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Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.Xây dựng hệ nghiên cứu tính chất quang của nguyên tử Rubi.
MINISTRY OF EDUCATION AND TRAINING VINH UNIVERSITY - - NGUYEN VAN AI ESTABLISHMENT OF THE SYSTEM TO INVESTIGATE OPTICAL PROPERTIES OF THE ATOMIC RUBIDIUM Specialization: OPTICS Code: 9440110 ABSTRACT OF DOCTORAL THESIS IN PHYSIC NGHỆ AN, 2022 The work is accomplished at Vinh University Adviser: Reviewer 1: Prof Dr Nguyen Huy Bang ……………………………………… …………………………………… Reviewer 2: ……………………………………… …………………………………… Reviewer 3: ……………………………………… …………………………………… The thesis was defended before the doctoral admission board of Vinh University at … h… , … , … , 2022 The thesis can be found at: - Nguyen Thuc Hao Information – Library Centre, Vinh University - Viet Nam National Library PREFACE Reason to choice the investigation subject Spectroscopy is a scientific field that was born a long ago and is associated with important milestones in the history of physic development The development of modern methods and spectrophotometers has gradually elucidated the microstructure of atoms/molecules to the superfine level Design and construction of modern experimental systems to study ultra-high-resolution spectral structures and study atomic optical properties are topics that are always of interest to domestic and international scientists Currently, high-resolution spectroscopy techniques such as saturation absorption spectroscopy (SAS) [1]–[4], combined excitation spectroscopy [3], [4] and polarization spectroscopy techniques are available [4] is used to determine the hyperfine transition of atoms/molecules Thereby, helping us to understand the atomic structure with high precision, so that we can easily manipulate and control them and serve as the basis for the formation of new theories Such as laser cooling and trapping of atoms [5]–[9] or create new materials with special properties such as Electromagnetically Induced Transparency (EIT) [10]– [20] This material is formed by the quantum interference between the displacement probability amplitudes of the quantum states inside the atom under the simultaneous action of the laser fields Typical optical properties of EIT materials include: transparency at resonant frequency, giant Kerr nonlinearity [10], [13], [15], [21]–[26], dispersion rate is extremely large, so the group velocity of the photon is extremely small [27]–[32] In particular, we can control the aforementioned intrinsic properties of atoms external laser With these outstanding properties, EIT materials are expected to create many important applications For example, using EIT materials for light storage [33]–[38], optical bistabilization and optical switching [39]–[43] (a fundamental element for modern optical information processors) will have a sensitivity several million times higher than using traditional Kerr nonlinear materials Furthermore, since the Kerr nonlinear coefficient of EIT materials can be controlled in both magnitude and sign, we can control the optical bistable and all-optical switching characteristics, in other words, the application of This will create active optical switches The basic model for creating EIT materials is based on the association between the three hyperfine states of the atom and two laser fields (in which one laser acts as a driver), so the basic configuration of EIT are atomic systems with three energy levels (lambda, V, and ladder configuration) Under the action of the pump laser beam, the medium becomes transparent with the laser beam detecting at a certain frequency domain (called the transparent window or the EIT window) Although three-energy EIT materials have been widely applied to modern photonic devices [40], [44], this material has only a narrow transparent spectral domain, so the active domain of these devices is limited confined to a small frequency domain Therefore, finding a solution to increase the number of transparent windows of EIT materials has been of interest in scientists today One of the solutions proposed by many scientists is to use atomic systems with close hyperfine states [26], [43], [45], [46], such as alkali metal atom At that time, a laser field can simultaneously link many hyperfine transitions close together, so it is possible to create many transparent windows Besides the EIT effect, ultra-high-resolution spectroscopy can make it easier to observe the Macaluso-Corbino effect (also known as the optical-magneto effect) This effect was first discovered by scientist Faraday when shining light through a solid medium and a liquid crystal medium [47], [48] Then two scientists Macaluso-Corbino observed the rotational effect of the plane of polarization of the light beam travelling through the atomic gas medium and showed that the rotation angle depends on the frequency and intensity of the laser beam [49], [49] 50] Recently, the optical-magneto effect has also received a lot of research attention [51]–[54] because it has many useful applications such as light modulation, supersensitive magnetometer [55]–[57] ], etc In foreign countries, there have recently been some experimental studies on the effect of multiwindow EIT/EIA transparency For example, in 2014 Kang Ying and colleagues observed seven EIT windows in a V-configured Rubi atom when two laser beams pumped and probed in the same direction [45] In 2015, Dipankar Bhattacharyya and colleagues observed five velocity-selectively induced absorption (EIA) peaks, in the six-energy lambda configuration of the Rubi atom [58] Then, Bo-Xun Wang and co-workers integrated a Mach-Zehnder interferometer to observe the group refractive index of the atomic Rubidium vapour medium [26] In 2017, Khairul Islam and colleagues observed six EIA absorption peaks, in the V-shaped five-level atomic system of the Rb atom [59] The experimental observations in the above works are in good agreement with the theoretical model However, the obtained spectral signals are not really clear and other investigations have not been exploited In the country, besides the successes in theoretical research on the EIT effect and related applications, our group has also successfully built an experimental system to observe the electromagnetic induced transparent spectrum of atomic gas Rb at room temperature [23], [60] The advantage of this experimental system is that the EIT spectrum and EIT dispersion spectrum have been observed with three perfect transparent windows (transparency is close to 100%) However, this experimental system also has the disadvantage that the installation is spread out and not flexible, the stability is not high, so some EIT spectral lines have not been observed and it is difficult to perform related experiments requiring high sensitivity as high as Kerr nonlinearity and optical bistable Therefore, the design and construction of a high-resolution spectral experimental system with compact size, high stability, and low cost, which integrates research into many atomic optical properties and related applications is becoming a challenge wishes of research groups in the country and around the world With the desire to build such an experimental system, we chose the topic “Establishment of the system to investigate optical properties of the atomic Rubidium” as our doctoral thesis In this experimental system, we use the Rubi atom for the following reasons: The First is the energy level structure of the Rubi atom have transition frequencies consistent with those of the lasers diode is widely used in the market; The second is the Rb atom of the alkali metal group has one electron in the outermost shell, so it has a simple energy level structure and a relatively close frequency gap between the energy levels Therefore, just using a laser beam can easily link many neighbouring displacements; the Third is the Ruby atom is easily converted to a gas at room temperature, thus making it easy to model Research objectives Design and build a high-resolution spectral experimental system, with compact size, high stability, and low cost, integrating various ultra-high-resolution spectroscopy measurements From there, use the experimental system to study the optical properties of the atomic gas Rubidium Research content To achieve the set objectives, the content of the thesis focuses on the following issues: + Learn about related experimental systems at home and abroad, and understand the advantages and disadvantages of existing experimental systems From there, it is proposed to design and build a versatile experimental system that can investigate many optical properties of the Rubidium vapour medium based on the EIT effect + Develop a procedure for performing spectral measurements of the Rubi atom + Orientation to develop experimental systems for research-related applications Research Methodology - Theory We rely on the principles of high-resolution spectrometry such as absorption and dispersion spectroscopy, velocity-selective optical pump spectroscopy, electromagnetic induced transparency spectroscopy, etc At the same time, based on the principles of measuring effects related such as group refractive index, Kerr nonlinear coefficient, optical bistable, etc Based on semi-classical theory and density matrix formalism to build theoretical models to simulate research results - Experiment + Develop the existing experimental system, build an experimental system that can perform many measurements to study the optical properties of the Rubidium vapour medium + From the data obtained from the measurements, we use data processing software to come up with an experimental path, thereby analyzing the change in the optical properties of the Rubidium vapour medium according to the controlled laser parameters Thesis structure In addition to the introduction and conclusion, the thesis has three chapters presented as follows: Chapter I Principles of high-resolution spectroscopy In this chapter, we present the principles of high-resolution spectroscopy as a basis for building an experimental system to study atomic optical properties Here, we also present the principle of investigating some applications of the electromagnetic induction transparency effect, to guide the construction of a comprehensive experimental system within the framework of the thesis Chapter II Building an experimental system to study optical properties of the atomic Rubidium vapour medium In this chapter, on the basis of some experimental systems on atomic spectrum published in recent years, through analyzing the advantages and disadvantages of the existing experimental systems We build a multifunctional, compact, highly sensitive and stable experimental system that can investigate optical properties Based on the existing equipment in the laboratory, design and build an experimental system for atomic spectroscopy including saturated absorption spectroscopy, saturation dispersion, velocity-selective optical pump spectroscopy, etc… Chapter III Study of the optical properties of atomic gases In this chapter, we carry out spectral measurements to study the optical properties of the medium based on the built experimental system Simultaneously, survey the application measurement models of optical properties of the Rubidium vapour medium Thereby, giving parameters and diagram of measurement principle, as well as additional necessary equipment to develop the built experimental system CHAPTER I PRINCIPLES OF HIGH RESPONSIBILITY spectroscopy In this chapter, we present the principles of high-resolution spectroscopy such as saturated absorption spectroscopy and dispersion spectroscopy, velocity-selective optical pump spectroscopy, electromagnetically induced transparent spectroscopy, group refractive index and nonlinearity Kerr as well as related effects such as optical stability and all-optical switching The contents presented in this chapter are the theoretical basis for building an integrated experimental system to research the optical properties of atomics, which is present in chapter 1.1 Principle of saturated absorption spectroscopy and dispersion saturated spectroscopy 1.2 Principle of velocity-selective optical pump spectroscopy The velocity-selective optical pump spectroscopy system uses two laser beams propagating in opposite directions as shown in Figure 1.6 The first low-intensity laser beam is called the detector laser (DL1) The frequency of the detector laser is locked at a value close to the resonant shift frequency of the spectral region to be investigated DL2 DL1 Figure 1.1 Schematic diagram of the velocity-selective optical pump spectroscopy Hình 1.2 velocity selective optical pump spectroscopy of 85 Rb When the pump laser sweeps through these frequency values, the groups of atoms will respectively switch to the saturation state, so the absorption coefficient for the probe beam decreases This leads to times when the beam intensity increases, so the received signal will be peaks as shown in Figure 1.8 For the 85Rb atom, the window spacing from left to right is 63.40 MHz, respectively; 63.40 MHz; 57.24 MHz; 63.40 MHz; 120.64 MHz 1.3 Principle of electromagnetic induced transparent spectroscopy 1.4 The Macaluso-Corbino Effect 1.5 Some applications of the EIT medium 1.5.1 Measure the speed of the group of light 1.5.2 Kerr Nonlinear 1.5.3 Optical bistability 1.6 Ruby (Rubidium) atom Chapter II BUILDING THE EXPERIMENT SYSTEM INVESTIGATION OPTICAL PROPERTIES OF THE ATOMIC VAPOUR In this chapter, we review some experimental systems that measure spectral atoms in the world and analyze the advantages and disadvantages of the systems On that basis, we designed and built a compact experimental system, integrating many different spectral measurements Which ensures flexibility and ease of switching between different measurements The integrated system also need to ensure accuracy and stability in the measurements 2.1 Some experimental systems measure spectral atoms in the world 2.1.1 The experimental system of Thorlab measures saturated absorption spectroscopy 2.1.2 Experimental system of Teachspin 2.1.3 EIT Experimental system pump-probe V-shaped configuration in the same direction 2.1.4 Experimental system for measuring refractive index of light group 1.5 EIT experiment at Vinh University 2.2 Building a versatile experimental system 2.2.1 General principles On the basis of analyzing the advantages and disadvantages of the above atomic spectrometer experimental systems, we design and build an experimental system that can integrate many spectral measurements The integrated test system must ensure the following requirements: + The path of the light beams is short, minimizing the noise of the Rubidium vapour medium + Multi-function, it could be flexibly switched between measurements + Compact, easy to move The experimental system consists of three main parts with a block diagram as shown in Figure 2.13: Optical parts: The first part is an optical system consisting of optical devices placed on a table with dimensions of 45 cm x 60 cm Control part: consists of three control modules Module controls the DL1 laser source of Teachspin, module controls the DL2 laser source of Moglabs and module controls the temperature of Thorlabs OPTICAL CONTROL DISPLAY Figure 2.1 Block diagram of the compact system The parts of Display and storage: The signals received on the three Photodetectors are connected to a Tektronix electronic oscilloscope Here the data is recorded with images and digital data The layout diagram of optical components on an optical tabletop is shown in Figure 2.14 Here, the position of the optical devices is arranged so that flexibility can be made between different spectral measurements Rb Figure 2.2 Diagram of the arrangement of optical devices on the optical surface of the experiment system investigation optical properties M1 – M7: Mirror; S1 – S3: beam shutter; ND1 – ND3: neutral density filter; BS1 – BS6: beam splitter; FPI: Fabry-Pérot Interferometer ; MZI: Mach-Zehnder Interferometer; P1 – P2: Polarizer; PD1 – PD3 : Photodetector; DL: Laser diode ; IS: optical isolator The system can be used to observe absorption spectroscopy, dispersion spectroscopy, saturated absorption spectroscopy, saturation dispersion spectroscopy, absorption spectroscopy and dispersion spectroscopy in the presence of the EIT effect in case both beams are present at the same time pump in the same direction and in the opposite direction, the change of light beam polarization when passing through the atomic gas medium 2.2.2 Optical parts Figure 2.3 Arrangement of the devices on the optical surface of the experimental system 2.2.3 Control unit 2.2.4 Display Parts 2.3 Schematic diagram of spectroscopy measurements 2.3.1 Optical diagram to observe absorption and dispersion spectroscopy Figure 2.4 Optical diagram to observe absorption spectroscopy Figure 2.5 Optical diagram to observe dispersion spectroscopy 2.3.2 Optical diagram observe the saturated absorption and dispersion spectroscopy 11 Hình 2.10 Optical diagram observe EIT configuration two pump beam 2.3.6 Optical diagram to observe the Macaluso-Corbino effect Chapter III RESEARCH OF OPTICAL CHARACTERISTICS OF ELECTRIC GAS In this chapter, we perform atomic spectrometric measurements of Rb with the experimental system built in chapter Detailed presentation of spectrometric procedures, processing of spectral data and building of theoretical models to explain the results obtained At the same time, there is a comparative evaluation with results from published experimental systems On the basis of spectral measurement results, we also propose some development directions of the experimental system to be implemented in the near future 3.1 Investigation of absorption and dispersion spectra 3.1.1 Measurement process Optical diagrams used to investigate the absorption and dispersion spectra are shown in Figure 2.33 and Figure 2.34 When performing absorption and dispersion spectroscopy of the medium, we use the DL1 laser system of TeachSpin Since the frequency of the laser head depends on the stability of the power supply parameters, the laser source must be turned on for at least 30 minutes before proceeding with further operations Step 1: Turn on the laser source, increase the current for the laser generator to 2.4 mA (Teachspin's diode laser emission threshold), and observe the laser beam with the CCD camera, if the laser signal is bright-dark according, the laser is on work In the case that the laser beam intensity does not change, showing that the laser resonator chamber has not satisfied the resonance conditions for laser activate, we 12 need to adjust the rotation angle of the diffraction mirror, find the position to get the maximum resonance signal (for the laser system we have assembled stably, this process usually does not need to be repeated) Step 2: Increase the current supply to the DL1 up to 5.26 mA, then the wavelength of the laser will go to about 780.24 nm, using the CCD camera to observe the fluorescence emission spectrum of the Rubi atom Adjust the frequency of the DL1 laser so that the signal displayed on the CCD camera screen is a continuous flashing light line Step 3: When the fluorescence spectrum of the medium corresponding to the wavelength of 780.2 nm is observed, adjust the laser beam entering the Fabry- Pérot interferometer so that the received spectral signal appears the signal interference fringe biggest brand Adjust the frequency sweep of the laser to a value of 10 GHz Step 4: Adjust the arms of the interferometer so that the beams of the two interference arms after exiting BS4 coincide, so that the optical path difference is less than 0.5 cm as we argued in Section 1.1 Step 5: Adjust the intensity of the laser beam For the detector laser beam, we have to adjust the laser beam intensity to be less than the saturation intensity Isat = mW/cm2, in this setup we always control the detector laser beam below 0.1 mW /cm2 to avoid the self-focusing effect of the beam Step 6: Connect Photodetector with digital oscilloscope In this system the Photodetector is set to a mode with an impedance ranging from 100 K to M depending on the intensity of the detector laser beam signal 3.1.2 Absorption and dispersion spectroscopy 3.2 Investigation of saturated absorption and dispersion spectroscopy 3.2.1 Measurement procedure 3.2.2 Saturated absorption spectroscopy and saturated dispersion spectroscopy Figure 3.1 Saturated absorption spectroscopy (a) and saturated dispersion spectroscopy (b) The results of the saturated dispersion spectroscopy measurements of the atoms of 87 85 Rb and Rb are shown in Figure 3.2 We see on the dispersion line, at the position of the saturated absorption spectral lines, appear normal dispersion domains Dispersion domains often appear in the background of anomalous dispersion lines The slope of the dispersion line at the location of the hyperfine shifts increases, so that the refractive index of the medium is enhanced 13 3.3 Investigation of EIT spectroscopy and EIT dispersion spectroscopy configuration pump-probe counter-propagating 3.3.1 Procedure measure EIT spectroscopy and EIT dispersion spectroscopy 3.3.2 EIT spectroscopy and EIT dispersion spectroscopy, configuration probe-pump counterpropagating Figure 3.2 Absorption and dispersion spectroscopy of 85 Rb atom in the presence of EIT effect in case the probe beam intensity is equal to 0.07 mW/cm , the associated laser beam intensity is mW /cm2 (a), the dispersion spectroscopy of the atomic gas 85Rb when reducing the associated laser frequency, all dispersion domains shift to the left by 68 MHz (b) The EIT spectrum and EIT dispersion are obtained as shown in Figure 3.7 The measurement results show that the absorption coefficient and refractive index of the medium depend on the intensity and frequency of the pump laser We can obtain up to normal dispersion domains in the anomalous dispersion domain The measured results are consistent with the previous measurement results 3.4 Investigation of EIT spectroscopy and dispersion of EIT configuration pump-probe copropagating 3.4.1 Measurement process 3.4.2 The EIT spectroscopy and dispersion of EIT configuration pump-probe co-propagating 14 Figure 3.3 Absorption ( ) and dispersion ( ) spectra of the 85Rb atom in the presence of the EIT effect We see that, on the Doppler line, there are EIT windows, of which three have the largest intensity corresponding to the shift from right to right of 5S1/2 (F=3) → 5P3/2 (F'=4) of the group of atoms bonded to 5S1/2 (F=3)→5P3/2 (F'=2); 5S1/2 (F=3)→5P3/2 (F'=4) of the group of atoms bonded to 5S1/2 (F=3)→5P3/2 (F'=3) and 5S1 /2 (F=3)→5P3/2 (F'=3) of the group of atoms bonded to 5S1/2 (F=3)→5P3/2 (F'=2) 3.5 Velocity selective optical pump Spectroscopy 3.5.1 Measurement process 3.5.2 Velocity selective optical pump spectroscopy In the case of the pump laser beam in the opposite direction of the detector laser, the obtained spectral image is as shown in Figure 3.9 Here, in case the laser beam is pumped against the detector laser beam, the number of spectral lines obtained is The distance between the spectral lines is 63.41, respectively. 1.12 MHz; 63.42 1.12 MHz; 57.36 1.12 MHz; 63.39 1.12 MHz; 120.6 1.12 MHz Figure Velocity-selective optical pump spectroscopy configuration probe-pump counter-propagating of 85Rb Comparing the experimental results with the theoretical model as presented in Section 1.2, we find that the positions of the spectral lines are consistent with the given theoretical model The spectral line intensity corresponding to the fourth and fifth largest shifts due to the superposition enhances the electromagnetic transparency of the two groups of atoms B, C and A, C 3.6 Investigation EIT spectroscopy configuring two pump beams in opposite directions 3.6.1 Measurement process 3.6.2 EIT spectroscopy of two pump beams in the same direction and opposite direction as the detector beam In this experiment, we measure the absorption spectroscopy in the presence of the EIT effect using two pump laser beams These two beams separate from the DL2 laser, which propagate in opposite directions Fixed frequency of DL2 at offset = 100 MHz relative to shift F = F= to red region Adjust the intensity of the two laser beams to the value of mW/cm2, the received signal is shown in Figure 3.10 Figure 3.10a shows that the detector laser beam signal has a Gaussian shape, there are 13 EIT windows 15 on the Doppler expansion line corresponding to a shift of 52 S1/2 (F = 3) → 52 P3/2 (F' = 2, 3, 4) of six groups of atoms moving thermally with different velocities Figure EIT spectroscopy of 13 windows on the Doppler line of the 85Rb atom a) experiment, b) theory To explain the experimental results, we use a four-energy-level model, V-configuration The number of transitions is determined according to the energy level diagram as shown in Figure 3.11, we consider two cases: In the first case, pump-probe co-propagating, the pump beam is associated with three displacements |1|2, |1|3 and |1 |4 corresponding to three groups of atoms A, B, C Due to the effect Doppler, the probe beam will have three resonance frequency values for each group of atoms However, there is one frequency value of the probe beam that resonates with all three groups of atoms, so we get seven detector beam frequencies that resonate with all three groups of atoms Group A: pA1 = 12 - c2 = c, (3.3) pA2 = 13 - c2 = 13 - 12 + c, (3.4) pA3 = 14 - c2 = 14 - 12 + c (3.5) pB1 = 12 - c3 = 12 - 13 + c, (3.6) Group B: pB2 = 13 - c = c, (3.7) pB3 = 14 - c3 = 14 - 13 + c (3.8) Cp1 = 12 - c4 = 12 - 14 + c, (3.9) Group C: 16 Cp2 = 13 - c4 = 13 - 14 + c, Cp3 = 14 - c4 = c (3.10) (3.11) The second case, pump-probe counter-propagating, the pump beam is associated with three displacements |1|2, |1|3 and |1|4 corresponding to three groups of atoms D, E, H Due to the effect Doppler, the detector beam will have three resonance frequency values for each group of atoms However, there are three overlapping frequency values of the three groups of atoms, so we get only frequencies of probe beam that resonate with all three groups of atoms Group D: pD1 = 12 + c2 = 212 - c, (3.12) pD2 = 13 + c2 = 13 + 12- c, (3.13) pD3 = 14 + c2 = 14 + 12 - c (3.14) pE1 = 12 + c3 = 12 + 13 - c, (3.15) Group E: pE2 = 13 + c3 = 213 - c, (3.16) pE3 = 14 + c3 = 14 + 13 - c (3.17) pH1 = 12 + c4 = 12 + 14 - c, (3.18) pH2 = 13 + c4 = 13 + 14 - c, (3.19) Group H: pH3 = 14 + c4 = 214 - c (3.20) Therefore, we obtain 13 EIT windows when changing the probe laser frequency as the results in Figure 3.10b (see Appendix B) The experimental results obtained are the positions of the EIT windows corresponding to the displacements as shown in Table 3.1 (see details in the thesis) 3.7 Investigation of electromagnetic induced absorption (EIA) spectroscopy in pump-reverse detector configuration 3.7.2 EIA spectrum in reverse pump-detector configuration The obtained results of EIA spectral signal as shown in Figure 3.12 17 Figure Absorption spectrum in the presence of EIA effect corresponding to the 52S1/2 (F = 1) 52P3/2 (F = 0, 1, 2) shift of the 87Rb atomic We see that on the absorption background five EIA peaks appear, the model explaining the formation of EIA peaks is shown as shown in Figure 3.13 During frequency shift the laser beam injects an amount of 169.9 1.12 MHz, the received beam spectral signal shows that when increasing the pump laser beam frequency to 169.90 1.12 MHz, the resonance absorption peaks are shifted to the right by the same amount and equal to 169.90 1.12 MHz The image of the detector laser beam spectrum when changing the pump laser frequency is shown in Figure 3.1.2b The absorption coefficient of the medium depends on the frequency of the detector laser and the pump laser When the pump laser is locked at frequency c near displacement 52 S1/2 (F = 2) 52 P3/2 (F = 2), the absorption coefficient of the enhanced medium at five frequencies p1 , p2 , p3 , p4 , p5 as given in expressions (3.26) to (3.30) 3.8 Investigation of the Macaluso-Corbino effect 3.8.1 Measurement process 3.8.2 Macaluso-Corbino Effect (MC) The experimental results show that, when there is no magnetic field and fix the polarizer P1, if we change the polarization direction of the polarizer P2, the intensity of the spectral signal changes, but the shape of the spectrum signal is unchanged This shows that the polarization direction of the beam as it passes through the medium is independent of frequency (Figure 3.15a) 18 (a) Probe response [arb units] B=0 300 00 85 87 Rb F=2 Rb F=3 85 Rb F=2 -300 87 Rb F=1 (b) B = 48 G 300 87 Rb F=2 85 Probe response [arb units] (c) 87 Rb F=2 85 Rb F=3 85 Rb F=3 Rb F=2 87 Rb F=1 p (GHz) p (GHz) 300 B = 48 G B=0 85 Rb F=2 Rb F=2 (d) -300 87 85 Rb F=3 B = 48 G B=0 85 Rb F=2 87 Rb F=1 87 Rb F=1 p (GHz) - 300 p (GHz) Figure 3.15 The results investigating experimentally the Macaluso - Corbino effect: (a) B = 0; (b) B = 48 Gauss; (c, d) the comparison in the presence of a magnetic field and when magnetic field is zero When current intensity reaches I = 1.5A, the magnitude of the magnetic induction B = 48 Gauss, we obtained spectral signal corresponding to frequencies near transition D2: 52S1/2(F = 3) 52P3/2(F = 2, 3, 4); 52S1/2(F = 2) 52P3/2(F = 1, 2, 3) of the atom 85Rb and 52S1/2 (F = 2) 52P3/2 (F = 1, 2, 3); 52S1/2 (F = 1) 52P3/2 (F = 0, 1, 2) of the atom 87Rb has variable shape and intensity (Figure 5b, c, d) Figure 5b shows that when the polarizer is placed at an angle of 300, the spectral signals obtained at the resonance shifts change more than when the polarizer is placed at -300 This shows that when the frequency of the laser beam approaches the resonance transitions, the polarization direction of the light beam rotates in a negative direction Therefore, when a magnetic field is present, the spectral signals obtained at the resonant transitions change more The variation of the spectral signal in resonance transitions compared to the case in the absence of a magnetic field for both rotational angles 300 and -300 is shown in Figures 5c and 5d Figure 5d shows that when the magnetic field is present, the spectral signal obtained at transition 52S1/2(F = 3) 52P3/2(F = 2, 3, 4) of the atom 85Rb is smaller than without magnetic field, whereas at transition 52S1/2(F = 2) 52P3/2(F = 1, 2, 3) of the atom 85Rb the spectral signal obtained was greater than without magnetic field This proves that the polarization rotation angle at transition 52S1/2(F = 3) 52P3/2(F = 2, 3, 4) is greater than 600 while the polarization rotation angle at transition 52S1/2(F = 2) 52P3/2(F = 1, 2, 3) is less than 600 19 Probe response [arb units] Theory p (GHz) Figure 3.16 The dependence of the rotation angle of the polarization plane on the external magnetic field strength, the top purple line is the theoretical simulation line, the lower lines correspond to the experimental lines of the other magnetic values when considering = 600 By varying the different magnetic field values, the measurements of the polarization plane rotation angle at resonant frequencies We found that as the magnetic field increased, the polarization plane rotation angle increased at near-resonant frequencies Based on the theoretical model and simulation [15], we find that the simulation results agree with the experimental results obtained with the same gas atom Rb (Figure 3.16) 3.9 Investigation Optical switching 3.9.1 Theoretical model Consider the V + Ξ double configuration four-level atomic system as shown in Figure 1.1 a Accordingly, the system consists of a ground state |1 and three excited states |2 , |3 , |4 respectively with energy levels |5S 1/2 , F = , |5P 3/2 , F = , |5P 1/2 , F = , |5D 5/2 , F = as depicted in Figure 1.15 b The probe beam has a weak intensity with frequency p and Rabi frequency p acting on the transistions |1|2, |1|3 and |2|4 are excited by laser coupling (frequency c) and signal lasser (frequency s) with Rabi frequency c and s , respectively Here, the probe field (solid line) is a continuous wave that has been converted by the signal field In Figure 1.1 a, the signal field strength is Ω s (τ) = Ω s0 {1 − 0.5tanh [0.4(τ − 20)] + 0.5tanh[0.4(τ−45)] − 0.5tanh[0.4] (τ−70)] + 0.5tanh[0.4(τ−95)]} with period 50/21 In Figure 1.1 b, the strength of the signal field is Ωs (τ) = Ωs0 {1 − 0.5tanh[0.2(τ−40)] + 0.5tanh[0.2(τ−90)] − 0.5tanh[0.2 (τ−140)] + 0.5tanh[0.2(τ−190)]} with a period of approximately 100/21 In both cases, the amplitude of the signal field is normalized by the peak value Ωs0 = 21 From Figure 3.16a shows that the period of the probe beam and the period of the signal beam are the same Furthermore, the probe beam is switched in ON or OFF mode when the signal beam switches the signal from OFF or ON respectively On the other hand, the probe pulse oscillation will be suppressed when the signal pulse width is large (Figure 3.26b) 20 Figure 26 (a) V + Ξ double configuration atomic diagram, (b) energy level diagram of atom 87 Rb Figure 27 Continuous probe beam signal change as the signal field transitions with periods of 50/21 (a) and 100/21 (b) With the parameters Ω p0 = 0.01 21 , Ω s0 = Ω c = 21 , p = 0, c = 0, s = 0; time τ is in units of 21 -1 3.9.2 Experimental model 3.10 Investigation of negative refractive index in the atomic medium 3.10.1 Theoretical model The principle of measuring the negative refractive index of the EIT medium is similar to that of the dispersion measurement of the EIT effect presented in Section 2.3.1 Here, we build a theoretical model to create a negative refractive index in the medium of Rubi atom gas based on the EIT effect From there, it is possible to find the necessary parameters for the investigation by negative refractive index experiment We consider a Three-level lambda-type atomic system as shown in Figure 3.19 Figure 3.7 Three-level lambda-type atomic system is excited by the probe and coupling fields 21 We can determine the refractive index of the medium as follows: n r D r D (3.47) We apply the calculation results to the 87Rb atom with the states 5S 1/2 (F = 1), 5P 1/2 (F = 2) and 5S 1/2 (F = 2), respectively energy levels , and Atomic density and other parameters are N = 10 27 atoms/m3 , m = 1.44 1027 kg, d 21 = 1.2 1029 Cm, m 31 = 7.26 1023 Am2 , 21 = 23 = MHz, 0 = 8.85 1012 Fm1 , 0 = 4 107 NA2 and k B = 1.38 1023 J/K The amplitude of the negative refractive index changes when the intensity of the pump laser is adjusted For example, We fix the probe frequency detuning at p = MHz which corresponds to the negative index region in figure 3.21, and study the influence of the coupling laser intensity on the negative refractive index The graphs of relative permitivity anh relative permeability, and the refractive index versus the coupling Rabi frequency when p = MHz, c = MHz, and T = 300 K are shown in figure 3.22 From figure we can see that both relative permittivity (dashed line) and relative permeability (solid line) varies from to 100 MHz It is beacause for given frequency of the probe beam, a change in coupling laser intensity can lead to transition between electromagnetically induced transparency (EIT) and electromagnetically induced absorption (EIA) [54], which changes the corresponding disperion properties In this case, we also find the medium shows negative reflective index when 38 MHz < c < 78 MHz 3.10.2 Experimental model 3.11 Some extended studies of the integrated experimental system 3.11.1 Measure the speed of the group of light propose a intuitive light group velocity measurement scheme which is relying on the propagation pulse deviation of two lasers with different emission frequencies, one passing through the sample chamber and the other as a reference pulse Optical diagram of light group velocity measurement based on the comparison of optical path difference of two light pulses arranged as Figure 3.17 In this optical scheme, We add two more electro- 22 optical modulators (AOM - Acousto-optic modulator) for generating pulses (nanosecond size) for the detector laser and the reference laser Figure Installation diagram of light group velocity measurement system 11.2 Observe Kerr nonlinear coefficient The layout of the Kerr nonlinear measurement experiment is shown as shown in Figure 3.18 The construction system is similar to the group velocity measurement system We just added an electro-optical modulator (EOM - Electro-Optic Modulator ) to modulate the intensity of the detector and reference laser beams Figure 3.9 Installation diagram of nonlinear Kerr measurement 3.11.3 Additional equipment and components required to develop the experimental system The optical switching system is developed based on the integrated experimental system presented in Chapter II Therefore, the equipment used for the optical switching system is similar to that described in section 2.2 The LD3 laser is a Moglabs laser as described in section 2.2 In addition, the system also needs to add the following devices: a Electro-Optical Modulator (EOM) b Optical Acoustic Modulator (AOM) 23 GENERAL CONCLUSION We have successfully designed and built experiment system, which integrating the following techniques: + Measure the absorption spectroscopy and saturated absorption spectroscopy + Measurement of dispersion spectroscopy and saturated dispersion spectroscopy + Measure EIT absorption and dispersion spectroscopy with three configurations (probe-pump counter propagating, probe-pump co-propagating, and two pump beams) + Measure the EIA absorption spectrum in case the probe-pump counter-propagating Compact optical benchtop construction (45 cm x 60 cm), easy switching between measurement configurations by opening and closing the block beam and rotating the Mirrors This allows us to save more costs than the case of building on many spread test systems, the design of the flexible system helps us to save time on installation and surveying difficult experiments We have built a theoretical model to explain the measured results on the experimental system and the procedure of the measurements, helping users (especially at universities) Some new research results when applying the experiment system and research model + Observing the 85Rb atomic spectrum by velocity-selective optical pump spectroscopy, we obtained spectral lines corresponding to the 52S1/2 ( F = 3) → 52P3/2 ( F' = 2, 3, 4) of three groups of atoms interacting with the pump laser The obtained results show that the positions of the spectral lines are consistent with the theoretical model we have built + Observe the EIT spectrum to obtain EIT windows in the case of the probe-pump counter-propagating, EIT windows in the case of the probe-pump co-propagating, and 13 EIT windows in the case of the advent of both pump beams The number of obtained windows is more than the number of windows of the first EIT observation system built at Vinh University (3 windows) Here, we have also built a theoretical model explaining the formation of windows as well as changing the parameters to control the position and intensity of the spectral lines and observe the dispersion spectrum in the presence of the effect EIT + The Macaluso- Corbino effect is observed, opening up the potential to study the phenomenon of opticalmagneto switching experimentally in the near future + On the basis of the components and equipment of the experimental system and the layout design of optical components in the experimental system, we have also proposed to build an experimental system for measuring the speed of light group, measuring refractive index Kerr power and optical switching + Successfully built a theoretical model to study the refractive index of the Rubidium vapour medium and discovered that a negative refractive index can be created in the Rubidium vapour medium when advent EIT effect, thereby providing an experimental model for further research experiment in the future 24 + Successfully built an experimental model to study the possibility of all-optical switching in the Rubidium vapour medium by using three laser beams with wavelengths of 776 nm, 780 nm and 795 nm Thereby proposing an experimental model that can observe the phenomenon of optical switching and optical bistable in the Rubidium vapour medium The research results have been published in international and national journals with significance + In terms of science: The project has built an experimental system to study optical properties of the Rubidium vapour medium, performing more than 12 spectral measurements with results consistent with the built theoretical model The topic has also built a theoretical basis for studying magnetic-optical switching and investigating the negative refractive index to select the basic parameters, thereby providing the necessary equipment to add to the experimental system to have future application development + In terms of practice: The project builds a built-in experimental system with compact size, integrating many measurements, low cost, easy to flexibly switch between spectral measurements, reducing the installation time of the measurements measure Here, the topic also provides a detailed procedure for making measurements on the experimental system to help researchers easily continue to perform The results of the project have been published in prestigious domestic and international journals and a patent application has been accepted SCIENTIFIC WORKS OF THE AUTHOR A Articles relative to the thesis Nguyen Van Ai, Nguyen Huy Bang and Le Van Doai, “Negative refractive index in a Doppler broadened three-level Λ-type atomic medium”, Physica scripta, 97 (2022) 025503 https://doi.org/10.1088/14024896/ac437a Khoa Dinh Xuan, Ai Nguyen Van, Dong Hoang Minh, Doai Le Van, and Bang Nguyen Huy “AllOptical Switching In A Medium of A Four-Level Vee-Cascade Atomic Medium”, Optical and quantum electronics, 164 (2022) 63 https://doi.org/10.21203/rs.3.rs-833664/v1 Nguyen Van Ai, Do Mai Trang, Le Canh Trung, Luong Thi Yen Nga, Trinh Ngoc Hoang, Le Van Doai, Nguyen Van Phu, Dinh Xuan Khoa and Nguyen Huy Bang, “Phổ tán sắc hiệu ứng EIT mơi trường khí ngun tử 85Rb có hiệu ứng Doppler,” Tạp chí khoa học trường Đại học Vinh, Tập 49 - Số 4A/2020, tr 5-11 Le Canh Trung, Nguyen Van Ai, Phan Van Thuan, Dinh Xuan Khoa, and Nguyen Huy Bang, “Measurement of dispersion in a Doppler broaden 87Rb atoms under optically saturated excitation”, The 5th Academic Conference on Natural Science for Young Scientists, Masters, and PhD Students from ASEAN Countries, 4-7 October 2017, Da Lat, Vietnam, ISBN: 978-604-913-088-5, pp 98-103 Phan Van Thuan, Ta Tram Anh, Le Canh Trung, Nguyen Tien Dung, Luong Thi Yen Nga, Dinh Xuan Khoa, Le Van Doai, Nguyen Huy Bang, and Nguyen Van Ai ‘Controlling Optical Bistability in a Five-Level Cascade EIT Medium’ Communications in Physics 26, no (18 July 2016): 33–33 https://doi.org/10.15625/0868-3166/26/1/8213 Nguyen Van Ai, Le Van Doai, Do Mai Trang, Phan Van Thuan, Dinh Xuan Khoa, and Nguyen Huy Bang, “A novel compact spectroscopic setup for teaching atomic physics in universities”, submitted to Physical Review A (2022) B The Invention Title: The KIT produces electromagnetic induced transparency (EIT) and super-high-resolution spectroscopy (accepted), intellectual property office of VietNam (Series Number: 1-2021-01614) C Reports presented at scientific workshops Le Canh Trung, Nguyen Van Ai, Phan Van Thuan, Dinh Xuan Khoa, and Nguyen Huy Bang, “Measurement of dispersion in a Doppler broaden 87Rb atoms under optically saturated excitation”, The 5th Academic Conference on Natural Science for Young Scientists, Masters, and PhD Students from ASEAN Countries, 4-7 October 2017, Da Lat, Vietnam (Oral), ISBN: 978-604-913-088-5, pp 98-103 Nguyen Van Ai, Le Canh Trung, Phan Van Thuan, Dinh Xuan Khoa, and Nguyen Huy Bang, “A compact setup for generation of multi-eit in a Rubidium atomic gaseous medium”, Hội nghị quang học quang phổ lần thứ 10, 10-15 tháng 11 năm 2018, Quảng Ninh, Vietnam (Oral) Nguyen Huy Bang, Nguyen Van Ai, Phan Van Thuan, Luong Thi Yen Nga, Le Canh Trung, Dinh Xuan Khoa, “A compact spectroscopic setup for teaching Atomic physics in universities”, The 6th Academic Conference on Natural Science for Young Scientists, Masters, and PhD Students from ASEAN Countries, 23-26 October 2019, Thai Nguyen, Vietnam (Oral), ISBN: 978-604-913-088-5, pp 98-103 Nguyen Van Ai, Le Canh Trung, Phan Van Thuan, Dinh Xuan Khoa, and Nguyen Huy Bang, “Observation of mutil EIT in doppler broadening atomic gas”, The Conference New Trends in Contemporary Optics, 23- 29 september 2019, Vinh university,Vinh, Vietnam (Poster) Nguyen Van Ai, Do Mai Trang, Nguyen Van Phu, Le Canh Trung, Phan Van Thuan, Luong Thi Yen Nga, Nguyen Huy Bang, “Observation of Macaluso-Corbino Effect in a gaseous Rubidium”, Hội nghị quang học quang phổ lần thứ 11, - tháng 11 năm 2020 Tp Hòa Bình, Việt Nam (Poster) Nguyen Van Ai, Le Van Doai, Luong Thi Yen Nga, Phan Van Thuan, Dinh Xuan Khoa and Nguyen Huy Bang, “Compact intergraded experimental system for observation fundamental atomic spectra”, The 7th academic conference on natural science for young scientists master and PhD Students from Asian countries (CASEAN7) , 14-17 October, 2021, Ha Noi - Vinh, Vietnam (Oral) ... “A compact setup for generation of multi-eit in a Rubidium atomic gaseous medium”, Hội nghị quang học quang phổ lần thứ 10, 10-15 tháng 11 năm 2018, Quảng Ninh, Vietnam (Oral) Nguyen Huy Bang,... Nguyen Huy Bang, “Observation of Macaluso-Corbino Effect in a gaseous Rubidium”, Hội nghị quang học quang phổ lần thứ 11, - tháng 11 năm 2020 Tp Hịa Bình, Việt Nam (Poster) Nguyen Van Ai, Le
