Broadband and continuous wave pumped second-harmonic generation from microfiber coated with layered GaSe crystal

Abstract

The conversion-efficiency for second-harmonic (SH) in optical fibers is significantly limited by extremely weak second-order nonlinearity of fused silica, and pulse pump lasers with high peak power are widely employed. Here, we propose a simple strategy to efficiently realize the broadband and continuous wave (CW) pumped SH, by transferring a crystalline GaSe coating onto a microfiber with phase-matching diameter. In the experiment, high efficiency up to 0.08 %W -1 mm -1 is reached for a C-band pump laser. The high enough efficiency not only guarantees SH at a single frequency pumped by a CW laser, but also multi-frequencies mixing supported by three CW light sources. Moreover, broadband SH spectrum is also achieved under the pump of a superluminescent light-emitting diode source with a 79.3 nm bandwidth. The proposed scheme provides a beneficial method to the enhancement of various nonlinear parameter processes, development of quasi-monochromatic or broadband CW light sources at new wavelength regions.

Parallel fabrication of silica optical microfibers and nanofibers

“…Optical micro/nanofibers (MNFs) drawn from standard silica fibers have been widely used as a miniature fiber-optic platform for manipulating optical fields with great versatility [1][2][3] . Benefitting from their favorable optical properties including low waveguiding loss, strong evanescent fields, tight optical confinement, high power transmission, and excellent compatibility with standard optical fibers [2][3][4][5] , these MNFs have been extensively studied for applications ranging from optical couplers [6][7][8] , nonlinear optics [9][10][11][12] , optical sensors [13][14][15][16] , atom optics [17][18][19] , to fiber lasers 20,21 and opto-mechanics [22][23][24][25] . As the structural parameters (waist diameter, uniform length, and tapering profile) of an MNF are subject to different demands in various application scenarios 2,3,26 , a number of MNF fabrication and geometry control techniques have been developed [27][28][29][30][31][32] , and MNFs with ultrahigh qualities (e.g., ultra-low loss 33 , ultra-high-precision diameter control 30,31,34 ) have been realized.…”