Raman Laser Research Articles

Raman laser induced self-organization with topology in a dipolar condensate.

We investigate the ground states of a dipolar Bose-Einstein condensate (BEC) subject to Raman laser induced spin-orbit coupling with mean-field theory. Owing to the interplay between spin-orbit coupling and atom-atom interactions, the BEC presents remarkable self-organization behavior and thus hosts various exotic phases including vortex with discrete rotational symmetry, stripe with spin helix, and chiral lattices with C4 symmetry. The peculiar chiral self-organized array of square lattice, which spontaneously breaks both U(1) and rotational symmetries, is observed when the contact interaction is considerable in comparison with the spin-orbit coupling. Moreover, we show that the Raman-induced spin-orbit coupling plays a crucial role in forming rich topological spin textures of the chiral self-organized phases by introducing a channel for atoms to turn on spin flipping between two components. The self-organization phenomena predicted here feature topology owing to spin-orbit coupling. In addition, we find long-lived metastable self-organized arrays with C6 symmetry in the case of strong spin-orbit coupling. We also present a proposal to observe these predicted phases in ultracold atomic dipolar gases with laser-induced spin-orbit coupling, which may stimulate broad theoretical as well as experimental interest.

Improving the fringe contrast in an atomic gravimeter by optimizing the Raman laser intensity

As the expansion of the atomic cloud’s diameter relative to the Gaussian Raman beam in an atom interferometer, the interaction between them would be reduced. Such an effect can decrease the effective Rabi frequency and lower the state transfer efficiency of the Raman laser, which finally reduces the fringe contrast and the sensitivity of the atom interferometer. In this work, we demonstrate experimentally that the fringe contrast can be improved by optimizing the laser intensities of three Raman pulses, and find that the criterion for the optimized Raman laser intensities should be the Raman pulse efficiency rather than the Rabi frequency. In the case of an atomic gravimeter, our method obtains an obvious enhancement of the fringe contrast when T > 60 ms and the maximum contrast enhancement is ∼5.1% (from 25.3% to 26.6%) at T = 120 ms. These results could be beneficial for atom-interferometer-based inertial sensors, including but not limited to the atomic gravimeter, gravity gradiometer and gyroscope.

Broadband 2D n × n Vortex Arrays Generated from an Efficient Petal‐Like Raman Laser with an Astigmatic Mode Convertor

Broadband vortex arrays distributed in 2D n × n vortices are extremely needed for multiple microparticle manipulation, high‐capacity optical communication, and quantum information. Vortex arrays are usually generated with spatial light modulators, metamaterials; it is a big challenge to improve beam quality and output power. Herein, crisscross 2D n × n vortex arrays are converted from petal‐like Raman lasers with an astigmatic mode convertor. Efficient petal‐like lasers in the form of the Laguerre–Gaussian mode with zero radial index and l azimuthal index (LG0,l ) are irradiated in a Raman microchip laser (RML) by adjusting optimal beam waist and locating the position of focus spot of the annular pump beam. High‐beam‐quality LG0,9 petal‐like Raman laser oscillating at broadband wavelength (bandwidth: 16.2 nm) is generated with power of 773 mW and an efficiency of 10.6%. The conversion efficiency from petal‐like laser to crisscross vortex array is as high as 90%. The vortex array with 5 × 5 vortices operating around 1078 nm is generated with a power of 693 mW and an optical efficiency of 9.5%. Taking advantages of the broad emission spectrum of ytterbium‐doped laser materials and stimulated Raman scattering effect, RMLs are potential sources for generating flexible vortex arrays with desired 2D n × n vortices oscillating in Raman wavelengths.

Signatures of Chemical Dopants in Simulated Resonance Raman Spectroscopy of Carbon Nanotubes.

Single-walled carbon nanotubes (SWCNTs) with organic sp2 or sp3 hybridization defects allow the robust tunability of many optoelectronic properties in these topologically interesting quasi-one-dimensional materials. Recent resonant Raman experiments have illuminated new features in the intermediate-frequency region upon functionalization that change with the degree of functionalization as well as with interactions between defect sites. In this Letter, we report ab initio simulated near-resonant Raman spectroscopy results for pristine and chemically functionalized SWCNT models and find new features concomitant with experimental observations. We are able to assign the character of these features by varying the frequency of the external Raman laser frequency near the defect-induced E11* optical transition using a perturbative treatment of the electronic structure of the system. The obtained insights establish relationships between the nanotube atomistic structure and Raman spectra facilitating further exploration of SWCNTs with tunable optical properties tuned by chemical functionalization.

Numerical modeling of continuous wave intracavity self-Raman lasers considering the influence of the thermal effect

A space-dependent theoretical model is developed to study the influence of the thermal effect on the characteristics of self-Raman lasers. The performances of the Raman laser are well researched by solving rate equations numerically. The simulation results show that the performance of the Raman laser can be improved by narrowing the linewidth of the fundamental field and using an output coupler with optimum transmission for 880 nm and 914 nm pump wavelengths. Also, cooling the temperature of the crystal for the 880 nm pump wavelength and heating the crystal temperature appropriately for the 914 nm pump wavelength are promising routes to further improve the Raman power.

Modelling light wave propagation and interaction and dynamical regimes analysis using the Lyapunov exponents method in ring fibre cavities

The ‘Cabaret’ finite differences method allows the performance of fast and conclusive modelling of the microcavity temporal dynamics with group velocity dispersion, cross- and self- phase modulation included. The proposed scheme and model allow us to study the dynamics of a cavity with two counter-propagating pulses, second order dispersion, modulation instability, Rayleigh scattering and other effects along the cavity roundtrips number up to 106…7. The possibility of Lyapunov exponents mapping for the Raman and SBS fibre lasers and cavities is discussed.

Picosecond random Raman lasing in the spectral range of 360–630 nm using powders of potassium, sodium and strontium nitrates

Stimulated Raman scattering (SRS) of picosecond laser radiation at 532 and 355 nm in microcrystalline powders of potassium, sodium, and strontium nitrates has been studied. One anti-Stokes and three Stokes components were generated in all samples when pumping at 532 nm. For the first time to our knowledge, random Raman lasing in the used nitrates has been obtained upon their excitation at 355 nm. In this case, the multifrequency Stokes SRS is also observed in all nitrates. We have analyzed all possible loss channels when ultraviolet radiation is used for excitation of SRS. In general, picosecond random SRS generation has been obtained at 19 spectral lines in the spectral range of 360–630 nm. In all cases, the SRS process is due to the internal symmetric mode of the (NO3)− ion with the frequency shifts of 1050 cm−1 (KNO3), 1069 cm−1 (NaNO3), and 1057 cm−1 (Sr(NO3)2).

Raman-IR spectroscopic, and XRD analysis of selected samples from Fogo Island, Cabo Verde: Implications for ancient Martian volcanology

Several space missions from NASA, and ESA have visited and will land on Mars in the search for life. The last mission to arrive was the Mars 2020 Perseverance rover on 18 February 2021. The next mission to Mars will be ExoMars Rosalind Franklin rover, expected to touch down sometime after 2028. Both Mars2020 and ExoMars are equipped with Raman spectroscopic systems: SuperCam and SHERLOC on Perseverance, and Raman Laser Spectrometer (RLS) on Rosalind Franklin (RF). These instruments will be tasked with identifying rocks, minerals, and potential organic biosignatures on the Martian surface. There are many challenges associated with the qualitative and quantitative analysis of resulting data received from current missions on Mars. It is our belief that studies of new terrestrial Martian analogues can help to overcome these challenges. Here, we introduce Chã das Caldeiras Outcrop, Fogo Island, Cabo Verde as a new volcanic terrestrial analog for Mars. We sampled several areas of relevance in Chã das Caldeiras and conducted a complete band analysis of Raman spectra for targets from this site. Additional analyses included ATR-FTIR and XRD. We detected several pyroxene types (augite and diopside) and plagioclase feldspar species (orthoclase, bytownite, sanidine, albite, and anorthite), olivine (forsterite), oxides (magnetite), and leucite. The alteration and secondary minerals detected were carbonates (calcite and dolomite), oxides (goethite, anatase, and hematite), spinel (chromite), phosphate (apatite), various clays, and zeolites (chabazite and muscovite and analcime). We present the Chã das Caldeiras site as a possible new volcanic analogue for Mars given: 1) the similarities to other volcanic places in the Canary Islands; 2) the exclusive geological evolution that is only present in the volcanic emplacement from the Macaronecia-group; 3) the pristine quality of the samples from the outcrop as well as the alteration volcanic minerals.

Spectrum multiplexing of multiwavelength picosecond oscillation of synchronously pumped Raman laser based on a Sr(MoO_4)-=SUB=-0.8-=/SUB=-(WO_4)-=SUB=-0.2-=/SUB=- crystal

For the first time to our knowledge, a single-phase solid solution Sr(MoO_4)0.8(WO_4)0.2 was used as an active medium of a Raman laser. Using the high-intensity synchronous picosecond pumping satisfying the condition of phase capture of the parametric Raman interaction on the second vibrational mode made it possible to oscillate six components of Raman radiation with a combined frequency shift on the first (888 cm-1) and second (327 cm-1) vibrational modes in the wavelength range of 1194-1396 nm. Oscillation efficiency of the multiwavelength Raman laser radiation was as high as 10%. By detuning the Raman laser cavity length, the pulse shortening down to 6 ps for the Raman laser radiation components with the combined frequency shift was obtained, which is an order of magnitude shorter than the pumping pulse duration (64 ps). Keywords: stimulated Raman scattering, single-phase solid solution, vibrational mode, synchronous pumping.

Обогащение спектра многоволновой пикосекундной генерации синхронно-накачиваемого ВКР-лазера на кристалле Sr(MoO_4)-=SUB=-0.8-=/SUB=-(WO_4)-=SUB=-0.2-=/SUB=-

For the first time to our knowledge, a single-phase solid solution Sr(MoO4)0.8(WO4)0.2 was used as an active medium of a Raman laser. Using the high-intensity synchronous picosecond pumping satisfying the condition of phase capture of the parametric Raman interaction on the second vibrational mode made it possible to oscillate six components of Raman radiation with a combined frequency shift on the first (888 cm–1) and second (327 cm–1) vibrational modes in the wavelength range of 1194-1396 nm. Oscillation efficiency of the multiwavelength Raman laser radiation was as high as 10%. By detuning the Raman laser cavity length, the pulse shortening down to 6 ps for the Raman laser radiation components with the combined frequency shift was obtained, which is an order of magnitude shorter than the pumping pulse duration (64 ps).

High-power free-running single-longitudinal-mode diamond Raman laser enabled by suppressing parasitic stimulated Brillouin scattering

Abstract A continuous-wave (CW) single-longitudinal-mode (SLM) Raman laser at 1240 nm with power of up to 20.6 W was demonstrated in a free-running diamond Raman oscillator without any axial-mode selection elements. The SLM operation was achieved due to the spatial-hole-burning free nature of Raman gain and was maintained at the highest available pump power by suppressing the parasitic stimulated Brillouin scattering (SBS). A folded-cavity design was employed for reducing the perturbing effect of resonances at the pump frequency. At a pump power of 69 W, the maximum Stokes output reached 20.6 W, corresponding to a 30% optical-to-optical conversion efficiency from 1064 to 1240 nm. The result shows that parasitic SBS is the main physical process disturbing the SLM operation of Raman oscillator at higher power. In addition, for the first time, the spectral linewidth of a CW SLM diamond Raman laser was resolved using the long-delayed self-heterodyne interferometric method, which is 105 kHz at 20 W.

Dielectric studies of BaxPb1−x(NO3)2 single crystals for optoelectronic applications

The study described above involves growing a series of mixed crystals of BaxPb1−x(NO3)2 with different initial Ba+2/Pb+2 ratios (x = 0 to 1), and analyzing their behavior in an applied electric field by measuring the dielectric constant (ε) and dielectric loss (tan δ) at different frequencies and temperatures. The results of the study show that the behavior of the mixed crystals varies depending on their composition, with both positive and negative deviations from linearity observed in the dielectric constant and dielectric loss. This non-linear behavior may have implications for the use of these nitrate crystals in various applications, including Stimulated Raman Scattering, lasers, and medical, spectroscopy, defense, and research devices. Overall, this study provides important insights into the behavior of BaxPb1−x(NO3)2 mixed crystals under an applied electric field, and highlights their potential applications in various fields of science and technology.

A 110 W fiber gas Raman laser at 1153 nm

AbstractWe report here the first hundred-watt continuous wave fiber gas laser in H2-filled hollow-core photonic crystal fiber (PCF) by stimulated Raman scattering. The pump source is a homemade narrow-linewidth fiber oscillator with a 3 dB linewidth of 0.15 nm at the maximum output power of 380 W. To efficiently and stably couple several-hundred-watt pump power into the hollow core and seal the gas, a hollow-core fiber end-cap is fabricated and used at the input end. A maximum power of 110 W at 1153 nm is obtained in a 5 m long hollow-core PCF filled with 36 bar H2, and the conversion efficiency of the first Stokes power is around 48.9%. This work paves the way for high-power fiber gas Raman lasers.

Multi-wavelength red diamond Raman laser

Multi-wavelength red diamond Raman laser

Numerical simulation of thermal effects in high-power diamond Raman lasers

Numerical simulation of thermal effects in high-power diamond Raman lasers

Generated Raman Laser Tem10 Mode at the Air-Heavy Water Interface by Stimulated Raman Scattering

Generated Raman Laser Tem10 Mode at the Air-Heavy Water Interface by Stimulated Raman Scattering

End-pumped Nd:YAG/Cr4+:YAG/KTA passive Q-switched cascade Raman laser

End-pumped Nd:YAG/Cr4+:YAG/KTA passive Q-switched cascade Raman laser

Progress on mid-infrared glass optical fiber materials and Raman laser source (invited)

Progress on mid-infrared glass optical fiber materials and Raman laser source (invited)

Experimental study on CCD damage by multi-wavelength Raman lasers

Experimental study on CCD damage by multi-wavelength Raman lasers

Intra-Cavity Raman Laser Operating at 1193 nm Based on Graded-Index Fiber

Nonlinear Raman frequency conversion is an important technical scheme to obtain special optical band lasers based on conventional ion-doped lasers. In our work, we designed an intra-cavity Raman fiber laser based on graded index fiber (GRIF) as the Raman gain medium. Based on the fundamental-frequency 1080-nanometer laser, efficient first-order and second-order Stokes Raman lasers were obtained, respectively. When the power of the fundamental-frequency 1080-nanometer laser was 33.4 W, the output power of the second-order 1193-nanometer laser was 11.39 W. The corresponding conversion efficiency was 34.1%. To our knowledge, this is the first report of a second-order Raman output based on a GRIF and intra-cavity structure. In the experiment, the spectrum-purification process with the increase in power was also observed. Our experimental results prove that the intracavity Raman-laser system based on graded index fiber with a high optical conversion efficiency has important application potential for obtaining new special-application bands.