Discussion:
a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
(too old to reply)
mimitech mimitech
2018-06-09 08:54:15 UTC
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Raw Message
Thanks Attila for your suggestion.

I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.

I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
mode VCSEL from a local distributor, price is about $500/pcs. I'm not sure
whether this model could work in CPT rubidium clock.

A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
VCSEL, with unit price $800, which was proved to work as this paper
"A compact atomic magnetometer for cubesats",
https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_0017N_11402.pdf
,

this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
Trapping (CPT) in Rubidium"
http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_Thesis_with_papers_V7.pdf

and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
series. The cheapest model is SA.31m priced about $1100 at Digikey /
Mouser.

Another paper "VCSEL Laser System for Atomic Clocks"
http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
several VCSEL from different vendors and found the ULM 794.7 nm single mode
VCSEL can work.

Thanks.

mimitech.
On Mon, 4 Jun 2018 21:31:56 +0800
I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
as my next hobby project. The main purpose is to learn the principles
behind CPT rubidium clock, and hopefully got similar or better
performance
than commercial miniature rubidium clock such as FE-5680A.
Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become
interesting,
if you use a naive approach.
Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You will
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical PLL).
If you have enough money to spend, I'd go for two Cateye diode laser CEL's
from Moglabs (cost AFAIK 5000€ each)
No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.
As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Bruce Griffiths
2018-06-09 11:23:12 UTC
Permalink
Raw Message
Theres also

http://www.photonics.philips.com/application-areas/sensing/components

and

https://www.sacher-laser.com/home/industriallasers/point_and_line_laser_module/industrial_laser_modules/micron_laser.html
Bruce
Post by mimitech mimitech
Thanks Attila for your suggestion.
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
mode VCSEL from a local distributor, price is about $500/pcs. I'm not sure
whether this model could work in CPT rubidium clock.
A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
VCSEL, with unit price $800, which was proved to work as this paper
"A compact atomic magnetometer for cubesats",
https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_0017N_11402.pdf
,
this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
Trapping (CPT) in Rubidium"
http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_Thesis_with_papers_V7.pdf
and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
series. The cheapest model is SA.31m priced about $1100 at Digikey /
Mouser.
Another paper "VCSEL Laser System for Atomic Clocks"
http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
several VCSEL from different vendors and found the ULM 794.7 nm single mode
VCSEL can work.
Thanks.
mimitech.
On Mon, 4 Jun 2018 21:31:56 +0800
I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
as my next hobby project. The main purpose is to learn the principles
behind CPT rubidium clock, and hopefully got similar or better
performance
than commercial miniature rubidium clock such as FE-5680A.
Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become
interesting,
if you use a naive approach.
Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You will
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical PLL).
If you have enough money to spend, I'd go for two Cateye diode laser CEL's
from Moglabs (cost AFAIK 5000€ each)
No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.
As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
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ew via time-nuts
2018-06-09 12:51:19 UTC
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Having followed the conversation and having looked at the p[possibility using a FRK with laser diode, it is low on our list because of all the ongoing projects but please if you want to spend time and money use any thing but a FE5680. I was one of the first using it and noticed and posted a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the attached. Do not have info as to who posted it.
Using a FRK is the easiest way to do so if interested contact me off list, based on our tests is a close second to the HP 5065A.
Bert Kehren 
 
In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time, ***@xtra.co.nz writes:

 
Theres also

http://www.photonics.philips.com/application-areas/sensing/components

and

https://www.sacher-laser.com/home/industriallasers/point_and_line_laser_module/industrial_laser_modules/micron_laser.html
Bruce
Post by mimitech mimitech
Thanks Attila for your suggestion.
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
mode VCSEL from a local distributor, price is about $500/pcs. I'm not sure
whether this model could work in CPT rubidium clock.
A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
VCSEL, with unit price $800, which was proved to work as this paper
"A compact atomic magnetometer for cubesats",
https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_0017N_11402.pdf
,
this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
Trapping (CPT) in Rubidium"
http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_Thesis_with_papers_V7.pdf
and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
series. The cheapest model is SA.31m priced about $1100 at Digikey /
Mouser.
Another paper "VCSEL Laser System for Atomic Clocks"
http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
several VCSEL from different vendors and found the ULM 794.7 nm single mode
VCSEL can work.
Thanks.
mimitech.
On Mon, 4 Jun 2018 21:31:56 +0800
I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
as my next hobby project. The main purpose is to learn the principles
behind CPT rubidium clock, and hopefully got similar or better
performance
than commercial miniature rubidium clock such as FE-5680A.
Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become
interesting,
if you use a naive approach.
Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You will
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical PLL).
If you have enough money to spend, I'd go for two Cateye diode laser CEL's
from Moglabs (cost AFAIK 5000€ each)
No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.
As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Dana Whitlow
2018-06-09 13:34:54 UTC
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Raw Message
What is an 'FRK'?

Thanks,

Dana
Post by ew via time-nuts
Having followed the conversation and having looked at the p[possibility
using a FRK with laser diode, it is low on our list because of all the
ongoing projects but please if you want to spend time and money use any
thing but a FE5680. I was one of the first using it and noticed and posted
a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the
attached. Do not have info as to who posted it.
Using a FRK is the easiest way to do so if interested contact me off list,
based on our tests is a close second to the HP 5065A.
Bert Kehren
In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time,
Theres also
http://www.photonics.philips.com/application-areas/sensing/components
and
https://www.sacher-laser.com/home/industriallasers/point_
and_line_laser_module/industrial_laser_modules/micron_laser.html
Bruce
Post by mimitech mimitech
Thanks Attila for your suggestion.
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
mode VCSEL from a local distributor, price is about $500/pcs. I'm not
sure
Post by mimitech mimitech
whether this model could work in CPT rubidium clock.
A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
VCSEL, with unit price $800, which was proved to work as this paper
"A compact atomic magnetometer for cubesats",
https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_
0017N_11402.pdf
Post by mimitech mimitech
,
this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
Trapping (CPT) in Rubidium"
http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_
Thesis_with_papers_V7.pdf
Post by mimitech mimitech
and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
series. The cheapest model is SA.31m priced about $1100 at Digikey /
Mouser.
Another paper "VCSEL Laser System for Atomic Clocks"
http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
several VCSEL from different vendors and found the ULM 794.7 nm single
mode
Post by mimitech mimitech
VCSEL can work.
Thanks.
mimitech.
On Mon, 4 Jun 2018 21:31:56 +0800
I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
as my next hobby project. The main purpose is to learn the principles
behind CPT rubidium clock, and hopefully got similar or better
performance
than commercial miniature rubidium clock such as FE-5680A.
Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become
interesting,
if you use a naive approach.
Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You
will
Post by mimitech mimitech
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical
PLL).
Post by mimitech mimitech
If you have enough money to spend, I'd go for two Cateye diode laser
CEL's
Post by mimitech mimitech
from Moglabs (cost AFAIK 5000€ each)
No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.
As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
Post by mimitech mimitech
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-***@febo.com
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and follow the instructions there.
Bob kb8tq
2018-06-09 14:12:03 UTC
Permalink
Raw Message
Hi

For several decades the Efratom FRK was the only “compact” Rb on the market. By today’s standards it’s a bit
large, but in that era it was quite small. They went through a couple of re-designs over the years, but kept the
basic form factor and nomenclature. The M-100 is the military version. EG&G ( and possibly others) cloned the
package in an attempt to compete with Efratom. You see very few EG&G’s and a *lot* of Efratom’s ….

Bob
Post by Dana Whitlow
What is an 'FRK'?
Thanks,
Dana
Post by ew via time-nuts
Having followed the conversation and having looked at the p[possibility
using a FRK with laser diode, it is low on our list because of all the
ongoing projects but please if you want to spend time and money use any
thing but a FE5680. I was one of the first using it and noticed and posted
a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the
attached. Do not have info as to who posted it.
Using a FRK is the easiest way to do so if interested contact me off list,
based on our tests is a close second to the HP 5065A.
Bert Kehren
In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time,
Theres also
http://www.photonics.philips.com/application-areas/sensing/components
and
https://www.sacher-laser.com/home/industriallasers/point_
and_line_laser_module/industrial_laser_modules/micron_laser.html
Bruce
Post by mimitech mimitech
Thanks Attila for your suggestion.
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
mode VCSEL from a local distributor, price is about $500/pcs. I'm not
sure
Post by mimitech mimitech
whether this model could work in CPT rubidium clock.
A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
VCSEL, with unit price $800, which was proved to work as this paper
"A compact atomic magnetometer for cubesats",
https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_
0017N_11402.pdf
Post by mimitech mimitech
,
this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
Trapping (CPT) in Rubidium"
http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_
Thesis_with_papers_V7.pdf
Post by mimitech mimitech
and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
series. The cheapest model is SA.31m priced about $1100 at Digikey /
Mouser.
Another paper "VCSEL Laser System for Atomic Clocks"
http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
several VCSEL from different vendors and found the ULM 794.7 nm single
mode
Post by mimitech mimitech
VCSEL can work.
Thanks.
mimitech.
On Mon, 4 Jun 2018 21:31:56 +0800
I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
as my next hobby project. The main purpose is to learn the principles
behind CPT rubidium clock, and hopefully got similar or better
performance
than commercial miniature rubidium clock such as FE-5680A.
Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become
interesting,
if you use a naive approach.
Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You
will
Post by mimitech mimitech
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical
PLL).
Post by mimitech mimitech
If you have enough money to spend, I'd go for two Cateye diode laser
CEL's
Post by mimitech mimitech
from Moglabs (cost AFAIK 5000€ each)
No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.
As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
Post by mimitech mimitech
and follow the instructions there.
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
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mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
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Steve - Home
2018-06-09 14:29:15 UTC
Permalink
Raw Message
It’s an older Efratom rubidium frequency reference.

Steve
Post by Dana Whitlow
What is an 'FRK'?
Thanks,
Dana
Post by ew via time-nuts
Having followed the conversation and having looked at the p[possibility
using a FRK with laser diode, it is low on our list because of all the
ongoing projects but please if you want to spend time and money use any
thing but a FE5680. I was one of the first using it and noticed and posted
a 4 Hz constant deviation using my Tracor 527 E subsequent confirmed by the
attached. Do not have info as to who posted it.
Using a FRK is the easiest way to do so if interested contact me off list,
based on our tests is a close second to the HP 5065A.
Bert Kehren
In a message dated 6/9/2018 7:23:45 AM Eastern Standard Time,
Theres also
http://www.photonics.philips.com/application-areas/sensing/components
and
https://www.sacher-laser.com/home/industriallasers/point_
and_line_laser_module/industrial_laser_modules/micron_laser.html
Bruce
Post by mimitech mimitech
Thanks Attila for your suggestion.
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
I have purchased small amount of Vixar P/N “795S-0000-BC01” 795nm single
mode VCSEL from a local distributor, price is about $500/pcs. I'm not
sure
Post by mimitech mimitech
whether this model could work in CPT rubidium clock.
A more suitable model maybe Oclaro P/N “APM2101013300” 795nm single mode
VCSEL, with unit price $800, which was proved to work as this paper
"A compact atomic magnetometer for cubesats",
https://open.bu.edu/bitstream/handle/2144/16303/Knechtel_bu_
0017N_11402.pdf
Post by mimitech mimitech
,
this thesis "Ultra-Low Phase Noise Atomic Clock using Coherent Population
Trapping (CPT) in Rubidium"
http://etheses.whiterose.ac.uk/20073/1/Burtichelov_PhD_
Thesis_with_papers_V7.pdf
Post by mimitech mimitech
and also it was used in commercial CPT rubidium clock - Microsemi SA.3xm
series. The cheapest model is SA.31m priced about $1100 at Digikey /
Mouser.
Another paper "VCSEL Laser System for Atomic Clocks"
http://ixnovi.people.wm.edu/documents/NathanBelcherREUPaper.pdf test
several VCSEL from different vendors and found the ULM 794.7 nm single
mode
Post by mimitech mimitech
VCSEL can work.
Thanks.
mimitech.
On Mon, 4 Jun 2018 21:31:56 +0800
I'm planning to build a CPT (coherent-population-trapping) rubidium
clock
as my next hobby project. The main purpose is to learn the principles
behind CPT rubidium clock, and hopefully got similar or better
performance
than commercial miniature rubidium clock such as FE-5680A.
Building a CPT clock is slightly more involved than you might think
at first. The laser diode is only one part of it. You will most likely
be able to improve on the short-term stability of the FE-5680 (which
is rather poor). But I doubt you will be able to improve much on
the long term stability, which is where things actually become
interesting,
if you use a naive approach.
Nevertheless, I have not seen many 794/795nm diodes around. The only
one that I have the datasheet of is the one from Vixar.
You might want want to consider going for the D2 line instead of the
D1 line, as 780nm diodes are more commonly available than 795nm. You
will
Post by mimitech mimitech
also need to buy several of those and select the ones that come closest
to the wavelength at the desired opearating conditions (usuall spread
is +/-1nm to +/-10nm). Do not assume you can tune more than 0.1nm with
temperature and current (rule of thumb is that you get about 10GHz
per °C and mA). If you need more tuning range, you will need to add an
external cavity (can give you up to 5nm range), which then needs to be
tuned to the 3.45GHz (ie it's length needs to be approximately 8-9cm).
Alternatively, you can get two S1-0780-XXX from Sacher Laser
(cost IIRC 2500€ each) and keep them 6.9GHz apart (using an optical
PLL).
Post by mimitech mimitech
If you have enough money to spend, I'd go for two Cateye diode laser
CEL's
Post by mimitech mimitech
from Moglabs (cost AFAIK 5000€ each)
No matter what you choose, you will need some wavelength stabilization
scheme. You can either do that with the vapor cell itself or use
an additional cell and do a DVALL or a saturated absorption locking.
Note that this addtional cell will need to be without buffer gas.
An external cell will offer better stability and thus lower noise,
which directly translates into higher stability.
As polarisation scheme, I suggest using σ+/σ- as it seems to be more
robust than the lin/lin schemes.
Attila Kinali
--
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the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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Post by mimitech mimitech
and follow the instructions there.
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Attila Kinali
2018-06-11 08:57:50 UTC
Permalink
Raw Message
On Sat, 9 Jun 2018 16:54:15 +0800
Post by mimitech mimitech
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
Why are you focusing on VCSEL anyways? Standard laser diodes already
have a modulation bandwidth that goes into several 100MHz, the better
ones should give you 1-2GHz. With that, you should be within 6dB,
maybe 10dB of the CW power. Given that you only need a few 10µW to 100µW
of laser power, and that those diodes are in the 1-30mW range should
give you enough margin.


Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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mimitech mimitech
2018-06-11 14:29:42 UTC
Permalink
Raw Message
Hi Attila,

I think your information is very interesting. I didn't realize which type
of common LDs can do GHz level modulation (anyway I didn’t have much
knowledge on laser diode before). It would be great If you could recommend
several good Laser diodes (which vendor/part number) with possible 1-2GHz
modulation bandwidth. Thanks!
Post by Attila Kinali
On Sat, 9 Jun 2018 16:54:15 +0800
Post by mimitech mimitech
I prefer the 780/795nm VCSEL scheme for its simplicity. After some
searching, looks like the 780nm VCSELs are also not easy to source,
although other types of 780nm LD are common.
Why are you focusing on VCSEL anyways? Standard laser diodes already
have a modulation bandwidth that goes into several 100MHz, the better
ones should give you 1-2GHz. With that, you should be within 6dB,
maybe 10dB of the CW power. Given that you only need a few 10μW to 100μW
of laser power, and that those diodes are in the 1-30mW range should
give you enough margin.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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Attila Kinali
2018-06-14 15:51:54 UTC
Permalink
Raw Message
On Mon, 11 Jun 2018 22:29:42 +0800
Post by mimitech mimitech
I think your information is very interesting. I didn't realize which type
of common LDs can do GHz level modulation (anyway I didn’t have much
knowledge on laser diode before).
Hehe. Same here. When I looked into CPT I thought that one needs
a fast laser diode as well. Then, a few years ago, I had the chance
to talk to John Kitching who corrected a few of my assumptions.
Post by mimitech mimitech
It would be great If you could recommend
several good Laser diodes (which vendor/part number) with possible 1-2GHz
modulation bandwidth. Thanks!
Sorry, unfortunately I do not have any reliable data on the bandwidth
of standard laser diodes. The easiest would be probably if you select
some diodes that you can easily acquire, then contact the manufacturer.
Manufacturers almost always have more data on their devices than they
put into the datasheet. They do not include it because they can either
not sufficiently control those parameters during production, cannot
test for it or testing would be too expensive.

Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
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Dana Whitlow
2018-06-15 02:49:53 UTC
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Raw Message
I've been told that CD player type diodes can be successfully modulated
up to about 600 MHz, but that going much further is either difficult or
perhaps impossible. This came from a guy (at Tektronix) who worked with
various types
of diode lasers a lot, back in the 1980's. But at least they are cheap. I
suspect that the leaded
package is a significant part of the issue; this ought to be somewhat
mitigated
by a suitable RF matching network.

Dana
Post by Attila Kinali
On Mon, 11 Jun 2018 22:29:42 +0800
Post by mimitech mimitech
I think your information is very interesting. I didn't realize which type
of common LDs can do GHz level modulation (anyway I didn’t have much
knowledge on laser diode before).
Hehe. Same here. When I looked into CPT I thought that one needs
a fast laser diode as well. Then, a few years ago, I had the chance
to talk to John Kitching who corrected a few of my assumptions.
Post by mimitech mimitech
It would be great If you could recommend
several good Laser diodes (which vendor/part number) with possible 1-2GHz
modulation bandwidth. Thanks!
Sorry, unfortunately I do not have any reliable data on the bandwidth
of standard laser diodes. The easiest would be probably if you select
some diodes that you can easily acquire, then contact the manufacturer.
Manufacturers almost always have more data on their devices than they
put into the datasheet. They do not include it because they can either
not sufficiently control those parameters during production, cannot
test for it or testing would be too expensive.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
_______________________________________________
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
and follow the instructions there.
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