Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
I don't know of any particular reason why a DVD-player laser should be faster, since neither CD nor DVD players need to deliberately modulate the lasers anyway. At least, that's the first blush answer. However, these diode lasers are generally noisy, apparently due to the inevitable presence of optical reflections back into the diodes. I once read that deliberately FM'ing the laser by applying a high frequency RF tone along with the DC bias current could be helpful in mitigating the problem. But this was in connection with the *analog* Laser Disk video recording format. I don't know if the laser noise was ever much of a problem with reading the digital formats of CDs and DVDs. If not, then surely the makers of diodes for these mass market applications would not be investing effort in making the lasers fast. On additional factor is that CD players and DVD players use different light wavelengths: ~780 nm for CDs, ~650 nm for DVDs. It might be that the difference in semiconductor composition between the two types makes a significant difference in the response speed. However, I doubt that this would would be relevant for present purposes, unless Rb also has some *useful* transitions in the 650 nm regime. Dana On Thu, Jun 14, 2018 at 11:25 PM, Hal Murray wrote: > > k8yumdoo...@gmail.com said: > > 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. > > Are DVD lasers faster? > > > -- > These are my opinions. I hate spam. > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
k8yumdoo...@gmail.com said: > 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. Are DVD lasers faster? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
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 On Thu, Jun 14, 2018 at 10:51 AM, Attila Kinali wrote: > On Mon, 11 Jun 2018 22:29:42 +0800 > mimitech mimitech wrote: > > > 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. > > > 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 > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
On Mon, 11 Jun 2018 22:29:42 +0800 mimitech mimitech wrote: > 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. > 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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
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! On Mon, 11 Jun 2018 10:57:50 +0200, Attila Kinali wrote: > > On Sat, 9 Jun 2018 16:54:15 +0800 > mimitech mimitech wrote: > > > 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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
On Sat, 9 Jun 2018 16:54:15 +0800 mimitech mimitech wrote: > 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 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
It’s an older Efratom rubidium frequency reference. Steve > On Jun 9, 2018, at 8:34 AM, Dana Whitlow wrote: > > What is an 'FRK'? > > Thanks, > > Dana > > >> On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts wrote: >> >> 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, >> bruce.griffi...@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 >>> On 09 June 2018 at 20:54 mimitech mimitech wrote: >>> >>> >>> 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--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 Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali >> wrote: On Mon, 4 Jun 2018 21:31:56 +0800 mimitech mimitech wrote: > 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,
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
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 ( and possibly others) cloned the package in an attempt to compete with Efratom. You see very few EG’s and a *lot* of Efratom’s …. Bob > On Jun 9, 2018, at 9:34 AM, Dana Whitlow wrote: > > What is an 'FRK'? > > Thanks, > > Dana > > > On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts wrote: > >> 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, >> bruce.griffi...@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 >>> On 09 June 2018 at 20:54 mimitech mimitech wrote: >>> >>> >>> 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--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 Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali >> wrote: On Mon, 4 Jun 2018 21:31:56 +0800 mimitech mimitech wrote: > 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€
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
What is an 'FRK'? Thanks, Dana On Sat, Jun 9, 2018 at 7:51 AM, ew via time-nuts wrote: > 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, > bruce.griffi...@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 > > On 09 June 2018 at 20:54 mimitech mimitech wrote: > > > > > > 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--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 Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali > wrote: > > > > > > On Mon, 4 Jun 2018 21:31:56 +0800 > > > mimitech mimitech wrote: > > > > > > > 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
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
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, bruce.griffi...@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 > On 09 June 2018 at 20:54 mimitech mimitech wrote: > > > 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--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 Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali wrote: > > > > On Mon, 4 Jun 2018 21:31:56 +0800 > > mimitech mimitech wrote: > > > > > 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 >
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
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 > On 09 June 2018 at 20:54 mimitech mimitech wrote: > > > 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--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 Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali wrote: > > > > On Mon, 4 Jun 2018 21:31:56 +0800 > > mimitech mimitech wrote: > > > > > 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-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] a newbie question: where can I purchase 794.7nm VCSEL for building CPT rubidium clock?
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--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 Tue, 5 Jun 2018 11:11:59 +0200, Attila Kinali wrote: > > On Mon, 4 Jun 2018 21:31:56 +0800 > mimitech mimitech wrote: > > > 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-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
