Fig. 1. Epitaxial structure of gain chip and resonant cavity of SDL. (a) Schematic of epitaxial structure; (b) schematic and photograph of resonant cavity

Fig. 2. Cavity mode radius of fundamental frequency laser in resonator of laser and polarization states of fundamental frequency laser and frequency-doubled blue light in resonator. (a) Cavity mode radius of fundamental frequency laser ; (b) polarization state of fundamental frequency laser; (c) polarization state of frequency-doubled blue light

Fig. 3. Spectrum of blue light SDL, PL spectrum of gain chip, and spectrum of fundamental SDL

Fig. 4. Characteristics of SQS blue laser pulse train. (a) Temporal waveform of pulse train; (b) radio frequency spectrum of pulse train

Fig. 5. Output power curves of fundamental SDL and SQS blue light SDL

Fig. 6. Repetition rate of SQS pulses versus pump power

Fig. 7. Experimental setup of UWOC system

Fig. 8. Comparison of communication BER between SQS blue light and CW blue light at different data transmission rates. (a) In clear water; (b) in Maalox solution with mass concentration of 922.2 mg·m^-3

Fig. 9. Communication BERs for SQS blue light and CW blue light at different Maalox solution mass concentrations. (a) 10 Mbit/s data transmission rate; (b) 20 Mbit/s data transmission rate