Fig. 1. (a) Schematic of the on-chip Er³⁺-doped LN microdisk resonator integrated with Cr film electrodes. (b) The top view of the 200-µm-diameter Er³⁺-doped LN microdisk from the optical microscope. (c) The enlarged image of the rim of the Er³⁺-doped LN microdisk by a 100× microscope objective.

Fig. 2. (a) Schematic of the experimental setup for tunable Er³⁺-doped LN microdisk laser. (WG, waveform generator; CTL, C-band tunable laser; PL, pump laser; PC, polarization controller; PD, photodetector; Osc, oscilloscope; OSA, optical spectrum analyzer; VG, voltage generator; OF, optical fiber; EC, electric cable.) (b) The measured transmission spectrum for the wavelength of the Er³⁺-doped LN microdisk laser. (c) The experimental setup photographed by a cell phone.

Fig. 3. (a) Histogram showing the statistic results of 80 resonant modes in Er³⁺-doped LN microdisk. (b) The double Lorentzian fitting showing a mode splitting, indicating both intrinsic Q factors of 2.13 × 10⁶ as measured at λ = 1544 nm.

Fig. 4. Electro-optic modulation in Er³⁺-doped LN microdisk resonator. (a) Normalized transmission measured when −200 V, −150 V, −100 V, −50 V, 0 V, +50 V, +100 V, +150 V, and +200 V voltages were applied on the electrodes. (b) The linear fitting of resonance wavelength shift in the Er³⁺-doped LN microdisk resonator with the applied negative and positive voltages.

Fig. 5. (a) Spectrum of the Er³⁺-doped LN microdisk laser with the pump power at 18 mW. (b) Recorded lasing spectra of the microdisk with the increasing voltage applied on electrodes.