High-efficiency second-order nonlinear processes in an optical microfibre assisted by few-layer GaSe

Abstract

The centrosymmetric nature of silica fibre precludes the realisation of second-order nonlinear processes in optical fibre systems. Recently, the integration of 2D materials with optical fibres has opened up a great opportunity to develop allfibre active devices. Here, we demonstrate high-efficiency second-order nonlinear frequency conversions in an optical microfibre assisted with few-layer gallium selenide (GaSe) nanoflakes. Attributed to the strong evanescent field of the microfibre and ultrahigh second-order nonlinearity of the GaSe nanoflakes, second harmonic generation (SHG) and sum-frequency generation (SFG) are effectively achieved with only sub-milliwatt continuous-wave (CW) lasers in the wavelength range of 1500-1620 nm, covering the C and L telecom bands. The SHG intensity from the microfibre is enhanced by more than four orders of magnitude with the assistance of the GaSe nanoflakes on fibre nonlinear processes. Moreover, in the SFG process, the intensity transfer between different frequencies can be effectively manipulated by changing the wavelengths and powers of two pump lasers. The realised strong second-order nonlinearity in the GaSe-integrated microfibre might expand the applications of all-fibre devices in all-optical signal processing and new light source generation at awkward wavelengths.

Harmonic Generation in Low‐Dimensional Materials

“…Recently, the integration of the LDMs with optical fibers has unlocked a great opportunity to develop all fiber active devices. Jiang and co-workers [222] reported an enhanced SHG and SFG from GaSe integrated micro-fiber with only sub-milliwatt power CW laser. The χ (2) in few layer GaSe integrated microfiber was enhanced up to the four order as compared to which achieved with bare micro-fiber.…”

Recent progress in terahertz modulation using photonic structures based on two‐dimensional materials

“…In addition, monolayer TMDCs have strong second-order nonlinearity due to their translational symmetry-breaking structure, which is conducive to nonlinear optical applications (e.g., second harmonic microscopy). 68,69 Also, studies show that 2D TMDCs have strong spin-orbit coupling, raising the intriguing prospect for optical modulation based on valley selective optical properties. 70,71 Other 2D materials with unique optoelectronic properties were also investigated, such as BP, MXenes, and heterostructures.…”

Boosted Second-harmonic generation in the LiNbO$\mathrm{_3}$ metasurface governed by high-Q guided resonances and bound states in the continuum

“…Recently, low-index nonlinear materials, such as AlN, GaSe and LiNbO 3 that have large second-order nonlinear susceptibilities, have attracted increasing attention as they are highly transparent from near-infrared to nearultraviolet spectrum region [33][34][35][36][37]. Over the past few years, the progress of exploiting Mie resonance-based nanostructures and metasurfaces has enabled researchers to achieve enhanced nonlinear generations in these materials.…”