Near to short wave infrared light generation through AlGaAs-on-insulator nanoantennas.

AlGaAs-on-insulator (AlGaAs-OI) has recently emerged as a promising platform for nonlinear optics at the nanoscale. Among the most remarkable outcomes, second-harmonic generation (SHG) in the visible/near infrared spectral region has been demonstrated in AlGaAs-OI nanoantennas (NAs). In order to extend the nonlinear frequency generation towards the short wave infrared window, in this work we propose and demonstrate via numerical simulations difference frequency generation (DFG) in AlGaAs-OI NAs. The NA geometry is finely adjusted in order to obtain simultaneous optical resonances at the pump, signal and idler wavelengths, which results in an efficient DFG with conversion efficiencies up to 0.01%. Our investigation includes the study of the robustness against random variations of the NA geometry that may occur at fabrication stage. Overall, these outcomes identify what we believe to be a new potential and yet unexplored application of AlGaAs-OI NAs as compact devices for the generation and control of the radiation pattern in the near to short infrared spectral region.

Transient guided-mode resonance metasurfaces with phase-transition materials.

We investigate transient, photo-thermally induced metasurface effects in a planar thin-film multilayer based on a phase-transition material. Illumination of a properly designed multilayer with two obliquely incident and phase-coherent pulsed pumps induces a transient and reversible temperature pattern in the phase-transition layer. The deep periodic modulation of the refractive index, caused by the interfering pumps, produces a transient Fano-like spectral feature associated with a guided-mode resonance. A coupled opto-thermal model is employed to analyze the temporal dynamics of the transient metasurface and to evaluate its speed and modulation capabilities. Using near-infrared pump pulses with peak intensities of the order of 100 MW/cm2 and duration of a few picoseconds, we find that the characteristic time scale of the transient metasurface is of the order of nanoseconds. Our results indicate that inducing transient metasurface effects in films of phase-transition materials can lead to new opportunities for dynamic control of quality (Q)-factor in photonic resonances, and for light modulation and switching.

Opto-thermally controlled beam steering in nonlinear all-dielectric metastructures.

Reconfigurable metasurfaces have recently gained a lot of attention in applications such as adaptive meta-lenses, hyperspectral imaging and optical modulation. This kind of metastructure can be obtained by an external control signal, enabling us to dynamically manipulate the electromagnetic radiation. Here, we theoretically propose an AlGaAs device to control the second harmonic generation (SHG) emission at nanoscale upon optimized optical heating. The asymmetric shape of the used meta-atom is selected to guarantee a predominant second harmonic (SH) emission towards the normal direction. The proposed structure is concurrently excited by a pump beam at a fundamental wavelength of 1540 nm and by a continuous wave (CW) control signal above the semiconductor band gap. The optical tuning is achieved by a selective optimization of meta-atoms SH phase, which is modulated by the control signal intensity. We numerically demonstrate that the heating induced in the meta-atoms by the CW pump can be used to dynamically tune the device properties. In particular, we theoretically demonstrate a SH beam steering of 8° with respect to the vertical axis for an optimized device with average temperature increase even below 90° C.

Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces.

We demonstrate optically tunable control of second-harmonic generation in all-dielectric nanoantennas: by using a control beam that is absorbed by the nanoresonator, we thermo-optically change the refractive index of the radiating element to modulate the amplitude of the second-harmonic signal. For a moderate temperature increase of roughly 40 K, modulation of the efficiency up to 60% is demonstrated; this large tunability of the single meta-atom response paves the way to exciting avenues for reconfigurable homogeneous and heterogeneous metasurfaces.

Efficacy and tolerability of short contact therapy with tretinoin, clindamycin, and glycolic acid gel in acne: A randomized, controlled, assessor-blinded two-center trial: The MASCOTTE study.

Retinoids and antibiotics topical treatments are commonly used as first line therapy in mild to moderate acne. However, irritant contact dermatitis is a common side effect of topical retinoids. A strategy to increase local tolerability is the "short contact therapy" (SCT) approach, consisting in the application of the product with the complete removal after 30 to 60 minutes using a non-aggressive cleanser. A gel containing tretinoin 0.02%, clindamycin 0.8%, and glycolic acid 4% in polyvinyl alcohol (MP-gel) has shown to be effective as monotherapy in mild to moderate acne with a tolerability profile similar to other topical retinoids. So far, no trials have been performed with this gel comparing the tolerability profile of SCT with standard application therapy (SAT). We conducted a 2-center randomized parallel groups, controlled, assessor-blinded study, comparing MP-gel applied as SCT in comparison with MP-gel used as SAT (The "MASCOTTE" trial). Forty-six subjects (nine men and 37 women, mean age 23 ± 4 years, range 18-31 years) with mild-to-moderate acne were enrolled, after their written informed consent in a randomized, parallel groups controlled, assessor-blinded 8-week trial. Twenty-three were assigned to MP-gel once daily (evening application) using the SCT approach (ie, complete removal of product after 1 hour using a gentle cleanser), and 23 were randomized to the SAT approach with the same gel. The primary endpoint was the evolution of the tolerability score (TS) assessed evaluating four items: erythema, dryness, stinging, and burning, using a 4-point score scale (from 0: no symptom to 3: severe symptom). Secondary endpoints were the evolution of global acne grading system (GAGS) score (range: from 0 to >39) and the investigator global assessment (IGA of acne severity) score (range from 0 to 4). TS was evaluated at 2, 4, and 8 weeks. GAGS and IGA scores were evaluated at baseline and at week eight. At week eight, an efficacy global score (EGS) (from 1: no efficacy to 4: very good efficacy) and a tolerability global score (TGS) (from 1: very low tolerability to 3: very good tolerability) evaluation were also done. All the evaluations were performed by an investigator unaware of treatment groups allocation (SCT or SAT). Thirty-eight subjects (83%) completed the 8-week treatment period. Eight subjects (two in the SCT group and six in the SAT group) dropped out prematurely due to low skin tolerability. In the SCT the TS at week two was 1.3 ± 1.7, in the SAT group TS was significantly higher (3.1 ± 1.7) (P = .028). TS was significantly lower in SCT group vs SAT also at weeks four and eight (P = .01; ANOVA test). The GAGS score at baseline was 19 ± 7 in the SCT group and 23 ± 4 in the SAT group (NS). At week 8 the GAGS score in SCT was significantly reduced to 8.5 ± 2.8 (-55%) (P = .001 vs baseline) and was also significantly lower in comparison with SAT group (8.5 vs 15; P = .0054). The IGA scores at baseline were 1.9 ± 0.6 in SCT and 2.4 ± 0.7 in SAT group. At week eight, in comparison with baseline values IGA score was reduced significantly by 48% in SCT and by 30% in SAT. EGS and TGS were significantly higher (better clinical efficacy and better tolerability) in SCT in comparison with SAT (3.6 ± 0.5 and 2.9 ± 0.3 vs 2.7 ± 0.6 and 1.5 ± 0.7; respectively). This tretinoin, clindamycin, glycolic acid gel, applied as SCT, has shown a better skin tolerability and at least a comparable clinical efficacy in comparison with the standard application modality in the treatment of mild-to-moderate acne. The SCT therefore could be an effective treatment strategy which could improve subjects' compliance and adherence.

Time-resolved thermal lens investigation of glassy dynamics in supercooled liquids: Theory and experiments.

This work reports results on the simultaneous spectroscopy of the specific heat and thermal expansivity of glycerol by making use of a wideband time-resolved thermal lens (TL) technique. An analytical model is presented which describes TL transients in a relaxing system subjected to impulsive laser heating. Experimentally, a set of TL waveforms, from 1 ns to 20 ms, has been recorded for a glycerol sample upon supercooling, from 300 to 200 K. The satisfactory fitting of the TL signals to the model allows the assessment of relaxation strength and relaxation frequency of the two quantities up to sub-100 MHz, extending the specific heat and thermal expansion spectroscopy by nearly three and eight decades, respectively. Fragility values, extracted from the relaxation behavior of the specific heat and the thermal expansion coefficient, are found to be similar, despite a substantial difference in relaxation strength.

Revisiting impulsive stimulated thermal scattering in supercooled liquids: Relaxation of specific heat and thermal expansion.

Impulsive stimulated thermal scattering (ISTS) allows one to access the structural relaxation dynamics in supercooled molecular liquids on a time scale ranging from nanoseconds to milliseconds. Till now, a heuristic semi-empirical model has been commonly adopted to account for the ISTS signals. This model implicitly assumes that the relaxation of specific heat, C, and thermal expansion coefficient, γ, occur on the same time scale and accounts for them via a single stretched exponential. This work proposes two models that assume disentangled relaxations, respectively, based on the Debye and Havriliak-Negami assumptions for the relaxation spectrum and explicitly accounting for the relaxation of C and γ separately in the ISTS response. A theoretical analysis was conducted to test and compare the disentangled relaxation models against the stretched exponential. The former models were applied to rationalize the experimental ISTS signals acquired on supercooled glycerol. This allows us to simultaneously retrieve the frequency-dependent specific heat and thermal expansion up to the sub-100 MHz frequency range and further to compare the fragility and time scale probed by thermal, mechanical, and dielectric susceptibilities.

Temperonic Crystal: A Superlattice for Temperature Waves in Graphene.

The temperonic crystal, a periodic structure with a unit cell made of two slabs sustaining temperature wavelike oscillations on short timescales, is introduced. The complex-valued dispersion relation for the temperature scalar field is investigated for the case of a localized temperature pulse. The dispersion discloses frequency gaps, tunable upon varying the slabs' thermal properties. Results are shown for the paradigmatic case of a graphene-based temperonic crystal. The temperonic crystal extends the concept of superlattices to the realm of temperature waves, allowing for coherent control of ultrafast temperature pulses in the hydrodynamic regime at above liquid nitrogen temperatures.

Blue nevus of the nail: A case report and review.

Blue nevus (BN), in all its clinical variants, rarely affects the nail bed. This leads to difficulty in the diagnosis of BN within the nail bed as well as to challenges with regard to its treatment and follow-up management, not solely attributed to the intrinsic difficulty of the anatomical site. We present the first case in the literature of an acquired cellular BN entirely confined within the nail bed, in a female Caucasian patient. We propose diagnostic and therapeutic options based on personal clinical and surgical experience.

Controlling the Quality Factor of a Single Acoustic Nanoresonator by Tuning its Morphology.

The mechanical vibrations of individual gold nanodisks nanopatterned on a sapphire substrate are investigated using ultrafast time-resolved optical spectroscopy. The number and characteristics of the detected acoustic modes are found to vary with nanodisk geometry. In particular, their quality factors strongly depend on nanodisk aspect ratio (i.e., diameter over height ratio), reaching a maximal value of ≈70, higher than those previously measured for substrate-supported nano-objects. The peculiarities of the detected acoustic vibrations are confirmed by finite-element simulations, and interpreted as the result of substrate-induced hybridization between the vibrational modes of a nanodisk. The present findings demonstrate novel possibilities for engineering the vibrational modes of nano-objects.

Photo-induced heat generation in non-plasmonic nanoantennas.

Light-to-heat conversion in non-plasmonic, high refractive index nanoantennas is a key topic for many applications, including Raman sensing, laser writing, nanofabrication and photo-thermal therapy. However, heat generation and propagation in non-plasmonic antennas is increasingly debated and contradictory results have been reported so far. Here we report a finite element analysis of the steady-state temperature distribution and heat flow in SiO2/Si core/shell systems (silicon nanoshells) irradiated with different continuous wave lasers (λ = 532, 633 and 785 nm), under real working conditions. The complex interplay among the optical properties, morphology, degree of crystallinity of the nanoshells, thickness dependence of thermal conductivity and interactions with the substrate has been elucidated. This study reveals that all of these parameters can be appropriately combined for obtaining either stable nanoshells for Raman sensing or highly efficient sources of local heating. The optimal balance between thermal stability and field enhancement was found for crystalline Si shell layers with thicknesses ranging from 40 to 60 nm, irradiated by a NIR laser source. On the other hand, non-conformal amorphous or crystalline shell layers with a thickness >50 nm can reach a very high local temperature (above 1000 K) when irradiated with a low power density (less than 1 mW µm-2) laser sources. This work provides a general approach for an extensive investigation of the opto-thermal properties of high-index nanoantennas.

Ultrafast nano generation of acoustic waves in water via a single carbon nanotube.

Generation of ultra high frequency acoustic waves in water is key to nano resolution sensing, acoustic imaging and theranostics. In this context water immersed carbon nanotubes (CNTs) may act as an ideal optoacoustic source, due to their nanometric radial dimensions, peculiar thermal properties and broad band optical absorption. The generation mechanism of acoustic waves in water, upon excitation of both a single-wall (SW) and a multi-wall (MW) CNT with laser pulses of temporal width ranging from 5 ns down to ps, is theoretically investigated via a multiscale approach. We show that, depending on the combination of CNT size and laser pulse duration, the CNT can act as a thermophone or a mechanophone. As a thermophone, the CNT acts as a nanoheater for the surrounding water, which, upon thermal expansion, launches the pressure wave. As a mechanophone, the CNT acts as a nanopiston, its thermal expansion directly triggering the pressure wave in water. Activation of the mechanophone effect is sought to trigger few nanometers wavelength sound waves in water, matching the CNT acoustic frequencies. This is at variance with respect to the commonly addressed case of water-immersed single metallic nano-objects excited with ns laser pulses, where only the thermophone effect significantly contributes. The present findings might be of impact in fields ranging from nanoscale non-destructive testing to water dynamics at the meso to nanoscale.

Thermal dynamics and electronic temperature waves in layered correlated materials.

Understanding the mechanism of heat transfer in nanoscale devices remains one of the greatest intellectual challenges in the field of thermal dynamics, by far the most relevant under an applicative standpoint. When thermal dynamics is confined to the nanoscale, the characteristic timescales become ultrafast, engendering the failure of the common description of energy propagation and paving the way to unconventional phenomena such as wave-like temperature propagation. Here, we explore layered strongly correlated materials as a platform to identify and control unconventional electronic heat transfer phenomena. We demonstrate that these systems can be tailored to sustain a wide spectrum of electronic heat transport regimes, ranging from ballistic, to hydrodynamic all the way to diffusive. Within the hydrodynamic regime, wave-like temperature oscillations are predicted up to room temperature. The interaction strength can be exploited as a knob to control the dynamics of temperature waves as well as the onset of different thermal transport regimes.

Discrimination of nano-objects via cluster analysis techniques applied to time-resolved thermo-acoustic microscopy.

Time-effective, unsupervised clustering techniques are exploited to discriminate nanometric metal disks patterned on a dielectric substrate. The discrimination relies on cluster analysis applied to time-resolved optical traces obtained from thermo-acoustic microscopy based on asynchronous optical sampling. The analysis aims to recognize similarities among nanopatterned disks and to cluster them accordingly. Each cluster is characterized by a fingerprint time-resolved trace, synthesizing the common features of the thermo-acoustics response of the composing elements. The protocol is robust and widely applicable, not relying on any specific knowledge of the physical mechanisms involved. The present route constitutes an alternative diagnostic tool for on-chip non-destructive testing of individual nano-objects.

Optical wavelength dependence of photoacoustic signal of gold nanofluid.

We investigate the optical wavelength dependence of the photoacoustic (PA) signal, detected with bandwidth (BW) in the MHz range, of gold nanospheres (NSs) immersed in water upon illumination with ns laser pulses. We compare the wavelength dependence of the PA signal (within the MHz BW) with the one of the optical absorption coefficient as determined from optical transmission measurements. Thermal boundary conductance (TBC) at the gold-water interface is taken into account, as well as the temperature dependence of the thermal expansion coefficient of water. The effects of NS size and laser pulse duration on the PA signal are also explored. The PA signal is investigated with an opto-thermo-acoustic model considering light absorption in gold NS and in a surrounding water shell.

Early Treatment with Imiquimod 5% Cream of Periungual Warts in Vietnam: The Poorer, the Better.

AIM: To evaluate the efficacy of imiquimod 5% in periungual wart treatment. MATERIAL AND METHODS: A group of 40 patients were recruited to apply imiquimod 5 % cream once daily for 5 consecutive days per week in 8 weeks. They were classified into 3 levels: Mild (the total lesion area ≤ 25 mm2), moderate (25 mm2 50 mm2). The outcome was evaluated at the 4th and the 8th week. The result was graded as excellent (complete clearance), good (≥ 50% clearance) and poor (< 50% clearance). RESULTS: The total area of the wart lesion got decreased significantly from the beginning to the 4th and the 8th week (36.7 mm2 vs 16.8 mm2, p = 0.0001 and 16.8 mm2 vs 8.8 mm2, p = 0.01). The complete clearance rate at the 4th week was lower than that at the 8th week significantly (22.5% vs 72.5%, p = 0.04). The clearance rate of patients suffering severe warts was lower significantly than that of mild/moderate patients (82.8% vs 45.5%, p = 0.03). The duration of the disease in people who responded completely to imiquimod was shorter than that of patients partially responded (10.2 ± 14.1 months vs 22.3 ± 14.3 months, p = 0.02). Adverse effects were not common, mild and local only. Recurrence rate after 6 months of follow up was 3.5%. CONCLUSION: In conclusion, Imiquimod 5% cream is a safe and effective drug in the treatment of periungual warts.

Efficacy of Adding Oral Simvastatin to Topical Therapy for Treatment of Psoriasis: The Vietnamese Experience.

BACKGROUND: Psoriasis, the prevalence of which ranges from 2% to 3% of the general population, has been recently recognised as not only a chronic inflammatory skin disorder but also an immunometabolic systemic disease. Dyslipidemia is one of the most important comorbidities of psoriasis. Statins, frequently used as anti-hyperlipidemic agents, may be beneficial in the treatment of several autoimmune diseases, including psoriasis, due to their anti-inflammatory and immunomodulatory characteristics. Hence, we hypothesised that using this medication was not only beneficial for reducing hyperlipidemia but also improving psoriatic conditions. AIM: We conducted a study to determine the prevalence of dyslipidemia in psoriatic patients as well as whether the addition of statins (simvastatin prescribed forms) to standard topical antipsoriatic treatment can improve skin lesions in psoriatic patients. METHODS: A group of 128 psoriatic patients and 128 healthy controls who were matched with the patients regarding ethnicity, age, and sex were enrolled, and their lipid concentrations were determined. Furthermore, sixty patients were randomly selected from the former group and divided into two treatment subgroups to evaluate the effect of statins on the severity of psoriasis using the PASI score. RESULTS: We found that the rate of dyslipidemia in the patient group was significantly higher than in the healthy group (53.9% versus 21.9%, p < 0.001), particularly the triglyceride concentration (1.86 ± 1.17 versus 1.43 ± 0.79 mg/dL, p < 0.001). Also, the PASI score reduction in the simvastatin-treated subgroup was significantly different from that in the placebo-treated one after eight weeks of therapy (8.63 ± 4.78 versus 5.34 ± 3.59, p < 0.01). CONCLUSION: This study showed that simvastatin might play a role in controlling hyperlipidemia and in turn decrease the PASI score in psoriatic patients.