Fig. 1. Crystal structure, crystal photos, and optical properties of KBOB. (a) Crystal structure^[12]; (b) (c) crystal photographs grown using lead-containing flux system^[14,27]; (d) the transmission spectra of crystals grown by lead-containing and lead-free flux in the short-wave region^[27]; (e) experimental and fitted refractive index dispersion curve^[14]; (f) experimental and theoretical Maker fringes for nonlinear optical coefficient d₂₂^[14]

Fig. 2. The magneto-optical and electro-optical properties of KBOB crystal. (a) Experimental output voltage versus the applied current for Tb doped glass, KBOB, and Bi₄Ge₃O₁₂(BGO) crystals^[16]; (b) linear fitting between phase difference and applied electric field strength (inset shows the KBOB device for EO measurement)^[17]

Fig. 3. The 532 nm power as a function of 1064 nm pump power for KBOB crystal. (a) Nanosecond laser output power^[18]; (b) picosecond laser output power^[24]

Fig. 4. The 515 nm and 343 nm power as a function of 1030 nm pump power for KBOB crystal^[25]. (a) The output average power of 515 nm green laser with different repetition rates; (b) the output average power of 343 nm ultraviolet laser with different repetition rates

Fig. 5. The output results of 355 nm obtained based on KBOB crystal. (a) The output power and conversion efficiency of 355 nm fs laser as a function of 710 nm pump laser^[24]; (b) the output energy and conversion efficiency of SFG, the sum of energy should be total pump energy (the inset shows the beam profiles of the SFG by using 10 Hz repetition rate)^[21]; (c) SFG output power dependent with the input power at 1064 nm using different focus lenses^[21]; (d) stability of output power at 355 nm^[21]

Fig. 6. Broadband optical parametric chirped pulse amplification in KBOB crystal near 800 nm^[26]. (a) Schematic of the OPCPA experimental setup; (b) class Ⅰ phase matching gain bandwidth of crystals at a pump wavelength of 526.5 nm; (c) amplified energy and the conversion efficiency as a function of pump energy/pump intensity, the inset shows the near-field beam profile at the output of KBOB crystal; (d) the spectra before and after amplification