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The 2021 Physics Nobel Prize was awarded to Syukuro Manabe, Klaus Hasselmann, and Giorgio Parisi for their “groundbreaking contributions to our understanding of complex physical systems.” Here we review some of the ideas and results which served as the scientific basis to the award. We also comment on the works by our research group on the complex systems properties of random lasers and random fiber lasers.

As changes in hard or soft oral tissues normally have a microbiological component, it is important to develop diagnostic techniques that support clinical evaluation, without destroying microbiological formation. The optical coherence tomography (OCT) represents an alternative to analyze tissues and microorganisms without the need for processing. This imaging technique could be defined as a fast, real-time, in situ, and non-destructive method. Thus, this study proposed the use of the OCT to visualize biofilm by Candida albicans in reline resins for removable prostheses. Three reline resins (Silagum-Comfort, Coe-Comfort, and Soft-Confort), with distinct characteristics related to water sorption and fungal inhibition were used. A total of 30 samples (10 for each resin group) were subjected to OCT scanning before and 96 h after inoculation with Candida albicans (URM 6547). The biofilm analysis was carried out through a 2D optical Callisto SD-OCT (930 nm) operated in the spectral domain. Then, the images were preprocessed using a [Formula: see text] Gaussian filter to remove the noise, and then Otsu binarization, allowing segmentation and pixel counting. The layer’s biofilm formed was clearly defined and, indeed, its visualization is modified by water sorption of each material. Silagum-Comfort and Soft-Confort showed some similarities in the scattering of light between the clean and inoculated samples, in which, the latter samples presented higher values of light signal intensity. Coe-Comfort samples were the only ones that showed no differences between the clean or inoculated images. Therefore, the results of this study suggest that OCT is a viable technique to visualize the biofilm in reline materials. Because findings in the literature are still scarcely using the OCT technique to visualize biofilm in reline resins, further studies are encouraged. It should not contain any references or displayed equations.

Temperature determination is of fundamental importance for a wide variety of applications in scientific research, technological developments, biomedical applications, and control of many industrial processes. To supply all these needs, a variety of sensors and devices using different methods have been developed. In this work, we propose a new alternative for a luminescent thermometer based on the visible emission of the europium ion (Eu3+) in the Y2O3 matrix. The sharp emission peak observed at 612 nm was achieved by exciting the Y2O3:Eu3+ ceramic powders with a broadband LED light source centered at 395 nm. The temperature-sensing behavior was explored based on the valley-to-peak ratio (VPR) approach. Thermal sensing performance based on red-emitting level (5D0 → 7F2) as a function of the temperature, in the range of 298–573 K, has been considered to evaluate the thermometric parameters. The evaluated thermal sensitivity in Y2O3:Eu3+ is around 0.53% K−1 at 298 K in our experimental range. Results imply that the present phosphor Y2O3:Eu3+ exhibits high and stable sensitivity in a wide temperature range. Hence, this work demonstrates the basis for the manufacture of thermometer of low cost, using simple commercial LED as a source of excitation.

Atomically thin 2D materials, currently being at the forefront of scientific and technological interest, can be categorized as metallic, semimetallic, semiconducting, insulating, or superconducting...

This study aimed to investigate the influence of Nd:YAG laser and aluminum oxide sandblasting on the shear bond strength (SBS) of lingual brackets and to optically analyze the behavior of the enamel morphology. Thirty-five bovines’ incisors teeth were divided into 5 groups (n = 7), according to the surface preconditioning: G1, control group; G2, Nd:YAG laser; G3, laser + aluminum oxide sandblasting (Al2O3); G4, Al2O3; and G5, Al2O3 + laser. All groups had lingual brackets bonded and shear debonded after 72 h. SBS values were analyzed, and the enamel morphology was evaluated by optical coherence tomography (OCT) and scanning electron microscope (SEM), before and after preconditioning surface. The optical attenuation coefficient (α) analysis was obtained from OCT images. Data analysis used the ANOVA test, followed by post hoc Tukey, Kruskal Wallis, and post hoc Dunn tests (significance of 5%). The SBS values presented similarly among groups, but the value of α showed statistical difference (p-value = 0.0124) between G3 and G5 with the others. Optical analyses indicated a melting on the enamel that suffered laser irradiation for G2 and G5 and crystal surface disorganization for G4. Sandblasting partially removes the melting of the laser effect (G3). The sandblasting is a dispensable step for bonding lingual brackets, and the melting of the enamel after laser irradiation does not compromise the bracket adhesive resistance. The Nd:YAG laser became an interesting tool to prevent caries and decrease prevalence of white spot lesions in orthodontic treatments, without systemic effects in patients with genetic high risks of caries.

The understanding of the nonlinear optical (NLO) properties of photonic materials is relevant and necessary for basic studies and technological developments. Among the materials with high optical n...

By employing the optical Kerr gate technique at 800 nm with 180 fs pulses at 76 MHz, we evaluated the third-order nonlinear optical response of two-dimensional (2D) semiconducting MoS2, semimetallic ZrTe2, and metallic NbS2 and NbSe2. The modulus of the nonlinear refractive index was measured to range from 8.6 × 10−19 m2/W to 5.3 × 10−18 m2/W, with all materials’ response time limited by the pulse duration. The physical mechanism to explain the ultrafast response time’s origin considers the nature of the 2D material, as will be discussed.

We investigate the physical mechanism responsible for spatial self-phase modulation of optical vortex beams after interaction with suspensions of 2D transition metal dichalco-genides and organic solvents in different spectral regions, showing its origin is thermal.

Random lasers are recognized as open cavity complex systems emitting coherent radiation with interesting properties. I shall describe its applications to studies of spin-glass, turbulence and its relation to the Nobel Prize in Physics 2021

The operation of a Hybrid Electronic Addressable Random laser is analyzed. The laser operates as a ϕ-OTDR distributed vibration sensor in a transform-limited mode-locked regime with 41 MHz FWHM bandwidth and

We discuss the physical mechanism responsible for spatial self-phase modulation in suspensions of 2D transition metal dichalcogenides using linearly and circularly polarized light, showing its thermal origin when CW or MHz-mode-locked lasers are employed.

Biosilicate and silver diamine fluoride were tested for remineralization through optical coherence tomography, and surface staining through CIELAB system in root caries. Both showed remineralization, however biosilicate showed lower surface staining.

In this work, we report the first nonlinear refraction (NLR) measurements of CVD monolayer ReS2. Using an 800-nm femtosecond laser, a high nonthermal NLR of 2.39x10−8cm2/W was obtained, 3× higher than that of monolayer WS2.

Here we investigate the third-order Nonlinear Optical (NLO) properties of Layered Transition Metal Dichalcogenides (LTMDs), the metallic NbS2. The Z-scan technique was employed to characterize the nonlinear refraction (NLR) and nonlinear absorption (NLA) behavior in the picosecond regime.

We report a new synthesis route to prepare YAB:Nd particles, on the basis of the urea precipitation method. The results confirmed the trigonal symmetry and the stimulated emission leading to random lasing in the powder.

YAG (Yttrium Aluminum Garnet) spheres doped with different lanthanide ions were obtained via Spray Pyrolysis. The Nd3+:YAG particles were studied for their stimulated emissions in disordered environments, while Yb3+/Er3+:YAG were intended for studies at different temperatures.

This paper reviews the work carried out in the field of nonlinear optics in two-dimensional and ultrathin lamellar materials, with a special focus on contributions authored and co-authored by researchers affiliated with Latin American institutions. It is shown that important and impactful contributions have emerged from Latin America, which has a consolidated and active optics community. Nonlinear optical refraction, nonlinear optical absorption, and nonlinear frequency conversion in materials such as graphene, transition metal dichalcogenides, and black phosphorus are among the reviewed themes.

The 2022 Latin America Optics and Photonics Conference (LAOP 2022), the major international conference sponsored by Optica in Latin America, returned to Recife, Pernambuco, Brazil, after its first edition in 2010. Held every two years since (except for 2020), LAOP has the explicit objective to promote Latin American excellence in optics and photonics research and support the regional community. In the 6th edition in 2022, it featured a comprehensive technical program with recognized experts in fields critical to Latin America, highly multidisciplinary, with themes from biophotonics to 2D materials. The 191 attendees of LAOP 2022 listened to five plenary speakers, 28 keynotes, 24 invited talks, and 128 presentations, including oral and posters.

To explore novel up-conversion (UC) system for optical temperature sensing, a series of Tm/Yb:SrF2 fluoride powders were fabricated employing a combustion synthesis (CS) technique. When Tm/Yb: SrF2 samples were excited by near-infrared radiation (~ 980 nm), four UC emission bands at ~ 477 nm (1G4 → 3H6), ~ 649 nm (1G4 → 3F4), ~ 700 nm (3F2,3 → 3H6) and ~ 771 nm (3H4 → 3H6) were observed. Non-contact thermal sensing performances based on temperature-dependent fluorescence intensity ratio (FIR) technique of thermally and non-thermally coupled energy levels were estimated in the range from 298 to 573 K. The co-doped phosphor showed, at 298 K, a maximum relative sensitivity SNTr of ~ 2.2%K−1 for the non-thermally coupled energy levels [(3H4 → 3H6)/ (1G4 → 3H6)] and a maximum relative sensitivity Sr of ~ 1.7%K−1 for the thermally coupled levels [(3F2,3 → 3H6)/(3H4 → 3H6)]. These outcomes show a good temperature-sensing performance when the non-thermally coupled levels with different temperature dependences were selected as the thermometric parameters. Hence, the Tm/Yb: SrF2 UC system has a promising prospect as optical temperature-sensing material.

The hybrid electronically addressable random (HEAR) laser is a novel type of random fiber laser that presents the remarkable property of selection of the fiber section with lasing emission. Here we present a joint analysis of the correlations between intensity fluctuations at distinct wavelengths and replica symmetry breaking (RSB) behavior of the HEAR laser. We introduce a modified Pearson coefficient that simultaneously comprises both the Parisi overlap parameter and standard Pearson correlation coefficient. Our results highlight the contrast between the correlations and presence or not of RSB phenomenon in the spontaneous emission behavior well below threshold, replica-symmetric ASE regime slightly below threshold, and RSB phase with random lasing emission above threshold. In particular, in the latter we find that the onset of RSB behavior is accompanied by a stochastic dynamics of the lasing modes, leading to competition for gain intertwined with correlation and anti-correlation between modes in this complex photonic phase.

Nonlinear optical characterization of nanostructured layered transition metal dichalcogenides (LTMDs) is of fundamental interest for basic knowledge and applied purposes. In particular, second-order optical nonlinearities are the basis for second harmonic generation as well as sum or difference frequency generation and have been studied in some 2D TMDs, especially in those with a semiconducting character. Here we report, for the first time, on the second-order nonlinearity of the semi-metallic ZrTe2 monolayer in acetonitrile suspension (concentration of 4.9 × 1010 particles per cm3), synthesized via a modified redox exfoliation method and characterized using the Hyper-Rayleigh scattering technique in the nanosecond regime. The orientation-averaged first-hyperpolarizability was found to be β(2ω) = (7.0 ± 0.3) × 10-24 esu per ZrTe2 monolayer flake, the largest reported so far. Polarization-resolved measurements were performed in the monolayer suspension and indicate the dipolar origin of the generated incoherent second harmonic wave.

AIM To compare the effect of erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser at different irradiation parameters and acid etching on the shear bond strength (SBS) of orthodontic brackets to enamel. MATERIALS AND METHODS Forty bovine incisors were randomly distributed into groups (n = 10): GI: 37% phosphoric acid etching; GII: Er,Cr:YSGG laser etching 19.1 J/cm2; GIII: Er,Cr:YSGG, 29.3 J/cm2; and GIV: Er,Cr:YSGG, 42.4 J/cm2. After treatments, metallic brackets were bonded using Transbond XT adhesive system. After light curing, the samples were subjected to 500 thermal cycles, debonded with a universal testing machine, and the SBS values were recorded. After debonding, surface morphology was evaluated using scanning electron microscopy (SEM) and optical coherence tomography (OCT). The values of SBS testing were analyzed by one-way analysis of variance (ANOVA) and Tukey post hoc test, at 5% significance level. RESULTS The mean SBS values of GI, GII, GIII, and GIV groups were 6.2 ± 1.7 MPa, 4.6 ± 2.5 MPa, 7.0 ± 2.2 MPa, and 8.0 ± 3.6 MPa, respectively. Laser irradiation promoted rough surfaces in all parameters used, and the OCT analysis revealed higher optical changes on lased groups when compared with phosphoric acid. CONCLUSION Er,Cr:YSGG laser irradiation operated at 42.4 J/cm2 and 29.3 J/cm2 is a better alternative for etching enamel prior to the orthodontic treatment than the phosphoric acid. CLINICAL SIGNIFICANCE Er,Cr:YSGG laser irradiation is better than the phosphoric acid for etching enamel prior to the orthodontic treatment because laser irradiation promotes similar SBSs and preventing demineralization around orthodontic brackets.

The available methods for veneer evaluation are limited to clinical and radiographic examinations, which may not allow the appropriate identification of failure. In this report, we demonstrate the use of optical coherence tomography (OCT) as a noninvasive diagnostic and follow-up method to evaluate gingival recovery and the adhesive interface in aesthetic oral rehabilitation involving periodontal plastic surgery and ceramic laminate veneers. OCT was efficient for evaluating both soft and hard tissues, as well as the quality of the adhesive interface. In conclusion, OCT was found to be a promising approach for the professional evaluation of aesthetic oral rehabilitation, as it was capable of generating images that enabled the analysis of gingival recovery and the adhesive interface.

Plasmonically enhanced random lasing in eggshell biomembranes is reported using a hybrid metalorganic system comprised by Rhodamine 6G as gain medium and silver nanoparticles as the plasmonic metal. The scattering mechanism responsible for feedback in the random laser action arises from the submicron randomly arranged structure of the eggshell biomembrane. The measured spectral narrowing in the biomembranes without Ag is of the same order as of the Ag-infiltrated biomembrane, showing an emission linewidth reduction from ∼45 ± 2 nm below threshold to ∼5.0 ± 0.5 nm above threshold. On the other hand, the effect of the plasmon enhancement is clearly seen in the emitted random laser intensity, which is more efficient and with a lower threshold in the presence of the Ag nanoparticles. We also investigated the spatial behavior of the random laser emission, which shows hot spots with higher intensity in the presence of the Ag nanoparticles, arising from the plasmonic enhancement.

The authors experimentally demonstrate the operation of a lasing phase-sensitive optical time-domain reflectometer (Φ-OTDR) based on random feedback from a sensing fiber. Here, the full output of the laser provides the sensing signal, in contrast to the small backscattered signal measured in a conventional OTDR. In this proof-of-principle demonstration, the laser operates as a distributed vibration sensor with signal-to-noise ratio of 23-dB and 1.37-m spatial resolution.