arXiv subjects

Sachin Barthwal

Publications and source records attributed to Sachin Barthwal.

4 recordsLinked to original sources

arXiv2019

United test of the equivalence principle at $10^{-10}$ level using mass and internal energy specified atoms

We use both mass and internal energy specified rubidium atoms to jointly test the weak equivalence principle (WEP). We improve the four-wave double-diffraction Raman transition method (FWDR) we proposed before to select atoms with certain mass and angular momentum state, and perform dual-species atom interferometer. By combining $^{87}$Rb and $^{85}$Rb atoms with different angular momenta, we compare the differential gravitational acceleration of them, and determine the value of Eötvös parameter, $η$, which measures the strength of the violation of WEP. For one case ($^{87}$Rb$|\emph{F}=1\rangle$ - $^{85}$Rb$|\emph{F}=2\rangle$),the statistical uncertainty of $η$ is $1.8 \times 10^{-10}$ at integration time of 8960 s. With various systematic errors correction, the final value is $η=(-4.4 \pm 6.7) \times 10^{-10}$. Comparing with the previous WEP test experiments using atoms, this work gives a new upper limit of WEP violation for $^{87}$Rb and $^{85}$Rb atom pairs.

quant-ph↗

arXiv2018

Competition effects of multiple quantum paths in an atom interferometer

We present an observation of competition effect among multiple quantum paths in a Raman-type Mach-Zehnder atom interferometer. By measuring the contrast of interference fringes, the competition effect among multiple interference paths is experimentally investigated. Due to the phase competition, the contrast periodically oscillates when modulating either the phase or the interrogation time between Raman pulses. The multiple quantum paths form because of the imperfect population transfer efficiency in stimulated Raman transitions, and are verified by modulating the duration of Raman pulses. The contrast could be optimized by suppressing the phase competition.

physics.atom-ph↗

arXiv2015

Construction of an inexpensive molecular Iodine spectrometer using a self developed Pohl wavemeter around 670 nm wavelength

We describe construction of an inexpensive Iodine Spectrometer with a home made Iodine vapour cell and a self developed wavemeter based on Pohl Interferometer, around 670 nm wavelength.This can be easily realised in an undergraduate teaching laboratory to demonstrate use of a diode laser interferometry using a Pohl interferometer and measurement of wavelength using image processing techniques.Visible alternative to the IR diode lasers, 670 nm diode laser used here give chance to undergraduate students to perform comprehensive though illustrative atomic physics experiments including the Zeeman effect, the Hanle effect, Magneto Optic Rotation (MOR) effect with a little tweaking in the present spectrometer. The advantage of the spectrometer is its ease of construction with readily available optics, electronics, evacuation and glass blowing facilities and easy analysis algorithm to evaluate the wavelength. The self developed algorithm of raster scanning and circular averaging gives the researcher insight into the basics of image processing techniques. Resolution approaching 0.5 nm can be easily achieved using such simple setup.

physics.optics↗

arXiv2014

Thin film detection of High Energy Materials: Optical Pumping Approach

We present our work on High Energy Material detection based on thin film of Lithium using the phenomenon of Optical Pumping. The Li atoms present in the thin film are optically pumped to one of the ground hyperfine energy levels so that they can no more absorb light from the resonant light source. Now in presence of a RF signal, which quantifies the ambient magnetic field, this polarized atomic system is again randomized thus making it reabsorb the resonant light. This gives a quantified measurement of the magnetic field surrounding the thin film detector. This is then mapped to the presence of magnetic HEM and hence the HEM are detected. Our approach in this regard starts with verifying the stability of Lithium atoms in various solvents so as to get a suitable liquid medium to form a thin film. In this regard, various UV-visible characterization spectra are presented to finally approach a stable system for the detection. We have worked on around 10 polar and non- polar solvents to see the stability criteria. UV-Vis probe has been found to be quite effective in addressing issue of hosting Lithium atoms by various solvents. Further results on the atomic system size as dispersed in the various solvents are presented. Atomic system size gives us a good quantitative estimate of the density of Lithium dispersed system in the thin film. Finally a separate atomic system under Ultrahigh vacuum is presented to achieve optical pumping wherein the polarization and depolarization of atomic system is seen using a 670 nm diode laser system which is electronically locked using a double window Hollow cathode lamp. These both systems will finally be combined together to give the final form to the detection system. As this whole system measures relative change in magnetic field due to the presence of HEM,it gives a more reliable and accurate detection method compared to the absolute measurement detectors.

physics.atom-ph↗