Optical Frequency Combs Generated in Silica Microspheres in the Telecommunication C-, U-, and E-Bands

Abstract

Optical frequency combs (OFCs) generated in microresonators with whispering gallery modes are demanded for different applications including telecommunications. Extending operating spectral ranges is an important problem for wavelength-division multiplexing systems based on microresonators. We demonstrate experimentally three spectrally separated OFCs in the C-, U-, and E-bands in silica microspheres which, in principle, can be used for telecommunication applications. For qualitative explanation of the OFC generation in the sidebands, we calculated gain coefficients and gain bandwidths for degenerate four-wave mixing (FWM) processes. We also attained a regime when the pump frequency was in the normal dispersion range and only two OFCs were generated. The first OFC was near the pump frequency and the second Raman-assisted OFC with a soliton-like spectrum was in the U-band. Numerical simulation based on the Lugiato–Lefever equation was performed to support this result and demonstrate that the Raman-assisted OFC may be a soliton.

Cascade Brillouin Lasing in a Tellurite-Glass Microsphere Resonator with Whispering Gallery Modes

“…The experiments with the considered microsphere were carried out according to the scheme shown in Figure 5. Like in our previous works [44,45,52,53], the study was conducted in an acrylic glove box to minimize the influence of dust, air currents, and other external factors. The WGM microsphere was excited by a tunable CW narrow-band telecom laser (Pure Photonics, 18 dBm, 10 kHz linewidth, and 190.3-197.9 THz tuning spectral range) controlled by a computer.…”

“…Laser radiation was coupled into the microsphere resonator through a silica taper with a diameter of ~3 μm. The taper was made by heating and stretching a standard telecom fiber as in [52,53]. Before the taper, a polarizing controller (PC) was used in the circuit.…”

Thermo-Optical Sensitivity of Whispering Gallery Modes in As2S3 Chalcogenide Glass Microresonators

“…The details are given in our previous article [20]. CW pump laser radiation was coupled into the microsphere through a fiber taper made of a commercially available silica telecommunication fiber by heating and stretching [16,27]. We used a commercially available tunable telecommunication C-band laser (Pure Photonics, PLCC550-180-60) with a linewidth of 10 kHz and adjustable power up to 18 dBm (63 mW) supporting the frequency sweeping mode.…”

Changes of the SNAP resonator shape owing to mode energy dissipation

“…The whispering gallery modes (WGM) microresonators have a small effective mode volume and a high Q factor, for example, for spherical microresonators, the maximum theoretically predicted quality factor is 𝑄 = 10 8 [1]. These advantages allow to easily employ nonlinear effects, for intantce, to generate optical frequency combs in spherical WGM microresonators [2].…”