Amplified spontaneous emission and gain in highly concentrated Rhodamine-doped peptide derivative.

Bioinspired fluorescence, being widely explored for imaging purposes, faces challenges in delivering bright biocompatible sources. While quite a few techniques have been developed to reach this goal, encapsulation of high-quantum yield fluorescent dyes in natural biological forms suggest achieving superior light-emitting characteristics, approaching amplified spontaneous emission and even lasing. Here we compare gain capabilities of highly concentrated Rhodamine B solutions with a newly synthesized biocompatible peptide derivative hybrid polymer/peptide material, RhoB-PEG1300-F6, which contains the fluorescent covalently bound dye. While concentration quenching effects limit the maximal achievable gain of dissolved Rhodamine B, biocompatible conjugation allows elevating amplification coefficients towards moderately high values. In particular, Rhodamine B, anchored to the peptide derivative material, demonstrates gain of 22-23 cm-1 for a 10-2 M solution, while a pure dye solution possesses 25% smaller values at the same concentration. New biocompatible fluorescent agents pave ways to demonstrate lasing in living organisms and can be further introduced to therapeutic applications, if proper solvents are found.

Partially coherent radar unties range resolution from bandwidth limitations.

It is widely believed that range resolution, the ability to distinguish between two closely situated targets, depends inversely on the bandwidth of the transmitted radar signal. Here we demonstrate a different type of ranging system, which possesses superior range resolution that is almost completely free of bandwidth limitations. By sweeping over the coherence length of the transmitted signal, the partially coherent radar experimentally demonstrates an improvement of over an order of magnitude in resolving targets, compared to standard coherent radars with the same bandwidth. A theoretical framework is developed to show that the resolution could be further improved without a bound, revealing a tradeoff between bandwidth and sweep time. This concept offers solutions to problems which require high range resolution and accuracy but available bandwidth is limited, as is the case for the autonomous car industry, optical imaging, and astronomy to name just few.