Duration of wave packet (photon) vs coherent time

AI Thread Summary
Coherence time refers to the duration a light pulse remains coherent, as different frequency components can drift out of phase over time. The duration of a wave packet is defined as the time difference between its leading and trailing edges. Coherence time is not necessarily contained within the wave packet's duration; instead, it is influenced by the pulse's bandwidth. It indicates how accurately future values of the light field can be predicted and is often measured using a Mach-Zehnder interferometer. Generally, coherence time is approximately twice the cavity length in such setups.
coke
Messages
8
Reaction score
0
hi, can anyone kindly explain to me what's 'coherent time' and 'duration of wave packet (photon)' in white light interference ?
 
Science news on Phys.org
Coherence time is length of time a pulse of light will remain coherent for. Light pulses (or wavepackets if you like) become incoherent with time because the different frequency components drift out of phase with one another.

The duration of the wave packet is just the time difference between the leading and trailing edge of the pulse.

Claude.
 
then does it mean that coherent time period is within the duration of a wave packet ?
 
then does it mean that coherent time is within the duration of a wave packet ?
 
No- the coherence time is related to the bandwidth of a pulse, and is only related to the pulse time in diffraction-limited cases.

The coherence time means how well you can predict future values of the field (or intensity), and is typically measured by a Mach-Zender interfeometer.

As a rule of thumb, the coherence time (or equivalently, the maximum path difference in a M-Z interferometer) is given by twice the cavity length.
 
Thread 'A quartet of epi-illumination methods'

Thread 'A quartet of epi-illumination methods'

Well, it took almost 20 years (!!!), but I finally obtained a set of epi-phase microscope objectives (Zeiss). The principles of epi-phase contrast is nearly identical to transillumination phase contrast, but the phase ring is a 1/8 wave retarder rather than a 1/4 wave retarder (because with epi-illumination, the light passes through the ring twice). This method was popular only for a very short period of time before epi-DIC (differential interference contrast) became widely available. So...
View full post »

Thread 'Effective absorption coefficient of gold nanoparticles'

I am currently undertaking a research internship where I am modelling the heating of silicon wafers with a 515 nm femtosecond laser. In order to increase the absorption of the laser into the oxide layer on top of the wafer it was suggested we use gold nanoparticles. I was tasked with modelling the optical properties of a 5nm gold nanoparticle, in particular the absorption cross section, using COMSOL Multiphysics. My model seems to be getting correct values for the absorption coefficient and...
View full post »

Similar threads

Effects of coherence length on optical interference filter
2
Replies
66
Views
5K
Question about wave interference and coherence
Replies
8
Views
2K
I Why do we use low-coherence light in Optical Coherence Tomography?
Replies
1
Views
3K
A The coherence length is much longer than the manufacturer claims
Replies
10
Views
2K
Wave interference - coherence and wavelength
Replies
7
Views
3K
I Shape of wave function (probability distribution) of a single photon
Replies
16
Views
433
Wave / particle duality of light
Replies
4
Views
2K
I Energy of Electromagnetic Waves in Destructive Interference
2
Replies
71
Views
8K
Coherent waves for interference
Replies
3
Views
8K
I 2-Slit: How do we know photon guns only produce single photons?
Replies
33
Views
2K

Hot Threads

Recent Insights

Back
Top