In the applications of optical communication and light-matter interaction manipulation, the capability of on-demand lasing output with programmable and continuous wavelength tunability over a broad spectral range under low threshold is key functionality. However, the ability to control multiwavelength lasing characteristics within a small mode volume with high reconfigurability remains challenging. The number of dyes and the emission wavelengths of existing materials always restrict the color gamut. A tunable laser with a selection of wavelength via the capability of a single chip has been a subject of great interest in recent years, with the realization of a selection of emission wavelength tunable laser as the ultimate goal.

In this Letter, we introduce a selection of emission wavelength laser by injecting Rhodamine 6G solution mixed with Au nanoparticles in the metal-cladded slab-capillary hybrid microcavity. The R6G solution mixed with Au nanoparticles of different diameters emits lasers of different wavelengths due to the resonant wavelengths of the Au nanoparticles being related to their size. A mechanism for tuning laser emission wavelengths is designed by manipulating the diameter of Au nanoparticles in Rhodamine 6G solution. Precision control of distinctive lasing wavelengths and a narrower peak are achieved, along with a stable lasing beam output from both ends of the capillary due to coherent superposition, and the laser peak always increases with the power of the pump light. This selection of emission wavelength laser has the advantages of easy preparation, availability for integration, and small size. Our findings offer possibilities for realizing a micro selection of emission wavelength laser from a single overall structure.

FIG. 1.  Laser emission in the capillary hybrid microcavity. (a) Fluorescence spectrum of R6G. (b) Injection of Au nanoparticles and R6G into the capillary under the action of pump light can catch the lasing beam. (c) Approximately 594 nm laser beam after passing through the transmissive narrow-band filter. (d) The laser intensity at approximately 594 nm varies with the pump light at 532 nm. (e) The spectrum of the pumping and laser beam using the spectrograph.

FIG. 2. Comparison of laser beams after injecting Au nanoparticles with different diameters. (a)–(c) The intensity of light from the capillary mixed with Au nanoparticles of 40, 50, and 60 nm. The black line corresponds to a stronger pump light power (∼10 µW) while the red line corresponds to a pump light power of approximately 5 µW. (d) The intensity of light from the capillary without Au nanoparticles.

This research was published in “Hong Yang, Hailang Dai, Qiheng Wei, Hongrui Shan, Zhuangqi Cao and Xianfeng Chen, Selection of emission wavelength of lasing via a hybrid microcavity, Physical Review Applied, 16, 034015 (2021)”.

Link: https://link.aps.org/doi/10.1103/PhysRevApplied.16.034015