k-Wave

1. samantp
   

   Member
   Joined: Jun '16
   Posts: 17

   Hello,
   I am seeking to run a simulation where I vary the pulse width and size of a source (I will simply use a disc source with a Gaussian shape in time using the time varying source problem codes) and examine the effect this has on the frequency. However, the pulse width time scales tend to be much smaller than the time scales of acoustic propagation. So, my question was, is it possible to design such a simulation with enough time steps to allow for both propagation and generation?

   My pulse widths will be in the range of femtoseconds whereas the acoustic propagation will take microseconds. Is it possible to run the first few femtoseconds of the simulation with a small dt, then stop the simulation, export a snapshot of that pressure into a new simulation with a higher dt, and then run that? i.e. is it possible to pause a simulation, export the checkpoint, and then run a simulation from that checkpoint with a different dt?

   Thank you!

   Posted 5 years ago #

2. wenxiu
   

   Member
   Joined: Jul '18
   Posts: 6

   Hello Samantp,

   I'm also a user of k-wave, and I has considered the femtosecond pulse laser simulation. But k-wave seems not suitable for this condition. When the laser excitation is with a femtosecond laser, there may be different acoustic wave generation mechanism such as two-photo effect. Moreover, a paper published at 2014 reported that the pulse width will not influence the amplitude of PA signal, and its pulse width varies from 200fs to 4ps.

   Best wishes!
   Wenxiu

   Posted 5 years ago #

3. samantp
   

   Member
   Joined: Jun '16
   Posts: 17

   Hi Wenxiu, can you please link the paper?
   To the best of my knowledge this is only due to bandwidth limitations on the detection transducers.

   Thank you!

   Posted 5 years ago #

4. wenxiu
   

   Member
   Joined: Jul '18
   Posts: 6

   Hello Samantp,

   Yes, here is the reference.
   Yamaoka Y , Harada Y , Sakakura M , et al. Photoacoustic microscopy using ultrashort pulses with two different pulse durations[J]. Optics Express, 2014, 22(14):17063.

   Best wishes!
   Wenxiu

   Posted 5 years ago #

5. wenxiu
   

   Member
   Joined: Jul '18
   Posts: 6

   Hello samantp,

   What's more, according to my understanding, the femtoseccond is much less than stress confinement and thermal confinement that only the deposited energy will influence the PA signal.

   Best wishes!
   wenxiu

   Posted 5 years ago #

6. Yan
   

   Member
   Joined: Dec '19
   Posts: 6

   Hello samantp,

   I come across with the same questions you asked before. Has your problems been solved now?

   Could you tell me how to define a gaussian pulse source with different pulse width,for example, 9ns, 1ns, 30ps?

   Best wishes!
   Yan

   Posted 4 years ago #

7. Bradley Treeby
   

   Developer
   Joined: Mar '10
   Posts: 1,643

   Hi Yun,

   You can define your source pressure (source.p) using a Gaussian, e.g., by using the gaussian function in k-Wave. Within the help file of the function, there is a formula you can use to convert the FWHM of the pulse to the variance (one of the inputs). Note, you will likely have to make your simulation time step very small to resolve the Gaussian, so the simulation might take some time.

   Brad

   Posted 4 years ago #

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