Wavefront metrology (class 3 of 3)

7 Maio 2025, 17:00 • Bachar Wehbe

A Shack-Hartmann wavefront sensor was built based on an array of lenses that divide / sample the incoming wavefront into small sub-apertures, focusing independently the light from each lens in a 2D sensor that captures the focal plane pattern. This pattern was processed to obtain the position of each focus point from each individual lens.

An incident plane wave was created using a spatial filter and a collimated lens to produce a grid of equidistant focal points, the reference position, while several distorted waves (corresponding to a point source from an optical fibre in controlled positions) result in an uneven distribution of points that were referenced to the ideal plan wave situation in order to determine with the sensor the position of the fibre tip, using the Shack-Hartman sensor to measure an unknown wavefront based of the focus shifts from the calibration. 

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Wavefront metrology (class 3 of 3)

7 Maio 2025, 15:00 • Alexandre Pereira Cabral

A Shack-Hartmann wavefront sensor was built based on an array of lenses that divide / sample the incoming wavefront into small sub-apertures, focusing independently the light from each lens in a 2D sensor that captures the focal plane pattern. This pattern was processed to obtain the position of each focus point from each individual lens.

An incident plane wave was created using a spatial filter and a collimated lens to produce a grid of equidistant focal points, the reference position, while several distorted waves (corresponding to a point source from an optical fibre in controlled positions) result in an uneven distribution of points that were referenced to the ideal plan wave situation in order to determine with the sensor the position of the fibre tip, using the Shack-Hartman sensor to measure an unknown wavefront based of the focus shifts from the calibration.

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LIGO noise and optical and beam architecture

5 Maio 2025, 14:00 • José Manuel Rebordão

Noise factor in GWO. Intrinsic and technical noises. Analysis of the intrinsic factors. Evolution of overall noise curves since initial LIGO (2010) to current implementations or being under development.
Thermal noise: comparative analysis between thermal properties of silicon, fused silica and sapphire; exquisite properties of Si, therefore justifying its selection for LIGO Voyager, despite the need to change the laser and reducing temperature to 123 K.
 
Principle of measurement. Optical Gain. Impact of using resonant arms to gain sensitivity. Active FP cavities driven by intracavity power concept
Architectures of GWO: comparative analysis of optical layouts; beam architecture and its relation to the different resonant cavities.
 
NEXT CLASS
Reviewing: FP cavities, gaussian waves. Mode-matching.
Analysis of layered systems

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VOID

2 Maio 2025, 09:00 • José Manuel Rebordão

Troca de sala pelo professor… não foi realizada aula!

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Wavefront metrology (class 2 of 3)

30 Abril 2025, 17:00 • Bachar Wehbe

A Shack-Hartmann wavefront sensor was built based on an array of lenses that divide / sample the incoming wavefront into small sub-apertures, focusing independently the light from each lens in a 2D sensor that captures the focal plane pattern. This pattern was processed to obtain the position of each focus point from each individual lens.

An incident plane wave was created using a spatial filter and a collimated lens to produce a grid of equidistant focal points, the reference position, while several distorted waves (corresponding to a point source from an optical fibre in controlled positions) result in an uneven distribution of points that were referenced to the ideal plan wave situation in order to determine with the sensor the position of the fibre tip, using the Shack-Hartman sensor to measure an unknown wavefront based of the focus shifts from the calibration. 

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