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Mubeen
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- ultra short pulse
what will happen if two one femtosecond(1 fs) laser pulse interferes?
This is a very complicated question, actually. There's a lot going on with the "internal" coherence of the pulse itself, and unless you know the mutual coherence between the pulses, it's impossible to analyze.Mubeen said:TL;DR Summary: ultra short pulse
what will happen if two one femtosecond(1 fs) laser pulse interferes?
A simple case of 'not too short' pulses will only produce a pattern when the arrivals are near coincident and the depth of the fringes will depend on the relative amplitudes of the pulses over time. On boresight and coincident timing, the fringes should be deep but for other angles, the relative amplitudes will be different over time (because of the pulse delay in addition to the simple carrier phase effect). This is the same sort of effect that you get with Young's slits where the sources are finite widths and not omnidirectional and the fringes get weaker off axis.Mubeen said:iam curious to know whether the fringes will have good contrast?.
This seems to be approximately one cycle of light. So, for Young's Slits for example, I would expect to see the bright central band but no other fringes. This is because if a diffracted path has a delay of one wavelength there is nothing there - it is after the pulse. In addition, the screen will be dimly illuminated by the diffracted light from the two slits, but interference will not occur due to the time difference being too great.Mubeen said:TL;DR Summary: ultra short pulse
what will happen if two one femtosecond(1 fs) laser pulse interferes?
IS the process just simple multiplication? The modulation envelope varies with time so it's not just loke multiplying the element pattern by the array pattern. It's a transitory phenomenon.tech99 said:multiplied by the modulation envelope
Can you back up that verbal description with some maths that contains x,y and t? It's true that only in one place and one time are the E fields equal in amplitude and phase but what happens at other times and in other directions. I think the problem with non-continuous waves is that the concept of simple interference could be actually misleading.tech99 said:One ray is progressively delayed as we move from the centre line, so it is sweeping in time across the modulation envelope. The other ray is progressively advanced, so sweeps the other way in time. We then have interference between these two. So if there is just one pulse having a length of one cycle, that is all we see.
In fact, the 'pattern' would not be stationary, which is what happens with a conventional Young's slits pattern at switch on and switch off.sophiecentaur said:that the concept of simple interference could be actually misleading.
Interference of two ultra short laser pulses refers to the phenomenon where two laser beams, each with very short durations (typically in the femtosecond range), overlap in space and time. This overlap can lead to constructive or destructive interference patterns, depending on the phase relationship between the two pulses. The study of this interference provides insights into the temporal and spatial characteristics of the pulses, as well as their interactions with materials.
The temporal overlap of the two ultra short laser pulses is critical for observing interference. If the pulses overlap in time, their electric fields will combine, leading to interference effects. The degree of overlap determines the nature of the interference; a complete overlap can result in strong constructive or destructive interference, while partial overlap may produce more complex patterns. The timing of the pulses can be precisely controlled, allowing researchers to explore the dynamics of the interference in real-time.
Interference of ultra short laser pulses has several applications, particularly in fields such as ultrafast optics, spectroscopy, and material science. It is used to study transient phenomena in materials, measure the temporal dynamics of electronic and molecular processes, and in techniques like pump-probe spectroscopy. Additionally, it plays a role in imaging techniques, such as coherent anti-Stokes Raman scattering (CARS) microscopy, which can provide high-resolution images of biological samples.
Studying the interference of ultra short laser pulses presents several challenges, including the need for precise timing and synchronization of the pulses, which requires advanced equipment and techniques. Additionally, the short duration of the pulses can make it difficult to measure and analyze the resulting interference patterns accurately. Environmental factors such as vibrations, temperature fluctuations, and air turbulence can also affect the stability and coherence of the laser beams, complicating experimental setups.
Interference patterns from ultra short laser pulses can be measured using various techniques, such as interferometry, which involves splitting a laser beam and recombining it after a controlled delay. Detectors, such as photodiodes or CCD cameras, are used to capture the resulting intensity patterns. Advanced analysis techniques, including Fourier transform methods and autocorrelation, can be employed to extract information about pulse duration, shape, and temporal characteristics from the interference patterns. Data processing software is often used to interpret the results and visualize the interference effects.