Browsing by Subject "Interferometry"

Now showing 1 - 7 of 7

Open Access
Development of a rapid-scan fiber-integrated terahertz spectrometer
(Springer New York LLC, 2014) Keskin, H.; Altan, H.; Yavas, S.; Ilday, F. O.; Eken, K.; Sahin, A. B.
Scientists in terahertz (THz) wave technologies have benefited from the recent developments in ultrafast laser technologies and RF technologies and applied these new gained techniques into characterizing a wide variety of phenomena. Undoubtedly, the most successful of these applications has been in the development of time-domain terahertz spectroscopic and imaging systems which has been utilized in the characterization of dielectrics and semiconductors. This pulsed technique has allowed users to characterize dynamical behavior inside materials under illumination with picosecond resolution. Typically pump/probe or similar dynamical measurements require the use of amplified pulses derived from free-space solid state lasers in the μJ-mJ range and since interferometric techniques are typically used in pulsed measurements the measurement time of a THz spectrum can last at least tens of minutes. Better systems can be realized based on fiber laser technologies. Here we discuss the advantages of a THz spectrometer driven by an ultrafast Ytterbium doped fiber laser whose repetition rate can be tuned rapidly allowing for rapid dynamical measurements. The efficient gain medium, robust operation and compact design of the system opens up the possibility of exploring rapid detection of various materials as well as studying dynamical behavior using the high brightness source.
Open Access
Experimental observation of cavity formation in composite metamaterials
(Optical Society of American (OSA), 2008) Caglayan H.; Bulu I.; Loncar, M.; Özbay, Ekmel
In this paper, we investigated one of the promising applications of left-handed metamaterials: composite metamaterial based cavities. Four different cavity structures operating in the microwave regime were constructed, and we observed cavity modes on the transmission spectrum with different quality factors. The effective permittivity and permeability of the CMM structure and cavity structure were calculated by use of a retrieval procedure. Subsequently, in taking full advantage of the effective medium theory, we modeled CMM based cavities as one dimensional Fabry-Perot resonators with a subwavelength cavity at the center. We calculated the transmission from the Fabry-Perot resonator model using the one-dimensional transfer matrix method, which is in good agreement with the measured result. Finally, we investigated the Fabry-Perot resonance phase condition for a CMM based cavity, in which the condition was satisfied at the cavity frequency. Therefore, our results show that it is possible to treat metamaterial based cavities as one-dimensional Fabry-Perot resonators with a subwavelength cavity. © 2008 Optical Society of America.
Open Access
Fano effect in a double T-shaped interferometer
(Springer, 2009) Moldoveanu, V.; Dinu, I. V.; Tanatar, Bilal
We study the coherent transport in a one-dimensional lead with two side-coupled quantum dots using the Keldysh's Green function formalism.The effect of the interdot Coulomb interaction is taken into account by computing the firstand second order contributions to the self-energy.We show that the Fano interference due to the resonance of one dotis strongly affected by the fixed parameters that characterize the second dot. If the second dot is tuned close to resonance an additionalpeak develops between the peak and dip of the Fano line shape of the current. In contrast, when the second dotis off-resonance and its occupation number is close to unity the interdot Coulomb interaction merely shifts the Fano line and no other maxima appear.The system we consider is more general than the single-dot interferometer studied experimentally by Kobayashi et al. [Phys. Rev. B 70, 035319 (2004)] and may be used for controlling quantum interference and studying decoherence effects in mesoscopic transport.
Open Access
Fourier transform plasmon resonance spectrometer using nanoslit-nanowire pair
(American Institute of Physics, 2019) Uulu, Doolos Aibek; Ashirov, Timur; Polat, N.; Yakar, O.; Balcı, S.; Kocabaş, C.
In this paper, we present a nanoscale Fourier transform spectrometer using a plasmonic interferometer consisting of a tilt subwavelength slit-nanowire pair on a metallic surface fabricated by the focused ion beam microfabrication technique. The incident broadband light strongly couples with the surface plasmons on the gold surface, and thus, surface plasmon polaritons (SPPs) are generated. The launched SPPs interfere with the incident light and generate high contrast interference fringes in the nanoslit. The transmitted SPPs through the metal nanoslit can decouple into free space and are collected by an objective in the far field. The spectroscopic information of the incidence light is obtained by fast Fourier transform of the fringe pattern of the SPPs. In our design, there is no need for a bulky dispersive spectrometer or dispersive optical elements. The dimension of the spectrometer is around 200 μm length. Our design is based on inherent coherence of the SPP waves propagating through the subwavelength metal nanoslit structures etched into an opaque gold film.
Open Access
Integrated micro ring resonator displacement sensor for scanning probe microscopies
(Institute of Physics Publishing, 2004) Kiyat, I.; Kocabas, C.; Aydınlı, Atilla
We describe a novel displacement sensor for scanning probe microscopies using an integrated optical micro ring resonator. This device operates by means of monitoring the changes in the transmission spectrum of a high finesse micro ring resonator. Finite element method simulations were carried out to obtain the optimum sensor design and finite difference time domain simulation was used to obtain the transfer characteristics of micro ring resonators. Operation principles and sensitivity calculations are discussed in detail. To achieve high sensitivity, we have studied different types of ring resonator. The highest sensitivity is obtained in a race-track resonator. This new design should provide sensitivities as high as ∼10 -4 Å -1.
Open Access
Mesoscopic Fano effect in an Aharonov-Bohm interferometer Coulomb-coupled to a nearby quantum dot
(Wiley, 2007) Tolea, M.; Moldoveanu, V.; Tanatar, Bilal
Motivated by the pionieering experiments of Buks et al. [Nature 391, 871 (1998)] we investigate the visibility of the Fano effect in a single-dot Aharonov-Bohm interferometer which is Coulomb-coupled to a nearby quantum dot. The latter acts as a 'Which Path Detector' and is coupled to two leads on which a finite bias is applied. Using the non-equilibrium Keldysh-Green function formalism we compute the currents through the detector and the interferometer. We take into account the first two contributions to the interaction selfenergy and emphasize the correction to the Landauer formula which appears beyond the single-particle approximation. Particular attention is given to the coherence properties of the interferometer in the presence of the electron-electron interaction between the embedded dot and the detector. We show that when the detector is subjected to a finite bias the amplitude of Aharonov-Bohm oscillations of the current through the interferometer decreases. The Fano line is in turn rather stable under interaction. Our results generalize an earlier work of Silva and Levit [Phys. Rev. B 63, 201309 (2001)] and complement the existing description of the controlled dephasing.
Embargo
Suppressing the nonreciprocal errors in a fiber optic rotation sensor
(2024-02) Andaç, Tuğba
Among several other types of rotation sensors, interferometric fiber optic gyro-scopes (IFOGs) shine out as they provide longer lifetime, quicker turn-on time, higher reliability, precision, and sensitivity. However, the fact that any environmental effects distorting the counter-propagating beams from travelling the identical path in a rotating loop induce phase differences apart from the Sagnac effect and cause error leaves them as an application which still needs to be improved. Therefore, we will start by paving the way with the studies we have conducted on the light source for improving its wavelength stability against temperature, and then we will steer our studies toward improving the quality of the fiber optic coil. Although IFOGs being a worldwide hot topic, most of the studies have been carried out by using quadrupole winding pattern, while only little is known when it comes to other winding patterns. Use of hexade-capole winding pattern paints a more promising picture and opens new doors in this research line. Being in the quest of finding a way to improve the performance of these sensors against such disturbing effects, we study and explore the thermal behaviours of the IFOGs built with fiber coils having different winding patterns. We demonstrate that the use of hexadecapole winding pattern overtowers the other winding patterns namely dipole, quadrupole, and octupole in the need of trimming as it presents lower absolute rate error; not only at a certain rate of temperature change but also under different rate of temperature changes. Moreover, we enrich our studies by further investigating the thermal behavior of these sensors, show the independency of Shupe effect in the direction of real rotation, and propose a novel method which eliminates the significance of the symmetry in fiber coil winding. We support our experimental findings with the simulations as well.