Comparison of Fragmentation and Dusting Laser Modes for Laser Ureteroscopy Lithotripsy of Ureteral Stones at a Single Center

Background Laser ureteroscopic lithotripsy (URSL) is an efficacious treatment for ureteral stones. There have been few previous studies compared the different energy and frequency settings for URSL in a single center. The fragmentation and dusting laser mode were simultaneously used in our medical center. We compared the efficacy and outcomes of these two laser modalities for the treatment of ureteral stones.Methods Patients who underwent fragmentation or dusting laser URSL for ureteral stones were retrospectively reviewed. The demographic data, stone parameters, perioperative data and stone-free rates were analyzed between the two groups.Results There were a total of 421 patients with ureteral stones who met the study criteria. More patients in the dusting group had multiple ureteral stones and pyuria than in the fragmentation group. The fragmentation group had a better stone free rate and a lower push back rate compared with the dusting group. (82% vs. 71%; 10% vs. 20% respectively, both p<0.05). Multivariate analysis revealed that stone basket use (odds ratio [OR] = 3.026; p<0.001) significantly improved the stone free rate, whereas multiple stones (OR=0.322; p <0.001), upper ureteral stone location (OR=0.098; p=0.002) and pyuria (OR=0.428; p=0.001) significantly decreased the stone free rate. The laser mode used was not significantly related to the stone free rate in the multivariate analysis.Conclusions Both laser modes were effective and safe for ureteral lithotripsy. Risk factors associated with a lower stone free rate were multiple stones, pyuria, upper ureteral stone location and an operation without the use of a stone basket.

Quantifying Information via Shannon Entropy in Spatially Structured Optical Beams

While information is ubiquitously generated, shared, and analyzed in a modern-day life, there is still some controversy around the ways to assess the amount and quality of information inside a noisy optical channel. A number of theoretical approaches based on, e.g., conditional Shannon entropy and Fisher information have been developed, along with some experimental validations. Some of these approaches are limited to a certain alphabet, while others tend to fall short when considering optical beams with a nontrivial structure, such as Hermite-Gauss, Laguerre-Gauss, and other modes with a nontrivial structure. Here, we propose a new definition of the classical Shannon information via the Wigner distribution function, while respecting the Heisenberg inequality. Following this definition, we calculate the amount of information in Gaussian, Hermite-Gaussian, and Laguerre-Gaussian laser modes in juxtaposition and experimentally validate it by reconstruction of the Wigner distribution function from the intensity distribution of structured laser beams. We experimentally demonstrate the technique that allows to infer field structure of the laser beams in singular optics to assess the amount of contained information. Given the generality, this approach of defining information via analyzing the beam complexity is applicable to laser modes of any topology that can be described by well-behaved functions. Classical Shannon information, defined in this way, is detached from a particular alphabet, i.e., communication scheme, and scales with the structural complexity of the system. Such a synergy between the Wigner distribution function encompassing the information in both real and reciprocal space and information being a measure of disorder can contribute into future coherent detection algorithms and remote sensing.

Low-threshold and narrow-linewidth perovskite microlasers pumped by a localized waveguide source

For the widely used vertically pumped (VP) method with a free-space beam, very little pump power is absorbed by the gain materials in microlasers because of the large spatial mismatch of areas between laser modes and free-space pump beams together with small thicknesses of gain materials, resulting in a high pump power threshold. Here, an in-plane-waveguide-pump (IPWP) method with a localized waveguide source is proposed to reduce pump power threshold of perovskite microlasers. Owing to reduced spatial mismatch of areas between laser modes and localized waveguide sources as well as increased absorption distances, the pump power threshold of the IPWP method is decreased to approximately 6% that of the VP method. Moreover, under the same multiple of the pump power threshold, the laser linewidth in the IPWP method is narrowed to approximately 70% that in the VP method. By using the IPWP method, selective pumping two adjacent (separation 2 or 3 μm) parallel-located perovskite microlasers is experimentally demonstrated, and no crosstalk is observed. This IPWP method may have applications in low-energy and high-density microlasers and photonic integrated circuits.