Browsing by Author "Oran, Abdullah"

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RF injection locked 18 GHz regeneratively mode-locked semiconductor laser
(OPTICAL SOC AMER, 2010 MASSACHUSETTS AVE NW, WASHINGTON, DC 20036 USA, 2018) Oran, Abdullah; Ozharar, Sarper; Can, Gokhan; Olcer, Ibrahim; Ozdur, Ibrahim; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
In this manuscript, a semiconductor based fiber ring cavity mode-locked laser regeneratively driven at 18 GHz is presented. The optical spectrum of the laser is centered at 1578 nm. The laser is RF injection locked via an external source at 18 GHz. The phase noise of the mode-locked laser is measured and the integrated timing jitter was found to be 10.8 fs (from 100 Hz to 20 MHz) and 13.3 fs (from 100 Hz to Nyquist frequency). The integrated amplitude fluctuation (from 100 Hz to 20 MHz) was less than 0.02%. The laser phase and amplitude noise responses to various injected RF power levels were also investigated. The injection RF power has significant effect on the phase noise and the best jitter value is around 40 dB lower than the cavity regenerated RF power. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Three-dimensional imaging in degraded visual field
(Institute of Physics Publishing, 2016) Özharar, Sarper; Ozdur, Ibrahim T.; Oran, Abdullah; AGÜ, Mühendislik Fakültesi, Elektrik & Elektronik Mühendisliği Bölümü;
Imaging at degraded visual environments is one of the biggest challenges in today's imaging technologies. Especially military and commercial rotary wing aviation is suffering from impaired visual field in sandy, dusty, marine and snowy environments. For example during landing the rotor churns up the particles and creates dense clouds of highly scattering medium, which limits the vision of the pilot and may result in an uncontrolled landing. The vision in such environments is limited because of the high ratio of scattered photons over the ballistic photons which have the image information. We propose to use optical spatial filtering (OSF) method in order to eliminate the scattered photons and only collect the ballistic photons at the receiver. OSF is widely used in microscopy, to the best of our knowledge this will be the first application of OSF for macroscopic imaging. Our experimental results show that most of the scattered photons are eliminated using the spatial filtering in a highly scattering impaired visual field. The results are compared with a standard broad area photo detector which shows the effectiveness of spatial filtering. © Published under licence by IOP Publishing Ltd.