Pockels Faster than Light Effects
Ralph Sansbury
The experiment described here shows that there are effects that travel
faster than the speed of light that influence the amplitude of light pulses
received at a photodiode. This is the second of a series of experiments that
show this effect. (In this second set of experiments, cables that were of
unequal length in the first set of experiments were made equal and shorter
pulses and smaller distances were employed)
The following first two scope pictures show the photodiode response to
light from a laser when the Pockels shutter in front of the laser is pulsed
open for a few nanoseconds and the shutter in front of the photodiode is
always open and vice versa. The 2.5V control pulse on channel one, when
further activated, turns on a higher voltage pulse on the shutter Pockels
shutter which allows transmission when on, and blocks transmission when off.
The pulse on channel two does the same thing on the Pockels shutter in
front of the photodiode.
The activation of a control pulse means that a bias voltage is first
applied to the capacitor plates between which are the Pockels crystals, so
as to produce minimal transmission of light through the crystals and a
polarizer and then a high voltage electronic pulse is turned on which when
combined with the controlling low voltage pulse, removes the suppressing
voltage momentarily. The relative timing of the electronic pulses is shown
in the 7th and 8th scope pictures. The effect of this timing and the equal
length cables between the low voltage pulse generator channels and the high
voltage pulse supply is shown by the scope pictures of the light pulses.
(Cable timings of 2 six foot cables and 2 twenty one foot cables are
shown in scope pictures 9-12. (Two 50 Ohm six foot cables were used to
connect the low voltage pulse generator outputs to two scope channels and
one six foot 50 Ohm cable connected the photodiode to the third scope
channel. The 21 foot, 50 Ohm cables connected the same two pulse generator
outputs (through T connectors) to the electrooptic modulators connected in
turn to Pockels crystal capacitor plates by 22.25 inch cables, one in front
of the laser and one in front of the photodiode)
The third scope picture shows what happens when minimal transmission is
produced by both Pockels shutters except that the shutter in front of the
photodiode is pulsed. Thus the voltage pattern is largely emi
(electromagnetic interference) induced by the high voltage pulsing circuit
on the photodiode circuit. This means that the light produced by this
electronic pulse as shown in the second scope picture is the upper part of
the first spike.
The fourth scope picture shows what happens when a piece of opaque
cardboard is placed at the exit of the Pockels shutter in front of the
photodiode.
Results
The fifth scope picture shows what happens when both Pockels shutters are
pulsed open at the same time, namely that the Pockels shutter in front of
the photodiode being open briefly while the shutter in front of the laser is
open briefly for the same time, produces more light on the photodiode than
when the shutter in front of the photodiode is kept closed (scope picture 6)
and more light of course than when the laser shutter is kept closed(3) or
the light beam is blocked at the exit of the Pockels shutter in front of the
photodiode(4).
One can conclude that opening the photodiode shutter for ten to fifteen
nanoseconds at the same time as the laser shutter for about the same
duration, increases the responsivity of the photodiode to the light pulse
from the laser.(Note that the duration of the high voltage pulse is
controlled by the high voltage pulser while the initiation time of the high
voltage pulses is controlled by the low voltage pulser.) This is the case
even though the photodiode shutter is closed before the expected time of
arrival of the so called train of photons at the photodiode shutter. That
this is indeed the case is obvious by comparing the first two scope
pictures. That some small constant level of light on the photodiode may be
necessary for this effect to occur is suggested by comparing scope pictures
3 and 4.
This indicates that light arriving at the photodiode before the delay
time required by the speed of light premise, can increase the magnitude of
light arriving at the photodiode at the expected time of arrival.
Thus, light may not be a wave front or probabilistic photon moving
through space but rather the cumulative effect of instantaneous forces at a
distance. These forces produce systematic effects below noise before the
light or other electromagnetic radiation increases in amplitude sufficiently
to be distinguished from noise.
A discussion of the Pockels effect and the theory of what happens in the
Pockels crystals and polarizer crystals and the silicon photodiode to
produce these observed effects is given below.
Scope pix can be emailed in Word 95 format until the Pockels2 file is
posted on the web page
http://www.bestweb.net/~sansbury
Uncle Al
Ralph Sansbury wrote:
>
> Pockels Faster Than Light Effects
> The experiment described here shows that there are effects that travel
> faster than the speed of light that influence the amplitude of light pulses
> received at a photodiode. This is the second of a series of experiments that
> show this effect.
[snip]
Put a sock in it. Physics groups don't even bother to call you a jerk
any more.
--
Uncle Al
http://www.mazepath.com/uncleal/
http://www.ultra.net.au/~wisby/uncleal/
http://www.guyy.demon.co.uk/uncleal/
(Toxic URLs! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
Ralph Sansbury
Uncle Al <Uncl...@hate.spam.net> wrote in message
news:38B15F5D...@hate.spam.net...
>
>
> Ralph Sansbury wrote:
> [snip]
Pockels Faster Than Light Effects
The experiment described here shows that there are effects that travel
faster than the speed of light that influence the amplitude of light pulses
received at a photodiode. This is the second of a series of experiments that
pulses and smaller distances were employed)
The following first two scope pictures show the photodiode response to
light from a laser when the Pockels shutter in front of the laser is pulsed
is always full open and vice versa. The 2.5V control pulse on channel two,
when further activated, turns on a higher voltage pulse on the Pockels
shutter which allows maximal transmission when on, and minimizes
transmission when off. The pulse on channel one does the same thing on the
Pockels shutter in front of the photodiode.
The activation of a control pulse means that a bias voltage is first
applied to the capacitor plates between which are the Pockels crystals, so
as to produce minimal transmission of light through the crystals and a
polarizer and then a high voltage electronic pulse is turned on which when
combined with the controlling low voltage pulse, removes the suppressing
voltage momentarily. The relative timing of the electronic pulses is shown
in the 7th and 8th scope pictures. The effect of this timing and the equal
length cables between the low voltage pulse generator channels and the high
difference in the time of occurrence of the light pulses is thus due to the
14 foot distance between the laser exit hole and the photodiode(reversing
the crystals produces no change).
(Cable timings of 2 six foot cables and 2 twenty one foot cables are
shown in scope pictures 9-12. (Two 50 Ohm six foot cables were used to
connect the low voltage pulse generator outputs to two scope channels and
one six foot 50 Ohm cable connected the photodiode to the third scope
channel. The 21 foot, 50 Ohm cables connected the same two pulse generator
laser, the other near the photodiode, connected in turn to Pockels crystal
capacitor plates by 22.25 inch cables, one in front of the laser and one in
front of the photodiode)
The third scope picture shows what happens when minimal transmission is
produced by both Pockels shutters except that the shutter in front of the
photodiode is pulsed. Thus the voltage pattern is largely emi
(electromagnetic interference) induced by the high voltage pulsing circuit
on the photodiode circuit. This means that the light produced by this
electronic pulse as shown in the second scope picture is the upper part of
The fourth scope picture shows what happens when a piece of opaque
cardboard is placed at the exit of the Pockels shutter in front of the
photodiode.
Results
The fifth scope picture shows what happens when both Pockels shutters are
pulsed open at the same time, namely that the Pockels shutter in front of
the photodiode being open briefly while the shutter in front of the laser is
open briefly for the same time, produces more light on the photodiode than
when the shutter in front of the photodiode is kept closed (scope picture 6)
and more light of course than when the laser shutter is kept closed(3) or
the light beam is blocked at the exit of the Pockels shutter in front of the
photodiode(4).
Similar results were obtained when the photodiode shutter and photodiode
were moved 3 feet further from the laser shutter and laser.(scope pictures
12 through 17)
One can conclude that opening the photodiode shutter for ten to fifteen
nanoseconds at the same time as the laser shutter for about the same
duration, increases the responsivity of the photodiode to the light pulse
from the laser.(Note that the duration of the high voltage pulse is
controlled by the high voltage pulser while the initiation time of the high
voltage pulses is controlled by the low voltage pulser.) This is the case
even though the photodiode shutter is closed (minimized) before the expected
time of arrival of the so called train of photons at the photodiode shutter.
That this is indeed the case is obvious by comparing the first two scope
pictures. That some small constant level of light on the photodiode may be
necessary for this effect to occur is suggested by comparing scope pictures
3 and 4. (Scope picture 11 shows the response of the photodiode when the
photodiode shutter is pulsed full open after a delay at the expected time of
arrival of the light.)
This indicates that light arriving at the photodiode before the delay
time required by the speed of light premise, can increase the magnitude of
light arriving at the photodiode at the expected time of arrival.
Thus, light may not be a wave front or probabilistic photon moving
through space but rather the cumulative effect of instantaneous forces at a
distance. These forces produce systematic effects below noise before the
light or other electromagnetic radiation increases in amplitude sufficiently
to be distinguished from noise.
A discussion of the Pockels effect and the theory of what happens in the
Pockels crystals and polarizer crystals and the silicon photodiode to
produce these observed effects is given below.
Uncle Al
Ralph Sansbury wrote:
>
> Uncle Al <Uncl...@hate.spam.net> wrote in message
> news:38B15F5D...@hate.spam.net...
Uncle Al wrote "Put A Sock In It." Do you have a problem with
comprehension?
Matthew Montchalin
|Uziel wrote:
|> Uncle Al, please elaborate on why you have a problem with Ralph.
|> Having only read his post and your response it seems to me that
|> you are the crank and he is not, although this may not be the case.
|
|His spew has been spammed all over Usenet science groups and
|throughly, punctiliously discredited on technical grounds. Look
|up the fuming pile in Deja News. It's big and stinky. He is now
|branching out into peripheral newsgroups. Look at the distribution
|list. Enough is bloody enough.
You mean he shouldn't be given a medal?
Uziel
read his post and your response it seems to me that you are the crank and he
is not, although this may not be the case.
Uncle Al <Uncl...@hate.spam.net> wrote in message
news:38B1B8F0...@hate.spam.net...
>
>
> Ralph Sansbury wrote:
> >
> > Uncle Al <Uncl...@hate.spam.net> wrote in message
> > news:38B15F5D...@hate.spam.net...
>
Uncle Al
Uziel wrote:
>
> Uncle Al, please elaborate on why you have a problem with Ralph. Having only
> read his post and your response it seems to me that you are the crank and he
> is not, although this may not be the case.
His spew has been spammed all over Usenet science groups and
throughly, punctiliously discredited on technical grounds. Look up
the fuming pile in Deja News. It's big and stinky. He is now
branching out into peripheral newsgroups. Look at the distribution
list. Enough is bloody enough.
Reality is not decided by majority vote, screaming on a soapbox, or
being a prolix jackass on Usenet. He's wrong. He's technically
wrong. His hundreds of lines of repetitious crap have no business
being here.
Uziel
Uncle Al <Uncl...@hate.spam.net> wrote in message
news:38B1F8A5...@hate.spam.net...
Ralph Sansbury
snip
Tom,
I dont remember exactly what you said but you are right that I have
changed my tune.
The effect of the blocking voltage applied to the Pockels crystal at the
photodiode, may be to change 180 degrees the phase of the radiation received
(but not fully detectable) from the source and scattered forward from the
crystal so that when it interacts at the photodiode with the source
radiation not blocked at the laser, it tends to cancel and reduce further
buildup. But if there has been enough buildup, then the cancelling effect is
not completely successful and this radiation builds up to a detectable
level.
This anyway is how at the moment, I interpret what is happening. Let me
know your thoughts.
Ralph
----- Original Message -----
From: MadToM <mad...@ipof.fla.net>
To: <sans...@bestweb.net>
Sent: Monday, February 21, 2000 12:14 PM
Subject: Re: Pockels Faster than Light Effects
> Hello Ralph
>
> I just read your new post to the relativity news group.
> I was wondering what was taking you so long to finish with your new
> experiment, and had almost concluded that you must have not found
> anything. But that dose not seem to be the case.
> I read your post and it dose seem that you have changed your tune a
> little, it almost sounds like I was right about the pocket cell.
> So I am writing you this e-mail to ask you straight out.
> Was I wrong, right, almost???
> MadTom
>
Scharnberg F_alk
On Tue, 22 Feb 2000, Ralph Sansbury wrote:
<snip>
> ----- Original Message -----
> From: MadToM <mad...@ipof.fla.net>
> To: <sans...@bestweb.net>
> > Hello Ralph
> >
> > I just read your new post to the relativity news group.
<snip>
RALPH !
Why do you :
1. think that anyone is interested in your *private* communication ?
2. post this to newsgroups that are *not* the relativity forum, where
your companion sits ?
Shall i post my emails in here as well ??
F alk
Roland Smith
<sans...@bestweb.net> wrote:
[Snip]
> The following first two scope pictures show the photodiode response to
>light from a laser when the Pockels shutter in front of the laser is pulsed
>open for a few nanoseconds and the shutter in front of the photodiode is
>always open and vice versa. The 2.5V control pulse on channel one, when
>further activated, turns on a higher voltage pulse on the shutter Pockels
>shutter which allows transmission when on, and blocks transmission when off.
>The pulse on channel two does the same thing on the Pockels shutter in
>front of the photodiode.
[Snip]
A couple of questions Ralph.
(1) Just why are your diode signals so pathetically small (trying to
do mv measurements in a lab with a pulsed HV generator is a really
BAD idea). I thought you were going to use a lens in your
"improved" experiment to get better signal to noise.
(2) Why do your photodiode signals go NEGATIVE ? Your diode should
produce positive going signals only. Negative signals = noise or
ringing in your system.
Roland
MadToM
I looked up my old post And have listed some of them here.
http://x41.deja.com/getdoc.xp?AN=556779430&CONTEXT=951344020.994181128&hitnum=13
http://x41.deja.com/getdoc.xp?AN=559469126&CONTEXT=951344020.994181128&hitnum=6
http://x41.deja.com/getdoc.xp?AN=560654598&CONTEXT=951344020.994181128&hitnum=3
From reading your resent post I get the impression that you implemented
a version
of my question and seem to have reached conclusions similar to my
predictions.
So, my question bellow. I still have a million questions, and I will
find the time
to look over the material at your web page in detail.
MadTom
Ralph Sansbury wrote:
>
> Uncle Al <Uncl...@hate.spam.net> wrote in message
> news:38B1B8F0...@hate.spam.net...
>
> snip
> Tom,
> I dont remember exactly what you said but you are right that I have
> changed my tune.
> The effect of the blocking voltage applied to the Pockels crystal at the
> photodiode, may be to change 180 degrees the phase of the radiation received
> (but not fully detectable) from the source and scattered forward from the
> crystal so that when it interacts at the photodiode with the source
> radiation not blocked at the laser, it tends to cancel and reduce further
> buildup. But if there has been enough buildup, then the cancelling effect is
> not completely successful and this radiation builds up to a detectable
> level.
> This anyway is how at the moment, I interpret what is happening. Let me
> know your thoughts.
> Ralph
>
> ----- Original Message -----
> From: MadToM <mad...@ipof.fla.net>
> To: <sans...@bestweb.net>
> Sent: Monday, February 21, 2000 12:14 PM
> Subject: Re: Pockels Faster than Light Effects
>
> > Hello Ralph
> >
> > I just read your new post to the relativity news group.
David Moodie
Ralph Sansbury <sans...@bestweb.net> wrote in message
news:Ho2s4.6104$JQ.3...@monger.newsread.com...
> Pockels Faster Than Light Effects
>
> Scope pix can be emailed in Word 95 format until the Pockels2 file is
> posted on the web page
> http://www.bestweb.net/~sansbury
>
Perhaps I should first take the opportunity to apologise to all those who
would prefer to see this thread die, but I do have some genuine queries
concering the results and what I believe may be a completely rational
explanation for them.! In the past I've resisted the temptation to join in
as soo much was hand waving generalisation, which offered nothing to the
argument on either side, although I have offered a few suggestions for
improving the experiment, most of which I'd still like to see, the most
significant of them are also referred to in this post.
Having read the occasional post on this thread over the years I'm pleased to
see a little bit more information coming rather than the usual rhetoric, and
it did provide me with something different to read on my journey home.
Having said that the experimental procedure and recording could still be
significantly improved, the power levels incident on the photoreceiver are
still inadequate, additional gain at least should follow the photoreceiver,
even if there are problems increasing the optical power levels.
Now back to the "new" results presented by Ralph in his latest Pockels
paper, and what I believe is a rational (or conventional) explanation of the
results presented.
Of particular interest, in my opinion, are the traces shown in Figure 7,
which displays the actual voltage level on the Pockels cell.
First a brief description of the transfer function of an electro-optic
modulator (Pockels cell), with appropriate polarisors.
Generally speaking the transmission of a Pockels cell is given by
T=sin^2((pi/2). (V/Vpi))
where V is the applied voltage and Vpi is the half wave voltage, which is
the voltage required to induce a pi phase difference between two orthogonlly
polarized input waves. This voltage will achieve a change in transmission
from
minimum to maximum. (For more information see texts such as Wilson and
Hawkes: Optoelectronics and Introduction or Yariv : Optical Electronics, and
many others.)
Vpi is dependent upon the electro-optic coefficient of the crystal, the
separation between the electrodes and the length of the cell.
Now, if I am interpreting the traces correctly, the results presented in
Figure 7 of Ralph's latest release show a DC bias of 300V on the cell , it
is noted in the text that a DC voltage is applied to realise minimum
transmission. A positive going pulse of approx. 140V is then applied to the
cell in order to switch to maximum transmission. Fair enough. The voltage
on the cell then appears to decay roughly exponentially to zero after the
appearance of this pulse. The trace is titled as the laser shutter, but I'm
assuming that the cell at the photoreceiver has a similar response also.
It is noted that at a time T of approx. 58ns the voltage on the cell is
approx. 160V, or alternatively 300-140. given the symmetrical nature of the
response of a Pockels cell, when appropriately biased, this also corresponds
to a maximum in transmission, This point in time also corresponds to the
time when a pulse (of extremely low voltage) is seen in Figure 5, which I
believe is the apparent anomalous result that has been referred to for so
long.
With regard to this I would suggest that the cells be fully characterised
with respect to applied voltage in order to clarify the results. Also, the
work presented has improved slightly with more info and less talk but it
would still have been beneficial to present diagrams to accompany the
appropriate graphs, and of course improve the signal levels from the
photodiode, via improvements to the optical system, and by further
amplification of the photoreceiver signal,as mentioned previously
Some question that may be given in reply.
Why don't we see this pulse on the initial traces (1-3)?. Perhaps we do,
e.g small peak (after main peak) on trace 1, significant (well as
significant as any other signal) peak at his point in time on trace 2. It
is also difficult to accurately determine the presence or not of a secondary
peak due to the significant emi and ringing on the receiver, another case
for increased gain, and reduction of the optical losses.
I'm not quite sure what is happening in a few other traces as they are
inadequately captioned. It would also be nice to see more traces along the
lines of Figure 7, with the actual voltage applied to the cell in order to
determine if this theory holds.
What if the apparent response of the cell isn't as I have anticipated, i.e.
we don't see a sin squared response with applied voltage. In this case then
the characterisation of the cells may be wrong, it should be noted that
electro-optic crystals can also be used as beam deflectors, and what may be
happening with the cell is a combination of attenuation and movement of the
beam. This can be checked by removing output polarisors and using a
quadrant detector to examine the beam characteristics, which can be
performed as a DC measurement. According to my interpretation a minimum in
transmittance should also be seen for a DC voltage level of about 60V. If
this is not the case then are you really applying the correct voltage to
achieve max. transmission? You do have relatively long path lengths, and any
misalignment of the first cell could cause movement in the beam position
which is why perhaps, you see a max transmission for the specified voltage,
as any further increase actually takes the beam off of the detector, which
has a relatively small area. I could go on along these lines but would
prefer that you provide the appropriate characterisation for the cells with
DC voltage which would help to clarify the situation.
Comments Please
regards
David
ps is just me (or a colloquialism at least) or is anyone else aware of the
use of pockel, to mean to slightly adjust your experimental results to agree
with theory, for example moving a point slightly to give a better curve fit
, or expanding your error margins. This is widely referred to as the pockel
factor with people I know. I should say that my use of this (the term, not
the actual action, of course), stemmed to well before Ralph's results came
to light, and was often come across as a post grad when checking undergrad
lab reports, who even without extensive optics knowledge could put the
pockel effect to good use.
Ralph Sansbury
----- Original Message -----
From: David Moodie <d.mo...@primex.co.uk>
Newsgroups: sci.optics,sci.astro,sci.physics.relativity,sci.physics
Sent: Thursday, February 24, 2000 4:19 AM
Subject: Re: Pockels ...a rational explanation?
David,
Thank you for your interest and your expertise.
Re: your objections
>
> It is noted that at a time T of approx. 58ns the voltage on the cell is
> approx. 160V, or alternatively 300-140. given the symmetrical nature of
the
> response of a Pockels cell, when appropriately biased, this also
corresponds
> to a maximum in transmission, This point in time also corresponds to the
> time when a pulse (of extremely low voltage) is seen in Figure 5, which I
> believe is the apparent anomalous result that has been referred to for so
> long.
snip
> Some question that may be given in reply.
> Why don't we see this pulse on the initial traces (1-3)?. Perhaps we do,
> e.g small peak (after main peak) on trace 1, significant (well as
> significant as any other signal) peak at his point in time on trace 2. It
> is also difficult to accurately determine the presence or not of a
secondary
> peak due to the significant emi and ringing on the receiver, another case
> for increased gain, and reduction of the optical losses.
> I'm not quite sure what is happening in a few other traces as they are
> inadequately captioned. It would also be nice to see more traces along the
> lines of Figure 7, with the actual voltage applied to the cell in order to
> determine if this theory holds.
Not sure what you mean here. The fig 5 light pulse resembles 1) the fig 1
light pulse, and 2) the second emi spike in fig 3 and fig 4 when the light
from the laser is partially or wholly blocked.
And this fig 5 light pulse ( the part that is greater then the emi
spikes) only occurs if the photodiode shutter is open at the same time as
the laser shutter even though the photodiode shutter is then closed before
the light pulse has supposedly 'reached' the photodiode or photodiode
shutter.
> What if the apparent response of the cell isn't as I have anticipated,
i.e.
> we don't see a sin squared response with applied voltage. In this case
then
> the characterisation of the cells may be wrong, it should be noted that
> electro-optic crystals can also be used as beam deflectors, and what may
be
> happening with the cell is a combination of attenuation and movement of
the
> beam.
Are you saying that the fig 5 light pulse is due to attenuation and
movement
of the beam where the beam is the pulse(fig1) produced by the laser shutter?
But even
if this is what is being done by the photodiode shutter it is being done
before the beam
has arrived at the photodiode shutter and the photodiode and therefore is a
superluminal effect,yes?
> This can be checked by removing output polarisors and using a
> quadrant detector to examine the beam characteristics, which can be
> performed as a DC measurement. According to my interpretation a minimum
in
> transmittance should also be seen for a DC voltage level of about 60V. If
> this is not the case then are you really applying the correct voltage to
> achieve max. transmission? You do have relatively long path lengths, and
any
> misalignment of the first cell could cause movement in the beam position
> which is why perhaps, you see a max transmission for the specified
voltage,
> as any further increase actually takes the beam off of the detector, which
> has a relatively small area. I could go on along these lines but would
> prefer that you provide the appropriate characterisation for the cells
with
> DC voltage which would help to clarify the situation.
Couldn't afford to keep the rented test equipment any longer so cant make
these tests even
if you could probably give me advice on how to do them.
Ralph
Ralph Sansbury
----- Original Message -----
From: Roland Smith <Roland-an...@ic.ac.uk>
Newsgroups: sci.optics,sci.astro,sci.physics.relativity,sci.physics
Sent: Tuesday, February 22, 2000 3:40 AM
Subject: Re: Pockels Faster than Light Effects
> On Mon, 21 Feb 2000 03:36:07 GMT, "Ralph Sansbury"
> <sans...@bestweb.net> wrote:
>
> [Snip]
>
> > The following first two scope pictures show the photodiode response
to
> >light from a laser when the Pockels shutter in front of the laser is
pulsed
> >open for a few nanoseconds and the shutter in front of the photodiode is
> >always open and vice versa. The 2.5V control pulse on channel one, when
> >further activated, turns on a higher voltage pulse on the shutter Pockels
> >shutter which allows transmission when on, and blocks transmission when
off.
> >The pulse on channel two does the same thing on the Pockels shutter in
> >front of the photodiode.
>
> [Snip]
>
> A couple of questions Ralph.
>
> (1) Just why are your diode signals so pathetically small (trying to
> do mv measurements in a lab with a pulsed HV generator is a really
> BAD idea).
Couldn't think of an alternative.
I thought you were going to use a lens in your
> "improved" experiment to get better signal to noise.
>
I did get two lenses that worked and the large lens by itself worked
But didn't think it was necessary so long as there was a clear distinction
between light and emi on the scope pictures.
Also I wanted to reduce the number of factors influencing the results.
> (2) Why do your photodiode signals go NEGATIVE ? Your diode should
> produce positive going signals only. Negative signals = noise or
> ringing in your system.
Got rid of as much noise as I could. Maybe this is in the cables and
connections. We dont have to be absolutists at
this stage. The superluminal effect is clearly above
noise and for practical applications there is clearly room for improvement.
Ralph
Bob May
what it's doing. Photodetectors just don't act that way! However,
crosscoupling of signals happens exactly that way! Average power of a
crosscoupled signal is 0 (equal power above and below the otherwise
expected signal) over time as it is AC coupled into the other line.
The proper signal should be something that shows a one way (I could
have said positive or negative here but then the argument could be for
the other!) direction signal that doesn't balance with a signal of the
other direction. As I have said before, get someone who's a good tech
and have him straighten out your problems and do a timing analysis of
the delays of your apparatus. After you get that done, you will see
that light does indeed go at ~1ns/ft. of distance.
Uncle Al has seen so much of what Ralphie is trying to do that he is
just frustrated that such silliness happens so easily and it's like
Mole Bashing down at the fair. As often as you bash one down, another
pops up which needs the same treatment. His concept is to bash it
down so hard it doesn't come up again which unfortunately doesn't work
as the moles are always new ones. Ralphie just is still getting
bashed for his silliness.
--
Bob May
I don't read attachments to posts as they may give me a
virus If I expect an attachment from you I will open it..
You may have a brilliant thought but if you put it into an
attachment I won't read it and thus both you and I lose.
I don't like to say it but unfortunatly, there are those who
insist upon being nasty to the rest of us. Bob May
David Moodie
>
>
> David,
>
> Thank you for your interest and your expertise.
> Re: your objections
>
> >
> > approx. 160V, or alternatively 300-140. given the symmetrical nature of
> the
> > response of a Pockels cell, when appropriately biased, this also
> corresponds
> > to a maximum in transmission, This point in time also corresponds to the
> > time when a pulse (of extremely low voltage) is seen in Figure 5, which
I
> > believe is the apparent anomalous result that has been referred to for
so
> > long.
> > Some question that may be given in reply.
> > Why don't we see this pulse on the initial traces (1-3)?. Perhaps we
do,
> > e.g small peak (after main peak) on trace 1, significant (well as
> > significant as any other signal) peak at his point in time on trace 2.
It
> > is also difficult to accurately determine the presence or not of a
> secondary
> > peak due to the significant emi and ringing on the receiver, another
case
> > for increased gain, and reduction of the optical losses.
> > I'm not quite sure what is happening in a few other traces as they are
> > inadequately captioned. It would also be nice to see more traces along
the
> > lines of Figure 7, with the actual voltage applied to the cell in order
to
> > determine if this theory holds.
>
1
> light pulse, and 2) the second emi spike in fig 3 and fig 4 when the light
> from the laser is partially or wholly blocked.
> And this fig 5 light pulse ( the part that is greater then the emi
> spikes) only occurs if the photodiode shutter is open at the same time as
> the laser shutter even though the photodiode shutter is then closed before
> the light pulse has supposedly 'reached' the photodiode or photodiode
> shutter.
>
to preempt your objections. The time T refered to in my original reply was
also incorrect it should have been about 76ns.
My fundamental point is, that, assuming the cell before the photodiode has a
similar response to the one shown in Fig. 7 then the cell may NOT be closed
at the point in time where the anomolous peak is seen. It may be partially
open.
From the trace in Fig 7 it appears that after opening the cell the voltage
on it decays to zero. The point which I estimate to conicide with the pulse
corresponds to a voltage level (approx. 160V) which may should also realise
max. transmission. My estimation of the time between the pulse and the
possible secondary transmission window is about 26-28ns, taken from Trace 4
on Fig 7, that is the time from the voltage level at 440V (peak of the
pulse) and the 160V level on teh decaying pulse. It is possible that on Fig
1 the small pulse at approx 108ns is due to this.
Looking at Fig. 2. for the photodiode cell being pulsed then there is
obviously considerable diference in the response of the two cells as seen by
the difference in the pulse shape and amplitude. What I assume is refered
to as the second emi spike, occuring at exactly the same time as the laser
pulse is expected !?, makes it expetionally difficult to determine emi
content and real signal content at this point in time.
. I take it that I am at least looking at the correct signal, which occurs
at approx. 76ns. It does appear to show some general trends though, for
example the amplitude decreases from fig 2 to fig 3 and from fig 3 to 4, as
the laser power is reduced and then removed, but this is pretty inconclusive
given teh low signal levels involved. the question is then is the difference
in amplitude betweem figs 2 and 5 significant? Rersonally I find it
impossible to say.
regarding the characterisation of the cells and some other measurements I
suggested, you do not need expensive test equipment to perform them, only a
high voltage supply 0 to 500V and a DC photoreceiver. If you still have the
voltage source originally used to bias the cells then you could put together
a photoreceiver for about 10-15 dollars. This really is such a basic test
that it should have been performed before conducting any experiments in my
opinion. alternatively did the manufacturer of the devices not supply any
characterisation data? You don't really address this point in your previous
reply which was really the whole point of my post, that the photodetector
cell may be partially transmitting at the time the anomalous pulse. The
degree of transmittance is not well controlled as it is dependent on the
decay of the DC signal to zero, rather than an applied pulse. While this is
not easy to determine given the lack of equipment, the characterisation of
the cells with DC applied signal woudl go some way to resolving the issue.
regards
David
Roland Smith
<sans...@bestweb.net> wrote:
>> (2) Why do your photodiode signals go NEGATIVE ? Your diode should
>> produce positive going signals only. Negative signals = noise or
>> ringing in your system.
>
> Got rid of as much noise as I could. Maybe this is in the cables and
>connections. We dont have to be absolutists at
>this stage. The superluminal effect is clearly above
>noise and for practical applications there is clearly room for improvement.
>Ralph
Ralph, you just don't seem to understand the implication of this. You
SHOULD get a nice clean all positive (or all negative) pulse out of
your photodiode from an optical signal. The pulse polarity depends on
how your diode is wired up. If you see a ringing signal that goes
positive and negative then something is WRONG.
A signal that went large positive at the start, than rang and decayed
could just be a bad piece of impedance matching. This is NOT what you
have. You have a growing and then decaying series of positive and
negative swings, the classic form of an EM noise burst that I see
every day from Pockells cells in my lab.
If you are going to do the experiment, please go and get some real
electronics expertese in the lab.
Roland.
Ralph Sansbury
David Moodie <d.mo...@primex.co.uk> wrote in message
news:895pbi$npl$1...@supernews.com...
>
> Ralph Sansbury <sans...@bestweb.net> wrote in message
> news:toet4.3998$Zh4.6...@newshog.newsread.com...
> My fundamental point is, that, assuming the cell before the photodiode has
a
> similar response to the one shown in Fig. 7 then the cell may NOT be
closed
> at the point in time where the anomolous peak is seen. It may be partially
> open.
If you look at the unlabeled fig 12 and 13 which correspond to fig 1 an
fig 2 except the photodiode and shutter are placed further away, 17and 18 ft
versus 13 and 14ft approximately, from the laser you see that the light
pulses more clearly do not overlap and the same anomalous peak occurs albeit
with lesser light intensity.
Also when the laser shutter bias was changed to transmit more light on a
continual basis but still contained a pulse, the pulse shown on the
photodiode jumped from the location of the anomolous peak and the location
of the laser shutter pulse(fig 1) to the location of the phtd. shutter
pulse(fig2)( I would need a video camera to show this 'jump')
If you saw the 'jump' referred to above you would be perhaps more
convinced that there is a real difference.
I agree it is small but it is on top of the noise and it is repeated
thousands of times a second for many seconds. Statistically the small, 3 and
2 mV differences are significant to the .99999999999 level.
Personally, I dont think one can pretend this effect doesn't exist.
Of course if a stronger laser was used the effect would be more dramatic
Or perhaps if the lenses which I have were used the effect at these
distances would have been 2 times greater. Unfortunately I have had to
return the rented test and electrooptic modulator equipment and dont have
the funds to rent such equipment again.
> regarding the characterisation of the cells and some other measurements I
> suggested, you do not need expensive test equipment to perform them, only
a
> high voltage supply 0 to 500V and a DC photoreceiver. If you still have
the
> voltage source originally used to bias the cells then you could put
together
> a photoreceiver for about 10-15 dollars. This really is such a basic test
> that it should have been performed before conducting any experiments in my
> opinion. alternatively did the manufacturer of the devices not supply any
> characterisation data? You don't really address this point in your
previous
> reply which was really the whole point of my post, that the photodetector
> cell may be partially transmitting at the time the anomalous pulse. The
> degree of transmittance is not well controlled as it is dependent on the
> decay of the DC signal to zero, rather than an applied pulse. While this
is
> not easy to determine given the lack of equipment, the characterisation of
> the cells with DC applied signal woudl go some way to resolving the issue.
Isn't the characterization relevant here given by the differences
between the pictures of the photodiode responses?
The time between the beginning of the triggers and the observed pulses,
fig 1 and fig 2 show that the light
from the pulsed laser shutter arrives about12.5 ns later; in fig12 and 13,
20ns later when compared to the arrival
time of pulses from the photodiode shutter. These times, and the duration of
the pulses, tell us when the shutters are open and closed.
Now when both shutters are biased to be almost closed, the laser shutter
pulse does not produce an effect above noise but when the photodiode
shutter is pulsed, a pulse above noise(thermal and emi) occurs where the
laser shutter pulse should-- not where the photodiode shutter pulse should.
Doesn't this mean that the photodiode shutter pulse effect is due to the
opening of the photodiode shutter at the same time as the laser shutter even
though it is closed before light arives at the photodiode?
You point out that the anomalous effect pulse occurs on top of an emi
spike.
But of course so do the pure laser shutter pulse and the pure photodiode
shutter pulse
but we dont say that the emi spike is part of the cause of these light
pulses!
Ralph
Ralph Sansbury
Roland Smith <Roland-an...@ic.ac.uk> wrote in message
news:=8e2OEcfXq6nga...@4ax.com...
> On Thu, 24 Feb 2000 18:11:53 GMT, "Ralph Sansbury"
> <sans...@bestweb.net> wrote:
>
>
> >> (2) Why do your photodiode signals go NEGATIVE ? Your diode should
> >> produce positive going signals only. Negative signals = noise or
> >> ringing in your system.
> >
> > Got rid of as much noise as I could. Maybe this is in the cables and
> >connections. We dont have to be absolutists at
> >this stage. The superluminal effect is clearly above
> >noise and for practical applications there is clearly room for
improvement.
> >Ralph
>
> Ralph, you just don't seem to understand the implication of this. You
> SHOULD get a nice clean all positive (or all negative) pulse out of
> your photodiode from an optical signal. The pulse polarity depends on
> how your diode is wired up. If you see a ringing signal that goes
> positive and negative then something is WRONG.
Partly this cleanliness of the pulses is a matter of the 2mV/division
and partly this is a matter of working with different devices than you are
working with.
The only negative going pulses I see are those due to unmatched
impedance reflections in the low voltage pulses and I dont see any clear
negative going voltages on the photodiode that are outside the range of
thermal noise or effects induced by these unmatched impedance reflections.
If you see any such please specify.
Whatever is wrong and the degree to which it is wrong is shown. You seem
to be implying that a cleaner signal would be evident if there were not
loose wire connections or better equipment or I was as expert as you and
that maybe these effects are somehow related to the superluminal effect.
But you dont seem to understand that bad impedance matching can produce
these negative going pulses and you dont seem to understand the basic laws
of electromagnetic induction and how these and other emi is produced in the
photodiode cable. Because that is what is obviously going on. (Perhaps you
should bone up on basic electromagnetics) Your claim that it does not come
under the heading of emi or thermal noise limitations is bogus.
But there is something else going on which is the point of the
experiment, namely, the 2 & 3mV anomalous pulses which are significantly
different from the thermal and emi noise at the .9999999 level.
Let me quote from my reply to David Moodie.
"The time between the beginning of the triggers and the observed pulses,
fig 1 and fig 2 show that the light
from the pulsed laser shutter arrives about12.5 ns later; in fig12 and 13,
20ns later when compared to the arrival
time of pulses from the photodiode shutter. These times, and the duration of
the pulses, tell us when the shutters are open and closed.
Now when both shutters are biased to be almost closed, the laser shutter
pulse does not produce an effect above noise but when the photodiode
shutter is pulsed, a pulse above noise(thermal and emi) occurs where the
laser shutter pulse should-- not where the photodiode shutter pulse should.
Doesn't this mean that the photodiode shutter pulse effect is due to the
opening of the photodiode shutter at the same time as the laser shutter even
though it is closed before light arives at the photodiode?
You point out that the anomalous effect pulse occurs on top of an emi
spike.
But of course so do the pure laser shutter pulse and the pure photodiode
shutter pulse but we dont say that the emi spike is part of the cause of
these light
pulses!"
Ralph
.
Dries van Oosten
> > (1) Just why are your diode signals so pathetically small (trying to
> > do mv measurements in a lab with a pulsed HV generator is a really
> > BAD idea).
>
> Couldn't think of an alternative.
why don't you put the laser and the detection system in another room? I
assume the effect is only dependent on the distance between the pockel
cells and not the distance from the pockels cell to the laser or the
detection system.
>
> I thought you were going to use a lens in your
> > "improved" experiment to get better signal to noise.
> >
> I did get two lenses that worked and the large lens by itself worked
> But didn't think it was necessary so long as there was a clear distinction
> between light and emi on the scope pictures.
> Also I wanted to reduce the number of factors influencing the results.
Good idea. The less optical elements the better. If you see a signal
without lenses, then keep them out. I might be nice however to try to see
what the effect of the lenses is. Maybe there's some information in it.
>
> > (2) Why do your photodiode signals go NEGATIVE ? Your diode should
> > produce positive going signals only. Negative signals = noise or
> > ringing in your system.
>
> Got rid of as much noise as I could. Maybe this is in the cables and
> connections. We dont have to be absolutists at
> this stage. The superluminal effect is clearly above
> noise and for practical applications there is clearly room for improvement.
We do have to be absolutists. If you don't understand why there is a
negative signal, then you don't know what's going on in your experiment,
so something can be happening that you don't know about. If you open the
pockel cell, there is the voltage buildup. If there are strange things
such as negative diode signals, couldn't it be the voltage spike caused by
the triggering of the pockels cell that causes this? Maybe you've already
did this, but isn't it a good idea to block the diode (with a mechanical
chopper) will you are pulsing the pockels cells and then substract the
"chopper closed" signal from the "chopper open" signal. A reversed diode
signal sounds like a voltage spike somewhere.
> Ralph
Groeten,
Dries
Ralph Sansbury
Dries van Oosten <dvoo...@phys.uu.nl> wrote in message
news:Pine.OSF.4.21.00022...@ruunat.phys.uu.nl...
Ralph Sansbury
Dries van Oosten <dvoo...@phys.uu.nl> wrote in message
news:Pine.OSF.4.21.00022...@ruunat.phys.uu.nl...
> On Thu, 24 Feb 2000, Ralph Sansbury wrote:
>
> > > (1) Just why are your diode signals so pathetically small (trying to
> > > do mv measurements in a lab with a pulsed HV generator is a really
> > > BAD idea).
> >
> > Couldn't think of an alternative.
>
> why don't you put the laser and the detection system in another room? I
> assume the effect is only dependent on the distance between the pockel
> cells and not the distance from the pockels cell to the laser or the
> detection system.
>
> >
most light etc given time contraints. But the point is there was a clear
small signal above noise that was repeated millions of times.
> > I thought you were going to use a lens in your
> > > "improved" experiment to get better signal to noise.
> > >
> > I did get two lenses that worked and the large lens by itself
worked
> > But didn't think it was necessary so long as there was a clear
distinction
> > between light and emi on the scope pictures.
> > Also I wanted to reduce the number of factors influencing the results.
>
> Good idea. The less optical elements the better. If you see a signal
> without lenses, then keep them out. I might be nice however to try to see
> what the effect of the lenses is. Maybe there's some information in it.
>
> >
> > > (2) Why do your photodiode signals go NEGATIVE ? Your diode should
> > > produce positive going signals only. Negative signals = noise or
> > > ringing in your system.
> >
> > Got rid of as much noise as I could. Maybe this is in the cables and
> > connections. We dont have to be absolutists at
> > this stage. The superluminal effect is clearly above
> > noise and for practical applications there is clearly room for
improvement.
>
> We do have to be absolutists. If you don't understand why there is a
> negative signal, then you don't know what's going on in your experiment,
> so something can be happening that you don't know about.
The degree to which the signal was negative was typical as you can see in
the scope pictures of
the negative signals or reflectance due to imperfect impedance matching in
the trigger pulses in the same
picture. As I pointed out to Roland, the induction of these effects is basic
electromagnetics and nothing
mysterious.
The point again is that there was a clear small signal above thermal and
such emi noise that
was repeated millions of times.
but isn't it a good idea to block the diode (with a mechanical
> chopper) will you are pulsing the pockels cells and then substract the
> "chopper closed" signal from the "chopper open" signal. A reversed diode
> signal sounds like a voltage spike somewhere.
Yes it would have been a very good idea to try this.
Ralph http://www.bestweb.net/~sansbury
Skywise
>
> Dries van Oosten <dvoo...@phys.uu.nl> wrote in message
> news:Pine.OSF.4.21.00022...@ruunat.phys.uu.nl...
> > On Thu, 24 Feb 2000, Ralph Sansbury wrote:
I see you still haven't learned how to use your newsreader software.
--
S*k*y*w*i*s*e
http://home.earthlink.net/~skywise711/ Laser & Optics links galore!!!