Precise Determination of Minimum Achievable Temperature for Solid-State Optical Refrigeration

We measure the minimum achievable temperature (MAT) as a function of excitation wavelength in anti-Stokes fluorescence cooling of high purity Yb3+-doped LiYF4 (Yb:YLF) crystal. Such measurements were obtained by developing a sensitive noncontact thermometry that is based on a two-band differential luminescence spectroscopy using balanced photo-detectors. These measurements are in excellent agreement with the prediction of the laser cooling model and identify MAT of 110 K at 1020 nm, corresponding to E4-E5 Stark manifold transition in Yb:YLF crystal.Comment: 10 pages, 6 figure

Application of a smart dynamic scale for measuring live-fish biomass in aquaculture

— The need of measuring the fish biomass, either for in-land facilities or offshore cages, drove recently to develop a cheap dynamic scale (by MEGA Materials srl), based on a board of the Arduino family, suitable to measure live-fish weights. Via a Bluetooth transmitter and a specific app the communication with smartphones is allowed. The estimation of live-fish biomass is extremely relevant to precisely quantify the daily dose of feed to be supplied and to avoid a reduction of fish growth. We present the comparison between ‘static’ and ‘dynamic’ weight measures of seabream juveniles reared in tanks

Investigation of Yb-doped LiLuF4 single crystals for optical cooling

Optical cooling of solids, relying on annihilation of lattice phonons via anti-Stokes fluorescence, is an emerging technology that is rapidly advancing. The development of high-quality Yb-doped fluoride single crystals definitely led to cryogenic and sub-100-K operations, and the potential for further improvements has not been exhausted by far. Among fluorides, so far the best results have been achieved with Yb-doped LiYF4 (YLF) single crystals, with a record cooling to 91 K of a stand-alone YLF:10%Yb. We report on preliminary investigation of optical cooling of an LiLuF4 (LLF) single crystal, an isomorph of YLF where yttrium is replaced by lutetium. Different samples of 5% Yb-doped LLF single crystals have been grown and optically characterized. Optical cooling was observed by exciting the Yb transition in single-pass at 1025 nm and the cooling efficiency curve has been measured detecting the heating/cooling temperature change as a function of pumping laser frequency

on a rapidly converging iterative algorithm for diode parameter extraction from a single iv curve

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Atomic-layer molybdenum sulfide optical modulator for visible coherent light

Coherent light sources in the visible range are playing important roles in our daily life and modern technology, since about 50% of the capability of the our human brains is devoted to processing visual information. Visible lasers can be achieved by nonlinear optical process of infrared lasers and direct lasing of gain materials, and the latter has advantages in the aspects of compactness, efficiency, simplicity, etc. However, due to lack of visible optical modulators, the directly generated visible lasers with only a gain material are constrained in continuous-wave operation. Here, we demonstrated the fabrication of a visible optical modulator and pulsed visible lasers based on atomic-layer molybdenum sulfide (MoS 2), a ultrathin two-dimensional material with about 9-10 layers. By employing the nonlinear absorption of the modulator, the pulsed orange, red and deep red lasers were directly generated. Besides, the present atomic-layer MoS 2 optical modulator has broadband modulating properties and advantages in the simple preparation process. The present results experimentally verify the theoretical prediction for the low-dimensional optoelectronic modulating devices in the visible wavelength region and may open an attractive avenue for removing a stumbling block for the further development of pulsed visible lasers

Nonlinear optical response of Au nanorods for broadband pulse modulation in bulk visible lasers

Due to the lack of suitable optical modulators, directly generated Pr3+- and Dy3+-doped bulk visible lasers are limited in the continuous-wave operation; yet, pulsed visible lasers are only sparingly reported recently. It has been theoretically predicated that Au nanorods could modulate the visible light operation, based on the nonlinear optical response of surface plasmon resonance. Here, we demonstrate the saturable absorption properties of Au nanorods in the visible region and experimentally realized the pulsed visible lasers over the spectral range of orange (605nm), red (639nm), and deep red (721nm) with Au nanorods as the optical modulator. We show that Au nanorods have a broad nonlinear optical response and can serve as a type of broadband, low-cost, and eco-friendly candidate for optical switchers in the visible region. Our work also advocates the promise of plasmonic nanostructures for the development of pulsed lasers and other plasmonic devices

Cascade Superfluorescence in Er:YLF

We report the analysis of paired photon pulses arising from two cascading transitions in continuously pumped Erbium-doped YLiF$_4$ 1% and 0.01% crystals at 1.6 K. The dependence of the pulse peak intensity on the squared number of involved Erbium ions, between 10$^{11}$ and 10$^{13}$, definitely identifies the cooperative nature of the two pulsed emissions, that are generated by the subsequent, spontaneous formation of coherent states. The observed fluctuations of the time interval between the paired pulses and, most importantly, its correlation with the second pulse duration, demonstrate that the Erbium ions coherence is indeed seeded by vacuum fluctuations

Comparative spectroscopic and thermo-optic study of Tm: LiLnF4 (Ln = Y, Gd, and Lu) crystals for highly-efficient microchip lasers at ~2 μm

We report on a detailed comparative study of the spectroscopic and thermo-optic properties of tetragonal Tm:LiLnF4 (Ln = Y, Gd, and Lu) crystals indicating their suitability for highly-efficient microchip lasers diode-pumped at ~791 nm and operating at ~1.91 μm. An a-cut 8 at.% Tm:LiYF4 micro-laser generated 3.1 W of linearly polarized output at 1904 nm with a slope efficiency of η = 72% and a laser threshold of only 0.24 W. The internal loss for this crystal is as low as 0.0011 cm-1. For 8 at.% Tm:LiGdF4 and 12 at.% Tm:LiLuF4 lasers, the output power reached ~2 W and η was 65% and 52%, respectively. The thermal lens in all Tm:LiLnF4 crystals is weak, positive and low-astigmatic. The potential for the Tm:LiLnF4 lasers to operate beyond ~2 μm due to a vibronic coupling has been proved. The Tm:LiYF4 vibronic laser generated 375 mW at 2026-2044 nm with η = 31%. The Tm:LiLnF4 crystals are very promising for passively Q-switched microchip lasers

Sense of smell in chronic rhinosinusitis: A multicentric study on 811 patients

Introduction: The impairment of the sense of smell is often related to chronic rhinosinusitis (CRS) with or without nasal polyps (CRSwNP, CRSsNP). CRSwNP is a frequent condition that drastically worsens the quality of life of those affected; it has a higher prevalence than CRSsNP. CRSwNP patients experience severe loss of smell with earlier presentation and are more likely to experience recurrence of their symptoms, often requiring revision surgery. Methods: The present study performed a multicentric data collection, enrolling 811 patients with CRS divided according to the inflammatory endotype (Type 2 and non-Type 2). All patients were referred for nasal endoscopy for the assessment of nasal polyposis using nasal polyp score (NPS); Sniffin' Sticks olfactory test were performed to measure olfactory function, and SNOT-22 (22-item sinonasal outcome test) questionnaire was used to assess patients' quality of life; allergic status was evaluated with skin prick test and nasal cytology completed the evaluation when available. Results: Data showed that Type 2 inflammation is more common than non-type 2 (656 patients versus 155) and patients suffer from worse quality of life and nasal polyp score. Moreover, 86.1% of patients with Type 2 CRSwNP were affected by a dysfunction of the sense of smell while it involved a lesser percentage of non-Type 2 patients. Indeed, these data give us new information about type-2 inflammation patients' characteristics. Discussion: The present study confirms that olfactory function weights on patients' QoL and it represents an important therapeutic goal that can also improve patients' compliance when achieved. In a future - and present - perspective of rhinological precision medicine, an impairment of the sense of smell could help the clinician to characterize patients better and to choose the best treatment available