I have grown the crystals of inorganic materials doped with amino acids viz threonine, basically my material have applications in nonlinear optics. so for that ideally my materials should behave like nlo materials and it should show second harmonic generation. when i take second harmonic generation of my grown crystals which are doped with amino acids so i found that the SHG efficiency is to be decrease rather than increase. so please tell me what are the reasons behind that.
Jaudeep.
The problem you are having more likely has to do with nonlinear conversion length. The best SHG is obtained when you fulfill phase matching conditions. To increase the signal you should find the phase matching conditions in either angle or temperature, or determine the optimum length for the xtals to maximize SHG. If the xtal is larger than the NLO length the signal does decrease rather than increase if phase matching is not achieved.
When you alter the material there is morphological change in the material and the optimum conditions change. So when doping with the amino acids more likely you have a different material and the optimum conversion conditions do change with respect to with the pure material. Not strange at all.
Look for the Kurtz powder test (Kurtz Perry Journ Appl Phys, 39,1968, 3798) which is used to determine the capabilities of new materials. Maker fringes technique (Maker, Terhune et al PRL 8, 21 1962) or any wedge technique could also prove useful. Then characterizing the material structure to find which tensor elements are active, meaning in which directions and polarization you observe SHG.Good luck with the characterization
Jaudeep.
The problem you are having more likely has to do with nonlinear conversion length. The best SHG is obtained when you fulfill phase matching conditions. To increase the signal you should find the phase matching conditions in either angle or temperature, or determine the optimum length for the xtals to maximize SHG. If the xtal is larger than the NLO length the signal does decrease rather than increase if phase matching is not achieved.
When you alter the material there is morphological change in the material and the optimum conditions change. So when doping with the amino acids more likely you have a different material and the optimum conversion conditions do change with respect to with the pure material. Not strange at all.
Look for the Kurtz powder test (Kurtz Perry Journ Appl Phys, 39,1968, 3798) which is used to determine the capabilities of new materials. Maker fringes technique (Maker, Terhune et al PRL 8, 21 1962) or any wedge technique could also prove useful. Then characterizing the material structure to find which tensor elements are active, meaning in which directions and polarization you observe SHG.Good luck with the characterization
@ C.G Treviño-Palacios: I have like same problem I synthesized inorganic material which is NLO material but result of SHG shows 0 mV means?
Hi Jaydeep,
to fully characterise nonlinear crystals, it is - among other things - necessary to measure all refractive indices at least for the two wavelengths used in SHG. Using the refractive indices, it would be possible to calculate the angles for phase matching. See appropriate textbooks for that.
Dear Jaydeep.
Please follow the remark from C.G Treviño-Palacioswhich may be the reason of your SHG decrease when doping your crystals with amino acids.
Also ensure that your material is not absorbing at the fundamental wavelength (or at the second harmonic) which might also explain your SHG decrease.
When you dope your crystals, does your system corresponds to a solid solution or a demixion at the solid state (e.g. microstructure)?
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