POEM seems to be a promising new treatment for failed Heller myotomy resulting in short-term symptom relief in > 90 % of cases. Previous Heller myotomy may make subsequent endoscopic remyotomy more challenging, but does not prevent successful POEM.
Solar cells and optical detection devices often incorporate antireflective surfaces to reduce undesired reflection and enhance optical absorption. This letter reports a “black silicon” structure of antireflective porous silicon fabricated by using electrochemical etching. The sample has a gradient-index multilayer structure, i.e., the refraction indices of the structure increase from the top (near the air) to the bottom (near the Si substrate). Reflectance below 5% is obtained over a broad wave number range (3000–28000cm−1) and the depression mechanism of the optical reflectance is analyzed by simulating the structure with the transfer matrix method. The simulated result fits the measured spectra well.
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