Optical Lattice Trap for Kerr Solitons

We show theoretically and numerically that dichromatic pumping of a nonlinear microresonator by two continuous wave coherent optical pumps creates an optical lattice trap that results in the localization of intra-cavity Kerr solitons with soliton positions defined by the beat frequency of the pumps. This phenomenon corresponds to the stabilization of the Kerr frequency comb repetition rate. The locking of the second pump, through adiabatic tuning of its frequency, to the comb generated by the first pump allows transitioning to single-soliton states, manipulating the position of Kerr solitons in the cavity, and tuning the frequency comb repetition rate within the locking range. It also explains soliton crystal formation in resonators supporting a dispersive wave emitted as a result of higher-order group velocity dispersion or avoided mode crossing. We show that dichromatic pumping by externally stabilized pumps can be utilized for stabilization of microresonator-based optical frequency combs when the comb span does not cover an octave or a significant fraction thereof and standard self-referencing techniques cannot be employed. Our findings have significant ramifications for high-precision applications of optical frequency combs in spectrally pure signal generation, metrology, and timekeeping.Comment: 13 pages, 12 figure

Third-degree heart block in thalassemia major: A case report

Background: First and second-degree heart blocks are partly common rhythm disorders in thalassemic patients but complete heart block is a very rare complication of iron overload cardiomyopathy. Case Presentation: This 15-year-old boy, a known case of major β-thalassemia was admitted to our emergency unit with dyspnea and cough because of decompensated heart failure. The electrocardiogram showed complete heart block with junctional escape rhythm. Interestingly, his previous electrocardiogram taken 2 months earlier, had some PVC and second degree, Mobitz type 1 (Wenckebach) heart block. After improvement of dyspnea and control of blood pressure in normal range, the patient was referred to ER. A dual-chamber permanent pacemaker was implanted and his symptoms improved, but he died 24 days after discharge from hospital. Conclusion: We present a rare case of complete heart block after a second-degree (Mobitz 1) heart block that was due to severe iron overload cardiomyopathy. © 2012 by Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Sciences

Passively mode locked Raman laser

We report on the observation of a novel mode locked optical comb generated at the Raman offset (Raman comb) in an optically pumped crystalline whispering gallery mode resonator. Mode locking is confirmed via measurement of the radio-frequency beat note produced by the optical comb on a fast photodiode. Neither the conventional Kerr comb nor hyper-parametric oscillation is observed when the Raman comb is present