- #1
tim1608
- 63
- 0
Hi Everyone
This is a question which, in various forms has been asked in various places on the Internet but I have never seen a satisfactory answer. I have therefore decided to try and ask it in a unique way which will start off conventionally to begin with.
If I have two side-by-side lasers of identical wavelength and amplitude completely overlapping at a far-away target with a half-wavelength phase difference, thus causing the target to be dark, where does the energy go?
The following are intensity diagrams which show Lasers A and B, initially in phase and not overlapping and then being moved so that they overlap.
These are ASCII diagrams using the Courier (fixed-width) font which hopefully will display correctly on your computer. Please ignore the underscores. I am using them because spaces at the beginning of a line are ignored. The height of the blocks represents intensity.
In phase:
1. No overlap:
AAA BBB
AAA BBB
2. 1/3 overlap:
__B
__B
AAABB
AAABB
3. 2/3 overlap:
_BB
_BB
AAAB
AAAB
4. Total overlap:
BBB
BBB
AAA
AAA
Now 1/2 a wavelength out of phase:
1. No overlap:
AAA BBB
AAA BBB
2. 1/3 overlap:
AA BB
AA BB
AA BB
3. 2/3 overlap:
A B
A B
A B
A B
A B
A B
4. Total overlap:
?
Can anyone complete the sequence? Is it the same as when the lasers are in phase? Is 1 to 3 correct?
Thank you very much.
This is a question which, in various forms has been asked in various places on the Internet but I have never seen a satisfactory answer. I have therefore decided to try and ask it in a unique way which will start off conventionally to begin with.
If I have two side-by-side lasers of identical wavelength and amplitude completely overlapping at a far-away target with a half-wavelength phase difference, thus causing the target to be dark, where does the energy go?
The following are intensity diagrams which show Lasers A and B, initially in phase and not overlapping and then being moved so that they overlap.
These are ASCII diagrams using the Courier (fixed-width) font which hopefully will display correctly on your computer. Please ignore the underscores. I am using them because spaces at the beginning of a line are ignored. The height of the blocks represents intensity.
In phase:
1. No overlap:
AAA BBB
AAA BBB
2. 1/3 overlap:
__B
__B
AAABB
AAABB
3. 2/3 overlap:
_BB
_BB
AAAB
AAAB
4. Total overlap:
BBB
BBB
AAA
AAA
Now 1/2 a wavelength out of phase:
1. No overlap:
AAA BBB
AAA BBB
2. 1/3 overlap:
AA BB
AA BB
AA BB
3. 2/3 overlap:
A B
A B
A B
A B
A B
A B
4. Total overlap:
?
Can anyone complete the sequence? Is it the same as when the lasers are in phase? Is 1 to 3 correct?
Thank you very much.