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Size: 5168
Comment:
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Size: 5183
Comment:
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| Deletions are marked like this. | Additions are marked like this. |
| Line 35: | Line 35: |
| ||||||''X End laser fiber setup''|| | ||||||||''X End laser fiber setup''|| |
| Line 40: | Line 40: |
| ||Layout the fiber along 40m arms in insulated tubes||MT+help ||Laid out||Nov 5|| | ||Layout the fiber along 40m arms in insulated tubes||MT+help ||Laid out||Nov 21|| |
| Line 43: | Line 43: |
| ||Setup fibers in the fiber chassis||MT || || ||Couple fiber to fiber||MT|| || ||Combine PSL and end laser with appropriate polarization (50/50 --> 90/10)||MT|| || ||Detecting beatnotes at the PD||MT || || |
||Setup fibers in the fiber chassis||MT || || || ||Couple fiber to fiber||MT|| || || ||Combine PSL and end laser with appropriate polarization (50/50 --> 90/10)||MT|| || || ||Detecting beatnotes at the PD||MT || || || |
| Line 48: | Line 48: |
| ||Hook up frequency counter||MT || || || Check FC acquisition scripts||MT || || || || |
||Hook up frequency counter||MT || || || || Check FC acquisition scripts||MT || || || |
Frequency Offset Locking (FOL) for Dual Wavelength Laser Stabilisation
Overview
In order for the Arm Length Stabilization (ALS) system to be effective in its purpose, the beat frequency between the AUX lasers and the PSL must be within the efficient working range of ALS (< 50 MHz). Thus, our purpose in Frequency Offset Locking (FOL) is to design a feedback-control loop that will keep this beat frequency well within the working range of ALS, so that manual tuning of auxiliary (AUX) laser frequencies may be avoided.
Frequency offset locking works by sampling light from each laser source, PSL and AUX laser, and combining them to produce a beat note which corresponds to the difference between the frequencies of either laser.
The combined PSL and AUX light is sensed at an RF photodiode and an RF frequency counter is used to measure the beat frequency. A digital PID control loop compares the detected beat frequency with the desired beat frequency to produce an error signal. The error signal is then converted back to an analog signal, to actuate on the temperature of the crystal in the AUX laser to keep its frequency within the desired range.
Schematic
A schematic of the setup for FOL is shown below:
Project Tasks
Tasks |
Who |
Status |
Last updated |
General tasks |
|||
Make procurements list and purchase stuff |
MT |
Done |
Oct 9 |
Find out the fiber mode with collimator |
MT |
Waist of output beam = 210um |
Oct 16 |
Y End laser fiber setup |
|||
Waist of beam from doubling crystal |
MT |
Elog 10287 --> Waist = 40.2um |
Oct 9 |
Designate space for the setup at end tables |
MT |
~30cm of propagation distance available |
Oct 13 |
Design telescopes for coupling light into the fiber |
MT |
converging lens f=12cm |
Oct 13 |
Assemble end telescope and couple light into fiber |
MT |
Status - elog 10638 |
Oct 24 |
Layout the fiber along 40m arms in insulated tubes |
MT+help |
Laid out |
Nov 5 |
PSL fiber setup |
|||
Waist of beam from doubling crystal |
MT |
Elog 10287 --> Waist = 43.5um |
Oct 23 |
Designate space on PSL table |
MT |
Lot of space available |
Oct 23 |
Find out the fiber mode with collimator |
MT |
Waist of output beam = 176um |
Oct 23 |
Design telescopes for coupling light into the fiber |
MT |
f_1=75mm@z=10.4cm+f_2=-1m@z=32.3cm with target @z=40cm |
Oct 23 |
Assemble end telescope and couple light into the fiber |
MT |
Temporary telescope in place |
Nov 5 |
X End laser fiber setup |
|||
Waist of beam from doubling crystal |
MT |
|
|
Designate space for the setup at end tables |
MT |
|
|
Design telescopes for coupling light into the fiber |
MT |
|
|
Assemble end telescope and couple light into fiber |
MT |
|
|
Layout the fiber along 40m arms in insulated tubes |
MT+help |
Laid out |
Nov 21 |
Beat note setup |
|||
Make fiber chassis layout |
MT |
Done |
Nov 21 |
Setup fibers in the fiber chassis |
MT |
|
|
Couple fiber to fiber |
MT |
|
|
Combine PSL and end laser with appropriate polarization (50/50 --> 90/10) |
MT |
|
|
Detecting beatnotes at the PD |
MT |
|
|
Frequency counter setup |
|||
Hook up frequency counter |
MT |
|
|
Check FC acquisition scripts |
MT |
|
|
Read beat frequency on StripTool |
MT |
|
|
Mount FC module on IOO rack |
MT+help |
|
|
End laser thermal actuator characterization |
|||
Digital servo |
MISC tasks |
|||
Behavior of PM fiber to temperature fluctuations |
|
|
|
Polarization controller characterization |
|
|
|
Procurements list
Component |
Quantity needed/procured |
Part number |
Order status |
As of |
70m PM fiber |
4/4 |
Corning PM98-U25A |
Procured |
Oct 7 |
6 axis fiber mount |
6/4 |
Thorlabs K6XS |
? |
Oct 7 |
Fiber mounting adapters |
6/4 |
Thorlabs SM1FCA |
Need to rder more |
Oct 7 |
Fiber collimators |
6/3 |
Thorlabs CFC-2X-C |
More ordered |
Oct 13 |
Fiber collimator mounts |
6/2 |
Thorlabs AD9.5F |
More ordered |
Oct 13 |
HR1064 mirrors |
?/plenty |
CVI Y1 mirrors |
Procured |
Oct 7 |
Lenses for telescopes |
?/1064nm lens kit available |
? |
? |
Oct 7 |
Fiber insulating tubes |
2/2 |
- |
Procured |
Oct 7 |
Fiber BS for splitting PSL light between the arms(PM = PM+PM in 50-50) |
1/1 |
Afw Tech POBC-64--C-(s)PM-7-2-25 dB |
Procured |
Oct 7 |
PM fiber mating sleeves PM FC/APC & (FC/APC) |
6,4/0 |
Thorlabs ADAFCPMB2&ADAFCB3 |
Ordered |
Oct 16 |
PM and SM fiber patch cables |
|
Thorlabs |
Ordered |
Oct 16 |
Fiber BC for beat note between arm and PSL (PM+PM=SM) |
2/2 |
Afw tech POBC-64-C-1-7-2-25 dB |
Procured |
Oct 7 |
Polarization controller |
?/1 |
Acrobat PCM4102-333 |
Procured |
Oct 7 |
Fiber BS for splitting combined light between PD and pick off (SM 10-90) |
2/2 |
Afw Tech FOSC-1-64-10-C-(s)3m-H64-2 |
Procured |
Oct 7 |
Fiber coupled PD |
2/2 |
Thorlabs FPD310 |
Procured |
Dec 3 |
Frequency counter |
2/2 |
Minicircuits UFC6000 |
Procured |
Oct 7 |
Fiber chassis |
1/1 |
Front Panel Express |
Ordered |
Nov 26 |