Third Harmonic Generation Nonlinear Optical Imaging
Prof. Suchi Guha
Department of Physics and Astronomy, University of Missouri, MO, US
Background
Prof. Suchi Guha’s research activity focuses on organic semiconductors and organic optoelectronics, making use of optical imaging and spectroscopy to investigate these materials and their properties. In a 2021 publication (Bhattacharya et al. 2021) Prof. Guha’s team investigated the nonlinear optical properties of lead halide perovskites using third order harmonic generation (THG), comparing CsPbBr3 and MAPbBr3 nanocrystals with and without Ruddlesden-Popper planar faults. This was done to investigate the potential uses of inorganic halide nanocrystals with planar defects for a range of nonlinear optical applications.
The nonlinear optical imaging system in this study was used to visualise and compare THG emission from the different samples using reflection geometry.
THG images from a MAPbBr3 single crystal (left) and films of RP-CsPbBr3 (mid) and non‑RP CsPbBr3 (right). Each image was acquired with the Prime 95B with initial excitation of 1200 nm. Line profiles for each image are taken from the same region, shown with a yellow line.
Challenge
A CMOS camera was required to capture THG images from a range of different nonlinear samples, across a range of illumination intensities. These samples can produce substantial background illumination, requiring a highly sensitive camera to distinguish THG signals from sample noise.
In addition, different nonlinear samples exhibited significantly different THG signal intensities, requiring a CMOS camera that can image both high and low signal levels, preferably at the same time. This would require a large full-well capacity, low read noise, and a large dynamic range mode.
We used the Prime 95B CMOS camera to image third harmonic nonlinear phenomenon from perovskites and compare their intensities.
Prof. Suchi Guha
Solution
The Prime 95B sCMOS camera is an ideal solution for this challenging application, thanks to the combination of high sensitivity, large full-well capacity, and low noise. With a large 11 µm pixel and 95% quantum efficiency thanks to back-illumination, the Prime 95B has unrivalled signal collection. When paired with the low read noise, this results in a highly sensitive sCMOS solution for this application.
The large pixel also results in a large full well, with the Prime 95B able to collect up to 80,000 e- of signal and having a 16-bit mode designed for high dynamic range (HDR) imaging.
Reference
Payal Bhattacharya, Maria V. Morrell, Yangchuan Xing, Cherian J. Mathai, Ping Yu, and Suchismita Guha (2021), Enhanced Third Harmonic Generation in Lead Bromide Perovskites with Ruddlesden–Popper Planar Faults, The Journal of Physical Chemistry Letters 2021 12 (16), 4092-4097, 10.1021/acs.jpclett.1c00555
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