We report on the quality assessment of an optical coherence tomography (OCT) image. A set of recent digital filters are used for denoising the interferometric signals. It is found that when a combination of continuous wavelet transform (WT) decomposition and the WT denoising techniques is imposed on raw signals, the highest signal-to-noise ratio of 17.8 can be reached. The structural similarity (SSIM) index is eventually employed to evaluate the modality of the reconstructed OCT image. Further, we found out that a SSIM value of about 0.95 can be reached, independent of the method used for envelope extraction.
An antiresonant ring (ARR) interferometer configuration is introduced for the characterization of a continuous wave (CW) Nd:YAG laser output. The output of the ARR device is precisely characterized to determine the gain and loss of a laboratory CW Nd:YAG laser by using the Findlay-Clay approach. The ARR arm is then experimentally arranged inside the cavity of an arranged high power side-pumped CW Nd:YAG laser. A coated beam splitter with 50-50% reflectivity at normal incidence is placed inside the cavity to provide a wide range of reflectivity from 0 to 100%. This is performed by a rotatable stage and tilting the beam splitter by 10• with the steps of 0.05. By changing the input electrical power of the laser pump the variation of the output laser power is monitored for 20 individual reflectivity of ARR arm. Average pump threshold power of about 180 W is obtained. With the help of the derived equations and obtained threshold power, small signal gain and loss associated with the emerging beam is estimated. It is verified that the former is very dependent to the input parameters. Laser efficiency is also measures 5.6% which is quite comparable with the reported values.
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