A polarizer only allows light of certain polarity (the "direction" the waveform oscillates, think sunglasses or 3D glasses, or the polariser in your LCD screen) to pass through.
But it doesn't have to be polarization just any easy modulation of the light, polarization is just easy to do since all you need is a huge polarizer and a few reaction wheels.
Think about planetary transitions; we can detect those quite easily this is how we find exoplanets these days, in fact we can fairly accurately identify the composition of the planet's atmosphere and the atmosphere is a fairly thin slice of the entire planet's silhouette.
So the only thing you need to do is to position a sufficiently big object it doesn't have to be even that big (still huge in our scale but something in the range of 100's or even 1000's of kilometers across would likely be sufficient the radius of the earth is only 6300KM~ and we can detect planets smaller than the earth AFAIK, and it can be as thin as a solar sail and considering we already build satellites with antenna that unfold to the size of a few football fields it might be possible even with our current level of technology or something not that far off) because you take advantage of the distance between planetary systems that object needs to be able to modulate the light it can be polarization, abstraction, color filtering.
To put it simply make a huge ass thin TFT LCD let the sun act as a backlight and put it in a stelar synchronous orbit from the vantage point of the star system you want to communicate with so it would always appear in line between it and your local star and blink your messages away.
If you want to go for the golden star then build a huge ring which also is capable of acting like lense this can allow you to have a communication array which can also direct the signal in a relative narrow beam.
https://en.wikipedia.org/wiki/Polarization_(waves)
But it doesn't have to be polarization just any easy modulation of the light, polarization is just easy to do since all you need is a huge polarizer and a few reaction wheels.
Think about planetary transitions; we can detect those quite easily this is how we find exoplanets these days, in fact we can fairly accurately identify the composition of the planet's atmosphere and the atmosphere is a fairly thin slice of the entire planet's silhouette.
So the only thing you need to do is to position a sufficiently big object it doesn't have to be even that big (still huge in our scale but something in the range of 100's or even 1000's of kilometers across would likely be sufficient the radius of the earth is only 6300KM~ and we can detect planets smaller than the earth AFAIK, and it can be as thin as a solar sail and considering we already build satellites with antenna that unfold to the size of a few football fields it might be possible even with our current level of technology or something not that far off) because you take advantage of the distance between planetary systems that object needs to be able to modulate the light it can be polarization, abstraction, color filtering.
To put it simply make a huge ass thin TFT LCD let the sun act as a backlight and put it in a stelar synchronous orbit from the vantage point of the star system you want to communicate with so it would always appear in line between it and your local star and blink your messages away.
If you want to go for the golden star then build a huge ring which also is capable of acting like lense this can allow you to have a communication array which can also direct the signal in a relative narrow beam.