Showing papers on "Doppler broadening published in 2022"
TL;DR: In this article , a solution-based transfer-free coating method was used to integrate two-dimensional (2D) graphene oxide (GO) films onto the SOI nanowires with precise control of the film thickness.
Abstract: We experimentally demonstrate enhanced spectral broadening of femtosecond optical pulses after propagation through silicon-on-insulator (SOI) nanowire waveguides integrated with two-dimensional (2D) graphene oxide (GO) films. Owing to the strong mode overlap between the SOI nanowires and the GO films with a high Kerr nonlinearity, the self-phase modulation (SPM) process in the hybrid waveguides is significantly enhanced, resulting in greatly improved spectral broadening of the femtosecond optical pulses. A solution-based, transfer-free coating method is used to integrate GO films onto the SOI nanowires with precise control of the film thickness. Detailed SPM measurements using femtosecond optical pulses are carried out, achieving a broadening factor of up to ~4.3 for a device with 0.4-mm-long, 2 layers of GO. By fitting the experimental results with the theory, we obtain an improvement in the waveguide nonlinear parameter by a factor of ~3.5 and in the effective nonlinear figure of merit (FOM) by a factor of ~3.8, relative to the uncoated waveguide. Finally, we discuss the influence of GO film length on the spectral broadening and compare the nonlinear optical performance of different integrated waveguides coated with GO films. These results confirm the improved nonlinear optical performance of silicon devices integrated with 2D GO films.
15 citations
TL;DR: In this article , optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of [Formula: see text]Rb D2 transition, which involves the Doppler broadening effect, are solved.
Abstract: In this study, optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of [Formula: see text]Rb D2 transition, which involves the Doppler broadening effect, are solved. The calculated spectra agree well with the experimental results obtained based on the coupling-probe scheme with orthogonal linear polarizations of the coupling and probe fields. The mechanisms of electromagnetically induced absorption (electromagnetically induced transparency) for the open [Formula: see text] and 3 transitions (open [Formula: see text] and 3 transitions) are determined to be the effect of the strong closed [Formula: see text] transition line (strong closed [Formula: see text] transition line); this finding is based on a comparison between the calculated absorption profiles of the DTLS without neighboring states and those of all levels with neighboring states, depending on the coupling and probe power ratios. Furthermore, based on the aforementioned comparison, the crucial factors that enhance or reduce the coherence effects and lead to the transformation between electromagnetically induced absorption and electromagnetically induced transparency, are (1) the power ratios between the coupling and probe beams, (2) the openness of the excited state, and (3) effects of the neighboring states due to Doppler broadening in a real atomic system.
7 citations
TL;DR: In this paper , the authors demonstrate that the spectrum broadening and compression of mid-IR pulses can be adjusted independently through the use of inert and molecular gases, while uniform broadening up to 1-μm bandwidth at the 1/e2 level relies on the proper choice of gas mixture and its compounds partial pressure.
Abstract: Precise control of the nonlinear optical phenomena is the limiting factor for the spectral broadening and pulse compression techniques for high-power laser systems. Here we demonstrate that generation of the blue and red components under filamentation of 4.55-μm mid-IR pulses can be easily adjusted independently through the use of inert and molecular gases, while uniform broadening up to 1-μm bandwidth at the 1/e2 level relies on the proper choice of gas mixture and its compounds partial pressure. Such synthesized media provide a feasible route for the free of damage control of pulse spectral broadening and compression for gigawatt peak power laser systems operating in the mid-IR. Additional management of a generated spectrum can be realized through the adjustment of focusing conditions. The resulted pulse is compressed by a factor of 2.6 down to 62 fs pulse duration (4.1 optical cycles) with additional dispersion compensation. Controllable nonlinear compression down to four optical cycles keeping the millijoule energy level of a mid-IR laser pulse provides direct access to extreme nonlinear optics.
5 citations
01 Jan 2022
TL;DR: Positron annihilation spectroscopy (PAS) is a highly sensitive and promising method of probing the structural defects in solids including nanomaterials as mentioned in this paper , which can be used to investigate the changes in structure and structural defects like vacancies and thereby to probe the related properties.
Abstract: Positron annihilation spectroscopy (PAS) is a highly sensitive and promising method of probing the structural defects in solids including nanomaterials. PAS studies are carried out to obtain information related to the structural defects in materials for the investigation of their suitability of application in various fields of science, technology, and materials engineering. The chapter describes a comprehensive, systematic, and methodical elucidation of fundamentals of positron annihilation lifetime and coincidence Doppler broadening spectroscopic techniques. The chapter explains in detail how PAS is effectively utilized to investigate in detail the changes in structure and structural defects like vacancies and thereby to probe the related properties. The chapter covers the essential gamut of PAS in nanomaterials and serves as a comprehensive reference material for this subject.
5 citations
TL;DR: In this paper , optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of [Formula: see text]Rb D2 transition, which involves the Doppler broadening effect, are solved.
Abstract: In this study, optical Bloch equations with and without neighboring hyperfine states near the degenerate two-level system (DTLS) in the challenging case of [Formula: see text]Rb D2 transition, which involves the Doppler broadening effect, are solved. The calculated spectra agree well with the experimental results obtained based on the coupling-probe scheme with orthogonal linear polarizations of the coupling and probe fields. The mechanisms of electromagnetically induced absorption (electromagnetically induced transparency) for the open [Formula: see text] and 3 transitions (open [Formula: see text] and 3 transitions) are determined to be the effect of the strong closed [Formula: see text] transition line (strong closed [Formula: see text] transition line); this finding is based on a comparison between the calculated absorption profiles of the DTLS without neighboring states and those of all levels with neighboring states, depending on the coupling and probe power ratios. Furthermore, based on the aforementioned comparison, the crucial factors that enhance or reduce the coherence effects and lead to the transformation between electromagnetically induced absorption and electromagnetically induced transparency, are (1) the power ratios between the coupling and probe beams, (2) the openness of the excited state, and (3) effects of the neighboring states due to Doppler broadening in a real atomic system.
5 citations
TL;DR: In this paper , the authors investigated the transformation of free volume extended defects in selected chalcogenide glasses caused by thermal annealing for 10, 25, and 50'h.
Abstract: Herein, transformation of free‐volume extended defects in selected chalcogenide glasses caused by thermal annealing for 10, 25, and 50 h is studied. For 80GeSe2–20Ga2Se3 as well as for GeS2–Ga2S3 glasses with different GeS2 and Ga2S3 contents (80GeS2–20Ga2S3, 82GeS2–18Ga2S3, 84GeS2–16Ga2S3), positron annihilation lifetime spectroscopy and Doppler broadening of annihilation radiation methods are applied. By analyzing the positron annihilation lifetime spectra decomposed into two components, it is shown that the observed changes in the second defect‐related component for the 80GeSe2–20Ga2Se3 glasses confirm the agglomeration of free volumes in the initial stage of annealing (10 h) with further fragmentation (25 h) and shrinkage (50 h). Increased content of Ge‐related subsystem in the GeS2–Ga2S3‐based glasses results in the agglomeration of free‐volume defects in the 82GeS2–18Ga2S3 glasses with their further expansion in the 84GeS2–16Ga2S3 matrix.
5 citations
TL;DR: In this article , Positron annihilation Doppler Broadening spectroscopy was implemented to investigate damage due to 1 MeV Kr-ion irradiation of UO2 and 3 MeV Au irradiation, and lanthanide-doped versions of these materials.
Abstract: Nuclear fuels containing uranium oxide, plus fission and activation products, will continue to undergo radioactive decay and also fission after removal from the reactor. These nuclear materials will undergo exposure to heat and persistent irradiation by alpha particles and neutrons. Vacancies and larger open volume defects, sometimes filled by helium, may be created and lead to swelling. Positron annihilation Doppler Broadening spectroscopy was implemented to investigate damage due to 1 MeV Kr-ion irradiation of UO2 and 3 MeV Au irradiation of CeO2 (a surrogate for UO2) and lanthanide-doped versions of these materials. Contrary to expectation, significant differences arose due to the doping atoms. In UO2, the doping atom type resulted in varying concentrations of the same type of defect. In CeO2, the defect type and concentration changed due to irradiation of differently doped material. Comparison of TRIM calculations to positron annihilation spectroscopy Doppler Broadening (PAS-DB) data vacancy signal S (both left axis) and PAS-DB of irradiated CeO2 (right axis). The UO2 sample was irradiated with 1 MeV Kr ions and the CeO2 sample with 3 MeV Au ions. The solid lines are the simulation of positron data (grey for UO2 from two differently prepared samples and green for CeO2) based on best fits of simple damage profiles (red). The damage profile assumes stacks of layers with constant damage. In UO2, the best fit damage shows layers of decreasing defect concentration (red). In contrast, in CeO2, the damage is low near the surface and rises. These differences may have implications for the use of CeO2 as simple non-radioactive analogue of UO2-based nuclear fuels.
4 citations
TL;DR: In this article , the authors examined the spectral broadening process caused by the combination of the discrete transition peaks induced by the crystal field effect and electron-phonon coupling widening based on Yb:Lu x Sc 2-x O 3 crystals.
Abstract: Over the past decades, Yb 3+ -doped cubic sesquioxide crystals have been considered as ideal gain materials for ultrafast laser generation, owing to their high thermal conductivity and adequate optical characteristics. The broadening of spectra by mixing host crystals to obtain short pulses has been extensively explored; however, few studies have examined the mechanism of the crystal field effect on spectral broadening. This paper describes the spectral broadening process caused by the combination of the discrete transition peaks induced by the crystal field effect and electron-phonon coupling widening based on Yb:Lu x Sc 2-x O 3 crystals. The energy level splitting induced by the crystal field effect not only determines the emission peak positions, but also broadens the emission spectra in the mixed host materials through the increasing spin-orbit coupling effect. Moreover, with the involvement of the electron-phonon coupling and the crystal field effect, the spectral broadening is much more obvious at room temperature. These results not only explain the spectral broadening mechanism of Yb 3+ -doped sesquioxides but also provide important insights for the improvement of new ultrafast laser materials.
4 citations
TL;DR: In this article , a nonlinear multipass cell with a bulk medium was used to compress 250-fs pulses down to 38 fs, and the same input pulses created a sufficient bandwidth for sub-20-fs pulse generation in a multi-cell with gaseous media.
Abstract: Multipass spectral broadening and compression around 515 nm are experimentally demonstrated. A nonlinear multipass cell with a bulk medium is used to compress 250-fs pulses down to 38 fs. The same input pulses create a sufficient bandwidth for sub-20-fs pulse generation in a multipass cell with gaseous media. In both cases, the efficiency exceeds 85%. Dispersion management by reduction of the cell size and the thickness of the nonlinear medium allows an efficient generation of ultrashort pulses in the visible range and establishes a pathway for ultraviolet spectral broadening by means of multipass cells.
4 citations
TL;DR: In this article , a comparison of TRIM calculations to positron annihilation spectroscopy Doppler Broadening (PASDB) data vacancy signal S (both left axis) and PAS-DB of irradiated CeO_2 (right axis).
Abstract: Nuclear fuels containing uranium oxide, plus fission and activation products, will continue to undergo radioactive decay and also fission after removal from the reactor. These nuclear materials will undergo exposure to heat and persistent irradiation by alpha particles and neutrons. Vacancies and larger open volume defects, sometimes filled by helium, may be created and lead to swelling. Positron annihilation Doppler Broadening spectroscopy was implemented to investigate damage due to 1 MeV Kr-ion irradiation of UO_2 and 3 MeV Au irradiation of CeO_2 (a surrogate for UO_2) and lanthanide-doped versions of these materials. Contrary to expectation, significant differences arose due to the doping atoms. In UO_2, the doping atom type resulted in varying concentrations of the same type of defect. In CeO_2, the defect type and concentration changed due to irradiation of differently doped material. Graphical abstract Comparison of TRIM calculations to positron annihilation spectroscopy Doppler Broadening (PAS-DB) data vacancy signal S (both left axis) and PAS-DB of irradiated CeO_2 (right axis). The UO_2 sample was irradiated with 1 MeV Kr ions and the CeO_2 sample with 3 MeV Au ions. The solid lines are the simulation of positron data (grey for UO_2 from two differently prepared samples and green for CeO_2) based on best fits of simple damage profiles (red). The damage profile assumes stacks of layers with constant damage. In UO_2, the best fit damage shows layers of decreasing defect concentration (red). In contrast, in CeO_2, the damage is low near the surface and rises. These differences may have implications for the use of CeO_2 as simple non-radioactive analogue of UO_2-based nuclear fuels.
4 citations
TL;DR: In this article , a Si3N4 waveguide was used to perform coherent spectral broadening using pulses in the picosecond regime with high repetition rate, which enables the generation of a coherent octave spanning spectrum.
Abstract: Spectral broadening of optical frequency combs with high repetition rate is of significant interest in optical communications, radio-frequency photonics and spectroscopy. Silicon nitride waveguides (Si3N4) in the anomalous dispersion region have shown efficient supercontinuum generation spanning an octave-bandwidth. However, the broadening mechanism in this regime is usually attained with femtosecond pulses in order to maintain the coherence. Supercontinuum generation in the normal dispersion regime is more prone to longer (ps) pulses, but the implementation in normal dispersion silicon nitride waveguides is challenging as it possesses strong requirements in propagation length and losses. Here, we experimentally demonstrate the use of a Si3N4 waveguide to perform coherent spectral broadening using pulses in the picosecond regime with high repetition rate. Moreover, our work explores the formation of optical wave breaking using a higher energy pulse which enables the generation of a coherent octave spanning spectrum. These results offer a new prospect for coherent broadening using long duration pulses and replacing bulky optical components.
TL;DR: In this paper , the authors achieved a negative refractive index with significantly reduced absorption in a three-level Λ-type atomic gas medium under Doppler broadening, where the coupling laser intensity must be approximately ten times greater than that when the broadening is ignored.
Abstract: We have achieved a negative refractive index with significantly reduced absorption in a three-level Λ-type atomic gas medium under Doppler broadening. It shows that the conditions for obtaining negative refractive index in the presence of Doppler broadening are very different from those of Doppler broadening absent. In particular, in order to obtain negative refractive index in the case of Doppler broadening the coupling laser intensity must be approximately ten times greater than that when the Doppler broadening is ignored. Meanwhile, the frequency band of negative refractive index with Doppler broadening is significantly expanded (about a hundred times) compared to that without Doppler broadening, however, the amplitude of negative refractive index decreases with increasing temperature (or Doppler width). Even in some cases as temperature (Doppler width) increases, the left-handedness of the material can disappear. In addition, we also show that the amplitude and the frequency band of negative refractive index can be changed by adjusting the intensity and the frequency of coupling laser. Our theoretical investigation can be useful for selection of laser parameters under different temperature conditions to achieve negative refractive index in experimental implementation.
TL;DR: In this article , the positron annihilation in tungsten lattice and in vacancy-type defects using state-of-the-art first principles methodology are calculated with two-component density functional theory with local density approximation and weighted density approximation.
TL;DR: In this paper , the evolution of vacancies in P92 alloy was investigated using slow positron beam Doppler broadening spectroscopy, and it was shown that the migration of vacancies hindered by C atoms is mainly related to carbon-vacancy complexes in the P92 Alloy at approximately 300°C.
TL;DR: In this paper , an analytical model for cross-Kerr nonlinear coefficient in a four-level N-type atomic medium under Doppler broadening was presented, and the model was applied to 87 Rb atoms to analyze the dependence of the nonlinear coefficients on the external light field and the temperature of atomic vapor.
Abstract: We present an analytical model for cross-Kerr nonlinear coefficient in a four-level N-type atomic medium under Doppler broadening. The model is applied to 87 Rb atoms to analyze the dependence of the cross-Kerr nonlinear coefficient on the external light field and the temperature of atomic vapor. The analysis shows that in the absence of electromagnetically induced transparency (EIT) the cross-Kerr nonlinear coefficient is zero, but it is significantly enhanced when the EIT is established. It means that the cross-Kerr effect can be turned on/off when the external light field is on or off. Simultaneously, the amplitude and the sign of the cross-Kerr nonlinear coefficient are easily changed according to the intensity and frequency of the external light field. The amplitude of the cross-Kerr nonlinear coefficient remarkably decreases when the temperature of atomic medium increases. The analytical model can be convenient to fit experimental observations and applied to photonic devices.
TL;DR: In this paper , the authors presented a new method for obtaining an analytical solution for the Kaniadakis Doppler broadening (KDB) function, and reported the computational efficiencies of this solution compared with the numerical one.
TL;DR: In this paper , Positron Annihilation Doppler Broadening Spectroscopy (PADBS) was used to analyse the origin and development of defect processes in porous silicon structures.
Abstract: Abstract Here we present Positron Annihilation Doppler Broadening Spectroscopy (PADBS) as a powerful method to analyse the origin and development of defect processes in porous silicon structures as a result of alloying with lithium for the use in battery anode applications. Several prepared anodes were lithiated (discharged against Li + /Li) and de-lithiated (charged) with different capacities followed by a distinct treatment procedure and an analysis using the Delft Variable Energy Positron Beam. The results presented here show that we can distinguish two different processes attributed to (1) structural changes in silicon as a result of the alloying process, and (2) the formation of defects that initiate degradation of the material. The limit at which the porous material can be used for at least the first two cycles without the occurrence of damage can thus be accurately determined by using the PADBS technique.
TL;DR: In this article, the authors extended the self-phase modulation model from X-rays to DC using extreme intensity femtosecond laser pulses in the four states of matter: gases, liquids, solids, and plasmas.
TL;DR: In this article, the impact of broadening fiber, dynamic switching between different harmonic modes and the influence of laser polarization on the properties of the generated supercontinuum is studied for three different kinds of telecommunication fibre.
Abstract: The application of a recently demonstrated mode-locked ultralong pulsed fibre ring laser architecture (Gallazzi et al., 2021) to the inexpensive and efficient generation of supercontinuum from a pulsed output at 1.56 μ m in standard single-mode telecommunication fibre is experimentally demonstrated. The impact of broadening fibre, dynamic switching between different harmonic modes and the influence of laser polarization on the properties of the generated supercontinuum are studied for three different kinds of telecommunication fibre. Flexible spectral broadening beyond 200 nm is obtained with good temporal correlation and pulse compression from 240 fs down to 50 fs.
TL;DR: In this article , a spectroscopic line shape analysis for several species in the divertor scrape-off-layer of the stellarator Wendelstein 7-X (W7-X) was performed.
Abstract: Impurity temperatures have been determined by a spectroscopic line shape analysis for several species in the divertor scrape-off-layer of the stellarator Wendelstein 7-X (W7-X). Examples include spectral lines from intrinsic elements (C II and C III, He I) as well as from seeded impurities (Ar II, N II) through the divertor gas inlet system. Both Doppler broadening and Zeeman splitting are found to contribute significantly to the impurity line shapes. Zeeman splitting arises due to the confining magnetic field in W7-X and complicates the line shape appearance. By attributing Doppler widths to each of the various Zeeman components, however, we demonstrate that reliable ion temperature values can be derived provided that the presence of the magnetic field is properly accounted for. The spectrally highly resolved lines are analyzed by means of a multi-parameter, least-squares fit routine, which accounts for Doppler broadening, Zeeman splitting, as well as the instrumental broadening of the spectrometer used to measure the spectral line shapes. By spectral fitting of the Zeeman features, it is also found that the line shape analysis can yield values for the local magnetic field, which can be used to localize the impurity radiation approximately provided that the line emission is dominant in a small area intersected by the lines of sight of the spectrometer.
TL;DR: Positron beam-based Doppler broadening results on He ion-implanted FeCrCoNi show distinct changes in defect-sensitive S-parameter corresponding to the formation of helium-vacancy complexes, nucleation/ growth of helium bubbles, and finally the helium bubble rupture, with isochronal annealing as discussed by the authors .
TL;DR: In this paper , the authors extended the self-phase modulation model from X-rays to DC using extreme intensity femtosecond laser pulses in the four states of matter: gases, liquids, solids, and plasmas.
TL;DR: In this paper , the effects of neighboring transitions through Doppler broadening on the electromagnetic induced absorption and electromagnetically induced transparency (EIT) of the degenerate two-level system (DTLS) in 85Rb atoms with respect to the linear parallel polarization configuration of coupling and probe lasers have been investigated.
TL;DR: In this article , the authors simulate experimental conditions for nonlinear spectral broadening and compression of multi-joule, sub-picosecond, and femtosecond laser systems focusing on 1'm center wavelength.
Abstract: We simulate experimental conditions for nonlinear spectral broadening and compression of multi-joule, sub-picosecond, and femtosecond laser systems focusing on 1 μm center wavelength. The spatial, spectral, and temporal properties of two distinct cases are investigated in detail. The first system is a short multi-pass cell with 0.1–0.5 J pulse energy operated at higher helium pressures, used to illustrate the transition between Kerr-effect induced spectral broadening and spectral broadening in plasma. The second case is a long ten-joule multi-pass cell operated at few Pascal pressure range. These examples cover the operational extent of plasma spectral broadening in a multi-pass cell. Effects pertaining to plasma spectral broadening, including imperfect spatial beam profiles and initial non-zero nonlinear phase, are investigated, as well as scalability.
TL;DR: In this article , the authors discussed the energy dissipation of short-lived para-positronium (p-Ps) in polymers and silica glass, and determined the S parameter characterizing the Doppler broadening of p-Ps annihilation.
Abstract: In this letter we discuss the energy dissipation of short-lived para-positronium (p-Ps) in polymers and silica glass. The S parameter characterizing the Doppler broadening of p-Ps annihilation is determined from the previously reported systematic data of positron annihilation age momentum correlation for various polymers and silica glass. A comparison of the S parameter with that expected for thermalized p-Ps trapped in a free volume reveals that p-Ps is not thermalized and possesses excess energy in fluorinated polymers and silica glass, indicating that it is difficult for Ps to lose energy in substances containing heavy elements such as fluorine and silicon.
TL;DR: In this article , a krypton-filled Herriott-type cavity employing metallic mirrors is used for spectral broadening, which enables the efficient post compression of the pulses emitted by an ultrafast coherently combined thulium-doped fiber laser system.
Abstract: We report on the generation of GW-class peak power, 35-fs pulses at 2-µm wavelength with an average power of 51 W at 300-kHz repetition rate. A compact, krypton-filled Herriott-type cavity employing metallic mirrors is used for spectral broadening. This multi-pass compression stage enables the efficient post compression of the pulses emitted by an ultrafast coherently combined thulium-doped fiber laser system. The presented results demonstrate an excellent preservation of the input beam quality in combination with a power transmission as high as 80%. These results show that multi-pass cell based post-compression is an attractive alternative to nonlinear spectral broadening in fibers, which is commonly employed for thulium-doped and other mid-infrared ultrafast laser systems. Particularly, the average power scalability and the potential to achieve few-cycle pulse durations make this scheme highly attractive.
TL;DR: In this paper , the spectrum observation of the rotational Doppler effect based on the coherent interaction between atoms and structured light in an atomic vapor is realized, and the geometric phase and polarization of the structured beam are generated and manipulated by using a flexible and efficacious combination optical elements, converting an initial linearly polarized Gaussian beam into a phase vortex beam or an asymmetric or symmetric vector beam.
Abstract: A vector beam with the spatial variation polarization has attracted keen interest and is progressively applied in quantum information, quantum communication, precision measurement, and so on. In this letter, the spectrum observation of the rotational Doppler effect based on the coherent interaction between atoms and structured light in an atomic vapor is realized. The geometric phase and polarization of the structured beam are generated and manipulated by using a flexible and efficacious combination optical elements, converting an initial linearly polarized Gaussian beam into a phase vortex beam or an asymmetric or symmetric vector beam. These three representative types of structured beam independently interact with atoms under a longitudinal magnetic field to explore the rotational Doppler shift associated with the topological charge. We find that the rotational Doppler broadening increases obviously with the topological charge of the asymmetric and symmetric vector beam. There is no rotational Doppler broadening observed from the spectrum of the phase vortex beam, although the topological charge, and spatial profile of the beam change. This study can be applied to estimate the rotational velocity of the atom-level or molecule-level objects, measure the intensity of magnetic fields and study the quantum coherence in atomic ensembles.
TL;DR: In this paper , the DCT-DB Doppler broadening method was proposed and validated using the ENDF/B-VIII.0 data library, where the authors used a discrete cosine transform (DCT) to solve the problem.
01 Jul 2022
TL;DR: In this article , the relativistic and non-relativistic Doppler effects on spectral line profiles in ultra-hot plasmas in a laboratory system were compared.
Abstract: Abstract In this work, we present a comparative study between the relativistic and non-relativistic Doppler effects on spectral line profiles in ultra-hot plasmas in a laboratory system. We have established an exact formula of the relativistic Doppler profile in ultra-high-temperature plasma that is not a Gaussian one (unlike the non-relativistic Doppler profile that is Gaussian). We have also derived a new FWHM (Full Width at Half Maximum) formula of the corresponding profile that is different from the non-relativistic FWHM ( ). We have also shown that, in the relativistic case, Doppler broadening exhibits an asymmetry of spectral line profile (non-Gaussian profile). To ensure the validity of our investigation, we have compared our theoretical calculation with the experimental results and found a good agreement.