Fig. 4: Thin nitride Q and loss measurements.
From: Anneal-free ultra-low loss silicon nitride integrated photonics
a The loss and intrinsic Q variation of the transverse magnetic (TM) mode vs. wavelength for three different devices. b Q measurement of the TM mode resonance in device 3 at 1550 nm that yields the lowest loss and highest Q of 1.77 dB m−1 and 14.9 million, respectively. The loaded Q and full-width max (FWHM) are 4.0 million and 49.1 MHz, respectively. c The setup for the laser to resonator Pound–Drever–Hall (PDH) locking and frequency noise measurements with an optical frequency discriminator; PD photodetector, BPD balanced photodetector, PC polarization controller, OSC oscilloscope. d Frequency noise measurements at 1550 nm of the laser free-running vs. when PDH locked to the ring resonator cavity. The 1/π-integral linewidth (1/π-ILW) and β -separation linewidth (β-SLW) of the laser were reduced by factors of 22 and 28, respectively, upon locking. The frequency noise was as low as 20 Hz2 Hz−1 at 10 kHz frequency offset from the carrier, then
