RGB WGM lasing woven in fiber braiding cavity

This study is led by professor Tianrui Zhai (Faculty of Science, Beijing University of Technology). The fiber braiding cavity is designed to achieve the red-green-blue (RGB) whispering gallery mode (WGM) lasing with large color gamut by a facile approach. The braiding cavity consists of three dye-doped polymer fibers. The polymer fiber is fabricated brush-coating technology. The dyes doped polymer ink are brush coated onto the optical fiber to form red-emitting fiber (R-fiber), green-emitting fiber (G-fiber) and blue-emitting fiber (B-fiber).

Each polymer fiber before weaving can act as an excellent WGM microcavity properties, with lower excitation threshold of 19.1 μJ/cm², narrowest spectral linewidth of 0.045 nm and high quality (Q) factor (10⁴). The results verify that the polymer fiber has lower optical loss. The peak wavelength can be tunable by changing the cavity diameter (mλ_m = πn_effD). The Q factor of WGM lasing is positively correlated with the D. The Q value is calculated using the equation Q≈ λ⁄Δλ. The calculation of Q value is from 1×10⁴ to 3×10⁴ when altering dye-coated fiber diameter from 80 μm to 265 μm. This can be attributed to the local time increase by the increase of cavity diameter.

The researchers obtain seven lasing spectra including blue (B), green (G) and red (R) lasing, dual-color lasing (G+B), (R+B), (R+G) and full-color lasing (R+G+B). The emission spectrum of full-color WGM lasing covers the whole visible region in the fiber braiding cavity. The white circle named as “R+G+B” denotes the International Commission on Illumination (CIE) 1931 color diagram of the mixed white light. The lasing emissions cover a color gamut 86.7 % larger than the standard RGB (sRGB) space, showing great potential in compact white sources and laser display devices.

See the article:

RGB WGM lasing woven in fiber braiding cavity

https://doi.org/10.1007/s11432-022-3436-y

---

---