Fig. 1: Experimental setup and principle of operation.
From: Giant injection-locking bandwidth of a self-pulsing limit-cycle in an optomechanical cavity
a The main optical signals are derived from two external-cavity diode lasers (L1 and L2) and sent into a tapered microloop optical fiber to evanescently couple light into the silicon optomechanical crystal cavity (OMC). The optical signal decoupled from the OMC is collected by the same fiber and measured either in transmission or in reflection using an in-fiber circulator. The signals in both arms are band-pass filtered by 1 nm bandwidth wavelength filters (WF), impinging on two fast photodetectors (PDs). The electrical signals are sent to a spectrum analyzer (SA), a vector network analyzer (VNA) or an oscilloscope (OSC) for characterization. EOM stands for electro-optic modulator and FPC for fiber polarization controller. b Optical transmission spectrum, exhibiting two optical modes at λ1,o = 1531 nm and λ2,o = 1559 nm. Lasers L1 and L2 address the fundamental and first order modes respectively, L1 acting as the pump and L2 as the probe. c Self-pulsing (SP) limit-cycle represented in the phase space defined by the effective temperature increase of the cavity region (ΔT) and the free carrier concentration (N) d Time trace of the transmitted optical signal when SP is active. The positions highlighted by numbers 1–4 are associated to the different corners of the SP limit-cycle of panel c. e and f Power spectral density (PSD) spectra when the system is in a SP state and the modulation is on (Pmod = ±6.1%) at different modulation frequencies. In panel e the SP limit-cycle is not locked to the external modulation (fmod~33 MHz and υSP~43 MHz), while it is locked in panel f (fmod = υSP~41 MHz).
