I am getting poor polarization measurements from a fiber laser made from PM maintaining fiber. Firstly I would like to ask if my measurement method is ok.
I collimate the beam with an aspherical lens of 8mm focal distance. Then there is a Glan Tayler Polarizer.
https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=815
I tune the angle for maximum and minimum transmission, noting the power. I am only getting a 20:1 ratio between minimum and maximum transmission.
I am concerned that my minimum measurement is my big source of error..Any change in this makes a large change in ratio. I am using a low and high power powermeter for each of the measurements for best accuracy.
Is there another way of doing this measurement?
Thanks
Alex
I do not know what is the best way of doing this measurement, but I do
know how to test your method: measure the polarization of light directly
out of the laser (attenuated if necessary).
Am 13.01.2019 um 23:06 schrieb JTS:
I do not know what is the best way of doing this measurement, but I do
know how to test your method: measure the polarization of light directly out of the laser (attenuated if necessary).
Here I mean: of *a* laser whose polarization you are sure about.
I am getting poor polarization measurements from a fiber laser made from PM maintaining fiber. Firstly I would like to ask if my measurement method is ok.
I collimate the beam with an aspherical lens of 8mm focal distance. Then there is a Glan Tayler Polarizer.
https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=815
I tune the angle for maximum and minimum transmission, noting the power. I am only getting a 20:1 ratio between minimum and maximum transmission.
I am concerned that my minimum measurement is my big source of error..Any change in this makes a large change in ratio. I am using a low and high power powermeter for each of the measurements for best accuracy.
Is there another way of doing this measurement?
On Sunday, January 13, 2019 at 11:07:52 PM UTC+1, JTS wrote:
Am 13.01.2019 um 23:06 schrieb JTS:
I do not know what is the best way of doing this measurement, but I do
know how to test your method: measure the polarization of light directly >>> out of the laser (attenuated if necessary).
Here I mean: of *a* laser whose polarization you are sure about.
Thanks for the idea... I will give that a go tmrw, but I think it might be harder tha it should be to find a laser whose polarisation we know... I'll let you know...
Thanks
Alex
Am 13.01.2019 um 23:22 schrieb alex:
On Sunday, January 13, 2019 at 11:07:52 PM UTC+1, JTS wrote:
Am 13.01.2019 um 23:06 schrieb JTS:
I do not know what is the best way of doing this measurement, but I do >>>> know how to test your method: measure the polarization of light
directly
out of the laser (attenuated if necessary).
Here I mean: of *a* laser whose polarization you are sure about.
Thanks for the idea... I will give that a go tmrw, but I think it
might be harder tha it should be to find a laser whose polarisation we
know... I'll let you know...
Thanks
Alex
I think Phil Hobbs' suggestions are more precise than mine, but another approach is - polarize the light with a polarizer (a polarizer with
1:100 ratio is good enough for this) and repeat your measurements. If
you can measure 1:100, it means the 1:20 you measured is ok.
Yup. A Glan-Taylor is good for 1:10,000 if you use it right. Almost as good as a Wollaston, at least in the transmitted beam. A "beam
splitting Thompson" improves the refracted beam a fair amount, but
they're not that common. Stick with the transmitted one.
On Tuesday, January 15, 2019 at 5:33:51 AM UTC+1, Phil Hobbs wrote:
Yup. A Glan-Taylor is good for 1:10,000 if you use it right. Almost as
good as a Wollaston, at least in the transmitted beam. A "beam
splitting Thompson" improves the refracted beam a fair amount, but
they're not that common. Stick with the transmitted one.
I became curious and I read a bit on Wikipedia. The reflected (I think you mean reflected, right?) beam is only partially polarized in these kind of polarizers because they work by total internal reflection of one polarization (which is then completelyabsent in the transmitted beam) but the other polarization is also reflected a bit (so it is present in the reflected beam).
I have also read about the difference between Glan-Thompson (is this the one you called "beam splitting Thompson"?) and Glan-Taylor, but to figure it out I would have to spend some time with calculations, so I stop here for the moment.
I am getting poor polarization measurements from a fiber laser made from PM maintaining fiber. Firstly I would like to ask if my measurement method is ok.
I collimate the beam with an aspherical lens of 8mm focal distance. Then there is a Glan Tayler Polarizer.
https://www.thorlabs.de/newgrouppage9.cfm?objectgroup_id=815
I tune the angle for maximum and minimum transmission, noting the power. I am only getting a 20:1 ratio between minimum and maximum transmission.
I am concerned that my minimum measurement is my big source of error..Any change in this makes a large change in ratio. I am using a low and high power powermeter for each of the measurements for best accuracy.
Is there another way of doing this measurement?
Thanks
Alex
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