Spatial modulation of THz beams for imaging applications

Techniques based on compressive sensing allow us to image fields at faster rates and at our labs in METU we have been experimenting with imaging based on spatial modulation of THz beams using single pixel detectors [1]. However these studies are based on discrete patterns using metal sheets. These techniques would benefit greatly if we could modulate the THz field. For example, optical modulators play a key role in optoelectronics and communication systems. Electro-optic, acousto-optic and thermo-optic effects are well established mechanisms to control intensity, phase or polarization of light in the visible and near infrared frequencies. Efficient control of terahertz waves, however, has been a challenge due to the lack of a THz active material. Graphene is a viable material for active terahertz (THz) devices [2]. Electrostatic tuning of high mobility carriers on graphene provides an electrical means for controlling THz waves. Here we demonstrate a terahertz intensity modulator using a graphene supercapacitor which consists of two large area graphene electrodes and electrolyte medium. By patterning the device into an array the potential for rapid imaging is demonstrated. These works are discussed in the context of current mm wave/THz stand-off imaging investigations taking place in our laboratories.
International Symposium on Light and Life, 14-16 October 2015


3D scanning Hall probe microscopy with 700 nm resolution
DEDE, MUNIR; AKRAM, RİZWAN; Oral, Ahmet (2016-10-31)
In this report, we present a three dimensional (3D) imaging of magnetic field vector (B) over right arrow (x,y,z) emanating from the magnetic material surfaces using a scanning Hall probe microscopy (3D-SHPM) down to a 700 nm spatial resolution. The Hall probe is used to measure B-z(x,y) on the specimen surface at different heights with the step size of Delta z = 250 nm, as we move away from the surface in z direction, until the field decays to zero. These set of images are then used to get partial derivati...
Spatial Filtering of MEG Signals for User-Specified Spherical Regions
Özkurt, Tolga Esat; Sun, Mingui; Jia, Wenyan; Sclabassi, Robert J. (2009-10-01)
We introduce a spatial filtering method in the spherical harmonics domain for constraining magnetoencephalographic (MEG) multichannel measurements to any user-specified spherical region of interest (ROI) inside the head. The method relies on a linear transformation of the signal space separation inner coefficients that represent the MEG signal generated by sources located inside the head. The spatial filtering is achieved effectively by constructing a spherical harmonics basis vector that is dependent on th...
Quantitative atom-resolved force gradient imaging using noncontact atomic force microscopy
Oral, Ahmet; ÖZER, HAKAN ÖZGÜR; HOFFMANN, PM; PETHICA, JB (2001-09-17)
Quantitative force gradient images are obtained using a sub-angstrom amplitude, off-resonance lever oscillation method during scanning tunneling microscopy imaging. We report the direct observation of short-range bonds, and the measured short-range force interaction agrees well in magnitude and length scale with theoretical predictions for single bonds. Atomic resolution is shown to be associated with the presence of a prominent short-range contribution to the total force interaction. It is shown that the b...
Sensor Fusion of a Camera and 2D LIDAR for Lane Detection
Schmidt, Klaus Verner (null; 2019-04-26)
This paper presents a novel lane detection algorithm based on fusion of camera and 2D LIDAR data. On the one hand, objects on the road are detected via 2D LIDAR. On the other hand, binary bird’s eye view (BEV) images are acquired from the camera data and the locations of objects detected by LIDAR are estimated on the BEV image. In order to remove the noise generated by objects on the BEV, a modified BEV image is obtained, where pixels occluded by the detected objects are turned into background pixels. Then,...
Comparative evaluation of SAR image formation algorithms
Şahin, Halil İbrahim; Dural Ünver, Mevlüde Gülbin; Koç, Seyit Sencer; Department of Electrical and Electronics Engineering (2010)
In the scope of this thesis, simulation-based analyses and comparative evaluation of Synthetic Aperture Radar (SAR) image formation techniques, namely Time Domain Correlation, Range Stacking, Range Doppler and Chirp Scaling algorithms, are presented. For this purpose, first, the fundamental concepts of SAR such as SAR geometry, resolution and signal properties are explained. A broadside SAR simulator that provides artificial raw data as an input to the algorithms is designed and implemented. Then, the mathe...
Citation Formats
H. Altan, “Spatial modulation of THz beams for imaging applications,” presented at the International Symposium on Light and Life, 14-16 October 2015, Islamabad, Pakistan, 2015, Accessed: 00, 2021. [Online]. Available: