Kindly suggest which type of pattern will be found in the output beam of Mode-locked laser?
AA is right. Harmonic frequencies also are less intense that the source frequency.
Most mode-locked lasers are designed to support the fundamental Gaussian mode, due to some advantages. So usually you should see a Gaussian transverse pattern. Otherwise you see rings and blobs for higher transverse mode lasers.
Actually I am using a side-pumped Nd:YAG laser placing it in a z cavity havinf 1.3 um mirrors. The input frequency is 100 Hz (rep rate). At the back mirror side I have placed the oscilloscope for the measurement of output frequency. But I am not getting any stable or mode-locked frequency. I have set the scale at 500ps/div. How could I get the Mode-locked pulse? Actually I am not finiding out where are the mistakes.
Are you trying to build an oscillator? The information you gave seems a little vague. Getting a ML is a complicated process. For example your mirrors should support the sufficient bandwidth, and there should be some dispersion compassion. Also a choice of active or passive ML should be emade. You can read some detailed theory in my thesis here https://inspirehep.net/record/1387252
Thank you Harsha Panuganti for your reply. I have alighned a z cavity (osillator) already for the generation of second harmonic (SH). And SH is also generated but the mode-locked pulse I could not get. And I don't know how can I get that pulse. Kindly tell me is it possible to generate mode-locked (ML) pulse from a laser diode side-pumped Nd:YAG laser module. And what are the important factors I should follow for generation of ML pulse.
Ruma, based on your description, I will not expect a ML pulse. ML, here, means a pulsed formation. There are requirements for ML. The requirement for a good SHG is high intensity of the source laser. And ML lasers provide high peak intensities, because of the pulsed formation. Although ,note that the average power is same as a CW.
Now you are saying you don't have a ML but still see SHG. That implies that your CW is intense enough to produce SHG. However, a ML pulse will increase the SHG output. From my little knowledge, yes a ML pulse can be generated from a Ti:Sapph laser side pumped by Nd:YAG. But there are a number of things involved to make that happen. as I said you should have something like a modulator for active ML or a ML mirror to generate passive ML. I think the best way for you to figure out where the problem is, is to carefully read the theory to know and understand how ML is generated. My thesis is a good source to know about passive ML, which is used for fs-pulses. If your cavity is designed to produce ns-ps pulses then there should be a modulator that produces active ML. You can read the theory on active ML online. It takes some time to understand these concepts. But I see that's the only way you will figure out where the problem is. Good luck.
Thank you for your suggestion. But there are several works are already done using SHG crystal, brewster plate and Nd:YAG laser. Actuaaly I am not finding out the problem. Kindly send me your thesis so that I can find out some solution.
My thesis can be downloadable here https://inspirehep.net/record/1387252 as sent to you in my previous conversations.
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