavity could be said to be using an optical oscillator—not to produce the radiation but to effect the amplification.

#### Ian0

Joined Aug 7, 2020
6,735
The light bouncing back and forth in the laser cavity would be moving at the speed of light (minus velocity factor considerations). That light could be said to be oscillating. So, then any laser that uses a Fabry-Pérot cavity could be said to be using an optical oscillator—not to produce the radiation but to effect the amplification.
Isn't it amplifier with a frequency-dependent feedback loop, like any other oscillator?

#### Ya’akov

Joined Jan 27, 2019
6,858
Isn't it amplifier with a frequency-dependent feedback loop, like any other oscillator?
The fundamental wavelength of the laser depends on the light source. For example, HeNe lasers use helium-neon tubes to produce the light. The cavity causes the emitted photons to bounce back and forth through the tube, excited more photon output.

There is some effect on output frequency, though not being an expert on lasers I don't quite understand it. If the mirrors are not perfectly phase coherent, the beam wavelength can drift, I think.

#### drjohsmith

Joined Dec 13, 2021
549
Do you think we've answered the original question ?

#### Ya’akov

Joined Jan 27, 2019
6,858
Do you think we've answered the original question ?
I took #7 to indicate that we had.

#### Janis59

Joined Aug 21, 2017
1,538
Thanks a lot - very good link to the article what named the accurate references to THz radiation sources and detecting sensors. Good job!
I mean the doi.org/10.1038/nmat708 (sci-hub contains the full that text)