homodyne detection: understanding the laser noise amplitude transfer function
DESCRIPTION
Homodyne detection: understanding the laser noise amplitude transfer function. J érô me Degallaix Ilias meeting – June 2007. Going DC. Stefan’s talk this morning. Laser. PRM. SRM. Carrier local oscillator. Measure the laser intensity noise transfer function. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/1.jpg)
Homodyne detection:understanding the laser noise amplitude transfer function
Jérôme Degallaix
Ilias meeting – June 2007
![Page 2: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/2.jpg)
Going DC
Laser
Carrier local oscillator
PRM
SRM
Stefan’s talk this morning
![Page 3: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/3.jpg)
Measure the laser intensity noise transfer
function• Switch off laser power stabilisation loop• Inject white noise into the laser pump• Record dark port spectrum
101
102
103
10-6
10-5
10-4
10-3
10-2
10-1 Amplitude Spectum comparison MID_VIS 2007-06-12
Frequency (Hz)
[V/s
qrt(
Hz)
]
Reference 10:50:00 13:00:30
![Page 4: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/4.jpg)
Laser
output
After laser After MC
Reflected PRC
Reflected BS
Input ?
![Page 5: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/5.jpg)
The measured TF
![Page 6: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/6.jpg)
Laser
FSR = 125 kHz
Optical fields
![Page 7: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/7.jpg)
Laser
FSR = 125 kHzfMI = 14.9 MHz
Optical fields
![Page 8: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/8.jpg)
Laser
FSR = 125 kHzfMI = 14.9 MHzfSR = 9.01 MHz
Optical fields
![Page 9: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/9.jpg)
Carrier TF
Simple Michelson
Flat response due:• Arm asymetries• Dark fringe offset
![Page 10: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/10.jpg)
Carrier TF
With SRM
Peak due to SRM
![Page 11: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/11.jpg)
Carrier TF
Including the higher order optical modes
• Increase the amplitude of the TF• Flat the response at high frequency
![Page 12: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/12.jpg)
TF with SR sidebands
Resonance peak of the sidebands!
![Page 13: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/13.jpg)
TF with SR sidebands
![Page 14: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/14.jpg)
TF with SR sidebands
Including the higher order optical modes
Shape of the sidebandsresonance different!
![Page 15: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/15.jpg)
TF with MI sidebands
![Page 16: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/16.jpg)
TF with MI sidebands
Including the higher order optical modes
![Page 17: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/17.jpg)
Changing the PRC FSR
A little test to confirm what we understand...
![Page 18: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/18.jpg)
Changing the SRC FSR
Another test...
![Page 19: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/19.jpg)
Does it match the experiment ?
• Adjust the overall gain of the simulated TF• Thanks to Andreas for the tuning of the parameters
![Page 20: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/20.jpg)
To sum up...
Due to the signal recycling mirror
Due to SR sidebands and
higher order optical modes
Due to MI sidebands
Due to second order optical
modes
Overal magnitude depends of:• arm detuning • magnitude of higher order optical modes
![Page 21: Homodyne detection: understanding the laser noise amplitude transfer function](https://reader035.vdocument.in/reader035/viewer/2022062221/5681350b550346895d9c5e84/html5/thumbnails/21.jpg)
So ?