Fig. 1. (a) 3D schematic diagram of a microcavity laser with a quarter deleted. (b) 2D simulated diagram of circular-sided square microcavity with a central hole. (c) Mode Q-factor versus mode wavelength. Insets are magnetic field (|Hz|) distributions for the 0th and 1st transverse modes. (d) |αm|2 of different angular quantum numbers m for the high Q-factor 0th mode. Husimi distribution map in a circular-sided square microcavity with an output waveguide for the (e) 0th and (f) 1st near-degenerate modes with the high Q-factor. Mode Q-factor and mode frequency interval Δf versus the change of refractive index Δn for (g) high-Q 0th mode and 1st mode, (h) two near-degenerate modes of the 0th mode, and (i) two near-degenerate modes of the 1st mode.

Fig. 2. (a) Output power coupled into an SMF and the applied voltage versus the CW injection current. (b) Lasing spectra map and (c) lasing mode wavelengths and mode intervals versus the CW injection current. Inset in (a): microscope image of a circular-sided square microlaser.

Fig. 3. (a) Test system for nonlinear dynamics. ISO, isolator; OSA, optical spectrum analyzer; EDFA, erbium-doped fiber amplifier; OBPF, optical bandpass filter; PD, photodetector; ESA, electrical spectrum analyzer; OSC, real-time oscilloscope. (b) Lasing spectra and RF spectra for longitudinal mode around (c) 1545 nm and (d) 1555 nm, at currents of 18, 20, and 22 mA. (e) Enlarged view of RF spectra in dotted box in (d).

Fig. 4. Temporal dynamics for irregular pulse packages of the longitudinal mode around 1555 nm for the microlaser at 20 mA.

Fig. 5. Dynamic routes into the chaotic state around 1555 nm for dual-transverse-mode self-chaotic microlaser: (a) P1 state at 23 mA, (b) P3 state at 24 mA, (c) P3 plus chaos at 25 mA, and (d) chaos at 26 mA. (a1)–(d1) Lasing spectra and (a2)–(d2) corresponding RF spectra.

Fig. 6. (a) Chaotic optical spectra with currents ranging from 27 to 35 mA. (b) RF spectrum, (c) temporal waveform, and (d) autocorrelation function of chaos signal at 29 mA by filtering the main longitudinal mode around 1556 nm. Inset in (d) is an ACF curve for 1000 ns.

Fig. 7. Relative intensity noise of the self-chaotic microlaser at 29 mA.

Fig. 8. (a) Full optical spectrum, and (b)–(d) RF spectrum at the current of 35 mA. RF spectra for (b) longitudinal mode around 1557 nm, (c) longitudinal mode around 1567 nm, and (d) all modes without optical filter.