Wideband Tuning and Deep‐Tissue Spectral Detection of Indium Phosphide Nano‐Laser Particles

Abstract

Abstract Laser particles (LPs) emitting narrowband spectra across wide spectral ranges are highly promising for high‐multiplex optical barcoding of biological cells. Here, LPs based on indium phosphide (InP) nanodisks are presented, operating in the near‐infrared wavelength range of 740–970 nm. Utilizing low‐order whispering gallery resonance modes in size‐tuned nanodisks, an ultrawide color palette with 25% spectral utilization and nanometer‐scale linewidth is achieved. A simple theoretical model accurately predicts spectral ranges based on particle size. The minimum laser size is 430 nm in air and 560 nm within cells, operating at mode orders of 4 or 5. The high brightness and narrow linewidths of polymer‐silica‐protected InP LPs, combined with a silicon‐detector spectrometer, enable spectral detection of laser peaks with high signal‐to‐background ratios in highly‐scattering media, including 1‐cm‐thick chicken breast tissue and blood vessels in live mice.